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3/22/2016 - Adopted Board Records
AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 RESOLUTION 032216-1 SETTING THE ALLOCATION PERCENTAGE FOR PERSONAL PROPERTY TAX RELIEF IN ROANOKE COUNTY FOR THE 2016 TAX YEAR WHEREAS, in accordance with the requirements set forth in Section 58.1-3524 (C) (2) and Section 58.1-3912 (E) of the Code of Virginia, as amended by Chapter 1 of the Acts of Assembly and as set forth in item 503.E (Personal Property Tax Relief Program or "PPTRA") of Chapter 951 of the 2005 Acts of Assembly and qualifying vehicle with a taxable situs within the County commencing January 1, 2016, shall receive personal property tax relief; and WHEREAS, this Resolution is adopted pursuant to Ordinance 122005-10 adopted by the Board of Supervisors on December 20, 2005. NOW THEREFORE, BE IT RESOLVED, BY THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, as follows: 1. That tax relief shall be allocated so as to eliminate personal property taxation for qualifying personal use vehicles valued at $1,000 or less. 2. That qualifying personal use vehicles valued at $1,001-$20,000 will be eligible for 58.07% tax relief. 3. That qualifying personal use vehicles valued at $20,001 or more shall only receive 58.07% tax relief on the first $20,000 of value; and 4. That all other vehicles which do not meet the definition of qualifying (for example, including but not limited to, business use vehicles, farm use vehicles, motor homes, etc.) will not be eligible for any form of tax relief under this program. Page 1 of 2 5. That the percentages applied to the categories of qualifying personal use vehicles are estimated fully to use all available PPTRA funds allocated to Roanoke County by the Commonwealth of Virginia. 6. That this resolution shall be effective from and after the date of its adoption. On motion of Supervisor McNamara to adopt the resolution, seconded by Supervisor Peters and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None PY TESTE: Deborah C. Jacks I/ Chief Deputy Cler the Board of Supervisors cc: Rebecca Owens, Director of Finance Laurie Gearheart, Assistant Director of Finance Ruth Ellen Kuhnel, County Attorney Kevin Hutchins, Treasurer Nancy Horn, Commissioner of the Revenue Page 2 of 2 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 RESOLUTION 032216-2 ADOPTING REVISIONS TO THE STORMWATER MANAGEMENT DESIGN MANUAL FOR ROANOKE COUNTY WHEREAS, Section 23-1.8 of the Roanoke County Code provides for the adoption of a Stormwater Management Design Manual; and WHEREAS, Roanoke County will utilize the policies, criteria, and information contained in this design manual for the proper implementation and requirements of the stormwater management ordinance; and WHEREAS, this design manual shall be authorized and approved by the Board of Supervisors by resolution. NOW, THEREFORE BE IT RESOLVED, by the Board of Supervisors of Roanoke County, Virginia, as follows: 1. That the Stormwater Management Design Manual dated July 1, 2014 and approved by the Board of Supervisors by Resolution on May 13, 2014, is hereby repealed. 2. That the "Stormwater Management Design Manual" dated March 22, 2016 is hereby adopted in order to implement the requirements of Chapter 23. "Stormwater Management Ordinance", as provided in Section 23-1.8. 3. That this resolution shall be effective from and after March 22, 2016. Page 1 of 2 On motion of Supervisor Assaid to adopt the resolution, seconded by Supervisor Hooker and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None PY TE Dbborah C. Jac Chief Deputy CI r o the Board of Supervisors cc: Arnold Covey, Director of Community Development Tarek Moneir, Deputy Director of Development Page 2 of 2 COUNTY OF ROANOKE STORMWATER MANAGEMENT DESIGN MANUAL MARCH 22, 2016 March 22, 2016 Department of Community Development 5204 Bernard Drive Roanoke, Virginia 24018 TABLE OF CONTENTS COUNTY OF ROANOKE STORMWATER MANAGEMENT DESIGN MANUAL PREFACE Roanoke County's intent is to comply with the state Stormwater Management Law and Regulations, through implementation of the Roanoke County Stormwater Management Ordinance. All BMPs proposed for use in the County must be previously approved by DEQ and they must be contained on the VA BMP Clearinghouse. This Design Manual has local requirements that aid in the implementing of the state requirements and that supplement the state requirements. This March 22, 2016 edition of the Design Manual replaces the July 1, 2014 Design Manual, as approved by the Board of Supervisors by Resolution 032216-2 Due to the complexity of the subject, it is necessary for engineers and designers to be familiar with the information contained in all of the references listed in Section 1.8 of this manual. COUNTY OF ROANOKE 1 TABLE OF CONTENTS MARCH 22, 2016 TABLE OF CONTENTS Chapter 1 — Introduction 1.1 Manual Purpose.................................................................................................1-1 2-1 1.2 Water Programs Regulatory Background.......................................................1-1 2-1 2.3 1.2.1 Erosion and Sediment Control Program .................................................. 1-2 2.4 1.2.2 Stormwater Management Program.......................................................... 1-2 2.5 1.2.3 Floodplain Management Program............................................................ 1-2 2.6 1.2.4 Illicit Discharge Detection and Elimination Program .............................. 1-2 1.2.5 Municipal Separate Storm Sewer System (MS4) Permit ......................... 1-2 1.3 Contents of the Manual.....................................................................................1-3 1.4 Authority.............................................................................................................1-4 1.5 Applicability.......................................................................................................1-4 1.6 Administration...................................................................................................1-4 1.6.1 General..................................................................................................... 1-4 1.6.2 Manual Amendments............................................................................... 1-5 1.6.3 Exceptions................................................................................................1-5 1.6.4 Appeal of Decisions................................................................................. 1-5 1.7 Approval and Permits........................................................................................1-5 1.7.1 Local Approvals and Permits................................................................... 1-5 1.7.2 Water and Sewer Approvals and Permits ................................................ 1-5 1.7.3 Joint Permit Application.......................................................................... 1-6 1.8 Reference Sources..............................................................................................1-6 1.8.1 County of Roanoke Code and Ordinances ............................................... 1-6 1.8.2 Virginia Law and Regulations................................................................. 1-7 1.8.3 Virginia Manuals, Handbooks and Websites ........................................... 1-7 1.9 Acronyms and Abbreviations...........................................................................1-7 Appendix 1A — Roanoke County Policy on Common Plan of Development or Sale Chapter 2 Stormwater Management Plan Review and Approval 2.1 Overview of the Review and Approval Process .............................................. 2-1 2.2 Concept Stormwater Management Plan Submittal ........................................ 2-1 2.3 Stormwater Management Master Plan Submittal .......................................... 2-1 2.4 Stormwater Management Plan Submittal....................................................... 2-1 2.5 Submittal of Stormwater Calculations............................................................. 2-2 2.6 Changes and Modifications to an Approved Plan .......................................... 2-3 Chapter 3 Easements 3.1 General................................................................................................................3-1 3.2 Drainage Easements........................................................................................... 3-1 3.2.1 Culverts and Storm Drains....................................................................... 3-2 3.2.2 Open Channels......................................................................................... 3-3 3.3 Access Easements............................................................................................... 3-4 3.4 Maintenance of Easements................................................................................ 3-4 COUNTY OF ROANOKE 11 TABLE OF CONTENTS MARCH 22, 2016 TABLE OF CONTENTS Appendix 3A — Standard Easement Agreements Chapter 4 Stormwater Hydrology 4.1 References........................................................................................................... 4-1 4.2 Design Frequencies............................................................................................ 4-1 4.2.1 General.....................................................................................................4-1 5-1 4.2.2 Storm Drainage Systems..........................................................................4-1 5-1 4.2.3 Stormwater Management Facilities......................................................... 4-2 4.3 Time of Concentration (tc) and Travel Time(Tt)............................................ 4-2 4.3.1 General.....................................................................................................4-2 5-2 4.3.2 Overland Flow......................................................................................... 4-2 4.3.3 Shallow Concentrated Flow..................................................................... 4-3 4.3.4 Channelized Flow.................................................................................... 4-3 4.3.5 Pipe Flow................................................................................................. 4-3 4.4 Selection of Methodologies................................................................................ 4-3 4.4.1 General.....................................................................................................4-3 5-7 5.3 4.4.2 Peak Discharge Methods for Design of Storm Drainage Systems .......... 4-4 5.5 4.4.3 Hydrograph Methods for Design of Stormwater Management Facilities 4-4 4.5 Methodologies.....................................................................................................4-4 5-8 4.5.1 Rational Method....................................................................................... 4-4 4.5.2 Modified Rational Method....................................................................... 4-6 4.5.3 SCS Method............................................................................................. 4-7 Appendix 4A — Design Aids, From Chapter 6, VDOT Drainage Manual Appendix 4B — Design Aids, From Chapter 4, VA SWM Handbook Appendix 4C — Information from VDOT Hydraulic Design Advisories Chapter 5 Open Channels 5.1 References........................................................................................................... 5-1 5.2 Design Methodology and Criteria.................................................................... 5-1 5.2.1 Major and Minor Channels...................................................................... 5-1 5.2.2 Design Flow............................................................................................. 5-1 5.2.3 Hydrology................................................................................................ 5-1 5.2.4 Channel Hydraulics.................................................................................. 5-2 5.2.5 Channel Velocity..................................................................................... 5-2 5.2.6 Channel Slope.......................................................................................... 5-3 5.2.7 Cross Sectional Area................................................................................ 5-4 5.2.8 Channel Lining......................................................................................... 5-5 5.2.9 Freeboard Requirements.......................................................................... 5-6 5.2.10 Calculation of Depth of Flow at Bends and Curves ................................ 5-7 5.2.11 Channel Location and Width Restrictions on Residential Lots ............... 5-7 5.3 Environmental Considerations and Fishery Protection ................................. 5-8 5.5 Maintenance Requirements.............................................................................. 5-8 5.6 Floodplain Studies.............................................................................................. 5-8 COUNTY OF ROANOKE 111 TABLE OF CONTENTS MARCH 22, 2016 TABLE OF CONTENTS Appendix 5A — Aids for Open Channel Design, From Chapter 7, VDOT Drainage Manual Chapter 6 Culverts 6.1 References...........................................................................................................6-1 6.2 Design Methodology and Criteria.................................................................... 6-2 6.2.1 Computation Methods.............................................................................. 6-2 6.2.2 Hydrology................................................................................................ 6-2 6.2.3 Culvert Hydraulics................................................................................... 6-2 6.2.4 Structural Design..................................................................................... 6-5 6.2.5 Materials.................................................................................................. 6-6 6.2.6 Culvert Sizes............................................................................................ 6-7 6.2.7 End Conditions......................................................................................... 6-7 6.2.8 Multiple Barrel Culverts.......................................................................... 6-8 6.2.9 Culvert Skew............................................................................................ 6-8 6.2.10 Buoyancy................................................................................................. 6-8 7.3 6.2.11 Debris and Trash Racks........................................................................... 6-9 6.3 Installation.......................................................................................................... 6-9 7-11 6.3.1 Bedding Material..................................................................................... 6-9 6.3.2 Backfill.....................................................................................................6-9 7.3.3 Separation of Utilities............................................................................ 6.4 Environmental Considerations and Fishery Protection ................................. 6-9 6.5 Maintenance Requirements............................................................................ 6-10 Appendix 6A — Aids for Stormwater Culvert Design, From Chapter 8, VDOT Drainage Manual Chapter 7 Storm Drains 7.1 References........................................................................................................... 7-1 7.2 Design Methodology and Criteria.................................................................... 7-1 7.2.1 Computation Methods.............................................................................. 7-1 7.2.2 Hydrology................................................................................................ 7-2 7.2.3 Design Flows........................................................................................... 7-2 7.2.4 Measures to Convey Stormwater Runoff to Inlets ................................... 7-2 7.2.5 Storm Drain Inlets.................................................................................... 7-3 7.2.6 Storm Drain Pipes.................................................................................... 7-5 7.2.7 Determination of Hydraulic Grade Line .................................................. 7-7 7.2.8 100 -Year Conditions.............................................................................. 7-10 7.2.9 Materials................................................................................................ 7-10 7.2.10 Structural Design................................................................................... 7-10 7.3 Installation........................................................................................................ 7-10 7.3.1 Bedding Material................................................................................... 7-11 7.3.2 Backfill...................................................................................................7-11 7.3.3 Separation of Utilities............................................................................ 7-11 7.4 Environmental Impacts...................................................................................7-11 COUNTY OF ROANOKE iv TABLE OF CONTENTS MARCH 22, 2016 TABLE OF CONTENTS 7.5 Erosion Protection at Outfalls........................................................................ 7-11 7.6 Maintenance Requirements............................................................................ 7-11 Appendix 7A — Aids for Storm Drain System Design, From Chapter 9, VDOT Drainage Manual Appendix 7B — Installation Procedures Chapter 8 Residential Lot Drainage 8.1 References........................................................................................................... 8-1 8.2 General Lot Grading......................................................................................... 8-1 8.3 Construction Plan Requirments....................................................................... 8-1 Chapter 9 Stormwater Detention 9.1 References........................................................................................................... 9-2 9.2 Design Methodology and Criteria.................................................................... 9-2 9.3 Environmental Impacts..................................................................................... 9-8 9.4 Maintenance Requirements........................................................................... 9-8 Chapter 10 Energy Dissipation 10.1 References.........................................................................................................10-1 10.2 Design Methodology and Criteria..................................................................10-2 10.2.1 Outlet Velocity....................................................................................... 10-2 10.2.2 Erosion Control Stone............................................................................ 10-2 10.2.3 Riprap Outlet Basins.............................................................................. 10-2 10.2.4 Baffled Outlets....................................................................................... 10-3 10.2.5 Energy Dissipator for Paved Areas ........................................................ 10-4 10.2.6 Additional Energy Dissipators............................................................... 10-4 10.3 Installation Requirements...............................................................................10-5 10.4 Easements.........................................................................................................10-5 10.5 Environmental Impacts...................................................................................10-5 10.6 Maintenance Requirements............................................................................10-5 Appendix 10A — Aids for Energy Dissipation Design, From VDOT Drainage Manual Appendix 10B — Aids for Energy Dissipation Design, From VDOT Road and Bridge Standards Appendix 10C — Energy Dissipation Design Schematics Chapter 11 (RESERVED) Chapter 12 Environmentally Sensitive Areas 12.1 References......................................................................................................... 12-1 12.2 Floodplains........................................................................................................12-2 12.2.1 Applicant Flood Study Requirements.................................................... 12-3 COUNTY OF ROANOKE v TABLE OF CONTENTS MARCH 22, 2016 TABLE OF CONTENTS Chapter 13 Geotechnical Studies (RESERVED) Chapter 14 Maintenance of Stormwater Management Facilities 14.1 12.2.2 Floodplain Delineation........................................................................... 12-5 12.3 Steep Slopes......................................................................................................12-5 15-1 14.3 12.3.1 Development Restrictions...................................................................... 12-5 14.4 12.3.2 Design Standards................................................................................... 12-5 12.4 Stream Buffers................................................................................................. 12-6 12.5 Critical Erosion Areas.....................................................................................12-6 14-5 12.6 Karst Geology...................................................................................................12-7 12.7 Stormwater Hot Spots.....................................................................................12-8 15-4 12.7.1 Design Restrictions................................................................................ 12-9 12.7.2 Golf Course Development..................................................................... 12-9 Appendix 12A — Design Aids, From Local Assistance Manual, Chesapeake Bay Local Assistance Department Chapter 13 Geotechnical Studies (RESERVED) Chapter 14 Maintenance of Stormwater Management Facilities 14.1 Responsibility for Maintenance......................................................................14-1 14.2 Maintenance Agreements................................................................................14-1 15-1 14.3 Maintenance Program..................................................................................... 14-2 14.4 Additional Maintenance and Repair..............................................................14-5 15-2 14.5 Inspection and Maintenance Records............................................................14-5 14.6 References......................................................................................................... 14-5 Appendix 14A — Maintenance Agreements Appendix 14B — Maintaining Stormwater Systems, A Guidebook for Private Owners and Operators in Northern Virginia Chapter 15 Inspection and Enforcement 15.1 Construction Inspections.................................................................................15-1 15. 1.1 Notifications to the County of Roanoke ................................................ 15-1 15.1.2 Periodic Inspections............................................................................... 15-2 15.1.3 Final Inspection and As -Built Documentation ...................................... 15-2 15.2 Post -Construction Inspections and Maintenance.........................................15-3 15.3 Records..............................................................................................................15-4 15.4 Enforcement.....................................................................................................15-4 15.4.1 Notice of Violation................................................................................ 15-4 15.4.2 Stop Work Orders.................................................................................. 15-5 15.4.3 Restoration of Land................................................................................ 15-5 Appendix 15A — Inspection Forms COUNTY OF ROANOKE vi TABLE OF CONTENTS MARCH 22, 2016 Chapter 1 - Introduction 1.1 Manual Purpose As land is developed and woodlands and pastures are converted to more intensive commercial and residential uses, the increase in impervious surfaces (pavements, buildings, etc.) and managed turf, cause adverse effects including: • Increased flooding • Increased erosion and deposition of sediment in streams • Less base flow in streams due to less groundwater recharge • Increased runoff of pollutants (nutrients, sediment, bacteria, oil) • Decreased stream biodiversity (e.g.,aquatic insects and fish) • Loss of recreational uses such as swimming and fishing The County of Roanoke stormwater management goals are to minimize these adverse effects of land development by implementing effective stormwater management Best Management Practices (BMPs) as required by the County Code for new and redevelopment, and over time, by providing BMP measures to mitigate the adverse effects of past land development activities. The County of Roanoke Stormwater Management Design Manual, hereafter called the Design Manual, contains local requirements that supplement local ordinances, state regulations and guidance, and federal regulations. In general, direction and guidance from these sources is not repeated in this Design Manual. Refer to the listing of Reference Sources at the end of this chapter. 1.2 Water Programs Regulatory Background The County of Roanoke implements, and is regulated by, several water programs as briefly described below. Land Disturbing Activities are regulated under the erosion and sediment control, stormwater management, and floodplain management programs. Existing Development is regulated by the illicit discharge detection and elimination program and, if the property contains a permanent BMP, by the stormwater management program. The County of Roanoke itself is regulated by the MS4 Permit program. While the MS4 permit only directly regulates the County, it may indirectly impact anyone living in, owning property, or developing in the County of Roanoke through the impact of County actions that are required by its permit. COUNTY OF ROANOKE MARCH 22, 2016 1-1 INTRODUCTION 1.2.1 Erosion and Sediment Control Program The County is the local Erosion and Sediment Control (E&SC) authority. E&SC requirements are contained in the County of Roanoke Erosion and Sediment Control Ordinance and Virginia Erosion and Sediment Control Regulations. The County administers the program under the oversight of the Virginia Department of Environmental Quality (DEQ). 1.2.2 Stormwater Management Program The County is the local Virginia Stormwater Management Program (VSMP) authority. VSMP requirements are contained in the County of Roanoke Stormwater Management Ordinance and Virginia Stormwater Management Regulations. The County administers the program with oversight of the DEQ. The proper understanding of the meaning of "common plan of development or sale" is critical to understanding the applicability of stormwater management requirements for land disturbing activities. The County's policy concerning common plan of development or sale is contained in Appendix IA. 1.2.3 Floodplain Management Program The County regulates development in the floodplain through its Zoning Ordinance. This Program was developed and is administered to comply with Federal Emergency Management Agency requirements. 1.2.4 Illicit Discharge Detection and Elimination Program Except for specific limited exceptions, only uncontaminated stormwater may be discharged into stormwater systems. The County operates an Illicit Discharge Detection and Elimination Program in accordance with the County of Roanoke Illicit Discharge Ordinance, as required by its MS4 Permit. The DEQ provides oversight of this program. 1.2.5 Municipal Separate Storm Sewer System (MS4) Permit The County of Roanoke is regulated under a General Permit for Small Municipal Separate Storm Sewer Systems issued by the DEQ. MS4 permits generally impact urban areas and they require the locality to implement specific Minimum Control Measures (MCM) to protect local water quality. These MCM's generally fall into six (6) categories: 1. Public Education and Outreach on Stormwater Impacts 2. Public Involvement and Participation 3. Illicit Discharge Detection and Elimination 4. Construction Site Stormwater Runoff Control 5. Post Construction Stormwater Management COUNTY OF ROANOKE MARCH 22, 2016 1-2 INTRODUCTION 6. Pollution Prevention and Good Housekeeping for Municipal Operations The MS4 Permit also requires that the locality address water impairments that are identified by a Total Maximum Daily Load (TMDL) Study where the locality has been given a Waste Load Allocation (WLA). The County of Roanoke has WLA's for a number of its streams for impairments caused by sediment, bacteria, and PCBs. See the Roanoke County website, Department of Community Development, Stormwater Management page for more information concerning the MS4 Permit and TMDLs. 1.3 Contents of the Manual The Design Manual is divided into 15 chapters. An overview of each chapter is presented below. Chapter 1 — Introduction. Chapter 1 presents the general background and purpose behind the Design Manual. The chapter documents the goals of the program, the applicable requirements for stormwater management, and the administration of the program. Chapter 2 — Stormwater Management Plan Review and Approval. Chapter 2 presents the process that the applicant and the County of Roanoke follow to assure that the requirements of the stormwater management program and the Stormwater Management Ordinance are met. Chapter 3 — Easements. Chapter 3 establishes the requirements for easements for BMPs and storm drainage systems. Chapter 4 — Stormwater Hydrology. Chapter 4 documents the hydrologic design practices used to establish design flows necessary to design storm drainage systems and BMPs. Chapter 5 — Open Channels. Chapter 5 presents the requirements for open channel hydraulics, including cross section requirements, side slopes, widths, slopes, channel linings, and calculation methods. Chapter 6 — Culverts. Chapter 6 presents the requirements for culverts, including materials, slopes, headwater and tailwater limitations, and design calculation methods. Chapter 7 — Storm Drains. Chapter 7 presents the requirements for storm drains, including storm drain piping sizes, and lengths, and storm drain inlet hydraulics. Chapter 8 — Residential Lot Drainage. Chapter 8 presents the requirements for residential lot drainage by providing drainage and/or grading the land to direct surface drainage away from building and toward streets, drainage conveyance structures, or sheet flow. COUNTY OF ROANOKE MARCH 22, 2016 1-3 INTRODUCTION Chapter 9 — Stormwater Detention. Chapter 9 presents requirements and design criteria for stormwater storage facilities. Design criteria include location, sizing, requirements, site access, release rates, and spillway requirements. Chapter 10 — Energy Dissipation. Chapter 10 includes the requirements for velocity and energy reduction devices at the discharge from storm drains, culverts, open channels, and other stormwater management systems. Energy dissipation is required to prevent excessive velocities and erosion in downstream channels. Chapter 11 — RESERVED. Chapter 12 — Environmentally Sensitive Areas. Chapter 12 presents requirements for development of environmentally sensitive areas including floodplains, stream buffers, steep slopes, erodible soils, and stormwater pollutant hot spots. Chapter 13 — Geotechnical Studies. (RESERVED) Chapter 14 — Maintenance of Stormwater Management Facilities. Chapter 14 presents the requirements for establishing a maintenance program for stormwater management facilities, and the establishment of a maintenance agreement to assure that stormwater management facilities are properly maintained. Chapter 15 — Inspection and Enforcement. Chapter 15 presents the inspection and enforcement procedures to ensure that construction of stormwater management facilities comply with the approved plans and are properly maintained post -construction. As -built requirements are also addressed in this chapter. 1.4 Authority The Design Manual provides supplemental information to implement the provisions of the County Code as they pertain to stormwater management, including storm drainage, and land development. In the event that any part of this Design Manual is held to be illegal or void, this shall not have the effect of making illegal or void the Design Manual in its entirety, or any section thereof, which shall remain effective. 1.5 Applicability The requirements of this Design Manual apply to all land disturbance activities requiring permits. Portions of this Design Manual apply to maintenance and repair of stormwater management facilities and other best management practices after construction is completed. COUNTY OF ROANOKE MARCH 22, 2016 1-4 INTRODUCTION 1.6 Administration 1.6.1 General The policies and procedures contained within this Design Manual shall be administered by the County of Roanoke, Director of Community Development (Director), or designee. 1.6.2 Manual Amendments This Design Manual may be periodically amended, as recommended by the Director of Community Development, or designee, and approved by the Board of Supervisors. Amendments to this Design Manual will be posted on the County website, and will become effective on the date listed on the website. It is the manual user's responsibility to check the website and verify that they have the latest requirements. 1.6.3 Exceptions Requests for exceptions of any provisions of this Design Manual shall be made in writing to the County of Roanoke, Director of Community Development. The exception request shall clearly identify the Design Manual provision that is desired to be modified; the justification to support the issuance of an exception, and the alternative measures that are proposed to meet the intent of the Design Manual. All requests for an exception will receive a written response outlining the reasons for approval, or denial, after receipt of all information requested by the Director. In reviewing the request, the Director shall closely examine the proposed development and evaluate the variance request based on the conditions set forth in the Design Manual, County of Roanoke Code, Stormwater Management Ordinance; and the requirements and recommendations of the VA SWM Handbook, VDOT Drainage Manual, VA BMP Clearinghouse, and other sources. 1.6.4 Appeal of Decisions Appeals of decisions may be filed in accordance with the procedures provided in the County of Roanoke Code, Stormwater Management Ordinance. 1.7 Approvals and Permits The applicant is responsible for acquiring all required approvals and permits. 1.7.1 Local Approvals and Permits The review and approval of stormwater management plans shall be an integral part of the overall review of site plans. Local permits and approvals include Erosion and COUNTY OF ROANOKE MARCH 22, 2016 1-5 INTRODUCTION Sediment Control Approval, Virginia Stormwater Management Program Permit, Land Disturbance Permit, Zoning Permit, and Building Permit. Retaining walls with a height of 3' or greater require a building permit. 1.7.2 Water and Sewer Approvals and Permits Public water and sewer requires approval from either the Western Virginia Water Authority (WVWA) or the Town of Vinton, depending on the geographic location. If the site is located in the Town of Vinton or to the east of the Town of Vinton, within the Town of Vinton service area; then, Town of Vinton approval is required. If public water and/or sewer is located elsewhere in the County; then, WVWA approval is required. For areas not served by public water and sewer, local health department approval is required for wells and onsite sanitary sewage disposal. 1.7.3. Joint Permit Application Wetlands and streams are protected under several Federal and State programs. Whenever jurisdictional wetlands or streams are impacted by land disturbing activities, a Joint Permit Application must be completed and filed with the Virginia Marine Resources Commission (VMRC). VMRC will distribute the joint permit application to The U.S. Army Corps of Engineers (USACE) and the Virginia Department of Environmental Quality (DEQ). The USACE and DEQ will consult with other Federal and State agencies in processing the permit application. Upon receipt of an acceptable application the following permits may be issued: • USACE Federal Section 404 Permit • DEQ Water Protection Permit (VWP) • VMRC Permit The Design Professional shall provide the County of Roanoke a copy of the required wetland permit; or with written documentation that a wetland permit is not required by the USACE, DEQ, or VRML. The written documentation shall be prepared by a 3rd party professional experienced in wetland delineation. Plans shall show the surveyed wetland boundary delineation, provide geographic location of the wetland flags, provide acreage of wetlands, and linear footage of streams. Wetlands shall be numbered and flagged in the field. Wetland delineations shall be performed in accordance with the 1987 Corps of Engineers Wetland Delineation Manual and the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Eastern Mountains and Piedmont Region. COUNTY OF ROANOKE MARCH 22, 2016 1-6 INTRODUCTION 1.8 Reference Sources Managing stormwater runoff from land disturbing activities and prior developed land is a complex issue. There are a number of laws, ordinances and guidance sources that those that design land disturbance activities (land development) must follow. The requirements and recommendations of the following sources, latest editions, are incorporated into this Design Manual by reference. All of the referenced sources are readily available on the internet. 1.8.1 County of Roanoke Code and Ordinances Design and construction of land disturbing activities shall comply with all relevant portions of the County of Roanoke Code including: • Stormwater Management Ordinance • Erosion and Sediment Control Ordinance • Illicit Discharge Ordinance • Zoning Ordinance • Subdivision Ordinance 1.8.2 Virginia Law and Regulations Design and construction of land disturbing activities shall comply with all relevant Virginia law and regulations including: • Virginia Stormwater Management Law • Virginia Erosion and Sediment Control Law • Virginia Stormwater Management Regulations • Virginia Erosion and Sediment Control Regulations 1.8.3 Virginia Manuals, Handbooks, and Websites • Virginia Stormwater Management Handbook, Hereafter throughout this Design Manual referred to as the VA SWM Handbook. • Virginia Department of Transportation Drainage Manual. Hereafter throughout this Design Manual referred to as the VDOT Drainage Manual. COUNTY OF ROANOKE MARCH 22, 2016 1-7 INTRODUCTION • Virginia Department of Transportation Road and Bridge Standards. Hereafter throughout this Design Manual referred to as the VDOT Standards. • Virginia Department of Transportation Road and Bridge Specifications. Hereafter throughout this Design Manual referred to as the VDOT Specifications. • Virginia Erosion and Sediment Control Handbook. Hereafter throughout this Design Manual referred to as the VA E&SC Handbook. • Virginia Stormwater Management BMP Clearinghouse website (htlp://vwrrc.vt.edu/swc/). Hereafter throughout this Design Manual referred to as the BMP Clearinghouse. 1.9 Acronyms and Abbreviations For clarification, the following is a listing of abbreviations, and acronyms used in stormwater management and throughout this Design Manual. A — Drainage area, acres (stormwater hydrology) A — Cross section area, square feet (open channel or pipe hydraulics) B — VDOT rainfall coefficient, no units (stormwater hydrology) BMP — Best management practice C — Runoff coefficient, no units (stormwater hydrology) Cf— Saturation factor, no units (stormwater hydrology) CMP — Corrugated metal pipe CN — Curve Number (stormwater hydrology) USACE — U.S. Army Corps of Engineers D — VDOT rainfall coefficient, no units (stormwater hydrology) DCR — Virginia Department of Conservation and Recreation De — Critical duration, minutes (stormwater hydrology) DEQ — Virginia Department of Environmental Quality E — VDOT rainfall coefficient, no units (stormwater hydrology) FEMA — Federal Emergency Management Agency g — Gravity coefficient, 32.2 feet/s2 H — Height or depth of water, feet Hf, Hi, Hm, Ho, Ho — Head losses in piping and structures, feet (storm drain hydraulics) HDPE — High density polyethylene HGL — Hydraulic grade line I — Rainfall intensity, inches per hour (stormwater hydrology) Ipost — Post -development impervious cover, percentage (water quality Simple Method calculation) Iexisting — Existing impervious cover, percentage (water quality Simple Method calculation) K, Ki, Ko — Head loss coefficients for piping, no units Lpre — Pre -development pollutant loading, pounds per year (water quality Simple Method calculation) COUNTY OF ROANOKE MARCH 22, 2016 1-8 INTRODUCTION Lpost — Post -development pollutant loading, pounds per year (water quality Simple Method calculation) MS4 — Municipal Separate Storm Sewer System n — Manning's equation roughness coefficient, no units (open channel and pipe hydraulics) NFIP — National Flood Insurance Program Q — Stormwater flow, cubic feet per second (cfs) R — Hydraulic radius, feet (open channel hydraulics) r, — Stream bend radius, center, feet (open channel hydraulics) ri - Stream bend radius, inside bank, feet (open channel hydraulics) ro — Stream bend radius, outside bank, feet (open channel hydraulics) S — Slope, feet per feet (open channel or pipe hydraulics) or as a percentage (%) SCS — Soil Conservation Service t, — Time of concentration, minutes (stormwater hydrology) Tp — Time to peak flow, minutes (stormwater hydrology) Tr — Time to recede, minutes (stormwater hydrology) Tt — Travel time, minutes (stormwater hydrology) V, Vi, Vo — Velocity, feet per second (open channel and pipe hydraulics) VA E&SC Handbook — Virginia Erosion and Sediment Control Handbook, latest version, as amended VA SWM Handbook — Virginia Stormwater Management Handbook, latest version, as amended VDOT — Virginia Department of Transportation VDOT Drainage Manual — Virginia Department of Transportation, Drainage Manual, latest version, as amended VDOT Specifications — Virginia Department of Transportation, Road and Bridge Specifications, latest version, as amended VDOT Standards — Virginia Department of Transportation, Road and Bridge Standards, latest version, as amended VMRC — Virginia Marine Resources Commission VSMP — Virginia Stormwater Management Program, as administered by DEQ and Roanoke County AZ = Difference in water surface elevation from the inside curve to the outside cuive of an open channel, feet (open channel hydraulics) COUNTY OF ROANOKE MARCH 22, 2016 1-9 INTRODUCTION APPENDIX IA POLICY CONCERNING COMMON PLAN OF DEVELOPMENT OR SALE COUNTY OF ROANOKE MARCH 22, 2016 IA -1 INTRODUCTION Policy Concerning "Common Plan of Development or Sale" 1A.1 General This policy explains how Roanoke County interprets and will apply "common plan of development or sale" in its local VSMP. In the event that this policy conflicts with any guidance issued by DEQ, DEQ guidance will govern. All land -disturbing activities, except those specifically exempted in Section 23-1.3 of the Roanoke County Stormwater Management Ordinance, require approval from Roanoke County as the local VSMP authority and coverage under the state General Permit for Discharges of Stormwater from Construction Activities prior to commencing land -disturbing activities. Several exemptions apply to land -disturbing activities that disturb less than one acre of land and that are not part of a larger common plan of development or sale. In order to properly apply these exemptions, it is necessary to understand what is meant by "common plan of development or sale." It is critical for developers and land -owners to understand that the permitting exemption can be lost by disturbing more area on a project than planned (exceeding 1 acre land - disturbance) or by taking actions that demonstrate that a small project (less than 1 acre land -disturbance) is part of a larger common plan of development or sale. Actions that increase land disturbance or that create a larger common plan of development after plan approval and during construction will necessitate securing a VSMP permit, may result in possible enforcement and penalty actions, and may result in additional costs and delays due to the need to redesign the site and construct or modify BMPs. Land disturbing activities that are exempt from the requirements of the Stormwater Management Ordinance may not be exempt from the Erosion and Sediment Control stormwater management requirements. Erosion and Sediment Control regulations could still require stormwater management to address Minimum Standard 19. 1A.2 State Definition and Guidance 9VAC25-870-10 defines common plan of development or sale in the following manner: "Common plan of development or sale " means a contiguous area where separate and distinct construction activities may be taking place at different times on different schedules. For the purposes of the VSMP regulations, individual lots within existing residential, commercial, or industrial site plans and subdivision plans that were platted prior to July 1, 2004 may be considered separate land -disturbing activities. COUNTY OF ROANOKE MARCH 22, 2016 INTRODUCTION IA -2 1A.3 Discussion and Application 1A.3.1 USEPA guidance (http://cfpub.epa.gov/npdes/fags.cfm?program_id=6 ) A "larger common plan of development or sale" is a contiguous area where multiple separate and distinct construction activities may be taking place at different times on different schedules under one plan. For example, if a developer buys a 20 -acre lot and builds roads, installs pipes, and runs electricity with the intention of constructing homes or other structures sometime in the future, this would be considered a larger common plan of development or sale. If the land is parceled off or sold, and construction occurs on plots that are less than one acre by separate, independent builders, this activity still would be subject to stormwater permitting requirements if the smaller plots were included on the original site plan. The larger common plan of development or sale also applies to other types of land development such as industrial parks or well fields. A permit is required if one (1) or more acres of land will be disturbed, regardless of the size of any of the individually -owned or developed sites. 1A.3.2 The creation of a common plan of development or sale A common plan of development or sale comes into being when there is documentation showing plans or intent to disturb earth regardless of how many phases or how long it will take. Common documents that create a common plan of development include: (a) any announcement or documentation (marketing plans, sign, sales pitch, notice, etc.); (b) any physical demarcation (boundary signs, lot stakes) indicating construction may occur on a specific plot; (c) subdivision plats; or, (d) construction drawings. 1A.3.3 The completion of a common plan of development or sale Once a common plan of development or sale has been created, it remains in force until the contemplated development is substantially completed (less than one (1) acre remaining to be developed). There may be a time when a new developer will want to perform a land disturbing activity on an undeveloped parcel (that was created on or after July 1, 2004), and wants to know if a common plan of development or sale is still valid. In order for the new activity to not be a part of the original common plan of development or sale, it must meet 2 tests. Test 1: Was the original plan, including modifications, ever substantially completed with less than one (1) acre of the original common plan of development or sale remaining (e.g., less than one (1) acre remains to build out)? Test 2: Has there been a clearly identifiable period of time where there is no on- going construction, including meeting criteria for final stabilization? (Roanoke County, by this policy, sets the clearly identifiable period of time at one (1) year.) If the project meets the two tests, then it may be evaluated for permitting purposes on its individual merits. If it does not meet either of the two tests, then it remains part of the original common plan of development or sale, and it requires permit coverage. COUNTY OF ROANOKE MARCH 22, 2016 IA -3 INTRODUCTION 1A.3.4 Additional development on an individual parcel after the intended construction is completed When the intended construction on a parcel that is part of a larger common plan of development or sale is completed, any subsequent development or redevelopment of that parcel is considered a new plan of development. 1A.3.5 Effect of adding property to an existing project There are 2 cases where adding land to a project could have permitting impacts. Case 1: A common plan of development or sale has already been created and development of the common plan of development or sale is ongoing. The developer purchases additional property to incorporate into the development. The additional property would become part of the common plan of development or sale. Case 2: A developer subdivides a parcel to create a residential lot. The development of the lot will disturb less than 1 acre. No stormwater permit is required. Prior to a clearly identifiable period of time (1 year) where there is no on-going construction on the first lot, the developer creates a second lot from the original parcel (or markets additional homes prior to creating lots). The development of the second lot would disturb less than 1 acre; however, the development of the first lot and the second lot together would cumulatively disturb 1 acre or more. A larger common plan of development or sale has been created. A permit is required to cover the entire common plan of development or sale (both the construction on Lot 1 as well as Lot 2 and any subsequent lots). Construction on Lot 1 would need to halt until permitting is completed. Stormwater management requirements would need to be met for the entire common plan of development or sale. 1A.3.6 Timing for construction and ownership of BMPs for a common plan of development or sale The technical criteria for stormwater management must be applied to the entire common plan of development or sale. In some cases, portions of a common plan of development or sale may have BMPs with a higher efficiency of pollutant removal or stormwater volume or rate control than other portions of the common plan of development or sale. However, no portion of the common plan of development or sale shall be considered by the County to be completed or be allowed to be occupied until BMPs are completed and functioning that provide stormwater management for that portion of the common plan of development or sale adequate to meet minimum standards (e.g., the construction of BMPs cannot be deferred to a later phase, if the portion of the common plan of development or sale that is currently under construction does not have adequate BMPs to meet the stormwater management technical criteria). COUNTY OF ROANOKE MARCH 22, 2016 IA -4 INTRODUCTION BMPs that provide stormwater management for one individual parcel may be on the individual parcel and may be owned and maintained by the property owner of the individual parcel. At the developer's option, BMPs that provide stormwater management for one individual parcel may be made a property association's responsibility as described in the next paragraph. BMPs that provide stormwater management for more than one parcel must be owned and maintained by a property association, consisting of all property owners that are benefiting from the BMP. 1A.3.7 De minimus land disturbance Neither federal nor state definitions or guidance address de minimus land disturbance on a lot within a larger common plan of development or sale. It is obvious that at some point, minor land disturbing activities should not be regulated, within a larger common plan of development or sale; example — disturbance of 20 square feet, on a lot, to erect a temporary sign. For the purpose of implementing the VSMP, Roanoke County considers land disturbance of less than 2,500 square feet to be de minimus and will not fall under the VSMP regulations. If any additional land disturbance occurs on a lot, within a larger common plan of development or sale, within one (1) year of completing the original disturbance, the land disturbance area will be summed. If the summed land disturbance is greater than 2,500 square feet, then the total land disturbed must comply with the VSMP regulations. 1A.4 Examples 1A.4.1. Example 1 A residential subdivision was started after July 1, 2004. Only 60 of the 100 lots have been developed, with the remaining 40 lots constituting 1 acre or more. No development has occurred since around 2010. A developer intends to develop a vacant lh acre lot. This situation applies to a vacant lot in accordance with Section IA.3.3. The residential subdivision is a common plan of development or sale. While a clearly identifiable period of time of no construction has passed (Test 112), the project was never substantially completed (Test 91). Therefore, the developer requires a VSMP permit. 1A.4.2 Example 2 A residential subdivision was constructed around 2010. About 80 of the 100 lots have been developed, with the remaining 20 lots constituting 1 acre or more. The owner of one of the constructed homes intends to construct an addition to his home that will disturb 3,000 square feet. This situation applies to an individual parcel after intended construction has been completed in accordance with Section 1.3.4. The residential subdivision is a common plan of development or sale. However, the intended construction has been completed on this lot. Therefore, the addition is treated as a new development project. Since it disturbs less than I acre, no VSMP permit is required. COUNTY OF ROANOKE MARCH 22, 2016 1A-5 INTRODUCTION 1A.4.3 Example 3 A regional shopping center was built in the 1990s. It is currently marketing plans to develop several additional buildings in its parking lot. It anticipates that the buildings will be constructed one at a time. The anticipated disturbed area for the construction of each building is less than 1 acre, but the anticipated disturbed area for the construction of all of the additional buildings is over an acre. The common plan of development or sale occurred prior to July 1, 2004, and the original plan is completed. Each of the proposed buildings will disturb under I acre; however, since the 3 buildings are being marketed together, a new common plan of development or sale has been created and the construction of all three buildings must be considered as a single land -disturbing activity. A VSMP permit is required. 1A.4.4 Example 4 A regional shopping center was built in the 1990's. The owner intends to construct a building expansion that will disturb 0.8 acres. Just over a year after completion of the expansion, the owner of the regional shopping center decides to construct another building in its parking lot. The building construction will disturb 0.7 acres. The common plan of development or sale occurred prior to July 1, 2004, and the original plan is completed. The developer intends to construct a building expansion as a stand- alone project. The project will disturb less than I acre; therefore, no VSMP permit is required. After a distinct time period (I year) has passed with no construction activity, the developer decides to construct another building in its parking lot. Since a distinct time period (I year) has passed since the completion of the building addition, and since the new building is not part of the building expansion plan, and since less than I acre is disturbed, no common plan of development or sale is created and no VSMP permit is required. Note If the building expansion and additional building in the parking lot were part of an overall renovation plan that was intended to be constructed in phases, then a common plan of development or sale would have been created and a VSMP permit would have been required. 1A.4.5 Example 5 A congregation intends to build a new church in phases. Phase 1 is for a multipurpose sanctuary and parking and the construction will disturb 2 acres. Phase 2 is for a classroom expansion and its construction will disturb 0.5 acres. The phased church construction is a common plan of development or sale. A VSMP permit will be required for Phase 1 and Phase 2. COUNTY OF ROANOKE MARCH 22, 2016 IA -6 INTRODUCTION 1A.4.6 Example 6 A congregation intends to build a new wing for education use and expand the parking lot. No construction has been built for over a year. The construction will disturb 0.8 acres. The proposed project is separate from the original church construction; therefore, it is not part of a larger common plan of development or sale. Since disturbed area is less than I acre, no VSMP permit is required. 1A.4.7 Example 7 A developer has a plan approved that indicates that 0.9 acres will be disturbed. During construction, the developer actually disturbs 1.2 acres. The developer's plan indicates that less than I acre will be disturbed. Therefore, no VSMP permit was required. However, the developer actually disturbed over I acre. Therefore, the County issues a "Stop Work" order until a VSMP permit can be issued. A stormwater management plan meeting the stormwater management regulation technical requirements must be prepared and submitted, along with an executed and recorded maintenance agreement, revised performance security, and additional fees. The developer must ensure that an adequate SWPPP is prepared and available at the site. No further land -disturbance activities may occur until these items are completed and a VSMP permit is issued. The County may undertake other enforcement actions and penalties, depending on the circumstances. 1A.4.8 Example 8 An existing fast food restaurant is part of a partially developed commercial area. It plans a renovation that includes some parking lot changes and a small expansion to its seating area. The construction disturbed area is 0.7 acres. The commercial area is part of an active common plan of development or sale; however, the intended construction (fastfood restaurant) on this parcel has been completed. In accordance with Section ]A. 3.4, the renovation is a separate land -disturbing activity. Since less than I acre is disturbed, no VSMP permit is required. 1A.4.9 Example 9 A developer intends to construct a subdivision in two phases. He intends to develop Phase 1 first, followed by Phase 2. Since the subdivision is a common plan of development or sale, the two phases are treated as a single land disturbance activity and the determination of whether or not adequate stormwater management is being provided is analyzed for the subdivision as a whole. Stormwater management for the subdivision will be accomplished by a combination of BMPs on individual lots, to serve the individual lots; and BMPs intended to serve multiple lots. Due to the characteristics of COUNTY OF ROANOKE MARCH 22, 2016 1A-7 INTRODUCTION the site and the layout of the design, the overall plan indicates that the proposed BMPs for Phase 1 are not adequate to meet the pollutant removal requirements, but that with the construction of Phase 2, the overall effectiveness of the BMPs will be increased so they are adequate to meet the pollutant removal requirements for both Phase 1 and Phase 2 upon completion of Phase 2. The proposed plan is unacceptable in accordance with Section 1.3.6. Even though it is expected that portions of the common plan of development or sale will have more effective BMPs than other portions of the common plan of development or sale, and even though the common plan of development or sale is evaluated as a single land -disturbance activity; It is not acceptable to construct a portion of the common plan of development or sale without concurrent construction of adequate BMPs such that the technical requirements of the stormwater management regulations are met as each portion of the common plan of development or sale is completed. 1A.4.10 Example 10 A land -owner owns a parcel with existing public road frontage. The current zoning and subdivision requirements would allow for the parcel to be subdivided into 8 lots without the need for any additional public infrastructure. The property owner divides the parcel to create one 1/4 acre lot and constructs a single family house on it. Several years after completion of the single family house, the property owner divides the parcel again to create another 1/4 acre lot and constructs another single family house. Each project is separated by adequate time that they are independent projects and no VSMP permit is required. 1A.4.11 Example 11 A land -owner owns a 10 acre parcel with existing public road frontage. The current zoning and subdivision requirements would allow for the parcel to be subdivided into 8 lots without the need for any additional public infrastructure. The property owner divides the parcel to create one 1/4 acre lot and sells the individual lot to a developer to construct a single family house on it. After the property sale, the landowner posts a sign on his property stating that "land is available for development and that the owner will subdivide". The owner has created a larger common plan of development or sale by marketing development on his parcel. The developer may continue with his project to construct a single family house, since the property was sold to him prior to the creation of the larger common plan of development or sale. However, any further construction on the land- owner's parcel will require a VSMP permit. COUNTY OF ROANOKE MARCH 22, 2016 IA -8 INTRODUCTION STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL CHAPTER 2 Chapter 2 — Stormwater Management Plan Review and Approval In order to maintain the character and integrity of neighborhoods, to promote excellence of development, to prevent undue traffic and environmental hazards, and to encourage the most harmonious development and use of land, a site development plan, including a storm water management plan and sediment control plan, is required for commercial and residential development and shall be submitted to the County of Roanoke's Department of Community Development. Plans should be submitted in compliance with the Digital Plan Submission Guide policy. (http://www.roanokecountyva.gov/index.aspx?NID=317) These plans will be distributed to the appropriate departments and divisions for review and approval. When required, the applicant is also responsible for submittals to the Virginia Department of Transportation, Virginia Department of Environmental Quality, Western Virginia Water Authority, Town of Vinton, and other applicable regulatory agencies for their review and approval. When applicable, all of these entities must approve the site development plan prior to the issuance of any permits for all types of developments as required by the Zoning Ordinance, Subdivision Ordinance, Erosion and Sediment Control Ordinance, and Stormwater Management Ordinance. In cases where jurisdictional waters exist on the proposed site, the applicant may need to obtain approvals and/or permits from any or all of the following agencies: the U.S. Army Corps of Engineers (USACE), the Federal Emergency Management Agency, the Virginia Department of Environmental Quality (DEQ), and the Virginia Marine Resource Commission (VMRC). It is the responsibility of the applicant to obtain all necessary permits from USACE, DEQ, VRML, etc and provide Roanoke County with a copy of the required permit(s). Approval of plans by Roanoke County does not alleviate the applicant's liability of obtaining the required permit(s). 2.1 Overview of the Review and Approval Process No application for land development, land use conversion, or land disturbance can be approved, and no permits issued, without all of the elements required for a VSMP permit, as more fully described in the County Stormwater Management Ordinance and 9VAC25-870- 55. These elements generally include a permit application, erosion and sediment control plan, stormwater management plan, stormwater maintenance agreement, performance bond, fees, and executed development agreements. An agreement in lieu of a stormwater management plan may be accepted for a detached single family residence that is not part of a common plan of development. The submittal, review, and approval of site development plans, including stormwater management plans will follow the Roanoke County Land Development Procedures. This document is available from the County of Roanoke Department of Community Development website (http://www.roanokecountyva.gov/index.aspx?NID=317). COUNTY OF ROANOKE STORMWATER MANAGEMENT PLAN MARCH 22, 2016 REVIEW AND APPROVAL 2-1 STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL CHAPTER 2 2.2 Concept Stormwater Management Plan Submittal A concept site development plan, including a concept stormwater management plan, is strongly encouraged by the County of Roanoke when the proposed development meets any of the conditions set forth in the Roanoke County Land Development Procedures. A concept site plan or concept stormwater management plan may also be submitted for any project at the applicant's option. If submitted, the concept site development plan, including a concept stormwater management plan, should addressed items as outlined in Roanoke County's Land Development Procedures. 2.3 Stormwater Management Master Plan Submittal A stormwater management master plan and calculations are required for all phased projects that are part of a common plan of development. The master plan shall address grading, stormwater conveyance, and stormwater management BMPs for the overall development. The master plan is required to be approved prior to issuance of any permits. Each phase must provide adequate stormwater treatment to address the stormwater requirements for each individual phase. The Stormwater Master Plan shall show how the Designer will address stormwater management requirements for the entire project. At a minimum, the plans shall show the overall development, the location and type of the proposed BMPs required to treat the entire development, and contours. Additionally, the Designer shall provide applicable drainage areas to the BMPs and provide an accompanying VRRM worksheet to support the overall design. The final stormwater management master plan shall be appropriately sealed and signed by a licensed professional in adherence to all minimum standards and requirements pertaining to the practice of that profession as required in the VA Stormwater Management Regulations. 2.4 Stormwater Management Plan Submittal An approved site development plan and a local VSMP permit, is executed agreement in lieu of a stormwater management plan, is required prior to issuance of any other permits. The final stormwater management plan shall be appropriately sealed and signed by a licensed professional in adherence to all minimum standards and requirements pertaining to the practice of that profession as required in the VA Stormwater Management Regulations. The VSMP permit application information will be reviewed by the County of Roanoke. In addition to Roanoke County's review, the Virginia Department of Transportation may also review the site development plan with the stormwater management plan, as appropriate. Plans for review by these entities must be submitted directly to them, when required. COUNTY OF ROANOKE MARCH 22, 2016 2-2 STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL CHAPTER 2 Roanoke County strongly encourages all commercial projects or sites within a common plan of development that disturb between 0.90 and 0.99 acres to provide point(s) with northing and castings to delineate the disturbance limits on the plans. Additionally, Roanoke County strongly encourages that the plans include a note that the disturbance limits are clearly delineated by a surveyor in the field. Orange safety fence is the preferred method to mark the delineation. 2.5 Submittal of Stormwater Calculations Calculations shall be submitted to the County of Roanoke supporting the stormwater management and storm drainage design. Calculations shall be well organized and coordinated with the design to allow for efficient review by the County. Calculations shall be bound together in a booklet or stapled together, depending on the number of pages. Each page of the calculations should include the date prepared, a unique page number, and the date revised. Calculations shall follow the following general format: • Cover Sheet —The cover sheet shall contain the project name, property tax parcel(s) number(s), applicant's name, design professional's name, calculation date, and (for final calculations) the seal and signature of the design professional. • Table of Contents — A table of contents shall be provided where the calculations exceeds 25 pages, or where appropriate to assist the reviewer in locating information in the calculations. • Introduction— A general description of the project providing information to assist the reviewer in understanding the nature and scope of the project and of the storm drainage and stormwater management facilities that are proposed. This should also explain existing and proposed conditions. • Criteria and Methodology — A listing of the basic design criteria for water quality compliance, channel protection, flood protection, and TMDL (where appropriate). • References — A listing of references that are used in the calculations • Assumptions —A listing of all assumptions, and justification of the assumptions that are used in the calculations. • Analysis - The body of the calculations clearly labeled as to what stormwater BMPs or storm drainage system the calculations are for. The calculations shall be step-by- step to ensure that a reviewer that is not familiar with the project can follow the progression of the calculations. If computer printouts are provided highlight the input COUNTY OF ROANOKE MARCH 22, 2016 2-3 STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL CHAPTER 2 and output information and ensure that the input information is clearly supported in the calculations, and that the output is properly evaluated in the summary and conclusions. All calculation parameters must be fully supported and documented and include the design storm frequency, intensity and duration, times of concentration maps (including segment lengths, elevations, slopes, and flow types), soil curve numbers or runoff coefficients; calculations identifying pre -and post -development peak runoff rates and total runoff volumes for each watershed area, infiltration rates (where applicable), culvert, storm drain, and open channel capacities, flow velocities, data on the increase in rate and volume of runoff for the specified design storms, pre - and post -development phosphorous runoff rates and all other calculations needed to support the proposed design. • VRRM Worksheet — A digital copy of the VRRM worksheet shall be submitted with the plan submittal. Roanoke County uses an annual rainfall of 42" for all projects located within Roanoke County and precipitation rates from the NOAA precipitation chart for the Roanoke County Airport. • Drainage Area Maps — Drainage area maps shall be provided for storm drainage inlets and BMPs. Pre and post drainage area maps shall be provided. • Summary and Conclusions — A summary of the results, preferably in tabular or chart form for each storm drain system and stormwater BMP to indicate that the land disturbing project meets County requirements and any conclusions. Provide Q1, Q2, and Qlo for pre and post conditions. • Appendices and Attachments — Any supporting information such as pre -developed and post -developed drainage area maps, soils maps, U.S.G.S. quadrangle maps, NOAA precipitation chart, design nomographs, and computer printouts. Drainage maps must be clearly delineated and labeled to indicate the amount of area draining to each BMP and storm drainage inlet. Calculations that are not well organized and coordinated with the design shall be reiected and the submittal shall not be reviewed until proper calculations are submitted. 2.6 Changes and Modifications to an Approved Plan Changes to an approved subdivision or site plan, including an approved stormwater management plan, must be formally submitted for review to the County of Roanoke Department of Community Development at the counter with the Permit Technicians or via Roanoke County's FTP site. The County of Roanoke, upon receipt of the resubmittal of an approved development plan, shall review and approve or disapprove the resubmitted plan according to the Roanoke County Land Development Procedures. Approval or disapproval of the resubmitted plan shall be made in writing to the applicant. COUNTY OF ROANOKE Maitcx 22, 2016 2-4 STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL CHAPTER 2 Any use, arrangement, location, or construction not in compliance with the approved plan is a violation of the County Code. COUNTY OF ROANOKE MARCH 22, 2016 2-5 STORMWATER MANAGEMENT PLAN REVIEW AND APPROVAL EASEMENTS Chapter 3 - Easements 3.1 General This manual addresses three types of easements: Private drainage easements; Public drainage easements; and • Access Easements CHAPTER 3 Easements may be required as a part of a subdivision plat or site plan review. The purpose of this section is to provide policy, procedures, and guidelines for establishing easements for storm drainage and BMPs. Easements may grant certain rights and privileges to the County or other public entity such as VDOT for public easements, or to specific landowners and/or the County in the case of private easements. Proposed easements will be shown conceptually on preliminary site plans. The easements will be in final form on the submitted stormwater management plan and will be consistent with the design on final plats and site plans. Easements shall be dimensioned to allow them to be located in the field by providing dimensional ties to property corners, or centerline bearings and distances. Where easements are aligned with property lines, offset dimensions will be provided. Verification of easement locations will be required as a part of the as -built drawing requirements. If drainage or BMPs are found to have been constructed outside of the easement; then, the permittee will be responsible for vacating the original easement and recording a new easement, in the proper location, at the permittee's expense. Easements should not split property lines. Where an open channel or storm drain system runs parallel to a property line, it should be offset from the property line an adequate amount so that the easement is totally contained on the property that contains the open channel or storm drain and not be split onto the adjacent property. This provision allows construction of fences at the property line. All easements, shall connect to public access points. Easements shall be wide enough, and shall be located to allow convenient access for inspection and repairs, regardless of the minimum widths given herein. 3.2 Drainage Easements Public drainage easements giving the County or a public entity such as VDOT the right to discharge stormwater runoff onto private property is required for all public storm drainage systems and BMPs that are located on private property. This includes open channels, culverts, COUNTY OF ROANOKE EASEMENTS March 22, 2016 3-1 EASEMENTS CHAPTER 3 inlets, storm drains, stormwater management basins, and other best management practices that are owned, operated, and maintained by the County or other public entity such as VDOT. Public storm drainage systems are used to convey stormwater drainage from public property, public right-of-way, or another public storm drainage system through private property. Once the stormwater is discharged into a perennial or intermittent stream, or is otherwise managed, a public drainage easement is not required. Public BMPs are used to provide appropriate stormwater management for stormwater runoff generated by land development on public property. Examples of situations where a public drainage easement is required include: • Concentrated stormwater runoff from a County or County School Board owned site discharging to private property, including any open channels leaving the property or any storm drains leaving the property. • Concentrated stormwater runoff from public streets and open channels or storm drains from the public street right-of-way which passes onto any private property. Private drainage easements giving a private party the right to discharge concentrated stormwater runoff onto downstream private property is required whenever connection is made to a downstream private storm drainage system. No buildings, foundations, structures, fences or walls, not associated with the storm drainage system or BMP shall be located within a drainage easement. In addition, easements that contain open channels shall not be obstructed by fences or unmanaged vegetation. The closest edge of a storm drainage easement shall not be located within 10 feet of the rear wall of any individual single-family residential structure, except where the easement is required to access a BMP that is solely serving the single-family residence. Underground utility lines and structures shall be kept at least 5 -feet horizontal from drainage pipes, structures, and channels, except at utility crossings. Utility crossings at drainage easements shall be at as near 90-degress as possible. Where a storm drainage system terminates or starts short of a property line, adequate drainage easements shall be dedicated to allow for maintenance and future extension of the system through the property. 3.2.1 Culverts and Storm Drains The minimum width of drainage easements for culverts and storm drains shall be as follows: Pipe Size (width) Minimum Easement Width Smaller than 36" 20 feet 36" — 42" 25 feet COUNTY OF ROANOKE EASEMENTS March 22, 2016 3-2 EASEMENTS CHAPTER 3 48" — 60" 30 feet 66" — 78" 35 feet Minimum width given above is for installations with depths of cover of 10 -feet or less (measured at the top of pipe). For each additional 5 -feet of cover over 10 -feet (rounded up), the minimum easement width shall be increased by 10 -feet. For pipes that are larger than given in the table above, and for installations that result in minimum easement widths greater than 50 -feet due to installation depths, the minimum easement width shall be set by the County based on the width requirements to access the pipe in the future for repair. Drainage easements at the inlet and outlet of all culverts and storm drain inlets shall include the areas inundated by the headwater during the 100 -year storm. The easement shall extend a minimum of 10 feet from culvert inlets and outlets and storm drain inlets to allow for maintenance access. Where steep slopes and/or deep fills exist, additional easement area may be required to allow for proper access. Storm drain easements shall cross private driveways at perpendicular angles to the extent practical. 3.2.2 Open Channels The minimum width of the drainage easement required is dependent on the top width of the channel as indicated in Figure 3-1. The County may require wider easement width, if the open channel is located in rough terrain and additional width is required for access for inspection or repair. Figure 3-1 Minimum Easement Width for Open Channels DEPTH OF PROPOSED CHANNEL COUNTY OF ROANOKE March 22, 2016 EASEMENT WIDTH TOP WIDTH r 0' OF CHANNEL WIDTH OF BOTTOM 3-3 PROPOSED CHANNEL EASEMENTS EASEMENTS 3.3 Access Easements CHAPTER 3 Access easements giving the County the right to access private property for the purpose of inspecting, and if necessary to maintain or repair private BMPs is required for all private BMPs. This includes stormwater management basins, filter strips, bioretention trenches, underground detention areas, and all other BMPs. All structures, pond areas, embankments, inlet and outlet channels, and access and working areas necessary to inspect, maintain, and repair the facilities shall be included in access easements. The 100 -year flooding area of all stormwater basins or other holding structures shall be contained within the access easement area. In addition, all BMPs shall contain a minimum 20 -foot working area around all stormwater management basins and a minimum 10 -foot working area around all other BMPs and an access easement connecting to a public road. Depending on the size and location of the stormwater management facility, more than one vehicle accessible access easement connecting to a public road may be required. All stormwater structures and BMPs shall be accessible by vehicle. Areas within an access easement that are intended to be vehicle accessible shall have a maximum slope of 10 percent for unpaved surfaces and 18 percent for paved surfaces. The vehicle access shall be a minimum of 12 feet in width. The minimum width for an access easement shall be 20 feet. All access easements shall connect to a public road or right of way; unless a suitable blanket access easement is provided. 3.4 Maintenance of Easements Ownership of land within easements shall remain with the property owner. The property owner shall have the responsibility of maintaining the easement areas free of any obstructions or use that would interfere with the rights or privileges granted by the property owner. The property owner shall not alter the existing ground elevations or in any way redirect or obstruct stormwater flow. Any alterations to easements resulting in obstruction or redirection of flow will be returned to existing elevations immediately at the cost of the property owner. COUNTY OF ROANOKE EASEMENTS March 22, 2016 3-4 EASEMENTS APPENDIX 3A STANDARD EASEMENT AGREEMENTS County of Roanoke — Permanent Drainage Easement Agreement COUNTY OF ROANOKE March 22, 2016 3A-1 APPENDIX 3A EASEMENTS EASEMENTS APPENDIX 3A Exemption Claimed: Grantee is exempted from recordation taxes and fees pursuant to § 58.1- 811A(3), Code of Virginia. Prepared By: Tax Map No.: Property Owners: THIS DEED OF EASEMENT, made this day of , 20 , by and between AND (whether one or more, "Grantor") and the BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA ("Grantee"). WITNESSETH: That for and in consideration of the sum of One Dollar ($1.00), paid in hand at and with the execution and delivery of this Deed of Easement, and other good and valuable consideration, the receipt, adequacy and sufficiency of which is hereby acknowledged, the Grantor does hereby GRANT and CONVEY with General Warranty and Modern English Covenants of Title unto the Grantee, its successors and assigns, the following described easement, to -wit: A perpetual RIGHT and EASEMENT, approximately feet in width, to construct, operate, maintain, inspect and repair or replace a drainage system and related improvements including slope(s), if applicable, together with the right of ingress and egress thereto from a public road, upon, over, under, and across a tract or parcel of land belonging to the Grantor, acquired by deed dated and recorded in the Clerk's Office of the Circuit Court of Roanoke County, Virginia, in Deed Book , page , and designated on the Roanoke County Land Records as Tax Map No. (the "Property"). The location of said easement is more particularly described on the plat attached hereto as "Exhibit A" and by this reference made a part hereof (the "Plat"), and shown traversing as shown on Exhibit A. The Grantee agrees to restore and repair any actual damage to Grantor's Property which may be directly caused by the construction, reconstruction, or maintenance of said project except as hereinafter provided. The Grantor agrees that the Grantee will not be expected to restore the Property to the identical original condition, but rather as near thereto as is practicable, and that the Grantor will cooperate with the Grantee in effectuating such restoration. It is expressly agreed between the parties hereto that the Grantee and its agents shall have the right to inspect the easement herein granted and to cut, clear, and remove all undergrowth, obstructions, or improvements lying within, or upon said easement, that in any way endanger or interfere with the proper use of the same. The Grantor covenants that no building or structure shall be erected upon or within the easement herein granted or placed in such location as to render the said easement inaccessible. In the event that this covenant is violated, the Grantee COUNTY OF ROANOKE EASEMENTS March 22, 2016 3A-2 EASEMENTS APPENDIX 3A shall not be obligated to repair, replace, or otherwise be responsible for such improvements if damaged or removed. The Grantor acknowledges that the plans for the aforesaid project as they affect the Property have been fully explained to the Grantor or Grantor's authorized representative. The fixtures, facilities, lines, utilities, and any other improvements placed upon, under, or across the Property by the Grantee shall remain the property of the Grantee. The easement herein granted is in addition to, and not in lieu of, any easement or right-of-way now in existence or which may be acquired in the future. The Grantor covenants and aggress for themselves, and for their heirs, successors, successors in title, executors, legal representatives, and assigns that the consideration aforementioned and the covenants herein shall be in lieu of any and all claims to compensation and damages by reason of the location, construction, operation, maintenance, or reconstruction of or within the easement herein granted. The grant and provision of this Deed of Easement shall constitute a covenant running with the land for the benefit of the Grantee, its successors and assigns forever to have and hold unto the Grantee, its successors and assigns forever. , County Administrator, or his designee, of Roanoke County, Virginia, hereby joins in the execution of this instrument to signify the acceptance by said Board of Supervisors of the real estate conveyed herein pursuant to Ordinance No. adopted by the Board of Supervisors of Roanoke County, Virginia, on the day of , COUNTY OF ROANOKE EASEMENTS March 22, 2016 3A-3 EASEMENTS APPENDIX 3A IN WITNESS WHEREOF, the parties hereto have caused this agreement to be executed on their behalf. GRANTOR: (SEAL) (SEAL) (Name) (Name) GRANTOR ACKNOWLEDGMENT State of: County/City of: , to wit: The foregoing instrument was acknowledged before me this , day of , by: and (Notary Public Signature) (Notary Public Printed Name) My Commission expires: Registration # BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA: (SEAL) (County Administrator of Roanoke County, Virginia) COUNTY ACKNOWLEDGMENT State of: County/City of: to wit: The foregoing instrument was acknowledged before me this , day of 1 , by , County Administrator, on behalf of the Board of Supervisors of Roanoke County, Virginia. (Notary Public Signature) (Notary Public Printed Name) My Commission expires: COUNTY OF ROANOKE March 22, 2016 3A-4 Registration # (SEAL) EASEMENTS STORNIWATER HYDROLOGY Chapter 4 - Stormwater Hydrology CHAPTER 4 Stormwater hydrology defines the means and methods to calculating stormwater runoff from a designated area. This section documents the hydrologic practices used to establish design flows necessary to prepare the required stormwater peak flow and storage calculations. 4.1 References Except where more stringent requirements are presented in this Design Manual, stormwater hydrology shall comply with state requirements. The primary design references are: • VDOT Drainage Manual • VA SWM Handbook • BMP Clearinghouse 4.2 Design Frequencies 4.2.1 General Design frequencies shall be selected consistent with good engineering practice and economics. The design frequency requirements given in this Design Manual are minimum, specific conditions may dictate that less frequent design frequency should be used. 4.2.2 Storm Drainage Systems Storm drainage systems consist of manmade open channels, culverts, and storm drains. Designs shall be based on the following minimum design storm frequencies: Manmade Open Channels: Minor Channel Capacity 10 -year Minor Channel Protective Lining (Drainage Area 5 acres or less) 2 -year Minor Channel Protective Lining (Drainage Area over 5 acres) 10 -year Major Channel Capacity 100 -year Major Channel Protective Lining 10 -year (100 -year if potential for catastrophic failure) COUNTY OF ROANOKE MARCH 22, 2016 4-1 STORMWATER HYDROLOGY STORMWATER HYDROLOGY Culvertq Principal Arterial Roads Other Roads Storm Drains CHAPTER 4 25 -year 10 -year 10 -year All storm drainage designs for open channels, culverts, and storm drains shall be checked for the 100 -year flow condition where there is the possibility of flooding residences, commercial or industrial buildings, overtopping primary roads, experiencing significant economic loss, or catastrophic failure. Where justified by the consequences of failure, the minimum design frequency shall be increased. 4.2.3 Stormwater Management Facilities Designs shall be in accordance with the VA SWM Handbook and BMP Clearinghouse. 4.3 Time of Concentration (tc) and Travel Time (Tt) 4.3.1 General Time of Concentration (Q is the length of time required for a drop of water to travel from the most hydraulically distant point in the watershed, or subwatershed to the point of analysis. Travel Time (Tt) is the length of time required for that same drop of water to travel from the study point at the bottom of the sub - watershed to the study point at the bottom of the whole watershed. The travel time is descriptive of the sub -watershed by providing its location relative to the study point of the entire watershed. Therefore Time of Concentration is the summation of Travel Time values for the various consecutive flow segments. Travel Time and Time of Concentration generally consist of four flow types - overland flow, shallow concentrated flow, channelized flow, and pipe systems. Calculations shall be reviewed for reasonableness and the results shall be revised if needed to provide a reasonable velocity and flow time that will best represent the study area. When designing a drainage system, the flow path is not necessarily the same before and after land disturbing activities have been completed. Therefore, the travel time path shall be reflective of the actual conditions both before and after the land disturbing activities. In some cases, runoff from a portion of the drainage area that is highly impervious may result in a greater peak discharge than would occur if the entire area were COUNTY OF ROANOKE MARCH 22, 2016 4-2 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY CHAPTER 4 considered. In this case, adjustments can be made to the drainage area by disregarding those areas where flow time is too slow to add to the peak discharge. To prevent small drainage areas from skewing the time of concentration calculation results, when establishing sub drainage areas for analysis, the largest sub drainage area shall be no greater than 5 times the area of the smallest sub drainage area. Time of concentration maps shall include segment lengths, elevations at beginning and end of segment, slopes, and flow types. 4.3.2 Overland Flow Overland flow is flow that occurs at the upper end of a watershed, where flow is not concentrated and there are no channels. The length of overland flow shall be reflective of actual conditions and shall normally be no greater than 150 feet. Where the overland flow does not contain any slopes exceeding 5% AND if the soils are not designated as highly erodible, a maximum length of overland flow of 200 feet may be used. Highly erodible soils are designated as United States Department of Agriculture Natural Resources Conservation Service land capability classification (LCC) classes IIIe, IVe, VI, VII, or VIII or having an erodibility index greater than or equal to 8. Overland flow shall be calculated using the Seelye chart contained in the Appendix 4A for the Rational Method or TR -55 for the SCS Method. Roughness coefficients (Manning's n) for sheet flow can be found in the TR -55 Manual. 4.3.3 Shallow Concentrated Flow Shallow concentrated flow is the flow that occurs when minor rivulets form just downstream from the overland flow. The maximum allowable length for shallow concentrated flow shall be 1000 feet. Shallow concentrated flow shall be calculated using the Overland Flow Velocity Chart from HEC -19 or by using the nomograph entitled "Time of Concentration of Small Drainage Basins," developed by P.Z. Kirpich. Copies of the Kirpich chart and nomograph are contained in Appendix 4A and shall be used for the Rational Method. TR -55 shall be used for the SCS Method. Results from the Kirpich nomograph shall be multiplied by 0.2 for paved channels. 4.3.4 Channelized Flow Channelized flow occurs where stormwater flow converges in gullies, ditches, and natural or man-made water conveyances, including storm drain pipes and culverts. COUNTY OF ROANOKE MaitcH 22, 2016 4-3 STORMWATER HYDROLOGY STORMWATER HYDROLOGY CHAPTER 4 Channelized flow shall be calculated by use of the nomograph entitled "Time of Concentration of Small Drainage Basins," developed by P.Z. Kirpich. A copy of the nomograph is contained in Appendix 4A and shall be used for the Rational Method. TR -55 shall be used for the SCS Method. Results from Kirpich nomographs shall be multiplied by 0.2 for paved channels. 4.3.5 Pipe Flow Pipe flow is the flow that occurs through culverts and storm drains. Use full -flow pipe velocities, unless it may be demonstrated that the pipe will operate at partial full conditions. If it can be shown that the pipe will operate at partial full conditions, then the partial full pipe velocity may be used. Design of flow through culverts is presented in Chapter 6. Design of flow in storm drain systems is presented in Chapter 7. 4.4 Selection of Methodologies 4.4.1 General There are a variety of widely used hydrologic methodologies. Each has its strengths and weaknesses. In the interest of standardizing hydrologic calculations, the following methodologies will be used for all projects, unless the County agrees that good engineering practice dictates the use of another method. 4.4.2 Peak Discharge Methods for Design of Storm Drainage Systems The Rational Method may be used to design storm drainage conveyance systems for drainage areas up to 200 acres. Minimum time of concentration when using the Rational Method is 5 minutes. The SCS method may be used for drainage areas up to 10 square miles. For drainage areas greater than 10 square miles, calculations shall be performed using at least two separate methods as described in the VDOT Drainage Manual (SCS method, regression equations, and/or stream gage data). The design peak flow shall be selected based on a professional evaluation of the results of the various methods. 4.4.3 Hydrograph Methods for Design of Stormwater Management Facilities The modified rational method may be used to design stormwater management facilities where drainage areas are less than 20 acres and times of concentration COUNTY OF ROANOKE MaitcH 22, 2016 4-4 STORMWATER HYDROLOGY STORMWATER HYDROLOGY CHAPTER 4 are less than 20 minutes. Minimum time of concentration when using the Rational Method is 5 minutes. Please be aware that DEQ's VRRM worksheet does not support the use of the Rational Method when designing BMPs; therefore, Roanoke County recommends using the SCS Method. The SCS method may be used in all cases. The SCS method must be used where drainage areas are 20 acres or greater, or where times of concentration are 20 minutes or longer. Minimum time of concentration when using the SCS method is 6 minutes. 4.5 Methodologies Following is an abbreviated discussion of each method. Refer to the VDOT Drainage Manual and the VA SWM Handbook for a more complete discussion. 4.5.1 Rational Method A. General The Rational Method is expressed as: Q = CtCIA Where: Q = Peak flow rate of runoff, cubic feet per second (cfs) Cf = Saturation factor C = Runoff coefficient representing a ratio of runoff to rainfall (dimensionless) I = Average rainfall intensity for a duration equal to the time of concentration for a selected return period, inches per hour (in/hr) A = Drainage area contributing to the design location, acres (ac) B. Saturation Factor The saturation factor (Cf) is an adjustment factor for modifying the runoff coefficient (C) for storms that are less frequent than a 10 -year recurrence interval. The product of Cf and C should not be greater than 1.0. COUNTY OF ROANOKE MaitcH 22, 2016 Recurrence Interval (Years) Cf 2, 5, and 10 1.0 25 1.1 50 1.2 100 1.25 4-5 STORMWATER HYDROLOGY STORMWATER HYDROLOGY CHAPTER 4 Where the product of Cf and C is greater than 1. 0, use 1.0. C. Runoff Coefficient The runoff coefficient (C) is a variable of the Rational Method that requires significant judgment and understanding for proper selection. A range of C - values for a given land use is given in Appendix 4A. The coefficient must account for all the factors affecting the relation of peak flow to average rainfall intensity other than area adjustment. Some of these factors include land slope, condition of cover, and antecedent moisture condition. As the slope of the drainage basin increases, the selected C -value should also increase. The lower range of C -values should be used where the majority of the slopes are less than 2 -percent. The average range of C -values should be used where the majority of slopes are 2 to 5 -percent. The higher range of C - values should be used where the majority of the slopes are greater than 5 - percent. The higher range of C -values should be used in clayey and other less pervious soil areas. D. Average Rainfall Intensity See the VA SWM Handbook. An IDF curve file is located on the Roanoke County webpage for use with HydroCAD and Hydraflow at htlp://www.roanokecountyva.gov/index.aspx?NID=317 Cf factors are not included for Q25 and Qioo in the IDF files and should be accounted for the calculations. E. Drainage Area Drainage area (DA) is measured in acres and is determined from evaluating a topographic map of the area. 4.5.2 Modified Rational Method A. General The Modified Rational Method is a means to generate hydrographs for small drainage areas. The parameters for the calculation are the same as the COUNTY OF ROANOKE MARCH 22, 2016 4-6 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY CHAPTER 4 Rational Method, except that a series of average rainfall intensities from different storms with the same frequency and different durations are computed. The hydrograph from the critical duration storm is used to design stormwater management facilities. The Modified Rational Method recognizes that the duration of a storm is often longer than the time of concentration. This longer duration storm, even though it produces a lower peak Q, can produce a larger volume of runoff than the storm duration equal to the actual time of concentration of the drainage area. In order to ensure the proper design of stormwater management facilities, the runoff for the critical storm duration shall be used. B. Hydrograph Assumptions The hydrograph generated by the Modified Rational Method is based on the following assumptions: • Time of Concentration (te) = Time to Peak (Tp) = Time to Recede (Tr) • The length of the critical duration storm (De) is from 0 minutes until the time of selected duration. • The rate of runoff is 0 at time 0 minutes. The rate of runoff increases linearly with time until the peak rate of runoff is reached at time Tp. • The peak rate of runoff is maintained from time Tp until the duration of the storm (De). The rate of runoff then decreases to 0 at time De plus Tr. • The peak rate of runoff is based on the average rainfall intensity (I) for the given storm duration. C. Critical Duration Storm The critical duration storm is the storm of a given frequency that has a duration that yields the greatest volume of storage in a stormwater management facility when the storm hydrograph is routed through the stormwater management facility. The critical duration storm may be estimated for preliminary purposes; however, the actual critical duration storm must be determined by routing the various duration storm hydrographs through the stormwater management facility and demonstrating which storm duration gives the greatest volume of storage. COUNTY OF ROANOKE MARCH 22, 2016 4-7 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY CHAPTER 4 4.5.3 SCS Method A. General The SCS Method may be used for computing peak flows and hydrographs for storms of selected return frequencies. This approach considers the time distribution of the rainfall, the initial rainfall losses to interception and depression storage and an infiltration rate that decreases during the course of a storm. The information required to use the SCS Method to determine the peak rate of runoff, or to develop a runoff hydrograph is: • 24-hour total rainfall, and rainfall distribution type. The 24 hour precipitation rate is based upon NOAA values at the Roanoke Airport. These values can be found on Roanoke County's website or NOAA's website. • Time of Concentration (t,) in minutes, rounded up to the nearest whole minute; • Curve Number (CN), which is determined by Cover Types and Hydrologic Soils Groups; and • Drainage Area (A) in acres. If the drainage basin is over 20 acres, or if it contains areas of different land uses, the drainage basin should be divided into sub -basins. Each sub -basin should have similar land uses. When sub -basins are used, the following information is required to use the SCS Method to determine the peak rate of runoff, or to develop a runoff hydrograph: • 24-hour total rainfall, and rainfall distribution type. The 24 hour precipitation rate is based upon NOAA values at the Roanoke Airport. • Time of Concentration (Q in minutes for each sub -basin, rounded up to the nearest whole minute; • Curve Number (CN), which is determined by Cover Types and Hydrologic Soils Groups, for each sub -basin; • Drainage Area (A) in acres, for each sub -basin; and • Travel Time (Tt) of the flow from each sub -basin as it flows through downstream sub -basins. COUNTY OF ROANOKE MARCH 22, 2016 4-8 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY CHAPTER 4 If the SCS Method is being used to design a stormwater management facility, the following additional information is required to rout the runoff hydrograph through the facility and to generate an outflow hydrograph: • Elevation — Storage Relationship • Elevation — Discharge Relationship B. 24-hour Rainfall and Distribution The 24-hour rainfall is determined by NOAA precipitation amounts for Roanoke Airport. C. Curve Number The SCS method uses a combination of soil conditions and land use (ground cover) to assign a runoff factor to an area. These runoff factors, or runoff curve numbers (CN), indicate the runoff potential of an area. The CN requires significant judgment and understanding for proper selection. A table containing CNs for various cover types and soils conditions is contained in Appendix 4A. When calculating existing rates of runoff (pre -construction), assume that all cover types are in good hydrologic condition. Hydrologic Soils Groups (HSG) include types A, B, C, and D, with type A being the most permeable and type D the least permeable. Appendix 4B includes a listing of most soil names with their respective hydrologic soils types. Urban/udorthents soils shall be considered a Type D soil for design purposes. Soils maps for the Roanoke Valley may be obtained by referring to USDA web soil survey. Colored soil maps with support HSG documentation shall be included in the calculations packet D. Drainage Area Drainage areas for each sub -basin should be identified on an appropriate topographic map. E. Elevation — Storage Relationship When runoff hydrographs are being routed through a stormwater management facility, the relationship between the elevation (or depth) of stored water in the COUNTY OF ROANOKE MARCH 22, 2016 4-9 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY CHAPTER 4 facility and storage volume needs to be known and input into the calculation. Often this information is obtained by determining the pond area bounded by contour lines on a grading plan. Enough data pairs (elevation — storage) must be provided to properly model conditions at transition points. F. Elevation — Discharge Relationship When runoff hydrographs are being routed through a stormwater management facility, the relationship between the elevation (or depth) of stored water in the facility and the discharge flow rate from the facility needs to be known and input into the calculation. The development of this relationship requires an understanding of the design conditions and underlying hydraulic principles. The hydraulic principals and equations governing the discharge rate will often change several times at varying elevations. These include weir flow, orifice flow, culvert inlet control, culvert outlet control, open channel flow, and possible effects from downstream backwater. 4.7 Drainage Area Analysis To prevent the undersizing of stormwater management components, upstream properties conditions shall be considered in the drainage area analysis. Stream channel and improvements to any conveyance system shall be analyzed. When the drainage of a project leaves the site at multiple locations, the discharges at each location must be evaluated and addressed separately." COUNTY OF ROANOKE MARCH 22, 2016 4-10 STORMWATER HYDROLOGY STORMWATER HYDROLOGY APPENDIX 4A DESIGN AIDS FROM CHAPTER 6, VDOT DRAINAGE MANUAL Overland Flow Nomagraph — Seelye Overland Flow Velocity Time of Concentration for Small Drainage Basins — Kirpich Average Velocities for Estimating Travel Time for Shallow Concentrated Flow Rational Method Runoff Coefficients Runoff Curve Numbers for Urban Areas Runoff Curve Numbers for Cultivated Agricultural Areas Runoff Curve Numbers for Other Agricultural Areas COUNTY OF ROANOKE MARCH 22, 2016 4A-1 APPENDIX 4A STORMWATER HYDROLOGY STORNIWATER HYDROLOGY OVERLAND FLOW - SEELYE APPENDIX 4A REPRINTED WIT14 PMWISSION FROM 'BATA BOOK FOR CIVIL ENGINEERS" VOL. I- G9SIGN P-Kp EDITION tI550 BY E. E.SE€LYE COUNTY OF ROANOKE MARCH 22, 2016 4A-2 STORMWATER HYDROLOGY 1900 35-- 5•800 800 700 Tc. = 0 2 5L°.4` S -19 - 600 T�=Overland Flew Time, minutes :50 - L=Length of Strip, Feet 00 S=Slope, foot/foot Pavel =Raticinal "C" Value 400� 2 - v, 300 _ O.7 Bure Soff 0.5 20— Li 200 Pont' 0.4 Gross _Surface 'Av`e La lJLJ U. ro ge GrossUj1. 0. .. l 00 r ce o. 1,0 * D 15 90 - 2.0 H Q, $0 Dense - c 70 Grass 0.2 5,0 z 60 ILL! 0 C? z Lu 20,E �a 40 r �c > 10— 00 30 C 9 Lj ¢ -.j LIA z 20 a rs e� 7 .. i f� 60 OVERLAND FLOW TIME REPRINTED WIT14 PMWISSION FROM 'BATA BOOK FOR CIVIL ENGINEERS" VOL. I- G9SIGN P-Kp EDITION tI550 BY E. E.SE€LYE COUNTY OF ROANOKE MARCH 22, 2016 4A-2 STORMWATER HYDROLOGY STORMWATER HYDROLOGY OVERLAND FLOW VELOCITY t z -3 .5 I Zpul 30 20 c� r� io 75 L .I COUNTY OF ROANOKE MARCH 22, 2016 APPENDIX 4A a s 5 10 II Ar was l VELOCITY, Vf ( FT f SIC) 4A-3 0 zo I zo STORMWATER HYDROLOGY STORMWATER HYDROLOGY APPENDIX 4A TIME OF CONCENTRATION - KIRPICH (Note: Multiply Tc by 0.2 for Paved Channels) TC�9.094139-8-MU13 TIME OF CONCENTHATIDN OF SMALL DRAINAGE BASINS COUNTY OF ROANOKE MARCH 22, 2016 4A-4 STORMWATER HYDROLOGY TC -PLawlimt Mil)T[$ Z ]4 iWM, FEFT H (FT) 50$ LX A mPLE T[ 300 [.EN5TH - 3 [101? k7. --3 E CF UN CF-N;FLknON =14 1,1]N_ 158 k$ lao 15$ Ba _jag R1 5o N� LQ S000 40 40 ti 39 3000 w 2@ 21 - 1 220 lin 1fi Sad 5 5 4� i _3 2 l� � 3 =i r�+�Y h� 11 114; Val. 10 No. 5. Junr 1940. P. N2 TIME OF CONCENTHATIDN OF SMALL DRAINAGE BASINS COUNTY OF ROANOKE MARCH 22, 2016 4A-4 STORMWATER HYDROLOGY laswr■...■ar■*�a�� ■irfri■■I�i�a��r wsr�w��fliffl�■�iM1l�iii�l� .��1� moi!! q•����1,��■■ 1*Ali■�1�1■G■■■Y■/������ MEN qV WtM■E�E■f■7■Si■■7IFI 1f■■N■if111�s�■■■■'!U■T�A' NiFAZ'mZZ Amo■■on"Sol ■11[IL111i1MRnone J121,A01■■■10 ■■■lm"MmE■■pai iiiii mmriomgEmm 1■mo ■EE■ENN1111iIMINCEEPAIP M ■■ MINN ■■E■■ ■■�i1113HI IRI CAUFA n ■ s■E■ �Mv1njJ11f11'11WW1►Aj X111■■■ ■ ■■■'1■ ■■111010 101 FFFiN1� N■■■1 �! ice' i! l�s� iFl� [* iFi ■� w■ ��r �Y ir..��y■■■�11��� ��>�iri■ r�r�■Rq■�! �#�i �■.gl�M� iii �i ��'iY. i�'��M i';� !�� � � �■�i11�iYri�� uni■■■mm STORNIWATER HYDROLOGY RATIONAL METHOD - RUNOFF COEFFICIENTS APPENDIX 4A Description of Area Runoff Coefficients Business: Industrial and Commercial 0.80-0.90 Apartments and Townhomes 0.65-0.75 Schools 0.50-0.60 Residential - Lots 10,000 sf 0.40-0.50 - Lots 12,000 sf 0.40-0.45 - Lots 17,000 sf 0.35-0.45 - Lots >'/z acre 0.30-0.40 Parks, Cemeteries, and Unimproved Areas 0.20-0.35 Paved and Roof Areas 0.90 Gravel 0.90 Pervious Pavement Varies** Cultivated Areas 0.50-0.70 Pasture 0.35-0.45 Lawns 0.25-0.35 Forest 0.20-0.30 Steep Grass (2:1) * 0.40-0.70 Shoulder and Ditch Areas * 0.35-0.50 Comments - 1. The lowest range of runoff coefficients may be used for flat areas (areas where the majority of the grades and slopes are 2% and less). 2. The average range of runoff coefficients should be used for intermediate areas (areas where the majority of the grades and slopes are from 2% to 5%). 3. The highest range of runoff coefficients shall be used for steep areas (areas where the majority of the grades are greater than 5%), for cluster areas, and for development in clay soil areas. 4. The residential runoff coefficients include impervious and pervious amounts in the coefficient. * Lower runoff coefficients should be used for permanent or established conditions (post - construction), i.e. sizing stormwater management basins. * Higher runoff coefficients should be used to design roadside ditch linings (construction). The design considers the ditch lining as not yet established. ** Based upon Manufacturer's recommendation and BMP Clearinghouse specifications. COUNTY OF ROANOKE MARCH 22, 2016 4A-6 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY RUNOFF CURVE NUMBERS FOR URBAN AREAS APPENDIX 4A COUNTY OF ROANOKE MARCH 22, 2016 4A-7 STORMWATER HYDROLOGY Soil Group A B C D Cover type and hydrologic condition Open space (lawns, parks, golf courses, cemeteries): Poor condition (grass cover < 50%) 68 79 86 89 Fair condition (grass cover 50% to 75%) 49 69 79 84 Good condition (grass cover > 75%) 39 61 74 80 Impervious areas: Paved parking lots, roofs, driveways (excluding right-of-way) 98 98 98 98 Streets and roads: Paved; curbs and storm drains (excluding right-of-way) 98 98 98 98 Paved; open ditches (including right-of-way) 83 89 92 93 Gravel (including right-of-way) 76 85 89 91 Dirt (including right-of-way) 72 82 87 89 Urban districts: Commercial and business (85% average impervious area) 89 92 94 95 Industrial (72% average impervious area) 81 88 91 93 Residential districts by average lot size: 0.10 or less, town houses (65% average impervious area) 77 85 90 92 1/4 acre (38% average impervious area) 61 75 83 87 1/3 acre (30% average impervious area) 57 72 81 86 1/2 acre (25% average impervious area) 54 70 80 85 1 acre (20% average impervious area) 51 68 79 84 2 acre (12% average impervious area) 46 65 77 82 Developing urban areas: Newly graded areas (pervious areas only, no vegetation) 1 77 1 86 1 91 1 94 COUNTY OF ROANOKE MARCH 22, 2016 4A-7 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY RUNOFF CURVE NUMBERS FOR CULTIVATED AGRICULTURAL AREAS APPENDIX 4A Cover Treatment Hydrologic Soil Grou type condition A B C D Fallow Bare soil --- 77 86 91 94 Crop residue Poor 76 85 90 93 Cover (CR) Good 74 83 88 90 Row Crops Straight Row (SR) Poor 72 81 88 91 Good 67 78 85 1 89 SR and CR Poor 71 80 87 90 Good 64 75 82 85 Contoured (C) Poor 70 79 84 88 Good 65 75 82 86 C and CR Poor 69 78 83 87 Good 64 74 81 85 Contoured & Terraced Poor 66 74 80 82 (C & T) Good 62 71 78 81 C&T and CR Poor 65 73 79 81 Good 61 70 77 80 Small Grain SR Poor 65 76 84 88 Good 63 75 83 87 SR and CR Poor 64 75 83 86 Good 60 72 80 84 C Poor 63 74 82 85 Good 61 73 81 84 C and CR Poor 62 73 81 84 Good 60 72 80 83 C&T Poor 61 72 79 82 Good 59 70 78 81 C&T and CR Poor 60 71 78 81 Good 58 69 77 80 Close -seeded SR Poor 66 77 85 89 or broadcast Good 58 72 81 85 Legumes or C Poor 64 75 83 85 rotation Good 55 69 78 83 Meadow C&T Poor 63 73 80 83 Good 51 67 76 80 Comments: Crop residue cover (CR) applies only if residue is on at least 5% of the surface throughout the year. Poor = Factors impair infiltration and tend to increase runoff Good = Factors encourage average and better than average infiltration and tend to decrease runoff. COUNTY OF ROANOKE MARCH 22, 2016 4A-8 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY RUNOFF CURVE NUMBERS FOR OTHER AGRICULTURAL AREAS Comments: APPENDIX 4A Cover Hydrologic Soil Group type condition A B C D Pasture', grassland, or range- Poor 68 79 86 89 continuous forage for grazing Fair 49 69 79 84 Good 39 61 74 80 Meadow — continuous grass, 30 58 71 78 protected from grazing and generally mowed for hay Brush — brush -weed -grass mixture Poor 48 67 77 83 with brush as the major element Fair 35 56 70 77 Good 30 48 65 73 Woods — grass combination Poor 57 73 82 86 (orchard or tree farm) Fair 43 65 76 82 Good 32 58 72 79 Woods3 Poor 45 66 77 83 Fair 36 60 73 79 Good 30 55 70 77 Farmsteads — buildings, lanes, 59 74 92 86 driveways, and surrounding lots PasturePoor < 50% ground cover or heavily grazed with no mulch Fair 50% to 75% ground cover and not heavily grazed Good > 75% ground cover and lightly or only occasionally grazed Brush Poor < 50% ground cover Fair 50% to 75% ground cover Good > 75% ground cover Woods Poor — Forest litter, small trees and brush are destroyed by heavy grazing or regular burning Fair — Woods grazed but not burned, and some forest litter covers the soil Good — Woods protected from grazing, litter and brush adequately cover soil COUNTY OF ROANOKE MARCH 22, 2016 4A-9 STORMWATER HYDROLOGY STORMWATER HYDROLOGY APPENDIX 4B APPENDIX 4B DESIGN AIDS FROM CHAPTER 4, VA SWM HANDBOOK Rational Equation Coefficients for SCS Hydrological Soil Groups, Urban Land Uses Rational Equation Coefficients for SCS Hydrological Soil Groups, Rural and Agricultural Uses Roughness Coefficient "n" for Manning Equation — Sheet Flow Roughness Coefficient "n" for Manning Equation — Pipe Flow Roughness Coefficient "n" for Manning Equation — Constructed Channels Roughness Coefficient "n" for Manning Equation — Natural Stream Channels Hydrologic Soils Names in Virginia (7 sheets) COUNTY OF ROANOKE MARCH 22, 2016 4B-1 STORMWATER HYDROLOG R +0000NN Oo,r-v') IO O O O O O O O O O o O -:t Ol N�,c A N O 0, �O dl N� r- M M M M N N O O O O O O O O O A O O O O O O O O O O + O a, N 00 I'0 tt N -� �O O O O O O O O O O o O 01 01 N O O O O O O O O O o O -:t o0 N O r- Vl N O N G1 -- � r- M N N N N U O O O O O O O O O O + O — dl N v'i M O 00 110 �O O O O O O O O O O o O c o0 N N N O O O O O O O O O O O Sr + C, -- � r- M N N N N O �O O O O O O O O O O U o O N 00 00 01 O N O O O O O O O O O O S.r O 00 r- Vl N dl 0000 �xid000000 �ci N � � 0 w a It w o w I••I �� U W a � U U 00 Cd C W U � C U N N N N N N .N. .N. .N. .N. R w w O U 00 00 O v', r— O I'0 — I'0 0 0 0 0 0 0 O O O O O O o MO V'1 00 \O \O 00 M V'1 00 V'1 O -,t�O M M N �--� 00 l 110 V'1 l 110 V'1 110 110 V'1 N O 0 0 0 0 0 0 0 O O O O O O 00 l— \O Vl l— \O Vl ID W" W" A O O 0 0 6 0 0 6 6 O O O O O O + - oo N l N oo M — N — O O - O1� �O O 0 0 0 0 0 0 0 O O O O O O M 00 'n 01 00 O 00 00 00 00 r— N O 0 0 0 0 0 0 0 O O O O O O U O O 0 0 0 0 0 0 0 O O O O O O �O O 0 0 0 0 6 0 0 O O O O O O o0 V'1 V'1 V'1 00 V'1 Vl N N O 0 0 0 0 0 0 0 O O O O O O _O O00 Om O 00 N --� --� — O \O M M M M M N 0 0 0 0 0 0 O O O O O O O S.r O "o O o0 M V1 O l Ol l -:t M - M o O - O vl M M N N N N N N -- �O O 0 0 0 0 0 0 0 O O O O O O V. 0 01 DD DD O N O 01 DD O �O O O O O tt M N N N O N O 0 0 0 0 0 0 0 O O O O O O O i. x 0 0 6 0 6 0 0 0 6 O O O O O O U W O p N O O 0 0 0 0 0 0 0 �0 "C "C "O "C 7O Ra �I 73 7� cd ci G� Cd �I U In12 U U 12to U U U U 00 W to -,:3 0 b- � 7:3 U Y O C o Cd a w UO cr o un STORNIWATER HYDROLOGY ROUGHNESS COEFFICIENT "n" FOR MANNING EQUATION - SHEET FLOW COUNTY OF ROANOKE MARCH 22, 2016 Surface Description n Smooth Surfaces (Concrete, 0.011 Asphalt, Gravel, or Bare Soil) Fallow (no residue) 0.05 Cultivated Soils: Residue Cover < 20% 0.06 Residue Cover > 20% 0.17 Grass: Short Grass Prairie 0.15 Dense Grasses 0.24 Bermuda Grass 0.41 Range (Natural) 0.13 Woods: Light Underbrush 0.40 Dense Underbrush 0.80 4B-4 APPENDIX 4B STORMWATER HYDROLOGY STORMWATER HYDROLOGY ROUGHNESS COEFFICIENT "n" FOR MANNING EQUATION - PIPE FLOW Material "n" Range From I To Coated Cast Iron 0.010 0.014 Uncoated Cast Iron 0.011 0.015 Vitrified Sewer Pipe 0.010 0.017 Concrete Pipe 0.013 Common Clay Drainage Tile 0.011 0.017 Corrugated Metal (2 2/3 x 1/2) 0.023 0.026 Corrugated Metal (3x1 and 6x1) 0.026 0.029 Corrugated Metal (6x2 structural plate) 0.030 0.033 HDPE 0.012 COUNTY OF ROANOKE MARCH 22, 2016 4B-5 APPENDIX 4B STORMWATER HYDROLOGY STORMWATER HYDROLOGY APPENDIX 413 ROUGHNESS COEFFICIENT "n" FOR MANNING EQUATION - CONSTRUCTED CHANNEL Lining Material "n" Range From To Concrete Lined 0.012 0.016 Cement Rubble 0.017 0.025 Earth, Straight and Uniform 0.017 0.022 Rock Cuts, Smooth and Uniform 0.025 0.033 Rock Cuts, Jagged and Irregular 0.035 0.045 Winding, Sluggish Canals 0.022 0.027 Dredged Earth Channels 0.025 0.030 Canals with Rough Stony Beds, 0.025 0.035 Weeds on Earth Banks Earth Bottom, Rubble Sides 0.028 0.033 Small Grass Channels: Long Grass — 13" 0.042 Short Grass — 3" 0.034 COUNTY OF ROANOKE MARCH 22, 2016 4B-6 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY APPENDIX 413 ROUGHNESS COEFFICIENT "n" FOR MANNING EQUATION - NATURAL STREAM CHANNEL Channel Lining "n" Range From To 1. Clean, Straight Bank, Full Stage 0.025 0.030 No Rifts or Deep Pools 2. Same as #1, Some Weeds and Stones 0.030 0.035 3. Winding, Some Pools and Shoals, 0.033 0.040 Clean 4. Same as 93, Lower Stages, More 0.040 0.050 Ineffective Slope and Sections 5. Same as 93, Some Weeds and Stones 0.035 0.045 6. Same as 94, Stony Sections 0.045 0.055 7. Sluggish River Reaches, Rather 0.050 0.070 Weedy with Very Deep Pools 8. Very Reedy Reaches 0.075 0.125 COUNTY OF ROANOKE MARCH 22, 2016 4B-7 STORMWATER HYDROLOGY STORMWATER HYDROLOGY APPENDIX 4B Sa*!.� APP(?MATTOK HAlgx-p B SOILS,= AQUENTS flydgrp it Sail ,NamelUdgrp AQUULTi D ARAPAHOE B/D ARCOLA C ARGENT D ASBU1tN* C ASHE B ASHLAR B ASSATEA GUE A ATKINS D ATLFE C AUGUSTA c AURA 1i a4USTII+l4'1L E B AXIS D AYCCCK B BACKBAY D BADIN B BAILE D BAILEGAP B BAMA B BAYBORD I) BEACHES D BECKHAM 13 BE.LHAV,EN D BELTsvff LE C BELWIR, C 13ERKS C PJUWMIAN B BERTTE 13 BIBB D BILTMORE A BIR.DSBORO 13 BLADES D BLAIRTON C BLAND C BLEAKHILL C BLUEMON17 B 130HICKET D BOJAC B BILLING C BOLTON B BONNTAU A BOULWOUD B BOTETO RT C BOURNE C BO IwbkN'SVRL.E, BM BR DOCK B BRADLEY C BRANDYW It4E C BRECKNOCK B BREMO C BRENTSV LLE C BROADWAY B 13ItC]CIGRGAI] C BRUSHY B BUCHANAN C BUCi:IiALL B WCKS F3 BUCKTON 13 BUFFSTAT B BUGLEY cm BUNCOMBE A BURKETOWN C BURROWSWLLE C CALVERTON C CALYLN C CAM CA AJD CANEY'VnIE C CARBO C CARDIFF B C,AR.OLM G CARRVA.LE D CARTECAY C CATASKA D CATHARP]N C CATLETT 0D CATOCTIN C CATPOR4 T A CAVERNS B CECIL B CRAGRlN B CHAPANOKE C COUNTY OF ROANOKE MARCH 22, 2016 4B-8 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY APPENDIX 4B COUNTY OF ROANOKE MARCH 22, 2016 4B-9 STORMWATER HYDROLOGY Soil Nmm Soil N-a[lie Hydgrp CHAST_AIN D CHATUCGE D CHAVIES B CEINNEBY C CHESTER B CHEWACLA C CHICKAHOMINY D CIMHOWIE C CLIINTC:OTEACGUE D CfHIFLEY C crosvk Eu D CHRISTIAN C CID C CLAPHA lA w C CLEARBROOK D CLIFTON C CLUBCAF D CLYN ER D COASTAL BEACH D CODORT-79 C COLFAX c COLLEEN C: COLVARD B CODS B COMUS B CONETOE A CONGAREE B C OOSAW B COROLLA D CORY'DON D COTACO c Co U'rRsEY C COWEE B CCIXVILL.E L) CRAIGSVELLE B CRAVEN CREEDMOOR C CROTON D CULLEN c CULPEPER C DALEV TT T .F I) DA14DRHMGE D DAVIDSON B D A. HOO B/D DECATUR B V ARL4NT DEKALB C DELANCO C DELL S B/D DERROC B DE -LARD C DOGUE C DOROVAN D DOTHA_I B DRAGSTON C D ALL B DRYPOND D DU°CKST 1N AID DUFFIELD B DULLES D DUMFRIES B DUNDAR D DUNNING D DUPLIN G DL'1 AM E DYKE B EBBING C EDGEHILL C FDNEDY`ITD-WN B EDNEYiIILLE B EDCIM C ELBERT D ELIOAK C ELI0K c ELKTON OD £LLIBER A ELSrNBORO B E-NeORIA C ENDCALV C COUNTY OF ROANOKE MARCH 22, 2016 4B-9 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY APPENDIX 4B Anil Name yo . Snil Ngril Hydlrrp Soil Nam HyAm F-11%loN, C E.NOTT C ERNEST C ELBANKS B EULONTA c E. LTNOLA C EVA7yI��1xSHAM D EV',ARD R E [. M c FAC.EVILLE B �E+��r'7E�R�C�xREEN FAIRFAX �1'�y D .I~ALLSFNGTON B/D FAUGUIER. G FAYWOOD C FEATHERSTON, E D FISKERMAN D FL ATV4' ODDS C FLETCHER B FLUVANNA C FLI.TVAQUE. T D FORESTDAI_F D FORT{ C F1ANKSTOWN B FREDERICK B FRENCH C FRII"P A GALLA R GALNESBORO C GALESTOWN A GEORGEWLLE B GILPIN C GLADEHILL 13 GLENE.LG B GLENTV LLE c GLEN W- O.OD B GOLDSBC}RO B GOLDSTON C GOLDVEIN C GOI ESVIL.LE* B GREENLEE B GRT!1dSLFY R GRITNEY C GROSECLOSE C GROVER B GUERNSEY C GULLION C GUNSTOCK C GUYAN C GV4TNNETT B HAGERST0'W C' V•AI�'T HALEWOOD B I-LARTLETON B HATBORO D HAWKSBILL B HAYESVILLE B HAYNLA_R ,T D HAYTE:R B EkYWOOD B HAZEL C HAZEL C LIAZELTON B HELENA C CHA NERI HER NDON B HIWASSEE B HOADLY C HOBUCKEN D ROGELANND* C HOLLYWOOD D HU-NTING'TON B I3YATTs TL.LE B HYDE 11v HYDRAQUENTS B INCLEDONT B =ELL CID COUNTY OF ROANOKE MARCH 22, 2016 4B-10 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY APPENDIX 4B .Snil Nn= liyd-rn Soil Nam � IRONGATE B rUKA T AGORA C JACKLAND D JEDBURG JEFFERSON B JOINS c JOHNSTON D JLI ALUSKA $ K A LNILk B ILLY D KENfPS%,7LLE B KENANSVILLE A KENANSVILLE C KEYPORT ARL&NT SORA D KRSTON RD KLE.T B IKLINES)i IL.LE C1D KONNAROCK. C LAIDIG C LAE .ST A LAKBLAATD A LANENA D VARIANT L.4NSDALE B L AROQUE $ LAVvNES D LEAF D LEA SVILLE D LECK KILL B LEEDSVILLE* B LEETONIA C L.EGORE B L.ENEW C LE -NOIR D LEON B?D LEVY D LENV B Ln,TSBFRAY B LIBRARY D LIGNTUM c LILY B LII SLOE c Lrf-rLEJOE B LITS. G LLOYD C LOBDELL B LODI B LCiUISA B LOUISBURG B LOW -ELL C LU+C ETiS B LU Y A LUGN Nf C LUMBEE B!D LUNT C LYNCHBURG c MA.CGVE B MADISON B MAGOTHA D NLANASSAS IFI NIANOR B NLkN`I'ACHIE C NLANTEO C D MARBLE C MARGO B MARLBORO B NIARR B MARUNISCO c MA ADA. C �iASSANETI:'A B MASSANUTTEN 9 N kTAPEAKE B I\LkTNELFLAT B MATTAN D COUNTY OF ROANOKE MARCH 22, 2016 4B-11 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY Soil Na= �N ATTAPEX kLydgra C Sun—Name MATT.4,PONi Blvd= C MAYOR AN B MCGARY C Nff-ADOWS D M kDO "v'ILLE H MEGGE' `T D MELF'A 1) M i i .i ROCK A MIMEVILLE 7By B OLEN A A N'1C?NACAN C MO7vONGAHELA C' MO TALTO C lVTO 11 OSS l._. MOONL-6ow c I+ ORVE.N B MOUNT LUCAS C MUCKALEE D NFUNDF—N, B WATT D I+.'IYATT VARIANT D NAHUNTA C N.kNSEM0l\-D C NTA'%k'N-EY D N TABSCO C NEVAKC C NEWARK C NE -'FLAT D ]��ENVH-k A NICHOLOSON c NI c) D NOLICHU KY F3 NOL.IN B NORFOLK B OAKIML B OAfLAND S B OCCOQUAN B OKEE #TEE D OPEQUON' C O AN+GEBURG B ORENDA B OSIER A -D OTHEL,LO C..'D PACTOLUS A PAGEBROOK D PA-NIT,TIKF,Y B PAM—LEY A VARIANT PARKER B I" ARTI,OW D PEAKS C PEAWTCdK D COUNTY OF ROANOKE MARCH 22, 2016 4B-12 APPENDIX 4B 5uil NeseHydtry MAUIRERTOWN D MCQUIEN C MECKLENBURG C ME��sSLVIN D i MLRED D YLLV Y LUNI MONGLE C MO * �Ty �R�+N•t{.�S7�S�OF�R'� 1'H 0RiUSQ—Y YJ..L,LL* 7By B MT'A'EATHER* B MURRILL B MYERSVLLLE B NASON B NE TORIA GID NEIATERN C NEWNLkRC NDL,k C IOMERVMLE B OA KLE'T' C OCHLOCKONEE B ORANGE D QRISI,NY B PACOLET B PAh4LICO D PANORAMA B PASQUOT.AN BfD PENN CID STORMWATER HYDROLOGY STORNIWATER HYDROLOGY APPENDIX 4B Soil Name nXd= 5aJIAa= gr sou-Nam.�. Hydlelxp PHILO B PHILO OMT'* B PINEY�VOODS D PI KSTON B PISGAH c PO ATY D POLO MOKE ByD PODgDEXTER B POLAWANA A+D POOLER VARLAN7 D POPE B POPLLMENTO C PORTERS B PORTSMOUTH BID POUNCEY D PUNGO D PURCELLVILLE B FLTRDY D RABUM B RAINS BID RAMSEY D RAPIDAN B RAPPHANNOCK D RARITAN C RAYNE B READD GTON G REAVILLE G REMLr K A RJGEYY H RION B RI�`ERYTFIV R RO.ANOICE D ROHRERSVILLE D ROSS B ROWLAND C RUM OR.D B RUSHTOWN A RL TON B SAFELL B SASSAFRAS B SASSAFRAS R RATWOOK B, SAVANNAH C SCA'MR-9%-TLLE* C SCHArF'ENAIKE:R A SEABROOK C SEDGBFIELD G SEKIL B SENECA B SEQUOTA c SHELOCTA B SHENVAL B SHER.A_NDO B SI VA C S14OT70WER D STNDION B $ EETERVILLE C SLABTOIA'N B SLAGLE c SLICKENS B SNICI{ERSVILLE B SPEEDWELL I3 SPESSARD A SPTVF-y B SPOST YLV ANLA c SPRIGGS SPRIT-GWOOD B STANTON T) ST.ARR C STATE B STEINSBURG C STONEVILLE B STUART C STUNIPTTC�WN B SUC E.S 1B UDLEY B SUEQUE-1- ANNA D SUFFOLK. B SUSDLEY B SUSQUEI ANNA D SW AMP D COUNTY OF ROANOKE MARCH 22, 2016 STORMWATER HYDROLOGY 4B-13 STORNIWATER HYDROLOGY APPENDIX 4B SWEETAFpLE B SAID=Y C SYCOLINE D SYL o C SYLVATUS D TAL.LADEGA C' TALLA 009A C 'T'ARBORO A TATE. B TATUM B TET01-um C TENDER B THURh+MONP B TIDAL MARSH I] TMERVI LE B T10OA. B TOOA B TODDSTAV D TOMOTf E.Y BID TOMS c TORRINTA C 'iOTIER c TOXAWAY BST] TRAPPIST C TREGO B TRENHOLM D TUCKAHOE B TUAMLING B TURBEVILLE C TLTSQUrME B TYGART C U=E A UDIFLLTVE?N7S B UNISON B VANCE C VARTNA C VAUCLUSE C VERRTREES B WADESBORO B WAREE D WAKULLA A WALLEN B W_A.RMINSTER c WAT'AUGA B VWATEREE• B WATT D WA FOOL D WEAVER C WEAVERTON* C WEBBT VVN C NVEDOWEE B WE,EXSVE LE BID ';NTHADKEE D WEDZERT C1D W7 STMORELAND B NVESTON D VESTI°HAIL A B WEVERTON 13 V4qffiPLING B iNIM STONE D WIRTEFORD B WICKHAM B WILKES C IVOLFGAP B WOODINGTON &D WORSHAM D Vr'RIGHTSBOR0 C WPYTCK B VaIRNO C Vr1c'1ticK B YADISIN C. -D YEMASSEE C YEOPDA B YORK c ZEPP B ZION C ZOAR C COUNTY OF ROANOKE MARCH 22, 2016 4B-14 STORMWATER HYDROLOGY STORMWATER HYDROLOGY APPENDIX 4C APPENDIX 4C INFORMATION FROM VDOT HYDRAULIC DESIGN ADVISORIES Rainfall Intensities (inches/hour) for the Roanoke Valley (Based on VDOT HDA 05-03) COUNTY OF ROANOKE MARCH 22, 2016 4C-1 STORMWATER HYDROLOGY STORNIWATER HYDROLOGY APPENDIX 4C Note: For use with the Rational Method only. Use NOAA precipitation chart for SCS Method. RAINFALL INTENSITY (IN/HR) FOR THE ROANOKE VALLEY Table based on VDOT Hydraulic Design Advisory HAD 05-03 If = B / (to + D)E where: If = Rainfall intensity for a given recurrence interval, f, in inches per hour t, = Watershed time of concentration (assumed to equal the storm duration), in minutes B,D,E = As taken from HDA 05-03 table for [Roanoke] [Roanoke (city)] based on the designated storm frequency. COUNTY OF ROANOKE MARCH 22, 2016 4C-2 STORMWATER HYDROLOGY Storm Duration (min) 5 10 15 20 25 30 35 40 45 60 75 90 105 120 2 4.39 3.51 2.94 2.54 2.24 2.01 1.82 1.67 1.54 1.26 1.07 0.94 0.83 0.75 Cj 5 5.33 4.29 3.62 3.14 2.79 2.52 2.30 2.12 1.96 1.63 1.40 1.23 1.10 1.00 10 6.04 4.91 4.18 3.66 3.26 2.96 2.71 2.51 2.34 1.96 1.69 1.50 1.35 1.23 Cj U 25 6.78 5.49 4.68 4.11 3.69 3.36 3.10 2.88 2.70 228 2.00 1.79 1.63 1.50 50 7.37 5.96 5.09 4.49 4.04 3.70 3.42 3.19 3.00 2.56 2.26 2.04 1.87 1.73 100 8.08 6.49 5.56 4.92 4.46 4.10 3.81 3.57 3.37 2.92 2.61 2.37 2.19 2.04 Table based on VDOT Hydraulic Design Advisory HAD 05-03 If = B / (to + D)E where: If = Rainfall intensity for a given recurrence interval, f, in inches per hour t, = Watershed time of concentration (assumed to equal the storm duration), in minutes B,D,E = As taken from HDA 05-03 table for [Roanoke] [Roanoke (city)] based on the designated storm frequency. COUNTY OF ROANOKE MARCH 22, 2016 4C-2 STORMWATER HYDROLOGY OPEN CHANNELS Chapter 5 — Open Channels CHAPTER 5 Open channels are man-made ditches and channels and natural channels, that are used to convey stormwater flow. This section defines criteria and restrictions to be used in designing open channels. Where open channels are a part of a BMP, they shall comply with the state requirements for the purposes of water quality improvement; however, they shall also comply with this Design Manual's requirements for water conveyance. 5.1 References The primary design references are: • VDOT Drainage Manual • VDOT Specifications • VA E&SC Handbook • Hydraulic Engineering Circular Number 15 (HEC -15), Design of Roadside Channels with Flexible Linings, Current Edition, as amended • VA SWM Handbook 5.2 Design Methodology and Criteria 5.2.1 Major and Minor Manmade Open Channels A major channel is designed to convey over 5 acres. A minor channel is designed to convey 5 acres or less. 5.2.2 Design Flow Design flow for manmade open channels within a development is contained in Chapter 4.2.2. Additionally, all storm drainage designs for open channels, culverts, and storm drains shall be checked for the 100 -year flow condition where there is the possibility of flooding residences, commercial or industrial buildings, overtopping primary roads, experiencing significant economic loss, or catastrophic failure. 5.2.3 Hydrology See Chapter 4 for methodology used to determine peak flows for a given design frequency. COUNTY OF ROANOKE MARCH 22, 2016 5-1 OPEN CHANNELS OPEN CHANNELS 5.2.4 Channel Hydraulics CHAPTER 5 Open channel design will be based on Manning's Equation for open channel flow, unless good engineering practice dictates using HEC -RAS or other method. See the VA SWM Handbook and VDOT Drainage Manual, as appropriate. Q= A x 1.49/n x Rai' x Sv2 Where: Q = Flow in the open channel (cfs) A = Cross-section area of the channel (ft2) R = A/wetted perimeter (ft) S = Channel slope (ft/ft) n = Channel roughness coefficient Nomographs have been included in Appendix 5A for use in solving Manning's equation setting channel characteristics. 5.2.5 Channel Velocity The lining of minor channels with drainage areas of five acres and less shall be designed to withstand the erosive effects of a 2 -year storm. The lining of minor channels with drainage areas over five acres and major channels shall be designed to withstand the erosive effects of a 10 -year storm. The final design shall be consistent with velocity limitations for the selected channel lining, as presented in Table 5-1. Major channels associated with dam embankment spillways or other structures where catastrophic failure could result from a lining failure may be required to be designed to withstand a more severe storm event. Where open channels receive flow from storm drains, culverts, or other open channels, or in other areas where channel velocity may cause scouring or erosion, outlet protection or energy dissipation may be necessary to reduce the potential for severe erosion. For the design of energy dissipation devices, see Chapter 10. COUNTY OF ROANOKE MARCH 22, 2016 5-2 OPEN CHANNELS OPEN CHANNELS TABLE 5-1 Maximum Velocity Based on Channel Lining CHAPTER 5 Channel Lining Maximum Velocity (Design Storm Erosion Resistant Easily Erodible Soils, Soils Vegetative Lined Channels Tall Fescue Grass Mixtures 6 fps 4 fps Kentucky Bluegrass 6 fps 4 fps Annual and Perennial Rye 4 fps 3 fps Sod 4 fps 3 fps Geosynthetic Lined Channels VDOT EC -2 4 fps VDOT EC -3, Type A 7 fps VDOT EC -3, Type B 10 fps Other Per Mfr Recommendations Riprap (see VDOT Drainage Manual Appendix 7-D for n values) Dependent on stone size and thickness, see HEC -15 for design of riprap channels Concrete None , Erosion resistant soils include those with a high clay content and high plasticity, silty clay, sandy clay, and clay. 2 Easily erodible soils include those with a high content of fine sand or silty, lower plasticity or non -plastic, sand, silt, sandy loam, and silty loam with an erodibility factor (K) greater than 0.35. 3Soils shall be presumed to be easily erodible; unless a geotechnical investigation is performed that samples and tests the soils. 4All channels constructed in fills shall be considered to be in easily erodible soils. 5.2.6 Channel Slope Generally the channel slope shall be established by the site topography. Open channels must be graded to drain with no standing water following a rain event. The minimum allowable grade shall generally be 2 percent for vegetated -lined and riprap-lined open channels and 1 percent for a concrete open channel. The maximum allowable grade for a stormwater channel shall be dependent on the channel lining materials and its ability to withstand erosion during the design storm. COUNTY OF ROANOKE MARCH 22, 2016 5-3 OPEN CHANNELS OPEN CHANNELS 5.2.7 Cross Sectional Area CHAPTER 5 Open channel cross-section area shall be designed based on site restrictions and channel capacity requirements. The following information as a minimum shall be provided in either a table and/or detail on the design plans that includes the channel number if multiple swales are proposed, bottom width, top width, slope, side slopes, total depth including freeboard, and liner. Each swale should be included in the chart and not just a worst case scenario. Additionally, Qlo, Qio water depth, freeboard provided, and V2 shall be clearly indicated in the calculations. Acceptable cross-sectional area options include: • Vee • Parabolic • Trapezoidal • Rectangular • Yard A. Vee For design aids, see the VDOT Drainage Manual and the VA E&SC Handbook. Additionally computer software such as North American Green, Flowmaster, etc. can be used for design aids. The maximum side slope of a vee -shape open channel is 3 horizontal to 1 vertical for vegetated channels (including reinforced vegetated) and is 2 horizontal to 1 vertical for all other linings engineered to be stable at this slope. B. Parabolic For design aids, see the VDOT Drainage Manual and the VA E&SC Handbook. Additionally computer software such as North American Green, Flowmaster, etc can be used for design aids. COUNTY OF ROANOKE MARCH 22, 2016 5-4 OPEN CHANNELS OPEN CHANNELS C. Trapezoidal CHAPTER 5 For design aids, see the VDOT Drainage Manual and the VA E&SC Handbook. Additionally computer software such as North American Green, Flowmaster, etc. can be used for design aids. The maximum side slope of a trapezoidal -shape open channel is 3 horizontal to 1 vertical for vegetated channels (Including reinforced vegetated) and is 2 horizontal to 1 vertical for all other linings engineered to be stable at this slope. D. Rectangular Rectangular channels shall only be allowed where site restrictions prevent the installation of a vee, parabolic, or trapezoidal channel. The requirements for rectangular channels apply to any open channel with side slopes greater than 2 horizontal to 1 vertical. Rectangular channels must either be concrete or gabions. An approved safety barrier must be placed on both sides for the length of the rectangular channel, where the channel is more than 3 -feet deep. Care must be taken to ensure that energy dissipation is placed at the outfall of the rectangular channel to prevent erosion at the discharge point. E. Yard Yard swales that do not convey stormwater over multiple lots can utilize a basic yard swale detail without providing calculations if the following conditions are met: less than 0.25 acres drainage area, 2.0% minimum longitudinal slope, 6% maximum longitudinal slope, side slope of 4:1 H:V (maximum 3:1), bottom width of 0 feet, total depth of 1.1' (including the 0.5' of required freeboard), applicable top width based on side slopes, and type of liner labeled (i.e. grass). The Designer shall show a detail on the plan that meets the basic yard swale criteria. All other yard swales will required calculations and an applicable detail. Yard swales must have a grass liner. COUNTY OF ROANOKE MARCH 22, 2016 5-5 OPEN CHANNELS OPEN CHANNELS 5.2.8 Channel Lining CHAPTER 5 An open channel lining shall be designed based on the cross-section, slope, and channel velocity requirements. The design may be based on a consideration of either permissive velocity or tractive force as described in the VDOT Drainage Manual. The preferred method for analyzing channel linings is to compare the maximum permissible velocity for the channel lining, listed in Table 5.1 in this chapter of the Design Manual, to the design velocity computed using Manning's equation to verify that the selected lining is adequate. As an alternative, the selected lining may be analyzed using the Tractive Force Method published in the VDOT Drainage Manual. This method analyzes sediment critical shear loading on the open channel bottom and side slope. The permissible tractive force for various soils is located in the Appendix of the VDOT Drainage Manual. Open channels may have different lining materials in different channel reaches based on velocity and potential erosion conditions. Care must be exercised to avoid erosion at open channel transition points. The open channel lining will have an impact on the design capacity in the form of the roughness coefficient. A table of generally accepted roughness coefficient (n) for various channels and linings is included in Appendix 5A. Allowable open channel linings include the following: A. Natural To the maximum extent possible, natural channels shall be preserved. Design discharges from permitted land disturbing activities shall comply with the VA SWM Regulations. B. Vegetative -Lined Vegetated or grass -lined channels include man made channels lined with established vegetation. These channels usually include a geosynthetic mat for channel stabilization. The type of grass allowable for vegetative -lined open channels is dependant on the slope of the channel, and the peak calculated velocity. Table 5-1 details the maximum permissible velocities for various channel linings. COUNTY OF ROANOKE MARCH 22, 2016 5-6 OPEN CHANNELS OPEN CHANNELS CHAPTER 5 A permanent channel stabilization geosynthetic mat should be considered for all vegetated channels. There are a wide variety of geosynthetic stabilization mat options from various manufacturers. The geosynthetic mat selected should be adequate for the slope and design flow velocities calculated for the channel. Where appropriate, VDOT Road and Bridge Standard EC -2 or EC -3 may be used. Where a permanent geosynthetic mat is used to provide channel stabilization, information on the proposed mat, in the form of manufacturer's catalog information, shall be submitted as a part of the stormwater management plan. The catalog information shall include the manufacturer's recommendations for maximum allowable velocity. Design drawings must state that the geosynthetic stabilization mat shall be installed in strict accordance with the manufacturer's recommendations. Where a permanent channel stabilization geosynthetic is not used, a temporary geosynthetic lining designed to provide a measure of bank stability until such time a reasonably stable and mature stand of vegetation is established shall be provided. C. Riprap-Lined The use of vegetated and geosynthetic-lined open channels for gentle - sloped open channels and concrete for steep -sloped open channels is recommended. Riprap-lined channels will not be acceptable where vegetated or geosynthetic-lined open channels are feasible. However, where design flow velocities exceed the erosive capability of a natural or vegetative -lined channel, rip rap may be used as a channel liner in areas where erosion is a concern. For an extended length of high velocity channel, consideration should be given to using a concrete channel rather than rip rap. Riprap lining shall be properly embedded in accordance with VDOT standards to maintain intended ditch cross section. Where riprap is required due to velocity conditions, it shall meet VDOT Standards and VDOT Specifications. VDOT recommended 50 percent stone size (D5o) and weight (W5o) and recommended thickness (T) for various riprap classifications is included in Appendix 5A. D. Concrete -Lined Reinforced concrete shall be considered where design velocities dictate or where there is a need to provide the maximum level of erosion protection. COUNTY OF ROANOKE MARCH 22, 2016 5-7 OPEN CHANNELS OPEN CHANNELS 5.2.9 Freeboard Requirements CHAPTER 5 Manmade channels within a development shall have a minimum of 6" of freeboard above the calculated water level during the design peak flow, unless flow is supercritical. Where flow is supercritical, a minimum of 12" of freeboard is required. Yard swales require 6" of freeboard. Flow is supercritical when: V/(32.2xH)os> Where: V = velocity (fps) H = depth of flow (feet) At bends and curves, the freeboard shall be measured from the calculated water level, including the increased depth due to the superelevation of the water surface. 5.2.10 Calculation of Depth of Flow at Bends and Curves Increases in the depth of flow occur at bends and curves due to the superelevation of the water surface. Superelevation of the water surface at bends and curves is calculated by: AZ = V2 / (32.2 x r,) x (ro — ri) where AZ = difference in water surface elevation between the concave and convex banks (ft) V = average velocity (ft/s) rc = radius of the center of the stream at the bend (ft) ro = radius of the outside bank of the stream at the bend (ft) ri = radius of the inside bank of the stream at the bend (ft) The increase in the normal stream flow depth at the outer bank of an open channel bend is one half of AZ. 5.2.11 Channel Location and Width Restrictions on Residential Lots The tops of open channel banks shall be at least 20 -feet from a residence. Where manmade open channels collect stormwater from more than one lot and they are located on a residential zoned lot their use shall be restricted as follows. Where all requirements cannot be met, a closed pipe storm drain system is required. COUNTY OF ROANOKE MARCH 22, 2016 5-8 OPEN CHANNELS OPEN CHANNELS CHAPTER 5 • Residential lot size 1 acre or greater o No additional restrictions. • Residential lot size 0.5 acre or greater, but less than 1 acre o Open channel top width shall be a maximum of 15 feet o Maximum drainage area passing through the open channel shall be 5 acres. • Residential lot size less than 0.5 acre o Open channel top width shall be a maximum of 15 feet o Maximum drainage area passing through the open channel shall be 3 acres. The above restrictions do not apply if any one of the following conditions is present: • The open channel is a natural channel that has adequate capacity. The retention of natural channels is encouraged. • The open channel is a perennial or intermittent stream that has adequate capacity and will remain undisturbed. • It may be demonstrated that open channels are required as a part of an integrated design to obtain the necessary water quality treatment. 5.3 Environmental Considerations and Fishery Protection Construction or modifications to open channels shall comply with all applicable laws and regulations. The applicant is responsible for procuring all necessary permits, such as US Army Corps of Engineers and VA DEQ Wetland Permits, VA DEQ VPDES Permits, etc., prior to obtaining a Land Disturbance Permit. A copy of these permits shall be submitted to Roanoke County prior to scheduling the precon meeting or the Engineer shall submit a 3rd party report to the County that supports that the permits are not required. 5.4 Maintenance Requirements The permittee is responsible for maintenance of open channels until construction is complete, including final clean up and site stabilization, to the satisfaction of the County of Roanoke. After the completion of construction, the property owner is responsible for maintenance of open channels. Maintenance includes periodically pruning or mowing vegetation and removing debris. COUNTY OF ROANOKE MARCH 22, 2016 5-9 OPEN CHANNELS OPEN CHANNELS 5.5 Floodplain Studies CHAPTER 5 A floodplain study shall be performed for all drainage areas greater than 100 acres that do not have detailed FEMA Flood Insurance Study flood profiles or elevations. See Chapter 12 for additional information on floodplain requirements. COUNTY OF ROANOKE MARCH 22, 2016 5-10 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A AIDS FOR OPEN CHANNEL DESIGN FROM CHAPTER 7, VDOT DRAINAGE MANUAL Appendix 7B-1, LD -268, Roadside and Median Ditch Design Form Appendix 7B-3, Channel Stability Work Sheet APPENDIX 5A Appendix 7B-4, Riprap Design Work Sheet for Standard VDOT Riprap Sizes Only Appendix 7B-5, Riprap Design Work Sheet for other than VDOT Standard Riprap Sizes Appendix 7C-1, Nomograph for Solution of Manning's Equation Appendix 7C-2, Trapezoidal Channel Capacity Chart Appendix 7C-3, Nomograph for Solution of Normal Depth Appendix 7D-1, Values of Roughness Coefficient n, 2 sheets Appendix 7D-3, Standard VDOT Riprap Classifications, Weights, and Blanket Thickness Appendix 7D-5, Selection of Stability Factors Appendix 7D-6, Permissible Velocities for Erodible Linings Appendix 7E-1, Angle of Repose of Riprap in Terms of Mean Size and Shape of Stone Appendix 7E-2, Permissible Shear Stress for Non -Cohesive Soils Appendix 7E-3, Permissible Shear Stress for Cohesive Soils Appendix 7E-4, Bank Angle Correction Factor (Ki) Nomograph Appendix 7E-5, Correction Factor for Riprap Size Appendix 7E-6, Riprap Size Relationship Appendix 7E-7, Channel Side Shear Stress to Bottom Shear Stress Ratio Appendix 7E-8, Tractive Force Ratio (K2) Appendix 7E-9, Determination of Mean Spherical Diameter COUNTY OF ROANOKE MARCH 22, 2016 5A-1 OPEN CHANNELS OPEN CHANNELS E w� APPENDIX 5A COUNTY OF ROANOKE MARCH 22, 2016 5A-2 OPEN CHANNELS a Q a ¢ a a h1f]TN u C9 E• m � q Q AW113 Q st � H COUNTY OF ROANOKE MARCH 22, 2016 5A-2 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A CHANNEL STABILITY WORKSHEET CHANNEL DATA WS) E = (ft_) Native Material SO= (Rift) R = (k) 0-50 = dn - {ft,' ri - ffps) 075- A 75. -A - { ) Side Slope ` -- :i n STABILITY ()F NATIVE MATERIAL Tb= 62.4 * R o So = 62.4 a . _ .rp Bed = (Appendix 7E-2 or ) For D 5o _ (Appendix 7E-1) For D75 = _ (Appendix 7E-9) Side Slope v e1 0= _ [1 - (sir2 0/ sir? 6)) 0.' 1 = [1 - (sir? ° f sirs °.5 T. Side Slope (SS) _ �� Bed * I = ■ tr, Bed ) (=) (>) co Native Material on Eked i:s (stable) (unstable) Native Material on Side Slope is (stable) (unstable) COUNTY OF ROANOKE MARCH 22, 2016 5A-3 OPEN CHANNELS OPEN CHANNELS CHANNEL DATA Q= WS) RIPRAP DESIGN WORKSHEET (VDOT STANDARD SIZES) R = (ft - J, dn= (ft.) V. = (lp�j; A ft-) DETERMINE RIPiIP SIZE � = 42' Side Slope Side Slope =_: 1 Ki- — [1 - (sin2 01 ln:? 1)1 0,5 K, = [1 - (SiD2 . ' [ sing 42'0)10 6 _ For Specific Gravity - 2.65 and Stability Factor - 1. D; _ 0_0W V$'� f ld$Vg 0' * K1 1 Dab = 0,001 * 3 1 4.6 * 1. n APPENDIX 5A D,,, Computed = Note: All VDOT standard riprap (Class Al through Type lI) is assumed to have a 4 of appfoximately 42'and a Specific Gravity of 2,65. Therefore, the Computed D�: should be adjusted by the Stability Gorrection Factor (CSF) (it any) to derive a Final D,,_ The VDOT tstar1d i r J U. ;i5t� of riprep vwitti if1E7,� rittxt IIiylier D5,0 �51IVUJJJ UU UPV�JRed, Correction Factor For Stability Factor (SF) other than 1,2 (Default - 1.0) sF - (SF / 1.2)" _ 11.2)1 Final D54= r o Computed D.0 = _ RIPRAP RECOMMENDATION VDOT (Class) (Type) Thickness J ) - " (2 ; CSF, IVISD minimum) COUNTY OF ROANOKE MARCH 22, 2016 OPEN CHANNELS 5A-4 OPEN CHANNELS CHANNEL DATA o =(ft) d n w -(ft.) RIPRAP DESIGN WORKSHEET (NON-VDOT STANDARD SIZES) P R _ __ (ft.) V„ — (fps) A = (ftp} Side Slope = -1 ASSUMED RIPRAP SIZE - Dry _ VERIFY ASSUMED RI PRAP SIZE f = ' (Appendix 7E-1) Side Slope = 1 0 Ki = 11 - (sin2 a J sin'+)j'.s K, a [11 - (sin2 o f sing 0)] 4.5 For Specific Gravity = 2.65 and Stability Factor = 1.2 Ds,=0.001 9V,�'l(dam o.s.K, i.) n APPENDIX 5A DSD =0,001 # 3/( 0.56 1)= D5o Computed ( ) (<) (_) (>) Dso Assurned [ Assumed Dso is (correct) (incorrect) Note_ The above process of assuming a Dsa size, determining the natural angle of repose (0) and computing a D5o size should be repeated until the Assumed Dw size equals the Computed Dso size. Once the D34 size determination has been made, it should be adjusted forthe Specific Gravity Correction Factor C,, (if any) and the Stability Correction Factor (C$,) (if any) to derive a Final Dia. Correction Factor For Riprap Specific Gravity (Sg) pother than 2,65 (DefeuIt � 1 0) 0og=2.121(Sr,-1)1.e' = 2.12f( - V5 = Correction Factor For Stability Factor (SF) other than 1.2 (Default = 1.0) CSF = (SF 1 1-2)'-'= (_/ 1.2)1-'= Final Correction Factor = C = C,9 • CsF _ _ Final D,.= C . Computed D.- = . - RIPRAP RECOMMENDATION: ATION: Thickness (T) _ " 12 . D-,-, IVISD •rn-nimum) COUNTY OF ROANOKE NLARCH 22, 2016 5A-5 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A NOMOGRAPH FOR SOLUTION OF MANNINGS EQUATION G _ ., &� + . � � .4L COUNTY OF#0ANOKE MARCH 2 ,2 !6 5A-6 e .. - « 0c Dy <. _, con UQUIP e %7,} � . ' m- /u 2- 04 ���� © a � ¢ � ._ §� COUNTY OF#0ANOKE MARCH 2 ,2 !6 5A-6 e .. - - � � � � C) -m 1> Z) � � Ln � � � � 0 � � � � � z 2! .z G) m JC) c � 0 2! O#£& CHANNELS « r.{ 0 � . -� � �• o � I0, e rin ,/ m §\ rfl < n .. ,. � rn . - � � � � C) -m 1> Z) � � Ln � � � � 0 � � � � � z 2! .z G) m JC) c � 0 2! O#£& CHANNELS iY��•,..i.....!.a�a7777N■f ■Y!� � �+���••����c1, 111 WIM1ili°i�V����Y� >•��1!lii�-���q 11111'H41NF'Aii7iii�� ■Iii■!!l������{,I�IYIYNIJNIY■■�'1�■ �■ ■■71i■ifi����a71�111�1111�.711'I����Ii1■��� ■■A■■!!l����711i1 q.111Y91L� U�■��� atm■1■■s■i��irdY1N1t'IIFhIR,Il,1{i W��■ A■■�■■f ■®� IY■IIIt�i,nllirl■hn,u�MMlkr��1�w■■ ■■■�R*■■-� �wlaullu'MIIIIIYIIL1lLi1�w�■ ■■■O■■■■■ ■�Igktl1Y�171NIC111aM ■�■■:■■■■■r��7111�1111L■ I ■■ ■■aa,rMl,as�■�IUIIaENILyI■■,hlm■,w■■■t rM�rr+■■■'■■■�Illlllllfllll�l■I�+i�1!■■� ■■■■i�■'i■■■■111113[I,�II■��i■1�11,11L'■�I 1111■■��■■�■*Illllll�al �II111�Ilililgllt�w IIi1■■�!�■■■■Illlllnll Gldrll� fli11ai11�11■ INII�■■iY1■��€IIINIII1��11►�I�ii111�1�1��i__� ilIIIIIIiN11Yi�®• 1111111111111 M i � Ff1 i �+YIIIYIYtIi1a11 nu IIIIIIIIII IIhIFIFIIi� 1111111.111 III,i 111Yi■ �k11Yu1ua,rnuuu IIn11�1111111111111 1117111111J111�1�1��i III]ppI1f11111111111 III I I Pi 117 q 11111111 1119111111]IIIIIIIIII II�IIIIIIIJIIIIIIIIII 111JIIIIIIJIIIIICI�11 Ir�luul,uullrrrri ui���u�uimr�iir CII IN ■ ■ ■!�tl■ice 7 ■ W�I■!!7■ r71■!�!!' rria■�■■a OPEN CHANNELS APPENDIX 5A NOMOGRAPH FOR SOLUTION OF NORMAL DEPTH d s 0.0€]2 0.i 0,vS O.G4 11,D3 11.02 COUNTY OF ROANOKE MARCH 22, 2016 w z Z W�TL F.,O d h4rimnially from z+0 $cub@ o g M f8 h".1w -9 — lam T - I • C-0.01 OmiO F73/3 m I Q.Q 3 9 & # FT i.4 5A-8 Flro. tfUL4TTIOIi: d Ona -0.3 d/9 -Q14 d--Ql4(4)j 'a FT OPEN CHANNELS w n -p_ y 01-3B (FT 3/ s) 4Afi 2 D aO4 io 0.03 :B,Q 6.4 5A 0.112 a,p 3 �Ci 2.D 0,01 0.0€]2 0.i 0,vS O.G4 11,D3 11.02 COUNTY OF ROANOKE MARCH 22, 2016 w z Z W�TL F.,O d h4rimnially from z+0 $cub@ o g M f8 h".1w -9 — lam T - I • C-0.01 OmiO F73/3 m I Q.Q 3 9 & # FT i.4 5A-8 Flro. tfUL4TTIOIi: d Ona -0.3 d/9 -Q14 d--Ql4(4)j 'a FT OPEN CHANNELS OPEN CHANNELS APPENDIX 5A VALUES OF ROUGHNESS COEFFICIENT `n' CHANNELS Type of Channel and Description Minimum Normal Maximum LINED CHANNELS (Selected linings) a. Concrete 1. Trowel finish 0.011 0.013 0.015 2. Float finish 0.013 0.015 0.016 3. Gunite, good section 0.016 0.019 0.023 b. Asphalt 1. Smooth 0.013 0.013 --- 2. Rough 0.016 0.016 --- EXCAVATED OR DREDGED a. Earth, straight and uniform 1. Clean, recently completed 0.016 0.018 0.020 2. Clean, after weathering 0.018 0.022 0.025 3. Gravel, uniform section, clean 0.022 0.025 0.030 4. With short grass, few weeds 0.022 0.027 0.033 b. Earth, winding and sluggish 1. No vegetation 0.023 0.025 0.030 2. Grass, some weeds 0.025 0.030 0.035 3. Dense weeds or aquatic plants in deep channels 0.030 0.035 0.040 4. Earth bottom and rubble sides 0.025 0.030 0.035 5. Stony bottom and weedy sides 0.025 0.035 0.045 6. Cobble bottom and clean sides 0.030 0.040 0.050 c. Dragline excavated or dredged 1. No vegetation 0.025 0.028 0.033 2. Light brush on banks 0.035 0.050 0.060 d. Rock cuts 1. Smooth and uniform 0.025 0.035 0.040 2. Jagged and irregular 0.035 0.040 0.050 e. Channels not maintained, weeds and brush uncut 1. Dense weeds, high as flow depth 0.050 0.080 0.120 2. Clean bottom, brush on sides 0.040 0.050 0.080 3. Same, highest stage of flow 0.045 0.070 0.110 4. Dense brush, high stage 1 0.080 10.100 0.140 COUNTY OF ROANOKE MARCH 22, 2016 5A-9 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A VALUES OF ROUGHNESS COEFFICIENT `n' NATURAL STREAMS Type of Channel and Description Minimum Normal Maximum NATURAL STREAMS 1. Minor streams (top width at flood stage <100 ft) a. Streams on Plain 1. Clean, straight, full stage, no rifts or deep pools 0.025 0.030 0.033 2. Same as above, more stones and weeds 0.030 0.035 0.040 3. Clean, winding, some pools/shoals 0.033 0.040 0.045 4. Same as above, but some weeds and stones 0.035 0.045 0.050 5. Same as above, lower stages, more ineffective 0.040 0.048 0.055 slopes and sections 6. Same as 4, but more stones 0.045 0.050 0.060 7. Sluggish reaches, weedy, deep pools 0.050 0.070 0.080 8. Very reedy reaches, deep pools or floodways 0.075 0.100 0.150 with heavy stand of timber and underbrush b. Mountain Streams (no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stages) 1. Bottom: gravels, cobbles, few boulders 0.030 0.040 0.050 2. Bottom: cobbles with large boulders 0.040 0.050 0.070 2. Floodplain a. Pasture, no brush 1. Short grass 0.025 0.030 0.035 2. High grass 0.030 0.035 0.050 b. Cultivated area 1. No crop 0.020 0.030 0.040 2. Mature row crops 0.025 0.035 0.045 3. Mature field crops 0.030 0.040 0.050 c. Brush 1. Scattered brush, heavy weeds 0.035 0.050 0.070 2. Light brush and trees, in winter 0.035 0.050 0.060 3. Light brush and trees, in summer 0.040 0.060 0.080 4. Medium to dense brush, in winter 0.045 0.070 0.110 5. Medium to dense brush, in summer 0.070 0.100 0.160 d. Trees 1. Dense willows, summer, straight 0.110 0.150 0.200 2. Cleared land with tree stumps, no sprouts 0.030 0.040 0.050 3. Same as above, but with heavy sprout growth 0.050 0.060 0.080 4. Heavy stand of timber, a few down trees, little 0.080 0.100 0.120 undergrowth, flood stage below branches 5. Same as above, but with flood stage reaching 0.100 0.120 0.160 branches 3. Major Streams (top width at flood stage >100 ft) a. Regular section with no boulders or brush 0.025 --- 0.060 b. Irregular and rough section 0.035 --- 0.100 (The n value is less than that for minor streams of the same description, because banks offer less effective resistance.) COUNTY OF ROANOKE MaitcH 22, 2016 5A-10 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A STANDARD VDOT RIPRAP CLASSIFICATIONS, WEIGHTS, AND BLANKET THICKNESS Classification D5o ft W5oObs) Tin Class Al 0.8 50 20 Class I 1.1 100 26 Class H 1.6 300 38 Class III 2.2 1000 53 Type I 2.8 2000 60 Type II 1 4.5 1 8000 1 97 SELECTION OF STABILITY FACTORS Condition Stability Factor Range Uniform flow; straight or mildly curving reach (curve radius/channel 1.0 - 1.2 width >30); impact from wave action and floating debris is minimal; little or no uncertainty in design parameters. Gradually varying flow; moderate bend curvature (30 > curve 1.3- 1.6 radius/channel width > 10); impact from waves or floating debris is moderate. Approaching rapidly varying flow; sharp bend curvature (30 > curve 1.6-2.0 radius/channel > 10); significant impact from floating debris and/or ice, significant wind and/or bore generated waves (1-2 feet); high flow turbulence; mixing flow at bridge abutments; significant amount of uncertainty in design parameters. Channel bends when ratio of curve radius to channel width (R/W) > 30. 1.2 Channel bends when 30 > R/W > 10. 1.3- 1.6 Channel bends when R/W < 10. 1.7 COUNTY OF ROANOKE MARCH 22, 2016 5A-11 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A PERMISSIBLE VELOCITIES FOR ERODIBLE LININGS Soil type or lining (earth; no vegetation Maximum permissible velocities ft/sec for Water Water carrying Clear carrying sand and water fine silts gravel Fine sand (non colloidal) 1.5 2.5 1.5 Sandy loam (non colloidal) 1.7 2.5 2.0 Silt loam (non colloidal) 2.0 3.0 2.0 Ordinary firm loam 2.5 3.5 2.2 Volcanic ash 2.5 3.5 2.7 Fine gravel 2.5 5.0 3.7 Stiff clay (very colloidal) 3.7 5.0 3.0 Graded, loam to cobbles (non colloidal) 3.7 5.0 5.0 Graded, silt to cobbles (colloidal) 4.0 5.5 5.0 Alluvial silts (non colloidal) 2.0 3.5 2.0 Alluvial silts (colloidal) 3.7 5.0 3.0 Coarse gravel (non colloidal) 4.0 6.0 6.5 Cobbles and shingles 5.0 5.5 6.5 Shales and hard pans 6.0 6.0 5.0 COUNTY OF ROANOKE MARCH 22, 2016 5A-12 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A ANGLE OF REPOSE OF RIPRAP IN TERMS OF MEAN SIZE AND SHAPE OF STONE MEAN STONE WE, DSS, FT, COUNTY OF ROANOKE MARCH 22, 2016 ME" STONE SIZE. 0$0,mfw 5A-13 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A PERMISSIBLE SHEAR STRESS FOR NON -COHESIVE SOILS 4 a z 1.0 o. 1"v 01011- 0.1 ,01r_0.1 COUNTY OF ROANOKE MARCH 22, 2016 D �lnj I'D (, S 5 10 so 100 PARTICLE DIAMETER, D (rom) 5A-14 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A PERMISSIBLE SHEAR STRESS FOR COHESIVE SOILS "Co a:1112 1.0 Q's 0., 0.09 0.01 COUNTY OF ROANOKE MARCH 22, 2016 Chart 5.0 10.0 PLASTICITY INDEX -PA, 5A-15 .150-0 OPEN CHANNELS aou�C�' Divi WN � 5.0 10.0 PLASTICITY INDEX -PA, 5A-15 .150-0 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A BANK ANGLE CORRECTION FACTOR (Ki) NOMOGRAPH si Bank angle w.th horizontal �._ 4, Material angle sof (See curt 4 ) COUNTY OF ROANOKE MARCH 22, 2016 5A-16 OPEN CHANNELS .. i 314 . _. 2.1 �Q .70 �5 251 .go 20 .s ti p 40-- 4_90 90 J -- _92- 10 Example Given: Fire. Solution: C, 1a° Ki 4p Very Angular i a 0.885 050- 1.5 ft. COUNTY OF ROANOKE MARCH 22, 2016 5A-16 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A CORRECTION FACTOR FOR RIPRAP SIZE C=IAlA1" C = D 5o CORRECTION FACTOR SF s STABILITY FACTOR Ss = SPECIFI-C GRAVITY ]OF ROCK s c 8F 5.� Lo .a 4,0} 1.9 2-1 1 3.0. 1.7 25 1.6 1.5 2.4- 1.4 2' 1.� ------- ----�T---1 17 2S 3.0 1. Example: Given= olution., Ss = 2.65 C = 1.0 SF=1_2 COUNTY OF ROANOKE MARCH 22, 2016 5A-17 OPEN CHANNELS OPEN CHANNELS APPENDIX 5A COUNTY OF ROANOKE MARCH 22, 2016 imp w Ween, �'rrtid; So1u��'r: v*+a.T b� pati PO 4WOM11.0 fC. K 1- Q-73 5A-18 OPEN CHANNELS RIPRAP SIZE RELATIONSHIP .Modian R.pW d PVD • Aver dapn In m&Li dwml (M a 50 a ° ve'' 40 2s �. A r f.5 25- 5 16 15- 20 20 a i0 4 zo 10 5 4j) COUNTY OF ROANOKE MARCH 22, 2016 imp w Ween, �'rrtid; So1u��'r: v*+a.T b� pati PO 4WOM11.0 fC. K 1- Q-73 5A-18 OPEN CHANNELS OPEN CHANNELS CHANNEL SIDE SHEAR STRESS TO BOTTOM SHEAR STRESS RATIO Chart 13 kill t.� � o.a rw �.7 0.5 0 2 COUNTY OF ROANOKE MARCH 22, 2016 APPENDIX 5A SIDE SLOPE Z 4 3 w2; lZ 4 6 a 10 5A-19 Wd OPEN CHANNELS OPEN CHANNELS TRACTIVE FORCE RATIO (K2) aS 40 30 5 6M 6L 0 wi z 10 APPENDIX 5A Chart 14 0. a COUNTY OF ROANOKE MARCH 22, 2016 0.2 OAS 0_6 is i ,o 5A-20 1:z OPEN CHANNELS ANGLE OF RE I POSE -6 1 DEG. ENO Now m �a ■ 0. a COUNTY OF ROANOKE MARCH 22, 2016 0.2 OAS 0_6 is i ,o 5A-20 1:z OPEN CHANNELS OPEN CHANNELS APPENDIX 5A DETERMINATION OF MEAN SPHERICAL DIAMETER 10,1300 6 - ♦ --ter., — - — — 232 4 4 2 6a- 1 COUNTY OF ROANOKE MARCH 22, 2016 5A-21 2.24h rzcun+z dd -a r OPEN CHANNELS 7 •Q 5A-21 2.24h rzcun+z dd -a r OPEN CHANNELS CULVERTS Chapter 6 - Culverts CHAPTER 6 A culvert is a single run of storm drain pipe that conveys water or stonnwater under a road, railway, embankment, sidewalk, or other obstruction. A culvert typically connects two open channels, but they may connect an open channel to a storm drain. Proper culvert design must consider many factors including: • Design Flow • Inlet conditions (flow approach conditions, allowable headwater, culvert inlet configuration) • Culvert conditions (material roughness, pipe slope, and length) • Tailwater depth • Buoyancy potential • Environmental considerations and effects on aquatic life • Design loads and service life of the pipe material Refer to the VDOT Drainage Manual, for a more through discussion of these items. For the design of stormwater inlets and storm drains, see Chapter 7. 6.1 References Except where more stringent requirements are presented in this Design Manual, culverts shall comply with VDOT requirements. The primary design reference is the VDOT Drainage Manual. Other appropriate references include: • VDOT Standards • VDOT Specifications • VA E&SC Handbook • VDOT Instructional and Informational Memorandum IIM-1D-121.15, Allowable Pipe Criteria for Culverts and Storm Sewers • FHWA Hydraulic Design of Highway Culverts HDS No. 5, Pub. No. FHWA- NHI-01-020, Current Edition, as amended • FHWA Debris Control Structures Evaluation and Countermeasures HEC No. 9, Pub. No. FHWA-IF-04-016, Current Edition, as amended COUNTY OF ROANOKE MARCH 22, 2016 6-1 CULVERTS CULVERTS 6.2 Design Methodology and Criteria 6.2.1 Computation Methods CHAPTER 6 Manual computations use design equations and nomographs. Results are documented on VDOT's Design Form LD -269. Form LD -269 is included in Appendix 6A. There are a number of computer programs available to design culverts. Any of these computer programs will be acceptable if their methodologies are based on the same equations and nomographs accepted by VDOT, and if they provide the same documentation of inputs, assumptions, and output as are contained on VDOT's Design Form LD -269. 6.2.2 Hydrology A. Design Flow Methodology See Chapter 4 for methodology used to determine design flows. Generally culverts shall be designed based on the peak flow (steady state), ignoring the effects of temporary upstream storage. B. Obstruction Allowance An obstruction allowance shall be applied in critical areas where excessive backwater may result in property damage or be a potential safety hazard. After using the appropriate design methodology to calculate the peak stormwater flow for a given frequency, an obstruction allowance will be added to the peak flow to establish the design flow rate through the culvert. The minimum obstruction allowance factor is intended to account for normal culvert obstructions, which may lower the actual capacity of the culvert once constructed, and is based on the size of the culvert pipe in accordance with the following tabulation: Culvert Size 18" and less 21"-24" 30" 36" and greater COUNTY OF ROANOKE MARCH 22, 2016 Minimum Obstruction Allowance Factor 25% 20% 15% 10% 6-2 CULVERTS CULVERTS CHAPTER 6 6.2.3 Culvert Hydraulics A. Design Flow The design flow shall be the peak flow from the following frequency storm event, plus the appropriate obstruction allowance: Roadway Storm Frequency Primary & Arterial 25 -year Secondary & Other 10 -year These frequencies are minimum values. Designing for less frequent storms may be required where there is potential damage to structures, loss of human life, injury, or heavy financial loss in the event of flooding. Compliance with the National Flood Insurance Program (NFIP) is necessary for all locations where construction will encroach on a 100 -year frequency flood plain. In addition, the 100 -year peak flow (without the addition of the obstruction allowance) shall be routed through all culverts, determining the headwater depth behind the culvert with road overtopping, to ensure that buildings and other structures are not flooded and that adjacent roadways and adjacent properties do not suffer significantly increased damage during the 100 -year storm event. Storage impacts of water behind the culvert may be considered in the calculation, but is not required. B. Allowable Headwater The allowable headwater is the depth of water that can be ponded at the upstream end of the culvert during the design condition, as measured from the culvert inlet invert. The allowable headwater depth shall be limited by the following conditions: • Headwater does not cause upstream property damage; • Headwater does not increase the 100 -year flood elevation, as mapped by NFIP; • During a design storm event, the water surface shall be a minimum of 18 inches below the shoulder of the road at the point where the culvert crosses COUNTY OF ROANOKE MARCH 22, 2016 6-3 CULVERTS CULVERTS CHAPTER 6 under, or the low point of the road grade where the water would overtop the road; • Headwater depth shall not exceed 1.5 times the diameter or height of the culvert barrel; • Headwater depth shall not be such that stormwater flows to other ditches or terrain, which permits the flow to divert around the culvert. • The maximum overtopping depths during an 100 -year storm event for various street classifications are as follows: Classification Max. Depth at Crown Max. Velocity Local 1 ft* 6 fps Collector 1 ft* 6 fps Arterial No Overflow No Overflow Highway No Overflow No Overflow * Street overflow during a 100 -year storm will not be allowed if the street is the only means of access for 40 or more residences. A variance to this requirement may be granted if the applicant shows that the connecting roads will be experiencing substantial overtopping during a 100 -year storm and that there is no benefit to enforcing this requirement. • In most instances, the roadway overtopping may be treated as a broad crested weir. C. Tailwater Conditions Tailwater is the water into which a culvert outfall discharges. Culvert design shall be based on tailwater conditions that could reasonably be anticipated during the design condition. • If an upstream culvert outlet is located near a downstream culvert inlet, the headwater elevation of the downstream culvert may establish the design tailwater depth at the upstream culvert. • If the culvert discharges into a lake, pond, stream, or other body of water, the maximum water elevation of the body of water during the design storm may establish the design tailwater elevation at the upstream culvert. COUNTY OF ROANOKE MARCH 22, 2016 6-4 CULVERTS CULVERTS CHAPTER 6 D. Inlet and Outlet Control Culvert hydraulic design shall consider both inlet and outlet control conditions. For a culvert operating with inlet control, the flow capacity is governed by the inlet geometry. For an outlet control culvert, the inlet geometry, barrel characteristics and tailwater elevation all impact the flow capacity. Minimum culvert performance is determined by analyzing both inlet and outlet control for a given flow and using the highest resulting headwater. (i) Inlet Control The following factors are considered when calculating inlet control headwater: • Inlet Area — cross sectional area of the culvert entrance face • Inlet Edge —projecting, mitered, headwall, or beveled edges are common • Inlet Shape — rectangular, circular, elliptical, or arch are common The nomograph for inlet control for circular concrete, corrugated metal and corrugated HDPE culvert pipe is included in Appendix 6A. Nomographs for calculating headwater and flow capacity for other pipe geometries are contained in the VDOT Drainage Manual. (ii) Outlet Control The following factors are considered when calculating outlet control headwater: • Manning's Roughness (n) — based on barrel material, for recommended n values, see the table in Appendix 6A. • Barrel Area — cross section perpendicular to the flow • Barrel Length • Barrel Slope COUNTY OF ROANOKE MARCH 22, 2016 6-5 CULVERTS CULVERTS CHAPTER 6 • Tailwater Elevation Outlet control affects the hydraulic grade line of the flow through the culvert. To calculate the hydraulic grade, reference the equations for velocity, velocity head, entrance losses, friction losses, and exit losses contained in the VDOT Drainage Manual. The nomograph for outlet control on circular concrete and corrugated metal pipe is included in Appendix 6A. For additional nomographs, cross sections, and pipe materials, see the VDOT Drainage Manual. E. Culvert Velocity Outlet velocity must be checked to assure that excessive erosion and scour problems will not occur. MS 19 from the VA E&SC Handbook requires that discharges be made to an adequate channel. Culvert outlet protection shall be provided in accordance with the standards and specifications for Outlet Protection and Riprap in the VA E&SC Handbook. Culverts under roads shall be provided with end sections or endwalls in accordance with the outlet protection requirements of the VDOT Drainage Manual. Where a special design is needed to reduce outlet velocity, it shall be designed in accordance with VDOT standards. The minimum velocity in a culvert barrel must be adequate to prevent siltation at low flow rates. At a minimum this velocity shall be 3 feet per second for a 2 -year storm event. 6.2.4 Structural Design All culverts shall be designed to withstand a HS -20 highway loading, unless it crosses under a railroad, in which case the culvert shall be designed for railroad loads. The structural design shall consider the depth of cover, trench width and condition, bedding type, backfill material, and compaction. 6.2.5 Materials Culverts, both public and private, shall be constructed of materials as follows: COUNTY OF ROANOKE MARCH 22, 2016 6-6 CULVERTS CULVERTS CHAPTER 6 • Culverts in the VDOT right-of-way shall be VDOT approved materials in accordance with VDOT IE\4-LD-121.15 and VDOT Standard PC -1. Minimum depths of cover are shown in the PC -1 details. • Public culverts not in the VDOT right-of-way shall be: o Reinforced concrete pipe (RCP) Class III minimum or greater as required by loading conditions/cover or box. o Aluminized corrugated metal pipe (CMP), is allowed for private systems only for sizes 36 -inch diameter or smaller. Minimum gage thickness for CMP culverts shall be 16 gage for 30 -inch diameter and smaller. Minimum gage thickness for 36 -inch diameter CMP culverts shall be 14 gage. Trench design for CMP culverts shall meet ASTM or AASHTO standards. o Special CMP culverts including diameters greater than 36 -inch, elliptical, and arch designs will be considered on a case-by-case basis by the County of Roanoke for use as culvert pipe material in private storm drain systems. • Private culverts not in the VDOT right-of-way may be: o Reinforced concrete pipe (RCP) Class III minimum or greater as required by loading conditions/cover or box. o Aluminized corrugated metal pipe (CMP), for sizes 36 -inch diameter or smaller. Minimum gage thickness for CMP culverts shall be 16 gage for 30 -inch diameter and smaller. Minimum gage thickness for 36 -inch diameter CMP culverts shall be 14 gage. Trench design for CMP culverts shall meet ASTM or AASHTO standards. o Special CMP culverts including diameters greater than 36 -inch, elliptical, and arch designs will be considered on a case-by-case basis o Corrugated high-density polyethylene (HDPE) with an integrally formed smooth interior is allowed for sizes 48 -inch diameter or smaller. HDPE culvert pipe minimum cover must be in accordance with the County of Roanoke Inspection Specifications for HDPE Pipe contained in Chapter 7-B-11. COUNTY OF ROANOKE MARCH 22, 2016 6-7 CULVERTS CULVERTS 6.2.6 Culvert Sizes CHAPTER 6 The minimum culvert size shall be 18 -inch diameter, except that culverts under private entrance roads or driveways may be 15 -inch diameter if it meets all design flow conditions. Culverts shall meet all cover conditions required. Where the site conditions preclude the use of a single culvert barrel to meet the design flow conditions, multiple barrel culverts are acceptable. The maximum length of a culvert shall be 300 feet. A culvert longer than 300 feet shall have manholes or junction boxes and shall fall under the requirements of Chapter 7. 6.2.7 End Conditions End sections and headwalls shall normally be required on inlets and outlets, as described below. A. Prefabricated End Sections Prefabricated end sections, or flared end sections, provide for a better flow path, improving the design flow and headwater conditions. Prefabricated end sections shall be provided for culverts 18 -inch to 36 -inch diameter, except: • No end section is required for 15 -inch or 18 -inch diameter driveway culverts. • Where culvert alignment exceeds 20 feet in vertical elevation change or culvert slope exceeds a 2:1 slope, a standard concrete headwall shall be provided instead of a prefabricated end section. • Where a concrete headwall is provided. B. Concrete Headwalls and Structures Precast concrete headwalls shall be provided at all culvert inlets and outlets, unless other end conditions are allowed, as stated above. Precast concrete headwalls shall meet the requirements of the VDOT Standards and VDOT Specifications. COUNTY OF ROANOKE MARCH 22, 2016 6-8 CULVERTS CULVERTS CHAPTER 6 Wingwalls may be required in conjunction with headwalls. Culvert pipes 48" or larger in diameter shall have concrete wingwalls. Wingwalls are generally used where the culvert is skewed to the normal channel flow or where the side slopes of the channel or roadway are unstable. Wingwalls shall meet the requirements of the VDOT Standards and VDOT Specifications. Wing walls shall be set at an angle between 30 degrees and 60 degrees from the headwall. Concrete aprons may be used at the entrance or the exit of culvert. Aprons are typically used where high velocities or headwater conditions may cause erosion upstream or downstream of the culvert. An apron shall not protrude above the normal stream bed elevation. Special design concrete slab end treatment, per VDOT Standards, may be used as a concrete end section. 6.2.8 Multiple Barrel Culverts Multiple barrel culverts shall be allowed where single culverts cannot handle the design flow while meeting the required cover or headwater condition requirements. The design of multiple barrels should avoid the need for excessive widening of the upstream or downstream receiving channels. The minimum spacing between culverts in a multiple barrel culvert design shall be that required to provide adequate lateral support and allow proper compaction of bedding material under the pipe haunches. 6.2.9 Culvert Skew Where possible, culverts shall be installed parallel to the flow path. The maximum allowable skew shall be 45 degrees as measured from the line perpendicular to the roadway centerline. 6.2.10 Buoyancy Verify that culvert pipe, end sections, and concrete end wall structures will not fail under hydrostatic uplift conditions. Buoyancy force consists of the weight of water displaced by the pipe and fill material that is over the pipe (below the headwater depth). The force resisting buoyancy includes the weight of the pipe, weight of the water within the pipe, and the weight of fill material over the pipe. Buoyancy is more likely to be a problem where: COUNTY OF ROANOKE MARCH 22, 2016 6-9 CULVERTS CULVERTS CHAPTER 6 • Lightweight pipe is used • Pipe is on a steep slope (usually inlet control with the pipe flowing partially full) • There is little weight on the end of the pipe (flat embankment slopes, minimum cover, and/or no endwalls) • High headwater depths (HW/D>1.0) Suitable cover, footings, or anchor blocks may be required to ensure the culvert's integrity during design conditions. 6.2.11 Debris and Trash Racks In general, trash racks or debris deflectors shall not be used where other site modifications may be made to prevent excessive trash or debris from entering the culvert. However, they may be required at specific locations, by the County of Roanoke, where large amounts of storm debris may be anticipated. 6.3 Installation All culvert pipe, headwalls, end sections, outlets, and other peripheral structures shall be installed in accordance with VDOT requirements and the manufacturer's recommendations. The characteristics of the trench, bedding, and pipe material all impact the structural strength of the pipe system. The installed culvert conditions shall comply with the design assumptions and calculations. HDPE pipe installation shall comply with the County of Roanoke's Inspection Specifications for HDPE Pipe. A copy of this installation guide is provided in Chapter 7. 6.3.1 Bedding Material Bedding material and installation shall comply with the requirements of the VDOT Specifications. 6.3.2 Backfill Backfill shall be suitable material and shall be placed and compacted in accordance with VDOT Specifications. A minimum of 12" backfill shall be placed over the top of a HDPE or CMP culvert prior to placing pavement or other surface treatment. COUNTY OF ROANOKE MARCH 22, 2016 6-10 CULVERTS CULVERTS CHAPTER 6 6.4 Environmental Considerations and Fishery Protection Where compatible with good hydraulic engineering, a culvert shall be located in "dry" conditions. Where this is not possible, the culvert shall be located to minimize impacts to streams or wetlands. When a culvert is set in a perennial stream the invert of the culvert shall be set below the normal flow line of the stream as required in the VDOT Drainage Manual. The grade of the culvert shall not exceed the grade of the natural stream in the area. Where construction requires other environmental permits, the applicant shall be responsible for obtaining all necessary environmental permits and complying with their requirements. 6.5 Maintenance Requirements The permittee is responsible for maintenance of culverts until construction is complete, including final clean up and site stabilization, to the satisfaction of the County of Roanoke. After the completion of construction, the property owner or responsible party is responsible for maintenance of all culverts not located in public easements. No one shall modify culverts in any way that impairs or restricts flow. The property owner shall periodically remove silt and sediment from the pipe and prune vegetation around the pipe entrance to avoid restricting flow capacity and shall correct erosion damage as necessary. All removed silt and sediment shall be properly disposed of away from storm drainage pipes and open channels and shall be properly stabilized with vegetation. COUNTY OF ROANOKE MARCH 22, 2016 6-11 CULVERTS CULVERTS APPENDIX 6A AIDS FOR STORMWATER CULVERT DESIGN FROM CHAPTER 8, VDOT DRAINAGE MANUAL Appendix 8B-1, Culvert Design Form LD -269 Appendix 8C-1, Nomograph for Inlet Control for Circular Concrete Pipe Appendix 8C-2, Nomograph for Inlet Control for Corrugated Metal Pipe Nomograph for Inlet Control for Corrugated HDPE Pipe Note: This table is not from the VDOT Drainage Manual. Appendix 8C-4, Nomograph for Critical Depth, Circular Pipe Appendix 8C-5, Nomograph for Outlet Control for Circular Concrete Pipe Appendix 8C-6, Nomograph for Outlet Control for Corrugated Metal Pipe Appendix 8D-1, Recommended Manning's n -Values APPENDIX 6A Note: This table has been modified from VDOT's standard to include additional pipe materials. Appendix 8D-2, Entrance Loss Coefficients (Ke), Outlet Control, Full or Partly Full COUNTY OF ROANOKE MARCH 22, 2016 6A-1 CULVERTS CULVERTS APPENDIX 6A CULVERT DESIGN FORM (VDOT LD -269) COUNTY OF ROANOKE MARCH 22, 2016 6A-2 CULVERTS MONOSSON 12millil gnomon011013=1 MENI1101 oni MENNEN-30 ON INEEMENEEMEN EMENEENES MEN m WEEMENEEMEN Bonn on MENEEMENVEN NEESE MONSOON COUNTY OF ROANOKE MARCH 22, 2016 6A-2 CULVERTS CULVERTS APPENDIX 6A INLET CONTROL, CIRCULAR CONCRETE PIPE CHART 10 mo r � 168 010" EXAMPLE (-2) 43) ' +P•rBGsfa 9,,000 �.w S. r44 111 !.5 �,• #. m RD 96 1,000 3, —500 1-500 ara co ay goo #.. 4 100 A 49 � d¢ so �! Lk so Kw ENTRANCE a 40 scatE d TYPE 1.0 3d 30 ;11 �9�urtMlr�irA 9 w*od�a�l o - Q 0 IV 6r trrr and .I,a w 3$ harMaila $ d ;bl 6rarT4 ani #7 '.c[wr.1 w 10 - Ef d 7 .7 T T* Mf "Olt tel or (3) Frojecl 1 $ Karlt&M*►r It rcrlla pj.tk*% # mi a alrel*hr 61f WNW Omm ltafnll 0 de -d 0 141110,. V twarai as $ S Ill uttrakwC $ 1.0 —. . � s Ilk HEADWATER DEPTH FOR IIEAD aFA SCALM 283 CONCRETE PIPE CULVERTS sulrt,V, or CLIC FoQLLM JRR r"I scvlsM MAt 0" WITH INLET CONTROL COUNTY OF ROANOKE MARCH 22, 2016 6A-3 CULVERTS CULVERTS APPENDIX 6A INLET CONTROL, CIRCULAR CORRUGATED METAL PIPE CHART 2 we0 Ic,oOo 16$ 8,000 EXAMPLE I56 6,000 v, ai Intkn{3.43 a..{I 6, t } 5,000 0. 64 Ei t 144 4,000 MYr A hw 3° IJI: 3.000 4191}} b. tl1 9.� 9.474. 120 F 2.00.0 j2} !.1 a.S 3, IDS a (31 t.t 74. y 96 1,000 3, _ 800 3. ti - 84 in 600 Soo 400 s340 vi 13 r Z 200 � S4 O r W 4R w 10Q IJ 84 J �► � o 40 WLLJ — I.Q 36 30 JJw f WTRANCE a x 2 SGALE D TYPE "F 9 � 33 20 {I} 4044.4 11 � ,81 34 LLJd u14 slope 'l ..—_ 'b._ p 27 10 i31 frtjatll"t o •7 .7 24 .7 g � to v44 tint {�� �. i'JM R+al+er 21 4 hor1aan}7171 to 1t0i 11}, Ihte �1e�!'MI ieCVl n�:q IisR 4hrv9Yi� 3 0. 6 arvd 0 �f it, Q. rinrN aiI .6 12 o+lu�l•'lta. I � k!S S HEADWATER DEPTH FOR C. M. PIPECULVERTS WITH INLET CONTROL BVpEA4 �F PUBLIC ROADS J/1k 1443 COUNTY OF ROANOKE MARCH 22, 2016 6A-4 CULVERTS CULVERTS APPENDIX 6A INLET CONTROL, CIRCULAR HDPE PIPE 10..o 9,000 5 c -,ow D - .36 ip%ches (3-0 feel) .0c* 66 c"s 1 (200D 4, 800 HW ."Ar* ee.-) (I G 5.4 (2) 2.1 rD. 3 -4 -'3) 2 2 6-C -3 "5 1-0 us'a scale W or (31 pmjed s Z)T'zmta Ily tc s> 18t1p. ffief I u�e tilraigh line ihQugh 0 ar-d 0 soa�F?s, or reva-m- as 1,5 1.0 HEADWATER DEPTH FOR CORRUGATED HDPE CULVERTS WITH INLET CONTROL COUNTY OF ROANOKE MARCH 22,2016 6A-5 CULVERTS 'D m Not 800 -400 200 ul 0 }GO 48 CT , w Za < - T�f-c Hw sc AL. F FNTr-AfJ0E is 40 TYPE CL 3 a Lj 27 LU "5 1-0 us'a scale W or (31 pmjed s Z)T'zmta Ily tc s> 18t1p. ffief I u�e tilraigh line ihQugh 0 ar-d 0 soa�F?s, or reva-m- as 1,5 1.0 HEADWATER DEPTH FOR CORRUGATED HDPE CULVERTS WITH INLET CONTROL COUNTY OF ROANOKE MARCH 22,2016 6A-5 CULVERTS CULVERTS CRITCAL DEPTH, CIRCULAR PIPE 0 CHART 4 ��rt 2 ba tmmWT EXCI< D TOP Of I 1 1 a m 1 APPENDIX 6A so dko 50 60 Ta 10 s4 M04 DISC HA14GEaQ-CFS � e S t- a.e . 4 s r G} 1 4 0 i T ti 4 %k v i WJ 1 4 0 LOO 266 504 400 540 640 700 6O0 1-J4 11313* F � �IS{MARu�'G•�F$ I,Z • ID 1 -4.t CAMNO'f ExOEE V Ta. OF P1 41 iT +r0 I4{i¢"no 3ofto 4000 DPS-C,71ARC E - 41.FS Bu AlAu GF PUALI C ROM S j -A pi. 19 4 CRITICAL DE PTH CIRCULAR PIPE COUNTY OF ROANOKE MARCH 22, 2016 6A-6 CULVERTS CULVERTS APPENDIX 6A OUTLET CONTROL, CIRCULAR CONCRETE PIPE F xvvQ 16150 1000 BOLE s opo 400 Soo -to lza IQ8 919 •e4 66 •50 .S4 ;b .36 -11 -50 • 27 -14 -tM 10 kS 4 lbuheru 0 'PUSLOL 1 DAC4 JA, w!Q xa HEAD FOR CONCRETE RIPE CULVERTS FLOWING F4JLL n=0.012 COUNTY OF ROANOKE MARCH 22, 2016 6A-7 CULVERTS nw - �t�.£�z�o� a —wwvs�Fa 9i61i 5q� sumwwAip wrLICF c.%&Yik7 PUwrn¢ FuLr. .r# Ia wurr :rv....d tik-■rWkOL'Mwrx'ir &P G iFy�� .j+wv�W M iM �IiF}� ifTpe$1R .e ydsr In e� i J # Zp q� _ - +4 r34 ad i r# xa HEAD FOR CONCRETE RIPE CULVERTS FLOWING F4JLL n=0.012 COUNTY OF ROANOKE MARCH 22, 2016 6A-7 CULVERTS CULVERTS APPENDIX 6A OUTLET CONTROL, CIRCULAR CORRUGATED METAL PIPE 9000 x 4WRIEN OF, ".iC fmiLD5 jAN 1963 COUNTY OF ROANOKE MARCH 22, 2016 M h P4 p P. 400 106 00 90 —300 +$. ew41r! Celan P4P sal-iryf#, @*� PkO 6 Hwtr YF Rt70 TC Lo sit -60 crs L` c� —54 _ 100 W 4• E0 : to ; ag 33 b0 uj 30 . � 27 F0 2♦ ZI IQ 1� 6 15 s Is x 4WRIEN OF, ".iC fmiLD5 jAN 1963 COUNTY OF ROANOKE MARCH 22, 2016 M h P4 p P. W"(RG(C ,OUTLET =,,LRT FLpwING FULL +$. ew41r! Celan P4P sal-iryf#, @*� PkO 6 Hwtr YF Eapwii 4M8e1My i■ tfy y�4�H n4iil�n Lo If O IPA 4. LLI { z It 3 ,. — 4 � Y �o� e CxaM��t 4 a+aa aD�' ID 6A-8 0,00 HEAD FOR STANDARD O. M. PIPE CULVERT FLOWING FILL n 0,024 CULVERTS CULVERTS APPENDIX 6A OUTLET CONTROL, CIRCULAR CONCRETE PIPE RECOMMENDED MANNING'S n -VALUES Type of Conduit Wall Description Manning's n Concrete Pipe Smooth walls 0.010 - 0.013 Concrete Boxes Smooth walls 0.012 - 0.015 Corrugated Metal 2 2/3 by 1/2 inch 0.022 - 0.027 Pipes and Boxes, Annular or corrugations Helical Pipe 6 by 1 inch 0.022 - 0.025 corrugations 5 by 1 inch 0.025 - 0.026 corrugations 3 by 1 inch 0.027 - 0.028 corrugations 6 by 2 inch 0.033 - 0.035 structural plate 9 by 2 1/2 inch 0.033 - 0.037 structural plate Corrugated Metal 2 2/3 by 1/2 inch corrugations 0.012 - 0.024 Pipe Spiral Rib Metal Smooth walls 0.012-0.013 (Steel or Alum.) PVC Smooth interior 0.010 - 0.012 Polyethylene (PE or HDPE) Smooth interior 0.011 - 0.013 Corrugated PE or HDPE I Corrugated interior 1 0.022 - 0.026 Note 1: The values indicated in this table are recommended Manning's "n" design values. Actual field values may vary depending on the effects of abrasion, corrosion, deflection, and joint conditions. Concrete pipe with poor joints and deteriorated walls may have "n" values of 0.014 to 0.018. Corrugated metal with join and wall problems may also have higher "n" values, and in addition, may experience shape changes which could adversely affect the general hydraulic characteristics of the culvert. Note 2: Fore further information concerning Manning n values for selected conduits consult Hydraulic Design of Highway Culverts, Federal Highway Administration, HDS No. 5, page 163. COUNTY OF ROANOKE MARCH 22, 2016 6A-9 CULVERTS CULVERTS APPENDIX 6A ENTRANCE LOSS COEFFICIENTS (Ke) OUTLET CONTROL, FULL OR PARTIALLY FULL Type of Structure and Design of Entrance Coefficient Pipe, Concrete Mitered to conform to fill slope 0.7 End -section conforming to fill slope 0.5 Projecting from fill, square cut end 0.5 Headwall or headwall and wingwall Square -edge 0.5 Rounded (radius = 1/12 D) 0.2 Socket end of pipe (groove end) 0.2 Projecting from fill, socket end (groove end) 0.2 Beveled edges, 33.7° or 45° bevels 0.2 Side or slope -tapered inlet 0.2 Pipe, Corrugated Metal (or Corrugated HDPE) Projecting from fill (no headwall) 0.9 Mitered to conform to fill slope, paved or unpaved slope 0.7 Headwall or headwall and wingwall, square -edge 0.5 End section conforming and to fill slope 0.5 Beveled edges, 33.7° or 45° bevels 0.2 Side or slope -tapered inlet 0.2 Box, Reinforced Concrete Wingwalls parallel (extension of sides), 0.7 square edged at crown Wingwalls at 10° to 25° or 30° to 75° to barrel, square edged on 3 edges 0.5 rounded on 3 edges to radius of 1/12 barrel 0.2 Wingwalls at 30° to 75° to barrel, crown edge rounded to radius 1/12 of barrel 0.2 Side or slope -tapered inlet 0.2 Note: End Section conforming to fill slope made of metal, concrete, or HDPE, are the sections commonly available from manufacturers. From limited hydraulic test they are equivalent in operation to a headwall in both inlet and outlet control. Some end sections incorporating a closed taper in their design have a superior hydraulic performance. These latter sections can be designed using the information given for the beveled inlet. COUNTY OF ROANOKE MARCH 22, 2016 6A-10 CULVERTS STORM DRAINS Chapter 7 - Storm Drains CHAPTER 7 A storm drain is a drainage system that conveys water or stormwater, consisting of two or more pipes in a series connected by one or more structures. Storm drains collect and transport stormwater from a site primarily through the use of a closed pipe network. For the storm water to be efficiently handled in a storm drain, the site must also have an efficient way to collect stormwater runoff and have it enter into the piped network. Once in the storm drain, the stormwater is routed to a discharge outfall. Storm drain systems include: • Measures to get stormwater runoff to inlets, • Inlets, and • Storm drain pipes and structures that stormwater runoff must pass through to reach the outfall This section defines criteria and restrictions that shall be used in designing and constructing public and private storm drains. See the VDOT Drainage Manual for more in-depth information. All storm drains 12 inches in diameter and larger shall have profiles prepared and submitted to the County. 7.1 References Except where more stringent requirements are presented in this Manual, storm drain collection systems shall comply with VDOT and other state requirements. The primary design reference is the VDOT Drainage Manual. Other appropriate references include: • VDOT Standards • VDOT Specifications • VA E&SC Handbook • FHWA Drainage of Highway Pavements HEC No. 12. • FHWA Urban Drainage Design Manual HEC No. 22. • VA Stormwater Management Handbook, Chapter 6 Appendix 6B (Karst Guidelines) COUNTY OF ROANOKE MARCH 22, 2016 7-1 STORM DRAINS STORM DRAINS 7.2 Design Methodology and Criteria 7.2.1 Computation Methods CHAPTER 7 Manual computations use design equations and nomographs. Results are documented on VDOT work sheets. Copies of these forms are included in Appendix 7A. • Form LD -204 Stormwater Inlet Computations • Form LD -229 Storm Drain Design Computations • Form LD -347 Hydraulic Grade Line Computations There are a number of computer programs available to design storm drainage systems. Any of these computer programs will be acceptable if their methodologies are based on the same equations and nomographs accepted by VDOT, and if they provide the same documentation of inputs, assumptions, and output as are contained on VDOT's work sheets. Computation methods are explained in detail, including comprehensive design examples, in the VDOT Drainage Manual. 7.2.2 Hydrology A. Design Flow Methodology Calculations establishing the design flow shall be submitted with the Stormwater Management Plan. Design flows shall be based on ultimate build -out of the contributing watershed based on the current Comprehensive Plan. 7.2.3 Design Flows The following minimum storm frequencies shall be used: A. Inlets Inlets shall be designed for storm frequencies and intensities consistent with the VDOT Drainage Manual. For reference, the VDOT table and its accompanying notes have been included in Appendix 7A. COUNTY OF ROANOKE MARCH 22, 2016 7-2 STORM DRAINS STORM DRAINS B. Storm Drains CHAPTER 7 Storm drains shall be designed for the storm frequencies and intensities consistent with the VDOT Drainage Manual. For reference, the VDOT table and its accompanying notes have been included in Appendix 7A. Unless otherwise specified by the VDOT Drainage Manual, a 10 -year frequency design storm shall be used in developing design flows. 7.2.4 Measures to Convey Stormwater Runoff to Inlets A. Pavement Drainage One objective in the site design is to collect and remove stormwater runoff from critical areas as efficiently as possible. A properly designed system will ensure that roadway surfaces are free of stormwater accumulations, and will protect the public from unnecessary hazards associated with water ponding and sheet flow. Except where porous pavement is used, road pavement shall be sloped transversely to drain stormwater from the roadway. A minimum cross slope of 2 percent should be applied to all roads, both primary and secondary. Greater slope should be considered where poor drainage is anticipated. Drainage structures associated with medians, curbs, and gutters should be designed to minimize accumulation of water onto travel lanes of roadways. For additional information concerning drainage of highway pavements, refer to FHWA HEC No. 12. B. Curb and Gutter Curb and gutter at the edge of pavements may be used to collect stormwater runoff from roadways. Curbing captures stormwater runoff and directs it to stormwater collection inlets while protecting adjacent properties from flooding and erosion due to sheet flow runoff from the impervious roadways. A curb and gutter forms a triangular conveyance channel. When a storm occurs, the runoff from the road creates a spread of water from the curb. The curb and gutter must be designed to convey this flow and prevent the spread of water from impacting traffic. The spread width of flow is determined by using VDOT nomographs or acceptable hydrological COUNTY OF ROANOKE MARCH 22, 2016 7-3 STORM DRAINS STORM DRAINS CHAPTER 7 design software. For curb and gutter flow, a Manning's n value of 0.015 is used in the computational analysis. See Appendix 7A for width of maximum allowable spread. Curb and gutter dimensions and design shall meet VDOT Standards. C. Open Channels Open channels may be used to collect site drainage and convey it to a storm drain inlet. Design requirements for open channels are covered in Chapter 5. 7.2.5 Storm Drain Inlets A. General Storm drain inlets are used to collect stormwater runoff from roads, walks, or low elevations during storm events and provide a method for passing the stormwater into the storm drain system. This is usually accomplished by placing storm drain inlets at regular intervals, low points, or at key locations to intercept flows and control the stormwater spread width. The design criteria for limiting the spread of water on travel lanes are contained in the VDOT Drainage Manual. The current design table and its notes have been included in Appendix 7A There are several different types of storm drain inlets which can be used to meet this purpose, and the designer shall choose the proper inlet structure based upon site conditions and design conditions to maximize the drainage efficiencies. • Curb • Grate • Slotted Drain/Trench • Combination Drainage and Stormwater management plans shall include a contour plan with sufficient contours shown to indicate proper drainage. B. Curb Inlets Curb inlets are vertical openings in the curb covered by a top slab. These inlets can convey large quantities of water, but also allow for large amounts of debris to enter the storm drain system. COUNTY OF ROANOKE MARCH 22, 2016 7-4 STORM DRAINS STORM DRAINS CHAPTER 7 Curb inlets shall be used to the maximum extent possible for pavement drainage. C. Grate Inlets Grate inlets are horizontal grates usually used in depressed medians or other low elevations. Grate inlets are often referred to as drop inlets or DIs. Grate inlets shall be avoided in paved areas. Where they are used in pavement, inlet grates shall be bicycle safe. D. Combination Inlets Combination inlets combine both the vertical opening used by curb inlets and the horizontal grate used in grate inlets. These inlets are often used when the inlet chamber is required to be under the gutter or street pavement away from the sidewalk or other utilities. Combination inlets shall be avoided where possible. Where they are used, they shall have bicycle safe grates. E. Slotted Drain Inlets Slotted drain inlets are a narrow slotted opening which can collect flow at a median barrier or curb. These inlets are usually located in areas of limited space and can be used to intercept sheet flow, or collect gutter flow to help reduce ponding depth or spreading at grate inlets. F. Inlet Locations Inlets shall be located to meet the design requirements of the VDOT Drainage Manual for maximum spread width. In addition, inlets shall be provided, regardless of contributing drainage area as follows: • Sag points in the gutter grade; • Upstream of median breaks, crosswalks, and street intersections; • Immediately upstream and downstream of bridges; • On side streets at intersections, where flow is approaching the main line; • Behind curbs, shoulders, or sidewalks to drain low areas or intercept concentrated flow; and COUNTY OF ROANOKE MARCH 22, 2016 7-5 STORM DRAINS STORM DRAINS CHAPTER 7 • Any low elevation in the grade. Inlets shall be avoided in pathways likely to be used by pedestrians or bicyclists. G. Access All inlets shall have a removable grate or manhole cover to allow access for clean out. All structures greater than 3 feet in depth shall be a minimum of 4 feet in diameter for maintenance access. H. Inlet Capacities The capacities of each inlet type are contained in the VDOT Drainage Manual. Documentation of inlet capacity shall be made on VDOT Form LD -204, Stormwater Inlet Computations or equivalent. I. Separation of Pipes in Inlets Where two or more pipes enter a concrete structure at or near the same elevation, a 6" minimum horizontal clearance must be maintained between the pipes. Additional clearance between pipes shall be provided if required to protect the structural integrity of the structure. J. Karst Terrain Water tight joints are required where storm drainage pipe are located in karst terrain. Additionally, an A -lock premium gasket or boot is required for the pipe connection to the storm drainage structure to prevent water loss at the structure connection. 7.2.6 Storm Drain Pipes A. Flow Capacity Based on the size and slope of the storm drain, the design capacity for a pipe flowing full can be determined using Manning's equation. Q= A x 1.49/n x W/' x Sv2 Where: Q = Flow in the pipe (cfs) A = Area of the pipe (ft2) COUNTY OF ROANOKE MARCH 22, 2016 7-6 STORM DRAINS STORM DRAINS CHAPTER 7 R = Hydraulic radius, for circular pipe R=Diameter/4 (ft) S = Storm drain slope (ft/ft) n = Pipe roughness coefficient The design flow capacity of a storm drain shall comply with the design frequencies set forth in VDOT Drainage Manual as shown in the table in Appendix 7A. In a roadway underpass, or depressed section, where ponded water can only be removed through the storm drain system, a 100 - year frequency storm event shall be used to design the storm drain at the sag point. Storm drain flow capacities shall be documented on VDOT Form LD -229, Storm Drain Design Computations or equivalent form. B. Storm Drain Slope To deter the settling of debris and sediment in the storm drain pipe, the pipe shall be designed to ensure positive slope and maintain a minimum velocity of 3 feet per second during a 2 -year frequency storm or a minimum of 0.5% slope, whichever is more restrictive. A minimum drop across the structure of 0.1' shall be provided in all storm drainage structures. The maximum pipe velocity, based on the 10 -year peak flow rate, in any storm drain shall be in accordance with VDOT requirements based on the storm drain material, but in no event shall it be greater than 20 fps. Storm drains shall be sloped to meet the velocity requirement set in this chapter. Slopes greater than 16 percent shall be avoided if possible. If unavoidable, drop structures shall be utilized in steeper terrain. In addition, storm drains with slopes steeper than 16% must have anchor blocks for support. C. Pipe Size All storm drains located in public easements or rights-of-way shall be a minimum of 15 -inch diameter. Pipe size shall not be reduced along the direction of the flow, except as required for proper operation of stormwater management facilities. D. Access Regardless of pipe size, a cleanout access point, either an inlet, manhole, or junction box shall be provided at a maximum of every 300 feet of pipe. COUNTY OF ROANOKE MARCH 22, 2016 7-7 STORM DRAINS STORM DRAINS CHAPTER 7 Cleanouts can be used for pipes 6" and smaller. All pipes over 6" require an inlet or manhole. E. Joints At a minimum, all joints shall be "soil tight". The County strongly recommends the use of "water -tight" joints under pavements and areas that are stormwater "hotspots". "Water -tight" joints are required for karst terrain. See Section IV and corresponding ADS detail in Appendix 7B for additional info in water tight joints. 7.2.7 Determination of Hydraulic Grade Line A. General The hydraulic grade line represents the free water surface elevation of water in a pipe system. Where the hydraulic grade line is above the top of a pipe, the pipe is flowing under pressure. The hydraulic grade line in a manhole or other structure is the elevation to which water will rise. Hydraulic grade lines shall be calculated and evaluated for all storm drains. The hydraulic grade line shall be calculated using VDOT methods and equations that are fully described in the VDOT Drainage Manual. Calculations shall be documented on VDOT Form LD -347, Hydraulic Grade Line Computations, or equivalent. A copy of this form is included in Appendix 7A. Hydraulic grade lines can also be calculated with design software (ie Storm sewer, etc.) The hydraulic grade line shall not exceed any critical elevation during the design storm. Critical elevations include rising above the ground elevation at inlets or other structures, or reaching an elevation where storm flow could back-up to cause flooding damage. The calculation of the hydraulic grade line begins at the system outfall and proceeds upstream to each structure on the system. The calculation is based on the principal of conservation of energy as shown below and includes major and minor energy losses: HGLus = HGLds + Hf + H,,, Where: HGLus = Elevation of hydraulic grade line at the upstream structure H,,, = Summation of minor head losses (junctions, bends, etc.) Hf = Pipe friction loss COUNTY OF ROANOKE MARCH 22, 2016 7-8 STORM DRAINS STORM DRAINS CHAPTER 7 HGLas = Elevation of hydraulic grade line at the downstream structure Major head losses are attributable to friction losses within the pipe. Minor head losses include losses from: • Junctions • Exits • Entrances • Bends in Pipes • Access holes • Conflict pipes • Plunging flow Expansions and contractions Appurtenances such as weirs, diverters, valves and meters B. Outfall Conditions The hydraulic grade line starts at the system outfall. At this point the hydraulic grade line shall be the actual tailwater elevation or the elevation of 0.8 times the diameter of the outlet pipe, whichever is higher. If the system discharges into a detention or retention pond, the hydraulic grade shall start at the 10 year water surface elevation. C. Pipe Friction Losses The friction slope is the energy slope for that run of pipe. The friction slope is determined by inserting pipe information and design flow into Manning's equation and solving for S (slope). The total friction headloss in the run of pipe is the friction slope multiplied by the length of the run. Where the hydraulic grade line falls below the crown of the pipe, the elevation of normal flow is the hydraulic grade line. D. Junction Losses 1. General Junction head losses are the summation of entrance (Hi), exit (Ho), and bend losses (HA). When calculating junction losses it is important to use actual flow velocities. If pipes are flowing partially full, then partially full velocities are used. COUNTY OF ROANOKE MARCH 22, 2016 7-9 STORM DRAINS STORM DRAINS CHAPTER 7 2. Entrance (expansion) Losses Entrance loss at a junction is given by: Hi = Ki (Vi2 / 2g) Where: Hi= Entrance head loss Ki = Entrance loss coefficient. Ki = 0.35 Vi = Velocity in the inlet pipe. Where more than one inlet pipe is present, use the velocity from the pipe that has the greatest momentum (Q*V) g = Gravitational acceleration constant, 32.2 ft/s2 3. Exit (contraction) Losses Exit loss at a junction is given by: Ho = Ko (V 2 / 2g) Where: Ho = Exit head loss Ko = Exit loss coefficient. Ko = 0.25, except that Ko = 0.3 when computing the loss leaving the initial inlet Vo = Velocity in the outlet pipe. g = Gravitational acceleration constant, 32.2 ft/s2 4. Bend Losses Bend loss at a junction are dependent on the angle between the inlet and outlet pipes. If the inlet and outlet pipe are in line with one another no bend) the angle is 0 degrees and there is no bend loss. As the angle increases towards 90 degrees, the bend loss increases. Storm drain systems should not be designed with bend angles greater than 90 degrees. The bend loss is given by: Ho=K(Vi2/2g) Where: HA= Head loss at bend K = Bend loss coefficient. K is determined by consulting Figure 9-10 in the VDOT Drainage Manual. A copy is included in appendix 7A. Vi = Velocity in the inlet pipe. COUNTY OF ROANOKE MARCH 22, 2016 7-10 STORM DRAINS STORM DRAINS CHAPTER 7 g = Gravitational acceleration constant, 32.2 ft/s2 5. Plunging Losses Where surface inlet inflow is 20 percent or more of the total flow through a junction, or when a lateral pipe enters a junction with its invert elevation above the crown of the outgoing pipe and the flow in the lateral pipe is 20 percent or more of the total flow through the junction, the total headloss from the structure (Hi + Ho + Ho) shall be multiplied by 1.3 (increased by 30 percent). This adjustment is cumulative with the adjustment for inlet shaping. 6. Inlet Shaping Inlet shaping refers to how the invert is shaped to provide smooth flow through the structure and is required in all manholes and inlets. When VDOT Standard IS -1, inlet shaping, is used in a structure the total headloss from the structure A + Ho + Ho) shall be multiplied by 0.5 (decreased by 50 percent). This adjustment is cumulative with the adjustment for plunging losses. 7.2.8 100 -Year Conditions Where there is the possibility of building structures flooding, conditions during the 100 -year storm shall be analyzed to verify that all existing and proposed structures do not flood. Flow from the 100 -year storm may be carried overland as well as by the storm drain system. 7.2.9 Materials A. Structures • All stormwater structures (inlets, manholes, and junction boxes) located in public easements or rights-of-way shall be precast or cast -in- place concrete. All structures, frames, grates, and covers shall be in accordance with VDOT Standards and VDOT Specifications. • All storm drain structures over four (4) feet in depth must have steps. COUNTY OF ROANOKE MARCH 22, 2016 7-11 STORM DRAINS STORM DRAINS B. Storm Drain Pipe CHAPTER 7 • Storm drains in the VDOT right-of-way shall be VDOT approved materials in accordance with VDOT II1VI-LD-121.15 and VDOT Standard PC -1. • Storm drains not in the VDOT right -of way shall be: o Reinforced concrete pipe (RCP). o Corrugated high-density polyethylene pipe (HDPE) with an integrally formed smooth interior is allowed for sizes 48 -inch diameter or smaller. HDPE pipe is allowed for pipe slopes less than 12% and with a velocity 12 fps or less. HDPE culvert pipe cover must be in accordance with the County of Roanoke Inspection Specifications for HDPE Pipe. A copy of this document is included in Appendix 7B. o Culverts 60 inches in diameter or greater may be Corrugated Aluminized Metal Pipe (CAMP) or corrugated aluminum with a minimum 14 gauge metal. o The minimum cover for all pipes is two (2) feet measured from the final surface. Special applications for less than two (2) feet of cover will be reviewed and approved by the County Engineer individually. The maximum cover for storm drainage pipes shall at a minimum comply with the requirements of the Virginia Department of Transportation Design Manual. 7.2.10 Structural Design All inlet structures, frames and grates; and pipes shall be designed to withstand a HS -20 loading, unless a pipe crosses a railroad, in which case the pipe shall be designed for railroad loads. The structural design shall consider the depth of cover, trench width and condition, bedding type, backfill material, and compaction. 7.3 Installation All inlets, pipes, and associated structures shall be installed in accordance with VDOT Specifications and the manufacturer's recommendations. The characteristics of the trench, bedding, and pipe material all impact the structural strength of the pipe system. The installed pipe conditions shall comply with the design assumptions and calculations. COUNTY OF ROANOKE MARCH 22, 2016 7-12 STORM DRAINS STORM DRAINS CHAPTER 7 HDPE pipe installation shall comply with the County of Roanoke Inspection Specifications for HDPE Pipe. A copy of this document is included in Appendix 7B. Storm drains shall not be installed through contaminated soils or groundwater. 7.3.1 Bedding Material Bedding material and installation shall comply with the requirements of the VDOT Specifications. Use Class I backfill (crusher run and #21) to one foot over the pipe for HDPE, up to the spring line for RCP. #57 stone is not allowed as pipe bedding. 7.3.2 Backfill Backfill shall be suitable material and shall be placed and compacted in accordance with the VDOT Specifications (PB -1 detail). Use Class I backfill (crusher run) to one foot over the pipe for HDPE, and up to the spring line for RCP. The minimum cover for all pipes is two (2) feet measured from the final surface. Special applications for less than two (2) feet of cover will be reviewed and approved by the County Engineer individually. Additional minimum depth of cover shall be provided if recommended by the manufacturer. All pipe installed must be inspected and approved by the County's Inspector prior to any backfill being placed. The Contractor must provide 24 hour notice to County prior to installing backfill so that County staff can be present for inspections. 7.3.3 Separation of Utilities Where storm drains cross other utilities, at least 1 -foot of vertical separation shall be provided. Where 1 -foot of vertical separation cannot be provided, special provisions shall be made in the bedding and backfill to avoid settlement that could cause point loadings on the storm drain or other utility. Water lines shall not pass through a storm drain inlet or manhole. 7.4 Environmental Impacts Construction or modifications to storm drains shall comply with all applicable laws and regulations. The applicant is responsible for procuring all necessary permits. COUNTY OF ROANOKE MARCH 22, 2016 7-13 STORM DRAINS STORM DRAINS 7.5 Erosion Protection at Outfalls CHAPTER 7 Erosion protection at storm drain outlets shall be provided in accordance with the outlet protection standards contained in the VA E&SC Handbook and the VDOT Drainage Manual. 7.6 Maintenance Requirements The permittee is responsible for maintenance of storm drains until construction is complete, including final clean up and site stabilization, to the satisfaction of the County. COUNTY OF ROANOKE MARCH 22, 2016 7-14 STORM DRAINS STORM DRAINS APPENDIX 7A AIDS FOR STORM DRAIN SYSTEM DESIGN FROM CHAPTER 9, VDOT DRAINAGE MANUAL Table 9-1, Criteria for Inlet Design Table 9-2, Design Frequencies for Storm Drain Conduit Notes that accompany Table 9-1 and Table 9-2 Figure 9-10, Losses in Junction due to Change in Direction of Flow Lateral Appendix 9B-1, LD 204 Stormwater Inlet Computations Appendix 9B-2, LD 229 Storm Drain Design Computations Appendix 9B-3, LD 347 Hydraulic Grade Line Computations Appendix 9C-1, Flow in Triangular Gutter Sections Appendix 9C-3, Flow Characteristic Curves (24" Gutter)- VDOT Standard Appendix 9C-23, Manning's Solution for Flow in Storm Drains APPENDIX 7A Appendix 9C-24, Nomograph for Computing Required Size of Circular Drain for Full Flow Appendix 9C-25, Concrete Pipe Flow Nomograph COUNTY OF ROANOKE MARCH 22, 2016 7A-1 STORM DRAINS STORM DRAINS CRITERIA FOR INLET DESIGN APPENDIX 7A DESIGN FREQUENCIES FOR STORM DRAIN CONDUIT Roadway Classification y Design Speed Design Storm Maximum Design Roadway (mph) S read Width p Frequency Intensity Classification With or Without Shoulder All 10 (yea 1,2) in/hour (ft) Principal Arterial <50 10 Actual Sh. Width +3 On Grade>50 10 Actual Sh. Width 3 Sag 10 Actual Sh. Width +3 Locations All On Grade <50 N/A4 4 '/2 Driving Lane + Gutter — Width (If Any) On Grades >50 10 Actual '/2 Driving Lane + Gutter Width (If Any) o <50 N/A' 4 '/2 Driving Lane + Gutter Sag — Width (If Any) 3 Locations >50 50 Actual '/2 Driving Lane + Gutter Width (If Any) Minor Arterial, Collector, Local On Grade <50 N/A4 4 Sh. Width +3 >50 N/A4 4 Sh. Width Sag N/A4 4 Sh. Width +3 Location All On Grade All N/A4 4 '/2 Driving Lane + Gutter o 7� Width (If Any) Sag N/A4 4 Drivin Lane + Gutter '/2 g Location All Width (If Any) DESIGN FREQUENCIES FOR STORM DRAIN CONDUIT Roadway Classification y Design Speed (mph) Design Storm Frequency (year 1,2) Principal Arterial With Shoulder All 25 Without Shoulder 50 10 < <50 25 Minor Arterial, Collector, Local With or Without Shoulder All 10 COUNTY OF ROANOKE MARCH 22, 2016 7A-2 STORM DRAINS STORM DRAINS APPENDIX 7A NOTES - CRITERIA FOR INLET DESIGN AND DESIGN FREQUENCIES FOR STORM DRAIN CONDUIT Notes I through 3 are General Notes and should be applied to any functional classification roadway where the site conditions are comparable to the conditions described in each note. 1 At locations where the vertical alignment of the roadway creates a sag condition in either a depressed roadway section or a roadway section utilizing concrete barriers, and ponded water on the roadway can only be removed through the storm drain system, a 50 -year storm frequency and the actual time of concentration should be used as the design criteria for both the drop inlet and the pipe system. 2 Federal Flood Insurance criteria dictate that the effects of the 100 -year storm event (using the actual time of concentration) on buildings insured under the Flood Insurance Program must be investigated. Such cases should only be encountered where the roadway traverses a designated floodplain area containing insured buildings and the depth of water on the pavement is sufficient to overtop the curb and flow to the buildings. s The maximum design spread width may not be obtainable due to the pavement/shoulder slope and the height of the curb. In locations where the curb would be overtopped and water would escape the roadway section prior to achieving the maximum design spread with, the maximum depth of ponded water allowed adjacent to the curb for the design storm shall be curb height minus one (1) inch. Notes 4 through 5 should normally be applied to the specific locations as noted in the criteria table. 4 At location where it may be reasonably anticipated that the runoff from storm events with rainfall intensities greater than 4 inches per hour will overtax the drop inlet system to the point that excess flow will escape the roadway section and result in potential damage to the adjacent property and/or roadway right of way, the drop inlet system shall be analyzed for a check storm event with a rainfall intensity of 6.5 inches per hour. If all of the runoff from the check storm event is found to be contained within the roadway section, both at the site and down grade, or if runoff escaping the roadway section is found to not be damaging to adjacent property, the drop inlet system may be used as originally designed under the general criteria. If the drop inlet system fails to meet the check storm criteria, it must be re -designed to accommodate the runoff from the check storm event. 5 Drop inlets in these locations are prone to clogging and are often located in areas where maintenance is difficult. To compensate for partial clogging, the computed slot length value should be adjusted by multiplying by a factor of two (2). The adjusted computed slot length value should then be used to determine the slot length specified on the plans. COUNTY OF ROANOKE MARCH 22, 2016 7A-3 STORM DRAINS STORM DRAINS APPENDIX 7A LOSSES IN JUNCTION DUE TO CHANGE IN DIRECTION OF FLOW LATERAL t Yom, Joon, HL= K V, = Vel of flnw in lateral in f.p_s_ g AcciBleralloa due to gmvlty, 32 It,'seolsec HL= FtM of head lest in Jct, due to change in dlriocWri of lateral love K Factor frnm graph m 60 40 CID gad 00 0-1 0.2 Q-3 0-4 ()'-5 0'A 0.7 Factor COUNTY OF ROANOKE MARCH 22, 2016 7A-4 STORM DRAINS STORM DRAINS APPENDIX 7A STORMWATER INLET COMPUTATIONS (VDOT LD -204) COUNTY OF ROANOKE MARCH 22, 2016 7A-5 STORM DRAINS �ellllllellllll� 1111111111111111 �����iiiiiiiii■��' �■I�11�1111�11�1 COUNTY OF ROANOKE MARCH 22, 2016 7A-5 STORM DRAINS STORM DRAINS APPENDIX 7A STORM DRAIN DESIGN COMPUTATIONS (VDOT LD -229) O O N cm CV j J x a { � W � J — LLr w 7 a �y a i- � U � * 8 ; f ' W 6 4 J W t � � F � Z b � W k N � x IC W O ia� � g r u r a # � } C 1 � o E � m ; J K i fC a 6 S $ �'W b J � Z W r 3 3 � � F _ u � n a i3 w r rc x u w x � LL � LL ss � 4 m w d ❑ { 4 U 2 � r A a � O 4 COUNTY OF ROANOKE MARCH 22, 2016 7A-6 STORM DRAINS STORM DRAINS APPENDIX 7A HYDRAULIC GRADE LINE COMPUTATIONS (VDOT LD -347) t b W IL 4 i+1 f � c lF L! 9? r r r � � r n 0 j M � r r r y� 1 J -gpU vi I-- W M -j r Z w a f+ co €9 N 'sI rr1 CV N i3 1D O 0 I II lF II ]E Y gY p�C L O I19 M N 9W G 963 r L0 M1 w ap 47 C 4= G O tl h II II "se Y *y SL O ,J A COUNTY OF ROANOKE MARCH 22, 2016 7A-7 STORM DRAINS STORM DRAINS APPENDIX 7A FLOW IN TRIANGULAR GUTTER SECTIONS PQj 006 0,05. z -0.94 E XAMPtE' GIVEN' nz- fir; a,° ?.b3 h t S-Lb#04 ; 7 =-6 Fr 0,5 1"IW, 4 ID 4 ;rT 3j S y Qty z G.03$ +.4 T(rT) -0.002 + L.00I T T + L � � j ow Q ! 1-67 05 T2.67 n E XAMPtE' GIVEN' nz- fir; a,° ?.b3 S-Lb#04 ; 7 =-6 Fr 0,5 1"IW, 4 ID 4 ;rT 3j S Qty z G.03$ +.4 T(rT) 3 0. E (V V�G 3 2.QO % ski 5 ASKI Ski 2) To alarm€ o discharge in gutter w np454 =83 e*pec firrd Qs ars n; T, and 8*, Thea, us* App. 9G.a tD find Eo. lotal dis0args Is COUNTY OF ROANOKE MARCH 22, 2016 7A-8 STORM DRAINS AlldplPF.FF,g lllp"wWAMMWWO J�w�inr�.v•�ra-rr ■uraaraa.-■ rr�- I R'xr■UllIn■!1R�r��lI ■/flElm PIP VLP::sss ll�■� 1 1 �l■■ 111:::3 STORM DRAINS APPENDIX 7A MANNING'S SOLUTION FOR FLOW IN STORM DRAINS 2400 20 co — H500 Goo Goo t0a 40-0 100 00 y so 50 40 :56 w 61 Zc) 6 W Lh- 4 ria � z Q 240 1810 t04 84 72 CD40 54 448 42 F �6 10 Z4 I� ` 45 ,a - 6 4 cr 0.5 r.—. .4 0.5 0.2 0.7 L E 0.9, 0. ria CL 2 0.06 1.0 0.04 W CL 0.0001 T o 0.00006 z 0,0004 a 00 0 0. 06 L + w CL 04; 0. Qz 0. loz C_0� 0,006 ' us 31 0.5 r.—. .4 0.5 0.2 0.7 L E 0.9, 0. ria CL 2 0.06 1.0 0.04 a_ oz 15 r0. 0 00004 4� COUNTY OF ROANOKE MARCH 22, 2016 7A-10 STORM DRAINS E w�" 4 & 0.0001 T o 0.00006 0,0004 0 13.00002 15 r0. 0 00004 4� COUNTY OF ROANOKE MARCH 22, 2016 7A-10 STORM DRAINS STORM DRAINS APPENDIX 7A NOMOGRAPH FOR COMPUTING REQUIRED SIZE OF CIRCULAR DRAIN FOR FULL FLOW F-1000 F 000 acd0 700 000 0Q 300 140 90 +} -50 0 7a] Ao LTJ Z tj Y'1 GI J20 106 06 90 64 7s 72 1ftl 46 do 43 Z .42 30 36 Z7 � 24 14 IG W is T 12 6 � a s/ope of 0-00603 xf- 7roo;r. lociiyr of .3..5 {'Ret- Secoocy. by irollow&7-9 doshec� 11;7e MCI .0001 .00cz .0003 zooz ,0000 .0093 ,0006 4004 r x Doe 06 6 { .0410 .0$08 fn � Ji74710 II .OG�O Cc. 0020 .Q04.0+]ZA LA 040 -0030 Cc I� LJ A06{T40 x0`909 OIOO ,0480 Ld J .005$ I1 -f .ol oc A�zoo SA moo ozoo A4A0 ,000 *-A44ii 1Q�g0 4600 J0600 J10 0 .0800 .1000 i IS 2 COUNTY OF ROANOKE MARCH 22, 2016 7A-11 STORM DRAINS STORM DRAINS APPENDIX 7A CONCRETE PIPE FLOW NOMOGRAPH -Ba cl CI'Q�1 r - 'c° F- 0 _ .00 0 .0003 400 ,tea 50 445 .o0 Cs. 300 -00(m -9 rp $ t} O -001 w- wi T2 +� ++F 4 .i- c n ez 4rAb 200 � 4 CL 4 � �-003T T sry as ora `� 300 EVO 00 4a C31-- a N-' r 7rJ d= 3$ .woe Soo lL1 0j 4:1 uJ O —j .OZ 1 #' F AX Lu # ,03 IBJ 2 Cf bc � Q -a A 18 � ,1:}5 W 73 i #Ga77COO C3 .Od 20 14 -j 1 Jo } 1 5 4000 Y 1� to �00c G 9 {] 91c?o 7" 7 KxxeKs.LEE: q cf1i Las 4 50, 5 �5 SOLUTION-' Prneerd lramt the Inti, rmad ta, = ZI Cls and D = 27" Pstord St=-CQ5 and Va!,.3 fR!F- Renc1 V=fx3 fps Ond Le# 1: a5 PeCord at, 0 L4 mirk COUNTY OF ROANOKE MARCH 22, 2016 7A-12 STORM DRAINS STORM DRAINS APPENDIX 7B INSTALLATION PROCEDURES FROM ROANOKE COUNTY Inspection Specifications for HDPE PIPE APPENDIX 7B COUNTY OF ROANOKE MARCH 22, 2016 713-1 STORM DRAINS STORM DRAINS INSPECTION SP CIMA`I'IONS FOR HDPE PIPE TABLE OF CONTENTS I, Overview II. Pre-lnstaUatian a. 'French Widths h. Dewatering Ill. Embedment a. Definitions h. Foundation c, Bedding d. Hhunching e. hiitial Backfill f. Final Backfill . Joints V. Typical Details APPENDIX 7B COUNTY OF ROANOKE MARCH 22, 2016 713-2 STORM DRAINS STORM DRAINS I. OVERVIEW APPENDIX 7B The County of Roanoke, in conjunction with the Vi-rginia Department of Transportation, is allowing HDPE pipe for storm. sewers. HDPE pipe may be used for any size lip to 48" in diameter. Anything above that must use previously approvers pipe material. 11. PRE -INSTALLATION A. Trench Widths Trench widths used in installing HDPE pipe have been established in AASHTO Section iii and. ASTM D2321. Table 1 provides the recommended trench widths for most installations to provide the proper placement and compaction of backfill material in the haunches around the pipe. Trenching should be completed in the existing soils with sidealls reasonably vertical to the top of the pipe. When excavation depths or soil conditions require shoring or use of a trench box, the bottom of the shoring or trench box should be placed no lower than the top of the pipe. This prevents disruption of the backfill when shoring of trench box is removed. If this practice cannot be followed, considerations should be given to leaving the shozing in place. Refer to Fable 1. TAI3LF-1 - SUGGESTEt) MINIMUM TRENGH WIDTHS Nominal P# a Diameter, (in) Pipe OD in Minimum Trench Width (in) 4 4.75 21 5 6.92 23 S 9.11 25 in 11-36 28 12 14.45 31 16 17..57 34 is 21.2 39 24 27.8 48 30 36,1 66 36 411 78 42 47.7 83 48 �a2.79 COUNTY OF ROANOKE MARCH 22, 2016 713-3 STORM DRAINS STORM DRAINS B. Dewatering APPENDIX 7B HDPE pipe will float in standing water. Thercfore, it is bnperative that the trench be dry when installing the pipe, Su np pumps, well paints, or other methods may be needed to insure a &y trtneh.. N_! -r o EMBEDMENT 3 Embedment materials are those used for the foundation, bedding, haunching, and initial backfill. An illustration of this can be found in Figure I page 5. A. Def .tions 1. Class I — Angular c.mxshed stone or rock (No. 25 or 26 stone). . Class. 11— Clean, course grained materials, such as gravel, course sands, and gravel/sand mixtures. 3. Class III — Course grained materials with des including silty or clayey gravels or sands. Gravel or sand must comprise mare than 50% of Class III materials. 4. Class IV and 'V materials are not recommended for embedrrzent materials. B. Foundation A. stable foundation must be provided in order to insure proper installation. Unsuitable or unstable foimdatlons maybe replaced with a suitable bedding material, placed in 6" lifts, COUNTY OF ROANOKE MARCH 22, 2016 713-4 STORM DRAINS STORM DRAINS C. Bedding; APPENDIX 7B 4 The middle of the bedding, equal to 1/3 of the pipe outside diameter, should be loosely placed. The rmining stone for the bedding should be ccYnpacted to a rninimum 90% standard proctor density. Class 1 stare will be acceptable teztal for use, except when the foLmdation is in soft, yielding, or otherwise unsuitable material. Then, the bedding material shall be #57 stone for the specifred depth, and then. capped with 4" of Class I stone. D. Haunching Haunebing provides the pipe with its main support and strength. Extra care must be taken in installing tha haun,ching. The haunching will extend frorn the bottom of the pipe up to the spring line. For larger diameter pipes (30"- 48"), embedment materials should be worked in by hand. Class l stone may be used and compacted in " maximum lifts, compacted to 90% standard proctor density. F. Initial Backfill hidtial Backfill will extend from the spring lime to 12" above the top of the pipe. The backfill material S'ha.11 consist of Class I stone, compacted in 6" lifts, compacted to 90% standard proctor density. F- Final Backfill Final back fill should be the same material as the proposed embardcent. Oerierally, the excavated material will be used for the fnal backfill. The final backffll is to be placed in 12"' maximum lifts, compacted to a minimum 8 5 °fa standaxd proctor compaction. COUNTY OF ROANOKE MARCH 22, 2016 713-5 STORM DRAINS STORM DRAINS Haunc Bod APPENDIX 7B Figure 1 Trench Crok's sectun Excavated `f reach Width Pipe Zone Haunch Zone COUNTY OF ROANOKE MARCH 22, 2016 713-6 STORM DRAINS STORM DRAINS APPENDIX 7B 6 IV, JOINTS For watertight joints, an ASTM F-477 elastameric rubber gasket shall be used at all joints of pipe. To install this gasket, the ends of the two pipes being connected shall be cleaned. The gasket shall be applied onto the bell with, the marling facing the coupler. Apply lubricant liberally to both joints of the pipes. Align the pipe to push it together on grade. Generally, pipe should be laid From the downstream end and working upstream. Small diameter pies (>24") can be pushed together by hand. larger diameter pipes may need to use a. bar or equipment to push the pipe together, If that is used, a wood block should be used to prevent any damage to the bell of the pipe. Special care should be taken to ensure that no bedding material gets into the joints. Stone or any other material that gets into the joint may cause leaks. Rubber gaskets are normally installed at the -Factory. However, if a pipe needs to be cut in the field, the gasket shall be stretched over the bell prior to connecting pipes together. COUNTY OF ROANOKE MARCH 22, 2016 713-7 STORM DRAINS STORM DRAINS TYPICAL DETAILS 0110 1 c DOT TABLES AND DETAILS APPENDIX 7B COUNTY OF ROANOKE MARCH 22, 2016 713-8 STORM DRAINS STORM DRAINS APPENDIX 7B { R COUNTY OF ROANOKE MARCH 22, 2016 713-9 STORM DRAINS STORM DRAINS APPENDIX 7B COUNTY OF ROANOKE MARCH 22, 2016 713-10 STORM DRAINS � r� � p jD;6 w F,r a t +� 0 § i J z Q 0 ¢m BR KAup • ' • S gica Lf w 3E LU u) -Z p< f d; o p Ld � a Ta w� p lipFv@C� _._._._......----....._-----'----- 7 S Z M3 .iC � j 91Wh V r COUNTY OF ROANOKE MARCH 22, 2016 713-10 STORM DRAINS STORM DRAINS APPENDIX 7B z a a= ?� n p Tm 4 W �� Q NNW M1 �gFNN,',"y Xp-01 FJNy¢ N� W �N1 u1 Do;; 50 (Q N? N UUiII L]q d a NNNNM7 0401 A97�� 4 47a= � GN2�C7 4� 1 d2� �Z2� �N a � pJ� m p�p ~p m �p N pp M1M1 oo W49 �= p LD ��QpIn AVOprMNHMn�mfN0 Z0��0.r j O 722p SrJ G5� V 65¢ 41Om 4ev OO NnP�o •• �Zw CC vHM d N7d �r�j I.- LL� q.M11 33 Ld SI7C 0 Q s W ~ Q im s - k a �S IRE im RE p'- gjgjp q a� N6 BIR _ pgimp COUNTY OF ROANOKE MARCH 22, 2016 713-11 STORM DRAINS EQ a rL OL a (� JN1WWf �y G ' It _ _ dd U a a I u a Q im s - k a �S IRE im RE p'- gjgjp q a� N6 BIR _ pgimp COUNTY OF ROANOKE MARCH 22, 2016 713-11 STORM DRAINS STORM DRAINS U 4 m LLJ ®� CC 4ry��mmm �J L LJ rr Lu LID t O '.3 U 0-11 L) Ul - j LLJ :E M'1 � 'A .. U $Sp � �• C6 {WY rk- W �] �. � 6J� 1 .-i � Lh f F'• 6ri ryw iL � W D- Ty In ❑ 3 i D ¢ U a Fl C7 LLJ al r• �G c ¢ N R _ •2 L!u YL - W W U 4 V1 m LLJ ®� CC 4ry��mmm LJ rr Lu O '.3 U 0-11 L) Ul w• fY M'1 � 'A .. U $Sp � �• C6 {WY W �] U z S K iL I-- W D- V1 m a ®� U $Sp � �• C6 {WY U z xc K O I-- W D- Ty In ❑ 3 i z U a LLJ al �G c ¢ N R _ •2 L!u YL - W W cy- � ® 14 s A M N Nl n w ox �c F v"t c u0 z'a. Lo G 44 SLA$ �W4 F dC7 APPENDIX 7B W 0. 11 f7 1-• Ln J IL y Is M U 0 LLJ LLJ a L) 1 LL W W J [� ry LLJ L) COUNTY OF ROANOKE MARCH 22, 2016 713-12 STORM DRAINS a ®� U $Sp � �• C6 {WY " xc K O I-- W D- ❑ 3 U a al �G ¢ N R _ •2 L!u YL - W W may$ � ® y yggrr $ 6 W Lm Yt ..JAW $ IA 2 L�¢p w ox �c F v"t c u0 z'a. Lo G 44 SLA$ �W4 F dC7 W 0. 11 f7 1-• Ln J IL y Is M U 0 LLJ LLJ a L) 1 LL W W J [� ry LLJ L) COUNTY OF ROANOKE MARCH 22, 2016 713-12 STORM DRAINS STORM DRAINS APPENDIX 7B COUNTY OF ROANOKE MARCH 22, 2016 713-13 STORM DRAINS �sOLL �II Ali f i.- I 3 no 00 111�k��� [S �z+C yy Ia� Ly t J� i}d i�Li Ilii t� mak`k2 tz Z a r- yr fn Z COO m6 FZ t n l i, ii� [ W dd Erle min 3-� W 0� it n '%` � H}lff W1 t5i {SIJ e r 6 ai' 11a l iIrij 4LL 0 Ln [3 po .! L o� Sam o -,,L7.F-. <��, 4 Ld.� LLJ y�� m cL ILLJ L` J IL 1 - a ilii 4• 43 V o o �� oWZL- 4A � r i� Ld tel, n � ;�� N � 3nN� x a v A R� o a. zi cti' ! � 9 c' W Wd sa IL 4x* - eP [1 {W m Wfi� — d_71 2 1 2 O W W Ldzo W 4 N l CS L 4l v pp ryL/ 6.Ww }L i LL 3 a = is 5 rWS LL a z 8 r. t+ X a ff oa g oaml J Z 3 4 sht3 w ra L ej COUNTY OF ROANOKE MARCH 22, 2016 713-13 STORM DRAINS RESIDENTIAL LOT DRAINAGE Chapter 8 - Residential Lot Drainage CHAPTER 8 Residential lot drainage for residential lots that are part of a common plan of development includes providing drainage and/or grading of the land to direct surface drainage away from building and toward streets, drainage conveyance structures, BMPs, or sheet flow. 8.1 References Except where more stringent requirements are presented in this Design Manual, lot drainage shall comply with state requirements. The primary design references are: • VDOT Drainage Manual • VA SWM Handbook • VA ESC Handbook • BMP Clearinghouse • State Building Code 8.2 General Lot Grading Lot grading plans establish the grading relationships between adjacent properties, determine the drainage areas and sizing of stormwater conveyance systems and BMPs, and account for the build out of the developed lot. 8.3 Construction Plan Requirements Individual lot grading and drainage shall be shown on the site plans and shall include the following information: • All high or low points shall be labeled on the plans. • All impervious areas shall be shown on the site plans. Additionally, all impervious areas shall be shown on the plot plans and shall not exceed the impervious areas shown on the approved site plans. Building pads sizes shall be noted on the site plans and the plot plans. If plot plans show an increase in the impervious areas then additional stormwater BMPs and a redesigned site plan may be required. Designers are encouraged to provide an adequate building pad on the site plans in order to meet homebuilders desired pad size and prevent redesign of the plans. COUNTY OF ROANOKE MARCH 22, 2016 8-1 RESIDENTIAL LOT DRAINAGE RESIDENTIAL LOT DRAINAGE CHAPTER 8 • Proposed and existing contours at two foot intervals. The proposed contours on plot plans shall conform with the intent of the approved site plan". • All stormwater conveyance structures (drainage pipes, swales, etc.) shall be shown on the plans. • All BMPs and swales shall be shown on the plans. • A finished floor elevation (FFE) shall be provided for each building pad on the site plan to the nearest foot. The plot plan shall show a FFE that is consistent with the intent of the approved site plan. See Section 12.2 for lots that are located in a floodplain. • Roof drains shall be shown on plot plans and shall meet the drainage areas as shown on the approved site plan. Rooftop disconnects used for stormwater quality shall be shown on the site plan. • Plot plans shall show that grading is consistent with the approved site plan. If plot plans is not consistent with the approved site plan then additional stormwater structures and a redesigned plan may be required. • Residential lots that are not part of a common plan of development may require residential lot grading at the discretion of Roanoke County due to the need of SWM plans, drainage issues, or other circumstances. • Residential driveways shall meet VDOT specifications for driveways abutting a public roadway and Roanoke County's Street standards for driveways abutting a private roadway for maximum driveway grades. COUNTY OF ROANOKE MARCH 22, 2016 8-2 RESIDENTIAL LOT DRAINAGE STORMWATER DETENTION Chapter 9 — Stormwater Detention CHAPTER 9 Stormwater detention facilities are a means of attenuating increases in peak flows caused by land development. In addition to providing flood control, stormwater detention facilities can protect downstream channels from increases in erosion. This chapter addresses general requirements for detention facilities as they relate to attenuating peak flows. When a storm event occurs, stormwater runoff enters the detention facility. The outlet structure allows a portion of the stormwater runoff to discharge from the facility and the remainder of the stormwater runoff is temporarily stored. After the end of the storm, water continues to discharge from the facility until it is empty. Stormwater detention facilities include: • Detention Basin • Retention Basin • Extended Detention Basin • Enhanced Extended Detention Basin • Underground Detention A detention basin is a pond that is normally dry. When a storm event occurs, it temporarily stores stormwater runoff, discharging it at a controlled rate through a hydraulic outlet structure to a downstream conveyance system. A retention basin is a stormwater pond which includes a permanent pool, even during non - rainfall periods. The pond includes storage above the normal pool elevation which temporarily stores stormwater runoff during storm events. An extended detention basin is a pond which temporarily stores runoff for a specific time period following a storm event, discharging it at a controlled rate through a hydraulic outlet structure to a downstream conveyance system. An extended detention basin is dry during non -rainfall periods. An extended detention basin provides more protection to the downstream channel from increases in erosion than a detention basin by releasing stored runoff at a lower rate over a longer time period. A typical plan and profile for an extended detention basin are detailed in the VA BMP Clearinghouse. An enhanced extended detention basin is similar to an extended detention basin, but it also incorporates a shallow marsh in its bottom. An underground detention facility consists of pipes or manufactured underground chambers used to temporarily store stormwater runoff following a storm event, discharging it at a controlled rate through a hydraulic outlet structure to a downstream conveyance system. An underground detention facility is dry during non -rainfall periods. COUNTY OF ROANOKE MARCH 22, 2016 9-1 STORMWATER DETENTION STORMWATER DETENTION CHAPTER 9 In addition to detention and retention basins, the design requirements specified by this chapter and the VA BMP Clearinghouse shall apply to ponds created as private property amenity features. 9.1 References Except where more stringent requirements are presented in this Manual, the design and construction of stormwater detention facilities shall comply with VDOT and VA BMP Clearinghouse requirements. The primary design references are: • VA SWM Handbook • VDOT Drainage Manual • VA E&SC Handbook • VDOT Standards • VA BMP Clearinghouse 9.2 Design Methodology and Criteria 9.2.1 Hydrology See Chapter 4 for methodology used to determine design flows. 9.2.2 Design Flows and Storage Volumes To properly design stormwater detention facilities, a flow routing program shall be used with an appropriate elevation — discharge - storage relationship for the design storm events. 9.2.3 Minimum Contributing Drainage Area A stormwater retention basin, which contains a permanent pool, requires at least 10 acres of watershed drainage and/or a good source of base flow to maintain the permanent pool. A minimum drainage area of 20 acres shall be used when the basin is located in an area of high visibility to prevent unsightly drying of the permanent pool. Retention basins are best suited for regional and large drainage area projects. COUNTY OF ROANOKE MARCH 22, 2016 9-2 STORMWATER DETENTION STORMWATER DETENTION CHAPTER 9 9.2.4 Detention Facility Locations Stormwater detention facilities should not be constructed within a Federal Emergency Management Agency (FEMA) designated 100 -year floodplain. If this is unavoidable, the facility shall comply with all applicable regulations under the National Flood Insurance Program, 44 CFR Part 59. The following factors shall be addressed when siting a stormwater detention facility: • Geotechnical conditions including soil conditions; • Groundwater levels and it's potential impacts; • Karst topography; • Existing and proposed utilities; • Aesthetics on surrounding properties; and • Environmental impacts including wetlands. Stormwater basins shall be located to minimize the aesthetic impacts to the surrounding property. Basins shall be set back from property lines a distance equal to the minimum width of the applicable required buffer yard. Locate stormwater detention facilities to avoid collecting significant amounts of drainage from offsite areas. Stormwater basins shall be set back at least fifty feet from a residential dwelling structure as measured from the wall of the structure to the top of the basin embankment. In proposed single family residential subdivisions, the stormwater management facility shall be located in a single non-developed lot. 9.2.5 Basin Grading Stormwater basins shall be graded to blend into the surrounding topography with the following conditions: • Basin side slopes shall be no greater than 3: L • Provisions shall be made for the long-term maintenance of basin slopes and periodic access for maintenance of the outlet structure, emergency spillway, and removal of accumulated sediments. COUNTY OF ROANOKE MARCH 22, 2016 9-3 STORMWATER DETENTION STORMWATER DETENTION CHAPTER 9 • The maximum allowable depth of a stormwater detention basin shall be 15 feet, as measured from the top of the embankment to the lowest point in a basin. • The bottom of the basin shall have a low flow or pilot channel to facilitate complete drainage. The pilot channel shall convey flows from a 2 year storm event and prevent standing water during dry -weather conditions. The pilot channel shall be sloped a minimum of 2% if it is a grass -lined channel and at a minimum of 1% if concrete -lined. In addition to the above requirements, the follow standards of practice should be used when designing a stormwater basin to the extent possible: • The length -to -width ratio of a stormwater basin should be a minimum of 2:1. A 3:1 ratio is desired where possible. This prevents short-circuiting of the basin's storage areas. • To minimize cut and fill, the long dimension of a stormwater basin should run parallel to the contours. 9.2.6 Embankments and Emergency Spillways Stormwater basin earthen embankments shall be designed and constructed to maintain structural integrity during the 100 -year frequency storm event. When applicable, Virginia Dam Safety regulations shall apply. The minimum top width of an embankment shall be 10 feet. Width may be greater based on the overall height. Embankment side slopes shall be no steeper than 3:1. Embankments with an emergency spillway must provide at least one foot of freeboard from the maximum 100 year storm water surface elevation to the top of the embankment. An embankment without an emergency spillway must provide at least two feet of freeboard from the maximum 100 year storm water surface elevation to the top of the embankment. A geotechnical study shall be required for all stormwater basins with constructed embankments greater than 6 feet in height as measured from the base of the embankment. The geotechnical study shall be performed by a licensed geotechnical engineer or licensed geologist and the report submitted to the County. COUNTY OF ROANOKE MARCH 22, 2016 9-4 STORMWATER DETENTION STORMWATER DETENTION CHAPTER 9 9.2.7 Outlet Structures and Release Rates A. Stormwater Release Rates Stormwater detention facilities shall be designed with an outlet structure to control the release rate from stormwater being held in the facility. Design release rates shall meet the requirements set forth in Chapter 4, except that extended detention facilities shall be designed based on releasing the design storm runoff volume in a prescribed time as indicated in the VA BMP Clearinghouse. All stormwater detention facilities shall be empty within 72 hours following the storm event. Ponds created as private property amenity features, not being used as stormwater management, shall be exempt from release rate requirements. B. Outlet Structure Criteria Outlet structures generally include a principal spillway or outlet and an emergency overflow. An outlet structure may take the form of a drop inlet, pipe, weir, or orifice. The principal spillway or outlet is intended to release flow from the design storm events at the necessary controlled rate, without allowing flow to enter the emergency spillway or overflow. The sizing of the outlet structure shall be based on the results of the hydrologic routing calculations or model. Outlets from stormwater detention facilities shall be designed to function without manual, electrical, or mechanical controls. Where necessary, energy dissipaters shall be placed at the outfall to provide a non-erosive velocity from the facility to a channel. See Chapter 10 for the design of outfall protection. The principal spillway is intended to convey the design storm without allowing flow to enter an emergency outlet. If site restrictions prevent the use of an emergency spillway, then the principal spillway should be sized to safely pass the 100 -year design storm without overtopping the facility. The designer should consider partial clogging (50%) of the principal spillway during the 100 -year design storm to ensure the facility would not be overtopped. For large storage facilities, selecting a flood magnitude for sizing the emergency outlet should be consistent with the potential threat to downstream life and property if the basin embankment were to fail. The minimum flood to be used to size the emergency spillway is the 100 -year COUNTY OF ROANOKE MARCH 22, 2016 9-5 STORMWATER DETENTION STORMWATER DETENTION CHAPTER 9 design storm flood. The sizing of a particular outlet structure should be based on results of hydrologic routing and calculations. When the primary spillway is less than 24 inches wide, it is considered inoperative during a 100 -year frequency storm. Where a stormwater basin with an earthen embankment has an emergency spillway included, two conditions should be evaluated. The routed 100 - year WSEL should provide one foot of freeboard between the 100 -yr WSEL and the top of the berm. Secondly, the spillway should be evaluated to show that the 100 -year flow passes through the spillway without overtopping the berm. Both conditions should be evaluated and met. The ability to pass the 100 -year flow through the spillway is typically evaluated by routing the flow through the spillway only with all other outlets ignored or by simply evaluating the 100 -year flow through the dimensional equivalent weir using F1owMaster, similar software, or applicable weir equations. Where a stormwater basin with an earthen embankment does not have an emergency spillway included, two conditions should be evaluated. The routed 100 -year WSEL should provide two feet of freeboard between the 100 -year WSEL and the top of the berm. Secondly, the principal outlet or spillway (riser weir or culvert outlet) should be sized to safely pass the 100 -year frequency storm without overtopping the berm. For this condition, the evaluation should include a 50% clogging factor and is typically evaluated assuming a weir length (perimeter) or culvert (diameter) based on dimensions providing 50% of the design flow area. The principal spillway should be a minimum of 24 inches wide/diameter unless calculations show that the freeboard requirements and no overtopping conditions are met. For examples of design calculations of outlet structure orifices and weirs, see the VDOT Drainage Manual and VA BMP Clearinghouse. All riser structures shall be cast -in-place or precast concrete, unless a substitute material has been approved by the County. VDOT standards for riser structures may be found in the VDOT Standards. Outlet pipes shall be reinforced concrete pipe with rubber gasket watertight joints, shall have appropriate seepage control, and shall be installed on a concrete cradle from the tie of the pipe to the riser for the entire length of the outfall pipe_ Concrete cradle shall be in accordance with the requirements of the VDOT Standards. COUNTY OF ROANOKE MARCH 22, 2016 9-6 STORMWATER DETENTION STORMWATER DETENTION C. Adequate Channel CHAPTER 9 Outflows from stormwater detention facilities shall be discharged to an adequate channel. For adequate channel requirements, see Chapter 5. 9.2.8 Omitted 9.2.9 Landscaping Stormwater basin embankments shall be vegetated. Selection and plant installation shall be in accordance with the standards of the VA BMP Clearinghouse. Trees and shrubs shall not be planted within a stormwater detention basin, nor on a stormwater basin berm, dam, or emergency spillway. The VA BMP Clearinghouse shall be utilized for guidance for landscaping in the marsh areas of enhanced extended detention basins. Native plants will be used to the maximum extent possible. 9.2.10 Underground Detention A. Materials All materials used in underground detention facilities shall be corrosion resistant consisting of reinforced concrete, aluminized corrugated metal pipe, corrugated high density polyethylene pipe, or similar approved material. B. Slope Underground detention facilities shall be sloped to drain at a minimum floor slope of 0.5 percent. C. Capacity Underground detention facilities shall be sized such that the 100 -year design storm may be routed through the facility with no damage to the surface property. D. Accessibility and Maintainability All underground detention facilities shall be designed to be readily accessible for periodic inspection and maintenance from the surface without the need to perform confined space entry. COUNTY OF ROANOKE MARCH 22, 2016 9-7 STORMWATER DETENTION STORMWATER DETENTION CHAPTER 9 Providing pre-treatment to remove sediments before or at the entrance of the underground detention facility to improve water quality and/or improve maintainability should be considered during the design. 9.2.11 Trash Racks Outlet structures shall be equipped with an appropriate trash rack. The trash rack shall be in accordance with the VA BMP Clearinghouse. 9.3 Environmental Impacts Environmental impacts shall be carefully considered when siting stormwater detention facilities. Siting basins in low lying areas with potentially environmentally sensitive areas requires careful consideration, coordination, approval, and permitting with local, state, and federal agencies to evaluate the suitability of constructing in these areas. Environmentally sensitive areas include, but are not limited to wetlands, shallow marshes, jurisdictional waters, natural watercourses, wildlife habitat, etc. and may be protected by state and/or federal laws. With careful planning, it may be possible to incorporate wetland mitigation into the basin design. Construction of stormwater basins or modifications to existing basins shall comply with all applicable laws and regulations. The applicant is responsible for procuring all necessary permits, such as US Army Corps of Engineers and Virginia DEQ Wetland Permits, Virginia DEQ VPDES Permits, VSMP Permits, etc., prior to beginning construction. Copies of all permits shall be provided to Roanoke County prior to a land disturbing permit being issued. See Chapter 12 for more information. Detention facilities shall be coordinated with a watershed or regional plan for managing stormwater runoff, if available. 9.4 Maintenance Requirements For the post -construction maintenance of stormwater detention facilities, see Chapter 14. COUNTY OF ROANOKE MARCH 22, 2016 9-8 STORMWATER DETENTION ENERGY DISSIPATION Chapter 10 - Energy Dissipation CHAPTER 10 Outlet protection for culverts, storm drains, BMP outlets, and steep open channels is essential to preventing erosion from damaging downstream channels and drainage structures. Erosion problems at culverts or at the outlet from detention basins are a common occurrence. Determination of the flow conditions, scour potential, and channel erosion resistance shall be standard procedure for all designs. Outlet protection can be a channel lining, structure, or flow barrier designed to lower excessive flow velocities and prevent erosion and scour. Outlet protection shall be employed whenever the velocity of flow at a pipe or open channel outlet exceeds the erosive velocity of the immediate downstream reach. Energy dissipation may take the form of the following: • Erosion control stone -lined channels; • Riprap outlet basins; or • Concrete baffled outlets. 10.1 References Except where more stringent requirements are presented in this Design Manual, energy dissipators shall comply with VDOT and other state requirements. The primary design references are the VDOT Drainage Manual and the VA E&SC Handbook. Other appropriate references include: • VDOT Standards • VA SWM Handbook • FHWA Design of Riprap Revetment HEC No. 11 (Pub. No. FHWA-IP-89-016 1989/2000) • FHWA Hydraulic Design of Energy Dissipators for Culverts and Channels HEC No. 14 (Pub. No. FHWA-EPD-86-110 Sept. 1983 & FHWA-IF-00-02 2000) • U.S. Dept. of the Interior — Bureau of Reclamation: Hydraulic Design of Stilling Basins and Energy Dissipators (Engineering Monograph No. 25) COUNTY OF ROANOKE March 22, 2016 10-1 ENERGY DISSIPATION ENERGY DISSIPATION CHAPTER 10 • U.S. Dept. of the Interior — Bureau of Reclamation: Design of Small Canal Structures 10.2 Design Methodology and Criteria 10.2.1 Outlet Velocity Where the outlet velocity from culverts, storm drain outfalls, or open channels is high, and channel or pipe modifications cannot adequately reduce the velocity, energy dissipation may be necessary. See the VDOT Drainage Manual Sections 7.4.6 and 8.3.2 for methodologies to determine design outlet velocities from open channels, culverts, and storm drains. For the calculation of open channel velocity, see Chapter 5. For the calculation of exit velocity from culverts, see Chapter 6. For the calculation of exit velocity from storm drain pipes, see Chapter 7. 10.2.2 Erosion Control Stone The most common form of energy dissipation is the use of erosion control stone at the outlet. Protection is provided primarily by having sufficient length and flare to dissipate energy by expanding the flow. The outlet velocities are computed for the VDOT design discharge. Where a pipe discharges into a channel, the apron shall extend across the channel bottom and shall extend up the bank to a depth of one foot above the maximum tailwater depth from the design storm event. The dimensional requirements of the erosion control stone apron shall be determined using the graphical curves in the VA E&SC Handbook. Generally, the use of erosion control stone for energy dissipation is limited to a maximum velocity of 19 feet per second. Alternative means of energy dissipation shall be required where the discharge velocity is greater than 19 feet per second. Alternative means include riprap outlet basins or concrete baffled outlets. The use of alternative means of energy dissipation requires the approval of VDOT when located in a VDOT right-of-way. 10.2.3 Riprap Outlet Basins A riprap basin is a depressed area of riprap placed at the outlet of a high velocity culvert, storm drain outlet or open channel. The riprap reduces the exit velocity COUNTY OF ROANOKE March 22, 2016 10-2 ENERGY DISSIPATION ENERGY DISSIPATION CHAPTER 10 by expanding the flow over the riprap length and width and forming a hydraulic jump. For the design of riprap basins, refer to the VDOT Drainage Manual. Dissipator geometry may also be computed using the "Energy Dissipator" module that is available in the computer program FHWA HY8, Culvert Analysis. Details of the riprap basin energy dissipator are included in Appendix 10A. 10.2.4 Baffled Outlets A baffled outlet usually consists of a concrete box structure with a vertical hanging concrete baffle and an end sill. Several variations of concrete baffled outlets have been published by VDOT and other state and local transportation and stormwater management agencies. A typical schematic of baffled outlets are shown in Appendix l OC. Baffled outlets are usually used when very high exit velocities exist at piped or channel transitions. Baffled outlets function by dissipating energy through impact of the water hitting the baffle and through the resulting turbulence. A tailwater depth is not required for adequate energy dissipation, but will help smooth the outlet flow. This type of outlet protection may be used with outlet velocities up to 50 feet per second. Baffled outlets are not included in state guidance handbooks. Hydraulic design procedures for baffled outlets may be found in the U.S. Department of Interior, Bureau of Reclamation, Design of Small Canal Structures, 1978 and are as follows: Step 1: Determine input parameters, including: H = Energy head to be dissipated, feet (can be approximated as the difference between channel invert elevations at the inlet and outlet). Where: Q = Design discharge, cubic feet/second v = Theoretical discharge velocity determined from 2 g H, feet/second A = Flow area, Q / v, feet d = Flow depth entering the basin, ft COUNTY OF ROANOKE March 22, 2016 10-3 ENERGY DISSIPATION ENERGY DISSIPATION CHAPTER 10 Fr = Froude number = v / ( g d )0.5, dimensionless g = Gravitational constant = 32.2 feet/second2 Step 2: Calculate the minimum basin width, W, in feet, using the following equation: W / d = 2.88 (Fr)0-566 Where: W = minimum basin width, feet d = depth of incoming flow, feet Fr = Froude number = v / ( g d )0.5 The limits of the W/d ratio are from 3 to 10, which corresponds to Froude numbers 1 to 9. If the basin is much wider than W, flow will pass under the baffle and energy dissipation will not be effective. Sten 3: Calculate other basin dimensions as a function of W Refer to the Schematic of Baffled Outlet in Appendix l OCA for other dimensions as a function of W and to identify variables that are used below in other steps. Step 4: Calculate the required protection for the transition from the baffled outlet to the natural channel based on the outlet width. A riprap apron shall be added of width W, length W (or a 5 -foot minimum), and depth f (W/6). The side slopes shall be 1.5:1, and the median rock diameter shall be at least W/20. Step 5: Calculate the baffled outlet invert elevation based on the expected tailwater The maximum distance between expected tailwater elevation and the invert should be b+f or some flow will go over the baffle with no energy dissipation. If the tailwater is known and fairly controlled, the baffled outlet invert should be a distance ( b / 2 ) + f below the calculated tailwater elevation. If tailwater is uncontrolled, the baffled outlet invert should be a distance f below the downstream channel invert. Step 6: Calculate the outlet pipe diameter entering the basin assuming a velocity of 12 fps flowing full. COUNTY OF ROANOKE March 22, 2016 10-4 ENERGY DISSIPATION ENERGY DISSIPATION CHAPTER 10 Step 7: If the entrance pipe slopes steeply downward, the entrance pipe shall be turned horizontal for at least 3 feet before entering the baffled outlet. Step 8: If it is possible that both the upstream and downstream ends of the pipe will be submerged, provide an air vent approximately 1/6 of the pipe diameter near the upstream end to prevent pressure fluctuations and possible surging flow conditions. 10.2.5 Energy Dissipator for Paved Areas For energy dissipation from velocities from paved channels or flumes, use VDOT Standards. Schematics of energy dissipators for paved flumes has been included in Appendix IOC. 10.2.6 Additional Energy Dissipators For additional energy dissipators, refer to FHWA HEC No 14 entitled, Hydraulic Design of Energy Dissipators for Culverts and Channels_ 10.3 Installation Requirements Energy dissipators shall be installed and constructed according to all applicable FHWA, VDOT, and other state requirements and recommendations. 10.4 Easements Where an energy dissipater will be owned by a public jurisdiction or agency, a drainage easement must encompass the entire energy dissipator, and provide an additional area 10 feet wide around the entire energy dissipator to provide for maintenance. 10.5 Environmental Impacts Construction or modifications to energy dissipation structures shall comply with all applicable laws and regulations. The applicant is responsible for procuring all necessary permits, such as US Army Corps of Engineers and VA DEQ Wetland Permits, etc. 10.6 Maintenance Requirements The permittee is responsible for maintenance of energy dissipation structures until construction is complete, including final clean up and site stabilization, to the satisfaction of the County. After the completion of construction, property owners or responsible parties are responsible for maintenance of all energy dissipation structures located in private easements. COUNTY OF ROANOKE March 22, 2016 10-5 ENERGY DISSIPATION ENERGY DISSIPATION APPENDIX 10A AIDS FOR ENERGY DISSIPATION DESIGN FROM VDOT DRAINAGE MANUAL Figure 8E-1, Details of Riprap Basin Energy Dissipator Figure 8E-3, Riprap Basin Design Checklist APPENDIX 10A COUNTY OF ROANOKE March 22, 2016 1OA-1 ENERGY DISSIPATION ENERGY DISSIPATION Chapter 8 — Culverts Appendix 8E-1 Energy Dissipation O15SIPATEIR POOL APRO{ 7Oh4LtiR 3 W, V""5'.0pWo- YAin 454, �+ FaP ❑F Ru NOTE A 0,0 r 6 2 TOP OF RFRAF NpFE B Y. TW Jy, HORI• fh �' ZGNTAL 14 I id OR Za 2dM OR ' 5R WM.. 2j. OR 1,Sd.u. Tsn. wIN. 27y0 OR 1.5d,. 1-5d CL SECTION rU IK �O1 f I @Of � r `"/ APRON 1 �f� 1 w2H SruM. tY:2H CuVER* I. h'ARIZONTAL L Wy a� HALF PLAN �k NOTE i HRi4R+�L CHANNEL SEC -A -A A—] � __� A. APPENDIX 10A TOP OF NAYURA. CHAJIN EL TH:ICICENED OR SLOPING TOE OPTIONAL. CONSTRUCT I= DOWNSTREAM CHANNEL DEGRADATION 15 A.VTiCiPATED. nOTE 6 NOTE W, DIAMETER FOR PIPE CULVERT W,= BARREL WIDTIi FOR BOX CULVERT W,= SPAN OF PIPE -ARCH CULVERT h� 2430 OR 4.54 E-xCAVA.TE TO TI -4S LINE. @ACKFILL WITH RIPRAP w SEC. C -C sd,a 2 ' J BERv AS RECUREQBERM AS 2EOUrIIED TO, SUPPORT RIPRAP TO SIJPPORY RPRAP 2d.,Y Oft S.SdyAx EXCAVA72 TO TI -S LINE. 9ACOILL WITH RIPRAP SEC. B -B SEC. D -D NOTE A - IF EX17 VELOCITY Or BASIN IS SPECIFfED, EHTEND BASIN AS REDURIED TO OSTAN SUFFICIENT CROSS-SECTIONAL AREA AT SECTIpN A -A 5UCH THAT Q,_/4CROSS SECTION AREA AT SGC, A -A) = SPECIFIEU EXIT VELOCITY. NOTE B WARP BASIN TO CONFORM TC NATURAL 5TREAm CHANNEL, TCP OF RIPPAP IN FLOOR OF BASIN SHOULD BE AT THE SAME ELEVATION OR LOWER THAN NATURAL CHANNEL BOTTOM AT SEC. A -A_ Figure 8E-1. Details of Riprap Basin Energy Dissipator SE,4 of 13 VDOT Drainage Manual COUNTY OF ROANOKE March 22, 2016 10A-2 ENERGY DISSIPATION ENERGY DISSIPATION Chapter 8 — Culveds Appendix 8E-1 Energy Dissipation Project No. _ Designer _ Reviewer CULVERT BRINK TW 0 DESIGN VALUES (Figure SP -2) FAD i. Depth. d, D„ ;d£ D. Froude No.. Fr 4A RIPRAP BASIN Date 'slate APPENDIX 10A MSIPATOR POOL '1 NOTF • i . - �i�=24-"Z *`� �t�tfa. TW ORZ. 3d,0 OR r . .y m,wmAW TAILWATER CHECK Tailxaier. TW Equivaiem deprh, dE TWId, 1F TWld, a 0.75. calcul, is rrprap downstream using Figure WA D,-(4&lzles TRIAL I FINAL . 1 TWAL BASIN MIENSIONS I FEEr Pool length is the 3 artier of Ion, 3W� Basin length is the larger Ishs 4W. Appra h TLiCkMSS 31)r, Basin Thickness 2A„ DOWNSTREAM RIPRaP(Figum SE4) UDE L VLN, V, D. 10 is 20 21 Figure 8E- 3. Riprap Basin Design Checklist OE -6 of 93 VDOT Drainage Manual COUNTY OF ROANOKE March 22, 2016 10A-3 ENERGY DISSIPATION ENERGY DISSIPATION APPENDIX lOB AIDS FOR ENERGY DISSIPATION DESIGN FROM VDOT ROAD AND BRIDGE STANDARDS Standard 114.01, Stone for Erosion Control APPENDIX 10B COUNTY OF ROANOKE March 22, 2016 1OB-1 ENERGY DISSIPATION ENERGY DISSIPATION L z 0 I � i 11 l 1 14k n a z 0 APPENDIX lOB 1p z W {l7 G4�4* !7N ^F COUNTY OF ROANOKE March 22, 2016 1OB-2 ENERGY DISSIPATION ms J R. m a x p � -Z� 2 Mp fh {�W� � F '�K � }} 2MU O H �x G ns ox toLS 75- 75- IN,? OM= U~ MCCy¢W u 0 M yF,J� L)yQ� L.Li7 r09 WZS} +Fg� L�fy ? lit;}# ® G €lI Ef3 O r aw r7 It y74 A+Y} La LL €7 Ld 0 i if 1p z W {l7 G4�4* !7N ^F COUNTY OF ROANOKE March 22, 2016 1OB-2 ENERGY DISSIPATION ENERGY DISSIPATION APPENDIX IOC APPENDIX IOC ENERGY DISSIPATION DESIGN SCHEMATICS Schematics of Baffled Outlet, from US Bureau of Reclamation, Design of Small Canal Structures (as used by the State of Georgia and State of Colorado) Standard Energy Dissipator for Use with Paved Flume, from VDOT Road and Bridge Standards Precast Energy Dissipator, from VDOT Road and Bridge Standards Level Spreader from VA DCR Stormwater Specifications Various Energy Dissipators and Stilling Basins, from City of Knoxville, TN BMP Manual COUNTY OF ROANOKE March 22, 2016 10C-1 ENERGY DISSIPATION ENERGY DISSIPATION VA DCR STORMWATER DESIGN SPECIFICATION NO. 2 APPENDIX IOC SHEET FLOW TO FILTER OR OPEN SPACE 1-31N_ COURSE AGGREGATE �- KEY LEVEL SPREADER OR OTHER LINING AS INTO EXISTING GRADE RIPRAP PLUNGE POOL RIPRAP APRON 6' X 6" TREATED .1 NIA TIMBERS OR DESIGN DISCHARGE CONCRETE LIP 2" MIN LENGTH OF LEVEL SPREADER LIP TO BE BASED ON DESIGN FLOW AND ALLOWABLE VELOCITY .7 M,qk TOP OF LEVEL SPREADER SHALL BE FLAT 1-31N_ COURSE AGGREGATE �- OR OTHER LINING AS DESIGNED FOR STABILITY PLAIN VIEW DIMENSION BASEL) UN UN IsTunom o IGTINQ ADE _ DESIGN DISCHARGE E%(20:1) OR LESS. IF VEGETATEo FILTER STRIP OR CONSERVED 2" MIN OPEN SPACE: FIRST 10 FEET LFSS THAN 2% 3' MIN 10, MIN 3' MIN MIN. DEPTH BASED ON REQUIRED STONE SIZE SECTIONA-A Figure 2.4: Level Spreader: Pipe or Channel Flow to Filter Strip or Preserver) Open Apace Version 2.0, January 1, 2013 Page 8 of 21 COUNTY OF ROANOKE March 22, 2016 1OC-2 ENERGY DISSIPATION ENERGY DISSIPATION APPENDIX IOC I I —,I PLAN C 9 Protection as required Ii Min. F illejH- l {W 5�L 3 -- f a I 1/2 (} SECTION Rock diameter for profadfionm I/ O(W) Figure 4.5.11 Schematic of Baffled Outlet (Source: U.S. Npt of the Inisr, or, 1$7$} 4.5-22 k es,vgi a Siamnw,Ster management Manual Volume 2 (Technical Handbook) COUNTY OF ROANOKE March 22, 2016 10C-3 ENERGY DISSIPATION ENERGY DISSIPATION CDOT Drainage Design Manual APPENDIX IOC Energy Dissipaters PLAN PLAN I I I I Ly L 6 --f0,20 m MAY.) I r I I+—�-4 SIA ihAIN.1--« 0.15 m Y k � I I�g.{}g m FILLET v L M11 hZ 3 I € h0 Ce Il5 V=� 0 a SECTION STILLING BASIN DESIGN r � I t2 :74 h3 a, a � ❑.t m R @EODINC SECTION ALTERNATIVE END SILL Figure 11.7 USSR'rype VI (impact) Dissipater COUNTY OF ROANOKE March 22, 2016 1OC-4 ENERGY DISSIPATION ENERGY DISSIPATION APPENDIX 10C NMOURNa N ri is to io k co co io 0o io b 6o a MMM0 t MMMMMM 4T WO _� Q $ `J 1L s as aQ c� tI��S Vats �ti w, $ S? b to io } F Yi g� & T t ® N 7rQ Oa Ly 7.1 N$ M rtf O a= H M CL DE d }3 W WLI; ffiLu � h�O Nry •A M M F r F Sl N r W it 0 } a cn % {I1 - i 4 N 0 LLJ � > rrl� C4 V 4 Q CL H N m W W W W W Z o Ww t8 p 92 CIA 2 rz mmm u- a sane R i saves _ a � ca save 7 J �° � C r La SaYB v + Vi at 0 d Z 15 Ld W 4 o Vl iia1Vd15510 A9ill COUNTY OF ROANOKE March 22, 2016 10C-5 ENERGY DISSIPATION ENERGY DISSIPATION APPENDIXIOC COUNTY OF ROANOKE March 22, 2016 1OC6 ENERGY DISSIPATION a §T pi /5 A _ . > o_ �§ m § K2�s� ® § ( e o �o®¥�E §%,k; : P Q N i 2 § �• R § w m ( N� W§ / win-. � � <� QQ 2 , . c 44 14-a % §- w In ; E - iQ m co J _ « § I. - a §■ Q Lu 46 \ , ■ . 3-s .�&.4. ¥ ■ 0 COUNTY OF ROANOKE March 22, 2016 1OC6 ENERGY DISSIPATION ENERGY DISSIPATION APPENDIX IOC I ACTIVITY: outlet Protection ES - 25 Chute blocks (size and shape_ vary) – Baffle ;piers, optional , see Vote (size and shape Mary) I Sufficient depth for — hydraulic jump plus adequate freeboard End sill (maybe derotated) Typical Stilling Basin At End of Paved Flume or Chute Computed normal flow L culvert Concrete stilling basin Baffles w slow water dawn (see nate 2) without excessive head loss Typical Stilling Basin lasing Baffles and Elevation Drop Stagger baffle blocks I iteral ly 'l'vpical Enerr4v Dissipator ; Baffle Blocks Within Headwall Securely fasten CM? tee section with coupling bands or screws a... ., y,.. - - Support structure with sandbags or other materials to prevent movement Temporary CMP Enerey Dissinatur Nates: 1. This is the basic format for several types of stilling basins. I.JSBR Type II basin does not contain baffle piers, but does have a dentated end sill. USBR Type lII basin has baffle piers and a smooth undentated end sill. See HEC -14 for detailed design of concrete structures. 2. Concrete stilling basin should be approximately as wide as the downstream channel. Design baffles to retain sufficient stormwater to act as a plunge Fool for a wide range of flow values. Relies on sufficient tailwater to halt flow velocity t Typical Impact Energypater (Virginia DOT? NOT TO SCALE Figure ES -25-2 Various Energy Dissipaters and Stilling Basins COUNTY OF ROANOKE March 22, 2016 10C-7 ENERGY DISSIPATION (RESERVED) Chapter 11— (RESERVED) COUNTY OF ROANOKE MARCH 22, 2016 CHAPTER 11 (RESERVED) ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A Chapter 12 - Environmentally Sensitive Areas Stormwater discharges to areas with features identified as environmentally sensitive may be subject to additional requirements, or may need to utilize or restrict certain stormwater management practices. The following type of areas are considered to be "environmentally sensitive": • Floodplains —Areas identified within a 100 -year recurrence interval flood plain. • Steep Slopes — Areas with a slope of 33 percent or greater. • Stream Buffers — Setbacks and vegetative buffers established adjacent to the Roanoke River as required by the County of Roanoke zoning ordinance or designated conservation area buffer zones at each bank of streams, ponds, lakes, wetlands, and stormwater BMPs. • Critical Erosion Areas — Areas with potential serious erosion problems as defined in the VA E&SC Handbook. These fall into two sub categories. o The erosion hazard is critical if the slope length exceeds the following criteria: 0-7% slope > 300 feet 7-15% slope > 150 feet >15% slope > 75 feet o Areas may be critical if the soils are highly erodible, as classified using the United States Department of Agriculture (USDA) Natural Resources Conservation Service (formerly Soil Conservation Service) methods, either Land Capability Classification IIIe, IVe, IV, VII, or VIII or with an erodibility index factor greater than 8. • Karst Geology — Areas where the underlying geologic conditions include caves and crevices which allow stormwater to infiltrate and quickly migrate and transport potential pollutants. • Hot Spots — Areas where a high potential for stormwater pollution may occur due to current or former activity on the site. • Jurisdictional Streams and/or Water — Waters regulated by U.S. Army Corps of Engineers (USACE) under Section 404 of the Clean Water Act. A jurisdictional determination (JD) is required that identifies and separates the Corps regulated areas from non-regulated areas. Disturbance in regulated areas requires a permit form USACE. JDs are typically good for 5 years after the determination has been made by COUNTY OF ROANOKE MARCH 22, 2016 12-1 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A the USACE. Third party reports by qualified professionals will be accepted for jurisdictional stream delineation. Wetlands- Wetlands regulated by U.S. Army Corps of Engineers (USACE) under Section 404 of the Clean Water Act. A jurisdictional determination (JD) is required that identifies and delineates wetlands. Disturbance in wetlands requires a permit form USACE. JDs are typically good for 5 years after the determination has been made by the USACE. Third party reports by qualified professionals will be accepted for wetland delineation. 12.1 References The following publications may be useful in providing guidance when performing construction, establishing development limits, and developing appropriate strategies and design features to address the special concerns related to environmentally sensitive areas: • VDOT Drainage Manual • VA E&SC Handbook • VA SWM Handbook • Virginia Department of Conservation and Recreation, Technical Bulletin No. 2, Hydrologic Modeling and Design in Karst • International Building Code • The Development of the Land Capability Classification (reprinted from Readings in the History of the Soil Conservation Service), Douglas Helms, Soil Conservation Service, 1992 • Clean Water Act Section 404 • River & Harbors Act of 1899 Section 10 • FEMA Flood Map Service Center • Flood Insurance Rate Map (FIRM) COUNTY OF ROANOKE MARCH 22, 2016 12-2 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A 12.2 Floodplains The purpose of floodplain management is to regulate the use of the floodplains in order to protect life and property, prevent sedimentation and pollution of water resources, and to prevent or protect against the general degradation of the environment. Floodplains and their regulatory requirements are generally based on the stream flows generated by a 100 -year frequency storm and existing land development conditions. However, storms and future land development can generate flows of greater magnitude and flooding above and beyond these limits. For this reason, additional vertical and horizontal setbacks from the floodplain limits are strongly encouraged to account for future development within the upstream drainage area and to serve as a factor of safety for larger flood events. Floodplains include: Areas identified within a 100 -year recurrence interval floodplain as identified by the Federal Emergency Management Agency (FEMA). These areas have been identified as the Floodplain Overlay District by the County of Roanoke Zoning Ordinance. Areas identified within a 100 -year interval floodplain as identified by an applicant floodplain study. Management of floodplains in Roanoke County shall be in accordance with the requirements published in the County of Roanoke Zoning Ordinance. Under no conditions, shall the land disturbance activity adversely affect the capacity of channels, floodways, ditches, or any drainage facility or system. The lowest floor elevation of any new residential structure, as defined in the County of Roanoke Zoning Ordinance Section 30-28, shall be at least 2 feet above the base flood elevation. The lowest floor elevation of any new non-residential structure shall be at least 1 foot above the base flood elevation unless the structure is floodproofed_ The elevation of the lowest floor shall be certified by a Registered Surveyor or Professional Engineer on an Elevation Certificate after the lowest floor is installed. Grading and cut and fill operations within the 100 -year flood plain are discouraged and must be approved by the County of Roanoke. Activity within the floodplain must also be coordinated with other regulatory requirements and agencies. These may include erosion and sediment control, stream buffer protection, FEMA, VMRC, U.S. Army Corps of Engineers, Virginia DEQ, and others. COUNTY OF ROANOKE MARCH 22, 2016 12-3 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A Construction of stormwater management impoundment structures within a floodplain shall be avoided to the extent possible. Where this is unavoidable, all stormwater management facility construction shall be in compliance with all applicable regulations under the National Flood Insurance Program, 44 CFR Part 59, and in accordance with the County of Roanoke Zoning Ordinance. The County does not have the authority to alter or modify the flood limits and/or elevations established by FEMA. Should an applicant flood study indicate any alteration in FEMA's limits and/or elevations, then the applicant must contact FEMA and obtain a map revision. 12.2.1 Applicant Flood Study Requirements A flood study, prepared by a Professional Engineer, must be prepared and submitted, by the applicant, for all areas where the drainage area is 100 acres or greater, and there are no detailed flood profiles or elevations from a FEMA Flood Insurance Study. There are two levels of studies. A detail study is required, if any development is proposed within the floodplain. Development includes grading and road crossings. A limited detail study is acceptable, if no development is proposed within the floodplain and the purpose of the study is to avoid the floodplain. A detail study involves a rigorous detailed hydrologic and hydraulic study of a flooding source reach. The typical riverine detail study includes the following minimum steps: • Field survey of stream and floodplain cross-sections • Field survey of all hydraulic structure crossings. • Collection of historical high water mark elevations and model calibration/verification, if data is available. • Detailed hydrologic & hydraulic modeling/computations • Establishment of the FEMA regulatory Floodway • Other tasks meeting all FEMA Guidelines and Specifications for Flood Hazard Mapping Partners A limited detail study may be performed when development is to occur adjacent to, but not in the existing floodplain. In most limited detail modeling, local regional regression equations along with a HEC -RAS hydraulic model will be developed. The major difference between the HEC -RAS models for the limited detail study and the detail study will be the amount of field survey information collected in the field and used to create the model and the amount of time spent on calibration to historical flood elevations. The limited detail models typically include no field survey data, and floodways are typically not computed. The COUNTY OF ROANOKE MARCII 22, 2016 12-4 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A methods for limited detail study are further outlined in the FEMA Guidelines and Specifications for Flood Hazard Mapping Partners In addition, the following information and items are required when an applicant flood study is submitted to Roanoke County for review: • The flood study shall be based on the ultimate land use conditions as published in the most recent Comprehensive Plan for upstream areas. Structure locations shall be based on the ultimate build out data. • The flood study shall be prepared by a registered Professional Engineer licensed to practice engineering in Virginia, sealed, signed, and dated. • Assuming that sedimentation or scour may occur during the storm event is not acceptable. • The flood study shall compare pre- and post -development conditions to verify that the proposed development will not increase the 100 year flood elevation more than 1 foot at any point. • The flood study shall consider backwater conditions, local obstructions and, where required by the County of Roanoke Department of Community Development, the partial or complete failure of any enclosed drainage system. Consideration must be given to the overflow path, to ensure that no structures will flood in the event of system failure. The flood study shall analyze the 100 -year flood path for all new development. A digital version of the 100 -year flood limits and cross sections must be provided to the County. The study and supporting data will become public information. The site plan digital file shall be in ACAD format and tied to the correct State Plane Coordinate. Cross sections from the study must be indicated on the site plans submitted as a part of the development review package. 12.2.2 Floodplain Delineation The limits of floodplain floodways shall be staked and flagged in the field prior to any land disturbance activities and they shall remain undisturbed during construction. After the completion of construction, the limits of floodplain floodways shall be checked to verify that no unauthorized filling has taken place in the floodway. COUNTY OF ROANOKE MARCH 22, 2016 12-5 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A Place floodplain limits and floodways on the final plats submitted for each property. All subdivision plats and site plans located within the floodplain in whole or in part shall include base flood elevation data. 12.3 Steep Slopes Special precautions and guidelines are required for development in areas having steep slopes, defined as thirty-three and one third percent (33.3%) or greater. These precautions and guidelines address the increased potential for soil erosion, sedimentation, water pollution and septic disposal problems associated with the development of areas with significant topographical relief. Unrestricted development of steep slopes may result in: • Rapid and/or large-scale movement of soil and rock; • Rapid and excessive stormwater run-off, • Deposition of eroded material leading to siltation of natural and man-made bodies of water; • Loss of aesthetic resource; and • Greater travel distance of septic effluent in the event of septic system failure. 12.3.1 Development Restrictions Land -disturbing activities on steep slopes are regulated by Chapter 8.1 of the County Code, "Erosion and Sediment Control and Steep Slope Development Ordinance of the County of Roanoke, Virginia." If the grade of a site is greater than 33.3%, refer to the International Building Code for steep slope development requirements. 12.3.2 Design Standards No land disturbance of steep slopes may occur without a geotechnical study that concludes that the land disturbance will result in a stable finished slope. For the requirements of a geotechnical study, see County of Roanoke Erosion and Sediment Control and Steep Slope Ordinance. Land disturbance of steep slopes require the preparation and submittal to the County of as -built plans showing that the finished geometry is in substantial conformity with the approved site plan. COUNTY OF ROANOKE MARCH 22, 2016 12-6 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A Site grading and measures required to control stormwater runoff shall collect and carry storm drainage away from the steep slope to the extent possible. If concentrated runoff is to be discharged in areas of steep slopes, adequate protection must be installed to prevent channel erosion and energy dissipation shall be used at the base of the steep slope to prevent erosion where the flow transitions to a shallower slope. The use of a closed conduit storm drain should be considered in accordance with Chapter 7. 12.4 Stream Buffers Stream buffers are established to provide a naturally vegetated strip of land adjacent to a stream. This buffer protects the stream from encroachment by development, preserves the water, recreational, and environmental resources, protects the floodplain and floodway, retards runoff, and helps improve the water quality of stream by preventing erosion and filtering non -point source pollution from runoff. The establishment of stream buffers as a water quality measure is encouraged by the County of Roanoke. Requirements for stream buffers shall be in accordance with Section 30-75 of the County of Roanoke Zoning Ordinance- Roanoke River Conservation and Overlay District. Additionally, the development must meet the required stream setbacks as outlined in Section 30-75-5. 12.5 Critical Erosion Areas Critical erosion areas, if cleared of vegetation and exposed to the elements of nature, may experience significant erosion and sedimentation problems, including a significant loss of topsoil. These soils tend to be located on hillsides and areas with steep slopes, and adjacent to river valleys and tributaries. Critical erosion areas include: • The erosion hazard is critical if the slope length exceeds the following criteria: 0-7% slope > 300 feet 7-15% slope > 150 feet >15% slope > 75 feet Critical erosion areas shall be indicated on the Erosion and Sediment Control Plan. To the extent feasible, disturbance of critical erosion areas shall be avoided or minimized. Where critical erosion areas are disturbed, their protection and stabilization shall specifically be addressed by the Erosion and Sediment Control Plan and the Stormwater Management Plan. COUNTY OF ROANOKE MARCH 22, 2016 12-7 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A 12.6 Karst Geology Developers and Designers are cautioned that construction in karst geology requires special care and study; and that they are responsible to ensure that all appropriate investigations are performed by licensed geotechnical engineers or geologists to ensure long-term soil stability for proposed buildings and site improvements. Although proper study of site conditions is the responsibility of the Developer and Designer, Roanoke County may, at its discretion, require a geotechnical investigation, prepared by a licensed geotechnical engineer or geologist, on a case by case basis. Karst is an underlying geology which is common in Roanoke County where the underlying rock is predominantly soluble limestone or dolomite creating caves, crevices, and other cavities in the rock. Stormwater may infiltrate to the karst geologic rock and quickly drain through the open cavities. In addition to providing a quick transport mechanism for potential stormwater pollutants, this may create quick erosion of the limestone, potentially causing sinkholes or other surface sloughing. Identification of karst geology shall be based on local geology and soils maps, aerial photography, and site visits by a person familiar with karst geology. Karst areas present problems with conventional hydrologic stormwater models, creating poor representation of runoff rates as most models do not have allowances for losses through sinkholes, crevices, or caves. See DCR Technical Bulletin 42, Hydrologic Modeling and Design in Karst for additional information on identification, and modeling requirements for areas in karst geology. Recommended practices include: • Design the site to take maximum advantage of topography. • Minimize site disturbance, cuts, fills, and drainage alterations. • Minimize the impervious surface. • Stormwater conveyance structures shall be designed to dissipate overland flow over the largest areas possible. Avoid concentration of flows and ponding. • Stormwater management facilities located in karst areas shall be installed with a liner. Only BMP structures approved for karst areas by the VA BMP Clearinghouse will be allowed for installation. 12.7 Stormwater Hot Spots Stormwater discharges from land uses or activities with higher potential pollutant loadings, known as "hotspots", may require a greater level of stormwater treatment or the COUNTY OF ROANOKE MARCH 22, 2016 12-8 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A use of specific structural BMPs and pollution prevention practices. Greater concentrations of sediment, hydrocarbons, traces metals, pesticides, and other toxics than are found in typical stormwater runoff may qualify a site for designation as a hot spot. The following land uses and activities may be stormwater hotspots: 1. Vehicle salvage yards and recycling facilities; 2. Vehicle fueling stations; 3. Vehicle service and maintenance facilities; 4. Vehicle and equipment cleaning facilities; 5. Fleet storage areas (bus, truck, etc); 6. Industrial sites (for SIC codes contact VA DEQ); 7. Marinas (service and maintenance areas); 8. Outdoor liquid container storage; 9. Outdoor loading and unloading facilities; 10. Public works storage areas; 11. Facilities that generate or store hazardous materials; 12. Commercial container nursery; 13. Golf courses; 14. Chemical storage; and 15. Dry cleaning operations. 12.7.1 Design Restrictions Stormwater BMP practices having an infiltration component located in stormwater hotspot areas shall be provided with adequate pretreatment or storage areas to preclude pollutants from the infiltration area. The property owner must conform with all applicable laws and regulations relevant to any chemicals or hazardous materials used on these sites. Industrial COUNTY OF ROANOKE MARCH 22, 2016 12-9 ENVIRONMENTALLY SENSITIVE AREAS ENVIRONMENTALLY SENSITIVE AREAS APPENDIX 12A operations shall be conducted to minimize exposure of chemical storage containers to stormwater, and contain any runoff as required by law where this can not be avoided. These sites must also meet DEQ VSMP and DEQ VPDES permit requirements, where applicable. 12.7.2 Golf Course Development Golf courses, while maintaining impervious area and natural buffers allow for the introduction of nutrients into stormwater through fertilizers and chemicals into stormwater through the use of pesticides and herbicides. Design of golf courses, public or private, should meet the following performance standards: Managed turf should be reduced by including areas of rough devoted to native plants, natural environments, and wildlife habitat enhancement; 2. An Integrated Pest Management and nutrient management plan should be prepared and followed; 3. Native or naturalized landscaping should be used to the extent possible; 4. Natural vegetation and trees along streams should be retained to the extend possible; 5. Stream crossings should be minimized; 6. Irrigation, drainage and retention systems should be designed to provide for efficient use of water and the protection of water quality; 7. Water reuse strategies should be employed when feasible; 8. Adherence to the "Environmental Principles of Golf Courses in the United States" published by the Center for Resource Management is encouraged. 9. A Nutrient Management Plan should be developed by a certified Nutrient Management Planner consistent with DCR's Nutrient Management Training and Certification Regulations. COUNTY OF ROANOKE MARCH 22, 2016 12-10 ENVIRONMENTALLY SENSITIVE AREAS GEOTECHNICAL STUDIES Chapter 13 - Geotechnical Studies (RESERVED) COUNTY OF ROANOKE MARCH 22, 2016 13-1 CHAPTER 13 GEOTECHNICAL STUDIES MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 Chapter 14 - Maintenance of Stormwater Management Facilities Proper maintenance of stormwater management facilities is essential to ensure proper long-term operation of these systems. Possible problems which may develop without proper maintenance include: • Stormwater structures may become clogged with debris reducing flow capacity which may cause upstream flooding; • Stormwater storage facilities may fill with sediment or debris reducing storage capacity and diminishing the ability of the facility to lower storm flows which may result in flooding downstream; • BMPs may not remove pollutants at the design levels required to meet the water quality requirements. If vegetation is not periodically cut and removed, it may release nutrients back into the environment, negating their water quality benefit. Stormwater management facilities include detention and retention basins, bioretention, grassed swales, and other BMPs that are intended to control stormwater runoff and change the characteristics of that runoff including, but not limited to, the quantity and quality, the period of release or the velocity of flow. Stormwater management facilities also include pipes and open channels, where the pipes and open channels are integral parts of the BMP (e.g. the pipes in a detention basin that convey flow from the outlet structure through an embankment to the discharge), and where the pipes and open channels are being used as BMPs to store or treat stormwater. Pipes (culverts and storm drains) and open channels that do not store or treat stormwater and are not an integral part of a BMP are storm drainage systems and not stormwater management facilities. Maintenance of stormwater management facilities are addressed in this Chapter. Maintenance of culverts, storm drains, and open channels that are not stormwater management facilities are addressed in their respective chapters. The maintenance guidance provided in this chapter is the routine maintenance that should be anticipated for typical nonproprietary BMPs; however, it is not meant to be all-inclusive. It is the applicant's responsibility to provide a project specific maintenance plan and schedule as part of the maintenance agreement. Information on BMP maintenance may also be found in the Manufacturer's literature. COUNTY OF ROANOKE MARCH 22, 2016 14-1 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.1 Responsibility for Maintenance Maintenance of stormwater management facilities is the responsibility of the permittee during construction until all work is completed, including final clean up and site stabilization, to the satisfaction of the County. At the completion of construction, maintenance of stormwater management facilities becomes the responsible party or land owner's responsibility in accordance with the executed Maintenance Agreement. The County is not responsible for maintaining private stormwater management facilities. 14.2 Maintenance Agreements A legally binding maintenance agreement specifying the parties responsible for the proper maintenance of all stormwater management facilities shall be secured prior to issuance of any permits for land disturbance activities. Responsibility for the operation and maintenance of stormwater management facilities, after the completion of construction, shall remain with the responsible party or property owner and shall legally pass to any successor or owner. The maintenance agreement shall include a project specific appendix that lists all stormwater management facilities present on the property; the minimum frequency of inspections and maintenance, and the routine maintenance that is to be performed for each stormwater management facility. The project specific appendix to the maintenance agreement is to be prepared by the applicant and submitted to the County with the Stormwater Management Plan for review. The information contained within the VA SWM Handbook, the VA BMP Clearinghouse, and Manufacturer literature shall be used, by the applicant, as a guide in preparing the project specific appendix to the maintenance agreement; however, the maintenance requirements shall be written to be specific to the project. When landscaping is a component of the stormwater management facility, a project specific maintenance schedule for the landscaping shall be provided that is reflective of the plant species that are used. The landscaping maintenance schedule shall contain guidance regarding methods, frequency, and time of year for landscape maintenance. The maintenance requirements shall stress the need to remove cut and remove vegetation from the BMP and the specific rate and method of fertilization, if any. A sample Maintenance Agreement is included on Roanoke County's website In addition, the applicant shall also establish easements for stormwater management facilities to grant the County the right of access for periodic inspections as described in Chapters 3 and 15. COUNTY OF ROANOKE MARCII 22, 2016 14-2 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3 Maintenance Program A consistent maintenance program is the best way to ensure that stormwater management facilities will continue to perform their necessary functions. The following components are common to many stormwater management facilities maintenance programs and shall be followed, where applicable. • Regular Inspections Scheduled inspections and additional inspections after major storm events are necessary to understand the condition of the stormwater management facility and discover deficiencies so that they may be corrected. • Vegetation Management Most stormwater management facilities rely on vegetation to filter sediment from stormwater and to stabilize the ground surface of the BMP. o Mowing Some stormwater management facilities may have no mow zones. Do not mow areas meant to stay natural. If mowing is allowed and desired, most grasses are hardiest if maintained as an upland meadow, with a blade height of 6 to 8 inches. If a shorter lawn is desired, additional lawn care will be needed to maintain turf health. Never cut grasses below a blade height of 4 inches. Grasses on embankments should be cut at least twice in the spring growing season, once in the summer, and twice in the fall growing season. Grass clippings should be collected, removed from the BMP, and disposed of properly. Ideally grass clippings should be composted and used as fertilizer or mulch in an upland area. Grass clippings must never be dumped into streams, open channels, storm drains, ponds, or stormwater management facilities as they will release nutrients as they decay which will flow into streams. o Fertilization One of the primary purposes of most stormwater management facilities is to remove nutrients from stormwater; therefore, it is important to not over fertilize. Often fertilization is not required, especially if grass is maintained at a height of 6 to 8 inches. Only fertilize where necessary to maintain the health of vegetation and then take care to apply only the minimum that is required. o Pest and Weed Control Avoid unnecessary pesticide and herbicide use. When absolutely required, use pesticides and herbicides in accordance with listed instructions and COUNTY OF ROANOKE MARCH 22, 2016 14-3 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 never allow spray to enter water as many of these chemicals are toxic to aquatic life in small concentrations. o Removing Accumulated Sediment Vegetation surrounding stormwater management facilities is designed to trap sediment; therefore, vegetation is likely to become laden with sediment and bare spots may emerge. Bare spots should be raked, backfilled if needed, and covered with top soil. Disturbed areas should be reseeded and mulched. Excess material should be removed and may be used as a mulch or soil supplement. If the soil becomes compacted, then aeration may be necessary. o Unwanted Vegetation Embankments must be kept clear of woody plants (trees and bushes) because their roots could cause seepage or slope failure. Consistent mowing should control any unwanted vegetation. • Slope, Embankment and Outlet Stabilization Stable slopes and embankments are necessary to ensure that erosion does not add to water quality problems and that embankments do not breach. Maintaining a health stand of grasses on slopes and embankments and preventing the grown of deep rooted (trees and shrubs) vegetation on embankment areas are important. Animal burrows can also cause deterioration to embankments. Animal burrows should be filled in as soon as they are discovered. In some cases animal control may be needed to avoid excessive burrows. Outlet structures are particularly vulnerable to undercutting and erosion. A small problem, if it is not corrected, may quickly result in the need to replace an entire structure. Consult a professional engineer if sink holes, cracking, wet areas around the outlet pipe, pipe displacement, or rusting of the pipe is observed. • Debris and Litter Control Regular debris and litter removal will reduce the chance of clogging outlet structures, prevent damage to vegetated areas, reduce mosquito breeding habitats, improve site appearance, and reduce conditions for excessive algae growth. • Mechanical Components Some stormwater management facilities have mechanical components including valves, sluice gates, anti -vortex devices, fence gates, locks, and access hatches that require periodic maintenance. • Insect Control The simplest way to control insects, particularly mosquitoes, is to avoid stagnant water. Most stormwater management facilities are designed to be dry within a short time after a rain event. If an insect problem develops in a detention basin or COUNTY OF ROANOKE MARCH 22, 2016 14-4 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 infiltration facility, then there is a maintenance issue that needs to be corrected. In stormwater management facilities, such as retention basins, that are designed to have a permanent pool of water insects may be controlled by the prompt removal of floatable debris and perhaps by introducing and maintaining a fish population. • Access Road and Area Maintenance Most stormwater management facilities are designed to be accessible by heavy machinery for maintenance and repairs. Access should be maintained by periodic removal of woody vegetation and upkeep of gravel areas. • Sediment and Pollutant Removal The primary purpose of many stormwater management facilities is the removal of sediments and nutrients (which are often attached to sediments). Sediment will naturally accumulate in a stormwater management facilities and must be periodically removed. The frequency of sediment removal will vary widely depending on the stormwater management facility's type and character of the contributing watershed. Removed sediments and pollutants should be properly disposed of in an upland area. They should be stabilized with vegetation so that they are not eroded by rainfall. Once sediment is removed, the stormwater management facility should be quickly restabilized, usually with vegetation. If maintenance operations disturb more than 5,000 square feet, an erosion and sediment control permit will be required before commencing work. Sediment and pollutant removal will usually take heavy equipment and is beyond the capabilities of most property owners without the assistance of appropriate contractors. • Component Repair or Replacement Eventually, like all infrastructure, stormwater management facilities' components will need to be repaired or replaced. Components may include inflow and outflow devices, trash racks and anti -vortex devices, valves, orifices, pipes, concrete structures, filter or infiltration media, earthworks such as embankments and side slopes Following completion of construction, routine maintenance shall be performed on stormwater management facilities as required and as specified in the Maintenance Agreement. If the County becomes aware that a stormwater management facility has not been adequately maintained, is not functioning properly, or has becomes a danger to public safety, public health, or the environment, the responsible party will be notified in writing. The responsible party shall then be required to address the deficiency issue within a reasonable time as identified in the written notice. Failure to address the deficiency issue may result in enforcement actions. COUNTY OF ROANOKE MARCH 22, 2016 14-5 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.1 Earthen Embankments Earthen embankments are an integral part of many BMPs including detention and retention basins and constructed wetlands. For Earthen Embankments maintenance guidance, see Table 14.1. Table 14.1 Earthen Embankments Maintenance Required Action Maintenance Objective Frequency of Action Inspections Inspect earthen embankments for signs of settlement, Annually seepage, woody vegetation growth, animal burrows, and good ground cover. Vegetation Objective is to maintain a healthy grass cover free of Mow grass on Management trees and brush embankments at least • Mow grass on embankments to a height of 6 to 8 twice during both inches. growing seasons and • Remove all trees and brush from embankment and once during the at least 25' beyond embankment. When removing summer. trees and brush, extract as much of the root as possible. • Fertilize, lime, or treat with pesticide or herbicide when needed to maintain grass health (do not over fertilize). • Reseed embankments as necessary to maintain vegetation. • Avoid over -fertilization. Slope, Embankment, • Fill animal burrows with compacted fill. As needed based on and Outlet . Regrade, repair, and revegetate eroded damage observed Stabilization embankments. during routine • If there are signs of seepage or embankment maintenance or slumps consult with a professional engineer. inspections Debris and Litter Keep the embankment clear of debris and litter During inspections or Control mowing Mechanical Not applicable Not applicable Components Insect Control Not applicable Not applicable Access Road and Remove woody plants and maintain surface in drivable Annually Area Maintenance condition Sediment and Not applicable Not applicable Pollutant Removal Component Repair Replace embankments that have major erosion, seepage, Infrequent and Replacement or slumping problems. Consult with a professional engineer. COUNTY OF ROANOKE MARCH 22, 2016 14-6 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.2 Principal Spillways Principal Spillways are an integral part of many BMPs including detention and retention basins and constructed wetlands. Principal spillways normally consist of an outlet structure, pipe through an embankment, and outlet discharging to a downstream open channel. For guidance for the maintenance of Principal Spillways, see Table 14.2. Table 14.2 Principal Spillways Maintenance Required Action Maintenance Objective Frequency of Action Inspections Inspect outlet structure for signs of cracks, spalling, Semiannually and after broken or loose sections, or leakage, and corrosion or every major storm event damage to anti -vortex device or trash rack; inspect pipe inspect the outlet for signs of corrosion or settling; inspect outlet structure, pipe, and protection for signs of erosion or damage. outlet protection. Vegetation Not applicable Not applicable Management Slope, Embankment, Repair any erosion damage to outlet protection. As needed based on and Outlet damage observed during Stabilization routine inspections Debris and Litter Keep outlet structure clear of debris. Remove debris Semiannually and after Control from the BMP and properly dispose of in an upland area. major rain events as a minimum. Debris removal may be more frequent. Mechanical If a drain valve is present, exercise the valve As noted Components semiannually to insure proper function. Periodically lubricate the stem and paint exposed metal to protect from corrosion. Insect Control Not applicable Not applicable Access Road and Remove woody plants and maintain surface in drivable Annually Area Maintenance condition Sediment and Not applicable Not applicable Pollutant Removal Component Repair Repair or replace outlet structure components to correct Infrequently and Replacement leakage, cracks, spalling, broken or loose sections, or corrosion. Repair or replace pipe to correct settlement, leakage, or corrosion. Repair or replace outlet protection to correct erosion damage. Take care to avoid changing the BMP discharge characteristics and to avoid damage to the embankment. Repairs and replacements may require consulting a professional engineer. COUNTY OF ROANOKE MARCH 22, 2016 14-7 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.3 Emergency Spillway Emergency Spillways are an integral part of many BMPs including detention and retention basins and constructed wetlands. Emergency spillways normally consist of an open channel, usually trapezoidal in cross-section, which are constructed beside an embankment to carry stormwater discharge from the BMP that is too great to be carried by the principal spillway. Emergency spillways should only discharge stormwater very infrequently Emergency spillways are most often vegetated (grassed), but may be protected against erosion by rip rap or concrete. For Emergency Spillways maintenance guidance, see Table 14.3. Table 14.3 Spillway Maintenance Required Action Maintenance Objective Frequency of Action Inspections Annually, and after any rain event that results in flow through the emergency spillway. Vegetation For a vegetated spillway the objective is to maintain a Mow grass at least Management healthy grass cover free of trees and brush twice during both • Mow grass to a height of 6 to 8 inches. growing seasons and • Remove all trees and brush from spillway. When once during the removing trees and brush, extract as much of the summer. root as possible. • Fertilize, lime, or treat with pesticide or herbicide when needed to maintain grass health (do not over fertilize). • Reseed spillway as necessary to maintain vegetation. Avoid over -fertilization. Slope, Embankment, Repair any damage to outlet. As needed based on and Outlet damage observed during Stabilization routine inspections Debris and Litter Keep the emergency spillway clear of debris and litter. During inspections or Control mowing Mechanical Not applicable Not applicable. Components Insect Control Not applicable Not applicable Access Road and Remove woody plants and maintain surface in drivable Annually Area Maintenance condition Sediment and Not applicable Not applicable Pollutant Removal Component Repair Repair slopes and protective linings as needed. Infrequently and Replacement COUNTY OF ROANOKE MARCH 22, 2016 14-8 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.4 Sediment Forebay A sediment forebay is used as a pretreatment device to allow sediment to settle from the incoming stormwater runoff before it enters the balance of the BMP. A sediment forebay helps to isolate the sediment deposition in an accessible area, which facilitates BMP maintenance. For Sediment Forebay maintenance guidance, see Table 14.4. Table 14.4 Sediment Forebay Maintenance Required Action Maintenance Objective Frequency of Action Inspections Observe depth of sediment deposition Annually Vegetation Not applicable Not applicable Management Slope, Embankment, Not applicable Not applicable and Outlet Stabilization Debris and Litter Remove debris and litter that accumulates in the During inspections or Control sediment forebay as needed intermittently Mechanical Not applicable Not applicable Components Insect Control Not applicable Not applicable Access Road and Remove woody plants and maintain surface in Annually Area Maintenance drivable condition Sediment and Remove accumulated sediment. Dispose of Generally every 3 — 5 Pollutant Removal sediments in an upland area and stabilize with years or when 6 — 12 vegetation. If necessary, obtain erosion and inches of sediment sediment control permit, prior to performing land has accumulated. disturbance. Component Repair Not applicable Not applicable and Replacement COUNTY OF ROANOKE MARCH 22, 2016 14-9 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.5 Landscaping Landscaping is an integral part of many BMP's. It is important that the landscaping thrive in order for it to fully function for pollutant uptake and ground stabilization. For Landscaping maintenance guidance, see Table 14.5. Table 14.5 Landscaping Maintenance Required Action Maintenance Objective Frequency of Action Inspections Observe landscaping growing conditions. If Monthly during the first landscaping is not thriving, correct conditions by growing season. applying fertilization, pesticide, herbicide, or Annually, in the fall, soil amendment. thereafter. Vegetation Each site shall have a site specific landscape Varies. Different plant Management maintenance schedule, depending on the species communities will used, that includes guidance regarding methods, require different levels frequency, and time of year for landscape of maintenance. maintenance and fertilization. Slope, Embankment, Not applicable Not applicable and Outlet Stabilization Debris and Litter Remove debris and litter. During inspections or as Control needed intermittently during vegetation management. Mechanical Not applicable Not applicable Components Insect Control Not applicable Not applicable Access Road and Not applicable Not applicable Area Maintenance Sediment and Not applicable Not applicable Pollutant Removal Component Repair Provide reinforcement planting after the first As needed based on and Replacement growing season, if necessary. Thereafter, observation during replace landscaping that dies or fails to thrive. inspections COUNTY OF ROANOKE MARCH 22, 2016 14-10 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.6 Stormwater Detention and Retention Basins For the design of basins see VA BMP Clearinghouse specifications. For maintenance guidance of stormwater basins, refer to the maintenance guidance for Earthen Embankments, Principal Spillways, Emergency Spillways, Sediment Forebay, and Landscaping contained in this chapter. For additional maintenance guidance for basins, see Table 14.6. Table 14.6 Basins Maintenance (i) Required Action Maintenance Objective Frequency of Action Inspections (1) (1) Vegetation (1) (1) Management Slope, Embankment, (1) (1) and Outlet Stabilization Debris and Litter Keep the embankment clear of debris During inspections or mowing Control and litter Mechanical (1) (1) Components Insect Control (1) (1) Access Road and (1) (1) Area Maintenance Sediment and (1), also remove accumulated sediment (1), Depending on the Pollutant Removal from basin area. Dispose of sediments effectiveness of the sediment in an upland area and stabilize with forebay and the condition of the vegetation. If necessary, obtain erosion watershed, sediment removal and sediment control permit, prior to from the basin may be required performing land disturbance. every 5 — 10 years. Component Repair (1) (1) and Replacement (1) Refer to the maintenance guidelines for Earthen Embankments, Principal Spillways, Emergency Spillways, Sediment Forebay, and Landscaping contained in this chapter. COUNTY OF ROANOKE MARCH 22, 2016 14-11 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.7 Constructed Wetlands For use of constructed wetlands as a BMP, see VA BMP Clearinghouse specifications.. For constructed wetlands maintenance guidance, refer to the maintenance guidance for Earthen Embankments, Principal Spillways, Emergency Spillways, Sediment Forebay, and Landscaping contained in this chapter. For additional maintenance guidance for constructed wetlands, see Table 14.7. Table 14.7 Constructed Wetlands( ) Required Action Maintenance Objective Frequency of Action Inspections (1), Document plant species distribution (1), Inspect at least and fatality rates and verify compliance semiannually for the first 3 - with landscaping requirements; years. document sediment accumulations, water elevations, and condition of the outlet. Vegetation (1) (1) Management Slope, Embankment, (1) (1) and Outlet Stabilization Debris and Litter Keep the embankment clear of debris During inspections or as needed Control and litter intermittently Mechanical (1) (1) Components Insect Control (1) (1) Access Road and (1) (1) Area Maintenance Sediment and (1), As necessary, remove accumulated (1), Depending on the Pollutant Removal sediment from constructed wetland area effectiveness of the sediment and re-establish vegetation. Dispose of forebay and the condition of the sediments in an upland area and watershed, sediment removal stabilize with vegetation. If necessary, from the constructed wetland obtain erosion and sediment control may be required infrequently permit, prior to performing land (every 10 years or less disturbance. frequent). Component Repair (1) (1) and Replacement (1) Refer to the maintenance guidelines for Earthen Embankments, Principal Spillways, Emergency Spillways, Sediment Forebay, and Landscaping contained in this chapter. COUNTY OF ROANOKE MARCH 22, 2016 14-12 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.8 Infiltration Practices For the design of infiltration basins and infiltration trenches as BMPs see VA BMP Clearinghouse specifications. 14.3.8.1 Infiltration Basin For Infiltration Basin maintenance guidance, refer to the maintenance guidance for Earthen Embankments, Principal Spillways, Emergency Spillways, Sediment Forebay, and Landscaping contained in this chapter. For additional maintenance guidance for infiltration basins, see Table 14.8A. Table 14.8A Infiltration Basin Maintenance �l> Required Action Maintenance Objective Frequency of Action Inspections (1), Inspect basin to ensure that the basin (1), Monthly for the first 6 - functions as designed. Examine infiltration months; and thereafter basin and outlet for clogging. Inspect for semiannually and after major erosion, slumping, excessive sedimentation rain events. levels and vegetation overgrowth. Vegetation Management (1) (1) Slope, Embankment, (1) (1) and Outlet Stabilization Debris and Litter Keep the buffer area clean to reduce litter and During inspections or Control floatables minimizing the clogging of the mowing infiltration basin. Mechanical Ensure no standing water remains in basin Repair as needed based on Components after storm events. Standing water indicates observation during infiltration is clogged. semiannual inspection. Insect Control Remove accumulated sediment in basin and Remove sediment restore filtration area. If standing water is accumulation every 2 years or present during dry weather, the infiltration when infiltration basin has basin has become clogged. standing water. Access Road and Area (1) (1) Maintenance Sediment and Pollutant Sediment shall be removed and disposed in an Depending on the Removal upland area and stabilized with vegetation effectiveness of the sediment when sediment fills the sediment reserve forebay and the condition of capacity, or when the basin loses its the watershed, sediment infiltration capacity. If necessary, obtain removal may be required erosion and sediment control permit, prior to infrequently (every 10 years performing land disturbance. Avoid or less frequent). compacting the floor of the infiltration basin. Component Repair and (1) (1) Replacement (1) Refer to the maintenance guidelines for Earthen Embankments, Principal Spillways, Emergency Spillways, Sediment Forebay, and Landscaping contained in this chapter. COUNTY OF ROANOKE MARCH 22, 2016 14-13 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.8.2 Infiltration Trench For maintenance requirements of infiltration trenches, see Table 14.8B. Table 14.813 Infiltration Trench Maintenance Required Action Maintenance Objective Frequency of Action Inspections Inspect infiltration trenches to ensure that the Quarterly inspection BMP continues to function as initially for the first year, and intended. Examine for clogging of infiltration semiannual inspection trench. Document depth of water in thereafter observation well or assessable pretreatment device to assess dewater capacity of the facility. Vegetation Buffer strips shall be mowed to 4 to 6 inches Cut grass twice during Management to limit unwanted vegetation. both growing seasons and once during the Trees shall be pruned such that the drip line summer. does not extend over the surface trench. All trees shall be removed within the trench to Prune overhanging prevent the puncture of filter fabric. trees annually. Slope, Embankment, Regrade, repair, and revegetate eroded and As needed based on and Outlet slumped buffer strips. damage observed Stabilization during inspections. Debris and Litter Keep the buffer area clean to reduce litter and During inspections or Control floatables minimizing the clogging of the mowing infiltration trench. Mechanical Not applicable. Not applicable Components Insect Control Not applicable Not applicable Access Road and Remove woody plants and maintain surface in Annually Area Maintenance drivable condition Sediment and Remove accumulated sediment in infiltration Every 2 years or when Pollutant Removal trench and restore filtration area. sediment causes infiltration trench to have standing water. Component Repair Remove and replace top 6"-12" gravel and As needed based on and Replacement filter cloth sediment barrier. observation during inspections. COUNTY OF ROANOKE MARCH 22, 2016 14-14 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.8.3 Porous Pavement For the design of porous pavement as a BMP see VA BMP Clearinghouse specifications. For maintenance requirements of porous pavement, see Table 14.8.C. Table 14.8.0 Porous Pavement Maintenance Required Action Maintenance Objective Frequency of Action Inspections Inspect pavement to ensure proper Quarterly, and after every structural operation, and that the major rain events, until permeable aspect of the pavement has performance characteristics of not become clogged with debris. the structure has been verified; Measure water depth in storage layer thereafter, annually Vegetation Not applicable Not applicable Management Slope, Embankment, Not applicable Not applicable and Outlet Stabilization Debris and Litter Vacuum clean pavement surface, Monthly Control followed by high pressure water washing. Do not use sand or other abrasives during winter weather as they will clog the surface. Mechanical Not applicable Not applicable Components Insect Control Not applicable Not applicable Access Road and Not applicable Not applicable Area Maintenance Sediment and Not applicable Not applicable Pollutant Removal Component Repair No repair is possible. If pavement Depends on frequency and and Replacement becomes clogged, complete replacement thoroughness of pavement is required. cleaning COUNTY OF ROANOKE MARCH 22, 2016 14-15 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.9 Bioretention Filter See VA BMP Clearinghouse specifications for the design of bioretention filters as BMPs. For maintenance guidance for bioretention filters, see Table 14.9. Table 14.9 Bioretention Filter Maintenance Required Action Maintenance Objective Frequency of Action Inspections Inspect filter to ensure that it continues Semiannually to function as initially intended. Observe sedimentation, standing water, and vegetation. Vegetation Provide adequate fertilization, pruning, Varies depending on plant Management and other care for landscaping. species Slope, Not applicable Not applicable Embankment, and Outlet Stabilization Debris and Litter Remove debris and litter. During inspections Control Mechanical Not applicable Not applicable Components Insect Control Not applicable Not applicable Access Road and Not applicable Not applicable Area Maintenance Sediment and Remove accumulated sediments and Annually Pollutant Removal dispose of them in an upland location and stabilize with vegetation. Component Repair Replace mulch layer. On an as needed Every 2 years for routine mulch and Replacement basis replace the planting soil and replacement. Every 5 years for vegetation to restore infiltration planting soil replacement. capacity to the underdrain. COUNTY OF ROANOKE MARCH 22, 2016 14-16 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.10 Sand Filters See VA BMP Clearinghouse specifications for the design of sand filters. For maintenance guidance for sand filters, see Table 14.10. Table 14.10 Sand Filter Maintenance Required Action Maintenance Objective Frequency of Action Inspections Monitor and document water level in filter Quarterly and after each chamber and rate of dewatering after storm major rain event for the events. first year, semiannually and after each major rain event thereafter. Vegetation Not applicable Not applicable Management Slope, Embankment, Not applicable Not applicable and Outlet Stabilization Debris and Litter Not applicable Not applicable Control Mechanical Not applicable Note applicable Components Insect Control Not applicable Not applicable Access Road and Remove woody plants and maintain surface Annually Area Maintenance in drivable condition Sediment and Pump out sedimentation chamber. If water Semiannually (midway Pollutant Removal has an oil skim, it should be removed by a between semiannual firm specializing in oil recovery and inspection events) recycling. Remove sediments and dispose of them properly in an appropriate landfill. Refill the first chamber with water to restore the water seal. Component Repair Remove and replace filter cloth and ballast Varies depending on the and Replacement gravel to restore filtering capacity when efficiency of the filter will no longer draw down within 40- pretreatment device hours. COUNTY OF ROANOKE MARCH 22, 2016 14-17 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.11 Grassed Swale See VA BMP Clearinghouse specifications for use of grassed swales as a BMP. For grassed swale maintenance guidance, see Table 14.11. Table 14.11 Grassed Swale Maintenance Required Action Maintenance Objective Frequency of Action Inspections Check for uniformity of vegetative cover or for . Weekly, until structural repair needed for concrete linings. vegetation is Check for sediment and debris accumulation and established. for erosion problems or bank sloughing. . Thereafter, semi- annually. • In addition, inspect grassed swale for damage after major rain events. Vegetation Objective is to maintain a healthy uniform Mow grass periodically. Management vegetative growth: Reseed as necessary. Use proper mowing techniques. • Mow grass to a height of 6 inches. • Collect and remove grass clippings. • Periodic weeding of invasive species and weeds. • Fertilize or treat with pesticide or herbicide when needed to maintain plant health (do not over fertilize). • Reseed and mulch any bare areas. Slope, Embankment, Regrade, repair, and revegetate eroded and As needed based on damage and Outlet slumped areas. Repair channel lining, outlet observed. Stabilization protection and rip rap where required. Debris and Litter Keep the channel clean to reduce litter and During inspections or Control floatables being washed downstream. mowing Mechanical Not applicable Not applicable Components Insect Control Not applicable Not applicable Access Road and Not applicable Not applicable Area Maintenance Sediment and Remove accumulated sediment in channels, Depends on site conditions Pollutant Removal behind check dams, and at outfalls and culverts to perform annually at a maintain flow capacity and drainage. Repair any minimum. damage that occurs during sediment removal. Component Repair Repair or replace check dams to maintain Annually or as needed and Replacement temporary ponding and to maintain filtered flow through check dams. COUNTY OF ROANOKE MARCH 22, 2016 14-18 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.12 Vegetated Filter Strip See VA BMP Clearinghouse specifications for use of vegetated filter strips as a BMP. For vegetated filter strip maintenance requirements, see Table 14.12. Table 14.12 Vegetated Filter Strip Required Action Maintenance Objective Frequency of Action Inspections Check the vegetation for uniformity of • Weekly, until vegetation is cover, sediment and debris accumulation, established. and erosion. Check for proper operation of . Thereafter, semi-annually. level spreader, if present. . In addition, inspect filter strip for damage after major rain events. Vegetation Management Objective is to maintain a healthy uniform As dictated by conditions. vegetative growth: • If the area is maintained as lawn use proper mowing techniques. Collect and remove grass clippings. • Periodic weeding of invasive species and weeds. • Periodic pruning of woody vegetation to stimulate grown. • Fertilize, lime, or treat with pesticide or herbicide when needed to maintain plant health (do not over fertilize). Slope, Embankment, Regrade, repair, and revegetate eroded As needed based on damage and Outlet Stabilization ground surface. observed during inspection Debris and Litter Keep the vegetated strip clean to reduce During inspections or mowing Control litter and floatables being washed downstream. Mechanical Not Applicable. Not Applicable. Components Insect Control Not Applicable. Not Applicable Access Road and Area Not Applicable. Not Applicable Maintenance Sediment and Pollutant Remove accumulated sediment and Depends on site conditions Removal reestablish vigorous vegetation cover. perform annually at a Dispose of sediments in an upland area and minimum. stabilize with vegetation. If necessary, obtain erosion and sediment control permit, prior to performing land disturbance. Component Repair and If level spreader is used, replace rigid lip Infrequently Replacement when necessary. COUNTY OF ROANOKE MARCH 22, 2016 14-19 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.13 Manufactured BMP Systems Several manufacturers have developed filter and screening devices which are gaining acceptability from the regulators as suitable BMPs for meeting stormwater quality requirements. These devices filter debris and sediment and other pollutants, such as metals and hydrocarbons from stormwater. Specific maintenance requirements for manufactured BMPs shall be in accordance with the manufacturer's specifications and warranty requirements. Provide the Manufacturer's specified guidelines for maintenance activities. See Table 14.13 for general maintenance guidance. Table 14.13 Manufactured BMP Maintenance Required Action Maintenance Objective Frequency of Action Inspections Inspect structure and inlets and outlets Semiannual or as specified by to ensure structural integrity and proper the manufacturer. functioning of the facility. Vegetation Not applicable Not applicable Management Slope, Embankment, Not applicable Not applicable and Outlet Stabilization Debris and Litter Remove debris and litter that interferes As needed based on impacts Control with proper operation. observed during semiannual inspection. Mechanical Provide routine maintenance to valves, Per manufacturer's Components sluice gates, pumps or other mechanical instructions. devices per manufacturer's instructions. Insect Control Not applicable Not applicable Access Road and Not applicable Not applicable Area Maintenance Sediment and Clean manufactured screen or filter Annually or as required. Pollutant Removal vault of debris, litter and floatable materials. Remove any sediment and pollutant build-up from the vault. Component Repair Repair or replace tank or vault structure As recommended by the and Replacement if leaks or cracks develop. Replace manufacturer and as needed. filtering media when necessary for proper functioning. COUNTY OF ROANOKE MARCH 22, 2016 14-20 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.14 Conservation Areas Conservation areas are naturally vegetated areas used to provide a measure of stormwater quality control as open space or forested areas. Conservation Areas should be maintained in their natural condition or can be planted to meet the VA BMP Clearinghouse specifications. Conservation areas require an easement. For Conservation Areas maintenance guidance, see Table 14.14. Table 14.14 Conservation Areas Maintenance Required Action Maintenance Objective Frequency of Action Inspections Check the vegetation for uniformity of cover . Quarterly, until vegetation and growth, sediment and debris is established. accumulation, and erosion. . Thereafter, annually. • In addition, inspect area for damage after major storm events. Vegetation Management (') Weed control to promote survival and If establishing new vegetation, rapid growth of trees and shrubs. continuous over first two years until vegetation is established. Vegetation shall be undisturbed after it has become established. Slope, Embankment, Regrade, repair, and revegetate eroded As needed, based on damage and Outlet Stabilization and slumped banks. observed during inspections. Debris and Litter Keep the area clean to reduce litter and Annually, and after major Control floatables being washed downstream. storm events, clean debris and litter which has accumulated. Mechanical Not Applicable Not applicable Components Insect Control Normally not applicable. Normally not applicable. Access Road and Area Normally not applicable. Normally not applicable. Maintenance Sediment and Pollutant Normally not applicable. If heavy Infrequent Removal accumulations of sediment occur, then either remove sediment accumulation or stabilize sediment accumulation in place with top soil and additional vegetation plantings. Component Repair and Normally not applicable. If major areas lose Rare Replacement trees due to fire, disease, or other cause, then replanting may be needed. (1) Note that most herbicides are very toxic to aquatic organisms. Follow listed instructions and never allow spray to enter waterways. (2) If maintenance work is required along the banks of jurisdictional streams or in wetlands, a permit may be required from the U.S. Army Corps of Engineers and the Virginia Department of Environmental Quality. COUNTY OF ROANOKE MARCH 22, 2016 14-21 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 14.3.15 Underground Detention Facilities Underground detention facilities are facilities that provide detention in underground pipes or chambers. For underground detention maintenance guidance, see Table 14.15. Table 14.15 Underground Detention Maintenance Required Action Maintenance Objective Frequency of Action Inspections Inspect condition of storage facility, outlet Semiannually structure, and presence of sediment and debris. Vegetation Not applicable Not applicable Management Slope, Embankment, Not applicable Not applicable and Outlet Stabilization Debris and Litter Remove debris and litter. As needed based on Control observations during semiannual inspection. Mechanical Not applicable Not applicable Components Insect Control Not applicable Not applicable Access Road and Not applicable Not applicable Area Maintenance Sediment and Remove accumulated sediments and Varies, depending on the Pollutant Removal dispose of them in an upland location and effectiveness of the stabilize with vegetation. pretreatment device. Component Repair Replace failed pipe, storage chambers, or Rare and Replacement other components. 14.4 Additional Maintenance and Repairs The routine maintenance items listed in the Maintenance Agreement are the minimum measures. If actual conditions demonstrate that additional maintenance or repairs are necessary for proper functioning of the stormwater management systems, they shall be provided by the responsible party. 14.5 Inspection and Maintenance Records COUNTY OF ROANOKE MARCH 22, 2016 14-22 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES CHAPTER 14 The responsible party or property owner shall maintain records of stormwater management facilities' inspections and maintenance activities, and submit copies to the County, when requested. 14.6 References The VA SWM Handbook and VA BMP Clearinghouse website contain information on maintenance of all VA DEQ approved nonproprietary BMPs. COUNTY OF ROANOKE MARCH 22, 2016 14-23 MAINTENANCE MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES APPENDIX 14B APPENDIX 14A MAINTENANCE AGREEMENTS Stormwater Management/BMP Facilities — Sample Maintenance Agreement can be found at http://www.roanokecountyva.gov/index.aspx?NID=331 Maintenance Agreements shall be submitted to: Department of Community Development Roanoke County Administration Center 5204 Bernard Drive P.O. Box 29800 Roanoke, VA 24018-0798 Procedures for submitting agreements: • Type all information on the agreement form. • Authorized property owner must sign form in black ink. • Signature must be properly notarized (black ink). • Attach a check for the recordation fee. • The Department of Community Development will coordinate the County Attorney and County Executive signatures, and recordation. • Maintenance agreements are required to be submitted, approved, and executed prior to the pre -construction meeting. COUNTY OF ROANOKE MARCH 22, 2016 14A-1 MAINTENANCE INSPECTION AND ENFORCEMENT Chapter 15 - Inspection and Enforcement CHAPTER 15 Inspection and enforcement can be divided into two distinct categories, construction and post - construction. Construction inspection ensures that the storm drainage systems and stormwater management facilities are constructed and installed in accordance with the approved Stormwater Management Plan. Once construction is complete, a final inspection will be conducted, and as -built documentation will be submitted to show that the constructed project meets the requirements of the approved Stormwater Management Plan. At this point, the responsibility for the operation and maintenance of the storm drainage systems and stormwater management facilities is transferred from the permittee to the property owner or responsible party. Where a project is constructed in phases, a final inspection shall be conducted of each completed phase as designated by the approved Stormwater Management Plan. The final inspection shall consist only of the phase being identified as complete. After construction is complete, the property owner or responsible party is required to conduct periodic inspections and maintenance of the stormwater management facilities. Property owner inspections and maintenance activities must be documented and maintained. The County of Roanoke will also conduct periodic post -construction compliance inspections of stormwater management facilities. 15.1 Construction Inspections Construction of storm drainage systems and stormwater management facilities shall comply with the approved final Stormwater Management Plan. Any changes to the approved design require a resubmittal to the County of Roanoke for approval. Inspections shall be performed by the permittee to ensure that construction conforms to the approved plans and specifications. Additional inspections will be performed by the County of Roanoke to confirm compliance. 15.1.1 Notifications to the County of Roanoke The permittee shall notify the County of Roanoke in advance of the start of construction and of the construction of critical components of a stormwater management facility. The following are examples of, but not limited to, critical components: • Before the start of construction; Before installing a stormwater pond embankment; Before installing pond outlet structures; COUNTY OF ROANOKE MARCH 22, 2016 15-1 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT CHAPTER 15 • Before setting any concrete BMP structures, this does not include precast drop inlets or manholes; • Before installing energy dissipation structures and any outlet structure into a jurisdictional stream (perennial or intermittent flow); • Before installing any infiltration or bioretention BMP; or • Any other key BMP component as determined by the County of Roanoke 15.1.2 Periodic Inspections The permittee is responsible to perform adequate inspection of the construction activities to confirm that the site is in compliance with the Erosion and Sediment Control Ordinance requirements and that the construction of storm drainage systems and stormwater management facilities and BMPs are in conformance with the approved Stormwater Management Plan. Upon completion of construction, the permittee must provide certification from a licensed professional that the completed project is in accordance with the approved plans and specifications and must provide documentation of regular inspections sufficient to adequately support compliance. All permittee inspections shall be documented and written reports prepared that contain the following information: • The date and location of the permittee inspection; • Whether construction is in compliance with the approved Stormwater Management Plan; • Variations from the approved construction specifications; • Corrective actions that have been taken to correct previous violations; • Any violations that exist or corrective actions that have been completed; and • The name and signature of the person who performed the inspection. The County of Roanoke shall conduct periodic inspections during construction. During the County inspection, the permittee will provide all permittee inspections which have been conducted since the last County inspection for County observation. If the County finds any violations, the permittee shall be notified in writing of the nature of the violation and of the required corrective actions. In conjunction, the County may issue an order requiring that all or part of the land disturbing activities permitted on the site be stopped until the specified corrective measures have been taken. If the County of Roanoke determines that there is a repeated failure to comply with the approved plans and specifications, enforcement action may be taken. COUNTY OF ROANOKE MARCH 22, 2016 15-2 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT CHAPTER 15 15.1.3 Final Inspection and As -Built Documentation Prior to final acceptance of the project the permittee is required to submit to the County of Roanoke as -built documentation, confirming that the storm drainage systems and stormwater management facilities and practices that have been constructed conform to the approved Stormwater Management Plan. In addition, once the as -built documentation has been submitted, a final inspection will be conducted by the County of Roanoke to confirm that the as -built documentation conforms to the actual construction. As -built documentation shall include the following: General: • As -built survey conducted following construction, sealed by a Registered Land Surveyor and/or Professional Engineer. As -built plans shall be a "redline" of the approved plans or a full size record drawing (as outlined below) and shall be to scale and provide a north arrow. • Stormwater easements and access easements shall be shown on the plans with metes and bounds. • Certification statement, signed by the permitee and a Licensed Professional indicating conformance with the approved Stormwater Management Plan (including certification to both the storm drainage and stormwater BMPs are in compliance with the approved plans). • A supplemental digital file is required for County records and shall be provided via the FTP site or on a CD-ROM made available in an AutoCAD format shown with the layer configurations described in Section 15.1.4. • The permittee's inspection log records with copies of all inspection test results documenting compliance with the approved Stormwater Management Plan. Storm Drain Systems: • All storm system structures identified and labeled the same as the approved plan. All structure elevations are to include an invert elevation, a top of grate (at grade) elevation and any opening elevations used for storm water intake purposes (NAVD 88). All data is to be verified to the closest hundredth of a foot (0.01). • All storm system pipes identified and labeled the same as the approved plan with upstream and downstream invert elevations (NAVD 88), the COUNTY OF ROANOKE MARCH 22, 2016 15-3 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT CHAPTER 15 total length of the pipe run from end to end, with the calculated slope. All data is to be verified to the closest hundredth of a foot (0.01). • Maximum tolerances shall be based upon the following: 1. Does the structure function properly (i.e. is pipe capacity greater than the calculated flow, etc)? 2. Has the proper amount of cover been provided? 3. Has a minimum as -built slope of 0.40% been provided or Q2 greater than 3 fps (whichever is more restrictive). • Redline revision of approved storm drainage profiles and horizontal layout plans for as -built storm drainages structures. . For changed values, strike thru the design value and enter the constructed value. A one page "record drawing" may be provided for the as-builts which includes the following information as a minimum: 1. Storm drainage profiles or storm drainage table which shows structure number, rim, inverts, pipe length, diameter, and slope; and 2. Horizontal layout of storm drainage on plans (plan should also show the location of buildings, edge of pavement, sidewalk, curb and gutter, property line, etc). • Label plan sheet as as -built. BMPs: Redline of approved Stormwater Management Plan for BMPs. For changed values, strike thru the design value and enter the constructed value. Provide as -built dimensions of the structures, grades, slopes, elevations, BMP components (details), etc on the plans to verify that the structure has been constructed correctly. A one page "record drawing" may be provided for the as-builts which includes the following information as a minimum: 1. Horizontal layout of BMP on plans (plan should also show the location of buildings, edge of pavement, sidewalk, curb and gutter, property line, etc); 2. As -built contours if required (i.e. bioretention); 3. Accessory structure details (i.e. berm, orifice, outlet structure, diaphragms, weirs, soil media, etc.). This should be provided with the BMP details on the as -built plan. • Update the BMP table on the plans and label as "as -built". Provide latitude and longitude of as -built BMP. • Provide available Manufacturer certification that the structure was installed correctly. COUNTY OF ROANOKE MARCII 22, 2016 15-4 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT • Label plan sheet as as -built. CHAPTER 15 A supplemental digital file is required for County records and shall be provided via the FTP site or on a CD-ROM made available in an AutoCAD format shown with the layer configurations described in Section 15.1.4. Ditch and Channel Sections: Provide ditch/channel cross-sections plotted to scale, 300 feet maximum intervals or portion thereof, minimum of 2 per ditch, with adequate spot elevations that defines the ditch section and slope as required by the approved plan. The Engineer shall show the location on the swale where the cross section is being provided. • Cross sections are to be shown and labeled on the plan. Ponds: Maximum tolerances shall be based upon the following: 1. Does the structure function properly (i.e. is swale capacity greater than the calculated flow, etc)? 2. Has the proper amount of depth/freeboard been provided? 3. Has a minimum as -built slope of 2.0% been provided vegetated swales or 1.0% for riprap or concrete lined channels? 4. Has the maximum allowable velocity for the channel lining been exceeded? A supplemental digital file is required for County records and shall be provided via the FTP site or on a CD-ROM made available in an AutoCAD format shown with the layer configurations described in Section 15.1.4. Redline of approved Stormwater Management Plan for ponds. For changed values, strike thru the design value and enter the constructed value. Provide as -built dimensions of the structures, pipe slopes, berms elevations, pond structure components (details), etc on the plans to verify that the structure has been constructed correctly. A one page "record drawing" may be provided for the as-builts which includes the following information as a minimum: 1. Horizontal layout of pond on plans (plan should also show the location of buildings, edge of pavement, sidewalk, curb and gutter, property line, etc); 2. As -built contours; 3. Accessory structure details (i.e. berm, orifice, outlet structure, weirs, etc.). This should be provided with the pond details on the as -built plan. COUNTY OF ROANOKE MARCII 22, 2016 15-5 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT CHAPTER 15 The survey shall include enough information to verify that storage capacities are no less than the storage volume required by the approved Stormwater Management Plan. For retention and detention structures, a stage -storage summary table with design values and as -built values shall be included. The survey shall verify inverts and sizes of pipes, culverts, and outlet structures. • Show location of and label elevations and width of berm. • Show location and label dimension and elevations of spillways. • Label plan sheet as as -built. • A supplemental digital file is required for County records and shall be provided via the FTP site or on a CD-ROM made available in an AutoCAD format shown with the layer configurations described in Section 15.1.4. If it is determined from the as -built documentation that the storm drainage systems or the stormwater management BMP facilities have not been constructed in accordance with the approved Stormwater Management Plan, then corrective action will be taken to comply with the approved Plan or the permittee shall provide studies and information required by the County of Roanoke to demonstrate that the constructed systems will function equivalent to the approved Stormwater Management Plan. This includes meeting all flow, velocity, and regulatory requirements and that the approved elevation -storage requirement is maintained. Once the as -built documentation has been accepted by the County of Roanoke, the permittee shall schedule a final inspection of the project site prior to final acceptance of the project by the County and the return of performance bonds or securities. The permittee shall provide 48 hour notice of a final inspection to the County of Roanoke. 15.1.4 ACAD Digital File Requirements The following items shall be submitted in ACAD format with the as-builts. All items shall be tied to the State Plane Coordinate and NAVD 88. All items shall be set to an elevation of zero, unless otherwise noted. All items (storm, topo, pavement, etc.) shall be submitted on a standalone layer (applicably named) so that information can correctly incorporated in to County GIS. Storm drainage pipe and structures. Structures shall be shown at their as - built location. COUNTY OF ROANOKE MARCH 22, 2016 15-6 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT CHAPTER 15 • Stormwater BMPs shown at the as -built location. BMPs shall be labeled to match the plans. Ponds, swales, infiltration basins, etc shall provide as - built contours and have applicable elevation assigned to the line work. • Proposed topographic contours inside the site property boundary for the approved project. These contours are the line work as shown on the approved plans and are not as -built contours, but line work from the CAD drawings. Elevations shall be assigned to the line work. • Easements and right-of-ways. • Property lot lines. • Edge of pavement. • Building layout. 15.2 Post -Construction Inspections and Maintenance The property owner or responsible party is responsible for the proper operation, inspection, maintenance, and repair of stormwater management facilities, after the completion of construction, in accordance with the applicable maintenance agreement. All inspection, maintenance, and repair activities shall be documented. The responsible party shall inspect and maintain stormwater management facilities at the frequencies listed in the Maintenance Agreement. In addition to the inspections performed by the responsible party, each stormwater management facility will be inspected periodically by the County of Roanoke. In the event that the stormwater management facility has not been maintained and/or becomes a danger to public safety, public health, or the environment, the County of Roanoke shall notify the property owner, or responsible party, by registered or certified mail and issue a Notice of Violation. The Notice shall specify the measures needed to correct the situation and shall specify the time within which such measures must be completed. If the responsible party fails or refuses to meet the requirements of the maintenance agreement, the County of Roanoke, after reasonable notice, may apply a civil or criminal penalty and may correct a violation of the design standards or maintenance needs by performing all necessary work to place the facility in proper working condition, and recover the costs from the responsible party or property owner. 15.3 Records Parties responsible for the operation and maintenance of a stormwater management facility shall make records of the installation and of all inspections, maintenance and repairs, and shall retain the records for at least five (5) years. These records shall be made available to the County of Roanoke upon request. Examples of inspection records can be found on the BMP Clearinghouse website, in Appendix 15A, or obtained from Manufacturer literature. COUNTY OF ROANOKE MARCH 22, 2016 15-7 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT 15.4 Enforcement CHAPTER 15 Any activity that is commenced without an approved Stormwater Management Plan, or is conducted contrary to the approved Stormwater Management Plan, may be subject to the enforcement actions outlined in the County of Roanoke Stormwater Management Ordinance. A property owner or responsible party that does not properly maintain a stormwater management facility in accordance with the maintenance agreement may be subject to the enforcement actions outlined in the County of Roanoke Stormwater Management Ordinance. 15.4.1 Notice of Violation When a County of Roanoke inspection has noted that a construction activity or maintenance of a stormwater management facility is not in compliance with the approved Stormwater Management Plan, including all maintenance agreements, or the County of Roanoke Stormwater Management Ordinance, the County shall issue a written notice of violation delivered by registered or certified mail to the permittee or property owner. The notice of violation shall include: • The name and address of the responsible party; • The address when available or a description of the building, structure or land upon which the violation is occurring; • A statement specifying the nature of the violation; • A description of the remedial measures necessary to correct the violation and a time schedule for the completion of such remedial action; • A statement of the penalty or penalties that may be assessed against the person to whom the notice of violation is directed, should the remedial measures not be implemented; • A statement that the determination of violation may be appealed by filing a written notice of appeal within 30 days of service of notice of violation. 15.4.2 Stop Work Orders If a project site is under construction and receives a notice of violation, construction activities in the area where the work was found to be deficient in meeting the approved Stormwater Management Plan shall cease immediately. COUNTY OF ROANOKE MARCH 22, 2016 15-8 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT CHAPTER 15 The stop work order will be in effect until the County of Roanoke confirms that the land disturbing activity is in compliance with the approved Stormwater Management Plan. The permittee shall address the remedial measures published with the notice of violation within the time period specified. Upon completion of the remedial measures, the County of Roanoke shall inspect the work and authorize the permittee in writing that the stop work order has been removed and work may continue in that area of the project. Failure to comply with a stop work order or with a notice of violation may result in the revocation of the permit and the violator shall be subject to the penalties set forth by the Stormwater Management Ordinance. 15.4.3 Restoration of Lands Any violator may be required to restore land to its undisturbed condition in accordance with a notice of violation, stop work order, or permit requirements. In the event that restoration is not undertaken within the time specified in the notice, the County of Roanoke may take necessary corrective action, the cost of which shall be covered by the performance bond, or become a lien upon the property until paid, or both. COUNTY OF ROANOKE MARCH 22, 2016 15-9 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT APPENDIX 15A INSPECTION FORMS Stormwater Management Construction Inspection Checklist Stormwater Management Facilities Inspection Report Form APPENDIX 15A Stormwater Management Facilities Maintenance/Repair Report Form COUNTY OF ROANOKE MARCH 22, 2016 15A-1 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT Inspector Name: Permittee's Name: Site Address or Location: Watershed: Reason for Inspection: ❑Routine Inspection ❑Complaint Stormwater Management Construction Inspection Checklist Inspection Date: Permit Number: Tax Map or Parcel ID No: ❑Intensive Rainfall ❑Other APPENDIX 15A Disturbed Area (at time of inspection): Does the Site Require: ❑Erosion and Sediment Control Plan ❑Stormwater Pollution Prevention Plan ❑SPCC Plan (oil storage) ❑Other If required, are these plans or permits available on-site? Erosion and Sediment Control Item Used Acceptable Condition Observations and Actions Required Completion Date Silt Fence YE] NE] YE] NE] Straw Bales Y ❑ N ❑ Y ❑ N ❑ Inlet Protection Y ❑ N ❑ Y ❑ N ❑ Stabilized Construction Entrance Y ❑ N ❑ Y ❑ N ❑ Sediment Trap/Basin Y ❑ N ❑ Y ❑ N ❑ Check Dams Y ❑ N ❑ Y ❑ N ❑ Seeding (Temporary or Final) Y ❑ N ❑ Y ❑ N ❑ Other: Y❑N❑ Y❑N❑ Y❑N❑ Y❑N❑ YE] NE] YE] NE] YE] NE] YE] NE] Page 1 of 2 COUNTY OF ROANOKE MARCH 22, 2016 15A-2 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT Stormwater Collection and Transport (Culverts, Storm Drains, and Inlets) APPENDIX 15A Item Constructed as Approved? Discrepancies and Corrections Completion Date Y ❑ N ❑ Y ❑ N ❑ Y ❑ N ❑ Y ❑ N ❑ Y ❑ N ❑ Y ❑ N ❑ Y ❑ N ❑ Y ❑ N ❑ Discharge Outfall from Development Adequate channel: Y ❑ N ❑ Signature of Inspector Page 2 of 2 COUNTY OF ROANOKE MARCH 22, 2016 15A-3 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT APPENDIX 15A Item Inspected Checked Maintenance Observations and Remarks Yes No Reqd. Not Req. Culverts and Storm Drains Is the culvert or storm drain filled more than 25% with debris, sediment, or trash? Is there evidence of structural 1:1 El failure of the culvert pipe? Is there evidence of erosion at the inlet and outlet of the culvert or at the storm drain inlet? Are there signs of settling, cracking, or misalignment of ❑ ❑ ❑ ❑ culverts, storm drain pipe, or concrete inlets? Stormwater Ponds (see also Embankments) Is the emergency spillway clear of obstructions, debris, and El vegetation? Is the outlet structure and pipe clean of debris and sediment, free ❑ of damage, and in working order? Is there an accumulation of debris, litter or trash? (For dry detention ponds) Is there El standing water in the pond? (For wet ponds) Is their excessive algae growth or other vegetation? Is there evidence of oil or other 1:1pollutants El 1:1 in the pond? Is there erosion at the discharge point? Do any safety devices, fences, ❑ ❑ Ll gates, or locks need repair? Page 1 of 1 COUNTY OF ROANOKE MARCH 22, 2016 15A-4 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT APPENDIX 15A STORMWATER MANAGEMENT BMP FACILITIES INSPECTION REPORT FORM Inspection Requirements: See the Stormwater Management BMP Facilities Maintenance Schedule for landowner's responsibilities for frequency of inspection and other requirements. This information is a part of the Maintenance Agreement that is recorded in the land records with the deed. Inspection Purpose: To assure safe and proper functioning of the stormwater management BMP facilities and associated structures, by providing regular observations of their conditions and operation. Retention of Records: All inspection/maintenance/repair documentation shall be retained by the landowner for a minimum of five (5) years. Submission of Records: At the end of each year, by December 31", mail all BMP inspection and maintenance documentation to: County of Roanoke Department of Community Development 5204 Bernard Drive Roanoke, Virginia 24018 Attention: Stormwater Program Manager (BMP Inspection and Maintenance Records) NAME OF BUSINESS OR LANDOWNER: ADDRESS: INSPECTION DATE: PERFORMED BY: Facility Management Checklist The following items should be checked for each BMP: 1. Facility construction meets the requirements of the Roanoke County Stormwater Management Design Manual, where applicable, and is adequate for the intended function. 2. The facility has been maintained properly according to the requirements of the Recorded Maintenance Agreement, BMP Maintenance Schedule, and the Roanoke County Stormwater Management Design Manual. 3. The facility is functioning adequately. 4. There have been no changes to the site conditions or area that would require modification and/or replacement of the existing facilities. 5. Access to the facility is adequate and maintained. Sheet 1 of COUNTY OF ROANOKE MARCH 22, 2016 15A-5 INSPECTION AND ENFORCEMENT INSPECTION AND ENFORCEMENT APPENDIX 15A STORMWATER MANAGEMENT BMP FACILITIES MAINTENANCE/REPAIR REPORT FORM Maintenance Requirements: Refer to the site's Stormwater Management BMP Facilities Maintenance Schedule for landowner's responsibilities for frequency of maintenance and other requirements. This Maintenance Schedule is a guideline of minimum maintenance requirements. Additional maintenance shall be performed as necessary for the proper functioning of Stormwater Management BMP facilities. This information is a part of the Maintenance Agreement that is recorded in the land records with the deed Maintenance Purpose: To enable the proper long-term functioning of the stormwater management BMP facilities to protect the Valley's water quality and prevent downstream flooding. Retention of Records: All inspection/maintenance/repair documentation shall be retained for a minimum of five (5) years. Submission of Records: At the end of each year, by December 31st, mail all BMP inspection and maintenance documentation to: County of Roanoke Department of Community Development 5204 Bernard Drive Roanoke, Virginia 24018 Attention: Stormwater Program Manager (BMP Inspection and Maintenance Records) NAME OF BUSINESS OR LANDOWNER ADDRESS: MAINTENANCE/REPAIR DATE: PERFORMED BY: GENERAL COMMENTS: Sheet 1 of COUNTY OF ROANOKE MARCH 22, 2016 15A-6 INSPECTION AND ENFORCEMENT ACTION NO. A-032216-3 ITEM NO. E-3 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER MEETING DATE: March 22, 2016 AGENDA ITEM: Request for authorization to execute a contract of sale and development agreement between the County of Roanoke, the Roanoke County Economic Development Authority and Waukeshaw Development, Inc. SUBMITTED BY: Jill Loope Director of Economic Development APPROVED BY: Thomas C. Gates County Administrator COUNTY ADMINISTRATOR'S COMMENTS: SUMMARY OF INFORMATION: In May of 2014, Roanoke County advertised a Request for Proposals for the sale and redevelopment of the former William Byrd building located in the Town of Vinton. The County received and accepted a proposal from Waukeshaw Development, Inc. to purchase and redevelop the facility into a mixed-use residential development. The proposed project includes the establishment of more than seventy (70) market rate apartments, consisting of one (1) and two (2) bedrooms, at a density determined through the zoning and design process. The projected investment for the redevelopment of the property is estimated at $9.2 million. The William Byrd building was constructed in 1930, and was used as an educational and vocational training facility from 1930-2010. The two (2) -story main building consists of 62,760 sq. ft. with an adjoining annex building consisting of 6,980 sq. ft. The property includes 6.494 acres, within walking distance to downtown Vinton. The property represents a unique opportunity for redevelopment as a mixed use residential and commercial project. To facilitate the redevelopment and historic preservation of the building, the County will submit an application to the Virginia Department of Historic Resources to pre -determine the facility's eligibility for inclusion in the National Register of Historic Places and the Virginia Landmarks Register. Page 1 of 3 To assist with the project, a three (3) -party performance agreement has been negotiated between Roanoke County, the Roanoke County Economic Development Authority and Waukeshaw Development, Inc. This agreement will assist the developerwith complex site and building re -development and infrastructure related costs, while providing new capital investment in Roanoke County and the Town of Vinton. The agreement allows for the sale of the property for ten dollars ($10) and an economic development grant in an amount equal to ten (10) years of new local tax revenue to be reimbursed to the company. New local tax revenue is defined as net new real estate taxes generated by the project. The total amount of the grant shall not exceed $1,000,000 over a ten (10) year period. If the development generates less than the estimated new local tax revenue, then the actual grant for that year shall be less. The ten (10) year period will commence on January 1, 2018. FISCAL IMPACT: Per the performance agreement, the grant will be calculated as a reimbursement based on new tax revenues generated by the project therefore the fiscal impact will be in the form of foregone revenue. ALTERNATIVES: 1) Adopt the contract of sale and development agreement and authorize the County Administrator, or any Assistant County Administrator, to execute the contract between the County of Roanoke, the Roanoke County Economic Development Authority and Waukeshaw Development, LLC. 2) Decline to adopt the contract STAFF RECOMMENDATION: Staff recommends approval of Alternative 1. Page 2 of 3 VOTE: Supervisor Peters moved to adopt the attached contract of sale and development agreement and authorized the County Administrator, or any Assistant County Administrator, to execute the contract between the County of Roanoke, The Roanoke County Economic Development Authority and Waukeshaw Development, LLC; Supervisor Hooker seconded the motion. Motion approved. cc: Jill Loope, Director of Economic Development Ruth Ellen Kuhnel, County Attorney Page 3 of 3 Yes No Absent Mr. Assaid ® ❑ ❑ Mr. Bedrosian ® ❑ ❑ Ms. Hooker ® ❑ ❑ Mr. McNamara ® ❑ ❑ Mr. Peters ® ❑ ❑ cc: Jill Loope, Director of Economic Development Ruth Ellen Kuhnel, County Attorney Page 3 of 3 CONTRACT OF SALE THIS CONTRACT OF SALE (the "Contract"), made this day of 2016, between ROANOKE COUNTY BOARD OF SUPERVISORS, a political subdivision of the Commonwealth of Virginia (the "Seller"), and WAUKESHAW DEVELOPMENT, INC., a Virginia corporation (the "Buyer") and/or its assigns. WITNESSETH: WHEREAS, the Buyer desires to purchase from the Seller the following properties (the "Property") to wit: Property Address: 100 Highland Road, Vinton, VA 24179 Property Parcel ID: 060.11-04-20.00-0000 Properly Description: Old William Byrd High School and associated acreage; and further described as lot B 1 consisting of 6.494 acres, as shown on the Resubdivision Plat for County School Board of Roanoke County and instrument #201212052 WHEREAS, the Seller hereby agrees to bargain, sell, and convey the Property to Buyer for redevelopment to residential and commercial uses (the "Project"). 1. Grant of Contract. The purchase price of the Property shall be for the sum of ten dollars and 00/100 cents ($10.00). The Buyer shall place into escrow with the Seller's agent a deposit of ten dollars and 00/100 cents ($10.00) (the "Deposit") upon execution of this Contract. 2. Term of Contract. The Buyer shall have six (6) months from the Contract execution date to perform necessary due diligence (the "Due Diligence Period") and to determine that the Property is suitable for Buyer's intended use. The Due Diligence Period may be extended for an additional twelve (12) months. To accommodate the Property's inclusion on the National Register of Historic Places, to allow for any necessary rezoning of the Property, and to allow the Buyer to seek financing for the Project. The Buyer shall exercise the extension by written notice to Seller prior to expiration of the original term. The results of said Due Diligence Period are to be satisfactory to the Buyer at the Buyer's sole discretion; otherwise, the Deposit shall be refunded in full. During the Due Diligence Period, the Buyer, its agents, employees, representatives, and contractors, at Buyer's sole cost and expense, may perform such tests, inspections, and examinations of the Property as the Buyer deems advisable, including without limitation investigations with regard to title, physical condition, environmental matters, matters of survey, flood plain, utilities availability, zoning and building code, and other applicable governmental requirements, financing requirements, and development requirements. The Buyer shall not damage or alter the Property while conducting its inspections, tests, and studies. Seller shall grant the Buyer, its agents, or assigns free access to the Property for such purposes. Page 1 of 16 3. Closing of Contract. This Contract is void if closing on this Contract ("Closing") does not occur on or before 12:00 p.m. on the last day of the Due Diligence Period, or any extension thereof. Closing shall be at a location selected by the Buyer, on or before 12:00 p.m. on the last day of the Due Diligence Period, or any extension thereof. 4. Obligations of the Parties. If the Buyer agrees to the stipulations as hereinabove set forth, the parties shall perform their respective obligations as follows: A. Obligations of the SELLER i. Seller will use its best efforts to affirmatively assist Buyer in obtaining ratification by the County of Roanoke of the Development Agreement (the "Development Agreement") in the form set forth in Exhibit "B" attached hereto and incorporated herein or in any other form approved by Buyer. Buyer and Seller agree that this Contract will not be considered fully - executed nor enforceable until the Development Agreement has been executed by both Buyer and the County of Roanoke. ii. Within five (5) days of the execution of this Contract, Seller will provide Buyer with copies of any and all available Property due diligence items requested by the Buyer and are within the Seller's possession. These include, but are not limited to, any existing surveys and plats of the Property, any photos and building plans, historic or otherwise, any environmental studies or written communiques with the Environmental Protection Agency ("EPA"), the Virginia Department of Environmental Quality ("DEQ"), or any other governmental agency, any Phase 1 or 2 environmental reports, the title commitment or policy for the Property, and any physical inspections reports or warranties such as roof and HVAC. iii. Within five (5) days of the execution of this Contract, Seller will provide Buyer with all keys, codes, or other security devices, if any, used in connection with access to the Property. iv. Seller agrees that it will be an applicant or co -applicant, as described in the Development Agreement, on project grant applications, if any, and will coordinate with Buyer to the extent necessary to accomplish the same. v. Seller agrees to act as the applicant, during the Due Diligence Period, for "Part 1" and "Part 2" applications to both the Virginia Department of Historic Resources and the National Park Service, to work with the Buyer's historic consultant to complete and submit those applications, and to pay for the fees associated with those applications. Should the Project not move forward, the intellectual property contained within those applications will remain the property of Seller. Page 2 of 16 vi. Seller agrees that it will be a co -applicant on the rezoning application within one hundred and twenty (120) days of the execution of this Contract and further agrees to cooperate and facilitate the rezoning of the Property to a zoning classification approved by the Buyer (Mixed -Use Development ["MUD"] zoning). The Buyer acknowledges that the rezoning of the property remains under the legislative discretion of the Town of Vinton. vii. Seller shall pay the fees and expenses of its legal counsel viii. Seller will provide, at its cost and expense, an American Land Title Association ("ALTA") and topographic survey for the Property within the first thirty (30) days of the Due Diligence Period and assign the survey files (digital ".dwg" files and hard -copy) to the Buyer, with all rights associated with the same and title search information. ix. Within thirty (30) days of the execution of this Contract, Seller will provide, at its cost and expense, a current Phase 1 Environmental Site Assessment ("ESA") report of the Property to Buyer, which must also include a lead and asbestos survey of the Property. x. Seller shall continue to maintain in full force and effect such casualty and liability insurance on or with respect to the Property as it maintains in the ordinary course of business, it being understood and agreed that all risk of loss with respect to the Property, except as may be caused by the acts or omissions of Buyer or its employees, agents, or contractors, shall remain with Seller through Closing. In the event that, prior to Closing, the improvements on the Property are materially damaged, destroyed, or rendered unusable by fire, casualty, or other cause, then Buyer may, at its option, terminate this Contract, and the Deposit shall be refunded to Buyer, or upon mutual agreement of the parties, the Buyer may affirm the contract, in which event the Buyer shall be entitled to the insurance proceeds solely applicable to the Project expenses. . xi. Seller shall use good faith efforts to seek all approvals, votes, and ordinances that are required under applicable law for the sale of municipal property, including those set forth in Virginia Code Sections 15.2-1800 et seq. and 15.2210 et seq. B. Obligations of the BUYER i. Buyer will convert the building to market rate apartments, at a density and unit mix to be determined by the Town of Vinton's zoning requirements and Buyer's sole discretion, comprising one- and two-bedroom apartments Page 3 of 16 and the potential for other commercial components if determined to be appropriate. ii. Buyer shall perform necessary due diligence to determine that Property is suitable for Buyer's intended use. iii. Buyer shall pursue state and federal government approvals relating to the issuance of both federal and state historic rehabilitation tax credits. The Buyer's obligations to purchase the Property are contingent upon these state government and federal government approvals relating to the issuance of both federal and state historic rehabilitation tax credits. iv. Buyer shall pay all fees and expenses of Buyer's legal counsel to the extent not paid prior to Closing. v. Buyer shall provide reasonably detailed status reports in writing to Seller every ninety (90) days during the Due Diligence Period prior to Closing. Such reports shall describe Buyer's due diligence inspections and results as well as Buyer's efforts to obtain financing. vi. Buyer agrees to act as the lead applicant for the rezoning of the property and will initiate and prepare all documents necessary to complete the Proj ect. vii. Closing of the construction financing and the real estate transaction will occur simultaneously. viii. Buyer agrees to provide an additional guarantee as security for the Buyer's compliance with the terms or conditions of this Development Agreement in the form of a cash escrow account in the amount of $200,000 made payable to the Seller or Authority. This security shall be deposited upon receipt of historic preservation certification and before commencing any renovation or construction work on the Property. 5. Real Estate Commission. Seller represents and warrants to Buyer, and Buyer represents and warrants to Seller, that each engaged no real estate broker, salesperson, or other intermediary to assist in the transfer of the Property from Seller to Buyer. 6. Representations and Warranties. Buyer hereby agrees to indemnify, defend, and hold Seller harmless from and against any claim arising out of a breach of the representations and warranties in this Contract. The representations, warranties, and indemnities of Buyer and Seller under this Contract shall survive Closing and delivery of the Deed or the termination of this Contract for any reason. A. Buyer accepts that the property will convey in "as is, where is" condition with all faults, and that Seller makes no representation or warranty whatsoever, whether express, implied, or arising by operation of law, with respect to the Property or Page 4 of 16 any portion, aspect, or component thereof, and expressly disclaims the same. Likewise, Seller makes no representation or warranty whatsoever, whether express, implied, or arising by operation of law, with respect to any documents, reports, or materials provided or made available to Buyer by Seller or its agents, or the accuracy of the information contained therein, and expressly disclaims the same. The foregoing disclaimers include, but are not limited to, matters of title, survey, financial performance, physical condition (including, without limitation, environmental condition or presence or absence of hazardous substances), zoning, tax status or consequences, fitness for a particular purpose or use, compliance with governmental requirements, access to the Property, and availability of utilities. 7. Termination of Contract. Buyer may terminate this Contract by giving Seller written notice of termination at any time prior to the expiration of the Due Diligence Period, or any extension thereof, if the results of such inspections are not satisfactory to Buyer, as foresaid. Buyer will commence such inspections forthwith upon execution of this Contract. If Buyer fails to give Seller such written notice of termination before the expiration of the Due Diligence Period, or any extension thereof, then, and in such event, the Buyer shall be deemed to have accepted the results of such inspections and shall proceed to Closing in accordance with the terms of the Contract. The Buyer may reserve the right to proceed to Closing sooner than the expiration of the Due Diligence Period provided the inspections are complete. In the event that this Contract is terminated before the Closing, neither Buyer nor Seller shall have any obligation to the other, and each party shall then be responsible for its own expenses, including, but not limited to, legal fees and expenses incurred in connection herewith. Seller shall pay for preparation of the Deed for the Property, which shall be a Special Warranty Deed, and shall pay any grantor's taxes that are imposed thereon. Buyer shall pay all other recording taxes and will accept and comply with the terms of said sale as herein set forth, provided the title is marketable. 8. Possession of Property. This sale is made subject to restrictions, covenants, agreements, and easements of record and existing leases. In this regard, Seller states that there are no outstanding lease agreements as of the execution date of this Contract. This sale is conditioned upon the improvements on the Property being in substantially the same condition on the date of Closing as the same are in on the date of this Contract. Risk of loss or damage to the Property shall be the responsibility of the Seller until final Closing is made, except that the Buyer shall have the right, at its sole discretion, to terminate this Contract at any time before the expiration of the Due Diligence Period, or any extension thereof, if the Property is substantially and/or materially damaged by an act of God or otherwise. If said casualty occurs, the Seller shall notify the Buyer by certified mail within ten (10) days of said occurrence and refund the Deposit to the Buyer, and each party shall have no further actions against one another is any court of competent jurisdiction for any and all fees, fines, penalties, liability, or expenses of or related to zoning this Property. Actual possession is subject to rights of tenants, if any, under existing leases. All rents, taxes, and other pro ratable items shall be prorated as of the Closing date. Page 5 of 16 9. Miscellaneous: A. Buyer may assign this Contract at its sole and absolute discretion to an entity created and controlled by Buyer to construct the Project. B. The paragraph headings appearing in this Contract are for reference purposes and shall not be considered a part of this Contract or in any way to modify, amend, or affect the provisions hereof. C. This Contract is a Virginia contract and represents the final understanding between Buyer and Seller with respect to the transaction described herein, there being no representations or agreements made by seller or Buyer, except those contained in this Contract and its addendums. In addition, this Contract constitutes the entire understanding among the parties, and shall be deemed to supersede all prior written or verbal communications among the parties. This Contract may not be modified or terminated, unless in writing signed by the Buyer and Seller. D. This Contract and the provisions hereof shall be binding upon and shall inure to the benefit of the Seller and Buyer and its respective heirs, executors, administrators, personal representatives, successors, and assigns. This Contract shall be freely assignable by the Buyer on or after the date hereof. The terms, provisions, and conditions of this Contract shall, where appropriate or the context requires, survive Closing hereunder. WITNESS the following signatures and seals as of the date first above written: SELLER: Thomas c. Gates, County Administrator DATE BUYER: WAUKESHAW DEVELOPMENT, INC. DATE Page 6 of 16 State/Commonwealth of County of I, , do certify that the foregoing Contract of Sale was acknowledged before me this day of 2016 by of Waukeshaw Development, Inc., a Virginia corporation, on behalf of the corporation. He/she is personally known to me or has produced identification. Notary Public Registration Number: My commission expires: State/Commonwealth of County of I, , do certify that the foregoing Contract of Sale was acknowledged before me this day of 2016 by Thomas C. Gates, County Administrator Roanoke County, a political subdivision of the Commonwealth of Virginia, on behalf of the Board. He/she is personally known to me or has produced identification. Notary Public Registration Number: My commission expires: Page 7 of 16 EXHIBIT "A" TO PURCHASE CONTRACT LEGAL DESCRIPTION OF PROPERTY Legal Description to be added. Page 8 of 16 EXHIBIT "B" TO PURCHASE CONTRACT DEVELOPMENT AGREEMENT THIS DEVELOPMENT AGREEMENT, (the "Agreement") made as of the day of 2016 (the "Effective Date") between the ROANOKE COUNTY BOARD OF SUPERVISORS, a political subdivision of the Commonwealth of Virginia (the "County"), the ECONOMIC DEVELOPMENT AUTHORITY OF ROANOKE COUNTY, VIRGINIA (the "Authority"), and WAUKESHAW DEVELOPMENT, INC., a Virginia Corporation ("the Developer") and/or its assigns. RECITALS: A. The County owns certain real property and improvements (the "Property") situated at 100 Highland Road, Vinton, VA 24179. B. The County and the Authority desire to redevelop the Property for residential and commercial uses and that Waukeshaw Development, Inc., serve as the Developer for the project. C. As a condition of its proposal to redevelop the Property, the Developer desires that the County and the Authority provide certain services or other deliverables as described in this Agreement. D. The County and the Authority desire to provide the services and other deliverables described in this Agreement to facilitate the redevelopment of the Property by the Developer. E. The parties expect that the Developer will promote economic development and generate new local tax revenues for Roanoke County, with a projected $9,200,000 investment; and F. This increased investment constitutes a valid public purpose for the expenditure of public funds. G. The Authority desires to grant certain monies to assist in realizing this investment within the County. NOW, THEREFORE, in consideration of the foregoing and other good and valuable consideration, the County, the Authority, and the Developer agree as follows: Page 9 of 16 ARTICLE I Developer's Obligations Section 1.1 The Developer shall redevelop the Property in accordance with the provisions of this Agreement. Section 1.2 Within one hundred and eighty (180) days after purchasing the Property, The Developer shall commence construction of the Project. The Developer shall complete the Project within thirty-six (36) months after commencement of construction. All costs of every kind and description associated with the Project shall be borne by Buyer, except those costs to be waived or paid for by the County, if within the County's control, as more particularly described herein. In constructing the Project, the Developer shall comply with all applicable laws, codes, and regulations. Section 1.3 The Developer shall be responsible for marketing and leasing the residential and commercial units at the Property. Any residential units at the Property will be leased as "market rate" housing. Section 1.4 The Developer represents that the Project cost (including but not limited to construction and related soft costs) is estimated at $9,200,000 Million. Section 1.5 The Developer agrees to prepare all documents as necessary to achieve the historic preservation certifications, designations and grants. Section 1.6 The Developer agrees to complete an architectural design plan, preliminary construction cost estimates, and explore financing opportunities, all which shall be shared with the County and/or Authority. Section 1.7 The Developer shall ascertain the sufficiency of the water and sewer connections, and the sprinkler capacity and determine with the Town of Vinton if any upgrades to the existing infrastructure are required. Section 1.8 The Developer shall ascertain with the Town of Vinton how the billing for the proposed units will be generated. Section 1.9 The Developer shall determine with the Town of Vinton the required parking ratios and requirements. Section 1.10 The Developer shall determine with the Town of Vinton any off-site improvements and permit fees required for the project including curb and gutter, street lighting, sidewalks, and entrance permits. Page 10 of 16 Section 1.11 The Developer will initiate a change of zoning within the first thirty (30) days of this Agreement to accommodate the proposed development, with County serving as co - applicant. The Developer understands that the rezoning process may have already been initiated. ARTICLE II County's and/or Authority's Obligations Section 2.1 In addition to the foregoing, the County agrees to provide the following in conjunction with the redevelopment and construction of the Property by the Developer: 2.1.1 The County agrees to act as a conduit for any additional incentives or funds identified by the County or by the Developer that may benefit the project, including those that must be procured by a not- for-profit entity or municipality. This may be accomplished via the County, or the Authority. 2.1.2 Should the land on subject parcel not be enough to accommodate the amount of code -required parking, Seller will provide a portion of 156 Highland Street, either by easement or by subdivision and title transfer, and at no charge, in an amount sufficient to satisfy that requirement. 2.1.3 The Developer shall provide any required easement to allow for access to the river trail or proposed trailhead parking, or access to and from the bus repair depot, however the Developer shall bear no responsibility for the cost of improvements, or any related maintenance. 2.1.4 The County shall indemnify the Developer from any liability associated with activities on such easements, or any leased property, including those activities associated with the river trail, and access easements to and from its adjacent properties or facilities, to the extent allowed by law. 2.1.5 Any parking required for the activities on the County's adjacent lot shall be provided by the County unless specifically and separately negotiated with the Developer. Section 2.2 Upon receipt of an invoice from the Developer, the Authority shall reimburse the Developer for its building permit fees, Erosion and Sediment Control and Stormwater ordinance fees due from Roanoke County during the development phase of the project, which obligation concludes at Certificate of Occupancy. ARTICLE III Procedures for Economic Development Incentive Grant Section 3.1 Beginning in the calendar year 2017, the County shall appropriate to the Authority sums sufficient for an Economic Development Incentive Grant for the benefit of the Project. These sum amounts will equal a total of ten (10) years of new local real estate taxes generated by the Project, which is estimated to equal one million dollars ($1,000,000). The total amount of the Economic Development Incentive Grant shall not exceed $1,000,000 over a ten- year (10) period. This ten-year period will commence on January 1, 2018. Section 3.2 Within sixty (60) days of the end of each calendar year beginning January 1, 2018 and until December 31, 2027, the Developer shall provide such financial and tax data Page 11 of 16 relating to the Project (provided that any personally identifiable, private, confidential or other information the Developer is required by law to keep private, shall be redacted) as may be reasonably required by the Authority so that the Authority may calculate the actual grant amounts. The Developer hereby authorizes the Commissioner of the Revenue for Roanoke County and the Commonwealth of Virginia to release to the Authority and the County the Developer's tax information and data so that the Authority may calculate the actual reimbursement amounts. The Authority shall pay the annual reimbursement amount to the Developer at an address designated by the Developer within thirty (30) days after receipt by the Authority of the data. Section 3.3 If the Developer terminates this Project or fails to complete the construction of this development by December 31, 2017 then the Authority shall be relieved of any obligation to the Developer for any Economic Development Incentive Grant. Section 3.4 If the Developer fails to receive historic preservation certification Part 1 and 2 and commence construction and renovation activity within one year of execution of this Agreement for the Property, the Developer shall be in default of this Agreement, and the County may acquire the Property together with any improvements made by the Developer upon the payment of the sum of Ten Dollars ($10.00); and whereupon the Developer shall forthwith convey the Property to the County. In the event that the Developer fails or refuses to convey title back to the County, then the County shall have the right to enter and take possession of the Property. The Developer shall pay to the County any and all attorney's fees, costs and other expenses incurred as a result of such action. Section 3.5 The Developer agrees not to convey any portion of the Property to any other persons or entities until the project is substantially complete; substantial completion shall be determined by the issuance of a certificate of occupancy for the building. If the Developer conveys or attempts to convey any portion of the Property, this conveyance will be deemed void, of no force or effect, and a breach of this contract and shall automatically revert back to the County. ARTICLE IV Performance Security Section 4.1 The Developer agrees to provide the County and the Authority with Additional Performance Security as security for the Developer's compliance with the terms and conditions of this Agreement and completion of the Project in accordance with The Developer shall deliver to the County upon receipt of historic preservation certification and before commencing any renovation or construction work on the Property a letter of credit drawn against a bank or financial institution qualified to, licensed, and conducting business in Roanoke, Virginia subject to prior approval by the County and/or Authority in County and Authority's sole discretion. The Additional Performance Security shall be payable to the Sellers and in the amount of $200,000. Page 12 of 16 ARTICLE V Confidentiality Section 5.1 The parties to this Agreement shall hold in confidence all information contained in the Agreement or related in any way to the development or marketing of the Property, including without limitation, any information related to the rental rate of units or incentive packages offered to prospective lessees. ARTICLE VI Liens Section 6.1 The Developer shall be liable for all obligations as the result of any material, materialmen's, or similar lien, and any obligation which arises in connection with the Project. In the event that any party hereto receives actual notice of any such lien, the party receiving such notice shall give the other parties prompt notice of such lien. ARTICLE VII Force Majeure Section 7.1 In the event that any party to this Agreement is delayed or prevented from performing any of its respective obligations (the "Delayed Party") under this Agreement by reason of strikes, lockouts, labor problems, inability to procure materials, contractors, professionals, inability to obtain utilities or failure of utilities, laws or other governmental requirements, riots, war, or other cause not brought about by the Delayed Party, and not related to any financial liability on the part of the Delayed Party, the time for performance of the obligation shall be extended by a period of time equal to the period of such delay or prevention. ARTICLE VIII Disclaimer of Liability Section 8.1 No warranties or representations have been made by the County concerning the Project, including without limitation intended, the economic, legal, or physical feasibility of Project, or the suitability of the Property, or the merchantability, fitness, or suitability of the completed Project. The County hereby disclaims any implied warranty or representation concerning the Project, including without limitation intended, those aspects described in the immediately preceding sentence. ARTICLE IX Notices Section 9.1 Any notice, demand, request, approval, consent, or other communication (collectively referred to as a Notice) concerning this Agreement or any matter arising in connection with this Agreement shall be in writing and addressed to the other party at the address set forth below. Any Notice shall be given by either: (i) personal delivery, in which event it shall be deemed given on the date of delivery; or (ii) certified mail return receipt requested, in which event it shall be deemed given three (3) business days after the date deposited in any post office, branch post office, or official depository. Any party may change any address for the delivery of Page 13 of 16 Notice to such party, by giving Notice in accordance with the provisions of this Section. The attorneys for the parties may give any Notice. ARTICLE X Miscellaneous Section 10.1 The rights and obligations of the parties under this Agreement shall inure to the benefit of and be binding upon the parties hereto and all persons who succeed to their respective rights and obligations. Section 10.2 This Agreement cannot be changed nor can any provision of this Agreement, or any right or remedy of any party, be waived orally. Changes and waivers can only be made in writing and the change or waiver must be signed by the party against whom the change or waiver is sought to be enforced. Any waiver of any provision of this Agreement, or any right or remedy, given on any one or more occasions shall not be deemed a waiver with respect to any other occasion. Section 10.3 This Agreement is signed by the parties as a final expression of all of the terms, covenants, and conditions of their agreement and as a complete and exclusive statement of its terms, covenants, and conditions and is intended to supersede all prior agreements and understandings concerning the subject matter of this Agreement. Section 10.4 This Agreement may be signed in one or more counterparts or duplicate signature pages with the same force and effect as if all required signatures were contained in a single original instrument. Any one or more such counterparts or duplicate signature pages may be removed from any one or more original copies of this Agreement and annexed to other counterparts or duplicate signature pages to form a completely executed original instrument. Section 10.5 The captions contained in this Agreement were inserted for the convenience of reference only. They do not in any manner define, limit, or describe the provisions of this Agreement or the intentions of the parties. Section 10.6 Whenever masculine, feminine, neuter, singular, plural, conjunctive, or disjunctive terms are used in this Agreement, they shall be construed to read in whatever form is appropriate to make this Agreement applicable to all the parties and all circumstances, except where the context of this Agreement clearly dictates otherwise. Section 10.7 This Agreement was prepared, negotiated, and delivered in the Commonwealth of Virginia. In the event of any dispute concerning or arising out of this Agreement, the laws of the Commonwealth of Virginia shall govern and control the construction and enforcement of this Agreement. Page 14 of 16 IN WITNESS WHEREOF, the parties have signed this Agreement as of the date set forth in the first paragraph of this Agreement. ROANOKE COUNTY By: Its: Administrator ECONOMIC DEVELOPMENT AUTHORITY OF ROANOKE COUNTY, VIRGINIA By: Its: WAUKESHAW DEVELOPMENT, INC. By: Its: State/Commonwealth of County of I, , do certify that the foregoing agreement was acknowledged before me this day of 2016 by of Waukeshaw Development, Inc., a Virginia corporation, on behalf of the corporation. He/she is personally known to me or has produced identification. Notary Public Registration Number: My commission expires: Page 15 of 16 State/Commonwealth of County of I, , do certify that the foregoing agreement was acknowledged before me this day of 2016 by Thomas C. Gates, Administrator of Roanoke County, a political subdivision of the Commonwealth of Virginia, on behalf of the Board. He/she is personally known to me or has produced identification. Notary Public Registration Number: My commission expires: State/Commonwealth of County of I, , do certify that the foregoing agreement was acknowledged before me this day of 2016 by of the Economic Development Authority of Roanoke County, Virginia, on behalf of the Authority. He/she is personally known to me or has produced identification. Approved to form: Roanoke County Attorney's Office Notary Public Registration Number: My commission expires: Page 16 of 16 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 ORDINANCE 032216-4 ACCEPTING AND APPROPRIATING $4,000 FOR PRINTING COSTS OF THE K, 1, AND 2 GRADE LEVEL INSTRUCTIONAL MATERIALS TO SUPPORT THE COUNTY LITERACY PLAN WHEREAS, the County literacy plan is a K through 12 program for students that outlines how to teach students who are not reading at the appropriate age level to improve their reading skills; and WHEREAS, in August 2015 the Roanoke County Schools Instructional Resources Department held a used textbook sale and generated revenues from the sale that exceeded the appropriated budget by $33,200; and WHEREAS, the department is requesting $4,000 of the excess revenues be appropriated to cover the printing costs of the K, 1, and 2 grade level instructional materials to support the county literacy plan; and WHEREAS, spiral bound books will be purchased and all materials printed will last a number of years; and WHEREAS, Section 18.04 of the Roanoke County Charter provides that funds be appropriated by ordinance; and WHEREAS, first reading of this ordinance was held on March 8, 2016, and the second reading was held on March 22, 2016. BE IT ORDAINED by the Board of Supervisors of Roanoke County, Virginia, as follows.. Page 1 of 2 On motion of Supervisor McNamara to adopt the ordinance, seconded by Supervisor Hooker and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None PY TESTE: Debprah C. Jacks Chief Deputy Clerk to Board of Supervisors cc: Angela Roberson, Clerk to the Roanoke County School Board Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 ORDINANCE 032216-5 ACCEPTING AND APPROPRIATING FUNDS IN THE AMOUNT OF $27,500 TO ROANOKE COUNTY PUBLIC SCHOOLS FROM THE NATIONAL BOARD FOR PROFESSIONAL TEACHING STANDARDS FOR TEACHER INCENTIVES WHEREAS, the General Assembly provides funds to award incentives to teachers in Virginia's public schools who hold certifications from the National Board for Professional Teaching Standards and meet the specified criteria; and WHEREAS, eleven (11) teachers in the Roanoke County Public Schools will receive a $2,500 incentive for holding their National Board certifications and meeting the specified criteria; and WHEREAS, the incentive is taxable to the recipient and the school division assumes responsibility for ensuring all taxes are remitted; and WHEREAS, Section 18.04 of the Roanoke County Charter provides that funds be appropriated by ordinance; and WHEREAS, first reading of this ordinance was held on March 8, 2016, and the second reading was held on March 22, 2016. BE IT ORDAINED by the Board of Supervisors of Roanoke County, Virginia, as follows.. 1. That the sum of $27,500 is hereby appropriated to the Roanoke County Public Schools; and 2. That this ordinance shall take effect from and after the date of adoption. Page 1 of 2 On motion of Supervisor McNamara to adopt the ordinance, seconded by Supervisor Hooker and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None A COPY TESTE: Deborah C. Jacks I Chief Deputy Clerk to Board of Supervisors cc: Angela Roberson, Clerk to the Roanoke County School Board Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 ORDINANCE 032216-6 ACCEPTING AND APPROPRIATING FUNDS IN THE AMOUNT OF $2,300 TO THE ROANOKE COUNTY PUBLIC SCHOOLS FROM SHARE OUR STRENGTH AND THE VIRGINIA NO KID HUNGRY CAMPAIGN TO EXPAND THE BREAKFAST PROGRAM AT NORTHSIDE HIGH SCHOOL WHEREAS, the Roanoke County Public Schools Nutrition Department was awarded a grant of $2,300 from Share Our Strength and the Virginia No Kid Hungry Campaign to support the expansion of the breakfast program at Northside High School; and WHEREAS, the grant funds will be spent on a mobile vending cart that will allow staff to serve meals outside the cafeteria; and WHEREAS, it is anticipated the cart will increase participation and help support the goal of providing healthy meals to as many students as possible; and WHEREAS, Section 18.04 of the Roanoke County Charter provides that funds be appropriated by ordinance; and WHEREAS, first reading of this ordinance was held on March 8, 2016, and the second reading was held on March 22, 2016. BE IT ORDAINED by the Board of Supervisors of Roanoke County, Virginia, as follows.. That the sum of $2,300 is hereby appropriated to the Roanoke County Public Schools; and 2. That this ordinance shall take effect from and after the date of adoption. Page 1 of 2 On motion of Supervisor Hooker to adopt the ordinance, seconded by Supervisor McNamara and carried by the following recorded vote: AYES: Supervisors Assaid, Hooker, McNamara, Peters NAYS: Supervisor Bedrosian A DORY TESTE: Deborah C. Jacks/ Chief Deputy Clerk 4e Board of Supervisors cc: Angela Roberson, Clerk to the Board County School Board Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 ORDINANCE 032216-7 APPROVING THE SALE OF THE 419 LIBRARY PROPERTY TO HERITAGE ROANOKE, LLC, AND AUTHORIZING THE EXECUTION OF A CONTRACT OF SALE WHEREAS, the Board of Supervisors owns property located at 3131 Electric Road consisting of two (2) parcels containing 2.526 acres and 0.93 acre previously used as the main headquarters for the County library system known as the "419 Library"; and WHEREAS, upon completion of the new South County Library, the 419 Library was vacated and made available for public acquisition; and WHEREAS, in July of 2014 the County advertised a Request for Proposals for either the sale or lease of the former 419 Library building; and WHEREAS, Heritage Roanoke, LLC, submitted an Offer to Purchase the property to establish a corporate office center for American Healthcare, Inc., which Offer the County accepted; and WHEREAS, a draft contract of sale has been prepared between the County and Heritage Roanoke, LLC, providing for the purchase of the property in "AS IS" condition at a total purchase price of $1.54 million, $1.49 million for the parcel containing 2.526 acres and $50,000 for the parcel containing 0.93 acre; and WHEREAS, this ordinance authorizes the conveyance of the former 419 Library located at 3131 Electric Road to Heritage Roanoke, LLC, upon the terms and conditions set out in the above-mentioned Contract; and Page 1 of 3 WHEREAS, Section 18.04 of the Roanoke County Charter directs the acquisition and conveyance of real estate interests be accomplished by ordinance; the first reading and public hearing for this ordinance was held on March 22, 2016. Due to time constraints the second reading was waived, upon a four-fifths (4/5th) vote of the Board pursuant to Article V, Chapter 2, Section 2-123(h) of the Roanoke County Code. NOW THEREFORE, BE IT ORDAINED by the Board of Supervisors of Roanoke County, Virginia, as follows: 1. That the conveyance of a 2.526 acre parcel and 0.93 acre parcel of real estate known as the former 419 Library and located at 3131 Electric Road (Tax Map Numbers 076.16-02-07.00 and 076.16-02-08.00) to Heritage Roanoke, LLC, upon certain terms and conditions as set forth in a Contract of Sale, is hereby approved and authorized; and 2. That the County Administrator or Assistant County Administrators are hereby authorized to execute such documents and take such actions on behalf of Roanoke County in this matter as are necessary to accomplish the acquisition of this real estate, all of which shall be approved as to form by the County Attorney. Page 2 of 3 On motion of Supervisor McNamara to adopt the ordinance and waive the second reading upon 4/5t" vote, seconded by Supervisor Peters and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None A GORY TESTE: Deborah C. Jacks Vthe Chief Deputy Clerk Board of Supervisors cc: Jill Loope, Director of Economic Development Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 3 of 3 CONTRACT OF SALE THIS CONTRACT of sale made and entered into this 22nd day of March 2016, by and between the BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, its successors or assigns, party or parties of the first part, hereinafter referred to as "Seller," and HERITAGE ROANOKE, LLC, party of the second part, hereinafter referred to as "Purchaser." WITNESSETH: NOW THEREFORE, in consideration of the premises and the mutual promises, covenants, and conditions set forth herein, the parties agree as follows: 1. PROPERTY: The Seller agrees to sell and the Purchaser agrees to buy all those certain lots, tracts or parcels of land, together with any improvements thereon, rights incident thereto, and appurtenances thereunto belonging, situate in the County of Roanoke, Virginia, and more particularly described as follows: All those certain tracts or parcels of land, together with any improvements thereon, rights incident thereto, and appurtenances thereunto belonging, situate in the County of Roanoke, Virginia, and more particularly shown and designated as 2.526 acre parcel and 0.93 acre parcel located at 3131 Electric Road, Tax Map Number 76.16-02-07.00 and Tax Map Number 76.16-02-08.00. THIS BEING all of the same real estate conveyed to the Board of Supervisors of Roanoke County by deeds from Radford & Radford, Inc., dated June 25, 1970 (Deed Book 898 Page 759); Donald J. Plybon and Teresa B. Plybon dated September 19, 1987 (Deed Book 1273, Page 405); and Eloise P. Clements and Charles Clements dated December 21, 1998 (Deed Book 1605, Page 384). Hereinafter referred to as the "Property." 2. PURCHASE PRICE: The total purchase price for the Property is One Million Five Hundred and Forty Thousand Dollars ($1,540,000.00), which is payable to Seller as follows: (A) Purchaser shall deliver to Poe & Cronk Real Estate Group, Inc., ("the "Broker") the sum of Twenty Five Thousand Dollars ($25,000) (hereinafter referred to as the Page 1 of 6 "Deposit") which shall be deposited into the Broker's non-interest bearing Escrow Account within (1) one business day following the approval of Contract by the Board of Supervisors of Roanoke County, Virginia. The Deposit shall be applied to the Purchase Price at closing or returned to the Purchaser in the event the Conditions (see below) have not been satisfied or waived by Purchaser; the Deposit shall be applied at Closing (see below) to the Purchase Price. (B) The balance of the Purchase Price shall be paid to Seller at Closing by wire transfer of immediately available funds to an account designated by Seller. 3. CONDITIONS: Purchaser shall have Thirty (30) days following the execution of this Contract of Sale as a due diligence period to obtain satisfactory financing to purchase, renovate, and equip the improvements to the Property for use as a corporate office center. If no notice to withdraw is given prior to the expiration of the due diligence period, then satisfactory financing shall be deemed secured by the Purchaser, and finalization of the Contract of Sale shall proceed. 4. CLOSING: Closing shall take place within thirty (30) days of the date the Conditions have been satisfied or waived by Purchaser. Closing shall be held at the offices of the Purchaser's attorney. 5. TAXES: Real estate and other taxes, water, sewer, and other customary charges shall be apportioned pro rata on a per diem basis between the Seller and the Purchaser as of the date of Closing. The Seller shall be responsible for preparation of the deed, payment of the tax imposed pursuant to the provisions of Section 58.1-802 of the Code of Virginia, 1950, as amended, payment of any other taxes properly payable by the Grantor/Seller, and payment of the Seller's attorney's fees, if applicable. Except as otherwise specifically provided herein, all other costs and recordation fees incurred in connection herewith shall be the responsibility of the Purchaser. Page 2 of 6 6. TITLE TO PROPERTY: The Seller shall deliver to Purchaser a good and sufficient deed for the Property at Closing, conveying to Purchaser title with SPECIAL WARRANTY and free and clear of all liens, encumbrances, easements, conditions, and restrictions, except as otherwise specifically provided herein or as Purchaser may, at its option, waive in writing. Seller represents and warrants that Seller has no knowledge of any reason or circumstance that would prevent Seller from conveying such title. If a defect is found which can be remedied by legal action within a reasonable time, Seller shall, at Seller's expense not to exceed $1,000.00, promptly take such action as is necessary to cure the defect. If the Seller, acting in good faith, is unable to have such defect corrected within sixty (60) days after written notice of such defect is given, or is unable to have such defect corrected at a cost not to exceed $1,000.00 and Seller elects not to expend additional sums for such correction, then Purchaser may, at its option, either (i) terminate this Contract, in which event the Purchaser shall be entitled to the return of the Deposit, shall have no obligation to purchase the Property, and this Contract shall be null and void, or (ii) waive the foregoing rights and enforce its rights to acquire the Property as provided herein. The parties may extend the date for Closing by mutual agreement in order to comply with the requirements of this paragraph. 7. RISK OF LOSS: All risk of loss or damage to the Property shall remain on the Seller until the date of Closing. In the event of substantial loss or damage to the Property or its building or improvements prior to Closing, Purchaser shall have the option of either (i) terminating this Contract and recovering the Deposit, or (ii) affirming this Contract, in which event Seller shall assign to Purchaser all of Seller's right under any policy or policies of insurance applicable to the Property and pay over to Purchaser any sums received as a result of such loss or damage. Page 3 of 6 8. REAL ESTATE COMMISSION: Seller and Purchaser acknowledge that they have dealt with no real estate brokers with respect to the transaction contemplated in this Contract of Sale, other than Poe & Cronk Real Estate Group, Inc., and its agents Dennis Cronk and Matt Huff, who are serving as the Seller's Designated Agents, and Jim Bolling, who is serving as the Purchaser's Designated Agent. Upon Closing, the Broker shall disburse from the Seller's proceeds a real estate commission per a separate Contract between the Seller and Broker. The Broker and Designated Agents shall not have any claim to a real estate commission until Closing of the Contract of Sale occurs. 9. DEFAULT: In the event Seller neglects or fails to comply with the provisions and covenants herein, Purchaser shall be at liberty to seek remedy in specific performance. In the event of Purchaser's default, Seller shall retain the full amount of the Deposit. 10. REFUSAL: If, prior to the execution of this Contract, the Seller receives any written offers from third parties to purchase the Property with better terms and conditions than the Purchaser's offer, then the Seller agrees to provide the Purchaser with a copy of the third party's offer and allow five (5) days for the Purchaser to match the terms and conditions of that offer. 11. APPROVAL: This Contract, and the terms contained herein, is subject to approval by the Board of Supervisors of Roanoke County, Virginia. In the event that this Contract is not approved by the Board of Supervisors, Seller shall promptly provide notice of same to the Purchaser, at which time Seller shall return the Deposit to the Purchaser and this Contract shall become null and void, and neither party shall have any further rights or obligations in relation thereto. 12. MISCELLANEOUS: (A) No waiver of any breach of covenants or conditions herein shall be construed as a waiver of a covenant or condition itself or any subsequent breach thereof. The paragraph Page 4 of 6 headings appearing in this Contract are for purposes of each reference and shall not be considered a part of this Contract or in any way to modify, amend, or affect the provisions hereof. (B) This Contract represents the entire Contract between the parties and may not be modified or changed except by written instrument executed by the parties. This Contract shall be construed, interpreted, and applied according to the law of the Commonwealth of Virginia, and shall be binding upon and shall inure to the benefit of the heirs, personal representatives, successors, and assigns of the parties. (C) Purchaser accepts the Property in an "AS IS" condition acknowledges and agrees that Seller makes no representation or warranties with respect to the Property. Purchaser agrees that Purchaser is taking the Property, including the building and improvements, without any warranties or representations from the Seller and that Purchaser has had sufficient opportunities to fully examine the Property, including the building, and that Purchaser shall comply with all environmental and other laws in renovating the building, including the proper removal of any asbestos and lead paint on the Property, and any surplus personal property remaining in the building. Purchaser acknowledges that Seller has certain items which may or may not be considered affixed to the real estate. One is a CorTen Steel Sculpture by Paul B. Ostaseski. The other is a time capsule which remains in a vault on the property. Seller agrees to remove the items, at Seller' expense, if requested. If this request is not made prior to closing, then a separate agreement shall be negotiated to survive the transfer of real estate. (D) This Contract is executed in duplicate, with each having the effect of an original, one of which shall be provided to each of the parties hereto. 13. The promises in this Contract and obligations of the Purchaser and of the Seller shall survive closing and be incorporated into the deed. Page 5 of 6 IN WITNESS WHEREOF, the parties have signed this Contract as of the date set forth in the first paragraph of this Contract. BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA By: Its: HERITAGE ROANOKE, LLC By: Its: State/Commonwealth of City/County of I, , do certify that the foregoing Contract was acknowledged before me this day of 2016 by of Heritage Roanoke, LLC, a Virginia corporation, on behalf of the corporation. He/she is personally known to me or has produced identification. Notary Public Registration Number: _ My commission expires: State/Commonwealth of City/County of I, , do certify that the foregoing Contract was acknowledged before me this day of 2016 by of the Board of Supervisors of Roanoke County, a political subdivision of the Commonwealth of Virginia, on behalf of the Board. He/she is personally known to me or has produced identification. Notary Public Registration Number: My commission expires: Page 6 of 6 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 ORDINANCE 032216-8 AUTHORIZING THE CONVEYANCE OF ROLAND E. COOK ELEMENTARY SCHOOL PROPERTY TO OLD SCHOOL PARTNERS, LLC WHEREAS, the Board of Supervisors of Roanoke County acquired this property located in Vinton Magisterial District through a conveyance from the Roanoke County School Board by deed dated August 13, 2013. At the time of the conveyance from the School Board to the County, the Roland E. Cook Elementary School ("School") was no longer in use by the Roanoke County School Board and was considered surplus property; and WHEREAS, the Old School Partners, LLC ("Buyer") proposed a purchase of the School for the purpose of restoration and renovation of the School; and WHEREAS, the School is a landmark building in the County, and Buyer's proposal would preserve the historic nature of the building and also provide additional residential and commercial services and employment in the Vinton Magisterial District; and WHEREAS, the County and Buyer executed an Option to Purchase Agreement for the Roland E. Cook Elementary School ("the School") building and parcel of land on August 25, 2015; and WHEREAS, the County, the Roanoke County Economic Development Authority ("EDA"), and the Buyer entered into a Performance Agreement dated August 11, 2015, which set forth terms and conditions for the Buyer's purchase, restoration and renovation of the School Page 1 of 4 WHEREAS, this property is on Tax map numbers 60.16-09-39 and 60.16-0940 and designated as "All those certain parcels of real estate known as the "Roland E. Cook Elementary School" containing 1.0445 acres, more or less, situate in the Vinton Magisterial District, together with any improvements thereon, rights incident thereto, and appurtenances thereon belonging, all as shown on the plat entitled "Boundary survey for School Board of Roanoke County showing Lots 8 through 14 (DB 6, PG 264) Section 8, Map of Lots Belonging to the Vinton Land, Loan & Building Co. (PBI, PG5) to be conveyed to the Board of Supervisors of Roanoke County" prepared by Caldwell White Associates dated August 7, 2013 and recorded as Instrument #20 1313 868," on the Option to Purchase Agreement executed between the County and the Buyer; and WHEREAS, the Option Agreement required the County to apply to the Commonwealth of Virginia Department of Historic Resources ("DHR") for a Historic Preservation Certification and the County made such application to seek a listing of the School on the Virginia Landmarks Register and the National Register of Historic Places ("the Register"); and WHEREAS, the County has applied for and anticipates receiving the appropriate designations from the DHR prior to the conveyance of the School to Buyer; and WHEREAS, the designation of the School on the National Register of Historic Places and on the Virginia Landmarks Register has a significant fiscal impact on the ability of Buyer to finance the renovations of the School through the sale of historic tax credits, which credits are available only in the renovation of those structures designated on the National and Virginia Registers; and WHEREAS, Buyer has agreed that, subsequent to this conveyance, Buyer will Page 2 of 4 assume all responsibility to ensure that the restoration, renovation and maintenance of the School is in compliance with requirements established by the Virginia and National Registers; and WHEREAS, the County authorizes the Buyer to stand in its stead or as its proxy in ongoing agreements and negotiations with DHR with regard to the restoration, renovation and maintenance of the School so that Buyer may obtain historic tax credits; and WHEREAS, the conveyance of this surplus school property for restoration and renovation provides economic benefits to the County and preserves a historic landmark in the County; and WHEREAS, Section 18.04 of the Roanoke County Charter directs that the acquisition and conveyance of real estate interests be accomplished by ordinance; the first reading of this ordinance was held on March 8, 2016, and the second reading and public hearing were held on March 22, 2016. NOW, THEREFORE, BE IT ORDAINED by the Board of Supervisors of Roanoke County, Virginia, as follows: 1. That the County shall convey to Buyer the School property parcels, which consists of Tax map numbers 60.16-09-39 and 60.16-0940, by Deed, a copy of which is attached hereto and incorporated by reference. 2. That the County Administrator or Assistant County Administrator are hereby authorized to execute such documents and take such actions on behalf of Roanoke County in this matter as are necessary to accomplish the acquisition of this real estate, all of which shall be approved as to form by the County Attorney. Page 3 of 4 On motion of Supervisor Peters to adopt the ordinance, seconded by Supervisor Hooker and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None Chief Deputy Cle cc: Jill Loope, Director of Economic Development Page 4 of 4 yrs ACTION NO. A -032216-9.b ITEM NO. L-3 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY. VIRGINIA HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER MEETING DATE: March 22, 2016 AGENDA ITEM: Confirmation of appointment of the Private Community Resource Provider to the Roanoke County Community Policy and Management Team (CPMT) SUBMITTED BY: Deborah C. Jacks Chief Deputy Clerk to the Board APPROVED BY: Thomas C. Gates County Administrator COUNTY ADMINISTRATOR'S COMMENTS: SUMMARY OF INFORMATION: In accordance with the Bylaws of the CPMT, a representative of a private organization or association of providers of children or family services, or its designee shall be appointed by the Board of Supervisors and serve for a three-year term. The Roanoke County Community Policy and Management Team (CPMT) has recommended Lisa McDowell with Life Bridge Counseling Services as the Private Community Resource Provider for this representation of a private provider. This would become effective July 1, 2016 for a three-year term to expire June 30, 2019. STAFF RECOMMENDATION: Staff recommends the confirmation of this appointment. Page 1 of 2 VOTE: Supervisor McNamara moved to confirmation the appointments; Supervisor Peters seconded the motion. Motion approved. cc: Jessica Webb, CSA Coordinator Page 2 of 2 Yes No Absent Mr. Assaid ® ❑ ❑ Mr. Bedrosian ® ❑ ❑ Ms. Hooker ® ❑ ❑ Mr. McNamara ® ❑ ❑ Mr. Peters ® ❑ ❑ cc: Jessica Webb, CSA Coordinator Page 2 of 2 ACTION NO. A -032216-9.d ITEM NO. L-5 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER MEETING DATE: March 22, 2016 AGENDA ITEM: Request to accept and allocate grant funds in the amount of $13,500 from the Virginia Department of Emergency Management (VDEM) for fiscal year 2015 Response Team Equipment, Training and Exercise grant SUBMITTED BY: Stephen G. Simon Chief of Fire and Rescue APPROVED BY: Thomas C. Gates County Administrator COUNTY ADMINISTRATOR'S COMMENTS: SUMMARY OF INFORMATION: Roanoke County Fire and Rescue received a grant from VDEM in fiscal year 2014-2015 to purchase a foam trailer to transport and apply fire suppression foam on emergency scenes involving flammable liquids. The trailer has been built and received and initial operation training was provided by the vendor. The next step is to train our personnel to Foam Technician Level 1 and 2 certifications. These classes include both classroom and field training exercises to prepare personnel for response to flammable liquid hazardous situations. FISCAL IMPACT: The grant from VDEM will provide one hundred percent (100%) funding and no County funds are required. Ordinance #052714-4 appropriated grant funds for grants that are routine and usual in nature for the 2015-16 fiscal year. STAFF RECOMMENDATION: Staff recommends accepting and allocating grant funds in the amount of $13,500 from the Virginia Department of Emergency Management to the Fire Department. Page 1 of 2 VOTE: Supervisor McNamara moved to accept and allocate grand funds in the amount of $13,5000 from the Virginia Department of Emergency Management to the Fire Department; Supervisor Peters seconded the motion. Motion approved. cc: Steven Simon, Chief of Fire and Rescue Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 Yes No Absent Mr. Assaid ® ❑ ❑ Mr. Bedrosian ® ❑ ❑ Ms. Hooker ® ❑ ❑ Mr. McNamara ® ❑ ❑ Mr. Peters ® ❑ ❑ cc: Steven Simon, Chief of Fire and Rescue Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 ACTION NO. A -032216-9.e ITEM NO. L-6 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER MEETING DATE: March 22, 2016 AGENDA ITEM: Request to accept and allocate grant funds in the amount of $40,122.72 from the U. S. Department of Justice's Bulletproof Vest Partnership to the Roanoke County Police Department SUBMITTED BY: APPROVED BY: Howard B. Hall Chief of Police Thomas C. Gates County Administrator COUNTY ADMINISTRATOR'S COMMENTS: SUMMARY OF INFORMATION: The U. S. Department of Justice Bulletproof Vest Partnership (BVP) has awarded the Roanoke County Police Department a matching grant totaling $40,122.72 to assist in the purchase of protective vests. This grant expires on August 31, 2017. FISCAL IMPACT: This is a 50/50 matching grant. The grant will provide $20,061.36 from the U. S. Department of Justice's Bulletproof Vest Partnership and the Police Department operating budget will provide the matching funds of $20,061.36. Budget Ordinance #052615-3 appropriated grant funds for grants that are routine and usual in nature for the 2015-16 fiscal year. STAFF RECOMMENDATION: Staff recommends the acceptance and allocation of grant funds in the amount of $40,122.72 from the U. S. Department of Justice's Bulletproof Vest Partnership to the Roanoke County Police Department. Page 1 of 2 VOTE: Supervisor McNamara moved to accept and allocate grant funds in the amount of $40,122.72 from the U.S. Department of Justice's Bulletproof Vest Partnership to the Roanoke County Police Department; Supervisor Peters seconded. Motion approved. cc: Howard B. Hall, Chief of Police Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 Yes No Absent Mr. Assaid ® ❑ ❑ Mr. Bedrosian ® ❑ ❑ Ms. Hooker ® ❑ ❑ Mr. McNamara ® ❑ ❑ Mr. Peters ® ❑ ❑ cc: Howard B. Hall, Chief of Police Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 ACTION NO. A -032216-9.f ITEM NO. L-7 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER MEETING DATE: March 22, 2016 AGENDA ITEM: Request to accept and allocate grant funds in the amount of $1,500 from the Virginia Department of Criminal Justice Services (DCJS) to the Roanoke County Police Department SUBMITTED BY: APPROVED BY: Howard B. Hall Chief of Police Thomas C. Gates County Administrator COUNTY ADMINISTRATOR'S COMMENTS: SUMMARY OF INFORMATION: The DCJS has awarded the Roanoke County Police Department a grant to help purchase MP4 players for the department's Crisis Intervention Team (CIT) Program. These devices will be used during CIT training. The 2015 grant is a one-time grant in the amount of $1,500 and expires on December 31, 2016. FISCAL IMPACT: The grant is one -hundred percent (100%) State funded. This grant does not require any matching funds. Budget Ordinance #052615-3 appropriated grant funds for grants that are routine and usual in nature for the 2015-16 fiscal year. STAFF RECOMMENDATION: Accept and allocate grant funds in the amount of $1,500 from the Virginia Department of Criminal Justice Services to the Roanoke County Police Department. Page 1 of 2 VOTE: Supervisor McNamara moved to accept and allocate grant funds in the amount of $1,500 from the Virginia Department of Criminal Justice Services to the Roanoke County Police Department; Supervisor Peters seconded the motion. Motion approved. cc: Howard B. Hall, Chief of Police Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 Yes No Absent Mr. Assaid ® ❑ ❑ Mr. Bedrosian ® ❑ ❑ Ms. Hooker ® ❑ ❑ Mr. McNamara ® ❑ ❑ Mr. Peters ® ❑ ❑ cc: Howard B. Hall, Chief of Police Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 ACTION NO. A -032216-9.a ITEM NO. L-8 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER MEETING DATE: March 22, 2016 AGENDA ITEM: Request to accept and allocate grant funds in the amount of $71,330.48 from the High Intensity Drug Trafficking Areas (HIDTA) Program to the Roanoke County Police Department for the Roanoke Valley Regional Drug Unit SUBMITTED BY: APPROVED BY: Howard B. Hall Chief of Police Thomas C. Gates County Administrator COUNTY ADMINISTRATOR'S COMMENTS: SUMMARY OF INFORMATION: The HIDTA funds were provided to identify organized drug trafficking organizations and, when possible, to prosecute the cases as drug trafficking conspiracies. Roanoke County Police Department serves as the lead agency and the Roanoke County Department of Finance serves as fiscal agent. At the end of the 2015 calendar year, additional funds in the amount of $11,330.48 were available to reimburse for expenses incurred by the Roanoke Valley Regional Drug in calendar year 2015. In addition, the Roanoke Valley Regional Drug Unit received a commitment of funding from HIDTA in the amount of $60,000 for the 2016 calendar year. These funds will be used to continue to support investigations of drug trafficking organizations that are operating in the greater Roanoke Valley. FISCAL IMPACT: Grant is one hundred percent (100%) federal funds. No matching funds from the County are required. Budget Ordinance #052615-3 appropriated grant funds for grants that are routine and usual in nature for the 2015-16 fiscal year. Page 1 of 2 STAFF RECOMMENDATION: Accept and allocate grant funds in the amount of $71,330.48 from the High Intensity Drug Trafficking Areas (HIDTA) Program to the Roanoke County Police Department for the Roanoke Valley Regional Drug Unit. VOTE: Supervisor McNamara moved to accept and allocated grant funds in the amount of $71,220.48 from the High Intensity Drug Trafficking Areas to the Roanoke County Police Department for the Roanoke Valley Regional Drug Unit; Supervisor Peters seconded the motion. Motion approved. cc: Howard B. Hall, Chief of Police Ruth Ellen Kuhnel, County Attorney Christopher Bever, Director of Management and Budget Page 2 of 2 Yes No Absent Mr. Assaid ® ❑ ❑ Mr. Bedrosian ® ❑ ❑ Ms. Hooker ® ❑ ❑ Mr. McNamara ® ❑ ❑ Mr. Peters ® ❑ ❑ cc: Howard B. Hall, Chief of Police Ruth Ellen Kuhnel, County Attorney Christopher Bever, Director of Management and Budget Page 2 of 2 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 RESOLUTION 032216-9.a EXPRESSING THE APPRECIATION OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY TO HAROLD D. CHRIMES, JR., PARAMEDIC/FIREFIGHTER, UPON HIS RETIREMENT AFTER MORE THAN TWENTY-FIVE (25) YEARS OF SERVICE WHEREAS, Harold D. Chrimes, Jr. was employed by Roanoke County on January 2,1991 -land WHEREAS, Mr. Chrimes retired on March 1, 2016, after twenty-five (25) years and two (2) months of devoted, faithful and expert service to Roanoke County; and WHEREAS, Mr. Chrimes, throughout his employment, has been instrumental in improving the quality of life and services to the citizens of Roanoke County; and WHEREAS, during Mr. Chrimes' time serving the citizens of Roanoke County, he provided compassionate and dedicated service to countless patients; and WHEREAS, Mr. Chrimes was highly respected amongst his peers and provided countless hours of mentoring to new fire and rescue employees who have gone on to provide competent service to the County; and WHEREAS, Mr. Chrimes has served on the Regional Heavy Technical Rescue Team and provided countless hours of training to numerous personnel in the area of Heavy Technical Rescue; and WHEREAS, Mr. Chrimes has provided training to volunteer and career agencies internationally, nationally, and across the state in multiple disciplines; and WHEREAS, Mr. Chrimes has served numerous years repairing stretchers and small equipment for the department ensuring safety for its personnel. NOW, THEREFORE, BE IT RESOLVED that the Board of Supervisors of Roanoke Page 1 of 2 County expresses its deepest appreciation and the appreciation of the citizens of Roanoke County to HAROLD D. CHRIMES, JR. for more than twenty-five (25) years of capable, loyal and dedicated service to Roanoke County; and FURTHER, the Board of Supervisors does express its best wishes for a happy and productive retirement. On motion of Supervisor McNamara to adopt the resolution, seconded by Supervisor Peters and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None A COP1Y TESTE: Deb'.rah C. Jacks f' / Chief Deputy ClerkVo the Board of Supervisors Page 2 of 2 ACTION NO. A -032216-9.c ITEM NO. L-4 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER MEETING DATE: March 22, 2016 AGENDA ITEM: Request to accept and allocate grant funds in the amount of $8,342.46 from the U. S. Department of Justice's Bulletproof Vest Partnership to the Roanoke County Sheriff's Office SUBMITTED BY: APPROVED BY: Eric Orange Sheriff Thomas C. Gates County Administrator COUNTY ADMINISTRATOR'S COMMENTS: SUMMARY OF INFORMATION: The U.S. Department Justice's Bulletproof Vest Partnership (BVP) awarded the Roanoke County Sheriff's Office an $8,342.46 matching grant to assist in the purchase of protective vests. This grant expires on August 31, 2017. FISCAL IMPACT: This is 50/50 matching grant. The grant will provide $4,171.23 from the U.S. Department of Justice and the Sheriff Department Operating budget will provide the matching funds of $4,171.23. Budget Ordinance #052615-3 appropriated grant funds for grants that are routine and usual in nature for the 2015-16 fiscal year. STAFF RECOMMENDATION: Staff recommends the acceptance and allocation of grant funds to the Sheriff Office in the amount of $8,346.46. Page 1 of 2 VOTE: Supervisor McNamara moved to accept and allocate grant funds in the amount of $8,346.46 to the Sheriff's Office; Supervisor Peters seconded the motion. Motion approved. cc: Eric Orange, Sheriff Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 Yes No Absent Mr. Assaid ® ❑ ❑ Mr. Bedrosian ® ❑ ❑ Ms. Hooker ® ❑ ❑ Mr. McNamara ® ❑ ❑ Mr. Peters ® ❑ ❑ cc: Eric Orange, Sheriff Rebecca Owens, Director of Finance Christopher Bever, Director of Management and Budget Page 2 of 2 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 RESOLUTION 032216-9 APPROVING AND CONCURRING IN CERTAIN ITEMS SET FORTH ON THE BOARD OF SUPERVISORS AGENDA FOR THIS DATE DESIGNATED AS ITEM L- CONSENT AGENDA BE IT RESOLVED by the Board of Supervisors of Roanoke County, Virginia, as follows: That the certain section of the agenda of the Board of Supervisors for March 22, 2016, designated as Item L - Consent Agenda be, and hereby is, approved and concurred in as to each item separately set forth in said section designated Items 1 through 8 inclusive, as follows: 1. Approval of minutes — January 19, 2016 2. Resolution expressing the appreciation of the Board of Supervisors of Roanoke County to Harold D. Chrimes, Jr., Paramedic/Firefighter, upon his retirement after more than twenty-five (25) years of service 3. Confirmation of appointment of the Private Community Resource Provider to the Roanoke County Community Policy and Management Team (CPMT) 4. Request to accept and allocate grant funds in the amount of $8,342.46 from the U. S. Department of Justice's Bulletproof Vest Partnership to the Roanoke County Sheriff's Office 5. Request to accept and allocate grant funds in the amount of $13,500 from the Virginia Department of Emergency Management (VDEM) for fiscal year 2015 Response Team Equipment, Training, and Exercise grant 6. Request to accept and allocate grant funds in the amount of $40,122.72 from the U. S. Department of Justice's Bulletproof Vest Partnership to the Roanoke County Police Department 7. Request to accept and allocate grant funds in the amount of $1,500 from the Virginia Department of Criminal Justice Services (DCJS) to the Roanoke County Police Department Page 1 of 2 8. Request to accept and allocate grant funds in the amount of $71,330.48 from the High Intensity Drug Trafficking Areas (HIDTA) Program to the Roanoke County Police Department for the Roanoke Valley Regional Drug Unit On motion of Supervisor McNamara to adopt the resolution, seconded by Supervisor Peters and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None A QOPT TESTE: Deborah C. Jacks / Chief Deputy Clerk t e Board of Supervisors Page 2 of 2 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 RESOLUTION 032216-10 TO SET THE REAL ESTATE MAXIMUM TAX RATE FOR CALENDAR YEAR 2016 TO SUPPORT THE FISCAL YEAR 2016-2017 OPERATING BUDGET WHEREAS, the Roanoke County Board of Supervisors of Roanoke Virginia will set maximum tax rates for calendar year 2016 to support the fiscal year 2016-2017 operating budget; and WHEREAS, a public hearing for citizen comments on setting maximum tax rates was held on March 22, 2106, at a regular meeting of the Board of Supervisors of Roanoke County Virginia; WHEREAS, the Roanoke County Board of Supervisors will adopt final 2016 calendar year tax rates to support the fiscal year 2016-2017 operating budget on April 12, 2016, following a public hearing for citizen comments on adopting calendar year 2016 tax rates; NOW, THEREFORE, BE IT RESOLVED by the Roanoke County Board of Supervisors of Roanoke Virginia, set the following Real Estate maximum tax rate for calendar year 2016 to support the fiscal year 2016-2017 operating budget: (a) The Real Estate Tax for calendar year 2016 is set at a rate of not more than $1.09 per $100 of assessed valuation. Page 1 of 2 On motion of Supervisor Peters to adopt the resolution, seconded by Supervisor Hooker and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None TESTE Dsborah C. Jacq Chief Deputy Cle to the Board of Supervisors cc: Christopher Bever, Director of Management and Budget Kevin Hutchins, Treasurer Nancy Horn, Commissioner of the Revenue Page 2 of 2 AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 RESOLUTION 032216-11 TO SET THE PERSONAL PROPERTY MAXIMUM TAX RATE FOR CALENDAR YEAR 2016 TO SUPPORT THE FISCAL YEAR 2016-2017 OPERATING BUDGET WHEREAS, the Roanoke County Board of Supervisors of Roanoke Virginia will set maximum tax rates for calendar year 2016 to support the fiscal year 2016-2017 operating budget; and WHEREAS, a public hearing for citizen comments on setting maximum tax rates was held on March 22, 2106, at a regular meeting of the Board of Supervisors of Roanoke County Virginia; WHEREAS, the Roanoke County Board of Supervisors will adopt final 2016 calendar year tax rates to support the fiscal year 2016-2017 operating budget on April 12, 2016, following a public hearing for citizen comments on adopting calendar year 2016 tax rates; NOW, THEREFORE, BE IT RESOLVED by the Roanoke County Board of Supervisors of Roanoke Virginia, set the following Personal Property maximum tax rate for calendar year 2016 to support the fiscal year 2016-2017 operating budget: (a) The Personal Property Tax for calendar year 2016 is set at a rate of not more than $3.50 per $100 of assessed valuation. Page 1 of 2 On motion of Supervisor McNamara to adopt the resolution, seconded by Supervisor Hooker and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None Chief Deputy Clerk cc: Christopher Bever, Director of Management and Budget Kevin Hutchins, Treasurer Nancy Horn, Commissioner of the Revenue Page 2 of 2 Board of Supervisors AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 RESOLUTION 032216-12 TO SET THE MACHINERY AND TOOLS MAXIMUM TAX RATE FOR CALENDAR YEAR 2016 TO SUPPORT THE FISCAL YEAR 2016-2017 OPERATING BUDGET WHEREAS, the Roanoke County Board of Supervisors of Roanoke Virginia will set maximum tax rates for calendar year 2016 to support the fiscal year 2016-2017 operating budget; and WHEREAS, a public hearing for citizen comments on setting maximum tax rates was held on March 22, 2106, at a regular meeting of the Board of Supervisors of Roanoke County Virginia; WHEREAS, the Roanoke County Board of Supervisors will adopt final 2016 calendar year tax rates to support the fiscal year 2016-2017 operating budget on April 12, 2016, following a public hearing for citizen comments on adopting calendar year 2016 tax rates; NOW, THEREFORE, BE IT RESOLVED by the Roanoke County Board of Supervisors of Roanoke Virginia, set the following Machinery and Tools maximum tax rate for calendar year 2016 to support the fiscal year 2016-2017 operating budget: (a) The Machinery and Tools Tax for calendar year 2016 is set at a rate of not more than $2.95 per $100 of assessed valuation. Page 1 of 2 On motion of Supervisor McNamara to adopt the resolution, seconded by Supervisor Hooker and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None cc: Christopher Bever, Director of Management and Budget Kevin Hutchins, Treasurer Nancy Horn, Commissioner of the Revenue Page 2 of 2 Xs AT A REGULAR MEETING OF THE BOARD OF SUPERVISORS OF ROANOKE COUNTY, VIRGINIA, HELD AT THE ROANOKE COUNTY ADMINISTRATION CENTER ON TUESDAY, MARCH 22, 2016 ORDINANCE 032216-13 GRANTING A SPECIAL USE PERMIT FOR A BROADCASTING TOWER (CELL TOWER) APPROXIMATELY 150 FEET IN HEIGHT IN A 1-1, LOW INTENSITY INDUSTRIAL, DISTRICT ON A 64.2 ACRE PARCEL LOCATED AT 7014 OLD MOUNTAIN ROAD, HOLLINS MAGISTERIAL DISTRICT, UPON THE PETITION OF DREW PATTERSON (VERIZON WIRELESS AGENT) WHEREAS, Drew Patterson, agent for Verizon Wireless, has filed a petition for a special use permit for broadcasting tower use at 7014 Old Mountain Road (Tax Parcel No. 28.03-01-02.02), in an 1-1, low intensity industrial district, in the Hollins Magisterial District; and WHEREAS, the Planning Commission held a public hearing on this matter on January 2, 2016, which was continued to March 1, 2016, because the Commission requested that the Petitioner provide the Commission with additional information; and WHEREAS, the Planning Commission's public hearing on this matter was resumed on March 1, 2016, the Petitioner having provided the requested information to the Planning Commission; and WHEREAS, the Planning Commission recommends approval of the petition with the condition that the total height of the tower shall not exceed 158 feet; and WHEREAS, the Board of Supervisors of Roanoke County, Virginia, held a first reading on this matter on September 22, 2015; the second reading and public hearing on this matter was held on March 22, 2016. NOW, THEREFORE, BE IT ORDAINED by the Board of Supervisors of Roanoke County, Virginia, as follows: Page 1 of 3 1. That the Board finds that the granting of a special use permit to Drew Patterson, agent for Verizon Wireless, for broadcasting tower use on a 64.62 acre parcel located at 7014 Old Mountain Road (Tax Parcel No. 28.03-01-02.02), in the Hollins Magisterial District, is substantially in accord with the adopted 2005 Community Plan, as amended, pursuant to the provisions of Section 15.2-2232 of the 1950 Code of Virginia, as amended, and that it shall have a minimum adverse impact on the surrounding neighborhood or community, and said special use permit is hereby approved with the following condition: (a) The total height of the tower shall not exceed 158 feet. 2. That this ordinance shall be in full force and effect thirty (30) days after its final passage. All ordinances or parts of ordinances in conflict with the provisions of this ordinance be, and the same hereby are, repealed. The provisions of this special use permit are not severable. Invalidation of any word, phrase, clause, sentence or paragraph shall invalidate the remainder. The Zoning Administrator is directed to amend the zoning district map to reflect the change in zoning classification authorized by this ordinance. On motion of Supervisor Bedrosian to adopt the ordinance, seconded by Supervisor Peters and carried by the following recorded vote: AYES: Supervisors Assaid, Bedrosian, Hooker, McNamara, Peters NAYS: None PY TESTE: Deborah C. Jackq Chief Deputy ClerKqothe Board of Supervisors Page 2 of 3 cc: Arnold Covey, Director of Community Development Philip Thompson, Deputy Director of Planning Tarek Moneir, Deputy Director of Development William Driver, Director of Real Estate Valuation Ruth Ellen Kuhnel, County Attorney John Murphy, Zoning Administrator Page 3 of 3