Revised Stormwater Manual

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Effective June 1, 2009 - Revised Stormwater Manual (SWM)

The Revised Stormwater Manual table of contents is listed below with links to various sections of the document. Questions about content and requirements may be directed to Virginia Spillman in the Stormwater Management Division of Water Resources. Contact Virginia Spillman at 336-373-2055.

Download the Entire Stormwater Manual - 4 MB

SWM Cover Page

Table of Contents 

1 Introduction

1.1 Background
1.2.1 Non-Structural BMPs Public Education Employee Education of Commercial and Industrial Establishments City of Greensboro Public Education Outreach On-Site Refuse Management Stormwater System Maintenance Paved Area Sweeping Used Oil Recycling Material Exposure Controls to Avoid or Limit Exposure of Materials to Precipitation Spill Prevention and Cleanup Erosion and Sedimentation Control Land Use Planning and Management
1.2.2 Structural BMPs Open Vegetated Conveyance / Grass Swale Riparian Buffers Rooftop Runoff Management Grass Paving Natural Infiltration

2 North Carolina's Stormwater Requirements

2.1 Overview of City of Greensboro’s Requirements
2.2.1 NPDES Discharge Permits
2.5 Water Supply Watershed Protection Requirements
2.9 City of Greensboro’s Requirements
   2.9.1 City of Greensboro Stormwater Master Plans
   2.9.2 Stormwater Management Plan Stormwater Management / Watershed Development Plan Components
   2.9.3 Stream Protection Requirements Stream Channelization / Piping Restrictions Stream Buffers
   2.9.4 Modifications to Stormwater Requirements Water Supply Watershed Protection Stormwater Management Control
2.10 Regulatory Requirements
   2.10.1 Jurisdictional Streams and Wetlands
   2.10.2 FEMA Floodway / Floodplain

3 Stormwater Management Calculations
3.1 Stormwater Management Objectives
   3.1.1 Quality Control for High Density Development in Water Supply Watershed Areas
   (Ordinance Section 30-7)
   3.1.2 Quantity Control (Ordinance Section 27-22)
   3.1.3 Engineer’s Certification of Stormwater Quantity Control
3.2 Peak Flow Calculations
   3.2.1 Hydraulic / Hydrologic Methods
3.5.2 Drawdown Time Calculations for a Pond with an Orifice Outlet
3.6.3 Detention Storage Estimation Methodologies
3.7.1 Hydraulic Methodologies (Open and Closed Conveyance Analysis)

4 Selecting the Right BMP
4.4 Comparison of BMP Treatment Capabilities

5 Common BMP Design Elements
   5.6 Earthen Impoundments, Embankments, and Dams
   5.6.1 Seepage Control
5.7 Underdrain System
5.8 Outlets
   5.8.6 Spillways Chute Spillways Free Overfall (Straight Drop) Spillways
   5.8.8 Trash Rack

6 Landscape and Soil Composition Specifications
6.4 Landscape Plans
6.5.1 Soils Analysis
6.5.3 Soil Specifications

7 BMP Inspection and Maintenance
7.2 Legal and Financial Issues
   7.2.2 Inspection and Maintenance Agreements
7.3.10 Dam Safety
   7.3.11 Reduction of Pollutants Entering BMPs
   7.3.12 Stabilization of BMP Drainage Area
   7.3.13 Blockage of Outlets
   7.3.14 Principal and Emergency Spillway

8 Level Spreader
8.3.5 Stream Buffer Widths
8.3.6 Options where Level Spreaders Are Not Appropriate
8.3.12 Stabilization of BMP Drainage Area
8.5 Maintenance

9 Stormwater Wetlands
9.3 Design
   9.3.1 Understanding Basic Layout Concepts
   9.3.2 Step 2: Determine the Volume to Treat
   9.3.5 Outlet Design
9.4 Construction
9.5 Maintenance
   9.5.1 Common Maintenance Issues
   9.5.11 Reduction of Pollutants Entering Wetland
   9.5.12 Stabilization of BMP Drainage Area
   9.5.13 Blockage of Outlets
   9.5.14 Principal and Emergency Spillway

10 Wet Detention Basin
10.1 General Characteristics and Purpose
10.3.2 Siting Issues
   10.3.3 Pretreatment and Inflow
   10.3.4 Length, Width (Area), Depth, Geometry
   10.3.6 Sediment Accumulation
   10.3.7 Plant and Landscape Requirements
   10.3.8 Surrounding Soils and Liners
   10.3.10 Safety Considerations
10.4 Construction
10.5 Maintenance
   10.5.1 Common Maintenance Issues
   10.5.10 Dam Safety
   10.5.11 Reduction of Pollutants Entering BMPs
   10.5.12 Stabilization of BMP Drainage Area
   10.5.13 Blockage of Outlets
   10.5.14 Principal and Emergency Spillway

11 Sand Filter
11.1 General Characteristics and Purpose
11.4 Maintenance
   11.4.1 Common Maintenance Issues
   11.4.3 Reduction of Pollutants Entering BMPs
   11.4.4 Stabilization of BMP Drainage Area

12 Bioretention
12.3.1 Retreatment Options
   12.3.6 Step 6: Size the Underdrain
   12.3.8 Step 8: Select Plants and Mulch
12.4 Common Maintenance Issues

13 Filter Strip
   13.5 Maintenance

14 Grassed Swale
14.2 Meeting Regulatory Requirements
14.5 Maintenance

15 Restored Riparian Buffers
15.2 Meeting Regulatory Requirements

16 Infiltration Devices
16.2 Meeting Regulatory Requirements

17 Dry Extended Detention Basin
17.1 General Characteristics and Purpose
17.2 Meeting Regulatory Requirements
17.3 Design
   17.3.2 Siting Issues
   17.3.6 Sediment Accumulation
   17.3.8 Outlet Design
   17.3.9 Dam Safety
   17.3.10 Underground Detention Material Specifications
17.4 Maintenance
   17.4.1 Common Maintenance Issues
17.5.13 Blockage of Outlets
   17.5.14 Principal and Emergency Spillway

18 Permeable Pavement Systems

19 Rooftop Runoff Management
19.1 General Characteristics and Purpose
19.2 Meeting Regulatory Requirements
19.5 Maintenance

20 Proprietary Systems
20.1 General Characteristics and Purpose
20.2 Meeting Regulatory Requirements

APPENDIX A City of Greensboro Links

APPENDIX 1 Depth-Duration-Frequency Table for Greensboro, NC

APPENDIX 2 Pond Detention Storage Computations

APPENDIX 3 Dam Safety Law of 1967

APPENDIX 4 BMP Design Check List

APPENDIX 5 BMP Certification Requirements

APPENDIX 6 BMP Inspection and Maintenance Check List

APPENDIX 7 Preliminary BMP Capital Cost Estimates

APPENDIX 8 Stormwater BMP Bonding Process

APPENDIX 9 Recommended Guidance for Riser and Barrel Spillway Discharge Characteristics and Flood Routing

APPENDIX 10 Buffer Bubble

Link to State BMP Manual

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