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Stormwater Ordinance

Knox County, TN Stormwater Management Manual: Volume 2 - Whole Manual


Chapter 1 Introduction (pdf)


Chapter 1 Addressing Stormwater Management Needs (pdf)

  • 1.1 Impacts of Development and Stormwater Runoff
    • 1.1.1 Development Changes Land and Runoff
    • 1.1.2 Changes to Stream
    • 1.1.3 Changes to Stream Geometry
    • 1.1.4 Impacts to Aquatic Habitat
    • 1.1.5 Water Quality Impacts
    • 1.1.6 Stormwater Hotspots
    • 1.1.7 Effects on Ponds, Lakes and Reservoirs
  • 1.2 Addressing Stormwater Impacts
  • 1.3 Comprehensive Stormwater Management Planning
  • 1.4 Minimum Stormwater Management Standards
  • 1.5 Stormwater Quality Treatment Rationale
    • 1.5.1 Regulatory Overview
    • 1.5.2 Attaining the Water Quality Standard

Chapter 2 Criteria for Stormwater Design (pdf)

  • 2.1 Integrated Site Design Approach
    • 2.1.1 Introduction
    • 2.1.2 General Design Policies and Guidance
  • 2.2 Stormwater Quality Management
    • 2.2.1 General Requirements and Policies
    • 2.2.2 Percent TSS Removal Values for Structural BMPs
    • 2.2.3 Calculation of WQv and %TSS Removal
    • 2.2.4 Calculation of %TSS Removal for BMPs in Parallel
    • 2.2.5 Calculation of %TSS Removal for BMPs in Series
    • 2.2.6 Calculation of %TSS Removal for Flow-through Situations
    • 2.2.7 The Measurement and Calculation of Percent Imperviousness
    • 2.2.8 Reducing the WQv
  • 2.3 Channel Protection (CPv)
    • 2.3.1 Background
    • 2.3.2 Design Criteria and Policies
  • 2.4 Stormwater Quantity Management
    • 2.4.1 Overbank Flood Protection Criteria (Qp25)
    • 2.4.2 Extreme Flood Protection (Qp100)
    • 2.4.3 Downstream Impact Analysis
  • 2.5 Stormwater Conveyance Design
    • 2.5.1 General Criteria
    • 2.5.2 Pipe Systems
    • 2.5.3 Roadway Culverts
    • 2.5.4 Open Channels
    • 2.5.5 Outlet Protection
    • 2.5.6 Gutters and Inlets
  • 2.6 Bridge Requirements

Chapter 3 Stormwater Hydrology (pdf)

  • 3.1 Introduction to Hydrologic Methods
    • 3.1.1 Symbols and Definitions
    • 3.1.2 Rainfall Estimation
    • 3.1.3 Rational Method
    • 3.1.4 Regression Methods
    • 3.1.5 SCS Hydrologic Method
    • 3.1.6 Clark Unit Hydrograph
    • 3.1.7 Water Quality Calculations
    • 3.1.8 Water Balance Calculations
    • 3.1.9 Calculating Downstream Impacts (the Ten Percent Rule)
  • 3.2 Storage Design
    • 3.2.1 General Storage Concepts
    • 3.2.2 Symbols and Definitions
    • 3.2.3 Flood Protection Storage Design Procedures
    • 3.2.4 Preliminary Detection Calculations
    • 3.2.5 Estimation of the Channel Protection Volume
  • 3.3 Outlet Structures
    • 3.3.1 Symbols and Definitions
    • 3.3.2 Primary Outlets
    • 3.3.3 The Design of Extended Detention Outlets
    • 3.3.4 The Design of Channel Protection Outlets
    • 3.3.5 Multi-Stage Outlet Design
    • 3.3.6 Trash Rack and Safety Grates
    • 3.3.7 Secondary Outlets

Chapter 4 Design and Maintenance of Structural BMPs


Chapter 5 Stormwater Credits and Better Site Design Practices  (pdf)

  • 5.1 Introduction
  • 5.2 Water Quality Volume (WQv) Credits
    • 5.2.1 Introduction
    • 5.2.2 Site Planning Using Stormwater Site Design Credits
    • 5.2.3 General Policies for WQv Credits
    • 5.2.4 Credit #1: Natural Area Preservation
    • 5.2.5 Credit #2: Managed Open Space Preservation
    • 5.2.6 Credit #3: Stream and Vegetated Buffers
    • 5.2.7 Credit #4: Use of Vegetated Channels
    • 5.2.8 Credit #5: Impervious Area Disconnection
    • 5.2.9 Credit #6: Environmentally Sensitive Large Lot Neighborhoods
  • 5.3 Better Site Design Practices
    • 5.3.1 Overview
    • 5.3.2 Incorporating Better Site Design Practices into Site Design Process
    • 5.3.3 Discussion of Better Site Design Practices
    • 5.3.4 Conservation of Natural Features and Resources
    • 5.3.5 Low Impact Site Design Techniques
    • 5.3.6 Reduction of Impervious Cover
    • 5.3.7 Using Natural Features for Stormwater Management
    • 5.3.8 Better Site Design Examples

Chapter 6 Water Quality Buffers (pdf)

  • 6.1 Introduction
  • 6.2 Applicability
    • 6.2.1 Community Waters Definition
  • 6.3 Buffer Zones and Widths
    • 6.3.1 Zones
    • 6.3.2 Widths
    • 6.3.3 Width Requirements for Steep Slopes
  • 6.4 Vegetation and Enhancement Requirements
    • 6.4.1 Inner Zone (Streams and Wetlands)
    • 6.4.2 Outer Zone (Streams and Ponds/Lakes)
    • 6.4.3 Non-native and Invasive Vegetation
    • 6.4.4 Buffer Enhancement Requirements
  • 6.5 Water Quality Buffer Averaging
    • 6.5.1 Requirements and Policies
    • 6.5.2 Areas Where Buffer Averaging is Prohibited
    • 6.5.3 Example Calculation
  • 6.6 Use of Buffer Areas
    • 6.6.1 Prohibited Uses
    • 6.6.2 Allowable Uses in the Inner Zone
    • 6.6.3 Allowable Uses in the Outer Zone
  • 6.7 Allowable Disturbances
    • 6.7.1 Inner Zone
    • 6.7.2 Outer Zone
  • 6.8 Protection of Water Quality Buffers
    • 6.8.1 During Construction
    • 6.8.2 After Construction
    • 6.8.3 Signage
  • 6.9 Level Spreaders
  • 6.10 Conflicts with State Requirements

Chapter 7 Stormwater Drainage Design  (pdf)

  • 7.1 Stormwater Drainage System Design
    • 7.1.1 Drainage System Components
    • 7.1.2 Checklist for Drainage Planning and Design
    • 7.1.3 General Drainage Design Standards
  • 7.2 Storm Drain Pipe Systems
    • 7.2.1 Design Standards and Considerations
    • 7.2.2 General Design Procedure
    • 7.2.3 Capacity Calculations
    • 7.2.4 Hydraulic Grade Lines
    • 7.2.5 Minimum Grade
  • 7.3 Culvert Design
    • 7.3.1 Symbols and Definitions
    • 7.3.2 Design Standards and Considerations
    • 7.3.3 Design Procedures
    • 7.3.4 Culvert Design Example
    • 7.3.5 Design Procedures for Beveled-Edged Inlets
    • 7.3.6 Flood Routing and Culvert Design
  • 7.4 Open Channel Design
    • 7.4.1 Open Channel Types
    • 7.4.2 Symbols and Definitions
    • 7.4.3 Design Standards and Considerations
    • 7.4.4 Manning’s “n” Values
    • 7.4.5 Uniform Flow Calculations
    • 7.4.6 Critical Flow Calculations
    • 7.4.7 Vegetative Design
    • 7.4.8 Riprap Design for Lining Open Channels
    • 7.4.9 Gradually Varied Flow
    • 7.4.10 Rectangular, Triangular, and Trapezoidal Open Channel Design
  • 7.5 Energy Dissipation Design
    • 7.5.1 Overview
    • 7.5.2 Symbols and Definitions
    • 7.5.3 Design Guidelines
    • 7.5.4 Riprap Aprons
    • 7.5.5 Riprap Basins
    • 7.5.6 Baffled Outlets
    • 7.5.7 Level Spreaders
  • 7.6 Minor Drainage System Design
    • 7.6.1 Introduction and General Criteria
    • 7.6.2 Symbols and Definitions
    • 7.6.3 Street and Roadway Gutters
    • 7.6.4 Stormwater Inlets
    • 7.6.5 Grate Inlet Design
    • 7.6.6 Curb Inlet Design
    • 7.6.7 Combination Inlets
  • 7.7 Bridge Hydraulics
    • 7.7.1 Bridge Hydraulics Concepts
    • 7.7.2 Computer Applications

Chapter 8 Floodplain and Sinkholes (pdf)

  • 8.1 Introduction
  • 8.2 Applicable Federal Regulations
    • 8.2.1 National Flood Insurance Program
    • 8.2.2 Community Rating System
  • 8.3 Local Floodplain Management Tools
    • 8.3.1 FEMA Flood Insurance Studies
    • 8.3.2 Knox County Engineering Floodplain Mapping
    • 8.3.3 Stormwater Master Plans
  • 8.4 Floodplain Management Regulations
    • 8.4.1 Summary of Ordinance Requirements for Development in Floodplains
    • 8.4.2 Requirements for Land Use and Land Disturbance
    • 8.4.3 Requirements for Engineering Studies
    • 8.4.4 Requirements for Construction in Floodplains
  • 8.5 Regulations for Development in Sinkhole Areas
    • 8.5.1 Background
    • 8.5.2 Regulations and Policies

Chapter 9 Construction Site Stormwater Management (pdf)

  • 9.1 TN Construction General Permit
  • 9.2 General Principles
  • 9.3 Regulations and Policies
    • 9.3.1 General
    • 9.3.2 Protection of Water Quality Buffers
    • 9.3.3 Stabilization of Disturbed Areas
    • 9.3.4 Off-Site Sedimentation
    • 9.3.5 Construction Sequencing
    • 9.3.6 Structural Controls
    • 9.3.7 Special Requirements Priority Construction Activities
    • 9.3.8 Cut and Fill Slopes
    • 9.3.9 Construction Exits
    • 9.3.10 Good Housekeeping Practices
  • 9.4 Erosion Prevention and Sediment Control Plans
    • 9.4.1 Plan Modifications
  • 9.5 Deficient Performance
  • 9.6 Inspections and Maintenance
  • 9.7 Small Lot EPSC Plans

Chapter 10 Pollution Prevention After Construction

  • 10.1 Overview
    • 10.2 Special Pollution Abatement Permit
    • 10.3 Sediment Disposal for Structural BMP Maintenance

Appendices

A. Nomographs

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Stormwater

205 West Baxter Avenue
Knoxville, TN 37917

Phone: 865-215-5540
Fax: 865-215-5831

Hours:
Monday - Friday
8:00 am - 4:30 pm
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