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Statewide Urban Design and Specifications

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Ames, IA 50010-8664

Phone: 515-294-8103
FAX: 515-294-0467

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Iowa State University--Becoming the Best

Iowa Stormwater Management Manual

The Iowa Stormwater Management Manual will be updated from time to time. When changes are made, the version number and date will change. A summary of the changes will also be listed.

The following infiltration-related specifications and figures (Chapter 1) have been developed to accompany the design portion (Chapter 2) of the Iowa Stormwater Management Manual.

Please note - the figures are provided in PDF, AutoCad (dwg), and Microstation (dgn) formats.

Chapter 1 - Specifications

Infiltration Practices

Figures

  • Figure 1E-2.1 - Infiltration Trench pdf dwg dgn
  • Figure 1E-4.1 - Bioretention System with Engineering Fabric pdf dwg dgn
  • Figure 1E-4.2 - Bioretention System with Filter Sand Layer pdf dwg dgn
  • Figure 1I-3.1 - Dry Swale with Engineering Fabric pdf dwg dgn
  • Figure 1I-3.2 - Dry Swale with Filter Sand Layer pdf dwg dgn
  • Figure 1I-3.3 - Narrow Trench Dry Swale with Filter Sand Layer pdf dwg dgn
  • Figure 1J-2.1 - Pervious PCC Pavement pdf dwg dgn
  • Figure 1J-3.1 - Porous HMA Pavement pdf dwg dgn
  • Figure 1J-4.1 - Permeable Interlocking Concrete Pavers pdf dwg dgn

Chapter 2 - Design

The following table of contents includes links to Version 3 (dated October 28, 2009) of Chapter 2 of the Iowa Stormwater Management Manual.

The changes made since Version 2 (dated December 5, 2008) are as follows:

  • Minor correction to a calculation in Table 1 of Section 2A-4.
  • Various updates to references.
  • Complete new parts 2J, 2K, and 2L.

2A  General Information

2A-1 General Information

  • Concept
  • Overview of stormwater discharges
  • Pollutants in urban stormwater
  • Management of stormwater quality and quantity
  • Permit requirement overview

2A-2 Planning and Design Principles

  • Project scope and analysis
  • Developing a stormwater management plan
  • Planning and design principles
  • Planning and design conditions
  • Floodplain management

2A-3 Stormwater Regulations and Permitting

  • Introduction
  • Regulated activities
  • Requirements for regulated MS4s
  • Stormwater management programs

2A-4 Stormwater Management Criteria

  • Development criteria
  • Minimum stormwater management guidelines
  • Minor and major design storms
  • Design frequencies for conveyance facilities
  • Street flow criteria

2A-5 Project Drainage Report

  • Purpose
  • Instructions for preparing report
  • Contents

2B  Unified Sizing Criteria

2B-1 Unified Sizing Criteria

  • General information
  • Rainfall frequency spectrum (RFS)
  • Water quality volume (WQv)
  • Recharge volume requirements (Rev)
  • Channel protection storage volume requirements (CPv)
  • Overbank flood protection volume requirements (Qp)
  • Extreme flood volume (Qf)

2C  Stormwater Hydrology

2C-1 General Information for Stormwater Hydrology

  • Introduction
  • Definitions
  • Concepts
  • Methods of runoff estimation

2C-2 Rainfall and Runoff Analysis

  • Introduction
  • Rainfall frequency analysis
  • NRCS 24-hour storm distribution

2C-3 Time of Concentration

  • Introduction
  • Definition
  • Factors affecting time of concentration
  • Estimating time of concentration (NRCS velocity method)
  • Estimating time of concentration (NRCS lag method)
  • Design example

2C-4 Rational Method

  • Introduction
  • Characteristics
  • Limitations
  • Use of the Rational method
  • Design example

2C-5 NRCS TR-55 Methodology

  • Introduction
  • Equations and concepts
  • Runoff factor
  • Urban modifications of the NRCS method
  • WINTR-55 for analysis

2C-6 Small Storm Hydrology

  • Introduction
  • Water quality volume and peak flow
  • Method for computing the channel protection storage volume
  • Maximized water quality capture volume
  • Estimating a maximized water quality capture volume
  • Design example

2C-7 Runoff Hydrograph Determination

  • Introduction
  • Unit hydrographs
  • Application of the unit hydrograph method
  • Watershed routing (hydrograph determination)
  • Tabular hydrograph method
  • Design example

2C-8 Low-Impact Development (LID) Hydrology

  • Introduction
  • Hydrologic comparison: conventional vs. low-impact development
  • LID hydrologic analysis components
  • Process and computational procedure
  • Determination of design storm event

2C-9 Detention Storage Design

  • Introduction
  • Alternatives for estimating detention volume
  • Planning and design alternatives
  • Preliminary detention storage design
  • Modified Rational method
  • Design example

2C-10 Channel and Storage (Reservoir) Routing

  • Introduction
  • Channel routing
  • Storage (reservoir) routing
  • Stage-storage relationship
  • Stage-discharge relationship
  • Storage-indication routing
  • Detention design procedure with storage routing
  • Design example (currently under development)

2C-11 Inlet Sediment Forebays

  • Introduction
  • Water quality
  • Channel erosion control and flood control
  • Design criteria

2C-12 Detention Basin Outlet Structures

  • Introduction
  • Outlet structure types
  • Extended detention (water quality and channel protection) outlet design
  • Sizing of single-stage risers
  • Design of multiple-stage outlets
  • Extended detention outlet protection
  • Trash racks and safety grates
  • Secondary outlets

2C-13 Water Balance Calculations

  • Introduction
  • Base equations

2C-14 Downstream Hyrologic Assessment

  • Introduction
  • Reasons for downstream problems
  • The ten-percent rule
  • Design example

2D  BMP Types and Applications

2D-1 General Information for BMPs

  • Description and performance of stormwater BMPs
  • Goals of stormwater BMPs
  • Pollutant removal processes

2D-2 Non-Structural Controls

  • Education, recycling, and source controls
  • Maintenance practices

2D-3 Structural Controls

  • Structural BMPs
  • Structural control categories
  • Structural stormwater control pollutant removal capabilities
  • Selection guide for structural stormwater controls
  • General application control screening process
  • Online vs. off-line structural controls
  • Onsite vs. regional stormwater management
  • Using structural stormwater controls in series

2E  Infiltration Practices

2E-1 General Information for Infiltration Practices

  • Introduction
  • Infiltration fundamentals
  • Infiltration systems
  • Infiltration hydraulics and process
  • Soils and infiltration
  • Screening criteria for infiltration practices
  • Types of infiltration practices
  • Design criteria for infiltration practices

2E-2 Infiltration Trenches

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Application and feasibility
  • Planning and design criteria
  • Physical specifications, geometry, and volume
  • Design of infiltration trenches
  • Design procedures
  • Inspection and maintenance requirements
  • Example schematics
  • Design example

2E-3 Infiltration Basins

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Application and feasibility
  • Planning and design criteria
  • General design
  • Physical specifications, geometry, and volume
  • Design of infiltration basins
  • Procedures for infiltration basin design
  • Maintenance
  • Design example

2E-4 Bioretention Systems

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Application and feasibility
  • Planning and design criteria
  • Physical specifications and geometry
  • Structures
  • Design procedures
  • Inspection and maintenance requirements
  • Design example

2E-5 Soil Quality Restoration

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Application and feasibility
  • Planning and design criteria
  • Design procedures
  • Inspection and maintenance requirements
  • Design example

2E-6 Native Landscaping

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Application and feasibility
  • Planning and design criteria
  • Design procedures
  • Inspection and maintenance requirements

2E-7 Soils Testing Requirements for Infiltration Practices

  • Definition
  • Purpose
  • Conditions where practice applies
  • Criteria
  • Additional considerations

2F  Filtration Practices

2F-1 Sand Filter

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Application and feasibility
  • Planning and design criteria
  • Flow regulation

2F-2 Design of Surface and Perimeter Sand Filter

  • Physical specifications and geometry
  • Pre-treatment/inlets
  • Outlet structures
  • Auxiliary spillway
  • Maintenance access
  • Safety features
  • Landscaping
  • Additional site-specific design criteria and considerations
  • Design procedures
  • Inspection and maintenance requirements
  • Design example

2F-3 Underground Sand Filter

  • Description
  • Pollutant removal capabilities
  • Design criteria
  • Inspection and maintenance requirements

2G  Detention Practices

2G-1 General Information for Detention Practices

  • Introduction
  • Storage facilities

2G-2 Dry Detention

  • Description
  • Design criteria and physical specifications
  • Inspection and maintenance requirements
  • Example schematics

2G-3 Wet Detention

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Application and feasibility
  • Design approach
  • Design procedures
  • Inspection and maintenance requirements

2H  Stormwater Wetlands

2H-1 General Information for Stormwater Wetlands

  • Description
  • Stormwater managment suitability
  • Pollutant removal capabilities
  • Application and feasibility

2H-2 Design of Stormwater Wetlands

  • Planning and design criteria
  • General design
  • Physical specifications and geometry
  • Pre-treatment inlets
  • Outlet structures
  • Auxiliary spillway
  • Maintenance access
  • Safety features
  • Landscaping
  • Additional site-specific design criteria and issues
  • Design procedures
  • Inspection and maintenance requirements

2I  Vegetated Swale Systems

2I-1 General Information for Vegetated Swale Systems

  • Introduction
  • Types of vegetated practices
  • Comparative pollutant removal capability
  • Suitability and selection considerations
  • Land use factors
  • Site conditions
  • Flow regulation
  • Pre-treatment

2I-2 Grass Swales

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Application and feasibility
  • Grass swales for pre-treatment
  • Check dams
  • Channel design criteria
  • Design procedure
  • Inspection and maintenance requirements
  • Design example

2I-3 Dry and Wet Swales

  • Description
  • Stormwater management suitability
  • Pollutant removal capabilities
  • Applications and feasibility
  • Planning and design criteria
  • Design procedure
  • Design example

2I-4 Vegetated Filter Strips

  • Description
  • Pollutant removal capabilities
  • Design criteria
  • Inspection and maintenance requirements
  • Design example

2J  Pavement Systems

2J-1 General Information for Pavement Systems

  • Introduction
  • General description
  • Design considerations
  • Permeable pavement design example

2J-2 Pervious Concrete Pavement

  • General description
  • Design criteria and specifications

2J-3 Porous Asphalt Pavement

  • General description
  • Design criteria and specifications

2J-4 Permeable Pavers

  • General description
  • Pollutant removal capabilities
  • Design criteria and specifications
  • Inspection and maintenance requirements

2K  Mechanical Systems

2K-1 General Information for Proprietary Mechanical Systems

  • Introduction
  • Guidelines for using proprietary systems

2K-2 Hydrodynamic Devices

  • Description
  • Applicability
  • Continuous deflective separation (CDS)
  • Downstream defender
  • Stormceptor
  • Vortechs
  • Advantages and disadvantages
  • Performance
  • Water quantity control
  • Cold climate
  • Operation and maintenance
  • Costs

2K-3 Gravity Separator Systems

  • General description
  • Pollutant removal capabilities
  • Design criteria and specifications
  • Inspection and maintenance requirements
  • Additional maintenance considerations and requirements

2K-4 Catch Basins with Sumps and Catch Basin Inserts

  • Introduction
  • Description
  • Selection of catch basin insert filtration devices
  • Applicability
  • Limitations
  • Siting and design considerations
  • Maintenance considerations
  • Effectiveness
  • Cost considerations

2L Coagulation and Flocculation

2L-1 Coagulation and Flocculation

  • General description
  • Pollutant removal capabilities
  • Design criteria and specifications
  • Siting and design considerations
  • Limitations
  • Maintenance considerations
  • Cost considerations

2M Storm Sewer Design

2M-1 General Information for Storm Sewer Design

  • Introduction
  • Definitions
  • Location of storm sewers
  • Pipe materials
  • Physical requirements
  • Horizontal alignment

2M-2 Groundwater Barriers and Outlets

  • Introduction
  • Groundwater barriers
  • Outlets

2M-3 Street Flow and Intake /Manhole Capacity

  • Introduction
  • Definitions
  • Intercepting flows
  • Storm sewer structure locations
  • Intake capacity
  • Manhole and intake standards
  • Intake capacity design example

2M-4 Storm Sewer Sizing

  • Introduction
  • Flow formulas
  • Hydraulic losses
  • Hydraulic design of storm sewers

2N Design of Culverts

2N-1 General Information for Design of Culverts

  • Introduction
  • Definitions
  • Site considerations
  • Culvert design items
  • Design considerations
  • Pipe material
  • Pipe culvert sizes
  • Culvert inlets
  • Roadway or street overtopping
  • Storage routing

2N-2 Culvert Hydraulics

  • Culvert flow controls and equations
  • Inlet and outlet control
  • Use of inlet and outlet control nomographs
  • Culvert design example

2O Open Channel Flow

2O-1 Channel Types and Structures

  • Introduction
  • Channel types
  • Drop structures for open channel flow

2O-2 Open Channel Flow

  • Introduction
  • Definitions
  • Uniform flow (Manning's equation)
  • Energy flow
  • Non-uniform flow
  • Hydraulic jump
  • Hydraulic jump design example for trapezoidal channel
  • Solution nomographs

2P Stormwater Easements

2P-1 Stormwater Easements

References

2Q-1 References