The Design and Use of Detention Facilities for Stormwater ...



The Design and Use of Detention Facilities for Stormwater Management

Detention ponds are probably the most common management practice for the control of stormwater. If properly designed, constructed, and maintained, they can be very effective in controlling a wide range of pollutants and peak runoff flow rates. There is probably more information concerning the design and performance of detention ponds in the literature than for any other stormwater control device. Wet detention ponds are also a very robust method for reducing stormwater pollutants. They typically show significant pollutant reductions as long as a few design-related attributes are met. Many details are available to enhance performance, and safety, that should be followed. Many processes are responsible for the pollutant removals observed in wet detention ponds. Physical sedimentation is the most significant removal mechanism. However, biological and chemical processes can also contribute important pollutant reductions. The extensive use of aquatic plants, in a controlled manner, can provide additional pollutant removals. Wet detention ponds also are suitable for enhancement with chemical and advanced physical processes.

This course will use the DETPOND stormwater detention pond model (model and documentation) to evaluate and design stormwater detention ponds for a wide range of conditions. DETPOND is based on the same modeling approach used in SLAMM, but provides more detail to enable more effective evaluations. This course also includes extensive documentation of successful pond designs and approaches.

This material is excerpted from: Pitt, R. Stormwater Quality Management, Part Two: Treatment of Stormwater. CRC/Lewis. Boca Raton, FL. Publication forthcoming.

The following is an abbreviated table of contents of the course material available from the downloadable pdf file:

Introduction 4

Expected Detention Pond Performance 5

Potential Detention Pond Problems 5

Wet Detention Pond Design Guidelines to Minimize Potential Problems 5

Required Stormwater Detention Pond Maintenance 6

Basic Wet Detention Pond Design Guidelines 6

Wet Detention Pond Costs 7

Pond Size Calculation 7

Background 7

Multiple Benefits of Detention Facilities 8

Dry Ponds 9

Wet Detention Ponds 9

Extended Detention (Combination) Ponds 9

Roof Storage 10

Up-Sized Pipes 10

Underground Rock-Filled Detention 10

Use with Other Controls 10

Examples of Detention Pond Performance 11

Oil/Water Separators 19

Problems With Wet Detention Ponds 24

Safety of Wet Detention Ponds 24

Nuisance Conditions in Wet Detention Ponds and Degraded Water Quality 26

Attitudes of Nearby Residents and Property Values 26

Maintenance Requirements of Wet Detention Ponds 27

Routine Maintenance Requirements 27

Sediment Removal from Wet Detention Ponds 28

Vegetation Removal from Wet Detention Ponds 29

Detention Pond Costs 30

Guidelines To Enhance Pond Performance 33

Insect Control and Fish Stocking 33

Aquatic Plants for Detention Ponds 33

Locating Ponds 41

Pond Surface Area and Shape 46

Pond Water Depth 46

Pond Side Slopes 47

Internal Baffles 47

Outlet Structures 47

Emergency Spillways 48

Multiple Detention Ponds and their use With Other Control Devices 48

Enhancing Pond Performance During Severe Winter Conditions 48

Detention Pond Design Fundamentals 50

Upflow Velocity 51

Effects of Short-Circuiting on Particulate Removals in Wet Detention Ponds 54

Residence Time and Extended Detention Ponds 57

Particle Size 59

Particle Settling Velocities 64

Pond Water Losses and Liners 66

Flow Rate Reductions In Water Quality Ponds 70

Control of Pollutants Other Than Suspended Solids 70

Natural Bacterial Dieoff in Detention Ponds 72

Design Based on NURP Detention Pond Monitoring Results 73

Importance of Reservoir Routing 75

Introduction To Storage-Indication Method 75

Outflow Rates From Discharge Control Devices 75

Stage-Area and Storage-Indication Curve Development 79

Storage-Indication Calculation Procedure 81

Selecting Outflow Control Devices To Meet Water Quality Objectives 88

Wet Pond Design Criteria for Water Quality 90

The Use of the DETPOND Program to Statistically Evaluate Wet Pond Performance 97

DETPOND Verification using Data Collected at the Monroe St. Detention Pond, Madison, WI 103

Method of Investigation 107

Data Analysis and Observations 107

Particle Size Distributions and Short-Circuiting 115

Monroe St. Pond Verification Conclusions 116

Verification Based on Measured Performance at a Landfill Pond in Birmingham, AL. 117

Issues Associated with Using a Continuous Record of Rains vs. a Single Event Storm 121

Stream Habitat Benefits Associated with Peak Flow Reduction Criteria 122

Untreated Flows Associated with Single-Event Criteria 123

Benefits of Using Continuous, Long-Term Simulations 123

Example Use of DETPOND and Wet Detention Pond Analyses 128

Analysis of the Wet Stormwater Detention Pond for the Brook Highland Shopping Center 128

The Use of DETPOND to Evaluate Wet Detention Pond for Minneapolis-St. Paul Airport 136

Design Suggestions for In-Receiving Water Detention 152

Retro-fit Examples for Providing Water Quality Benefits in Existing Dry Detention Ponds 156

Evaluation and Recommended Modifications to a Small Dry Stormwater Detention Pond 156

Retrofit of Dry Detention Pond in Sunnyvale, CA 166

Retrofit Case Examples from the Center for Watershed Protection (Claytor 1998) 174

Conclusions 177

References 178

Appendix A: User Guide for DETPOND 193

Example Design Calculations and Evaluation Using DETPOND 193

Steps in Entering Data for Evaluation in DETPOND 198

Example 1: Create a Rain File for Use in DETPOND 210

Example 2: Edit the Rain File Created in Example 1 211

Example 3: Create a Rain File from CD ROM Data 212

Example 4: Stochastically Generate a Rain File 213

Example 5: Create a Particle Size Distribution File 214

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