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Using WinSLAMM For Stormwater Retrofit in Urban

EnvironmentsAugust 22, 2011

StormCon 2011, Anaheim, CA

Presented by:James Bachhuber PHCaroline Burger PE

AECOMMadison, WI

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Dense Urban Land Uses Require Stormwater Retrofitting Open space is very limited Land values are very high Treatment measures have higher

safety & aesthetic requirements

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Overview of Santa Monica Stormwater Study

Purpose of Study: Test WinSLAMM approach to stormwater

management Identify priority land uses for pollutant

generation Compare alternative stormwater

management for pollution control levels

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Overview of Santa Monica Stormwater Study

Basic Approach: Identify representative pilot study area Create WinSLAMM files to represent local

conditions Source areas Rainfall Drainage Soils

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Overview of Santa Monica Stormwater Study

Basic Approach (continued): Model pilot area with no management

measures (base condition) “Retrofit” alternative management

practices to predict runoff volume & pollution control achieved

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Overview of Santa Monica Stormwater Study

Stormwater Practices Analyzed: Street cleaning (vacuum assist) Porous pavement Infiltration Pits Biofilters

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Project Area – Land Use

Commercial; 52.58; 10% Residen-tial - high

dens; 86.76; 17%

Residential - med dens; 199.49; 40%

Residential - low dens; 130.64; 26%

School; 12.66; 3% Parks; 12; 2% Oceanfront dist; 7.04; 1%

Wilshire Drainage Area Land Use (acres, %) Total = 501 acres

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Project Area

Commercial Land Use

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Project Area

School Land Use

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Project Area

Medium Density Res. Land Use

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Project Area – Source Area Delineations

Source Areas

Residential – High Density

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Project Area – Source Area Delineations

Residential – Low Density

Source Areas

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Project Area – Source Area DelineationsSource Areas

Residential – Single Family

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Project Area – Source Area Delineations

Source Areas

Commercial

Project Area – Source Areas

Res - high dens.

Res - low dens

Res 1-Family Commercial0%

10%20%30%40%50%60%70%80%90%

100%

45% 41%26%

36%

1%0%

0%

17%

19%20%

20%

12%

19%14%

19%

28%5%

5%

0%

4%11%20%

35%

2%

Source Area Comparison

Landscape

Alley

Street

Sidewalk / Drive

Parking

Roof

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WinSLAMM Modeling ResultsWinSLAMM Model Comparison of Development Scenarios

100%

100%

100%

95%

95%

83%

95%

95%

78%

61%

56%

55%

8%

3%3%

0%10%20%30%40%50%60%70%80%90%

100%

Runoff Volume Annual TSS Load Annual TP Load

Conventional + SwalesRoof & 1 Sidewalk + Infiltration Basin+ Narrow Streets

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WinSLAMM Model InputsSource Areas in WinSLAMM:

Conventional LIDRoofs

Disconnected

Single Sidewalk

NarrowerStreets

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Model InputsWinSLAMM Road Swale Description:

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WinSLAMM Model InputsWinSLAMM Infiltration Basin Description:

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WinSLAMM Modeling ResultsWinSLAMM Model Comparison of Development Scenarios

100%

100%

100%

95%

95%

83%

95%

95%

78%

61%

56%

55%

8%

3%3%

0%10%20%30%40%50%60%70%80%90%

100%

Runoff Volume Annual TSS Load Annual TP Load

Conventional + SwalesRoof & 1 Sidewalk + Infiltration Basin+ Narrow Streets

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WinSLAMM Modeling ResultsWinSLAMM Model Comparison of Development Scenarios

100%

100%

100%

95%

95%

83%

95%

95%

78%

61%

56%

55%

8%

3%3%

0%10%20%30%40%50%60%70%80%90%

100%

Runoff Volume Annual TSS Load Annual TP Load

Conventional + SwalesRoof & 1 Sidewalk + Infiltration Basin+ Narrow Streets

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WinSLAMM Modeling ResultsWinSLAMM Model Comparison of Development Scenarios*

Development Scenario

Runoff Volume (ac ft/yr)

TSS Load

(lbs/yr)

Total P Load

(lbs/yr)Conventional Development 29.52 11,104 44.99

Disconnect Roofs & 1 Sidewalk 24.52 10,518 42.66

Add Narrower Streets 23.09 10,585 42.63

Add Roadside Swales 16.27 6,196 27.49

Add Infiltration Basin 0.95 318 3.64* Annual loadings from 43.2 acre Cedar Hills development

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Questions / Discussion

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