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Stormwater Overview

The Environmental Protection Agency (E.P.A.) recently initiated a national rulemaking to establish a comprehensive program to reduce stormwater runoff from new development and re-development projects, and make other improvements to strengthen its stormwater program. The E.P.A. announced that during this rulemaking process it will evaluate sustainable green infrastructure design techniques that mimic natural processes to evapo-transpire, infiltrate and recharge, and harvest and reuse stormwater. 

The EPA asked ASLA to collect case studies on projects that successfully and sustainably manage stormwater. ASLA members responded with 479 case studies from 43 states, the District of Columbia, and Canada. Not only do these projects showcase landscape architecture, they also demonstrate to policymakers the value of promoting green infrastructure policies. Green infrastructure and low-impact development (LID) approaches, which are less costly than traditional grey infrastructure projects, can save communities millions of dollars each year and improve the quality of our nation’s water supply. 

An analysis of the case studies:  

Project type:
Institutional/Education — 21.5% 
Open Space/Park  — 21.3%
Other  — 17.6%
Transportation Corridor/Streetscape —  11.9%
Commercial —8.6%
Single Family Residential  — 5.5%
Government Complex — 4.2%
Multifamily Residential — 3.7%
Open Space-Garden/Arboretum  —2.9%
Mixed Use — 1.8%
Industrial — 1.1%


Estimated cost of green infrastructure:
$100,000–$500,000 — 29.2%
$1,000,000–$5,000,000 — 22.1%
$500,000–$1,000,000 — 13.2%
$50,000–$100,000 — 12.9%
$10,000–$50,000 — 12.1%
<$5,000,000 — 7.0%
>$10,000 — 3.5%

Green infrastructure type:
Retrofit of existing property — 50.7%
New development — 30.7%
Redevelopment project — 18.6%

How much impervious area was managed?
1 acre to 5 acres — 34.5%
5,000 sq/ft to 1 acre — 31.3%
greater than 5 acres — 24.8%
less than 5,000 sq/ft — 9.5%

Did use of green infrastructure increase costs?
Reduced costs — 44.1%
Did not influence costs — 31.4.7%
Increased costs — 24.5%

Green infrastructure design approaches used:
Bioswale — 62.1%
Rain garden — 53.2%
Bioretention facility — 50.8%
Permeable pavement systems — 47.3%
Curb cuts — 37.9%
Cistern — 21.2%
Downspout removal — 18.1%
Green roof — 16.5%
Rain barrels — 5.7%

Analysis

  • Over 300 ASLA members and other practitioners responded with 465 case studies
  • Case studies were submitted from 43 states, the District of Columbia, and Canada.
  • 55 percent of the projects were designed to meet a local ordinance.
  • 88 percent of local regulators were supportive of the green infrastructure projects submitted.
  • 68 percent of the projects received local public funding.
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EPA Office of Water
ASLA Water and Stormwater
Campaign for Green Infrastructure
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