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Stormwater Case Studies Search ResultsCase Study Location: Maryland: Prince George's County Case Study Title: Incorporating Low Impact Development into Stormwater Management Minimum Control Measure: Post-construction stormwater management in new development and redevelopment Summary: Location: Maryland: Prince George's County Contact Information: Chris Akinbobola Description: The Prince George's County's Department of Environmental Resources (DER) sought to develop a more cost-effective approach to stormwater management that provided both flood control and water quality benefits. In the early 1990s the County experimented with plant/soil filter techniques, which led them to develop a lot-level runoff management concept called low impact development (LID). The County produced local and national guidance on LID design techniques that describe in detail the steps needed to develop lots that mimic the hydrologic functions of a natural landscape. In 1990, the DER was faced with the task of managing stormwater under the NPDES Phase I Stormwater Rule. Conventional best management practices, which had been implemented throughout Prince George's County, had proven to be costly to maintain and inspect and fell short of the water quality goals the County sought to achieve. An additional challenge the DER faced in such an urbanized County was the daunting task of retrofitting areas already developed using capital-intensive, end-of-pipe structural stormwater treatment controls.
As a solution to these challenges, the County experimented with bioretention, or "rain gardens," which use small, low-lying landscaped areas to capture and infiltrate runoff on-site. Experience with these practices led them to develop a strategy for engineering lot-level landscapes that can function (hydrologically) like a natural landscape. This strategy evolved into the LID design approach, which involves directing runoff from impervious surfaces, such as rooftops, driveways, sidewalks, and streets, to grassed or other landscaped areas. This slows the runoff and provides treatment through filtration, settling, and biological uptake of pollutants. The ultimate goal of the LID design approach is to provide in situ management of runoff from impervious surfaces to reduce end-of-pipe treatment costs and protect headwater streams that would otherwise be vulnerable to degradation from erosive storm flows and high pollutant loads. The success of LID applications in Prince George's County led to the development of two national guidance manuals by Prince George's County's Department of Environmental Resources with assistance from EPA. Low-Impact Development Design Strategies: An Integrated Design Approach [PDF] expands the scope of Prince George's County's 1997 local design manual to be applied nationwide. The manual
In recent years, other communities, non-profit groups, private businesses, and federal agencies have implemented LID design and developed additional guidance and resources (see Additional Resources and Tools). Because of the economic and water quality benefits of this approach, LID has gained wide appeal, and its concepts have become standard practice in many communities dedicated to improving water quality. Additional Materials Related to this Case Study:
Additional Resources and Tools for this Minimum Control Measure EPA presents this case study as an example to which Phase I and Phase II municipal stormwater programs can refer as they develop their own stormwater programs. Although EPA has reviewed the case studies, they should not be considered officially endorsed by the Agency and are not intended to represent full compliance with EPA’s stormwater Phase II minimum control measures. Each community must decide on the appropriate BMPs necessary to meet its unique permit requirements and local conditions. |
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