Low-Impact Development
A Growing Trend in Storm Water Management
By Robia S. Chang and Carolyn Nelson Rowan
Communities are increasingly using an approach known as "low-impact development" (LID) to control storm water pollution. Instead of making large investments in complex and costly engineering strategies for municipality-wide storm water management, LID manages storm water through lot-level design strategies that mimic natural hydrology and processes. LID is customized by development and implemented on site by developers. LID addresses runoff close to the source, for example, by disconnecting roofs and paved areas from traditional drainage infrastructure and directing runoff to natural areas such as vegetated open spaces, which look like landscaped areas but are actually engineered systems that use plants and soil to trap and treat various contaminants. Other common LID practices include rooftop gardens, tree planter boxes and the use of permeable pavement in low-traffic areas, parking areas and walking paths.
For the most part, LID has been a voluntary approach, promoted by localities and adopted by developers. But recent developments in California permitting signal an increasing trend to require implementation of LID techniques.
Earlier this year, the San Diego Regional Water Quality Control Board approved a storm water runoff permit that will require the San Diego County, the Port District and the county's 18 cities to increase the testing and monitoring of runoff, street sweeping and sewer-line cleaning. Significantly, the renewal permit also requires the use of LIDs to control storm water pollution. Specifically, the permit requires routing of runoff from impervious to pervious areas and the use of permeable surfaces for portions of low-traffic areas. All sites greater than one acre will be subject to these same permit conditions within the next three years.
Similarly, a draft permit issued to Ventura County by the Los Angeles Regional Water Quality Control Board requires that all new development and redevelopment projects integrate LID principles into project design. The permittees, including the County Watershed Protection District, the Ventura County and 10 cities within the county, are to develop a LID Technical Guidance Document for use by planners and developers within 18 months of the issuance of the permit.
Most recently, on May 1, 2007, the San Francisco Bay Area's draft permit, which covers 76 municipalities, was released for review. As expected, all "regulated projects" must integrate LID principles. "Regulated projects" include commercial development projects that create 10,000 square feet or more of impervious surface (collectively over the entire project site), excluding interior remodels and routine maintenance or repair. Beginning the fourth year after permit adoption, the square footage threshold will drop to 5,000 square feet.
These regional developments in storm water management signal widespread change within California. As the focus of long-term planning shifts to include a more thorough review of environmental impacts, developers should expect that all state and local jurisdictions regulating storm water will require LID storm water pollution control for future developments.
June 2008 Commercial Edition Issue
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