Low-Impact Development 2008 Page 1 Low-Impact Development [Reference: Jones, Phillip. 2004. Low Impact Development: Stormwater Management Meets Environmental Protection. CE News. July 2004.] (Link to publication)Low Impact Development (LID) is a relatively new practice that attempts to unite site planning, land development, and stormwater management with ecosystem protection. It was first developed in the 1990s in response to the economic and environmental impacts of conventional stormwater management techniques. Put briefly, LID is a comprehensive development and design technique with the goal of preserving predevelopment hydrology and water quality through a series of small-scale, distributed structural and non-structural controls. Numerous local jurisdictions around the country also have expressed a continuing interest in LID training and demonstration projects. Several branches of the armed services have recognized LID as an important planning and design tool for their facilities. The Low Impact Development Centeris a nonprofit organization dedicated to research, development, and training for water resources and natural resource protection issues. It represents an excellent resource for additional information about low-impact development. Visit the Center at http://www.lowimpactdevelopment.org. Benefits of the LID Approach LID projects commonly are implemented because they reduce lifecycle costs for stormwater infrastructure and shifts maintenance burdens away from local governments. Additionally, they provide superior control of non-point-source pollution, and hydrologic control of small, frequently occurring storms and their effects on downstream ecology. Other benefits include National Pollution Discharge Elimination System (NPDES), Phase II Final Rulecompliance, Combined Sewer Overflow (CSO) mitigation, community development, and watershed pollutant load management. The EPA has established a web site dealing with storm water management at http://www.stormwatercenter.net/that serves as a resource for ideas on conserving water and managing storm water. The site includes a link to the A primary concern with the traditional "pipe-and-pond" approach to stormwater management has been poor control of small, frequent storms.Because the minimum design storm is often the one- or two-year storm, the peak rate, the runoff volume, and the pollutant loading of small, frequent storms is not attenuated, even though they account for the majority of the annual precipitation volume. (For example, 70 percent of the annual precipitation volume in Washington, D.C., comes from storms of 1 inch or less.) Most urban pollutants are conveyed in the first ½-inch to 1-inch of rainfall. Because conventional management strategies are intended for larger storms, they do little to address non-point-source pollution from these "first flush" events and may not assist with NPDES Phase II compliance. Additionally, failing to adequately manage small storms contributes to stream channel erosion.
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