2003-04-01 P & Z Agenda - Laserfiche WebLink

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. . , Non-Point Pollution Discharge Elimination System (NPDES) - Phase II Prepared by Brian Hanson Introduction The NPDES rule goes into effect on March 10,2003. This rule establishes a cost- effective, flexible approach for reducing environmental harm by storm water discharges from many point sources of storm water that were currently unregulated. EP A believes that implementation of Best Management Practices (EMP) controls at small construction sites (construction sites that disturb one to five acres) will also result in a significant reduction in pollutant discharges and an improvement in surface water quality. The NPDES program is a program designed to track point sources and require the implementation ofthe controls necessary to minimize the discharge of pollutants. Today's rule, which is the second phase of the storm water program, expands the existing program to include discharges of storm water from smaller municipalities in urbanized areas and from construction sites that disturb between one and five acres ofland. Backl!round EP A believes that the water quality impact from small construction sites is as high as or higher than the impact from larger sites on a per acre basis, and nearly 61 percent ofthe construction sites that were 1 acre or larger were between 1.0 and 4.9 acres in size. A primary concern at most construction sites is the erosion and transport process related to fine sediment because rain splash, rills (i.e., a channel small enough to be removed by normal agricultural practices and typically less than I-foot deep), and sheetwash encourage the detachment and transport of this material to waterbodies. Uncontrolled storm water discharges from areas of urban development and construction activity negatively impact receiving waters by changing the physical, biological, and chemical composition ofthe water, resulting in an unhealthy environment for aquatic organisms, wildlife, and humans. Twenty-one states reported storm water runoff from construction sites as a major cause of beneficial use impairment. Over a short period of time, storm water runoff from construction site activity can contribute more pollutants, including sediment, to a receiving stream than had been deposited over several decades. During the largest storm event, it was estimated that 80 percent ofthe sediment in the stream originated from the construction sites. Therefore, small construction sites can cause or contribute to an exceedance of water quality standards by changing natural hydrologic patterns, accelerating stream flows, destroying aquatic habitat and elevating pollutant concentrations and loadings. Such runoff may contain or mobilize high levels of contaminants, such as sediment, suspended solids, nutrients (phosphorous and nitrogen), heavy metals and other toxic pollutants, pathogens,