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

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~ , , toxins, oxygen-demanding substances (organic material), pesticides, petroleum derivatives, and floatables. Construction sites also can generate other pollutants associated with onsite wastes, such as sanitary wastes, construction chemicals, solid waste or concrete truck washout, when after a rain, storm water runoff carries these pollutants into nearby streams, rivers, lakes, estuaries, wetlands, and oceans. Estimates indicate that 80 percent ofthe phosphorus and 73 percent of the Kjeldahl nitrogen in streams is associated with eroded sediment. In watersheds experiencing intensive construction activity, the localized impacts of water quality may be severe because of high pollutant loads, primarily sediments. Siltation is the largest cause of impaired water quality in rivers and the third larges cause of impaired water quality in lakes. Construction site discharges were a source of pollution in: 6 percent of impaired rivers; II percent of impaired lakes, ponds, and reservoirs; and II percent of impaired estuaries. Rules EP A is applying NPDES permit requirements to construction sites below 5 acres that are similar to the existing requirements for 5 acres and above. The rule addresses all storm water discharges from construction site activities. The definition of "storm water discharges associated with small construction activity" includes discharges from construction activities, such as clearing, grading, and excavating activities, that result in the disturbance of equal to or greater than I acre and less than 5 acres. This also includes discharges from activities disturbing less than 1 acre if that construction activity is part of a "larger common plan of development or sale" with a planned disturbance of equal to or greater than I acre of land. A "larger common plan of development or sale" means a contiguous area where multiple separate and distinct construction activities are planned to occur at different times on different schedules under one plan. Such activities could include: road building; construction of residential houses, office buildings, or industrial buildings; or demolition activities. The NPDES permit also includes any other construction activity, regardless of size, designated based on the potential for contribution to a violation of a water quality standard or for significant contribution of pollutants to waters of the United States. In construction projects involving a larger common plan of development or sale ultimately disturbing 5 or more acres, operators of these sites are required to seek coverage under an NPDES permit regardless of the number oflots in the larger plan because designation for permit coverage is based on the total amount ofIand area to be disturbed under the common plan. Currently, when construction activity disturbing more than 5 acres occurs on an industrial site covered by the MSGP (Multi-Sector General Permit), authorization under a separate NPDES construction permit is needed because the MSGP does not include the "construction" industrial sector. The NPDES general permit for discharges from construction sites larger than 5 acres defined "commencement of construction" as the initial disturbance of soils associated with clearing, grading, or excavating activities or