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A description of the discharge, general rationale for development and implementation of <br />the storm water management program, and specific rationale for permit prohibitions, <br />receiving water limitations, and provisions follow. <br />II, Discharge Description and Location <br />The Dischargers have jurisdiction over and/or maintenance responsibility for storm drains <br />and watercourses that they own and/or operate in San Mateo County (See attached <br />location and political jurisdiction map). The discharge consists of storm water generated <br />in all hydrologic sub -basins which drain into watercourses which in tum flow into Lower <br />and South San Francisco Bay from the east side of the county or to the Pacific Ocean on <br />the west side. The quality of the discharge varies considerably and is affected by <br />hydrologic, geologic, land use, season, and sequence and duration of hydrologic events. <br />The major pollutants of concern expected in the discharge are heavy metals, excessive <br />sediment and nutrient loads, petroleum hydrocarbons, microbial pathogens, and <br />pesticides. <br />Ill. General Rationale <br />1. Water Quality Control Plan, San Francisco Bay Basin, June 21, 1995 (Basin Plan). <br />2. The Urban Runoff Management, Comprehensive Control Program section of the <br />Basin Plan requires the Dischargers to address existing water quality problems and <br />prevent new problems associated with urban runoff through the development and <br />implementation of a comprehensive control program focused on reducing'current <br />levels of pollutant loading to stone drains to the maximum extent practicable. The <br />Basin Plan comprehensive program requirements are designed to be consistent with <br />federal regulations (40 CFR 122-124) and are implemented through issuance of <br />NPDES permits to owners and operators of storm drain systems. The Dischargers, <br />having jurisdiction over and/or maintenance responsibility for municipally -owned and <br />operated storm drains and water courses within their boundaries, have assumed <br />responsibility for complying with the Basin Plan's requirements. The permit <br />recognizes submittal of the Plan as the Dischargers' Comprehensive Control Program <br />and requires implementation of the Plan. <br />The Basin Plan identifies the beneficial uses of waters and establishes water quality <br />objectives necessary to protect these beneficial uses which apply to certain receiving <br />waters within the Dischargers' boundaries. These water quality objectives serve as <br />receiving water limitations for waters that receive discharges of pollutants. <br />4. The Federal Water Pollution Control Act (Clean Water Act) as amended by the Water <br />Quality Act of 1987 (hereinafter CWA) Section 402(p) requires municipalities of <br />100,000 population or greater which have discharges from municipal separate storm <br />sewer systems to obtain NPDES permit coverage for these discharges. Permits are <br />also required for discharges that are determined to contribute to a violation of a water <br />