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Water quality conditions within the College Park project site have not been specifically evaluated.The project site has historically been used for agriculture, including crops,pasture,and dairies.Agricultural land uses are generally known to result in relatively high discharge rates of sediment,nutrients,and pesticides that are a result of tillage and land disturbance and chemical applications. Surface runoff typically occurs during the winter rainfall season and can be expected to potentially have elevated suspended solids content resulting from soil erosion.Inorganic mineral content in runoff from the watershed would likely reflect the mineral composition and erodibility of local soils and any human-caused discharges, such as fertilizer nutrients(e.g.,nitrogen and phosphorus),locally-used pesticides and herbicides,and specific trace metals. Diazinon and chlorpyrifos are specific organophosphate pesticides of concern to the Central Valley Regional Water Quality Control Board(RWQCB), and the Delta is included on the U.S.Environmental Protection Agency .. (EPA) 303(d)list described above as impaired for these compounds from agricultural and urban runoff sources. No specific information is available regarding the past and current use of these products within the project area; however,both pesticides have been widely used throughout the region. Diazinon can be a problem particularly during winter rainfall periods because it is used for dormant-season pest control and is highly soluble in water. However,the registration for diazinon for over-the-counter residential sales has been cancelled, and use is expected to decline as the product is phased out. Chlorpyrifos is generally much less soluble in water and is strongly adsorbed by soil particles. GROUNDWATER HYDROLOGY AND WATER QUALITY Groundwater hydrology and groundwater quality in the project study area have not been well quantified because of the sparse population,the predominantly rural land uses,and the fact that the Mountain House community does not use groundwater for any of its water supply.The MHMP EIR identified that wells in the area typically have relatively high TDS concentrations.The salinity content of the groundwater may be related to subsurface seawater intrusion from the Delta or may reflect background groundwater conditions. Some wells in the area at the time of preparation of the MHMP EIR had elevated levels of nitrate and sulfides that may have indicated the presence of wastes from nearby dairies or domestic septic tanks. 4.8.2 REGULATORY SETTING FEDERAL REGULATIONS The EPA is the lead federal agency responsible for water quality management.The federal Clean Water Act of 1972 (CWA)is the primary federal law that governs and authorizes water quality control activities by the EPA as well as the states.Various elements of the CWA address water quality and are discussed below.In California,the EPA has designated the SWRCB and its nine regional water quality control boards(RWQCBs)as the state agencies having the authority to administer and implement many of the regulations and programs mandated under the CWA. Water Quality Criteria and Standards Section 303 of the CWA requires states to adopt water quality standards for all surface waters of the United States.As defined by the CWA,water quality standards consist of two elements: (1)designated beneficial uses of the water body in question and(2)criteria that protect the designated uses.CWA Section 304(a)requires the EPA to publish advisory water quality criteria that accurately reflect the latest scientific knowledge about the kind and extent of all effects on health and welfare that may be expected from the presence of pollutants in water. Where multiple uses exist,water quality standards must protect the most sensitive use. Section 303(d) Impaired Waters List Under Section 303(d) of the CWA, states are required to develop lists of water bodies that would not attain water quality objectives after implementation of required levels of treatment by point-source dischargers(municipalities College Park at Mountain House Specific Plan III Draft EIR EDAW San Joaquin County 4.8-3 Water Quality