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4. ENVIRONMENTAL ANALYSIS 4.8 HYDROLOGY AND WATER QUALITY Surface Water Quality There is no available data on water quality for site-specific and local tributary streams and drainages. However,based on data gathered from regional water quality studies conducted by the California Regional Water Quality Control Board(RWQCB), it appears that the water quality in area surface streams and agricultural drainages have high total dissolved solids (TDS), and elevated concentrations of nutrients,pesticides, and salinity (RWQCB, 1983). As part of a regional analysis of water quality, the RWQCB tested the Ingram Creek and Hospital Creek for the pesticide diazinon. Sixteen of the 32 samples(50%)analyzed for diazinon exceeded the California Department of Fish and Game(CDFG)chronic water quality criterions for diazinon, and eleven of the 32 samples(34%)exceeded the CDFG acute criterion. Consequently,recent reports by the RWQCB lists Ingram Creek and Hospital Creek as an impaired water body due to the presence of the pesticide-related chemicals chlorpyrifos and diazinon in agricultural return flows. Regardless, Hospital Creek and Ingram Creek are considered a low priority for future Total Maximum Daily Load(TMDL)designation for agricultural chemicals(CVRWQC, 2002). 6 Water quality in the major aqueducts and other water supply conveyance facilities is monitored regularly and is maintained at high standards due to the co-mingling of surface water and groundwater in the downstream San Luis Reservoir system operated by the U.S. Bureau of Reclamation(USBR). GROUNDWATER HYDROLOGY For the purposes of this EIR, information regarding the water bearing units and groundwater hydrology was derived from: • Water level monitoring data from the Department of Water Resources Water Data Library, Groundwater Level Data(California Department of Water Resources [DWR], 2004), • Bulletin 118, San Joaquin River Hydrologic Region,California's Groundwater(DWR, 2003a), • Reclamation Plan for the Applicant for RMC Pacific Vernalis Quarry (Spinardi Associates, 2002), • Preliminary Geological/Geotechnical Study for Quarry Pit Excavation(Geomatrix, 2002), and 5 Chronic water quality criterion refers to the toxicity of compounds in the water which is the degree to which a substance or a mixture of substances can harm humans or animals. The EPA conducts toxicity assessments to characterize the properties and effects of chemicals and compounds,with special emphasis on the establishment of dose-response characteristics. The EPA uses a scale of toxicity,from acute to subchronic,for measuring the harmfulness of each substance. Chronic toxicity refers to the effects of repeated or long-term exposure to a substance while acute toxicity refers to the short-term effects of a one-time exposure to a chemical substance. J 6 Total Maximum Daily Load(TMDL)is a determination of the capacity of a water body to assimilate certain pollutants. TMDLs will eventually become an integral part of surface water quality regulation. The RWQCB is currently determining TMDLs for high priority water bodies in California. RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.8-4 FSA/203015 Adminiatmuve Draft EIR March 2004