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are persistent and bioaccumulative in living organisms),and mercury.Potential sources of pollution for all the listed constituents in the basin include agriculture,resource extraction,and unknown sources. — Depending on location in the San Joaquin Valley, runoff may contain elevated levels of inorganic salts,including some toxic elements such as boron and selenium. Inorganic salts, in general,are present as a function of the soil chemistry and climate of the region.Naturally present salts within the soils of the Coast Range originate from the marine origin of the parent material deposited over millions of years.Rainfall leaches through the soil and picks up salt;high evaporation rates of the and climate further result in concentration of the salts in runoff.Additional salts are imported into the San Joaquin Valley via water that is diverted Brom the Delta and then applied for crop production.The salts are generally not utilized by crops,therefore,any salts that do not percolate to the groundwater can discharge directly to streams as irrigation return flow or be retained in the soil through evaporation and later be transported in rainfall runoff. Water quality conditions in the Delta are monitored extensively by the California Department of Water Resources (DWR)and U.S. Bureau of Reclamation(Reclamation)to guide SWP and CVP operations and maintain compliance with applicable water rights,biological opinions,and other water quality regulations contained in the 1995 Delta Water Quality Control Plan(refer to Section 4.8.2,"Regulatory Setting").DWR's Municipal Water Quality Investigations(MWQI)program also relies on data from automated monitoring stations to specifically track water quality conditions in the Delta that are important to the SWP.Table 4.8-1 shows a comparison of the average concentrations of the key salinity indicators total dissolved solids(TDS), electrical conductivity(EC), and specific ions of chloride and bromide measured over several years at selected locations in the Delta.These constituents are all important indicators of the quality of water sources used for drinking water and agriculture. The data illustrate that concentrations of these salinity indicators are higher in the west-central Delta at Rock Slough, a side channel located off of Old River that contains an important municipal water supply intake site.The north Delta has higher salinity resulting from its closer location to the tidal action and associated salinity that intrudes into the central Delta estuary from the ocean(California Bay—Delta Authority 2003). In the south Delta, water quality is largely influenced by the considerable input of dissolved mineral salts that are present in San Joaquin River flows.Regulatory EC objectives are routinely exceeded in the San Joaquin River at Vernalis, a site that is representative of water that flows downstream in Old River,whereas standards are typically met at the other monitoring locations in the Delta.DWR's stated salinity goal for the SWP Banks Pumping Plant is 220 milligrams per liter(mg/L)TDS as a long-term average and 440 mg/L TDS as a maximum monthly average. — Delta salinity conditions exhibit pronounced increases during the winter and low-flow summer and fall conditions when freshwater inflows have declined(California Bay—Delta Authority 2003).In addition,concentrations of all the salinity indicators are greater during critically dry water years than during wet or above-normal water years. Regulatory objectives for EC are routinely exceeded in the San Joaquin River at Vernalis,whereas desired standards are typically met at the other monitoring locations in the Delta.The SWP's stated salinity goal is 220 mg/L TDS as a long-term average and 440 mg/L TDS as a maximum monthly average.Contra Costa Water District(CCWD),which diverts most of its water from Old River and Rock Slough,has an established delivered water quality goal of 65 mg/L chloride concentration. Table 4.8-1 Comparison of Average Concentrations of Inorganic Salts at Delta Locations Location TDS(mg/L) EC(pS/cm) Bromide(mglL) Chloride(mglL) SWP Clifton Court Forebay 286 476 0.269 77 CVP Tracy Pumping Plant 258 482 0.269 81 CCWD intake at Rock Slough 305 553 0.455 109 San Joaquin River at Vernalis 459 749 0.313 102 Source:Adapted by EDAW In 2005 from California Bay—Delta Authority(2003)—summary of water quality data collected generally monthly from 1990 through 1998. EDAW College Park at Mountain House Specific Plan III Draft EIR Water Quality 4.8-2 San Joaquin County