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III. Environmental Setting,Impacts, and Mitigations K. Hydrology,Geohydrology, and Water Quality Waste Discharge Requirements Order Number 90-122(because the well was contaminated). Groundwater samples from production wells, monitoring wells and hydropunch holes have been tested for Volatile Organic Compounds(VOCs). Chlorinated hydrocarbons are the only volatile organic compounds(VOCs)detected at concentrations greater than established maximum contaminant levels. The City is implementing a Corrective Action Plan(CAP)approved by the RWQCB. The CAP design includes the installation of a groundwater extraction and treatment system to mitigate the detected chlorinated hydrocarbons(R.W. Beck and Associates, 1992a). Surface Water The California Department of Water Resources is responsible for assessing the quality of all the State's water resources and has been monitoring water quality for many years. However, much of the long term data emphasizes mineral parameters,rather than toxic organic pollutants and none of the DWR water quality monitoring stations are located in the local watershed(DWR, 1985). The stations on the San Joaquin River are not necessarily representative of individual contributing basins, such as Little Johns Creek. Under existing conditions irregular surface grading of the landfill site and erosion along the margins of the creek has permitted runoff that has contacted wastes to co-mingle with storm runoff that has not contacted wastes,and sediment and wastes have entered the stream channel.2 The RWQCB (Order 90-122)has required monitoring samples to be collected quarterly from Little Johns Creek and analyzed for Total Organic Carbon(TOC),Total Dissolved Solids(TDS) Hardness(as Ca CO2),field pH,and specific conductance(µmhos/cm). However,the surface water monitoring program has not been able to obtain samples in every quarter,due to the lack of water in the Creek(the lack of water is attributed to normal seasonal variability,compounded by the effects of recent drought conditions)(see Table III.K.2). [City: please provide more monitoring data if and/or when available.] 2 Field observation in March 1993 by ESA staff indicated that several areas of the landfill surface bad rills and gullies with evidence of water and sediment(including waste)transported directly to the Creek along the southern margin of the existing landfill and to offsite agricultural fields on the north side of the landfill(across the road). III.K.9