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WASTE DISCHARGE REQUIREM_ :S ORDER NO.R5-2004-XXXX -4- DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN SHARPE WASTEWATER TREATMENT FACILITY SAN JOAQUIN COUNTY Response Plan. This Order requires that the Discharger implement this Manual or subsequent updates approved by Regional Board staff. Site Specific Conditions 16. Annual precipitation in the vicinity averages approximately 13.31 inches. The mean pan evaporation rate is approximately 41.36 inches per year. 17. The facility lies within the San Joaquin Delta Hydrologic Unit Area No. 544.00, as depicted on interagency hydrologic maps prepared by the Department of Water Resources in August 1986. 18. The area surrounding DDJC-Sharpe is a mixture of industrial, agricultural, and residential. 19. Based on the National Resource Conservation Service soil survey, the soils in the proposed land application areas are Tinnin loamy coarse sand, Veritas fine sandy loam, Merritt silty clay loam, and Timor loamy sand. Published infiltration rates for the soils range from 0.3 to 3.0 in/hr. Based on boring log data from existing monitoring wells, shallow soils in the area are described as silty sand with clay lenses. 20. Approximately 208 groundwater monitoring wells, 34 piezometers, 45 extraction wells, and four drinking water supply wells are present at the Discharger's facility. The monitoring wells, piezometers, and extraction wells were installed as part of the on-going efforts to remediate several large groundwater plumes comprised primarily of trichloroethene and tetrachloroethene. These plumes have migrated beyond the western boundary of the facility,but the extraction well network is expected to achieve full-containment of the plumes in the next five years. The designated wastewater discharge areas are within or directly up gradient of the current capture zone of the extraction well network. The existing well network is considered to be adequate for monitoring discharge of treated wastewater. 21. Groundwater from the first aquifer, locally described as the A-aquifer zone, is not considered a viable source of drinking water without treatment for inorganics. The first aquifer contains elevated concentrations of arsenic and other inorganics. The Discharger has defined an ambient arsenic concentration of 273 gg/L for the first aquifer, which exceeds the Federal Maximum Contaminant Level (MCL) of 10 gg/L. Groundwater Degradation 22. State Water Resources Control Board(State Board) Resolution No. 68-16 (hereafter Resolution 68-16 or the"Antidegradation Policy")requires the Regional Board in regulating the discharge of waste to maintain high quality waters of the state until it is demonstrated that any change in quality will be consistent with maximum benefit to the people of the State, will not unreasonably affect beneficial uses, and will not result in water quality less than that described in the Regional Board's policies (e.g., quality that exceeds water quality objectives). 23. Continued operation of Discharger's facility is a benefit to the people of California, and therefore sufficient reason exists to accommodate limited groundwater degradation beneath the designated land application areas,provided that: