FIELD DOCUMENTS AND WORK PLANS 1992-1999

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INFORMATION SHEET -2- MARLEY COOLING TOWER COMPANY STOCKTON, SAN JOAQUIN COUNTY crossing. Upper Mormon Slough is actually the South Fork of the Calaveras River below Bellota. From 1 October to 1 April every year, the East Stockton Water District dams the Calaveras River at its fork with Upper Mormon Slough, thus diverting all flows through Upper Mormon Slough and the Stockton Diverting Canal . From 1 April to 1 October every year, flows are split between the Calaveras River and Upper Mormon Slough. A series of check dams are installed along the Calaveras River, Upper Mormon Slough, and the Stockton Diverting Canal to provide irrigation water for adjacent farmers. During this time, there are periods of no flow in the Stockton Diverting Canal . MCTC submitted a Report of Waste Discharge (RWD) which requested an increase in the treated water flow from the treatment plant. MCTC proposed in the RWD an expansion of the on-site ground water treatment facility to control contaminant movement. An electrochemical reduction and precipitation treatment plant will be expanded and used in parallel with the existing ion exchange treatment system. Flows have been proposed to be increased to a maximum of 1.01 mgd (0.72 mgd average) . Ground water treatment will consist of various combinations of the following unit processes: flow equalization, reduction, precipitation, settling, filtration, pH adjustment and ion exchange. A Remedial Investigation / Feasibility Study has been conducted and in August 1990, the final Remedial Action Plan (RAP) was adopted by the DHS. The recommended ground water remedial action in the RAP included an increase to 0.72 mgd in the discharge of the treated ground water and/or storm water. A revised monitoring program has been prepared for the new plant. The adoption of the modified waste discharge requirements will expedite ground water cleanup by increasing flows. Basis for Effluent Limitations Effluent limits on discharge to the Stockton Diverting Canal are based on water quality objectives established by the "California Inland Surface Waters Plan" . Limits were set at 6.5 µg/l for Copper, 11 µg/1 for Hexavalent Chromium, 50 µg/l for Total Chromium, 5.0 µg/1 for arsenic and 500 mg/l for Total Dissolved Solids for protection of freshwater aquatic life and protection of Human Health. Reuse of a portion of the effluent discharge a soil flushing water has more relaxed limits and are based on technologically acheivable limits set at 65 µg/l for Copper, 50 µg/1 for Total Chromium, 5 µg/l for Arsenic and 640 mg/l for Total Dissolved Solids.