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WASTE DISCHARGE REQUIPMENTS 3 MARLEY COOLING TOWER COMPANY SAN JOAQUINCOUNTY TENTATIVE capture of the groundwater contamination plume. When cycling, water will be extracted primarily from the north zone near the site for a period and then, groundwater extraction will be from the area south of the site. Water extracted from the north zone will have higher chromium and copper concentrations. During south zone pumping,the capacity of the treatment plant will not be utilized fully unless supplemental waste sources are added. Flushing water may be added to supplement the groundwater concentrations. In either mode,when sufficient storm water is accumulated on the North Yard to justify treatment,the operator will manually initiate storm water treatment through the electrochemical unit. Groundwater from selected wells will simultaneously be delivered to the ion exchange unit. 12. The sequence of alluvial sediments underlying the MCTS facility from the water table to depths of at least 450 R below ground surface (bgs) comprises one aquifer. The water table is approximately 40 to 60 ft bgs. This aquifer is characterized by discontinuous lenses of sand, gravelly sand, clayey silt, silty clay, and clay. The aquifer underlying the MCTC facility can be divided into four hydrostratigraphic subunits: a)the shallow zone (water table to approximately 80 ft bgs),b)the 100 ft zone (approximately 80 to 120 ft bgs), c)the intermediate zone (approximately 120 feet to depths ranging from 170 to 200 bgs) and , d)the deep zone extending from below 200 ft bgs to approximately 450 ft bgs. 13. The Report of Waste Discharge describes the discharge to groundwater as follows: Average Flow: soil flushing 35 gallons per minute Treatment Plant Capacity: 0.94 mgd Average Temperature: Ambient(summer/winter) pH: 6.5 minimum— 8.5 maximum Constituent Daily Maximum, cell Outfall Number 001 (soil flushing) Total Chromium 50 Chromium VI 11 Copper 6.6 Arsenic 10 Total Dissolved Solids (TDS) 1000 mg/l PROPOSED CHANGES 14. The Discharger proposes to conduct a pilot study for remediation of hexavalent chromium in soil in the retort pit area and groundwater to reduce the anticipated cleanup time of the aquifer. The Discharger proposes to inject a chemical reducing agent(sodium dithionite) or an organic carbon source(ethanol)to stimulate microbial growth and produce reducing conditions in the retort pit area. The pilot study is based on the results of a review of the groundwater geochemistry at the Site. The Discharger proposes to inject sodium dithionite or ethanol into groundwater and vadose zone in two distinct phases,to reduce hexavalent chromium to trivalent 08/22/02 2:02 PM Marley Cooling