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WASTE DISCHARGE REQUIREMENTS -2- <br /> MARLEY COOLING TOWER COMPANY <br /> SAN JOAQUIN COUNTY <br /> operations are necessary. The modification was specifically requested for <br /> an increase in the treated water flow from the treatment plant. <br /> 6. The RWD consisted of five technical documents entitled "Suggested Revisions <br /> to NPDES Permit" , "Operation Description for Interim System" , "Performance <br /> Monitoring of the Interim System" , "Technical Report on Existing Water <br /> Treatment Plant Operation" and "Plan for Evaluation of Treated Water <br /> Disposal Alternatives" . <br /> 7. The Discharger, as proposed in the RWD, intends to expedite the extraction <br /> and expansion of the existing on-site water treatment facility by <br /> increasing flows to 0.59 mgd to the same outfall point in the Stockton <br /> Diverting Canal . The increase in the extraction and the expansion are <br /> needed to control off-site contaminant movement caused by recent changes in <br /> ground water gradients in the vicinity of the North Yard. Ground water <br /> will be extracted from extraction well EW-1 and monitoring wells MW-213 and <br /> MW-214. <br /> 8. The Discharger intends to construct an new electrochemical reduction and <br /> precipitation treatment plant to remove contaminants from the water, as <br /> shown on Attachment B, incorporated herein and made part of this Order. <br /> This system will be operated in parallel to the existing ion exchange <br /> treatment system. The new system should be on-line in January 1991. <br /> Ground water treatment will now consist of various combinations of the <br /> following unit processes: flow equalization, reduction, precipitation, <br /> settling, filtration, pH adjustment and ion exchange. <br /> 9. The new interim treatment plant consists of an electrochemical reduction <br /> and precipitation process which uses iron as the reducing agent for the <br /> hexavalent chromium followed by iron co-precipitation using pH adjustments. <br /> The addition of polymers and further pH adjustments are used to optimize <br /> settling. The effluent is then filtered prior to discharge. The solids <br /> from the clarifier are pumped and accumulated in a filter press. The <br /> filter cake is tested and taken off-site for disposal . The filter press <br /> filtrate and mixed media filter backwash drain to the existing sludge <br /> drying beds for the accumulation of additional solids. <br /> 10. The RWD describes the stormwater and ground water influent characteristics <br /> as follows: <br /> Average Flow: Existing Plant - 0.374 mgd <br /> Interim Plant - 0.216 mgd <br /> Average Temperature: Stormwater - ambient <br /> Ground water - 68° F <br /> pH: Ground water - 7.0 to 7.5 <br />