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WASTE DISCHARGE REQUIREMENTS -2- <br /> MARLEY COOLING TOWER COMPANY <br /> SAN JOAQUIN COUNTY <br /> 6. The DTSC, following discussions with Board staff, formally adopted the RAP <br /> on 29 August 1990, which included the conceptual design of the ground water <br /> remedial project. <br /> 7. The recommended ground water remedial action in the RAP includes the <br /> discharge of up to 0.72 mgd of treated ground water and storm water to the <br /> Stockton Diverting Canal . In order to minimize the local dewatering of the <br /> aquifer caused by overdraft and to restore the aquifer as a usable drinking <br /> water source by recharge of the treated ground water and/or storm water, <br /> reuse and aquifer reinjection were to be evaluated as discharge <br /> alternatives. The findings were that rejection into the intermediate <br /> aquifer is technically feasible and is 16% more expensive to implement than <br /> surface water discharge. <br /> 8. The Discharger has been operating a treatment system for contaminated <br /> ground water and storm water since October 1987. The discharge is <br /> presently regulated by Order No. 88-124 (NPDES No. CA0081787) , adopted by <br /> the Board on 24 June 1988. Revision of the current permit is required <br /> under Chapter 5.5, section 13380 of the Water Code for an increase in the <br /> treated water flow from the treatment plant and to incorporate reinjection <br /> of approximately 2% of the treated water for the purposes of flushing soils <br /> contaminated with chromium, copper, and arsenic attributed to the former <br /> wood preserving process. Full capture of reinjected treatment water is <br /> proposed. <br /> 9. The Discharger, proposes to expand the extraction of the existing on-site <br /> ground water treatment facility by increasing the treatment capacity to <br /> treat flows to 0.72 mgd, discharging to the same outfall point in the <br /> Stockton Diverting Canal . The increase in ground water extraction and the <br /> expansion of the treatment plant are needed to control contaminant <br /> migration and remediate the underlying aquifer to meet cleanup levels as <br /> well as treat storm water. Ground water will be extracted from 17 <br /> extraction wells on and off-site. <br /> 10. The site is divided into two areas, the North Yard and the South Yard. All <br /> past wood treatment activities were conducted on the North Yard. Rain <br /> falling on the North Yard would become contaminated after contact with <br /> treated cooling tower components. This contaminated rainwater is collected <br /> in a storm drain system and continues to be discharged to the treatment <br /> plant in the northeast portion of the site. Due to storage of treated wood <br /> products on the MCTC South Yard, some wood treating chemicals have been <br /> detected in the storm water runoff from the South Yard. Residual <br /> contamination exists in ditch sediments and walls of pipes leading to <br /> offsite ditches draining the area. Runoff from the South Yard is not <br /> regulated and will be under the revised permit. <br /> 11 . The Discharger has constructed an expanded ground water treatment plant <br /> including a new electrochemical reduction and precipitation unit to remove <br /> contaminants from the water. This system will be operated in parallel to <br />