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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2003-XXXX • 2 $PX CORPORATION MARLEY COOLING TOWER COMPANY SAN JOAQUIN COUNTY this Order, which requires total recapture of groundwater. 5. The discharge of treated groundwater to the Stockton Diverting Canal was previously regulated by Waste Discharge Requirements(WDR) Order No. 93-221, NPDES Permit No. CA0081787, which was adopted by the Regional Board on 22 October 1993. Under this Order, the Discharger was permitted to extract groundwater and discharge a maximum of 0.94 million gallons per day(mgd) of treated groundwater and storm water runoff to the Stockton Diverting Canal, a water of the United States and a tributary to the Calaveras River, at 37 degrees, 58 minutes, 19 seconds latitude and 121 degrees, 13 minutes, and 34 seconds longitude. The discharge pipeline and discharge point (Outfall 001) are shown on Attachment B. 6. The groundwater treatment system at the plant includes an electrochemical reduction and precipitation unit operating in parallel to an ion exchange treatment system. 7. The ion exchange system consists of two anion exchange vessels and a cation exchange vessel. In the anion exchange vessels, hexavalent chromium in the water is adsorbed onto the ion exchange resins. In the cation exchange vessel, trivalent chromium and copper are adsorbed. The exchange process continues until the resin's exchange sites are filled and exchange capacity is exhausted. The adsorbed wood treating chemicals are stripped from the ion exchange resins and the resins are conditioned for additional water treatment in a process called regeneration. During regeneration,which occurs approximately every 2.5 days, 15,000 gallons of solution containing the stripped chemicals is removed from the ion exchange system and processed through the electrochemical unit. 8. The electrochemical unit consists of an electrochemical reduction (Andco) and precipitation process which uses iron as the reducing agent for the hexavalent chromium followed by iron co-precipitation using pH adjustments. The addition of polymers and further pH adjustments are used to optimize settling. The effluent is then filtered prior to discharge. The solids from the clarifier are pumped and accumulated in a filter press. The filter press filtrate and mixed media filter backwash are returned to the treatment plant for further treatment. Filter press cake has been characterized as a Califomia hazardous waste, and is collected in roll off bins for off-site disposal. 9. The site is divided into two areas,the North Yard and the South Yard. All past wood treatment activities were conducted on the North Yard. Rain falling on the North Yard becomes contaminated after contact with treated cooling tower components. This contaminated rainwater is collected in a storm drain system and is passed through the treatment plant in the northeast portion of the site. Due to the past practice of storing treated wood products on the MCTC South Yard, some wood treating chemicals had been detected in the storm water runoff from the South Yard. The South Yard surface has been cleaned and residual contamination in pipes and ditches removed as part of the remedial actions undertaken by the Discharger. Runoff from the South Yard is not regulated.