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Marley Cooling Technologies • • 22 July 2002 San Joaquin County Inspection Report On 28 November 1984 the Regional Board ratified a Settlement Agreement between the Department of Health Services (now Department of Toxic Substances Control (DTSC)), Marley Cooling, and the Regional Board. This Settlement Agreement required the Discharger to conduct a Remedial Investigation/Feasibility Study (RDFS)to define the extent of contamination, to develop a Remedial Action Plan (RAP), and to implement all measures necessary to remediate existing site contamination. Following discussions with Regional Board staff, DTSC formally adopted the RAP on 29 August 1990. The RAP included the conceptual design of the groundwater remediation project. The recommended groundwater remedial action in the RAP includes the extraction, treatment, and discharge of contaminated groundwater. To minimize dewatering of the local aquifer and to aid in flushing of contaminants, approximately 5% of the treated water is reinjected into shallow soils in the area of a closed retort pit. The injected water is then recaptured by the groundwater extraction system. From the facility,up to 0.94 mgd of treated groundwater is discharged to the Stockton Diverting Canal,which flows northwest to the Calaveras River. Discharge to the Stockton Diverting Canal is conducted pursuant Waste Discharge Requirements (WDR's) Order No. 93-221,NPDES No. CA0081787. This permit expired on 1 July 1998, and accordingly, Marley Cooling had timely filed a new Report of Waste Discharge (RWD) and Application for permit renewal on 29 December 1997. Groundwater Treatment Processes The groundwater treatment system at the plant includes an electrochemical reduction and precipitation unit operating in parallel to an ion exchange treatment system. 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 during 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. 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 California hazardous waste, and is collected in roll off bins for off-site disposal. 2 Approved: