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SPX CORPORATION ORDER R5-2019-0018 SPX MARLEY COOLING TECHNOLOGIES GROUNDWATER CLEANUP NPDES NO. CA0081787 final RAP amendment that concluded that the pilot study successfully demonstrated the efficacy of in-situ Cr VI reduction and authorized the full-scale implementation of the in-situ treatment at the site. The WDRs for the protection of groundwater are being implemented under separate Order R5-2007-0126 issued by the Central Valley Water Board on 13 September 2007. A. Description of Wastewater and Biosolids Treatment and Controls The treatment system at the Facility consists of an electrochemical reduction and precipitation unit (ECS) operating in parallel to an ion exchange (IX) treatment system, the overall flow process can be seen in Attachment A (Figure A-1). The IX system consists of two anion exchange vessels and a cation exchange vessel. In the anion exchange vessels, chromium (VI) 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 would occur approximately every 2.5 days, 15,000 gallons of solution containing the stripped chemicals are removed from the IX system and processed through the electrochemical unit. A process flow diagram for the ion exchange system is shown in Attachment C (Figure C-3). As a result of in-situ remediation being conducted at the site, multiple extraction wells have met cleanup goals. Due to reduced flow rates from these idled wells, the IX system is not used any longer and is offline. The ECS unit consists of an electrochemical reduction (Andco) and precipitation process that uses iron as the reducing agent for the chromium (VI)followed by the addition of polymers 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. A process flow diagram for the electrochemical precipitation system is shown in Attachment C (Figure C-2). 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 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 South Yard, some wood treating chemicals had been detected in the storm water runoff. 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. Additionally, when sufficient storm water is accumulated on the North Yard to justify treatment, the operator will manually initiate storm water treatment through the Andco system. Groundwater from selected wells will simultaneously be delivered to the ion exchange treatment system. The groundwater treatment facility is designed to treat a maximum flow up to 0.94 mgd. Groundwater is extracted from approximately 13 operative extraction wells on and off-site. The groundwater extraction system can operate in a cyclical fashion with each of the two cycles lasting 56 hours or on a continuous basis with all extraction wells pumping at rates varying from 10 to 90 gallons per minute depending on effective capture of the groundwater contamination plume. When cycling, primary groundwater extraction is alternated between the north zone and the area south of the site. Water extracted from the north zone has higher contaminant concentrations. During south zone pumping, the capacity of the treatment plant ATTACHMENT F- FACT SHEET F-5