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WASTE DISCHARGE REQUIRE ORDER NO.R5-2003-XXXX <br /> SPXCORPORATION,MARLEY COOLING TOWER COMPANY 2 <br /> IN SITU GROUNDWTER REMEDIATION PILOT STUDY,SAN JAOQUIN COUNTY <br /> TENTATIVE <br /> 6. The soil and groundwater remediation activities to date at the site have included (a) excavation and <br /> off-site disposal of soils containing arsenic exceeding the recommended action levels from ditches <br /> and commercial and residential properties, (b) replacement of the synthetic liner in the bottom of <br /> the retort pit with an upgraded liner, (c) installation and operation of a retort fluid capture system <br /> and a leak detection system, (d) installation and operation of a 500 gallon per minute groundwater <br /> extraction and treatment system since 1992 (interim system started in 1987), and (e) installation <br /> and operation of a soil flushing system since 1997. <br /> 7. Groundwater is currently extracted from 14 extraction wells on and off-site. The groundwater <br /> extraction system operates with an extensive network pumping at rates varying from 10-90 gallons <br /> per minute depending on effective capture of the groundwater contamination plume. The <br /> groundwater treatment system consists of a treatment plant with an electrochemical unit operating <br /> in parallel to an ion exchange unit that removes waste constituents from the extracted water. <br /> Treated water upto 0.94 million gallons per day(mgd) is discharged to the Stockton Diverting <br /> Canal, a tributary to the Calaveras River, under an National Pollution Discharge Elimination <br /> System(NPDES)Permit No. CA0081787, Waste Discharge Requirements (WDR)No. R5-2003- <br /> 0030, and Groundwater Monitoring and Reporting Program (MRP)No. R5-2003-0030. <br /> 8. Groundwater monitoring results from January 2002 show that the total chromium concentrations <br /> are highest in well MW-105 at a concentration of 18,900 micrograms/liter(µg/1). The <br /> groundwater cleanup level for total chromium for the MCTC site is in the "Final Remedial Action <br /> Plan Approval Record"dated June 1990, and is the current or any update of the current MCL. The <br /> current MCL for total chromium is 50 µg/1. <br /> Pilot Study Layout and Operation <br /> 9. The Discharger proposes to inject a chemical reducing agent (calcium polysulfide) and an organic <br /> carbon source (ethanol)into shallow groundwater to reduce hexavalent chromium to trivalent <br /> chromium, thereby precipitating and immobilizing chromium. The ethanol will serve as a carbon <br /> source to stimulate microbial growth, and maintain reducing conditions. The pilot study will be <br /> conducted in two phases, Phase 1 and Phase 2. <br /> 10. The background groundwater quality(key parameters) for the site, as obtained from March 2003 <br /> upgradient monitoring well sampling, is summarized as follows: <br /> Constituent Units Concentration Water Reference <br /> Range Quality Limit <br /> Chromium (total) µg/1 3 to 9 50 California Primary Maximum <br /> Contaminant Level (MCL) <br /> Arsenic 1 2 to 5 10 USEPA Primary MCL <br /> Copper µg/1 2 to 4 170 California Public Health Goal in <br /> Drinking Water—Office of <br /> Environmental Health and <br />