FIELD DOCUMENTS AND WORK PLANS 2004-2014

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Appendix C:Initial Study Checklist Former Marley Cooling Tower Company,Stockton,CA 8.Continue the groundwater treatment system operation until remediation cleanup goals are achieved. The proposed work on the Franklin school site will be performed during periods when school will not be in session, Work will be scheduled when school is out of session and the athletic field has reduced usage. After . field activities are completed, surface completion will be restored to like original condition. The area of the proposed field activities will not interrupt the listed services. The project is expected to occur in the spring/summer 2007 and take approximately 12 months to complete. A notification to interested parties is expected to be sent out prior to the start of field work. BACKGROUND/HISTORY: In 1943, MCTC purchased the South Yard and began wood milling and cooling tower fabrication operations using pre-treated components purchased from vendors and shipped to the site. Wood preserving operations began in 1966 when the North Yard facilities were constructed. The facilities constructed included pressure vessels used for wood treatment(retorts), a retention pond constructed to impound and collect surface water run-off, a series of catch basins, and aboveground building structures.Wood products were treated with a copper/chromium/arsenic treating solution between 1966 and June 1982. In June 1982, the solution was replaced with an acid/copper/chromium solution. Wood treating operations continued until 1991. Chemicals used in these operations were released to the ground resulting in contamination of the soil and underlying groundwater. The Site has been the subject of investigation and remedial action since the mid 1980's to address this contamination. In June 1990, a Remedial Action Pian was approved and remedial actions were Implemented. Surface soils contaminated with arsenic, copper and/or chromium have been covered to prevent direct contact and the pipes/culverts/ditches area on or near the South Yard have been cleaned. An electrochemical precipitation system (high levels) and ion exchange system (low levels) are used to remove chromium from water extracted at approximately 450 gallons per minute from a series of 16 wells screened in the shallow (60-85'), 100-toot sand (90-110') intermediate (130-170'), and deep zones (180-220'), Treated groundwater is discharged to the Stockton Diverting Canal, north of the Site in accordance with National Pollutant Discharge Elimination System (NPDES) permit number CA0081787 and WDR permit number R5-2003-0100. Compliance monitoring of groundwater and reporting of effluent discharges to the Canal are on a scheduled frequency. Environmental restrictions are recorded with the County on the North and South Yard to protect the remedial systems and prevent certain uses. Enforceable Agreement HAS-A 01/02-140 is in place to continually operate and maintain the remedial systems with periodic reporting requirements. In 2003, an in-situ reductant solution of calcium polysuifide (3%) and ethanol (1-2%) in water was successfully tested through a phased pilot study approach under authorization granted by a 2003 RWQCB Waste Discharge Requirements permit. Monitoring data collected during the first pilot study indicated that a single point of injection could affect a reactive treatment zone with a radius of approximately 22 feet. This reactive treatment zone was shown to remain effective for the entire duration of the Phase I Pilot Study such that chromium impacted groundwater moving through the treated zone would also be reduced. Phase it involved the creation of a linear reactive barrier zone using injection points in a spaced grid approach. The calcium polysuifide solution generates reduced conditions resulting in dissolution of ferric hydroxide mineral coatings from aquifer grains. This dissolution in turn liberated arsenic in groundwater, previously present as a ferric arsenals co-precipitate in the ferric hydroxide coatings. The calcium polysuifide solution converts the ferric iron to ferrous iron,followed by the reaction of the ferrous iron with the hexavalent chromium which is removed from water when it forms the Insoluble chromium hydroxide. Arsenic concentrations liberated as a result of this process were shown to decrease over time. The ethanol was used as a substrate for indigenous microorganisms to control sulfate generation. HEALTH RISK DISCUSSION: A baseline risk assessment was performed as part of the remedial investigation in 1990 to address the potential human health and environmental impacts associated with the site in the absence of any further remedial action. Risks to human health and ecological resources were identified and several remedial measures were implemented over the last 16 years since the 1990 RAP. The primary chemicals of concern addressed in the 1990 RAP are arsenic and copper in shallow sail and chromium in deep soil and groundwater. The arsenic cleanup level used for soil was 30 mg/kg commercial, 14 mg/kg residential. Arsenic and copper which was not excavated and disposed off off-site has been encapsulated under a Resource Conservation and Recovery Act (RCRA) cap. Risks to potential ecological receptors have been addressed by the removal of impacted surface soil drainage ditches and piping and containment of Site run-off water. jChromium in groundwater is present at levels greater than 5,000 ug/L. The current groundwater remediation system continues to operate to remove this contaminant. Left unabated, chromium may reach the public water , _Aam:because roundwater represents a complete exposure pathway. The 1990 RAP estimates a health based ) Page 3 of 25.