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Mr. Marshall Cloud • - 2 - • 9 January 2008 <br /> Defense Distribution Depot San Joaquin <br /> removed and placed in storage bins. After the excavation activities, soil samples were <br /> collected from the base and sidewalls of the excavation, and from the bins. The excavation <br /> samples were submitted to a California certified laboratory for chemical analyses of total and <br /> soluble lead and chromium. Work was performed in accordance with the approved <br /> DDJC— Sharpe, Remedial Action Work Plan, Site S-26, Area 6, prepared by URS and <br /> dated October 2006. <br /> The laboratory performed chemical analyses on seven sidewall samples and two bottom <br /> samples collected from the excavation. Also, analyses were performed on one field <br /> duplicate sample collected from a sidewall and one from the floor of the excavation. All total <br /> lead and total chromium concentrations were below the cleanup criteria established in the <br /> Final Record of Decision, Basewide Remedy for DDRW— Sharpe Site (ROD), <br /> February 1996. The ROD specifies cleanup criteria for Operable Unit 2 soils of <br /> 1,000 milligrams per kilogram (mg/kg) for total lead and 300 mg/kg for total chromium. The <br /> total lead cleanup criterion was subsequently reduced to 800 mg/kg at the Remedial Project <br /> Managers meeting held in November 2005. <br /> The ROD also specifies soil sample analyses be performed utilizing the de-ionized water <br /> waste extraction test (DI-WET) method to determine if lead and chromium concentrations <br /> have the potential to leach to groundwater and result in exceedances of cleanup standards. <br /> All nine of the soil samples were analyzed by the DI-WET method for concentrations of <br /> soluble lead and soluble chromium. One of the sidewall soil samples collected at <br /> approximately one foot below ground surface had a soluble lead concentration of 613 <br /> micrograms per liter (pg/Q. The remaining DI-WET analyses for lead and chromium were <br /> below the evaluation criteria of 150 pg/L and 50 pg/L, respectively. <br /> The ROD, Section 9.1.4 requires that DDJC perform an attenuation study for soluble lead or <br /> chromium concentrations exceeding the evaluation criteria. An attenuation study was <br /> accomplished by collecting a soil sample approximately one foot below the original sample <br /> that had a DI-WET lead concentration of 613 pg/L. The concentration of soluble lead in the <br /> attenuation sample was less than the detection limit, which is below the evaluation criterion <br /> of 150 pg/L. <br /> Based on the confirmation sampling results, DDJC recommended no further soil removal at <br /> Site-26, Area A because the concentrations of total lead and total chromium in all of the soil <br /> samples were below the cleanup criteria established in the ROD. In addition, the attenuation <br /> study conducted to address the one soluble lead concentration that exceeded the lead <br /> evaluation criteria concluded that leaching of lead would not result in an exceedance of the <br /> ROD maximum contaminant level for groundwater. <br /> REMEDIAL ACTION REPORT <br /> Following agency approval of the 12 February 2007 Technical Memorandum, DESJC <br /> surveyed the excavation backfilled the excavation, transported the contaminated soils to <br /> certified disposal facilities, and prepared the 30 October 2007 Report. The Report <br />