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Stockton Meat Plant - Case Closure Page 6 <br /> March, 1996 <br /> lie example The Hydropunch II sample was reported with 1,200 ug/l as TPH-d <br /> This location is approximately 200 feet west of the tank site The location of <br /> this sample is upgradient of the tank site Krazen comments on Page 14 of <br /> their report <br />' "The observed distribution of TPH-D suggests that there may be <br /> a background concentration of diesel in groundwater in the <br /> range of 300 to 400 ug/l, not associated with the former Safeway <br /> USTs Another source for this "background" diesel may also be <br /> from former military operations which occupied the site <br /> However, no point sources attributable to the military <br /> operations were identified during this investigation <br /> The distribution of TPH-D in groundwater both west and <br /> northeast of the former Safeway USTs suggests that either, 1) <br /> groundwater flow direction has historically varied by over 180 <br /> degrees, 2) there is an off-site source for the diesel noted in <br /> ' sample KHP-9, west of the former tanks, or 3) an as yet <br /> unidentified military-related point source is present" <br /> Risk Assessment (1996 <br /> On August 18, 1994, Safeway request site closure The request was made <br /> concurrent with submittal of the third quarter, 1994, groundwater monitoring <br /> results On October 17, 1994, in a letter to Safeway (Attachment H), the San <br /> Joaquin County PHS stated that the County would accept a risk assessment in <br /> support of site closure A specific requirement was attached to the letter that <br /> the risk assessment " shall include data to support an estimation of the <br /> lateral extent of the existing plume The current data suggests that the <br /> existing monitoring wells are within the plume The lateral and vertical <br /> extent of the plume must be determined so that a more accurate estimation of <br /> ' the remaining mass of contamination can be calculated " <br /> In February, 1996, ChemRisk, a Division of McLaren/Hart completed and <br /> reported on a risk assessment for the site Their report, Tier II Risk Based <br /> Corrective Action for Former Safeway Meat Packing Facility , date February 26, <br /> 1996 , is included in Attachment H As requested in the PHS October, 1994 <br /> ' letter to Safeway, ChemRisk used both the lateral and vertical soil and water <br /> data from all the previous reports including data from Western Geologic <br /> Resources, 1rRM-West, and Krazen <br /> The results of the risk analysis indicated that the residual levels of volatile <br /> and semi-volatile organic chemicals in the soil and groundwater associated <br /> with the underground tanks are below levels which pose unacceptable risks <br /> Given diesel concentrations at detectable concentrations, albeit trace levels, <br /> 1 <br /> 1 <br />