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t <br /> Ike <br /> 355 Enterprise Place <br /> Page 2 of 2 <br /> • The last groundwater monitoring event took place on August 8, 2003; during this <br /> and the previous sampling event on May 30, 2003, groundwater results in all five <br /> monitoring wells and the one extraction well were non-detect for all contaminants <br /> of concern; <br /> Based concern <br /> in; <br /> calculations presented by AGE, the volume of petroleum <br /> hydrocarbon-impacted soil is approximately 2,885 cubic yards, yielding <br /> approximately 1,280 gallons of diesel, which is equivalent to 9,143 pounds of <br /> diesel. <br /> Based on these findings, interpretations, and conclusions, AGE recommends <br /> consideration of case closure neo this ommentsfon theseswith f ndingseanddine interpretations s <br /> in <br /> the eight.bulleted items above <br /> follows: <br /> • Groundwater gradient is toward the north, however, the highest soil <br /> contamination was encountered in borings P-4 and MW-5 located southwest of <br /> the former UST; EHD is concerned that there may be more than one source area. <br /> • EHD does not believe that the vertical extent of impacted soil has been <br /> demonstrated south of the former UST, nor has soil contamination been <br /> delineated laterally to the southwest, south, and east of the former UST site; also <br /> the lateral extent of groundwater contamination has not been delineated east of the <br /> former UST. <br /> AGE has shown a general decline in dissolved contamination concentrations,but has also <br /> demonstrated that there are still high concentrations of diesel on site. Therefore, EHD <br /> can not support a recommendation for site closure at this time. Please submit a work plan <br /> that will delineate soil contamination to the southwest, east, and south of the UST site; <br /> delineate groundwater east of this site; and provide a fate and transport model of <br /> petroleum hydrocarbons released at the site. The transport of petroleum hydrocarbons, <br /> potential relevant exposure pathways, and potential receptors should be specific for this <br /> site. Please submit this work plan and fate and transport model to EHD by August 3, <br /> 2004. Also, please initiate groundwater monitoring immediately since quarterly <br /> groundwater monitoring has not taken place since August 2003. <br /> If you have any questions, please contact Vicki McCartney by electronic mail at <br /> vmccartne s'cehd.com or by telephone at (209) 468-3456. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Vicki McCartney,REHS Nuel C.Henderson, Jr.,RG <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit N <br /> cc: Donna Sexton, AGE <br /> James L.L. Barton, CVRWQCB <br />