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Ms Lori Duncan <br /> Page 5 of 5 <br /> The vertical limit of previously existing soil contamination was somewhere between 10 and 17 <br /> feet below grade. This indicates that a clean soil buffer, 10 to 20 feet in thickness, was present <br /> between the contaminated soil and groundwater. Clean soil samples at consecutive depths of 17 <br /> and 20 feet suggest that the low-mobility contaminants did not migrate through this interval. <br /> All residual contaminated soil has now been removed. This corrective action has been successful <br /> in eliminating any threat to groundwater that the material may have posed. <br /> RECOMMENDATIONS <br /> Ground Zero recommends that this site be closed with no further action required. <br /> We wish PHS/EHD to reconsider the need for groundwater sampling. No evidence suggests that <br /> contamination may have migrated to groundwater. Soil contaminants consisted for the most part <br /> of low-mobility long chain hydrocarbons. No MTBE was detected in any sample and HVOCs <br /> were detected at very low concentrations only in samples in the tankpit at depths of S and 10 feet. <br /> The clean soil samples collected at 17 and 20 feet attests to the low mobility of the contaminants. <br /> Please contact Ground Zero at your earliest convenience if you have any questions or comments <br /> regarding this report. <br /> Respectfully, <br /> Groun ero Analysis Inc. <br /> ` ED .GF0 <br /> Sean Garvey, G' ��*'� <br /> St ologist �' <br /> GREGORY P. <br /> STAHI- <br /> ♦` <br /> No. 5023 'F <br /> Gregory P. Stahl, RG 5023 s <br /> CA Certified Hydrogeologist No. 264 lq�F OF CAUFa���' <br /> Attachments <br /> cc: Mr. Ed Niemann, North Stockton Auto Service <br /> Mr. Marty Hartzell, RWQCB <br /> Ms. Karen Collins, Environmental Closures <br /> Nsauto/reporls/excaysum.doc <br />