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X - _ _ x 4 February 11, 1992 Quik Stop Markets,Inc. Page 2 Project No. 3-49132-32 r nation. Soil samples from one boring, r millioear th npetroleum hydrocarbon contami n northwest portion of the north pump island, (E-3) contained 464 parts Per (ppnt) TPHG. The groundwater sample fronea ruellas debll ntained 470 zew �talevels ls oft toluene, parts per billion(ppb)TPHG and 21 ppb ben ethyl benzene, and total xylenes. MW-1 was subsequently destroyed in October 3, 1991 due to concerns that it could connect two water bearing units which appear to represent separate shallow aquifers. On September 11, 12 and 13, 1990, Exceltech (RESNA) drilled five additional "- exploratory borings at the site and converted three las f am thef them to ge boringstir monitoring wells. The results of the analyses of the soil same ittle or no petroleum hydrocarbon contamination. Analyses of groundwater samples collected from monitoring wells wom nd 4r 2ld not were found stoany 1 ppb hydrocarbon related contaminants butsamples benzene and detectable levels of ethyl benzene and total xylenes (RESNA, September 1990). During the above investigations, a leak was discovered in the subsurface piping for the fueling system at the site. Excavations to remove the contaminated soils revealed that the contamination had affected the tank backfill and possibly the soil beneath the tank backfill. Upon issuance of the proper permits, the overhead canopy, pump islands STs) were removed in concrete surface, and three underground fuel sremoval,ge se ca atlon and soil sampling _ Following tank October and November 1980. Fol g were continued until laboratory analyses of soil samples indicated that petroleum hydrocarbon contaminated soil above the water table in the vicinity of the storage tank moved fom the station and excavation had been removed. All contaminated soil double walled 1berg ass USTs properly disposed of(Exceltech November 1990). ew were installed at the sited concrete surface and the remaining ere replaced andwas backfilled the putt ba klin The canopy, pumps, an operation in March 1991. On April 2, 1990, Exceltech (RESNA) replaced the destroyed groundwater monitoring wnas well, MW-1, with two monitoring wells, designated MW-1R and MW-5. aquifer designed to monitor the local aquifer and N4W-5 to monitor a pe q discovered during the installation of MW-1. Analyses of all subsurface and analytical data indicated the presence of two aquifers beneath the czAstern portion of site. It was found that the local aquifer had no detectable TPHG or ETEX and the perched aquifer contained TPHG and some BTEX components (RESNA,July 1991). Well Pumping and Sampling On October 15, 1991, RESNA personnel visited the site for the purpose of pumping 200 gallons of groundwater from monitoring well MW-5. This humping was agreed upon with the San Joaquin County Public Health Services (SJCPHS) as an interim