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S E C O R Conceptual Site Model . Chevron Service Station#9-6171 March 25, 2005 Page 23 extraction was planned Groundwater monitoring well MW10, which is located within the excavation pit, was converted to a vapor extraction well By using groundwater monitoring well MW10 as an SVE well, remediation will extend to the capillary fringe Groundwater monitoring well MW1 was connected to the vapor extraction system This will remove any free floating product that was not collected during the Initial skimming of the well In 1996, the thermal oxidizer system was removed and replaced by a carbon adsorption I system In December 1998, SVE operations were discontinued due to shrinkage of the petroleum plume Confirmation that the plume had shrunk was established by collecting soil samples at 50 feet bgs and analyzing them for petroleum hydrocarbons The depth of sampling was chosen because it is the depth at which the highest concentrations of hydrocarbons have historically been present Laboratory analytical results Indicate that the treatment system has removed approximately 728 8 lbs (> 99 86%) of benzene from the soil Laboratory analytical results Indicate that the treatment system has removed approximately 62,221 6 lbs (99 66%) of TPHg from the soil Groundwater monitoring results indicate an overall dissolved mass reduction of 292 lbs (97 86%) of TPHg and 143 49 lbs (99 99%) of benzene 6.5 Exxon Service Station #7-0136—6425 Pacific Avenue • Exxon service station #7-0136 operated from 1988-2000 Exxon leased the former Regal #603 site from Wickland Oil Company after Regal vacated the premises The site has been Iredeveloped and is currently operating as a Safeway Food & Drug gasoline fill station In 1998 three double-walled fiberglass 10,000-gallon capacity USTs were installed They were removed in November 2000 and replaced by two 20,000-gallon capacity USTs The old USTs were destroyed onsite and transported and disposed of as non-hazardous waste In November 2000, six soil samples were collected from beneath the UST pit using a hydraulic drilling rig Native soil samples could not be collected due to the presence of pea- gravel at depths up to 25 feet bgs Upon completion of soil sampling, the UST pit was backfilled with excavated material to within 4 feet of grade surface Laboratory analyses of the soil samples indicate that petroleum hydrocarbons, fuel oxygenates (DIPE, ETBE, TAME, and TBA), and lead scavengers (EDB and 1,2-DCA) were present at or above method detection limits 66 Former Unocal Service Station #5421 —7303 Pacific Avenue IThe former Unocal service station #5421, occupies the northwest corner of the Intersection of Pacific Avenue and Willora Road In 1989, the station was upgraded and the UST pit relocated from the northwest portion to the southeast portion of the property A total of 1,200 yd of contaminated soil was removed from the property and properly disposed of In • 1992, a septic tank and associated leach field were removed from the site A total of 1,350 IN\FiledProtects\ChevronlRetaiR#9-61711Site Conceptual ModeiNFINAL_CSM doc