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11/20/2003 16:25 ATC ASSOCIATES -> 12094683433 NO.197 IP13 I I I I ADDITIONAL GROUNDWATER INVESTIGATION i OUIK. STOP No. 132 3555 WEST HAMMER LANE STOCKTON, CALIFORNIA 1.0 ]EXECUTIVE SUMMARY On behalf of Quik Stop Markets, Inc, (Quilt Stop), ATC Associates Inc, (ATC) has completed an additional groundwater investigation for the Quik Stop site located at 3555 'West Harmner Lane, Stockton, California (Figure 1). The purpose of this investigation was to further assess the vertical and lateral downgradient extent of petroleum hydrocarbons in soil and groundwater at the site and adjacent area. The results of the investigation are presented in this report. i To further assess groundwater conditions beneath the site, ATC completed three soil borings on July 09, 2000. The soil borings were advanced using a Geoprobe T"' sampling rig. Soil and groundwater sannples were obtained at each location. Groundwater samples were collected from � the local upper and lower aquifers. The soil and groundwater samples were analyzed for the following: total petroleum hydrocarbons as gasoline (TPH-G), benzene, toluene, ethylbenzene, xylenes (BTEC, and fuel oxygenates including tert-butanol, methyl tert-butyl ether (MTBE), di- isopropyl ether(DIPE), ethyl-tert-butyl ether(BTBE) and tert-amyl methyl ether(TAME). Groundwater was encountered at depths of 10 to 17 feet below ground surface (bgs) in the upper aquifer and at depths of 24 to 29 feet bgs in the lower aquifer. TPPI G was detected in groundwater samples obtained from SB-1 at 10 and 24 feet, from SB-2 at 17 and 29 feet and from SB-3 at 25 feet bgs. MTBE was also detected in the groundwater samples obtained from SB-1 at depths 10 and 24 feet bgs, from S13-2 at depths 17 and 29 feet bgs and from SB-3 at 25 feet bgs. MTBE was below laboratory detection limit in the groundwater sample collected from soil boring SB-3 at l t feet bgs. BTEX and other fuel oxygenates, excluding MTBE, were not present in groundwater samples obtained from SB-1, S13-2 and SB-3. Based on the results of this investigation, it appears that TPH-G and MTBE have migrated a short distance generally down gradient on site, in the vicinity of boring SBA, and off site at low concentrations, in the vicinity of soil borings SB-2 and SB-3. The maximum T'PH-G and MTBE 1:5AojacloVQl]f]CS19F MK4'S(61Sn3,)IQS 1321Rafm120001AAdDn16B08.0oc ATC Associates Inc.