SITE INFORMATION AND CORRESPONDENCE

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Review for No Further Action - 2 - 15 ,Tune 1995 Major Mart, 1235 East Alpine Ave. I Stockton, Yolo County Low levels of soil contamination were also detected in borings near the tank pit. In the boring for MW-1, 30 ppb benzene was detected at a depth of 51 feet. In the$oring for MW-2, 6 ppb benzene was detected at a depth of 50.6 feet. In the boring for MW-3, up to 76 ppb benzene and 270 ppb xylene were detected at depths of 41 and 55.6 feet. In MW-5, .only 0.98 ppb benzene ( _ was detected at 30 feet. No BTEX or TPHg contamination was detected in soil samples from MW-4 and MW-6. In April 1994, Secor drilled SB-1 and SB-2 as confirmatory borings; in the underground tank investigation. In SB-1, through the tank pit, soil contamination was detected at depths of 46, 56, and 66 feet, with 17 ppb benzene in the 66 ft sample. 1,2-DCA was also detected in SB-1, at up to 46 ppb at a depth of 68 feet. No BTEX, TPHg, or DCA contamination was detected in soil samples from SB-2. it Secor drilled SB-3 and SB-4 to investigate possible contamination below the former septic leach area. Contamination was detected at a depth of 26 feet in SB-3. Kerosene range hydrocarbons were detected at 1500 ppm (DL was 25 ppm). Laboratory personnel indicated that it was not weathered gasoline. Also, naphthalene was detected at 4.4 ppm and methyl naphthalene was detected at 2.5 ppm BTEX constituents were analyzed by both EPA Method 8020 and 8240. BTEX was not detected with 8020, however, the detection limits were high. With method 8240, toluene was detected at 35 ppb, xylenes at 510 ppb, ethylbeiizene at 130 ppb, and benzene and l DCA were not detected. However, the detection limit was 25 ppb: TPHg was analyzed with EPA. Method 418.1 and was not detected, however, the detection limit was very high. SB-3 was continued to 81.5 feet. A sample from 31 feet, had no detectable contamination, except for 12 ppb toluene. SB-4 was drilled 10 feet northeast of SB;-3 and also had no contamination in a soil sample from 26 feet, except for 13 ppb toluene. All detection limits were acceptable for the samples from SB-3 at 31 feet and SB-4 at 26 feet. According to Secor, because naphthalene and methyl nap hth leve ewere found below the septic leach field, the source of the naphthalene and methyl naphthalene.[may have been toilet deodorizers. It appears that the naphthalene and methyl naphthalene contamination is limited to approximately 26 feet in depth and does not extend more tl n 101feet laterally from SB-3. GROUND WATER CONDITIONS ! . Depth to ground water has varied from approximately 84 feet bgs lin October 1992 to approximately 67 feet bgs in March 1994. In early 1994, the ground water level was higher than the top of the screened intervals in the wells. In October 1994, Secor attempted to lower the water table in an effort to collect representative ground water samples and detect the presence of free product. However, the procedure was not completely successful; the water bearing zone produced water faster than it could be removed. With the procedure Secor used, only in MW-2 was the ground water lowered below the top of the well screen. _ The direction of ground water flow has varied between the west, southwest, south, southeast, east, and northeast, although the predominant direction of flow has been southeast. Secor has t speculated that one of the values used to determine the sole'�weste'rly gradient may have been in i� �j