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S k Ms. Dot Lofstrom _ Page 2 of 6 • surface from the fill ort end of the larger A second soil sample was collected at 14 ft below ground su a e p g UST. TPH was detected at a concentration of 360 ppm and total xylenes were detected at a concentration of 58 ppm. On September 1, 1987, additional soil samples were collected from the former UST pit. The samples were collected using a backhoe at approximately the same locations as the initial samples collected during the UST removal, but at depths of approximately 16.5 ft bgs. Analytical results for the sample collected beneath the smaller UST were not available. Results for the sample beneath the larger UST indicated TPH concentrations of 2,000 ppm and total xylenes at a concentration of 1,000 ppm. On September 25, 1987, twelve soil samples were collected from a stockpile of soil removed during the tank removal. Four of the samples contained detectable concentrations of TPH. Laboratory analytical results indicated that one sample contained concentrations of TPH as diesel at 13 ppm. The other three samples contained concentrations of total petroleum hydrocarbons as gasoline (TPHg) ranging from 170 ppm to 1900 ppm. The stockpiled soil had been segregated based on the sampling locations and laboratory results. In October 1987, Mr. Jay Friedman of Valley Volkswagen and Mr. Ray Walker of Walker Hydraulics backfilled the UST pit with the stockpiled soil. In May 1995, Ground Zero advanced soil borings SBI, SB2, and SB3 to approximately 46 feet bgs and installed monitoring well MW1 to a depth of 62.5 feet bgs (Figure 2). The soil samples collected from soil borings SB 1, SB2, and SB3 did not contain detectable concentrations of TPHg, benzene, toluene, ethylbenzene, total xylenes (BTEX), or Oil and Grease, except for the 25.5-ft sample from SBI (0.010-ppm total xylenes). The soil samples collected from MWI (located in the center of the former UST pit) contained TPHg concentrations of 8,000 ppm and 8,800 ppm in the 20.5 ft and 30.5 ft samples, respectively. Soil samples collected from MW I at the depths of 35.5 ft and 45.5 ft did not contain detectable concentrations of TPHg. Benzene was not detected in any of the soil samples. Oil and Grease was detected at concentrations of 230 ppm, 140 ppm, and 50 ppm in the 10.5 ft, 20.5 ft, and 30.5 ft samples, respectively. Low to moderate levels of TPHg and BTEX were reported in the initial groundwater sample collected from well MW1. Subsequent samples did not contain detectable TPHg or BTEX but did contain low levels of methyl tert-butyl ether MTBE. The MTBE may originate from the fuel leak at the adjacent property (601 E. Miner). In July and November 1999, Ground Zero advanced four additional borings downgradient of the UST's and collected soil and groundwater samples for analysis (Figure 2). Results were submitted to PHSIEHD and RWQCB in the report entitled Subsurface Investigation Summary Report and Request for Case Closure (December 20, 1999). Historical soil and groundwater analytical data are included in Attachment D. I i _