ARCHIVED REPORTS_XR0005362 - Laserfiche WebLink

Home Browse Search

i 1 2.0 BACKGROUND INFORMATION ' 2.1 Site Description The site is currently operated as an automotive repair center by Stockton Clutch and Brake, and ' is located in a predominantly commercial and residential area, on the northwest corner of Miner Avenue and Stanislaus Street in Stockton, California (Figure 2). ' 2.2 Investigations Previously Undertaken On July 29, 1987, two underground storage tanks (UST's), one 750-gallon waste oil and one 1000- gallon waste oil, were removed from the property by Walker Hydraulics of Pleasant Hill, California. One soil sample was collected at 12 ft below ground surface (bgs) beneath the smaller UST. The laboratory analytical results indicated total petroleum hydrocarbon (TPH) concentrations of 370 parts ' per million (ppm) and total xylenes at a concentration of 44 ppm. A second soil sample was collected at 14 ft below ground surface from the fill port end of the larger 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, three soil borings (SBI, SB2, and S133) were advanced to approximately 46 feet bgs and monitoring well MW 1 was installed to a depth of 62.5 feet bgs (see Figure 2). ' The soil samples collected from soil borings S131, SB2, and SB3 did not contain detectable concentrations of TPHg, benzene, toluene, ethylbenzene, total xylenes (BTEC, or Oil and Grease, except for the 25.5-ft sample from SB 1 (0.010-ppm total xylenes). The soil samples collected from ' MW 1 (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 MWI at the depths of 35.5 ft and 45.5 ft did not contain detectable concentrations of TPHg. Benzene was not ' datatroundzelvalleyvwlsummary.doc 2