ARCHIVED REPORTS XR0010494 - Laserfiche WebLink

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Mr. Harlin Knoll San Joaquin County Public Health Services, Environmental Health Division Page 3 May 18, 1995 In August 1992 , three additional soil borings (HBH #4 through HBH #6) were drilled to a depth of approximately 40 feet bgs at the adjacent Hammertown property site in order to further delineate the lateral extent of soil contamination. Toluene was detected at a maximum concentration of 0. 034 ppm in the borings at depths ranging from approximately 20 to 40 feet bgs. Benzene, ethylbenzene, and xylenes were not detected in the borings. Groundwater was not encountered in the borings . i In January 1994 , one additional soil boring (TB-1) was drilled at the site, and one additional soil boring (TB-2) on the Hammertown property. The soil borings were drilled to first encountered groundwater. Groundwater was encountered at a depth of approximately 71 feet bgs and a hydropunch sampler was advanced to a depth of approximately 75 feet bgs. TPHg and BTEX were not detected in soil and groundwater samples collected from the borings. William J. Hunter & Associates prepared a report based on the results of the investigation and recommended that the sites be closed to further environmental work. In a letter dated May 24 , 1994 San Joaquin County Public Health Services-Environmental Health Division (SJCPHS-EHD) stated that based on the results of the investigation performed by Hunter & Associates, groundwater had not been impacted by the unauthorized release and that the lateral extent of soil contamination had been defined. However, SJCPHS-EHD did not concur with Hunter & Associates' recommendation to close the site to further environmental work, and requested two additional soil borings be drilled at both sites in order to further evaluate soil contaminant concentrations previously detected in the area of the former UST in sidewall sample SW-2W and in offsite soil boring B-5 . On January 23 , 1990, TPHg toluene, ethylbenzene, and total xylenes were detected at concentrations of 1, 600 ppm, 95. 4 ppm, 49 . 2 ppm, and 280 ppm, respectively in sample SW-2W. On October 5 1990 , benzene, toluene, and ethylbenzene were detected at concentrations of 0 . 068 ppm, 0. 037 ppm, 0. 011 ppm, respectively in soil samples collected from boring B-5 at a depth of approximately 25 feet bgs. SJCPHS- EHD stated that if soil samples from the two requested additional soil borings demonstrated significant reduction in gasoline concentrations since 1990, and if the mass/volume of gasoline remaining in the soil could be calculated, then SJCPHS-EHD would reconsider the request for case closure.