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t 1.0 INTRODUCTION Upgradient Environmental Consultants was retained by Hotchkiss Mortuary in June, 1997 to assess the lateral and vertical extent of contaminated soil and groundwater beneath the mortuary property in Tracy, California. The invesitgation was performed at the request of the San Joaquin County Public Health Service, Environmental Health Division (PHS/EHD), the lead agency for the project. That request stemmed from the detection in 1990 of gasoline in a soil sample collected from beneath a 525-gallon underground storage tank (UST) when it was taken out of service and removed by Crisp Tank Testing. The mortuary had used the UST to store gasoline for company vehicles. The removal was witnessed by personnel from PHS/EHD and the Tracy Rural Fire Department. FGL Environmental Laboratories detected total petroleum hydrocarbons as gasoline (TPH-g) at a concentration of 300 .mg/kg and BTEX compounds at up to 3 mg/kg. On June 24, 1997, Upgradient Environmental submitted .a work plan to drill up to four borings around the former tank cavity and collect soil samples at 5-foot depth intervals until reaching the groundwater table. The work plan also called for collecting a water sample from each boring. In written communication received July 16, EHD amended the work plan to specify that all borings would be drilled to a minimum depth of 10 feet to insure that samples were collected be the depth of the 1990 tank sample. 2.0 SITE LOCATION Hotchkiss Mortuary is located at the intersection of Holly Drive and Highland Avenue in central Tracy (Figure 1). The area is topographically flat, and is zoned primarily for residential use. In addition to the mortuary,there are a few other commercial establishments in the area. 3.0 DRILLING AND SAMPLING Drilling took place on July 17, 1997. Boring B-1 was drilled in the approximate center of the former UST excavation, 6 feet south of the garage building in the rear portion of the property (Figure 2). Upgradient used a portable Beaver post-hole digger equipped with 3- inch-diameter hollow-stem augers. The boring was drilled to a total depth of 12 feet, and with the approval of Mrs. Margaret Lagorio of EHD„ soil samples were collected at 9 feet and 12 feet. Groundwater was reached at 9.7 feet, and a sample was collected at that depth. The soil samples were collected through the augers by driving a 1-inch-diameter steel sample tube lined with a 2-foot-long clear plastic sample sleeve into the native soil. After the 9-foot sample was extruded from the sample tube, a Microtip model 2020 photo- ionization detector was used to screen the sample for hydrocarbon vapors, the ends of the sample sleeve were cut off to eliminate head space, a small amount of the soil was preserved for examination, and the sleeve was sealed with plastic end caps and labelled. It