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' Quik Stop Market No. 132 July 28, 1992 Project No. 3-49132-33 Page I t ' SOIL GAS AND SHALLOW GROUNDWATER SURVEY ' FOR QUIK STOP MARKET NO. 132 3555 WEST HAMMER LANE STOCKTON, CALIFORNIA Introduction ' RESNA Industries Inc., has completed a soil gas and shallow groundwater survey around the Taco Bell site adjacent to Quik Stop Market No. 132 located at 3555 West Hammer Lane, San Joaquin County, Stockton, California (Figure 1). Previous investigations have detected gasoline-related compounds in a perched aquifer near the eastern site boundary. The groundwater gradient in this area appears to have an easterly flow from the Quik Stop Market to the Taco Bell. Efforts to gain permission to enter the Taco Bell property or the property to the north were not successful. RESNA and Quik Stop therefore, with the approval of the San Joaquin County Public Health Services (SJCPHS), elected to conduct a shallow groundwater survey on the eastern side of the Taco Bell site and that portion of West Hammer Lane which fronts the Taco Bell site (Figure 2). 1 Techniques ' The sampling process was conducted from the back of a specially equipped van operated by Tracer Research Corporation of Tucson, Arizona. A 1-1/2-inch-diameter hole was drilled through the asphalt and a 314-inch-diameter hollow steel probe with a detachable ' metal drive point was inserted into this hole and pressed and pounded to the desired depth. The interior of the pipe was put under vacuum and withdrawn (the metal drive point remains) until loss of vacuum indicated that water or air was entering the open ' end of the probe. A length of polyethylene tubing attached to a vacuum pump was then lowered to the bottom of the probe and vacuum applied to see if any groundwater was present. If groundwater was recovered, it was placed into a 40 ml glass vial and sealed ' with a Teflon-lined septa cap. If groundwater was not encountered, the probe was put under vacuum and after two to five probe volumes of soil gas were evacuated, a soil gas sample was collected in a glass syringe. In locations where a soil gas sample was obtained, the gas within the glass syringe was injected into a Hewlett Packard 5890 Series II gas chromatograph equipped with a flame ionization detector and a computing integrator (gas chromatograph) for analysis. In locations where a groundwater sample was obtained, approximately half of the liquid in the glass vial was decanted, the vial recapped, shaken vigorously, and a sample of the