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WORK PLAN FOR SOIL AND GROUNDWATER ASSESSMENT <br /> ELECTRO DELTA <br /> 821 S. Wilson Way <br /> Stockton, California <br /> 1.0 INTRODUCTION <br /> This work plan has been prepared by Upgradient Environmental Consultants on behalf of the <br /> owners of the above-referenced property under contract#99004. The purpose of the work plan is to <br /> specify the equipment and procedures that will be used to investigate the vertical and lateral extent <br /> of gasoline hydrocarbons beneath the Electro Delta property located at 821 S. Wilson Way in <br /> Stockton (Figure 1). The investigation was requested by the San Joaquin County Public Health <br /> Services Agency, Environmental Health Division (PHS/EHD) after a preliminary assessment in <br /> November 1998 demonstrated that the soil in the former location of a 550-gallon underground <br /> storage tank is contaminated. Under the authority of the Central Valley Regional Water Quality <br /> Control Board, regulatory oversight for the investigation has been assigned to PHS/EH.D and the <br /> site has been placed in its Local Oversight Program. <br /> 2.0 BACKGROUND <br /> It is our understanding that a 550-gallon underground storage tank (UST) was removed on <br /> December 18, 1985 from the property. The property was owned and operated by Caterpillar Tractor <br /> as early as the 1930's, and it is possible that the UST was installed during Caterpillar's ownership. <br /> Apparently, the UST was used to store leaded gasoline, because a concentration of 407 mg/kg <br /> (parts per million: ppm) was detected in the soil sample from beneath the UST when it was <br /> removed (data supplied by PHS/EHD). The removal was performed by Kleinfelder & Associates <br /> and witnessed by personnel from PHS/EHD. <br /> In November 1998, one soil boring was drilled to a depth of 15 feet in the approximate location of <br /> the former UST. Hydrocarbon odors became evident when the boring reached a depth of 12 feet, <br /> and laboratory analysis of a soil sample collected at the bottom of the boring indicated that <br /> gasoline-range hydrocarbons were present at a concentration of 4,890 ppm. Toluene, ethylbenzene, <br /> and xylene were also detected. Lead was not detected above local background levels. The <br /> investigation has therefore refocused on the hydrocarbons rather than on metals. <br /> 3.0 SCOPE OF WORK <br /> We propose to drill five borings in the immediate vicinity of the former tank cavity to Essess the <br /> depth and lateral extent of gasoline in the soil (Figure 2). Because of the limited space ovithin the <br /> garage building,the two borings in the building will be drilled with a Geoprobe direct-push drilling <br /> rig. In order to avoid the added complexity and expense of drilling in the public sidewalk at this <br /> stage, a third Geoprobe boring will be angle-drilled beneath the sidewalk on the east side of the <br />