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to provide a consistent approach to site evaluation and site management and/or closure GEOMATRIX decisions per the Low Risk Criteria outlined in the RWQCB "Appendix B of Tri-Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites"(RWQCB, revised 1996). The investigation included advancing eight soil borings (GB-1 through GB-8)and the collection and analyses of soil samples; grab groundwater ' samples were also collected from certain borings (Figure 2). Results of the investigation indicated that(1)petroleum hydrocarbons are present in the site subsurface, (2) the lateral and vertical extent of petroleum hydrocarbon-affected soil is constrained, and(3)residual ' petroleum found in soil should not pose an unacceptable health risk to future on-site residents. These results and conclusions were reported by Geomatrix on behalf of CPL in a"Site Status Report"dated August 1998 (Geomatrix, 1998). Soil analytical results are presented in Table A-1. tGrab groundwater data collected during the July 1998 investigation suggested that the residual petroleum present in the soil is not providing a significant source of dissolved petroleum constituents to groundwater. Groundwater samples collected from one location in the assumed downgradient direction from affected soil (GB-5) did not contain dissolved petroleum at concentrations above water quality objectives (WQOs) established by the RWQCB as part of the Technical Approach. Groundwater samples collected from another location(GB-4) in the assumed downgradient direction,based on groundwater gradient established during previous ' investigations at the adjacent Dividend Property, did not contain dissolved petroleum at concentrations above WQOs,with the exception of one sample(duplicate and unfiltered)that contained total petroleum hydrocarbons (TPH)quantified as diesel (TPHd) at 140 micrograms per liter(µg/1). TPH quantified as gasoline(TPHg) at 720 µg/1, TPHd at 520 µg/1,toluene at 0.7 µg/1, ethylbenzene at 1.6 µg/1, xylenes at 5.4 µg/1, acenaphthene at 1.3 µg/l, fluorene at 3.4 µg/l, pyrene at 0.3 µg/1, and chrysene at 0.2 µg/1 were detected in the grab groundwater sample ' collected from GB-1,which was installed directly within petroleum-affected soil. The TPH results are the only results above WQOs from GB-1. Grab groundwater analytical results are ' presented on Table A-2. ' \\sf3\deprdara\Doc_Safe\4780.01\c1srrpt.dm 2