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• Introduction This report presents the results of the additional site investigation required by the County of San Joaquin County Public Health Services Environmental Health Division (PHS-EHD) for the site as discussed in the Wright work plan (modified) dated October 24, 1995 The site had underground storage tanks removed and soil and groundwater contamination revealed Initial site studies by other consultants and groundwater monitoring reports have been completed for this site (see References) The work presented herein builds upon this work, which was reviewed and approved by PHS-EHD representatives Together with the previous site studies, Wright feels work presented herein forms the Problem Assessment Report Field Activities and Methods - Exploratory Soil Borings Nine exploratory borings were drilled at the locations shown on Figure 1 Drilling and well installation permits were secured from the PHS-EHD prior to doing the field work Boreholes were drilled with truck mounted GeoProbe (tm) drilling equipment Ail drilling equipment and sampling tools were cleaned prior to arriving, and before leaving the site The push tools were advanced to the desired sampling depth interval, and a continuous acetate liner was driven The sampler was then retrieved and dissembled, and the soil samples retained for chemical analysis were cut from the soil filled acetate liner, sealed with Teflon® paper and plastic endcaps, labeled, logged onto chain-of-custody forms and placed in a chilled ice chest The boreholes were lithologically logged using the Unified Soil Classification System under the . supervision of a registered geologist Additional Iithologic information was collected to describe the subsurface geology The samples were continuously collected at intervals of obvious contamination and at stratigraphic features of interest Depth of static groundwater levels in boreholes was measured to the nearest one-one hundredth of one foot at the existing grade Upon completion of the borehole drilling and collection of information, the boreholes were backfilled with grout, placed from the bottom to top of the borehole under approval of the PHS-EHD Groundwater Sampling Each exploratory boring was sampled The ground water samples collected from the boreholes were used for a rapid reconnaissance of site groundwater contamination The boreholes were sampled using the Wright Sampling Protocol, a brief summary of which follows Each borehole was advanced about 4-feet into the aquifer The water entering the borehole was sampled using a clean bailer, and carefully poured into the appropriate laboratory prepared container with minimum cavitation Depth to groundwater measurements were made to the nearest one-one hundredth of one foot, and also checked for the presence of separate phase product. Each water sample was labeled, logged onto a chain-of-custody form, and placed in a chilled ace chest Upon completion of the borehole sampling, the borehole was sealed as noted above Mr Ed's Muffler Project No 4090-P Page 3