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S E C O R <br /> L Ms. Anne Connor <br /> March 9, 2007 <br /> Page 5 <br /> was used in the backfill and compaction effort, and the surface elevation was finished to <br /> match that of the surrounding ground surface. <br /> It is SECOR's understanding that the soil bins will be removed by PTS and delivered to a <br /> waste management facility for disposal as non-hazardous soil. <br /> FINDINGS AND RECOMMENDATIONS <br /> Based on confirmation sample analytical results and SECOR's field observations, <br /> petroleum hydrocarbon-impacted soils remain beyond those removed during this remedial <br /> effort. The limited soil sample data set suggests that although chemical impact to soils may <br /> attenuate somewhat with depth, significant concentrations exist to a depth of at least 8 feet <br /> bgs. The hardpan layer observed discontinuously at approximately 3.5 feet bgs during the <br /> excavation work does not appear to have acted as a barrier to petroleum hydrocarbons <br /> migrating vertically from the surface. <br /> LObservations made in the field suggest that the chemical impact extends beyond the <br /> boundary of the excavation to the east and northeast, possibly below the adjacent <br /> pavement. The lack of volatile constituents in laboratory analytical data suggests a <br /> weathered fuel product, or possibly the presence of a heavier lubricating-type hydrocarbon. <br /> Although this scope of work was intended to completely remediate what was believed to be <br /> shallow, localized impact to soil from petroleum hydrocarbons, SECOR believes that <br /> additional characterization work is warranted to further delineate the lateral and vertical <br /> r extent of impacted soils. Such an investigation should include an evaluation of shallow <br /> Lgroundwater; although the on-site domestic well has been sampled and shown to be free of <br /> petroleum hydrocarbon-related constituents, this well is likely screened much deeper than <br /> the shallowest groundwater-bearing zone. SECOR also recommends performing a <br /> geophysical survey at the Site to evaluate the potential presence of underground storage <br /> r tanks (USTs) or related product delivery piping. <br /> Lis Sincerely, <br /> SECOR International Incorporated <br /> '-D C' 0 <br /> Neil Doran ruce E. Scarbrou , P. ® SMll <br /> Associate Geologist Managing Principal �•x,91 �d <br /> 10/0 <br /> cc: '/Mr. Mike Infurna, San Joaquin County Environmental Health <br /> L F <br /> I:\PG&E\French Camp\2007 Investigation\report\Excavation Report_Final.doc March 9,2007 <br /> rProject No.050T.50351.00.0003 <br />