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' 30 August 2004 AGE-NC Project No 99-0592 ' Page 12 of 13 ' The nearest surface water feature to the site is the Stockton Diverting Canal, located approximately 2,300 feet south-southwest of the site 1t is unlikely that water in the Stockton Diverting Canal is contaminated by impacted ground water from the site based on its distance and direction (up- gradient) from the site ' 7.0. SUMMARY/CONCLUSIONS The following conclusions were drawn from the results of this investigation ' Silt and clay were generally encountered to a depth of 57 feet bsg, with significant sand encountered at approximately 60 feet and 83 feet bsg Silt and sandy silt were encountered ' between the two main sand units Soil below 85 feet bsg consisted of clayey silt and other fine-grained soils Ground water was encountered at 64 feet bsg in the CPT soundings ' Pore pressure dissipation tests suggest that hydraulic conductivities were typical for sand where grab ground water samples were collected ' No analytes of concern were detected above laboratory reporting limits in any of the grab ground water or soil samples collected • The vertical limits of the dissolved plume have been defined on-site and do not extend ' greater than 70 feet bsg Laterally, hydrocarbon-impacted soil is defined to the west by soil boring B-2, to the northwest by B-3, to the south by boring MW�, and the northeast by bonn B-4 ��, �� 3 41-11, 1 Oq ' Dissolved hydrocarbon contamination detected in well MW-1 is likely the result of soil contamination present within the upper portions of the screened interval Some perched water ' may be present around 45 feet bsg, in the lens of silty sand/sandy silt (see MW-1 in cross- section A-A',Figure 4)-Contamination in MW-1 maybe due to seepage from perched water Water from the ground water table is likely not contaminated No contaminants of concern ' were detected in ground water samples collected from CPT-1 near MW-1 • Volumetric calculations indicate TPH-g in soil to be approximately 279 8 gallons,equivalent ' to 1,749 pounds • Release/s of petroleum hydrocarbons occurred from the on-site USTs Once released to the subsurface, the contaminants migrated into the upper clayey soil to a vertical depth of ' approximately 40 feet bsg The detected concentrations in ground water samples collected from the former UST location (e g , MW-1) have remained stable since ground water monitoring began in November 1999,indicating that further migration of hydrocarbons from ' the source area is not occurring Furthermore, analytes of concern have not been detected above laboratory reporting limits in ground water samples collected from perimeter Advanced GeoEnWronmental,Inc