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and implemented. Initially, GeoAudit had proposed to remove free product weekly and then twice a month thereafter. However, since the presence free product has decreased in MW-4, GeoAudit has removed free product twice a month since October 10, 1994 (Table 2). ' TABLE 2 SUMMARY OF THICKNESS OF FREE PRODUCT ' Larry's Auto Repair - 308 North Grant Strret, Stockton, California (Feet) Date Monitonng Well Thickness ' September 23, 1994 MW-4 005 ' October 11, 1994 MW-4 0 02-0 03 October 24, 1994 MW-4 0 01-0 02 4.0 FINDINGS ' 4.1 Groundwater Elevation and Gradient ' The relative elevation of groundwater in each well was calculated by subtracting the groundwater depth from the surveyed casing elevation (Table 3) The average depth to groundwater at the site is 55 47 feet bgs This represents approximately a one-quarter foot drop in ground-water from February 1994 to September 1994 The groundwater gradient and flow direction in September 1994 was calculated to be 0 0019 ft/ft directed N 55° E (Figure 3) ' 4.2 Petroleum Hydrocarbon Impacted Groundwater iTPH as gasoline was detected in MW-1, MW-2 and MW-3 at concentrations of 6,300 Ag/L, 63,000µg/L and 11,000µg/L, respectively Benzene,toluene,ethlybenze and xylene were also detected in each well Analytical results of groundwater samples are summarized in Table ' 4 The laboratory results and chain of custody form is included in Appendix B ' 5.0 CONCLUSIONS & RECOMMENDATIONS 5.1 Petroleum Hydrocarbon Impacted Soil ' Petroleum hydrocarbon impacted soil remains at the site. The lateral extent of the impacted soil has not been defined The San Joaquin County PHS/EHD is requiring additional ' assessment to determine the extent of impacted soil As stated in GeoAudit's quarterly report dated April 14, 1994, GeoAudit recommends two slant borings to determine if impacted soil exists beneath the structure located on-site ' 0-1-3 of Auld Semom I— L • LArga Mb Pp.,,QP/a WAV S V 1 rl{ riot