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RZA T—C APS <br /> Working to Restore Nature <br /> MW-3 and MW-4 collected before February 1993; these analyses were not performed on <br /> samples from the other wells These results are shown on Table 9. <br /> 6.0 SUMMARY <br /> RESNA's findings from investigations at the site are as follows <br /> o Sediments beneath the site consist primarily of silt to clayey silt with clay <br /> lenses from below surface grade (bsg) to approximately 33 feet bsg and silty <br /> sand and sand from 33 to 57 feet bsg <br /> o Groundwater was encountered during drilling at approximately 41 to 43 feet <br /> bsg Water-bearing sediments consist of silt with some clay, silty sand, and <br /> fine-grained sand. The depth to water has fluctuated from approximately 38 <br /> to 44 feet beneath the site from 1992 through 1993 Based on information <br /> provided from San Joaquin County Environmental Health Department(1986), <br /> the historic groundwater high is approximately 30 feet bsg The direction of <br /> groundwater flow has varied from northeast to southeast, and the groundwater <br /> igradient has vaned from 0 0009 to 0 01. <br /> o Low concentrations of residual gasoline hydrocarbons were detected in soil <br /> in the vadose zone from 0 to 26 feet bsg near the former tanks, adjacent to <br /> the dispenser islands,and near the northwest, northeast, and southeast corners <br /> of the site Concentrations of TPHg ranged from 1 1 ppm to 1,700 ppm The <br /> highest concentrations were detected in soil within the capillary fringe from <br /> 26 to 41 feet bsg and near the margins of the site Residual hydrocarbons <br /> were detected in soil samples collected above the capillary fringe in the offsite <br /> soil borings <br /> o Residual gasoline hydrocarbons were detected in soil near the product line <br /> due to a release of approximately 2 to 5 gallons of gasoline during drilling <br /> operations. <br /> o Floating product has not been observed at the site <br /> o Dissolved gasoline hydrocarbons, 1,2-dichloroethane,and 1,2-dichloropropane <br /> have been detected to samples from the five onsite wells and two offsite wells <br /> Concentrations of TPHg have ranged from 12,000 ppb to 110,000 ppb, and <br /> concentrations of benzene have ranged from 2,100 ppb to 16,000 ppb The <br /> 3ioo¢io 10 <br />