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apo .rvNr AssoCIA rEs �2 C 3 WKA No 1735 01 April 22, 1992 Q� Page 4 kY" Soil Disposal All excavated contaminated soils were immediately transported to Port Costa Materials, Port Costa, California, or Forward Landfill, Stockton, California, for remediation via a rotary-kiln incineration or a bioremediation process Two hundred twenty-seven truckloads (approximately 4,400 tons) of contaminated soil were removed from the site and remediated The soil was transported by a certified hazardous waste hauler, transportation manifests are included in Appendix E Ground Water Investigation One monitoring well (MW1) was constructed on site to a depth of 45 feet by our firm on September 18, 1991 at the location show on Plate 3 Depth to ground water was measured to be approximately feet below grade A southeasterly groundwater flow direction was estimated, based on review of San Joaquin County PHS files of neighboring sites under investigation Plate 10 shows an as-built drawing of the monitoring well Plate 11 contains a log of soil conditions encountered during monitoring well •; installation Monitoring well construction and sampling methods are described in Appendix D Laboratory analytical results of soil samples obtained during the monitoring well construction are presented in Table 7 Four ground water samples were obtained from the monitoring well over a period of three months Three of the samples, MW1, MW3 and MW4, revealed detectable concentrations of TPH-gasoline, all samples revealed detectable concentrations of one or more constituents of BTEX No detectable TPH- diesel contamination was reported in any of the water samples Laboratory results for the ground water samples are summarized in Table 8, complete laboratory results and chain-of--custody documentation are contained in Appendix C Summary Approximately 4,400 tons of TPH-gasoline and TPH-diesel contaminated soil were excavated from the subject property and transported to Port Costa Materials or Forward Landfill for remediation Small areas of shallow surface soil containing low levels of relatively immobile TPH as motor oil remain in the upper three feet of the northern and western walls of the excavation, the low levels of motor oil are believed to be the result of historic spraying of asphalt oils on the gravel yard prior to asphalting All other sampled areas of the excavation contained non-detectable or trace levels of petroleum hydrocarbon contamination .l DD WALLACE KUHL R,,+cd pnt 7 &A550QATE5 INC: