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5.4 Confirmation sam les/anal tical data 5.4.1 Table 4 Soil Testinq Resultsi.Plant K Closure Anai 1jte In m Ik Sa_male Date Description Gasollne 11 pqnzene -o uene Ethyl Benzene Xylene HAR1 @ 18 10124/96 36'hole Northwest corner @ 18' <10 il <0.002 <0.002 <0.002 <0.006 HAR1 @28 10124156 36"hole Northwest corner.bottom <10 <0.002 <0.002 <0.002 50.006 RHEWR2@16 10128/95 6 hole East end East side-wall @ 16 84 <0.002 50.002 40.002 -0.006 RHSWR2@16 10/25/95 6 hole East end South side-wall @ 16 470 <0.004 <0.004 <0.004 <0.012 RHNWR2@16 10125!95 6 hole East end North side-wall @ 16 2300 !{ <0.001 <0.001 0.190 <0.003 SASHR2@36 10125196 6 hole East end bottom hole @36 <10 50.002 <0.002 <0.002 <0.006 RHNWR3@16 1026195 6 hole West end North side-wall @ 16 <1 <0.003 <0.003 <0.003 <0.003 RHSWR3@16 10126G5 6 hole West end South side-wall @ 16 41 <0.003 <0.003 <0.003 <0.003 EABHR3@36 10126/95 6 hole West end bottom hole @36 <1 -0.003 <0.00C3 <0.003 40003 EABHR4@37 10!27196 2'hole North between East and West bottom <1 <0.003 <0.003 <0.003 <0.003 EABHR5@37 10/27/56 2'hole South between East and West bottom <1 <0.003 <0.003 -0.003 <0.003 f 5.5 Estimated Residual Contamination 5.5.1 General Discussion Tri Valley Growers has removed as much potentially contaminated soil as is practical and safe. The proximity of the tank site to a building is a limiting factor without risking the foundation support of the structure. We believe we have removed all source sods and any residual contamination is likely the result of a small amount of vaporized product in the soils. Using a conservative calculation we estimate some 93 gallons of gasoline hydrocarbons with amounts of benzene, toluene, ethyl benzene, and xylene.lwere removed with the excavated soils. Conservative estimates of residual contamination show an estimated 10 gallons of gasoline hydrocarbon and no detectable levels of benzene, toluene, and xylene. A very small amount of ethyl benzene was detected in one sample. An estimate of the volume ethyl benzene is approximately .0009 gallons. We wish to again stress that the residual product calculations are very conservative and we fully expect that these numbers overestimate product left in the sods. 5.5.2 Estimate with Existing Sample Data Drawing 1, "Representation of Soil Borings, Historical Excavation, And Areas Used For Estimation of Residual Contamination", shows the areas where historical excavation was performed, current soil borings (1 through 5) and areas r; Page 8