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MOO IN-1 f� Mr. R, W. Conlon October 9, 1990 202/150-0150 Page 18 4.3 GROUNDWATE,3 SAMPLING RESULTS Groundwater samples were last collected or,May 8, 1990 and sent to a State-certified laboratory for analysis. Laboratory results of these samp;es indicate that dissolved hydrocarbon constituents are Present in the ten monitoring wells at the site which do not contain separate-phase hydrocarbons. One monitoring well at the site contains :'hparate-phase hydrocarbons. Dissolved TPH-G concentrations ranged from 290 to 76,000 parts per billion (ppb). Dissolved benzene concentrations ranged from 2 to 22,000 ppb. The water sample collected from MW-5 on August 16, 1989, contained 74 ppb of 1,2- dichloroethane and 3 ppb of 1,2-dichloropropane. The laboratory results for groundwater analyses are summarized in Appendix V.and copies of the laboratory reports are presented in Appendix VI. Maps of dissolved TPH-G and benzene concentrations are presented In Figures 10 and 11. 5.0 CONCLUSIONS Soil conditions beneath the sive have been defined in all directions except to the north, across Charter Way. Assuming that the impacted soil does not extend farther than 20 feet north of the site,the volume of impacted soil would be approximately 3,000 cubic yards. The average concentration of petrofeum hydrocarbons within the soil is estimated to be 500 to 1,000 Fpm,resulting in an approximate total between 4,350 and 8,700 pounds of adsorbed hydrocarbons in the soil. The areal extent of groundwater conditions beneath the site have not yet been defined. All eleven monitoring wells contain detectable concentrations of hydrocarbons. Groundwater Technology would like to thank Texaco Refining and Marketing, Inc. for the opportunity to have been of service on this investigation. Please contact our West Sacramento Office if You have questions or comments. GROt1:�!}t1r1Tf H TECH,NoI.001;I.,VC.