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1 ' Sutter Office Center Project 2267-E Februaiy 18, 2002 Page 5 ' A summary of the analytical data is shown on Plate 5, and the cei trfred analytical reports and chain-of-custody records are presented in Appendices C and D FINDINGS AND RECOMMENDATIONS Plate 6 shows the extent of residual hydrocarbons in the soil and groundwater at the captioned site The groundwater obtained by the probes Shows a much hrghel level of residual hydrocarbons than that which is actually present because the residual hydro- carbons that are retained in the soil pores are released by the sampling process For example, Piobe A indicated that the level of TPH-G in the shallow groundwater was 470 . ppm, however, the actual level of TPH-G in the groundwater in Monitoring Well MW-1, adjacent to this probe, as 17 to 18 ppm Consequently, the data from the probes should only be viewed as a guide to the extent of the residual hydrocarbon impact on the groundwater Petroleum hydroca;bons were not found in Probe H, located approximately 100 feet northeast of the impacted area, indicating that the residual hydrocarbons aie generally confined on-site by the clayey soil They have not migrated any significant distance down Igradient from this site There are also no known active water wells within 2,000 feet of this site IWe recommend that an additional gi oundwater monitoring well be installed in the area where the probes indicate that residual hydrocarbons are present at the greatest depth, to determine the actual Ievel of residual hydrocarbons in the groundwater at 80 and 100 feet below the ground surface This mfoimatron will in determining possible maigation measures CLOSURE We have enjoyed working with you on this project If you have any questions, please do . not hesitate to call our office The following plates and appendices are attached and Icomplete this aepoxt Z__4 HYDRO GEO CONSULTANTS,INC