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■tom.' INC The additional site characterization activities (WZI, 1993) which are summarized in Exhibits • 3 through 8, consisted of 1) inclined soil boring AB-3 (included in this report in Appendix 111) and two vertical soil borings (T-4, T-6 in Appendix III) adjacent to the concrete tank that were advanced to a total depth of 47 feet below ground surface (Exhibit 5), 2) three shallow soil borings (D-6, D-7, D-8 in Appendix III) to a maximum depth of 16 5 feet below ground surface at Area"D"where previous data indicated that trace to minor hydrocarbon and chlorinated hydrocarbon compounds impacted the shallow subsurface from surface spillage, and 3) exploratory excavation of three shallow trenches to a depth of 7 feet to investigate shallow hydrocarbon soil impact from surface spillage at Area "A" ll PROPOSED REVISED REMEDIAL ACTION PLAN The proposed Revised Remedial Action Plan only addresses the diesel, gasoline, and oil and grease hydrocarbon sod contamination Because of the relative immobility of the heavy fraction hydrocarbons and distance of over 35 feet between identified base of soil contamination and estimated depth to ground water at 55 feet, no ground water investigation for hydrocarbon compound impact on local ground water is believed warranted Chlorinated hydrocarbon contamination will only be addressed as it impacts the aeration and waste disposal permitting of the diesel and oil and grease contamination The potential impact to local ground water due to chlorinated hydrocarbons is not part of this proposed Remedial Action Plan It will be addressed separately, most likely, under the oversight of the California Environmental Protection Agency, Department of Toxic Substance Control The average concentrations of heavy fraction hydrocarbon compound impacted soil is estimated at 500 to 2,500 parts per million The heavy fraction hydrocarbon impacted soil consists primarily of diesel fuel and/or oil and grease Volatile hydrocarbon concentrations (TPH-G) of impacted sod are estimated to average 100 ppm based on subsurface sampling (WZI, 1993, TMG, 1992) and are estimated to affect approximately 450 cubic yards of soil 40 Page 2