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•AL1 INC <br /> The additional site characterization activities (WZI, 1993) which are summarized in Exhibits <br /> 3 through 8, consisted of: 1) inclined soil boring AB-3 (included in this report in Appendix <br /> III) and two vertical soil borings (T-4, T-6 in Appendix III) adjacent to the concrete tank <br /> that were advanced to a total depth of 47 feet below ground surface (Exhibit 5); 2) three <br /> shallow soil borings (D-6, D-7, D-8 in Appendix III) to a maximum depth of 16.5 feet below <br /> ground surface at Area"D"where previous data indicated that trace to minor hydrocarbon <br /> and chlorinated hydrocarbon compounds impacted the shallow subsurface from surface <br /> spillage; and 3) exploratory excavation of three shallow trenches to a depth of 7 feet to <br /> investigate shallow hydrocarbon soil impact from surface spillage at Area "A". <br /> 11. PROPOSED REVISED REMEDIAL ACTION PLAN <br /> The proposed Revised Remedial Action Plan only addresses the diesel, gasoline, and oil <br /> and grease hydrocarbon soil contamination. Because of the relative immobility of the <br /> heavy fraction hydrocarbons and distance of over 35 feet between identified base of soil <br /> contamination and estimated depth to ground water at 55 feet, no ground water <br /> investigation for hydrocarbon compound impact on local ground water is believed <br /> warranted. Chlorinated hydrocarbon contamination will only be addressed as it impacts <br /> the aeration and waste disposal permitting of the diesel and oil and grease contamination. <br /> The potential impact to local ground water due to chlorinated hydrocarbons is not part <br /> of this proposed Remedial Action Plan. It will be addressed separately, most likely, under <br /> the oversight of the California Environmental Protection Agency, Department of Toxic <br /> Substance Control. <br /> The average concentrations of heavy fraction hydrocarbon compound impacted soil is <br /> estimated at 500 to 2,500 parts per million. The heavy fraction hydrocarbon impacted <br /> soil consists primarily of diesel fuel and/or oil and grease. Volatile hydrocarbon <br /> concentrations (TPH-G) of impacted soil are estimated to average 100 ppm based on <br /> subsurface sampling (WZI, 1993; TMG, 1992) and are estimated to affect approximately <br /> 450 cubic yards of soil. <br /> Page 2 <br />