SITE INFORMATION AND CORRESPONDENCE

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Mr. Ralph Moran • - 2 - • 11 August 2003 proposes to stop injection and begin routine monitoring to confirm the exceedance and to collect enough data to determine a trend in the concentrations. If concentrations remain above the baseline concentrations, ARCO will install a groundwater extraction and treatment system. ARCO will extract groundwater from one to three extraction wells, treat it, and then discharge it to the sanitary sewer or haul it off-site for disposal. After one year, ARCO will submit a pilot study report. If the results of the injection are favorable, ARCO plans to propose a full-scale injection plan that will cover up to 75 percent of the site by using two injection galleries. ARCO will determine the injection rates and concentrations of the sulfate/nitrate/nitrogen/phosphorous solution based upon the results of the pilot study. Since the Revised Report proposes a pilot study of the nitrate and sulfate injection, it is not considered a cleanup plan. A comprehensive cleanup plan will be required once the pilot study results are available. Regional Board staff concurs with the recommendations in the Revised Report and has sent out tentative Waste Discharge Requirements for your review. If you have any questions, you may contact MsDevra Lewis at (916) 255-3119. t L ' V Y L. COHEN, P.E. Chief, Private Sites Cleanup Unit cc: Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, Stockton Port of Stockton, Office of Environmental and Regulatory Affairs, Stockton Mr. Jeffrey Baker, Tesoro Petroleum Companies, Inc., Auburn, WA Ms. Anne Wilkinson, Time Oil Company, Seattle, WA Mr. Richard Brandes, ST Services, Martinez Mr. Steve Osborn, Kinder Morgan Energy Partners, L.P., Rocklin Mr. Robert Horwath, URS Corporation, Oakland Mr. Jaff Auchterlonie, SECOR International Incorporated, Rancho Cordova