Laserfiche WebLink
Mr. Paul Supple - 2 - 6 23 August 2004 ' <br /> ARCO evaluated the upper confidence limit of the 95`h percentile and the highest concentration detected <br /> in AR/MW-lA without using anomalous detections. The revised baseline levels were selected by <br /> taking either twice the highest concentration detected in AR/MW-1A or the upper confidence limit of <br /> the 95`h percentile, whichever was the greater value. ARCO now has assigned baseline levels for sulfide <br /> and total phosphorous, which were not originally proposed. Regional Board staff concurs with the <br /> revised proposed baseline concentrations for AR/MW-1A listed below: <br /> Constituent Previous Baseline Revised Baseline <br /> Nitrate as Nitrogen 3.54 mg/l 8.86 mg/l <br /> Sulfate 5.23 mg/1 11.2 mg/l <br /> Total Nitrogen 1.64 mg/1 2.8 mg/l <br /> Sodium 114.92 mg/l 114.92 mg/l <br /> Ammonium as Nitrogen 0.25 mg/1 0.42 mg/1 <br /> ortho-phosphate 1.21 mg/1 1.21 mg/1 <br /> Sulfide 0.29 mg/1 <br /> Total Phosphorous 4.45 mg/l <br /> Based on the revised baseline concentrations, ARCO may re-start the weekly injections. Although the <br /> pilot study is now in monthly monitoring according to Monitoring and Reporting Program No. <br /> R5-2004-0164, ARCO needs to collect samples a week after the next injection to verify the progress of <br /> the system during the time that injections did not occur and to monitor the results of the first injection <br /> after 10 weeks of no injections. The first monitoring report for the pilot study is due by <br /> 1 November 2004. If you have any questions, you may contact Devra Lewis at (916) 464-47119. <br /> L , Q,-uv <br /> WENDY 1. COHEN, P.E. <br /> Chief, Private Sites Cleanup Unit <br /> cc: Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, Stockton <br /> Port of Stockton, Office of Environmental and Regulatory Affairs, Stockton <br /> Mr. Robert Horwath,URS Corporation, Oaklan3 <br />