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San Joaquin County <br /> Environmental Health Department DIRECTOR <br /> �• =--�f •9 Donna Heran, REHS <br /> � • �'�`� 600 East Main Street <br /> y { Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Robert McClellon, REHS <br /> Jeff Carruesco, REHS, RDI <br /> Kasey Foley,REHS <br /> 4�/FORS` Website: www. <br /> sjgov.org/ehd Linda Turkatte,REHS <br /> Phone: (209) 468-3420 <br /> Fax: (209)464-0138 <br /> February 18, 2011 <br /> Mr. Den and Ms. Betty Ueda <br /> 626 East Galin Road <br /> French Camp, California 95231 <br /> Subject: Den's Auto Repair <br /> 308 South EI Dorado Street <br /> Stockton, California 95203-3404 <br /> Dear Mr. and Mrs. Ueda: <br /> The San Joaquin County Environmental Health Department (EHD) has received and <br /> reviewed Ozone Bench Scale Test Report (report), dated 26 October 2010, prepared and <br /> submitted by Advanced GeoEnviron mental, Inc. (AGE) on your behalf for the above- <br /> referenced subject site. By letter dated 15 April 2010, the EHD had conditionally approved <br /> the ozone bench-scale test. <br /> The report documents the soil and groundwater analytical results from the seven-day <br /> injection of ozone followed by a 12-day study of the aftereffects, and a separate study of the <br /> effects of in-situ oxygen sparging on groundwater samples. Results were similar between <br /> soil samples collected from boring OB-1 at 45, 50, and 65 feet below surface grade (bsg) <br /> combined with groundwater from monitoring well MW-1A, screened from 60 to 65 feet bsg, <br /> and soil samples collected from boring OB-2 at 45, 50, and 65 feet bsg combined with <br /> groundwater from monitoring well MW-2A, screened from 60 to 65 feet bsg. A brief <br /> summary of the ozone bench scale test and in-situ oxygen sparging findings are presented <br /> below: <br /> • Hexavalent chromium was not detected in the initial groundwater samples <br /> collected from MW-1A and MW-2A, but was detected in both combined-soil-and- <br /> groundwater samples collected on day one, with hexavalent chromium <br /> concentrations increasing throughout the seven-day bench scale test; the highest <br /> concentration of hexavalent chromium, detected on the seventh and final day of <br /> ozonation, was 390 micrograms per liter (Ng/L) in the soil/groundwater samples <br /> collected from OB-2/MW-2A. After ozone injection was terminated, concentrations <br /> of hexavalent chromium decreased in both soil/groundwater samples to less than <br /> 12 pg/L. Analytical results for hexavalent chromium generated by oxygen sparging <br /> were not reported. <br /> • Bromate was not detected in the initial groundwater samples collected from <br /> MW-1A and MW-2A, but was detected at 930 pg/L and 1,300 pg/L in soil- <br />