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San Joaquin County <br /> "..� Environmental Health Department DIRECTOR <br /> Donna Heran, REHS <br /> 600 East Main Street <br /> � X Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Robert McClellon, REHS <br /> -r - Jeff Carruesco,REHS, RDI <br /> 9�IFORN` - <br /> Website: WWW.SJgOV.Org/ehd Kasey Foley,REHS <br /> - Linda Turkatte,REHS <br />' Phone: (209) 468-3420 <br /> Fax: (209)464-0138 <br /> October 12, 2010 <br /> i <br /> Mr. Gerald L. Thiemann <br /> 327 Blossom Drive <br /> Ripon, California 95366 <br /> Subject: Former Thiemann's Service Station <br /> 106 West Second Street <br /> Ripon, California 95366 <br /> Dear Mr. Thiemann: <br /> The .,San Joaquin County Environmental Health Department (EHD) has reviewed i <br /> Addendum to ATG's Additional Subsurface Investigation at Former Thiemann's Service <br /> Station (addendum), dated 23 September 2010, prepared by ATC Associates, <br /> Incorporated (ATC) for the above-referenced subject site on your behalf. The addendum <br /> was submitted in response to EHD's email dated 26 August 2010 in which the EHD <br /> recommended that ATC prepare an addendum to Summary Report of Additional <br /> Subsurface Investigation, dated 16 August 2010, and compare residual soil concentrations <br /> of contaminants of concern to Environmental Screening Levels (ESLs) (San Francisco <br /> Bay Regional Water Quality Control Board), and California Human Health Screening <br /> Levels (CHHSLs) (California Environmental Protection Agency Office of Environmental <br /> Health Hazard Assessment). The EHD had initially directed the comparison of residual <br /> soil concentrations of petroleum hydrocarbon contaminants to ESLs and CHHSLs by <br /> letters dated 24 September 2009, and 02 March 2010. <br /> In the addendum, ATC lists the highest soil concentrations reported for total petroleum <br /> hydrocarbons as gasoline (TPH-g), and benzene, toluene, ethylbenzene, total xylenes <br /> (BTEX) detected in soil samples collected in the source area from soil borings TH-1, TH-3, <br /> TH-4, and SBA through SB-3, and provides the ESLs for these compounds in shallow soil <br /> at commercial/industrial property. ATC concludes that: <br /> • Soil concentrations of TPH-g and BTEX collected,in 1993 from TH-1, TH-3 and <br /> TH-4 exceed the ESLs; <br /> The residual impact to the vadose zone appears to be limited to the east side of <br /> the former tank excavation from 10 to 30 feet below surface grade with the plume <br /> extending northeast to West Second Street; <br /> • Soil concentrations have decreased significantly in the source area as indicated by <br /> results reported for soil samples collected in 1998 from soil boring SBA located in <br /> the same general vicinity as TH-1', TH-3, and TH-4; and <br />