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a NVE4 <br /> San Joaquin County DIRECTOR <br /> " Environmental Health Department <br /> Donna Heran,REHS <br /> 600 East Main Street ASSISTANT DIRECTORLaurie Cotulla,REHS <br /> Stockton, California 95202-3029 <br /> PROGRAM COORDINATORS <br /> Margaret Lagorio,REFS <br /> c4 F pR��P Website: www.sjgov.org/ehd Robert McClellan, REHS <br /> Phone: (209) 468-3420 Jeff Carruesco, REHS, RDI <br /> Fax: (209) 464-0138 Kasey Foley, REHS <br /> September 24, 2009 <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 /> Tl-ie -San Joaquin County Environmental Health Department has reviewed Summary <br /> Report of Additional Subsurface Investigation (report), dated June 23, 2009, prepared by <br /> ATC Associates, Incorporated (ATC), for the above-referenced site on your behalf. In <br /> October 2008, three cone penetration test (CPT) borings were advanced on- and off-site <br /> and grab groundwater samples were collected adjacent to each CPT boring. Analytical <br /> results from this investigation indicate that significant concentrations of total petroleum <br /> hydrocarbons quantified as gasoline (TPH-g) [23,000 micrograms per liter (Ng/L)], toluene <br /> (330 pg/L), ethyl benzene (1,200 Ng/L), and total xylenes (4,500 pg/L) were detected at <br /> approximately thirty-five feet below surface grade (bsg) in grab groundwater samples <br /> collected from borehole CPT3-35. The boring was located in the turn-lane of West <br /> Second Street, approximately thirty-eight feet north of monitoring well MW-2. At lower <br /> concentrations, the same constituents were detected in a grab groundwater samples <br /> collected at 112 feet bsg in soil boring CPT2-112, located approximately thirty feet <br /> southwest of MW-3. Additional investigation is needed to define the petroleum <br /> hydrocarbon plume north of MW-2. Please submit a work plan to the EHD by November <br /> 30, 2009. <br /> Review of historical groundwater analytical data collected from MW-2 and MW-3 appears <br /> to indicate that during the first quarter 2003, groundwater concentrations decreased <br /> significantly in MW-3 while increasing significantly in MW-2 during the first quarter 2005, <br /> possibly indicating a shift in the groundwater plume. Furthermore, soundings from the <br /> three CPT borings indicate a thick sand layer at approximately thirty to forty feet bsg, and <br /> thin sand layers in an interval approximately 108 to 112 feet bsg. <br /> Based on the information presently above, the EHD does not believe this site should be <br /> considered for closure as a low risk case as recommended by ATC in the report. This <br /> decision is subject to appeal to the State Water Resources Control Board (State Water <br /> Board), pursuant to H&SC Section 25296.40(x)(1), (Thompson-Richter Underground <br /> Storage Tank Reform Act — Senate Bill 562). Please contact the State Water Board <br /> Underground Storage Tank Program at (916) 341-5752 or visit the State Water Board <br /> internet website at http://w-ww.waterboards.ca.gov/ust/cleanup/petitions.html for <br /> information regarding the appeals process. <br />