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f v �„► <br /> San Joaquin County DIRECTOR <br /> Po I N Donna Heran,REHS <br /> Environmental Health Department ASSISTANT DIRECTOR <br /> 2: 600 East Main Street Laurie Cotulla, REHS <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Carl Borgman,REHS <br /> Website: www.s OV.or 1ehd Mike Huggins, REHS,RDI <br /> 4CrFORc� /8 g Margaret Lagorio, REHS <br /> Phone: (209) 468-3420 Robert McClellon, REHS <br /> Fax: (209)464-0138 Jeff Carruesco, REHS,RDI <br /> Kasey Foley,REHS <br /> GERALD L. THIEMANN OCT 11 2007 <br /> 327 BLOSSOM DRIVE <br /> RIPON CA 95366 <br /> RE: Former Thiemann's Service Station SITE CODE: 1479 <br /> 106 West Second Street <br /> Ripon, California 95366 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed analytical <br /> results for groundwater samples collected quarterly at the above-referenced site. <br /> Groundwater samples have not been analyzed for 1,2-dichloroethane (1,2-DCA) and 1,2- <br /> dibromorethane (EDB) for over two years. Analyze groundwater samples for these <br /> compounds, reporting concentrations at 0.5 micrograms per liter (0.5 pg/L), during the next <br /> sampling event and include these results in future analytical tables included in quarterly l <br /> reports. If 1,2-DCA and EDB are not detected in any groundwater samples, these <br /> compounds may be omitted from future sampling events. <br /> EHD approves a reduction in sampling frequency of monitoring wells MW-4 and MW-6 <br /> from quarterly to annually if groundwater results that include analyses for 1,2-DCA and <br /> EDB are nondetect during the next sampling event. Continue to collect depth to water <br /> measurements for every monitoring well during each quarterly groundwater monitoring <br /> event for the purpose of determining the groundwater gradient. <br /> The six-onsite monitoring well casing elevations must be surveyed by a California licensed <br /> professional and the elevation along with the latitude and longitude of the groundwater <br /> monitoring wells (including permanent sampling point designation) must be submitted <br /> electronically to GeoTracker, the State Water Resources Control Board database program. <br /> The well survey must be completed by December 14, 2007, and a hardcopy of the survey <br /> report must be submitted to EHD. <br /> Please note that the Central Valley Regional Water Quality Control Board (CVRWQCB) is <br /> requiring evaluation of site data against the Environmental Screening Levels (ESLs) issued <br /> by the San Francisco Bay Regional Water Quality Control Board, California Human Health <br /> Screening Levels (CHHSLs), and an evaluation of the potential for vapor intrusion into <br /> buildings. Therefore, you need to evaluate the potential threat for vapor intrusion inside <br />