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San Joaquin County DIRECTOR <br /> Donna Heran,REHS <br /> Environmental Health Department ASSISTANT DIRECTOR <br /> Laurie Cotulla,REHS <br /> 600 East Main Street <br /> , <br /> 'g StocktonCalifornia 95202-3029 PROGRAM COORDINATORS <br /> J < <br /> .. ..` Carl Borgman,REHS <br /> Mike Huggins,REHS,RDI <br /> • c ,-�--.. P Website: www.sjgov.org/ehd Margaret Lagorio,REHS <br /> 4CiFO R� Phone: (209) 468-3420 Robert McClellon,REHS <br /> Fax: (209) 464-0138 Jeff Carruesco,REHS,RDI <br /> June 30, 2008 Kasey Foley,REHS <br /> Mr. Paul Zumberge <br /> Frontier Transportation, Incorporated <br /> 425 Larch Road <br /> Tracy, California 95376 <br /> Subject: Frontier Transportation, Incorporated <br /> 425 Larch Road <br /> Tracy, California 95376 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Aquifer <br /> Pump Test Report of Findings dated November 8, 2006, and 2008 P Quarter <br /> Groundwater Monitoring Report dated May 23, 2008, prepared and submitted by <br /> Biophysics Environmental Assessments, Inc. (BEA), on your behalf. During the aquifer <br /> pump test, groundwater was removed from monitoring well MW-3R at a rate of <br /> approximately two-and-a-half gallons per minute for four hours followed by a two-hour <br /> recovery phase. During this time, groundwater measurements were collected from <br /> observation wells MW-3R, MW-22, MW-23, and MW-24, screened between five and <br /> twenty feet below surface grade (bsg), and MW-13, screened between thirty and forty <br /> feet bsg. Results from the test indicate favorable drawdown (approximately four feet in <br /> MW-3R) in the shallow wells while groundwater measurements in deep well MW-13 <br /> remained unchanged. The radius of influence was estimated to be approximately ninety- <br /> five feet. <br /> In the current report, 2008 1" Quarter Groundwater Monitoring Report, BEA reported <br /> that high concentrations of methyl tertiary-butyl ether (MTBE) are present in <br /> groundwater samples collected from monitoring wells screened between five and twenty <br /> feet bsg in the source area and west of the source area in MW-24, located approximately <br /> two hundred feet from the former underground storage tanks. BEA has recommended <br /> that pump and treat be initiated in the source area, and adsorbent socks filled with <br /> Caiphene be installed in shallow wells where high concentrations of petroleum <br /> hydrocarbons have been reported in groundwater. <br /> Before the EHD can respond to BEA's recommendations, a comparison of the proposed <br /> remedial methods to several other potential remedial methods to determine the most cost- <br /> effective for removing petroleum hydrocarbon contaminants based on site specific data <br /> and cost effectiveness must be provided to the EHD for review. In December 2005, BEA <br />