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San Joaquin County <br /> Environmental Health Department DIRECTOR <br /> M <br /> Donna Heran,RENS <br /> r — 2, 600 East Main Street PROGRAM COORDINATORS <br /> Q <br /> �- -< Stockton, California 95202-3029 Robert McClellon,REHS <br /> 'i Jeff Carruesco,REHS,RDI <br /> _ Kasey Foley,REHS <br /> • dq, --.��p' Website: wwwsjgov.org/ehd Linda Turkatte,REHS <br /> /FOR Phone: (209) 468-3420 <br /> Fax: (209)464-0138 <br /> February 4, 2011 <br /> Mr. Paul Zumberge <br /> Frontier Transportation, Incorporated <br /> 3577 West Philadelphia <br /> Chino Hills, California 91710 <br /> Subject: Frontier Transportation, Incorporated <br /> 425 Larch Road <br /> Tracy, California 95376 <br /> Dear Mr. Zumberge: <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Corrective <br /> Action Plan (CAP), dated 18 October 2010, prepared and submitted by your consulting firm, <br /> Ami Adini & Associates, Inc. (AA&A), on your behalf. The CAP was submitted in response to <br /> the EHD directive by letter dated 21 May 2010. In the CAP, AA&A compared six technologies <br /> to determine the appropriate remedial method to mitigate impacted groundwater and capillary- <br /> zone impacted soil at the above-referenced subject site. AA&A concluded, based on site <br /> conditions, that high vacuum dual-phase extraction (HVDPE) would be the most suitable and <br /> cost-effective remedial alternative for this site. <br /> The EHD has reviewed the historical quarterly and semi-annual groundwater results and has <br /> identified a number of monitoring wells where the methyl tertiary-butyl ether (MTBE) <br /> concentrations have shifted abruptly, as much as one to two orders of magnitude. This could <br /> indicate an unstable plume or mass variations due to currently unrecognized factors. <br /> In view of the apparent on-site variability of dissolved concentrations of MTBE, the <br /> groundwater analytical results from the eight off-site soil borings in September 2010 among <br /> which MTBE was detected only in the down-gradient borehole 68 at approximately 50 <br /> micrograms per liter (Ng/L), and the sampling results from two down-gradient domestic wells <br /> where contaminants of concern were not detected in June 2010 (indicating that no sensitive <br /> receptors appear to be threatened), the EHD believes the necessity for active remediation <br /> should be reevaluated. <br /> To assist the EHD to determine whether corrective action is necessary based on recently <br /> acquired information, please submit to the EHD an evaluation of the fluctuations in MTBE <br /> concentrations as they apply to: <br />