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San Joaquin County <br /> °"'"O••"""'••c <br /> DIRECTOR Health Department <br /> Donna Heran,RENS <br /> 1868 East Hazelton Avenue <br /> Stockton, California 95205-6232 PROGRAM COORDINATORS <br /> Robert McClellon,RENS <br /> Jeff Carruesco,REHS,RDI <br /> Kasey Foley,REHS <br /> Website: www.sjgov.org/ehd Linda Turkatte,REHS <br /> Phone: (209)468-3420 Rodney Estrada,REHS <br /> Fax: (209)464-0138 Adrienne Ellsaesser,REHS <br /> April 30, 2013 <br /> Mr. Daryl J. Pessler <br /> Chevron Environmental Management Company <br /> Marketing Business Unit <br /> 145 South State College Boulevard, Suite 400 <br /> Brea, California 92821 <br /> Subject: Former Chevron Service Station 9-0557 <br /> 139 South Center Street <br /> Stockton, California <br /> Dear Mr. Pessler: <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Low-threat <br /> Closure Request Report (report), dated 26 March 2013, submitted by your consulting firm, <br /> Holguin, Fahan & Associates, Inc. (HFA), on your behalf. In the report, HFA presented <br /> information to support site conditions that meet the general and media-specific criteria <br /> established in the Low-threat Underground Storage Tank Case Closure Policy (LTCP) enacted <br /> by the State Water Resources Control Board (State Water Board) on 17 August 2012. HFA <br /> concluded that case-closure requirements have been satisfied for LTCP, Health and Safety <br /> Code section 25296.10, and Resolution No. 92-49. <br /> The EHD is in general agreement with the conclusions presented in the report; however, before <br /> this agency can complete the site closure consideration, the following items need to be <br /> addressed: <br /> • Petroleum hydrocarbon contaminant concentrations continue to increase in groundwater <br /> collected from MW-15D. On page 8 of the report, HFA inadvertently stated that <br /> MW-15D was screened across the water table [currently at approximately 20 feet below <br /> surface grade (bsg)], and "the increasing trends in hydrocarbons (in MW-15D) are <br /> attributed to the rise in the groundwater elevations." Since MW-15D is screened well <br /> below the water table, between forty-six and fifty-one feet bsg, please provide an <br /> explanation why contaminants of concern continue to increase in groundwater monitored <br /> by MW-15D. <br /> • Provide the technical justification for the use of the geometric mean, rather than the <br /> arithmetic mean, when calculating the mass estimates of total petroleum hydrocarbons <br /> as gasoline (TPHg) in soil, and total petroleum hydrocarbons as diesel (TPHd) in <br /> groundwater. Also clarify why the height (h) was multiplied by 0.8 to get a volume of <br /> 7,700,000 cubic feet when calculating the TPHd mass in groundwater. <br />