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i <br /> San Joaquin County DIRECTOR <br /> Donna Heran, REHS <br /> p.?�'u'�M •C Environmental Health Department ASSISTANT DIRECTOR <br /> ?•' = � '�L Laurie Cotulla,REHS <br /> Z: , 600 East Main Street <br /> a' Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> ` Carl Borgman,REHS <br /> ~�,•' Mike Huggins, REHS,RDI <br /> c •.. �P Website: www.sjgov.org/ehd Margaret Lagorio,REHS <br /> < <br /> q F o'R�' Phone: (209) 468-3420 Robert McClellon,REHS <br /> Fax: (209) 464-0138 .teff Carruesco,REHS, RDI <br /> Kasey Foley,REHS <br /> October 1,2008 <br /> Mr. and Mrs. Jay Mellrath <br /> Post Office Box 326 <br /> Stockton, California 95201 <br /> Subject: Jay's Mini Mart <br /> 3302 West Lane <br /> Stockton, California 95204 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Site Closure Report <br /> dated July 28, 2008, prepared and submitted by ATC Associates Incorporated (ATC) on your behalf <br /> for the above-referenced site. Included in the report were an indoor vapor intrusion air risk <br /> assessment and a sensitive receptor survey. <br /> To assess the potential for vapor intrusion into existing buildings onsite, ATC compared groundwater <br /> analytical data to Tier 1 Environmental Screening Levels (ESLs) (San Francisco Bay Regional Water <br /> Quality Control Board), and California Primary and Secondary Maximum Contaminant Levels <br /> (MCL), and reported that concentrations of total petroleum hydrocarbons (TPH) quantified as diesel <br /> (TPH-d), TPH quantified as gasoline (TPH-g), benzene, methyl tertiary-butyl ether(MTBE), and 1,2- <br /> dichloroethane (1,2-DCA) exceeded the ESLs in groundwater samples collected from soil boring <br /> SB-3. Concentrations of benzene and 1,2-DCA also exceeded the primary MCLS, and MTBE <br /> concentrations exceeded the secondary MCLs. However, the concentrations of contaminants of <br /> concern in groundwater samples collected from monitoring wells at the site were below Tier 1 ESLs, <br /> primary MCLs, and secondary MCLs,. ATC also compared the highest concentrations of the <br /> contaminants of concern detected in soil (except benzene where an average concentration was applied <br /> without a technical justification for the departure from the data handling utilized for the other <br /> compounds.) to the Tier I ESLs and Preliminary Remediation Goals (PRGs) (United States <br /> Environmental Protection Agency, Region 9) and reported that the concentrations of benzene and <br /> MTBE in soil exceeded the Tier 1 ESLs. <br /> ATC performed a Tier 2 modeling of vapor intrusion to indoor air using the Johnson and Ettinger <br /> Vapor Intrusion Model, Version 3.0 (2003). Except for the 1,2-DCA concentration taken from soil <br /> boring SB-3, ATC inputted concentrations-detected in groundwater collected from quarterly sampling <br /> events into the model instead of the much higher concentrations detected in grab groundwater <br /> samples collected from soil borings B1-W and SB-3. As there are no groundwater monitoring points <br /> near either of these sampling points, this data should have been utilized, or a technical justification for <br /> the exclusion provided. Except for MTBE and toluene concentrations, ATC inputted soil <br /> concentrations into the model that did not reflect the highest concentrations detected in soil samples. <br />