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V � <br /> San Joaquin County DIRECTOR <br /> Environmental Health Department Donna Heran,REHS <br /> ASSISTANT DIRECTOR <br /> 600 East Main Street Laurie Cotulla,REHS <br /> :{ Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Carl Borgman,REHS <br /> C' •. P Mike Huggins, REHS,RDI <br /> Website: www.sjgov.org/ehd 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 /> August 8, 2008 <br /> Mr. Michael Karvelot <br /> Quik Stop Markets Incorporated <br /> 4567 Enterprise Street <br /> Fremont, California 94538 <br /> Subject: Quik Stop Station No. 076 <br /> 1030 South Olive Avenue <br /> Stockton, CA 95215 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed <br /> analytical results for groundwater samples collected from monitoring well MW-1 <br /> between June 2005 and June 2008, submitted on your behalf by Horizon Environmental <br /> Inc. (Horizon). Concentrations of total petroleum hydrocarbons quantified as gasoline <br /> (TPH-g) have steadily declined since February 2006 when TPH-g was detected at 4,800 <br /> micrograms per liter (pg/L) in groundwater samples collected from MW-1. Data from <br /> quarterly groundwater monitoring are suggestive that the decline in TPH-g concentrations <br /> parallels the increase in groundwater levels above the well's screened interval of sixty to <br /> eighty feet below surface grade (bsg). Additional site investigation is necessary to assess <br /> the lateral and vertical extent of impacted groundwater. The EHD recommends that a <br /> minimum of four hydropunch samples be collected in the silty sand encountered at sixty- <br /> five feet bsg to delineate the lateral extent of impacted groundwater, and one hydropunch <br /> sample be collected at the source area to delineate the vertical extent of impacted <br /> groundwater. PIease submit a work plan to the EHD by October 27, 2008, to assess the <br /> lateral and vertical extent of the total petroleum hydrocarbon plume. <br /> The Central Valley Regional Water Quality Control Board (CVRWQCB) is requiring <br /> evaluation of Environmental Screening Levels (ESLs), California Human Health <br /> Screening Levels (CHHSLs), (San Francisco Bay Regional Water Quality Control Board) <br /> and the potential for vapor intrusion into buildings for closure consideration of sites <br /> having residual contamination left in place. Therefore, you are directed to evaluate the <br /> potential for vapor intrusion inside the buildings located onsite. Please submit a work <br /> plan to EHD by October 27, 2008, to assess the potential for vapor intrusion into the <br />