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San Joaquin County DIRECTOR Environmental Health Department Donna Heran,REHS eN e "3OG N g 600 East Main Street ASSISTANTDIRECTORLaurie Cotulla,REHS Stockton, California 95202-3029 i PROGRAM COORDINATORS Mike Huggins,REHS,RDI Website:WWW.SJgov,orglehd Margaret Lagorio,REHS Phone: (209)468-3420 Robert Mcasilon,REHS Jeff Carruesco,REHS,RDI Fax: (209)464-0138 Kasay Foley,REHS June 5,2009 r Mr.Michael Karvelot Quik Stop Markets,Incorporated 4567 Enterprise Street i Fremont, California 94538 � Subject: Quik Stop Market No. 132 3555 West Hammer Lane Stockton, California 95209 i The San Joaquin County Environmental Health Department (EHD) has reviewed Additional Investigation Work Plan dated May 18, 2009, prepared by ATC Associates Inc. (ATC) for the above-referenced site on your behalf. The work plan was submitted in response to a letter dated September 23, 2008, from the EHD directing you to address: the lateral extent of petroleum hydrocarbon contamination in the first water-bearing zone identified by the-EFID to be approximately five to ten feet below surface grade (bsg); the vertical extent of petroleum hydrocarbon contamination in groundwater near soil borings ATC-5 and SB-2 where methyl tertiary-butyl ether (MTBE) was detected at 39 micrograms per liter (pg/L) at forty-two feet bsg, and 500 pg/L at twenty-nine feet bsg, respectively; and the petroleum hydrocarbon contamination remaining in soil in the area of soil sample QS-2 collected at approximately ten feet bsg. i In the work plan, ATC proposes to advance three soil borings (SB4, SB-5, and SB-6) to address soil and groundwater data gaps that include: • Evaluation of the "horizontal' and "lateral" extent of impacted p groundwater near the former underground storage tanks(USTs), • Evaluation of the potential for methyl tertiary-butyl ether (MTBE) to migrate down gradient of the source area beneath the adjacent Taco Bell facility to the southeast,and • Evaluation of impacted soil that may remain near the original release at the north end of the pump island. ATC proposes to advance borehole SB-4 approximately eight feet cast/northeast of soil boring B-3, initially to an approximate depth of fifteen feet bsg. One soil sample is proposed to be collected at the capillary fringe, and one grab groundwater sample is proposed to be collected at approximately fifteen feet bsg. Then ATC proposes to advance the boring to approximately forty feet and collect a grab groundwater sample. The site map illustrating the proposed location for SB4 does not include j the approximate location where soil sample QS-2 was collected. Based on information on file at the EHD, the proposed location for SB-4 is not where soil sample QS-2 was collected; therefore, you must provide technical justification for the proposed sampling point for SB-4, collection of a grab groundwater sample at approximately fifteen feet bsg, and collection of a soil sample at the capillary fringe. f 1 1