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San Joaquin County DIRECTOR <br /> A <br /> Environmental Health Department Donna Heran,REHS <br /> p ASSISTANT DIRECTOR <br /> z 2 600 East Main Street Laurie Cotulla,REHS <br /> N: { Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Carl Borgman,REHS <br /> cq �;�P Website: www.Sjgov.org/ehd Mike Huggins,REHS,RDI <br /> C i F 610 Margaret Lagorio,REHS <br /> Phone: (209)468.3420 Robert McCiellon,REHS <br /> Fax: (209) 464-0138 .teff Carruesco,REHS,RDI <br /> Kasey Foley,REHS <br /> KEN HILLIARD JUN 19 2007 <br /> 7—ELEVEN <br /> P.O. BOX 711 <br /> DALLAS, TX. 95221-0711 <br /> RE: 7-ELEVEN STORE 21756 LOP SITE CODE: 1369 <br /> 853 E. Yosemite Ave. <br /> Manteca, CA <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed the Site <br /> Closure Request dated 14 April 2006 and the Site Closure Request dated 31 October <br /> 2006 prepared by Secor for the above referenced site. EHD denies the request for site <br /> closure at this time. This decision is subject to appeal to the State Water Resources <br /> Control Board (SWRCB), pursuant to Section 25296.40(x)(1) of the Health and Safety <br /> Code (Thompson-Richter Underground Storage Tank Reform Act— Senate Bill 562). <br /> Please contact the SWRCB Underground Storage Tank Program at(916) 341-5752 for <br /> information regarding the appeal process. <br /> To date six geoprobe (GP) soil borings,'two sparge/vent wells (SPV), and four <br /> monitoring wells (MW) have been completed for the site investigation and remedial <br /> testing. Vapor extraction testing reduced some of the contaminant mass caused by the <br /> unauthorized release from the former USTs. Results of the groundwater samples from <br /> the MWs show a decline in the concentration of MTBE (the contaminant of concern)and <br /> were below the detection limit for MTBE when last sampled in August 2005. <br /> The predominant groundwater flow direction for the site during the investigation has <br /> been to the west/northwest and the highest concentrations of MTBE in the soil and <br /> groundwater were found in MW1 which is west/northwest of the former UST location. <br /> MW 2 (southwest of the former UST area) and MW3 (nVrthwest tithe former UST area) <br /> are located closer to the former UST area than MW1 but MTBE concentrations in the <br /> samples from these wells have been lower than those found in MW1. MW4 is furthest <br /> from and northwest of the former UST area and has not evidenced any MTBE <br /> contamination. The highest concentrations of MTBE in the soil were found at 20 and 25 <br /> feet below ground surface (bgs), which is below groundwater. <br /> In order to concur with closure of this site, current information is required. Quarterly <br /> sampling events should be performed and the groundwater samples must be analyzed <br /> for total petroleum hydrocarbons as gasoline, BTEX, MTBE, TBA, TAME, ETRE, DIPE <br /> 1,2-DCA and EDB. In addition, soil and water samples must be collected <br /> west/northwest of MW1 to show that the 525 mg/kg of MTBE in the soil sample from <br /> MW1 at 25 feet does not exist and that the MTBE in the groundwater did not m7JU <br /> P 1 2007 <br /> _ I <br />