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1 � <br /> 0 San Joaquin County DIRECTOR <br /> r°�� Donna Heran,REHS <br /> �o Environmental Health De Department� ASSISTANT DIRECTOR <br /> ��I 600 East Main Street Laurie Cotulla,REHS <br /> ALA <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> r,! Carl Borgman,REHS <br /> q<iFaeN� Mike Huggins, REHS,RDI <br /> Website: www.sjgov.org/ehd Margaret Lagono, REHS <br /> Phone: (209)468-3420 Robert McClellon,REHS <br /> Fax: (209)464-0138 Jeff Carruesco, REHS, RDI <br /> Kasey Foley,REHS <br /> STEPHANIE FURGAL MAY 1 U 2007 <br /> CHEVRON ENVIRONMENTAL MANAGEMENT COMPANY <br /> 6001 BOLLINGER CANYON ROAD ROOM K2240 <br /> SAN RAMON CA 94583 <br /> RE: Chevron Service Station 9-2033 <br /> 508 Charter Way <br /> Stockton, California <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Site <br /> Assessment Report dated December 18, 2006, prepared and submitted by ARCADIS <br /> U.S., Inc. (ARCADIS BBL, formerly known as Blasland, Bouck & Lee, Inc.) on your <br /> behalf for the above-referenced site. This report presents and discusses the results from <br /> the advancement of ten cone penetrometer testing (CPT)/membrane interface probe <br /> (MIP) soil borings and paired direct-push borings advanced adjacent to nine of the ten <br /> CPT borings between July and August 2005 by SECOR International Incorporated. CPT <br /> borings were advanced to depths between 57 and 100 feet below ground surface (bgs) to <br /> characterize the soil lithology, stratigraphy, and identify potential petroleum hydrocarbon <br /> contamination beneath the above-referenced site, while direct-push soil borings (DP-1 <br /> and DP-3 through DP-10) were advanced between 55 feet bgs and 61.5 feet bgs to <br /> characterize soil lithology and collect depth-discrete soil and groundwater samples for <br /> analysis. <br /> Laboratory analyses detected high concentrations of total extractable petroleum <br /> hydrocarbons as diesel (TEPH-d) and total petroleum hydrocarbons as gasoline (TPH-g) <br /> in soil samples collected at approximately 20 to 40 feet bgs in boring DP-4, and at 25 feet <br /> bgs in boring DP-8. Boring DP-4 was located down gradient of the source areas that <br /> include the former and existing underground storage tanks (USTs) and dispenser islands; <br /> and boring DP-8 was located between the former USTs and former southern dispenser <br /> island. <br /> TEPH-d and TEPH as motor oil (TEPH-mo)were detected at concentrations between 160 <br /> and 230,000 micrograms per liter (µg/L) in every grab groundwater sample collected <br /> from the nine direct-push soil borings at depths between 35 and 60 feet bgs. Based on <br /> these results, BBL proposes the installation of four monitoring well clusters to confine <br /> and monitor chemicals of concern (COC) both in the upper water table (approximately 20 <br /> feet bgs) and in the deeper water zone at approximately 50 to 60 feet bgs. <br />