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1 <br />, <br />1�'Rqu`N'..pp <br />0 <br />0 <br />San Joaquin County <br />Environmental Health Department <br />600 East Main Street <br />Stockton, California 95202-3029 <br />Website: www.sjgov.org/ehd <br />Phone: (209) 468-3420 <br />Fax: (209) 464-0138 <br />' STEPHANIE FURGAL <br />CHEVRON ENVIRONMENTAL MANAGEMENT COMPANY <br />6001 BOLLINGER CANYON ROAD ROOM X2240 <br />SAN RAMON CA 94583 <br />DIRECTOR <br />Donna Heran, REHS <br />ASSISTANT DIRECTOR <br />Laurie Cotulla, REHS <br />PROGRAM COORDINATORS <br />Carl 60r9man, REHS <br />Mike Huggins, REHS, RDI <br />Margaret Lagodo, REHS <br />Robert MCClellon, REHS <br />Jeff Carrueseo, REHS, RDI <br />Kasey Foley, REHS <br />MAY 10 2009 <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 />II <br />I <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 southem 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 (gg/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 concem (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 />