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t <br /> San Joaquin County <br /> Environmental Health Department DIRECTOR <br /> Donna Heron, REHS <br /> 600 East Main Street <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> a,�� .� Robert McClellon,REHS <br /> �.... <br /> Jeff Carruesco,REHS,RDI <br /> Website: www.sjgov. Linda <br /> org/ehd Foley,REHS <br /> L j F gR P Linda Turkatte, RENS <br /> Phone: (209)468-3420 <br /> Fax: (209)464-0138 <br /> April 27, 2011 <br /> Randy Coil <br /> Atlantic Richfield Company <br /> 501 Westlake Park Blvd. <br /> WL1-28.160B <br /> Houston, TX 77079 <br /> Subject: ARCO Service Station No. 6100 <br /> 25775 S. Patterson Pass Road <br /> Tracy, California, 95377 <br /> San Joaquin County Environmental Health Department (EHD) has received by email and on <br /> GeoTracker AS/SVE Pilot Test Work Plan (WP) dated 17 February 2011, in which your <br /> consultant, Arcadis proposes to conduct an off-site soil vapor extraction (SVE) and air sparging <br /> (AS) pilot test to evaluate the effectiveness of the technologies for addressing off-site <br /> groundwater impacted by petroleum products released from the underground storage tank <br /> (UST) system on the site formerly owned by ARCO. <br /> To prepare for the pilot test, an AS well will be installed to an approximate depth of 110 feet <br /> below surface grade (bsg) near monitoring well MW-1, which will be utilized as an SVE well for <br /> the test. Soil samples will be collected continuously from 40 feet bsg to total depth to assess for <br /> petroleum hydrocarbon impact and to compile a continuous lithologic log to select the interval to <br /> set the air sparge well screen. Soil samples collected will be analyzed for total petroleum <br /> hydrocarbons quantified as gasoline (TPHg), benzene, toluene, ethylbenzene, and total xylenes <br /> (BTEX), methyl tert-butyl ether (MTBE), the five fuel oxygenates and lead scavengers. <br /> The pilot test will consist of four phases as follows: <br /> I. A vacuum step test utilizing MW-1 for extraction and other wells as observation wells; <br /> II. A constant rate SVE test to determine the radius of influence at the selected vacuum and <br /> assess the contaminant concentrations initially extracted at the vacuum pressure; <br /> III. A constant rate air sparge test to assess its effect on water level and pressure in the <br /> observation wells; and <br /> IV. A constant rate AS/SVE test to evaluate the effect of AS on the contaminant mass <br /> recovery rate. <br /> During the course of the pilot tests, the extracted air will be monitored for volatile organic <br /> compounds (VOCs), presumably utilizing a photo-ionization detector (PID) devise to quantify the <br /> hydrocarbon mass recovery rate. <br /> SVE-IAS Pilot Test Work Plan Approval Letter 0411.doc <br />