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%Vol, 1%W <br /> San Joaquin County DIRECTOR <br /> Donna Heran,REHS <br /> Environmental Health Department� ,���•..Q p ASSISTANT DIRECTOR <br /> GLaurie Cotuila,REHS <br /> 600 East Main Street <br /> Stockton, California 95202-3029 <br /> PROGRAM COORDINATORS <br /> s Mike Huggins,REHS,RDI <br /> Margaret Lagorio, REHS <br /> CQ .. -.'• �P Website: www.sjgov.org/ehd Robert McClellan,REHS <br /> Lr�otz <br /> Phone: (209) 468-3420 Jett Carruesco,RENS,RDI <br /> Fax: (209) 464-0138 Kasey Foley, REHS <br /> July 22, 2009 <br /> David Atwater <br /> Van De Pol Enterprises <br /> P O Box 1107 <br /> Stockton CA 95201 <br /> Subject: California Fuels Station <br /> 2402 Pacific Avenue <br /> Stockton CA 95204 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Work <br /> Plan Addendum (WP) dated February 10, 2009, and Quarterly Report —Fourth Quarter <br /> 2008 (QR) dated March 19, 2009, prepared by Advanced GeoEnvironmental, Inc. <br /> (AGE). In the WP AGE proposes to: <br /> • Advance 3 soil confirmation borings (B-11, B-12, and B-13) to conduct a soil gas <br /> investigation to evaluate the potential for soil vapor intrusion <br /> • Convert the borings to soil vapor extraction (SVE) wells; and <br /> • Conduct a soil vapor extraction (SVE) rebound test <br /> The EHD approves the SVE rebound test and advancing the confirmation borings, <br /> however only borings yielding soil indicating significant contamination should be <br /> converted to SVE wells. The WP for the soil gas sampling investigation lacks a leak <br /> detection protocol for the soil gas samples. You will need to submit a work plan <br /> addendum to address soil gas sample leak detection to the EHD before the EHD can <br /> approve the work plan. <br /> This site appears to be approaching the point for closure consideration. Favorable <br /> results from the proposed soil vapor intrusion survey, the confirmation borings, and SVE <br /> rebound test will strengthen the case for site closure. The groundwater plume appears to <br /> be defined laterally in all directions by "non-detect" groundwater sample results from <br /> shallow monitoring wells MW-1 though MW-12 with screen intervals ranging between 20 <br /> and 50 feet below surface grade (bsg). However, the vertical extent of impacted <br /> groundwater may not be defined in the source area by deeper monitoring wells MW-13A <br /> through MW-13C or airsparge wells AW-2A and AW-2B. The EHD suspects that the <br /> data from the MW-13 wells may be demonstrating cross contamination. AW-2A has <br /> exhibited a significant rebound since shutting down the SVE system in March 2007 with <br /> an increasing trend from 1,200 pg/l to 9,300 ,ugll TPH-g. The deeper impact near MW- <br /> 13A though MW-13C and the vertical extent of groundwater contamination in the source <br /> area must be demonstrated for closure consideration. <br /> In the QR, AGE recommends reducing the frequency of groundwater sampling in <br /> selected monitoring wells. The EHD concurs with AGE's recommendation and directs <br />