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Advanced <br /> ,GeoEnvironmer�tal Ince <br /> i� :v <br /> 10 October 2003 REEN <br /> Vf <br /> AGE-NC Project No. 98-0468 <br /> OCT I 0 2003 <br /> ENVIRONMENT HEALTH <br /> Mr. James B. Giottonini <br /> PERMIT/SERVICES <br /> Ms. Sharla'Hardy <br /> City of Stockton <br /> 425 N. El Dorado Street, ThirdFloor <br /> Stockton, CA 95202 <br /> Subject: Closure Summary Report- MTBE Transport Model <br /> VAN BUSKIRK GOLF COURSE FACILITY <br /> 1740 Houston Avenue, Stockton, California <br /> Dear Ms. Hardy: ; <br /> ' i 'At the request of the City of Stockton,Advanced GeoEnvironmental,Inc. has prepared the enclosed <br /> closure summary fate. and transport model for the above-referenced site. As requested by.the <br /> California Regional Water Quality Control Board-Central Valley Region, an estimate of the travel <br /> time for a MTBE-plume to degrade to non-detections or reach the down-gradient-limits of the site <br /> is.required. <br /> " SITE CONDITIONS PLUME DISTRIBUTION <br /> Based on the findings from the CPT soil soundings collected in July.continuous sand units were <br /> encountered at 55 feet to 60 feet below surface grade(bsg) in CPT3,50 and 70 fe:,t bsg in CPT 1 and ' <br /> at-70 feet bsg in CPT5. Another significant-and continuous sand unit was encountered at 65 to 90 <br /> :,feet bsg. Silt and clay generally are the other stratigraphic soils internal to the section at.the site.^ <br /> MTBE has been detected in wells MW-3 through MW-10 at concentrations ranting from 0.84 gg/1 j <br /> (MW-8 in been <br /> 2002) to.1,100 ug/I (MW-4 in November 1999). MTBE was detected in the <br /> grab ground water'sam.ples collected from at 55 feet bsg (B9), down gradient of the former UST <br /> approximately 100 feet. The lateral migration of MTBE down-gradient from the former UST area <br /> is limited by well MW-7 and MW-8,CPT2 Low concentrations were detected in wells MW-9(B9) <br /> at 80 Ag/l and and MW-10 at 28µg/1. , <br /> Based on data acquired from a previous investigation at the site, the estimated area of the impacted <br /> ground water is 1100 ft from the fonner UST area to CPT2-, approximately 35 ft wide between wells <br /> and a thickness of 70 ft.. The average depth to ground water in the vicinity of the site is.10 to 12 feet <br /> AP <br /> 837 Shaw Road,Stockton, California 95215 <br /> Telephone(209)4674006 FAX(209) 46771118 <br />