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iI q k <br /> J <br /> TAIFE OF CALIFORNIA - .. PETE WILSON. Governor <br /> 'ALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— "`�,� <br /> ,ENTRAL VALLEY REGION <br /> a F <br /> 443 ROUTIER ROAD, SUITE A s <br /> ACRAMENTO, CA 95827-3098 - <br /> HONE: (916) 361-5600 <br /> AX: (916) 361.5686 <br /> �. \17 <br /> 7 <br /> f <br /> J U L 3. 1 1001 _ <br /> 30 July .,1991 ENVIRONMENTAL HEALTH <br /> PERMIT/SERVICES <br /> iu , G <br /> Ms. Mary Meays <br /> San Joaquin County Environmental :Health <br /> P.O. Box 2009 <br /> Stockton, CA 95201: <br /> FORMER CHEVRON #9-7780, 3245 EAST FREMONT STREET, STOCKTON,° SAN�joAQUIN COUNTY <br /> I have reviewed the file for this site and a !tecent "Quarterly Ground Water <br /> Monitoring Report" dated 4 June 1991 , prepared by Alton Geoscienice.l Chevron's <br /> cover letter to the 4 June 1991 report reques=ted closure consideration. <br /> The depth to ground water has increased about 35 feet since thei!investigation <br /> began in 1987 from about 40 feet in 1987 to about 75 feet in Apri,l _1991. The <br /> three original wells, installed by Groundwater Technology in 1987, contained <br /> significant ground water contamination the list time they were S'amp'led in <br /> February 1988.. The three wells were dry since February 1989 and have since <br /> been destroyed due to the poor condition of the' tops of the wells. ! EA I , <br /> Engineering installed four monitoring wells iii 1988, the deepest of,, the wells <br /> was 65 feet. At that time, one of the wells 'contained significant ground <br /> water contamination, two contained low levels] of contamination, I;and.Ithe fourth <br /> contained non-detectable levels. All of these wells have been dry since <br /> September 1989 but are in good condition and were not destroyed:: EA installed <br /> two more wells in August 1990 which have had non-detectable levels of <br /> contamination since they were installed. Welk EA-6 is near theformer tank, <br /> pit, the apparent source of contamination. <br /> Our file does not contain any information from" Blaine Technical !Services, who <br /> removed the tanks and collected. the soil samples from the excavation. The <br /> dimensions of the pit, especially' the final depth, are not clear: from the <br /> information we do have. Sample #218 was collected at 18 feet and contained ' <br /> 1100 ppb TPH as gasoline, however, it is not clear whether this wavia bottom <br /> sample and whether this contamination was left in place or the excavation' <br /> continued. Sample #3 was collected at 14 feet, but again, it is. not clear <br /> whether this was a side sample and whether it,'was left in place or the <br /> excavation continued. <br /> I . <br /> Based on the non-detectable levels of ground water contaminatioW', and the 35' <br /> foot drop in the water elevation, it appears that ground water contamination <br /> may no longer be present, however, it is probable that soil contamination does <br /> remain in' place. I recommend that Chevron collect at least two more rounds"of <br /> r. i. <br /> l <br />