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Working to Restore Nature <br /> 1710 Main Street <br /> Escalon, CA 95320 'R b. <br /> Phone: (209)838-3507 r i , d February 5, 1992 <br /> FAX: (209)838-3509EM <br /> n a "•+ ' `L �-} <br /> Ms. Laurie A. Cotulla � i� <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P.O. Box 2009 <br /> Stockton, CA 95201 <br /> Re: 1992 First Quarter Groundwater Monitoring Report, Genstar Western Stone site, <br /> 8181 E. 11th St., Tracy, CA (county site code: 1393) <br /> Dear Ms. Cotulla: <br /> This letter presents the results of RESNA's 1992 first quarter groundwater monitoring and <br /> sampling at the referenced site (Figure 1). Activities included monitoring depth to groundwater, <br /> purging of wells, groundwater sampling, and analysis of samples for total petroleum <br /> hydrocarbons as diesel (TPHD), benzene, toluene, ethylbenzene, and xylenes (BTEX). <br /> rr Groundwater monitoring and sampling was conducted on January 7, 1992. Depth to <br /> groundwater was measured in each well and subtracted from wellhead elevation to determine <br /> groundwater elevation (Table 1). Water levels in January were found to have decreased <br /> approximately .21 feet since last measured in October 1991. Figure 2 depicts the groundwater <br /> gradient on January 7, 1992. <br /> Gradient magnitude and groundwater flow direction were slightly changed since October 1991, <br /> at approximately .004 ft/ft or 21 ft/mile in a north-northwesterly direction. <br /> Water samples were collected from each well on January 7, 1992, after purging and stabilization <br /> of pH, conductivity, and temperature. Mr. Steve Schneider of the San Joaquin County Public <br /> Health Services was present to witness the sampling. <br /> The samples were collected, preserved and transported under chain of custody and in accordance <br /> with EPA and DHS protocol. The samples were analyzed by RESNA Environmental <br /> Laboratories (DHS cert. #1211) for TPHD and BTEX utilizing EPA methods 3510/8015 and <br /> 8020, respectively. Table 2 summarizes analytical results.' Attachment 1 contains laboratory <br /> data sheets, chain-of-custody documentation, and well purge logs. <br /> The water samples collected from wells MWl, MW2, MW3, and MW4 via dedicated pumps <br /> were not found to contain detectable concentrations of any petroleum hydrocarbon analytes. A <br /> duplicate sample collected with a disposable bailer from MW4 ("MW-4D") was reported to <br /> contain 1.0 parts per billion ethylbenzene. No other analytes were detected. A blind blank <br /> LRO20792.GPS <br />