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SNA WATERWORK CORP. <br /> [NDUSTRIES <br /> April 26, 1991e'� + 1) Lw9Yt <br /> MAY 611991 <br /> LINVIROf>;VIENTHL. HEALTH <br /> Ms. Laurie A. Cotulla PEW IT,,SCRVICES <br /> San Joaquin County Public Health Services, <br /> Environmental Health Division f <br /> P.O. Box 2009 <br /> Stockton, CA 9520 . <br /> Re: 1991 Second Quarter Groundwater Monitoring Report, <br /> Genstar Western Stone site, 6181 E. Eleventh St. , <br /> Tracy, CA (county site code: 1393) <br /> Dear Ms. Cotulla: <br /> This letter presents the results of our 1991 second quarter <br /> groundwater monitoring and sampling at the referenced site. <br /> Activities during the quarter included monitoring depth to <br /> groundwater, purging of wells, groundwater sampling, and analysis <br /> of samples for total petroleum hydrocarbons as diesel (TPHD) , <br /> benzene, toluene, ethylbenzene, and xylenes (STEX) . <br /> Groundwater monitoring and sampling was conducted on April 8, <br /> 1991. Depth to groundwater was measured in each well and sub- <br /> tracted from wellhead elevation to determine groundwater eleva- <br /> tion (Table 1) . Water levels in April were found to be essen- <br /> tially the same as when last measured in January 1991. Figure 2 <br /> depicts the groundwater gradient on April 8, 1991 . Gradient <br /> magnitude was essentially unchanged since January 1991, at op- <br /> proximately .005 ft/ft or 26 ft/mile. t r nds ter;° flow direr-tion <br /> wad. alAo unchanged and remains nortl weste . <br /> Water samples were collected from each well on April 8, 1991, <br /> after purging and stabilization of pH, conductivity, and tempera- <br /> ture. The samples were analyzed by Applied Analytical Laborato- <br /> ries (DHS cert. #1211 ) for TPHD and BTEX utilizing EPA methods <br /> 8015 and 8020, respectively. Table 2 summarizes analytical. <br /> results. Attachment 1 contains laboratory data sheets, chain-of- <br /> custody documentation, and well purge logs. <br /> The water sample collected from MW4 was found to contain 1 . 1 <br /> parts per billion (ppb) ethylbenzene. Benzene, toluene, xylenes, <br /> and TPHD were not detected in this sample. No detectable concen- <br /> trations of any analytes were found in the remaining samples. <br /> 1710 MAIN STREET . ESCALON,CA 95326 0 (209)838-3507 <br /> 2350-A WALSH AVENUE s SANTA CLARA,CA 95051 • (408)496-1249 <br />