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RESNA WATERWORK ORK CORP. <br /> IRK , INDUSTRIES <br /> January 30, 1991 <br /> Ms. Diane Hinson _ <br /> San Joaquin County Public Health Services, <br /> Environmental Health Division <br /> P.O. Box 2009 <br /> Stockton CA 95201 <br /> Re: 9 <br /> 1 91 First o. <br /> uarter Groundwater MonitoringRe r •'. , <br /> Q <br /> Pt <br /> Genstar Western Stone site, 8181 E. Eleventh St. , <br /> Tracy, CA ( County site code: 1393 ) <br /> Dear Ms. Hinson: <br /> i <br /> This letter presents the results of our 1991 first quarter <br /> groundwater monitoring and sampling at Lhe 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 (BTEX) . <br /> Groundwater monitoring and sampling was conducted on January 14, <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 January-,were found to be an <br /> average of .34 feet higher than when last measured in October, <br /> 1990. Figure 1 depicts the groundwater gradient on January 14, <br /> 1991. Gradient magnitude was unchanged since October, 1990 at <br /> approximately .004 ft/ft or 21 ft/mile. Groundwater flow direc- <br /> tion was also unchanged and remains northwesterly. <br /> Water samples were collected from each well on January 14, 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 1 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 MW1 was found to contain 0.7 <br /> parts per billion (ppb) toluene and 1 . 7 pp , total xylenes . <br /> Benzene, ethylbenzene, and TPHD were not detected in this sample. <br /> No detectable concentrations of any analytes were found in the <br /> remaining samples. <br /> 1'710 MAIN STREET . ESCALON,CA 95320 . (209)838-3507 <br /> 4249 <br /> 2350-A WALSH AVENUE • SANTA CLARA,CA 95051 • (408)496 <br />