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March 10, 1997 �� <br /> of ACV APR 0 7 1997 <br /> Michael Infurna, Sr. REHS CES� FNVIRONMENTAL HEALTH <br /> San Joaquin County PHS PERMITISERVICES <br /> Environmental Health Division <br /> P O Box 388 <br /> Stockton, CA 95201-0388 <br /> Re Twelfth Quarterly Groundwater Morutoring Report, 1500 Shaw Road, Stockton, CA; Site <br /> Code 1727, AES Protect No. 145-94009-01 <br /> Dear Mr Infurna- <br /> This report summarizes the monitoring and sampling event conducted on December 3, <br /> 1996 Field activities at the above referenced Canteen facility included monitoring and sampling <br /> of the eight monitor wells onsite (MW-1, MW-2, MW-3, MW-3A, MW-4, MW-5, MW-6, Nfw- <br /> 7) and the four offsite monitor wells (MW-8, MW-9, MW-10, and MW-11) on the U S. Chemical <br /> property <br /> Based on the groundwater elevations from the monitor wells, the groundwater gradient was <br /> S' 0 16 feet per 100 feet and the general du-action of groundwater flow was to the south Fluid level <br /> measurements for this event and historical events are summarized in Table 1 and the <br /> Potentiometnc Surface map is included as Figure 1. Copies of the field data sheets and water <br /> measurement data are included in Appendix A <br /> Free product was not detected in any of the monitor wells, nor has it ever been. <br /> The groundwater elevation was approximately four feet lower during this monitonng event <br /> than during the previous gauging (07123196) The four offsite monitor wells (MW-8 through <br /> MW-11), which were contoured with the Canteen monitor wells, were consistent with the <br /> established groundwater flow and gradient. In addition, five feet of oxygen release compound <br /> (ORC) was installed in monitor well MW-2 and 15' of ORC was installed in monitor well MW-3 <br /> during this monitoring and sampling event <br /> Benzene, toluene, ethylbenzene, total xylenes (BTEX) and TPH-G concentrations <br /> continued to decrease in all of the monitor wells Benzene concentrations were below detection <br /> hrmts in monitor wells MW-1 and MW-4 through MW-11 The maximum benzene concentration <br /> was 44ugIL in momtor well MW-10 TPH-G concentrations were below method detection limits <br /> in all of the monitor wells with the exception of monitor wells MW-3, MW-3A, and MW-10 <br /> which had concentrations of 1,370 ug/L, 444 ug/L, and 1,020 uglL, respectively <br /> 2833 Tnnrty Square, Suite 149 o Carrollton, Texas 75006 e Tel (972) 416-7171 o Fax (972) 416-7175 <br />