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Wm. J. Hunter & Associates 2220 Lorna Vista Dr <br /> Registered Geologists ? ,d I'Cr Ulj Sacramento, CA 95825 <br /> Petroleum & Mineral Appraisers (916) 972-7941 <br /> FAX (916) 972-1683 <br /> July 11, 1994 <br /> Michael Collins, RENS <br /> San Joaquin County PHS <br /> Environmental Health Division <br /> 445 No. San Joaquin Street <br /> Stockton, CA 95202 <br /> Ref: THIRD QUARgRLY G2-ODNDWATER MONITORING REMBT- <br /> 1500 Shaw Road, Stockton, CA, (Site Code 1727) <br /> Dear Michael; <br /> We are enclosing the results of the third quarterly report <br /> covering groundwater monitoring activities at the above site, <br /> which were performed on April 21 , 1994- Copies of the field <br /> logs, water measurement data, chain of custody and laboratory <br /> reports are included. The results of all of the laboratory <br /> results taken since monitoring began are summarized on TABLE 1 <br /> for your convenience. <br /> This is the fourth sampling and testing since completion of the <br /> . four monitoring wells in May, 1993, comments concerning the <br /> project are listed below for your information. <br /> 1 . The water table has risen an average of 4. 40 ' since January <br /> of this year. That is the highest level since measurements began <br /> in June, 1993- <br /> 2. The hydraulic gradient has been quite consistently to the <br /> south; refer to F <br /> jHIBIT A for details. <br /> 3. A comprehensive analaysis of amounts of BTEX & TPH-G measured <br /> in the four wells since initiation of the project generally sup- <br /> ports the gradient data obtained- MW-3, which is located in a <br /> downgradient position, (based on water level measurements, ) has <br /> recorded the highest levels of benzene in all four samples, and <br /> the highest levels of TPH--G, ethylbenzene & xylene in 3 of the 4 <br /> samples taken. Toluene was measured highest in that well in 2 of <br /> the 4 samples. <br /> 4. Although there appears to be a general decrease in the amount <br /> of toluene, ethylbenzene & xylene over the last 3 sampling <br /> Periods, benzene & gasoline levels have varied considerably and <br /> do not show an obvious pattern of reduction. <br /> 5. A preliminary attempt to define the existing plume indicates <br /> the possibility of an offsite source to the north. However, the <br /> • data collected to date is insufficient to confirm that evidence. <br /> 1 <br />