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Wm. J. Hunter & Associates 2220 Lorna Vista Dr <br /> Registered Geologists Sacramento, CA 95825 <br /> Petroleum & Mineral AppraisersCs- i� I V 11E�, (916j 972-7941 <br /> y i / <br /> FAX (916 972-1683 <br /> APR 1997 <br /> April 7 , 1997 <br /> ENVIRONMENTAL HEALTH <br /> Ron Rowe, Sr RENS PERMIT / SERVICES <br /> San Joaquin County PHS <br /> Envrironmental Health Division <br /> P O. Box 388 <br /> Stockton, CA 95201-0388 <br /> Ref : First Quarter 1997 Groundwater Monitoring report for 1211 <br /> South Turnpike Road, Stockton, Site Code 1788 <br /> we are enclosing a copy of the field report, laboratory results <br /> of water analyses, and maps showing the hydraulic gradient and <br /> lines of equal concentrations of benzene, ethylbenzene, toluene, <br /> xylene, and TPHg based on the latest data The field work was <br /> conducted on March 19, 1997 by Del-Tech Geotechnical Support <br /> Services as directed by our office <br /> The attached PLATE I shows the hydraulic gradient based on the <br /> latest sampling event , it continues to be to the northeast . The <br /> five monitoring events to date show that the gradient has <br /> remained quite constant since monitoring began. The gradient <br /> •, continues to be very low, at about 0033 ' /ft <br /> The results of water analyses taken since monitoring began are <br /> summarized on TABLE I . MW-1, although upgradient from the site <br /> of the removed UST, continues to record the highest levels of <br /> benzene, toluene, xylene, & TPHg MW-3 showed slightly higher <br /> levels of ethylbenzene (299 vs . 251 in MW-1 ) Levels of all <br /> compounds in MW-1 were significantly lower than measured in <br /> September MW-2 showed a slight increase in levels of benzene & <br /> TPHg; others were lower BTEX in MW-3 was down significantly; <br /> TPHg increased from 4 . 1 mq/L in September to 8 47 mq/L in March <br /> MTBE was not tested; it was ND in all three wells in September <br /> PLATES II thru VI show lines of equal concentrations of BETX & <br /> TPHg based on the April sampling event Levels of all tested <br /> compounds increase upgradient in a southerly direction The <br /> reason for this anomalous situation is not known at this time . <br /> Perhaps additional monitoring events will clarify the situation. <br /> Quarterly m nitoring will continue until further notice, the next <br /> sam 1 nt w 11 be due in June <br /> LON <br /> Wm. unter & Associates <br /> c c . R QCB <br /> r Pump nLIAPJI j HUMER <br /> 1 KQ 860 <br /> *��q� <br /> OFC <br />