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Wm, J. Hunter & Associates 2220 Loma Vista Dr. <br /> Registered Geologists Sacramento, CA 95825 <br /> Petroleum & Mineral Appraisers (916) 972=7941 <br /> R F Co F.IVL <br /> FAX(916) 972-1685 <br /> Lj <br /> April 7, 1997 APR L p 1997 <br /> Steven Sasson, REHS ENVIRO:,,Q►ENTAL_ HEALTH <br /> San Joaquin County PHS PERMIT j SERVICES <br /> Environmental Health Division <br /> 445 No. San Joaquin Street <br /> Stockton, CA 95202 <br /> Ref : Tenth Quarterly Groundwater Monitoring Report for 913 W. <br /> Fremont Street, Stockton. <br /> Dear Mr. Sasson; <br /> We have enclosed a copy of the field report, water analysis <br /> results, and a gradient map for the above property. The work was <br /> performed on March 19, 1997 by Del-Tech Geotechnical Support <br /> Services as directed by our office. <br /> The attached PLATE I shows the direction of the groundwater <br /> gradient indicated by the ten (10) measurements taken to date . <br /> The gradient continues in a northerly direction at about <br /> . 004 ' /ft . <br /> 1 <br /> The water table was measured at an average depth of 8 .59 ' bgs, a <br /> rise of 1 . 65 feet since the November, 1996 sampling event . <br /> The results of the laboratory anayzes of water samples collected <br /> since monitoring began are shown on TABLE I . Monitoring wells ##1 <br /> & ##4 are below detection levels for BTEX & TPHg. MW-2 recorded <br /> significant levels of BTEX & TPHg, but all compounds were below <br /> those measured when the well was last sampled in March, 1996 . <br /> MW-3 , which has essentially been ND in prior sampling events, <br /> measured minor amounts of BTEX & TPHg. <br /> PLATES II through PLATES V1 show the inferred lines of equal <br /> concentrations & limits for benzene, toluene, ethylbenzene, <br /> xylene, & TPHg based upon the results of the latest data & prior <br /> data obtained from the soil probes . Those maps show that the <br /> highest levels of contamination appear to be beneath Stockton <br /> Street, to the north/northeast of the site of the removed UST. <br /> Although the water table is some 7-8 ' above the top of the <br /> screened intervals in MW-1, MW-2 , & MW-3, we cannot justify_ the <br /> placement of additional wells at this site . The limits of the <br /> plumes have been delineated in all directions, and further <br /> investigative work does not appear warranted. <br /> Weare in the process of obtaining estimates for placing ORC <br /> 1 <br />