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Wm. J. Hunter & Associates t 2220 Loma vista Dr. <br /> e r • <br /> Registerec! Geologists Sacramento, CA 95825 <br /> `� � <br /> Petroleurn & Mineral Appraisers - f (916) 972-7941 <br /> 9; 36 FAX (916) 972-1683 <br /> August 25, 1997 <br /> Steven Sasson, REHS <br /> San Joaquin County PHS <br /> Environmental Health Division <br /> 445 No. San Joaquin Street <br /> Stockton, CA 95202 <br /> Ref : Second Quarter 1997 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, a groundwater gradient map, and inferred zero lines for <br /> benzene, toluene, ethylbenzene, xylene, & TPHg for the above <br /> property. The work was performed on June 26, 1997 by Del-Tech <br /> Geotechnical Support Services and witnessed by your office . <br /> The attached PLATE I shows the direction of the groundwater <br /> gradient; indicated by the eleven (11) measurements taken to date . <br /> The gradient continues to be to the north at about 006 ' /ft . <br /> The water table was measured at an average depth <br /> 8 <br /> drop of 0 . 09 feet since the March, 1997 sampling event6bgs, a <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. Levels of all <br /> tested compounds in MW-3 were lower than in the March sampling. <br /> benzene dropped from 0 . 5 ug/L to 0 .4 ug/L; toluene dropped from <br /> 0 . 7 ug/L to ND; ethylbenzene went from 0 . 5 ug/L to 0 . 4 ug/L; <br /> xylene went from 2 . 0 ug/L to 0 . 8 ug/l; and TPH as gasoline <br /> dropped from 52 ug/L to ND . As instructed by EHD personel, MW-2 <br /> was not sampled. <br /> PLATES II through PLATES vI show the inferred plume limits for <br /> benzene, toluene, ethylbenzene, xylene, & .TPHg based upon the <br /> results of the latest analyses & prior data obtained from the <br /> soil probes . The plume appears to be stabilized and has not <br /> migrated measureably since sampling began. <br /> We mentioned in our last report that we were in the process of <br /> obtaining estimates for placing ORC socks in MW-2 to evaluate the <br /> effectiveness of that product . That task has not yet been <br /> completed, but we expect to receive a proposal soon. This <br /> technique has made a significant improvement in the levels of <br /> gasoline contamination at a site in E. Stockton, and should work <br /> 1 <br />