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Wm. J. Hunter & Associates }_t,VIRO:ti,'; 3y? A L t;F_,g?M Loma Vista Dr <br /> Registered Geologists t'11-It`I VVIS6cramento, CA 95825 <br /> etroleum& Mineral Appraisers (916) 972.7941 <br /> '33 Qu_ 25 PPI 2' r8X (916) 972-1683 <br /> October 15, 1993 <br /> Michael Collins, REHS <br /> San Joaquin County Health Department <br /> Environmental Health Division <br /> 445 North San Joaquin Street <br /> Stockton, Ca 95202 <br /> Ref= Quarterly Groundwater Monitoring Report for 814 E Charter <br /> Way. Stockton - Site Code 1061 <br /> i <br /> Dear Michael; <br /> I am enclosing a copy of the field report, water analysis, and <br /> gradient map for the above property. The work was performed on <br /> October 3, 1993 by Del-Tech Geotechnical Support Services as <br /> directed by my office. <br /> The attached map shows the gradients as measured in October, <br /> 1992, (the first one taken after the monitoring wells were <br /> placed, ) plus the three taken in March, June, & October, 1993. <br /> All three measurements indicate a rather consistant northeasterly <br /> gradient_ <br /> It is interesting to note the differences in levels of contami- <br /> nation measured in the 3 wells between. last October and the <br /> current work; they are summarized below for your information. <br /> MW-1 MW-2 MW-3 <br /> Results in ug/L <br /> 10/92 3/93 6/93 10/93 10/92 3/93 6/93 10/93 10/92 3/93 6/93 10/93 <br /> B ND ND ND ND 7 .0 3.0 ND 38 19.0 17.0 13.0 15 <br /> T ND ND 0. 9 2. 3 1 . 6 1 . 9 0. 7 17 ND 7 4 7 0 6. 2 <br /> E ND ND ND 0 .6 ND 0 - 3 ND 11 ND 0 . 7 0 . 7 3.0 <br /> X ND ND 0. 4 1. 2 ND 1 .0 0. 4 19 ND 1 . 3 1 3 2. 8 <br /> TPHG 60 200 ND 81 470 500 ND 531 550 1200 110 390 <br /> The hydraulic gradient has remained quite stable since first mea- <br /> surements were taken last October. As shown on EXHIBIT A, it is <br /> to the east/northeast. Based on the data, monitoring well #2 is <br /> downgradient from both the site of the removed UST' s and the pump <br /> island. Wells #1 & #3 are essentially on strike, (parallel, ) <br /> with the gradient, and a considerable distance from the DST site_ <br /> Therefore, if the source of the groundwater contamination were <br /> the UST' s on the property, MW #2 should be measuring the highest <br /> levels of pollutants. Prior to the latest sampling, well #3 had <br /> recorded higher levels of all components than either wells #1 or <br /> #2. The latest laboratory results show that MW #2 had the <br /> highest levels; this may be due to fluctuations in the gradient <br /> that occurred between measurements, or to activity that may have <br /> 1 <br />