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Mr. Kyle Christie <br /> May 25, [989 <br /> Page 7 <br /> No BETX were identified in groundwater in any off-site monitoring well. <br /> BETX concentrations in groundwater from monitoring well W-2 are. considera!,ly greater <br /> than from monitoring well W-2A. These two wells are 5 feet apart (see Figure 1) and are <br /> ! accessible to groundwater near the surface of the aquifer (see Figure 2). The screened <br /> I -w interval of monitoring well W-2 extends about 15 feet above and 5 feet below the screened <br /> i interval in monitoring well W-2A. <br /> f <br /> Conclusions <br /> BETX concentrations in groundwater in on-site monitoring wells screened across the water <br /> table are in the same range as the BETX concentrations in groundwater wells in January <br /> 1 1989. The approximate 2-foot rise in the water table since January 1989, does not seem to <br /> have significantly affected BETX concentrations. <br /> BETX was not identified in the 74- to 88-foot depth interval. <br /> 1 No BETX were identified in any off-site monitoring wells. <br /> I The fact that BETX concentrations were considerably greater in monitoring well W-2 than <br /> in monitoring well W-2A suggests that hydrocarbons have more ready access into <br /> f1 monitoring well W-2. This access is probably from the vadose zone accessible to the <br /> screened interval of monitoring . well W-2, which is above the screened interval of <br /> monitoring well W-2A. <br /> The majority of hydrocarbons appear to remain pooled beneath the site near the water table <br /> and in the vadose and capillary fringe zones. The rate of vertical. and lateral dispersion in <br /> j groundwater appears to be slow. <br /> Should you have any questions regarding this report, please contact me or Ms. Jeanne <br /> Wallberg at (916) 444-0123. <br /> Verytruly yours,' <br /> BROWN AND CALDWELL <br /> Lawrence E. Phillips <br /> Project Manager <br /> 47 6W <br /> LEP.JSW:mkw <br /> cc/enc: Mr. Gordon' Boggs, California Regional .Water Quality Consol Board, Sacramento <br /> . Ms. Laurie Cotulia, San Joaquin Local Health District, Stockton <br /> Mr. Chris Winsor, ARCO Products Company, Los Angeles <br /> r 3 <br /> "! BROWN AND CALDWELL <br /> 723 S STREET SACRAMENTO.CA 95814-19181444-0123 - <br />