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MMW� <br /> wc_a,.r�+n <br /> �, � -,_- 5c•.n- rack+e^s�-•,,` e "d �,m:. <br /> t <br /> Mr. Kyle Christie L <br /> November 8, 1988 <br /> Page 7 <br /> analyzed for TPH by EPA Method 8015 identified low levels of TPH. 'Hae laboratory <br /> results are in Exhibit F. Drill cuttings were stored on site in 55-gallon drums pending <br /> laboratory analyses of the composite samples, and later disposed of at a Class ill landfill. <br /> 13TX concentrations in groundwater samples collected in June 1988 from wells W-2, W-2A, <br /> and W-213 are summarized in Table 2. June 1988 benzene concentrations for these three <br /> monitoring wells are also shown on Figure 1. June 1988 benzene concentrations in <br /> monitoring well W-2 confirm the decreasing trend previously identified in that well. June <br /> 1988 BT_X_ concentrations in monitoring well W-2A are significantly lower than June 1988 <br /> BTX concentrations in monitoring well W-2. In addition, unlike monitoring well W-2, no <br /> free product has accumulated in monitoring well W-2A since its constriction. It is thought <br /> that the source of the product is in the vadose zone. It is possible that the construction of <br /> 4 monitoring well W-2 provides access to hydrocarbons through permeable sand layers in the <br /> vadose zone, while the construction of monitoring well W-2A does not provide such <br /> !' access. Figure 3 shows the construction of monitoring wells W-2, W-2A, and W-213, and <br /> a the subsurface lithology of the monitoring well W-2 area. The two major vadose zone <br /> sand layers shown on Figure 3 are labeled sand zone A and sand zone B. The <br /> gravel <br /> pack of monitoring well W-2 intercepts sand zone B and possibly a small Dart of sand <br /> R ;-1 zone A (see Figure 3). The gravel pack of monitoring well W-2A possibly intercepts a <br /> ti small part of sand zone B. <br /> f( Fable 2. Analytical Results--Groundwater, June 1988 <br /> 'P4 Concentrations, ug/1 <br /> Well number Benzene ' <br /> Toluene <br /> Xylene <br /> � Action level 0.7a I()Oa a <br /> 620 <br /> { <br /> Fr= t W-2 3,570 <br /> W-2A 3,900 3,000 <br /> 437 937 672 <br /> f, W-2B <br /> 410 <br /> � 290 347 <br /> aDrinking water action levels recommended by California Department of Health <br /> Services, January 1987. <br /> Water_l;vel_ <br /> measurements-(Exhibit-B)-in-monitoring-wells-W=2-and-W-2A do not show the <br /> # _ ° same elevation of groundwater in these wells. Bath wells are screened across.the:water <br /> t table (see Figure 3). The average variation, however, is only 0.002 feet, which. is not <br /> significant. <br /> It 4 <br /> BROWN AND CALDWELL <br /> 723 S STREET' - - - - <br /> � q;- SA�R+4MENTQ CwI.;iORN1A 85Bi1•T092•i9F61444.0123 - <br />