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5.1 Groundwater Flow Direction <br /> After installation of the casing and filter pack materials, the depth-to-water was <br /> measured with a decontaminated electronic water level sounder. The field geologist <br /> observed increasing water levels between October 10 and 13, 2011. As a result, the <br /> temporary wells (MW-9A, MW-10A, and MW-11A) were left to equilibrate for one week <br /> before "static" water levels were measured on October 19, 2011. <br /> Groundwater monitoring information is summarized on Table 10: <br /> o to rin g <br /> ' Table 10 <br /> Summary of Groundwater Information from Phase I and II EMP Wells <br /> First Static Groundwater <br /> Well ID Groundwater Groundwater Elevation <br /> (ft) (ft) (ft amsl) <br /> MW-9 88.6 66.4 230.52 <br /> 1 MW-10 75 66.7 219.63 <br /> MW-11 69.5 67.2 216.07 <br /> MW-9A 1 99.9 83.05 215.13 <br /> MW-10A 86.0 74.10 206.95 <br /> MW-11A 43.3 1 43.31 222.41 <br /> Groundwater equipotential contours were developed using October 2011 data for <br /> temporary wells MW-9, MW-10, and MW-11 combined with the third quarter (Summer) <br /> 2011 monitoring data from wells SB-1, MW-4, MW-5, and MW-8. Data for permanent <br /> monitoring wells MW-9A, MW-10A, and MW-11A were collected March 2012 during <br /> well development and sampling. As shown on Figure 3, the equipotential data suggest <br /> the presence of a groundwater flow divide along the northern edge of the landfill. <br /> Groundwater to the south of the divide flows in a southerly direction at a gradient of <br /> 0.05 foot per foot, which is consistent with the historical interpretation of groundwater <br /> movement in the shallow aquifer. To the north of the flow divide, data from the <br /> temporary wells suggest that groundwater flows to the northeast with an apparent <br /> slight convergence along the centerline of Corral Hollow Road. <br /> 5.2 Nature and Extent of Groundwater Impacts <br /> Chlorinated aliphatic compounds; namely, PCE, TCFM, and DCDFM, were detected in <br /> samples from the temporary and permanent monitoring wells. Concentrations ranged <br /> tfrom estimated, trace levels to measured levels below State and Federal Maximum <br /> Contaminant Levels (MCLS). These results are consistent with those found historically in <br /> samples from monitoring wells MW-5 and MW-8. <br /> Isoconcentration contours of DCDFM, TCFM, and total VOCs (Figures 4, 5, and 6, <br /> respectively) were constructed using the temporary monitoring well data, March 28, <br /> EMP Report—Phase II Geo-Log0c Page ■ 18 <br /> 1 Corral Hollow Sanitary Landfill ASS O C I AT E S <br /> August 21,2012 <br />