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velocities is presented in Table 9 below and is based on the minimum and maximum <br /> hydraulic conductivity, minimum and maximum gradient, and minimum and maximum <br /> expected effective porosity. <br /> Table 9 <br /> Calculated Groundwater Flow Velocity Values for the Phase II EMP Wells <br /> Hydraulic <br /> Conductivity Gradient Effective Velocity Velocity <br /> (feet/day) (feet/feet) Porosity (feet/day) (feet/year) <br /> 0.0383 0.045 0.02 0.086175 31.45388 <br /> 0.0119 0.045 0.02 0.026775 9.772875 <br /> 0.0059 0.045 1 0.02 0.013275 4.845375 <br /> 0.0383 0.045 0.25 0.006894 2.51631 <br /> 0.0119 0.045 0.25 0.002142 0.78183 <br /> 0.0059 0.045 0.25 0.001062 0.38763 <br /> Use of an effective porosity of 2 percent is appropriate for portions of the aquifer that <br /> are controlled by fracture flow. Based on the boring logs, there is evidence to suggest <br /> that there are oxidation products on prismatic partings in the more fine-grained <br /> portions of the Corcoran Formation where an effective porosity of 2 percent is <br /> appropriate. Other descriptions in the boring logs suggest that groundwater flow may <br /> be limited to sand lenses in the Corcoran Formation where use of an effective porosity <br /> of 25 percent is probably more appropriate. <br /> 4.4.8 Well Survey <br /> Surveying of Phase II completed monitoring wells was conducted by the County. The <br /> survey of the new wells was tied to the on-site benchmarks and CHSL's existing <br /> groundwater monitoring network. Top of well casing and surrounding ground surface <br /> elevations were surveyed to the nearest 0.01 foot. The horizontal alignment of the well <br /> was surveyed to the nearest 0.1 foot. Survey data for each well are presented on the <br /> ' respective well construction log in Appendix B. <br /> 5.0 NATURE AND EXTENT OF RELEASE <br /> The following sections describe the nature and extent of the release based on the Phase <br /> I and II EMP findings concerning groundwater flow and contaminant distribution that <br /> were developed using field measurements and analytical results from the temporary <br /> and permanent monitoring wells, existing on-site monitoring well data, and well <br /> recovery data. <br /> EMP Report—Phase II Geo-Logic Page ■ 17 <br /> 1 Corral Hollow Sanitary Landfill A S S O C I ATE S <br /> August 21,2012 <br />