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Cells (100 ft by 100 ft) along the perimeter of the proposed liner were modeled as CCL by assigning them a hydraulic <br />conductivity of 0.003 ft per day (10E-7 cm/sec). Recharge inside the storage vessels was eliminated and the storage <br />vessels were modeled with constant head assigned as the proposed maximum water surfaces. As seen in Figure 13, <br />only slight mounding occurred east of the Site where groundwater levels rose approximately 2 feet and the effect <br />extended to approximately one-quarter of a mille to the east, to a maximum level of 3 feet just east of the Site. Levels <br />greater than 3 feet were encountered through the liner and on Site but had no impact on any structures off-site because <br />groundwater is approximately 25 feet below the existing ground surface. <br />Little decrease (shadow) in groundwater levels on the down gradient (west) side of the Site were modeled due to the <br />north, northwest groundwater gradient and the South Platte River's strong hydrologic connection to the Site, see <br />Appendix B. <br />5.0 SENS/T/VITYANALYSIS <br />5.1 Hydraulic Conductivity <br />A sensitivity analysis was performed on the hydraulic conductivity of the geological unit underlying the site (Broadway <br />Alluvium). The hydraulic conductivities detennined in the calibration process are on the low side of the range of values <br />reported by (Hershey and Schneider, 1989) but the groundwater levels modeled with these hydrologic conductivities <br />provided the most accurate modeled groundwater levels. <br />The hydraulic conductivity values were varied by 40% below and 90% above the assigned values. See Table 10 below <br />reporting the results of the sensitivity analysis. Overall a reduction in the hydraulic conductivity by 40°!° caused the <br />calibrated water levels to increase by and average of 1.25 feet and an increase in hydraulic conductivity by 90% caused <br />the calibrated levels to decrease by an average of 1.0 feet. <br />Table 10 <br />Sensitivity Analysis of <br />Hydraulic Conductivity <br /> <br /> <br />Percent Valley Fill <br />Hydraulic <br />Conductivi <br /> <br />MW1 <br /> <br />MW2 <br /> <br />MW3 <br /> <br />MW4 <br /> <br />MW5 <br /> <br />MW6 <br /> <br />MW7 <br />60% 99.0 4912.7 4911.2 4916.0 4925.4 4927.4 4924.1 4926.0 <br />80% 132.0 4912.2 4911.1 4915.7 4924.0 4926.0 4923.3 4925.3 <br />110% 181.5 4911.6 4911.0 4915.5 4922.7 4924.7 4922.7 4924.8 <br />130°fo 214.5 4911.4 4910.9 4915.3 4922.2 4924.2 4922.4 4924.6 <br />160% 264.0 4911.2 4910.9 4915.2 4921.6 4923.5 4922.1 4924.3 <br />190% 313.5 4911.1 4910.8 4915.1 4921.2 4923.1 4921.8 4924.0 <br />Notes: <br />Modeled groundwater levels reported for each monitoring welt lopfion. <br />Groundwater Model Report - SW TKO Water Storage Project - 10 - February 2005 <br />