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the aquifer materials with increasing distance from the western source area. Specific <br />yield data are presented in Figure 12. <br />3.2.2 Lower and Undivided Dawson Aquifer Laboratory Specific Yield Data <br />Fourteen Sy values were obtained from this aquifer. The values range from 0.04 to 0.27 <br />with an average value of 0.15 and a median value of 0.15. Senate Bi115 assigned a <br />specific yield value of 0.20 for this aquifer. The average and median values determined <br />by the SPDSS are both 25% lower than the SB-5 values for this aquifer. As is the case <br />with the Upper Dawson Aquifer, the Sy values reported by SPDSS indicate there may <br />not be as much water available in this aquifer for withdrawal as determined by SB-5. <br />Specific yield values generally decrease from west to east, consistent with the general <br />concept of increasingly fine grained (clayey) deposits further from the sediment source. <br />Specific yield data are presented in Figure 13. <br />3.2.3 Denver Aquifer Laboratory Specific Yield Data <br />Twenty-six Sy values were obtained from this aquifer. The values range from 0.002 to <br />0.46 with an average value of 0.18 and a median value of 0.14. Senate Bi115 assigned a <br />specific yield value of 0.17 for this aquifer. The average value determined by the SPDSS <br />is six percent higher and the median value is 18% lower than the respective SB-5 values <br />for this aquifer. An aquifer-wide specific yield distribution trend is not apparent from <br />the data, indicating samples may have been obtained from both fine- and coarse-grained <br />sediments throughout the aquifer's extent. Specific yield data are presented in Figure <br />14. <br />3.2.4 Upper Arapahoe Aquifer Laboratory Specific Yield Data <br />Seven Sy values were obtained from this aquifer. The values range from 0.03 to 0.27 <br />with an average value of 0.20 and a median value of 0.23. Senate Bi115 assigned a <br />specific yield value of 0.17 for this aquifer. This difference indicates there may be more <br />water available for withdrawal than what was determined by SB-5. The average and <br />median values determined by the SPDSS are 18% and 35% higher than the SB-5 values <br />for this aquifer, respectively. The limited number of samples and inability to assign four <br />of seven values to either the Upper or Lower Arapahoe Aquifer limits the significance of <br />this finding. An aquifer wide specific yield distribution trend is not apparent from the <br />very sparsely distributed data. Specific yield data are presented in Figure 15. <br />3.2.5 Lower and Undivided Arapahoe Aquifer Laboratory Specific Yield Data <br />Sixteen Sy values were obtained from tests in this aquifer. The values range from 0.06 to <br />0.40 with an average value of 0.19 and a median value of 0.18. Senate Bi115 assigned a <br />specific yield value of 0.17 for this aquifer. The average and median values determined <br />by the SPDSS are 12% and 6% higher than the SB-5 values for this aquifer, respectively. <br />The limited number of samples and inability to assign values from the northern half of <br />the aquifer to either the Upper or Lower Arapahoe Aquifer limits the significance of this <br />finding. An aquifer-wide specific yield distribution trend is not apparent from the data, <br />which are very sparsely distributed across the aquifer's extent. Specific yield data are <br />presented in Figure 16. <br />SPDSS Phase 2 Task 43.2 TM -Final 23 <br />2/ 13/ 2006 <br />