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3.2.6 Laramie-Fox Hills Aquifer Laboratory Specific Yield Data <br />Thirty Sy values were obtained for this aquifer. The values range from 0.05 to 0.38 with <br />an average value of 0.20 and a median value of 0.21. Senate Bi115 assigned a specific <br />yield value of 0.15 for this aquifer. The average and median values determined by the <br />SPDSS are 33% and 40% higher than the SB-5 values for this aquifer, respectively, <br />indicating there may be more water available in this aquifer for withdrawal than what <br />was determined by SB-5. The limited number of samples compared to the areal extent of <br />the aquifer limits the significance of this finding. An aquifer-wide specific yield <br />distribution trend is not apparent from the data. Specific yield data are presented in <br />Figure 17. <br />3.3 Storage Coefficient Data <br />Aquifer storage coefficient data represent the amount of water that can be obtained from <br />the full thickness of a unit area of a confined aquifer due to a 1 foot decline in water <br />level. This parameter is used in modeling for the confined portions of the Denver Basin <br />bedrock aquifers. The aquifer storage coefficient values of each aquifer were compiled <br />and analyzed for trends in geographic and statistical distribution. Table 6 summarizes <br />the number of data points analyzed, statistical groupings, and the range of values <br />observed by aquifer. No storage coefficient data were found in any data sources or <br />collected by field testing during Phases 1 or 2 for the Upper Dawson, Lower Dawson, <br />and Upper Arapahoe Aquifers. However, previously contoured data from Robson <br />(1983) are presented for these aquifers in Figures 18, 19 and 20, respectively, as well as <br />for the Denver, Lower Arapahoe, and Laramie-Fox Hills, which also have point values <br />of the storage coefficient data described below. <br />3.2.1 Denver Aquifer Storage Coefficient Data <br />Only one point value of 0.0003 is available for the Denver Aquifer. This value is posted <br />along with contours provided in Robson (1983) in Figure 20. The sole point value of <br />0.0003 for the Denver Aquifer generally agrees with the Robson (1983) contoured data. <br />3.2.2 Lower and Undivided Arapahoe Aquifer Storage Coefficient Data <br />Storage coefficient values from 14 data points range from 0.00002 to 0.008 with a median <br />value of 0.0003. Significant variability exists between some neighboring data points but <br />most of the data are within an order of magnitude of each other. The data do not agree <br />very well with those provided by Robson (1983), with some data points being <br />significantly higher and others lower than Robson, but most values are generally in the <br />range expected for a confined aquifer. A possible explanation of why some data points <br />are higher than those reported by Robson (1983) is that the tests may have been <br />conducted in locations where the aquifer has become unconfined or semi-confined due <br />to localized pumping since Robson's data collection effort. These values will be used, <br />with engineering judgment, in groundwater modeling to determine the range of likely <br />values for this parameter in the Lower and Undivided Arapahoe Aquifer. Data point <br />values are presented with contoured data from Robson (1983) in Figure 22. <br />3.2.3 Laramie-Fox Hills Aquifer Storage Coefficient Data <br />Storage coefficient values from 13 data points range from 0.00002 to 0.004 with a median <br />value of 0.0003. Point values are posted with contoured storage coefficient data from <br />SPDSS Phase 2 Task 43.2 TM -Final 24 <br />2/ 13/ 2006 <br />