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3.1.1 Upper Dawson Aquifer Hydraulic Conductivity Data <br />A total of 297 K values were obtained from the Upper Dawson Aquifer. The K values <br />range from 0.02 to 32 ft/day with a median value of 1.4 ft/day. The K data are presented <br />in Figure 6 and summarized statistically in Table 4. <br />As shown in Figure 6, the K data show a relatively high degree of variability within <br />small areas and do not show any significant spatial trends. In general the K values from <br />the Upper Dawson Aquifer exhibit significant heterogeneity; this is to be expected from <br />the low-gradient stream and swamp environments thought to have existed during the <br />time when these aquifer sediments were deposited (Romero, 1976). <br />3.1.2 Lower and Undivided Dawson Aquifer Hydraulic Conductivity Data <br />A total of 530 K values were obtained from the Lower Dawson Aquifer, the largest <br />number of data points and the highest concentration of data available for any of the <br />bedrock aquifers. The K values range from 0.01 to 191 ft/day, with a larger range than <br />the Upper Dawson, but with a much lower median value of 0.9 ft/day. The K data are <br />presented in Figure 7 and summarized statistically in Table 4. <br />As shown in Figure 7, there is reasonable consistency in the results for pumping and <br />specific capacity tests. This is not unexpected since there is better data control on the <br />aquifer tops and bottoms (for calculation of net sand thickness) and because these <br />aquifers are predominantly under confined conditions. The specific capacity analysis <br />method better fits the aquifer conditions. The K values are generally higher in the <br />northern half of the aquifer, except for an area northeast of Castle Rock, and they <br />decrease to the south. The lowest values are in northern El Paso County, as depicted by <br />both aquifer pumping tests and specific capacity results. The lower values are likely due <br />to a decrease in grain size of the aquifer materials in this part of the aquifer. In general <br />the K values from the Lower Dawson Aquifer exhibit significant heterogeneity, however <br />a trend of higher values north of El Paso County is observable. <br />3.1.3 Denver Aquifer Hydraulic Conductivity Data <br />A total of 341 K values were obtained from the Denver Aquifer. The K values range <br />from 0.0001 to 989 ft/day, with the minimum and maximum data obtained from lab <br />tests; the median value of all data types is 0.6 ft/day. The K data are presented in Figure <br />8 and summarized statistically in Table 4. <br />As shown in Figure 8, there is a good spatial distribution of the data, except for <br />southwest Elbert County. The data show considerable spatial variability, which could <br />indicate the highly variable nature of the low gradient stream and swamp environments <br />thought to have existed during the time when this aquifer was deposited (Romero, <br />1976). The slightly higher values along the west central portion of the aquifer, in <br />Townships 5 and 6 South, Ranges 66 to 68 West, north and west of Parker, likely indicate <br />the sediments have less fine grained sediment such as silt and clay, and thus could <br />indicate the presence of a higher energy depositional environment. <br />Relatively lower values are present in the north central part of the aquifer, suggesting <br />less coarse- and more fine-grained material deposited in a low energy environment such <br />SPDSS Phase 2 Task 43.2 TM -Final 20 <br />2/ 13/ 2006 <br />