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Figure 21 presents the top elevation contours for the Laramie-Fox Hills Aquifer. The <br />Laramie-Fox Hills Aquifer covers a total area of approximately 6,810 mil. A total of 2,272 <br />database picks with additional control picks were used to generate the contours (Table <br />1). Elevations range from 3,700 to 6,000, feet with the highest elevations occurring along <br />the southern edges of the basin. The asymmetric shape of the Denver Basin structural <br />syncline is seen in this figure, where the basin axis is located west of the basin's <br />geographic center as indicated by the low elevations in Townships 5S and 6S and <br />Ranges 66W and 67W. There is a relatively good distribution of picks throughout the <br />aquifer, with a higher number of picks residing in the northern half of the aquifer. As <br />discussed in Section 1.2.6, in the vicinity of Township 4N and Range 60W along the <br />northeastern edge of the aquifer extent, the Task 42.3 base of alluvium data suggests that <br />the Laramie-Fox Hills Aquifer has been eroded away in this area, and therefore, the <br />Laramie-Fox Hills top and bottom contours are identical and equal to the base of the <br />alluvium in this region. <br />Figure 22 presents the aquifer configuration data for the bottom elevation of the <br />Laramie-Fox Hills Aquifer. A total of 2,525 database picks with additional control picks <br />were used to generate the contours (Table 1). Bottom elevations of the Laramie-Fox Hills <br />Aquifer range from 3,500 to 5,800 feet, with the highest elevations observed along the <br />southern edge. The elevations decrease from the outer edges towards the middle with <br />gradual slopes in the eastern half of the basin and relatively steep slopes along the <br />western half. The aquifer's lowest elevation occurs in the west-central portion of the <br />basin, near Denver County's southeast side, and extends south into northeast Douglas <br />County. A comparison of the top and bottom elevations of the Laramie-Fox Hills <br />Aquifer indicates that the thickness of the aquifer extends up to 400 feet. As discussed in <br />Section 1.2.6 and noted above, in the vicinity of Township 4N and Range 60W along the <br />northeastern edge of the aquifer extent, the Task 42.3 base of alluvium data suggests that <br />the Laramie-Fox Hills Aquifer has been eroded away in this area, and therefore, the <br />Laramie-Fox Hills top and bottom contours are identical and equal to the base of the <br />alluvium in this region. <br />Figure 23 depicts the net sand thickness for the Laramie-Fox Hills Aquifer. A total of <br />1,746 database picks with additional control picks were used to contour the surface. The <br />picks are generally clustered in the northern half of the aquifer within Adams, <br />Arapahoe, and Weld Counties; there are no data points along the northern and eastern <br />edges of the basin. Net sand thickness in the aquifer ranges up to 250 feet, and the <br />majority of the thickness in the interior of the aquifer is around 150 feet with isolated <br />pockets of lesser sand thickness spotted throughout. <br />Section 3.5 Aquifer Configuration Cross-sections <br />Cross-sections of the Denver Basin region of the SPDSS were developed to help visualize <br />the configuration of the aquifers. A total of seven cross-sections were developed, two are <br />oriented south to north, and five are oriented west to east, with the lines ofcross-section <br />shown in Figure 24. In each of the cross-sections, the saturated alluvium is indicated in <br />yellow, the Dawson Aquifer is shown in shades of green, the Denver Aquifer in red, the <br />Arapahoe Aquifer in shades of blue and the Laramie-Fox Hills Aquifer in purple. In all <br />cases, the confining units between aquifer layers are shown in grey. The cross-sections <br />SPDSS Phase 2 Task 42.2 TM -Final 18 <br />2/13/06 <br />