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geophysical log picks for the bottom of the Dawson Aquifer are located in the northern <br />part of the aquifer, and there are fewer picks in the middle of the basin. This surface <br />begins to show the geometry of the structural syncline in the basin as indicated by the <br />U-shape contours near the center of the aquifer. A comparison of the top and bottom <br />elevations of the entire Dawson Aquifer indicates that its thickness ranges up to <br />1,000 feet. <br />Figure 8 presents the net or cumulative sand thickness of the Upper Dawson Aquifer in <br />the divided region. There were 129 database picks with additional control picks used to <br />contour this surface (Table 1). Net sand thickness extends up to 200 feet with an area of <br />relatively large net sand thickness near the western edge of the basin in Township 8S <br />and Ranges 66 and 65W in east-central Douglas County. The net sand thickness lessens <br />almost uniformly from its thickest point to the perimeter of the aquifer. <br />Figure 9 presents the net or cumulative sand thickness of the Lower Dawson Aquifer in <br />the divided region. There were 375 database picks and no additional control picks used <br />to contour this surface (Table 1). Net sand thickness extends up to 200 feet along the <br />western and southwestern boundaries of the divided zone. The sand thickness trend is <br />consistent with the depositional source of these deposits lying to the southwest, with <br />both overall aquifer thickness and the sand thickness decreasing away from the source <br />area. <br />Figure 10 presents the net or cumulative sand thickness of the Dawson aquifer in the <br />divided and undivided regions. In the divided region the net sand thickness represents <br />the sum of the Upper and Lower Dawson sands. A total of 391 database picks and no <br />additional control picks were used to contour this surface (Table 1). There are fewer <br />picks in the central region of the aquifer. Net sand thickness extends beyond 400 feet in <br />the south central region of the aquifer. <br />3.2 Denver Aquifer Configuration <br />Figure 11 presents the top elevation contours of the Denver Aquifer. The footprint of the <br />Denver Aquifer shown in Figure 11 covers an area of approximately 3,260 mil. There <br />were 683 picks with additional control picks used to contour the top elevation of the <br />Denver Aquifer (Table 1). Top elevations range from just over 5,000 feet to 6,700 feet, <br />with the highest elevations at the southern edge of the basin. Most of the geophysical log <br />picks used to contour this surface are located in the center of the aquifer within its <br />subcrop region, and there are fewer picks along the eastern and northern portions of the <br />aquifer in its outcrop region. Therefore, it was necessary to add control picks based on <br />ground surface along the perimeter to define the aquifer outcropping. <br />Figure 12 presents the bottom elevation of the Denver Aquifer. There are 1,153 bottom <br />elevation database picks with additional control picks used to contour the Denver <br />Aquifer (Table 1). The picks are distributed throughout the footprint of the Denver <br />Aquifer, with the highest concentration of picks located in the northern half of the <br />aquifer. Bottom elevations of the Denver Aquifer range from 4,600 to 6,200 feet, with the <br />lowest elevations occurring in the center of the basin in Township 6S, Range 66W. From <br />the lowest elevation the contours rise in elevation very quickly to the west and more <br />SPDSS Phase 2 Task 42.2 TM -Final 15 <br />2/13/06 <br />