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^ The bottom elevation contours of the Laramie-Fox Hills Aquifer highlight the <br />overall structure of the basin, which is an asymmetrical syncline that trends <br />slightly northwest and is plunging to the north. The deepest portion of the basin <br />is located in Townships 5S, 6S, and Range 66W with a minimum elevation of <br />approximately 3,400 feet. <br />^ The aquifer configuration database as presented in this TM is sufficient to <br />develop contoured surfaces for the aquifer top, bottom, and net sand thickness <br />(which includes the total thickness of sandstone and siltstone lithologies) for all <br />of the Denver Basin bedrock aquifers for the purposes of commencing regional- <br />scale water resources planning and groundwater modeling. <br />^ The nomenclature of the aquifer top, bottom, and net sand thickness picks in <br />HydroBase for the Dawson and Arapahoe Aquifers is complicated. Because of <br />duplicate picks and the complicated nomenclature, detailed spatial and attribute <br />queries are required to select picks for the various surfaces. <br />^ Most of the bedrock aquifers contain a higher density of data in their northern <br />portions and the resulting contoured surfaces are more accurate in these areas. <br />However, picks exist in sufficient density in the southern regions to have <br />confidence in the accuracy of the contours in those regions. <br />In the outcrop or subcrop regions for each aquifer, the density of picks is not <br />sufficient to accurately depict the paleochannels that have been carved into the <br />bedrock surfaces and prevent the top surfaces from exceeding ground surface in <br />some locations. The paleochannels presented as the bottom of alluvium in the <br />Task 42.3 South Platte Alluvium Region TM were used to modify the bedrock <br />surfaces for this TM. Likewise, the USGS 30 meter NED was used to constrain <br />the top surfaces to not be greater than ground surface. <br />Bedrock aquifer bottom elevation contours developed as part of this TM were <br />compared to existing Senate Bi115 (SB-5) layer bottoms. Overall, the bottom <br />elevation contours presented in this TM match the SB-5 bottom elevations <br />contours, and the current contours show added detail in localized areas due to <br />the presence of data that were not available when the SB-5 maps were <br />developed. <br />^ The SB-5 Denver Basin Atlas plates contoured the top of the aquifer surfaces to <br />the extent of the overlying confining unit. However, for this TM, the top surface <br />has been contoured to the extent of the base of the aquifer so that the upper limit <br />of the aquifer is defined over its full areal extent. <br />^ A series of cross-sections were prepared to show the aquifer configuration in <br />slices oriented both south-north and west-east. These cross-sections show the <br />asymmetric nature of the Denver Basin Aquifers and the relatively large <br />thickness of the confining layers that exist between some of the aquifers. <br />SPDSS Phase 2 Task 42.2 TM -Final 21 <br />2/13/06 <br />