2019-05-24_PERMIT FILE - M2019027

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B-2 approximately 4,904 ft. above mean sea level(amsl) in the western half, to a maximum elevation of about 4,912 ft. amsl in the eastern portion.. There is a general slope gradient downward to the north within the confines of the Permit Area; localized elevations range from approximately 4,902 ft. amsl at the western entrance to the Permit Area (with the corresponding elevation along southern extent of the proposed Permit Area ranging from about 4,903 ft. amsl in the western portion(rising to about 4,912 ft. amsl in the eastern portion),while the elevation along the northern extent of the proposed Permit Area is generally consistent at or about 4,894 ft. amsl along its extent. Regional and Localized Geology The site is located in the Denver-Julesburg (D-J) Basin, a tectonic basin that is located in northeast Colorado, southeast Wyoming, and southwest Nebraska. The D-J Basin is bounded on the west by the Colorado Front Range (Dechesne, M. and others; 2011). Areas of the D-J Basin that are adjacent to the Rocky Mountain Front Range have been divided into two sub-basins. The southern sub-basin is the Denver Basin and the northern sub-basin is the Cheyenne Basin. The Denver and Cheyenne Basins are defined by the extent of the Laramie Formation and are separated by a structural feature called the Greeley Arch (Kirkham and Ladwig; 1979). The site is on the northeast flank of the Denver Basin and the sedimentary rock units dip generally to the south and southwest with a gradient of 50 to 100 feet per mile. There are approximately 10,000 feet of Paleozoic to upper Cretaceous sedimentary rocks at the site. The geologic units of concern at the site primarily consist of Pleistocene and Holocene unconsolidated eolian (windblown) deposits: the Tertiary -Upper Cretaceous D 1 Sequence of the Denver Group, and the Upper Cretaceous Laramie Formation. Other relevant Upper Cretaceous units are the Fox Hills Sandstone and the Pierre Shale. The Pierre Shale is a marine deposit that regionally may be up to 8,000 feet. Beneath the subject site, the Pierre Shale is about 6,000 feet thick (COGCC; 2019). The Pierre Shale is important because it is considered to be a low-permeability hydrogeologic confining layer that precludes significant downward movement of groundwater. The top of the Pierre Shale is about 600 feet below ground surface in the immediate area. Keenesburg Project—Limited Impact 110 Application_May 24,2019