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G-10 <br /> Above the Pierre Shale is the Fox Hills Sandstone which is composed of medium-to fine-grained <br /> sandstone interbedded with shale. It was deposited in a shallow marine or shore line environment. <br /> The sandstones are often massive and occur in "shingles" that pro-grade from west to east <br /> (Dechesne,M. and others;2011). The shingling morphology often makes it difficult to determine <br /> the contact between the Fox Hills Sandstone and the Pierre Shale since the sand shingles can be <br /> interbedded with the Pierre Shale. Regionally,the Fox Hills Sandstone ranges from 25 to 400 feet <br /> in thickness (Kirkham and Ladwig; 1979); however, locally, it is about 200 feet thick, or less. <br /> (COGCC;2019) <br /> The next unit in ascending stratigraphic order is the Laramie Formation. The unit was deposited in <br /> a delta plain environment and is divided into two distinct parts. The lower part consists of <br /> sandstone, shale, and coal and regionally is from 100 to 300-feet thick. The coals present in the <br /> lower Laramie Formation have been mined in both the Denver and Cheyenne Basins,including at <br /> the nearby (4 miles north) Coors Energy Company's Keenesburg strip mine. The upper part <br /> consists of shale,siltstone,claystone,occasional sandstone,and minor coal. Regionally,the upper <br /> Laramie Formation ranges from 250 to 600 feet thick; however, at the Keenesburg No. 2 Mine <br /> location,the top of the Laramie Formation Coal Zone(in the lower part of the formation)may be <br /> about 200 feet below the surface (Kirkham and Ladwig; 1979). A review of oil and gas well <br /> geophysical logs in the vicinity of the site indicated that the Laramie Formation is either partially <br /> or wholly cased off. Given that,it is estimated that the thickness of the Laramie Formation at the <br /> site may be 300 to 400 feet thick. <br /> With regard to groundwater resources,the Fox Hills Sandstone and Laramie Formation have been <br /> combined into a single hydrogeologic unit, considered a principle aquifer in the Denver Basin <br /> (Wray and Koenig; 2001). Sandstones in both units are considered aquifers and the upper part of <br /> the Laramie Formation is a confining unit. <br /> The D 1 Sequence of the Denver Group is the next unit in succession and,based on mapping,may <br /> be present under the southwest portion of the Keenesburg No. 2 Mine Permit Area. The DI <br /> Sequence contains rocks that have previously been"mapped as the Arapahoe Formation,portions <br /> of the Dawson Arkose, and portions of the Denver Formation". The D1 Sequence generally <br /> consists of sandstone, shale,and minor lignite in eastern areas. At the base of the D 1 Sequence is <br /> a unit informally designated as the Arapahoe Conglomerate which is composed of coarse-grained <br /> material including pebbles and cobbles and in places it is considered an aquifer. However, the <br /> Keenesburg No. 2 Mine_112 Reclamation Operation—November 22, 2019 <br />