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B-3 <br /> Above the Pierre Shale is the Fox Hills Sandstone which is composed of medium-to fine-grained sandstone <br /> interbedded with shale. It was deposited in a shallow marine or shore line environment. The sandstones <br /> are often massive and occur in"shingles"that pro-grade from west to east(Dechesne,M.and others;2011). <br /> The shingling morphology often makes it difficult to determine the contact between the Fox Hills Sandstone <br /> and the Pierre Shale since the sand shingles can be interbedded with the Pierre Shale. Regionally,the Fox <br /> Hills Sandstone ranges from 25 to 400 feet(Kirkham and Ladwig; 1979). Locally,it is about 200 feet thick <br /> or less (COGCC; 2019). <br /> The next unit in ascending stratigraphic order is the Laramie Formation. The unit was deposited in a delta <br /> plain environment and is divided into two distinct parts. The lower part consists of sandstone, shale, and <br /> coal and regionally is from 100 to 300-feet thick. The coals present in the lower Laramie Formation have <br /> been mined in both the Denver and Cheyenne Basins,including at the nearby(4 miles north)Coors Energy <br /> Company's Keenesburg strip mine. The upper part consists of shale, siltstone, claystone, occasional <br /> sandstone, and minor coal. Regionally, the upper Laramie Formation ranges from 250 to 600 feet thick. <br /> At the site, the top of the Laramie Formation Coal Zone in the lower part of the formation may be about <br /> 200 feet below the surface(Kirkham and Ladwig; 1979). A review of oil and gas well geophysical logs in <br /> the vicinity of the site indicated that the Laramie Formation is either partially or wholly cased off. Given <br /> that, it is estimated that the thickness of the Laramie Formation at the site may be 300 to 400 feet thick. <br /> With regard to groundwater resources,the Fox Hills Sandstone and Laramie Formation have been combined <br /> into a single hydrogeologic unit, considered a principle aquifer in the Denver Basin (Wray and Koenig; <br /> 2001). Sandstones in both units are considered aquifers and the upper part of the Laramie Formation is a <br /> confining unit. <br /> The D 1 Sequence of the Denver Group is the next unit in succession and may be present under the southwest <br /> portion of the site,based on mapping. The D 1 Sequence contains rocks that have previously been"mapped <br /> as the Arapahoe Formation, portions of the Dawson Arkose, and portions of the Denver Formation". The <br /> D 1 Sequence generally consists of sandstone, shale, and minor lignite in eastern areas. At the base of the <br /> D 1 Sequence is a unit informally designated as the Arapahoe Conglomerate which is composed of coarse- <br /> grained material including pebbles and cobbles and in places is considered an aquifer. The conglomerate <br /> is limited in extent and may not be present at the site. The D1 Sequence may reach zero thickness in the <br /> southwest part of the site (Deschesne, M.,et al; 2011). <br /> Keenesburg Project—Limited Impact 110 Application_May 24,2019 <br />