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The Late Cretaceous Mancos Shale tmderlies the Iles Formation and outcrops southwest of <br />the permit boundary along Sage Creek and the Sage Creek Anticline. 'The IV[ancos Shale <br />is a dark grey marine shale with interbedded sandstones near the toll and interbedded <br />sandstone and limestone near the bottom. <br />Overlying the Mesaverde Group is the Lewis Shale, a homogeneous marine shale with a <br />thickness of between 1000 and 1500 feet. The Lewis Shale is overlain by the: Cretaceous <br />Lance Formation and the Tertiary Fort Union Formation- The ~lasatch Formation of <br />Eocene age unconformably overlies the Fort Union Formation. It is aJmprised primarily <br />of fresh water stream-laid sandstone and shale deposits. Unconsolidlate:d alluvial, terrace, <br />and surflcial deposits of Quaternary age overlie the exposed geologic formations in some <br />areas, particularly along larger streams. <br />The proposed permit area lies structurally between the parallel, souith-southeast trending <br />Sage Creek and Fish Creek anticlines. The axis of the Sage Creek: Anticline is situated <br />about one to two miles west of the western edge of the Yoast permit ara;a: TI•~e axis of the <br />Fish Creek Anticline originates near Scotchman's Draw and extends south-southeasterly <br />dividing the northern first five-year mine block from the neck portion of rthe permit azea. <br />The rock units in the proposed permit area dip predominantly 15 to 20 percent to the north <br />in the north mine block, to the northwest in the neck area, and to the west in the south <br />mine block. More extreme dips of 25 to 35 percent occur locally in the northwest and <br />northeast parts of the north mine block. The rock uniu are appazently unaffected by any <br />significant faulting within the permit area. <br />Surface Water <br />The Yoast Mine drains to Sage Creek on the west side, and to Grassy Creel; on the east <br />side. Sage Creek and Glassy Creek aze perennial tributaries to the Yampa River. Armand <br />Draw and Scotchmans Gulch are intermittent drainages which drain from the northern side <br />of the proposed permit area into Grassy Creek. The Yampa River then flows to the Green <br />River and eventually the Colorado River. Refer to Figure 3 for more detail. <br />Sa¢e Creek <br />Sage Creek is a perennial stream to the west of the proposed permit ;area. ~ Flaws upstream <br />from the proposed permit azea range from an average 0.7 cubic feet per second (cfs) in the <br />spring to neaz 0 in late summer and fall. Approximately two miles downstream from the <br />permit azea, average flows of 1.5, 0.09, and 0.04 cfs were observed. during traseline data <br />collection in the spring, summer, and fall respectively. <br />Water quality in Sage Creek varies from upstream to downstream. iJpstre:am from the <br />permit azea, a CaMgHCCO3 water type predominates. Total dissolved :solids (TDS) <br />typically range from 296 to 510 mg/1 at high and low flows, respectively. Downstream from <br />Yoaat Mine 8 July 6, 1995 <br />