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CHAPTER III <br />THE AFFECTED ENVIRONMENT <br />A. General Setting <br />The Yoast Mine is located 13.7 kilometers (8.5 mi) south <br />of Hayden in Routt County, Colorado. The topography of <br />the area consists of broad west and northeast facing <br />moderately sloping benches and ridges. Native rangeland <br />vegetation occurs on 872.5 ha (2,156 ac), and about 35.6 <br />ha (88 ac) are used for grain crops and tame pasture. <br />B. Critical Elements <br />1. Cultural, paleontological, or historic resource <br />values <br />Cultural resource surveys of the proposed permit <br />area have identified 26 cultural resource sites. <br />These sites include five historic sites, eight <br />prehistoric sites, and 13 isolated finds. <br />2. Water quality /supply values <br />a. Surface Water <br />Surface water sources in the proposed permit <br />area include Sage Creek and Grassy Creek, with <br />intermittent flows in Scotchmans Gulch and <br />Annand Draw. The perennial streams have <br />average flows of less than 0.06 m3 /s (2 cfs) , <br />with total dissolved solids (TDS) <br />concentrations of about 300 mg /1 to about 900 <br />mg /l.. <br />b. Ground Water <br />Aquifers in the proposed permit area include <br />the coals and interbedded units of the <br />Williams Fork Formation Middle Coal Group, as <br />well as the overlying Twentymile Sandstone and <br />the underlying Trout Creek Sandstone. Yields <br />from the Middle Coal Group and the Twentymile <br />Sandstone average about 0.038 m3 /min (10 <br />gal /min), with the Trout Creek Sandstone <br />yielding about 0.019 m3 /min (5 gal /min). <br />Water quality in the coal aquifers is <br />characterized by TDS concentrations of about <br />900 to 1,000 mg /l, while TDS concentrations in <br />the interbedded units ranges up to 6400 mg /1. <br />Alluvial aquifers along Sage Creek, Annand <br />C <br />