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ridges that are deeply incised, and barren, brush covered, southwestward facing cliffs where <br /> more resistant sandstone outcrops exist. The long, sloping landforms of these areas coincide <br /> with the strike and dip of the underlying bedrock. The permit area is dissected by several small, <br /> ephemeral drainages flowing into two principal stream systems: Sage Creek on the southwest <br /> and Grassy Creek on the southeast. A detailed discussion of the Yoast Mine surface water <br /> system is presented in Tabs 7 and 16 of the permit application package (PAP). <br /> The Yoast permit area is in the Williams Fork Mountains. The coal seams mined <br /> comprised the Wadge and the Wolf Creek. These seams are contained within the Middle <br /> Coal Group, an interval of interbedded sandstones, sandy shales, shales and coal within the <br /> Williams Fork Formation. Above the Middle Coal Group is the Twentymile Sandstone, a <br /> 100-200 foot thick fine-grained, massive sandstone, a prominent formation visible <br /> throughout the Yampa River Valley. The upper unit of the Williams Fork Formation <br /> contains the Upper Coal Group of the Mesaverde group, and consists of layers of <br /> sandstone, sandy shale, shale and coal. The thickness units vary from approximately 200 to <br /> 850 feet throughout the region. <br /> Surface Water <br /> The Yoast Mine drains to Sage Creek on the west side and to Grassy Creek on the east side. <br /> Sage Creek and Grassy Creek are perennial tributaries to the Yampa River. Annand Draw and <br /> Scotchman's Gulch are intermittent drainages which drain from the northern side of the permit <br /> area into Grassy Creek. The Yampa River then flows to the Green River and eventually to the <br /> Colorado River. <br /> Sage Creek <br /> Sage Creek is a perennial stream to the west of the permit area. Water quality in Sage Creek <br /> varies from upstream to downstream. Baseline data indicate a predominantly CaMgHCO3 water <br /> type upstream from the permit area. Total dissolved solids (TDS) typically ranged from 296 to <br /> 510 mg/1 at high and low flows, respectively. A CaMgSO4HCO3 water type predominated <br /> downstream from the permit area, and TDS typically ranged from 526 to 695 mg/1 at high and <br /> low flows, respectively. Most of the flow in Sage Creek is diverted out of the stream for <br /> irrigation purposes prior to reaching the site where downstream baseline data was collected. <br /> Sage Creek water is also utilized for livestock watering. <br /> Grassy Creek <br /> Grassy Creek is a perennial stream to the east of the permit area. A CaMgSO4HCO3 water type <br /> predominates upstream from the permit area. TDS ranges from 680 to 853 mg/1 at high and low <br /> flows, respectively. <br /> Permit Area <br /> Intermittent flows from the northern side of the permit area drain through Annand Draw into <br /> Scotchman's Gulch and then into Grassy Creek. Spring flows in Annand Draw are <br /> predominantly from the melting of snowpack. Late spring to early summer flows are a <br /> combination of bank storage, runoff from precipitation events over saturated or frozen ground, or <br /> perched spring flow recharged by snowmelt. The remainder of the year, the channel exhibits <br /> ephemeral flow characteristics <br /> 5 <br />