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characteristics of the Iles Formation can be described. The Iles <br />J~'• Formation is continuous and can be correlated over a large area. <br />Trout Creek Sandstone, the upper member of the Iles Formation, has <br />been mapped to be 75 feet thick. This sandstone is easily <br />recognized and is considered a marker bed for the top of the Iles <br />formation. Trout Creek Sandstone is a white, fine-grained and well <br />sorted sandstone. It is fairly uniform in thickness in the general <br />area. <br />Beneath the Iles Formation lies the Mancos Shale. The Mancos Shale <br />is a marine shale with thin interbeds of siltstones and limestones <br />and is estimated to be over 5,000 feet thick in this area. This <br />shale forms the base of the regional groundwater system in the <br />area. These shales are relatively impermeable and do not store or <br />transmit appreciable quantities of groundwater. The Mancos Shale <br />is exposed north of the permit area and is found at depth beneath <br />the permit site. <br />The permit area straddles the southern limb of the Collum Syncline. <br />The syncline is a regional structure trending in a southeast- <br />northwest direction parallel to the major geologic structure of the <br />area in the Axial Basin. The Williams Fork and the Iles Formations <br />are truncated north of the permit area and the Mancos Shale is <br />exposed as a result of the regional geologic structure. <br />Goodspring, Taylor and Wilson Creeks are tributaries to the Yampa <br />River, a major surface water feature located some distance from the <br />mine property. Water resources on the mine property are connected <br />to the Yampa River only by surface water discharge and then only <br />during periods of infrequent snowmelts and thunderstorm events. A <br />second major surface water feature in the area is the Williams Fork <br />River. However, the Williams Fork River, which is a tributary to <br />the Yampa River, does not receive discharge from Wilson, Goodspring <br />or Taylor Creeks. Instead, the Williams Fork flows into the Yampa <br />River near the town of Hamilton. This location is far above the <br />confluence of the Yampa River with Milk Creek, the immediate <br />receiving system of water from Goodspring, Wilson and Taylor <br />Creeks. <br />:~ <br />:. <br />2.04.7-2 <br />