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4.3.2. Physiographic Setting The Lease area is characterized by shallow, linear valleys which are separated by broad ridges or low hills. Most of the area drains into Yellow Creek; only the southeastern part drains into Ryan Gulch which in turn drains into Piceance Creek. All drainages on the Lease are ephemeral and unnamed. Yellow Creek, which separates the main body of the Lease from the Lease annex, flows throughout most of the year. Elevation of the Lease ranges from about 6,775 feet in Section 16 to about 6,240 feet near Yellow Creek. Total topographic relief is about 535 feet. Steepest topographic slopes occur along the southeastern corner of the property in the headward reaches of Horse Draw. A semiarid climate prevails in the Lease area; annual precipitation usually is less than 15 inches. In response to climate and elevation, the dominant vegetation is pinyon juniper and sagebrush with lesser amounts of grasses and small shrubs. Stands of pinyon-juniper are scattered throughout most of the Lease, separated by broad flats of sagebrush and grasses. The southeast corner of the Lease (Section 25 primarily) has been chained and the pinyon juniper removed. The chained area now contains a higher than average density of various grass species. Wildlife in the Lease area consists of numerous small birds, mammals and reptiles, as well as a sizeable population of migratory mule deer. A small population (less than 30) of wild horses also lives in the general area surrounding and including the Lease. Other larger mammals which have been observed include mountain lions, bobcats, coyote and elk. 4.3.3. Surface Geology The north-central Piceance Creek Basin is dominated by surficial outcrops of Uinta Formation (Figure 4-12). Geologic mapping of the Lease area by Duncan (1976a, Daub & Associates, Inc. Page 4-32 NSI Mine Plan 2010 Rev. Printed: 7/5/2010 Section 4 Geology