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~~; r. 4 ' state boundary, extending approximately 40 miles from the Sangrede Cristo Range to Raton Mesa. The Plateau is underlain by the Raton formation, composed of late Cretaceous through early Tertiary sandstone, siltstone, and coal-bearing shale (Gleichman 198.3) . ` Soils in the project area are generally loamy (wood and Bair 1980). The Table Mountain Loam occurs on level to nearly level (0-3 percent) stream terraces and varies in depth between 20 and 40 inches. The Fort Collins Very Fine Sandy Loam is found on upland draiages with gentle (3-9 percent) slopes. It grades from a very fine sandy loam to loam within the top 8 inches; a blocky clay loam subsoil extends to 38 inches; and the underlying .. material is loam or light clay loam. The Louviers-Travessilla Channery Loam occurs on moderate to steep (30-70 percent) slopes. They are shallow and directly underlain by interbedded sandstones, siltstones, and shales. • The' Purgatoire River is the major drainage in the Colorado portion o~f the Park Plateau. The river heads in the Culebra ~`. Range as three separate drainages the North, Middle, and South Forks. The North and Middle Forks come together at Vigil, near the western edge of the mine boundary, and the South Fork joins the main watercourse at Weston. The Purgatoire then flows eastward within a relatively wide valley (locally referred to as the Picketwire valley) for approximately 30-35 miles. At Trinidad, it flows to the northeast for a short distance, turns once again to the northeast, an orientation it maintains until it joins the Arkansas River at Las Animas. The project area is drained by a small number of small intermittent drainages, most ~;: of which flow south or east into the Purqatoire. The named drainages include Gold Canyon, Lopez Canyon, Sawmill Canyon, and ~ Cherry Canyon. Describing climatic conditions for the project area is difficult, as no meteorological stations are located nearby. The nearest station is in Trinidad, approximately 10-15 miles east. The climate there can be classified as semiarid (Noy-Meir 1973). The growing season, the number of frost-free days, is approximately I 160 days (USDA 1941). Elevations in the project area varies from 7,200 feet to about 7,840 feet, over 1,000 feet higher than in Trinidad. Climatic conditions in the upper Purgatoire. Valley differ somewhat from Trinidad. Generally, these higher elevations are cooler, wetter, and have a shorter frost-free period (Lutz and Hunt 1972). Summer rainstorms occur with remarkable regularity and provide much of the annual precipitation; this rainfall is augmented by winter snowfall. • Temperatures are also variable, ranging from 40'F to 71'F annually. During the summer, fluctuations of 40'F in daily temperature are not unusual. The result is a frost-free period ~ of 130-150 days (Gleichman 1983)