2008-07-25_GENERAL DOCUMENTS - C1981010 (2)

Home Browse Search

The climate of the Craig, Colorado area is characteristic of semi-arid steppe regions. The average annual precipitation for the town of Craig, 5 miles north of Trapper, is 13.5 inches, of which over one-third is snowfall (averaging 66.5 inches/year). Trapper Mine's average annual precipitation is 16.7 inches. The mean annual temperature in Craig is 43°F, with recorded extremes of -45°F and +100°F. Winds are predominantly from the west, but are locally modified by topographic features. The growing season for the area in the vicinity of Craig averages 77 frost-free days. Soil Types Three soil orders are found in the permit area: Aridisols, Entisols, and Mollisols. These soil orders are characteristic of fairly steep, semi-arid regions of northwestern Colorado. They represent soils that grade from recently developed soil bodies with minimum horizon development (Entisols) to older soils with well-defined diagnostic horizons (Mollisols). Soil Characteristics and Distribution Overall, the soils found in the proposed permit area are relatively deep and well-drained. Effective rooting depth varies from two to sixty inches within the area. The deepest soils yielding the greatest rooting depths occur in valleys and on the leeward sides of ridges. Soil reaction is slightly acid to moderately alkaline over the permit area with the exception of inclusions of small scattered areas with saline substrata. These small areas have probably formed in place from weathered sodic shale. Control of Vegetation Distribution by Climate and Soils Vegetation in the area grows largely in response to macro-climatic influences of the region. The north-facing slopes, having moderate to deep soils, a relatively mesic moisture regime, and favorable levels of insolation throughout the year, are characterized by well-developed mountain shrub communities. On the colluvial toe-slopes, communities dominated by sagebrush and some grasses occur. On the south-facing slopes behind the ridgeline of the Williams Fork mountains, vegetative communities are not as well-developed in terms of cover, density, and production due to the less favorable soils, moisture regime, and increased solar insolation. The trend in these areas is toward communities dominated by juniper, pihon, mountain mahogany and xerophytes. Control of Vegetation Distribution by Land Uses Within the permit area, natural vegetative communities have been modified to varying degrees by humans and domestic animals. Much of the land along toe-slopes and valley bottoms has been cleared of native vegetation and is currently used for dry land agriculture. Most of the north-facing slopes in the area have been historically used for the grazing of sheep and/or cattle. The farming and ranching have produced a mosaic of vegetation communities in the permit area. Vegetation Distribution in Permit Area Trapper Mine 12 July 25, 2008