2008-02-04_PERMIT FILE - C1982056A

Home Browse Search

Extremes, 1971-1978. Rased on data collected by the United States Department of Commerce, the mean annual • temperature at Steamboat Springs is 38.7 degrees F with recorded extremes of 96 degrees Fand -50 degrees F. Mean monthly temperatures range from 15.4 degrees F in January to 16.8 degrees F in July; mean daily maxima range from 29.3 degrees F in January to 82.8 degrees in July; and mean daily minima range from I.5 degrees F in January to 40.9 degrees F in July. Freezing temperatures can occur during any month of [he year. The average annual growing season (above 20 degrees F) of irrigated land near the Yampa River and Steamboat Springs is 102 days according to the Colorado Water Conservation Board and USDA, 1969. Mean temperatures at Hayden are about 3 to 4 degrees F warmer than corresponding mean temperatures in Steamboat Springs. Monthly means a[ Hayden range from 17.3 degrees F in January to 65.9 degrees F in July. Mean daily maxima range from 31.0 degrees F in January to 85.3 degrees F in July. Extreme temperatures of 100 degrees Fand -45 degrees F were recorded at Hayden in 39 years of observations, freezing temperatures can occur during any month of the year in Hayden. Win[I The east-west orientation of [he Yampa Valley is conducive to easterly downslope breezes during nighttime hours and stronger westerly upslope +ainds during the day. Local terrain has the effect of shielding the valley with respect to surface air me[ion, and consequently, calm or near-calm conditions are common, especially at night and in the early morning. Preliminary information on atmospheric stability and associated air motion has been collected near Gaig and may be used as an indication of air movement patterns farther up the Yampa River Valley. Four stability categories are • defined: stable, unstable, neutral and transition conditions. Stable conditions occur when the air layers close to the ground undergo cooling with associated low wind speeds; neutral conditions occur with cloudy skies and/or high wind speeds; transition conditions occur in [he short period of time following the breakup of stable conditions and prior to the onset of unstable or neutral conditions. Stable layers, at ground level, occurred approximately 60 percent of [he time. Such layers are q~pically as deep as 1,100 feet and can persist for several days during winter and spring. Under stable conditions, surface winds are light and variable. Local influences control the surface wind about 40 percent of the time. Ordinarily, local influences are caused by [he valleys of tributaries to the Yampa River. However, the drainage air that flows down these smaller valleys is typically only 100 [0 200 feet deep. The existence of stable layers is most common from 7 p.m. to I I a.m., followed by upslope, or westerly winds through about 6 p.m. The gradient westerly winds have higher velocities than the drainage winds and are associated with neutral or unstable conditions. In the transition period behveen stable and neutral or unstable conditions, surface winds tend to be ligln and variable. Wind data from the Federal Aviation Administration a[ the Hayden Airport ([he closest reporting station collecting wind data) show that wind velocities of 3 to I S miles per hour blow from the east to northeast 16.3 percent of the time and from the west to southwest 31.3 percent of the time. Also, winds with velocities exceeding I S miles per hour blow out of the west-southwest 7.5 percent of the time. Winds so light [hat their speeds were not detectable (0 to 3 miles per hour) occurred 6 percent of [he time. The remaining 34.4 percent of [he observations occurred randomly. Weather Station at Enerey Mine No. 1 • A weather station was operated at Energy Mine No. I for the period of 1977 and 1978. Temperature and precipitation information from the weather station are found in Table 19, Weather Data -Energy Mine No. 1 Station. MR 97-1~4 2.04-46 Revised 10/02/97