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12.0 Climate <br />The Sunday Mines Group is located within an arid environment. Climatic conditions <br />in this area generally include moderate to cold winter night time temperatures with <br />hot summer daytime temperatures, large daily temperature fluctuations typical of <br />arid climates, and a large excess of evaporation over precipitation. <br />12.1 Annual Precipitation <br />Weir et al (1983) investigated climatic fluctuations within the Dolores River Basin, and <br />observed that precipitation is correlated with elevation, with highest precipitation <br />amounts occurring within mountain areas surrounding the basin, and markedly <br />lower precipitation occurring within the central lower- elevation basins. Weir et al. <br />(1983) provides contour maps of precipitation within the Dolores River Basin, which <br />show the area of the Sunday Mines Group to be among the driest portions of the <br />basin. <br />Site - specific climatic data are not available for the Sunday Mines Group. Therefore, <br />temperature and precipitation data were collected from the Uravan, Colorado, <br />National Oceanic Atmospheric Administration (NOAA) weather station. Precipitation <br />at Uravan is estimated to be similar to the mine area based on an isohyetal map <br />provided by Weir et al. (1983). The period of record for this weather station extends <br />from 1961 through 2007. <br />Table 12 -1 shows the monthly total precipitation data for the period of record and <br />Figure 12 -1 is a box plot showing monthly total precipitation summary statistics. <br />October, August, and September are the wettest months of the year, with median <br />monthly precipitation totals of 1.36 inches (in), 1.25 in, and 1.04 in., respectively. June, <br />February, December, and January are the driest months of year, with median monthly <br />precipitation totals of 0.34 in, 0.61 in, 0.64 in, and 0.70 in, respectively. The wettest <br />month on record is October 1972 when 5.89 in of precipitation were recorded at the <br />Uravan station. <br />Figure 12 -2 compares the annual precipitation to the average annual precipitation <br />over the period of record, which shows extended periods of particularly high or low <br />precipitation. This data is shown in terms of water year totals, from October through <br />September. The average annual precipitation for water years 1962 through 2007 is 12.6 <br />in. Note a yearly total for water year 1961 could not be computed because <br />precipitation data from October through December of 1960 are not available. <br />Maximum annual precipitation was recorded in 1997 at 19.87 in, while the minimum <br />precipitation was recorded in 1974 at 7.66 in. <br />12.2 Direction and Velocity of Prevailing Winds <br />Data regarding wind speed and direction are presented in Table 12 -2 and Figure 12 -3. <br />C \Users 1cwoodward&Desktop \Sundays \FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx <br />12 -1 <br />