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Hydrogeological Evaluation of Sunday Mines Group <br />Geologic and Hydrologic Conditions <br />Figure 2-1 also shows that the Salt Wash Member of the Morrison Formation crops <br />out west-northwest of the Topaz mine adjacent to the Dolores River. <br />2.3 Regional Hydrogeologic Framework <br />2.3.1 Climate <br />The Sunday Mines Group is located within an and 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 />and climates, and a large excess of evaporation over 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 ischyetal map <br />provided by Weir et al. (1983). The period of record for this weather station extends <br />from 1961 through 2007. Pan evaporation data are not available at the Uravan station. <br />Therefore, pan evaporation data were collected from a monitoring station at Dead <br />Horse Creek near Naturita, Colorado. The period of record for these data extends <br />from 1971 to 1980. <br />Table 2-1 shows the monthly average maximum and minimum temperatures for the <br />period of record. Large daily temperature fluctuations are typical for this semi-arid to <br />and region, with upwards of 30° F to 40° F fluctuations between night and day during <br />most of the year. Summer high temperatures can reach 100° F or greater and winter <br />low temperatures can reach below 0° F, however, daytime highs in the winter are <br />normally above freezing (32° F). <br />Table 2-2 shows the monthly total precipitation data for the period of record and <br />Figure 2-6 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 /> <br />2-7 <br />TA64986-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.14 - Hydrogeology Repon\fhal sunday hydro report\textTINAL Sunday Hydrogeology Repon.doc