2006-06-02_PERMIT FILE - C1980007A (5)

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Elk December and February are months that have experienced low minimum temperatures, though not as cold as January, and are markedly distinct from the other months. November, with its lowest monthly mean average temperature of 30.6 °F, does not approach December, January, or February in experiencing low temperatures. Both November and March do have quite cold days occasionally, however. The lowest recorded November temperature is -10 ~'. The lowest recorded temperature for March is ~ °F. The months of May through September clearly comprise the warmest period. The maximum temperatures for May and September are 91 and 94 °F, respectively. Next are April and October with maximum temperatures of 84 and 86 °F. The low~es[ temperat~ues experienced during this period are 22 °F in May and 26 °F in September, and lows of 0 °F in April and 7 °F in October. Precipitation The West Elk Mine study area generally receives 16 inches of precipitation between October and April. There is an increase to 20 inches in the Wooten Mesa-Lion Mesa vicinity and also where the land rises toward the south into the Chain Mountains. Precipitation at higher elevations in the Chain Mountains to the south of West Elk Mine rises to 25 inches, while at the summits of Mount Gunnison and Coal Mountain it is 30 inches. The May-September precipitation is generally eight inches near the study area It rises to 10 inches in the Chain Mountains and 12 inches atop Mount Gunnison. It rises to 30 inches in the Lennox Mesa-Lion Mesa vicinity and the Chain Mountains, and to 40 inches atop Mormt Gunnison and • Coal Mountain (CT.S. Department of Commerce, 1956). Specific information on precipitation at area monitoring sites is presented below. Somerset Precipitation Station The N.O.A.A. established a rain gauging station, the Somerset Station, at the West Elk Mine adjacent to the wastewater treatment plant in November 1983 following the closure of the Wilcox Ranch Station. This station was moved in 1993, a short distance near the southeast comer of fresh water pond FW-1. Precipitation data have been collected by N.O.A.A. through calendar year 1993. The following table presents monthly mean precipitation from the period of available record at this station, 1983 through 1993 (N.O.A.A., 1993, 1992-1983). IVIONTHL.Y PRECIPTTATION AVERAGE JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TTL AVG 1.23 2.33 238 1.76 1.90 1.03 0.71 1.36 2.13 1.98 224 1.90 20.95 l~lcox Ranch Station Prior to September, 1984 precipitation data were available from the Wilcox Ranch Station (38° 55' 107° 31' W), the climatic data station closest to the West Elk Mine study area at that time. • This station was east of Bowie on the north side of the North Fork of the Gnnni cnn River in the I.Otr/7 r/947R05; 8/907R7l; 6lD5 PR06;e1/mrF 2006 PRr0