1988-06-17_REPORT - C1981013 (2)

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1 . 0 INTRODUCTION Wyoming Fuel Company (WFC) owns and operates the New Elk and Golden Eagle underground coal mines in southern Colorado. This report presents the hydrologic monitoring activities conducted at the two mines during 1987 and analysis of trends over the four year monitoring period. Appropriate data and information related to this assessment is presented in the Appendices of this report. As the mine permit areas are adjacent, many of the studies have been conducted for the entire area of both mines as opposed to assessing each facility separately. Also included in this report is a discussion of mitigative measures taken to minimize disturbance to area hydrologic functions and plans for future hydrology monitoring activities. 1 . 1 Site Description The mine sites are located approximately six miles west of Weston in Las Animas County, Colorado (T33S , R68W) and are situated in mountainous terrain which provides numerous canyons contributing runoff to the series of ephemeral, intermittent, and perennial streams of the area (Figure 1) . The surface facilities are adjacent to the Purgatoire River which is the primary stream drainage of the area. The general direction of stream flow is easterly to the confluence with the Arkansas River, also in Las Animas County. The closest weather station to the site is located at the Trinidad Airport ( elevation 5, 746 ft) approximately 30 miles east. Over a recording period of 50 years, total precipitation averaged 13. 5 inches . The majority of this precipitation occurs from April to September, July recording the most rainfall in the form of rapidly moving thundershowers . The mean temperature is 51 . 50F, January and July having the lowest and highest temperature, respectively. The project area is approximately 1, 650 feet higher in elevation than the Trinidad Airport and can be considered to have a somewhat lower mean 1