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~ ~_ <br />THE ALLEN MINE <br />This study was conducted at the Allen Mine, a deep mining operation <br />recovering metalurgical-grade bituminous coal. The mine is located 40 <br />miles west of Trinidad, in Las Animas County, Colorado and has been active <br />in the removal of coal since 1951. This coal is interbedded in marine <br />shale and both are removed during the mining process. The two materials <br />are separated and the shale waste material, commonly called slack, is <br />placed in waste dumps near the mine mouth. <br />Fifteen years of climatological data has been collected at North <br />• <br />Lake, 10 miles north of the mine site. The average annual precipitation <br />between 1962 and 1976 was 51 cm. During the 3 years of this study preci- <br />pitation ranged from 34.3 cm in 1978 to 50.8 cm in 1979. <br />Soil analysis has shown that the waste material contains gravel <br />fragments greater than 2 mm which account for 38 to 69 percent of the <br />waste volume. The remaining volume has been classified in texture as a <br />sandy loam to clay loam. The organic matter content was 1.0 to 2.8 percent. <br />This value also reflects carbon contamination from the coal in the waste <br />ma*_erial. The electrical conductivity ranged from 0.8 to 6.7 mmhos/cm and <br />the pH was 8.3 to 8.8. The sodium absorption ratio (SAR) ranged from 15 <br />to 38. The SAR, pH, and electrical conductivity values are all high enough <br />to potentially inhibit plant growth. <br />The mine is situated in the valley of the Purgatoire River. The land <br />~1 <br />adjacent to the mine in the valley bottom is in improved pasture or meadows <br />used for hay production and livestock grazing. <br />13 <br />