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Pictured Cliffs Sandstone and Fruitland Formation. <br />Ground Water Hydrology <br />Two aquifers are in hydrologic communication with the Carbon Junction Mine: the Animas River <br />alluvium (400 ft. downslope from the mine permit area) and the Pictured Cliffs sandstone (subcrops <br />beneath the mine pit area). <br />Monitoring of alluvial ground water has not been required at the Carbon Junction Mine. Animas River <br />alluvial water can be expected to have not been degraded by coal mining at Carbon Junction because the <br />less than 10 -acre surface area of coal spoil at the mine would not generate enough leachate to overcome <br />the dilutional effect of native alluvial ground water. <br />Bedrock ground water at the mine was monitored in well 95-1 from 1995 through 2005. This well <br />presumably was completed in the Fruitland Formation and Pictured Cliffs sandstone. Well 95-1 is <br />located within the expected flowpath of any coal spoil leachate that would be generated in the Carbon <br />Junction backfilled pits. Monitoring data from this well did not show evidence of leachate prior to 2006. <br />The requirement to monitor well 95-1 was eliminated in TR -13. Elimination of this monitoring was <br />based chiefly on: a) historical monitoring data from the wells indicating no impacts from coal mining at <br />Carbon Junction, b) recognition that any coal spoil leachate generated by and migrating from the <br />relatively small (less than 10 -acre) pit area at Carbon Junction would undergo significant attenuation and <br />dispersion in the Animas River alluvium and Pictured Cliffs sandstone within a few hundred feet of the <br />mine pits. <br />The relatively small pit area of the Carbon Junction Mine (less than 10 acres) indicates the mine does not <br />have the potential to negatively impact ground water quality; therefore, a ground water point of <br />compliance has not been established. <br />Surface Water Hydrology <br />The Carbon Junction Mine is located in the Animas River Drainage Basin, in the valley of the upper <br />reach of Carbon Junction Canyon. The channel of Carbon Junction Canyon is deeply incised, has a steep <br />gradient, and has only ephemeral flows. When flow occurs, it is directly tributary to the Animas River to <br />the southwest. The drainage area of Carbon Junction Canyon is 0.8 square miles. Three intermittently <br />flowing natural springs (1, 3, and 4) have occasionally created minimal baseflow in Carbon Junction <br />Canyon. <br />The channel of Carbon Junction Canyon extends along the contact of the Pictured Cliffs Sandstone and <br />the Fruitland Formation. These strata discharge to the channel of Carbon Junction Canyon (via natural <br />springs) during dry periods. When the channel contains surface runoff, it recharges the Pictured Cliffs <br />sandstone and the Fruitland Formation. <br />Flows in Carbon Junction Canyon usually occur only when there has been a thunderstorm or when snow <br />is melting. Highest flows occur during springtime snowmelt and in early summer when precipitation <br />events are more frequent. Water quality in Carbon Junction Canyon fluctuates seasonally, with the best <br />quality occurring during periods of high flow. <br />Historically, flows in Carbon Junction Canyon have not been diverted for flood irrigation of crops. Any <br />use of water from Carbon Junction Canyon would be through diversion of Animas River water <br />downstream of the confluence of these two streams. The mine's previously -approved postmining land <br />uses of industrial, commercial, residential, and recreation were not expected to use surface water. <br />31 <br />