2008-08-11_REVISION - C1992080 (19)

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Surface Water Hydrology The Carbon Junction Mine is located in the Animas River Drainage Basin, in the valley of the upper reach of Carbon Junction Canyon. The channel of Carbon Junction Canyon is deeply incised, has a steep gradient, and has only ephemeral flows. When flow occurs, it is directly tributary to the Animas River to the southwest. The drainage area of Carbon Junction Canyon is 0.8 square miles. Three intermittently flowing natural springs (1, 3, and 4) have occasionally created minimal baseflow in Carbon Junction Canyon. The channel of Carbon Junction Canyon extends along the contact of the Pictured Cliffs Sandstone and the Fruitland Formation. These strata discharge to the channel of Carbon Junction Canyon (via natural springs) during dry periods. When the channel contains surface runoff, it recharges the Pictured Cliffs sandstone and the Fruitland Formation. Flows in Carbon Junction Canyon usually occur only when there has been a thunderstorm or when snow is melting. Highest flows occur during springtime snowmelt and in early summer when precipitation events are more frequent. Water quality in Carbon Junction Canyon fluctuates seasonally, with the best quality occurring during periods of high flow. Historically, flows in Carbon Junction Canyon have not been diverted for flood irrigation of crops. Any use of water from Carbon Junction Canyon would be through diversion of Animas River water downstream of the confluence of these two streams. The mine's approved postmining land uses of industrial, commercial, residential, and recreation are not expected to use surface water. The quantity of water from Carbon Junction Canyon tributary to the Animas River would be insignificant for the overall flow of the river. The drainage basin of Carbon Junction Canyon is only 0.8 square miles compared to over 1090 square miles for the Animas River above the Colorado-New Mexico state line. The Carbon Junction Mine is on Segment 13b of the Animas and Florida River Sub-basin of the San Juan and Dolores River Basin. Colorado Water Quality Control Commission lists numeric standards for this segment in its regulation 3.4.0. The permittee monitors water at two CDPS, outfalls, the south pond, Pond 1 (outfall 001), and the north pond, Pond 2 (outfall 002). Both ponds discharge to Carbon Junction Canyon. Both ponds discharged in January 2005, but did not discharge in 2006 or 2007. Sampling of springs 1, 3, and 4 was terminated in TR-13. Climate The climate of the area is relatively moderate, with a monthly low mean temperature of 25°F in January and a monthly high mean temperature of 67°F in July. Record temperature extremes range from a high of 99°F, recorded in August, to lows of -27°F , recorded in January and February. Annual precipitation averages 18.0 inches, with a maximum of 2.36 inches in August and a minimum of 0.98 inches in November. The average snowfall is 65.3 inches, with the largest amount in January (21.2 inches), followed by December (14.8 inches). The average wind direction is generally from the west, with an average speed of less than one knot. 6