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<br /> <br /> <br /> <br />PR-04, Colowyo Coal Mine C1981-019 22 August 2016 <br /> <br />drinking water standards, but manganese concentrations did not. Total recoverable iron <br />standards did not exceed the USEPA aquatic life standard. TDS concentrations increase in the <br />downstream direction. <br /> <br />The Division has determined that alluvial valley floors (AVFs) exists within the area of the <br />Collom permit expansion area, as well as the adjacent area. These can be found within the <br />watersheds of Collom Gulch, Little Collom Gulch and Morgan Gulch. Surface coal mining and <br />reclamation operations at Colowyo, if conducted in compliance with the Permit, will preserve the <br />essential hydrologic functions of AVFs outside the permit area and will reestablish the essential <br />hydrologic functions of AVFs within the affected area, throughout the mining and reclamation <br />process (Rule 4.24.2). <br /> <br />Ponds at the Colowyo Mine are designed, constructed, and maintained to hold and passively treat <br />the volume from a 10-year, 24-hour precipitation event. Discharges from ponds are monitored to <br />detect exceedances of limitations listed in the Colorado Discharge Permit System (CDPS) <br />permit. In addition to the use of sediment ponds, the Division proposes to grant small area <br />exemptions (SAEs) for some locations on the Collom site, which shall be outside of the sediment <br />control system of ditches and ponds. Some of the proposed SAEs in the Collom area drain areas <br />larger than the Division usually considers appropriate for SAEs. As a result, the Division has <br />required CCC to reevaluate these sediment control structures in accordance with Rules 4.05.2, <br />4.05.5, and 4.05.6. In addition, CCC must avoid mixing surface drainage from SAEs with <br />discharges from mining pits. <br /> <br />Additional information related to surface water at the Colowyo Mine: <br /> Precipitation averages 18 inches annually on the Colowyo property, and runoff is limited. <br />Flows in the smaller drainages are mainly in response to snow melt or intense <br />thunderstorm events. <br /> Previous studies by Tetra Tech and by Cedar Creek Associates have identified 33 seeps <br />and springs within the Collom Gulch, Little Collom Gulch, and Jubb Creek drainages. <br /> The Wilson Reservoir, from which water is drawn for mining activities, is not within the <br />Permit area. The pumping station at the reservoir and the pipeline from the pumping <br />station to the mine are included in the Permit. <br /> <br /> <br />3.2.10 Vegetation <br /> <br />Baseline vegetation information is found in Section 2.04.10, Map 4, and Exhibit 10 of the PAP <br />original volumes (Volumes 1 – 11). Vegetation information associated with Lower Wilson and <br />South Taylor expansion areas can be found in Section 2.04.10 of Volume 12, Exhibit 10 of <br />Volume 13, and Maps 3, 4A, and 4B of Volume 14. Vegetation information associated with the