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Mountain Coal and Bear Coal Water Quality Assessment CO-0038776 and CO-0044377 <br />domestic wastewater effluent and discharges to the North Fork of the Gunnison River via Outfall <br />004. <br />The Bear Coal W WTF Outfa11001 discharges mine water to the North Fork of the Gunnison River <br />within one mile of the Mountain Coal WWTFs' Outfalls 004 and 016. Thus, Bear Coal Company <br />W WTF Outfa11001 was modeled in conjunction with Mountain Coal W WTFs' Outfalls 004 and 016 <br />when determining assimilative capacities in the North Fork of the Gunnison River. The Beaz Coal <br />Company also dischazges to the North Fork of the Gunnison River via Outfa11002; however, this <br />discharge consists entirely of treated surface runoff water. <br />Based on WQCD general approaches, there aze no discharges composed entirely of surface runoff <br />water evaluated in this assessment. This is because automatic discharges of surface nmoffwater will <br />not occur during periods of critical low flow as surface runoffwater only occurs during precipitation <br />events, and any manual releases of surface runoff water dischazges from ponds will be required to <br />meet the assimilative capacities set forth iri this WQA. <br />The ratio of the low flow of the North Fork of the Gurmison River to the design flow from Mountain <br />Coal WWTFs' Outfalls 004 and 016 and Bear /ciak WWTF Outfall 001 is greater than 150:1. <br />Analyses indicate that assimilative capacities for discharges to the North Fork ofti're Gunnison River <br />are laxge due to lazge instream dilution. <br />-The Mountain Coal Company, LLC is the sole known point source contributor of mine water to -~ <br />Sylvester Gulch, West Sylvester Gulch, the Dry Fork ofMinnesota Creek, and Lope Pine Gulch; no . <br />other point sources were identified as mine water dischazges to Sylvester Gulch, West Sylvester <br />Gulch, the Dry Fork of Minnesota Creek, and Lone Pine Gulch upstream or downstream. Thus, for <br />these four receiving waters, the findings ofthis assessment Indicate that there is no dilution, no other <br />sources of pollutants of concern, and that assimilative capacities aze equal tothe in-stream standazds <br />for Sylvester Gulch applied to Outfa11011; in-stream standards for the Dry Fork of Minnesota Creek <br />applied to Outfall 012; in-stream sta-?dazds for Lone Pine Gulch applied to Outfall 013; and in- <br />stream standazds for West Sylvester Gulch applied to Outfa11017. <br />Information used in this assessment includes data gathered from the Mountain Coal Company, LLC, <br />Beaz Coal Company, Inc., the U. S. Census Bureau, the WQCD, the Colorado Division of Water <br />Resources (DWR), the U.S. Environmental Protection Agency (EPA), the U. S. Geological Survey <br />(USGS), and communications with the local water commissioner. The data used in the assessment <br />consist of the best information available at the time of prepazation of this WQA package. <br />II. Water Quality <br />Mountain Coal WWTFs, via Outfalls 004 and 006, and the Bear Coal WWTF, via Outfall 001, <br />discharge to the Water Body Identification (WBID) stream segment COGUNF02, which means the <br />Gunnison River Basin, North Fork of the Gunnison River Sub-basin, Stream Segment 02. This <br />segment is composed ofthe "Mainstem of North Fork of the Gunnison River from the confluence of <br />Muddy Creek and Coal Creek to the Black Bridge (41.75 Drive)." Stream segment COGUNF02 is <br />classified for Cold Water Aquatic Life Class 1, Class la Existing Primary Contact Recreation, <br />Agriculture, and Water Supply. <br />Appendix A Page 3 of ZO Last Revised 3/9/2004 <br />