HYDRO28372

• Permit No: C1980007
• IBM Index Class Name: Hydrology
• Doc Date: 4/19/2004
• Doc Name: Exhibit 7 NPDES Permit
• From: Colorado Health Department of Public Health & Environment
• To: Mountain Coal Company
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

Mountain Coal and Bear Coal Water Quality Assessment CO-0038776 and CO-0044377
domestic wastewater effluent and dischazges to the North Fork of the Gunnison River via Outfall
004.
The Bear Coal W WTF Outfa11001 dischazges mine water to the North Fork of the Gunnison River
within one mile of the Mountain Coal W WTFs' Outfalls 004 and 016. Thus, Beaz Coal Company
WWTF Outfa11001 was modeled in conjunction with Mountain Coal W WTFs' Outfalls 004 and 016
when determining assimilative capacities in the North Fork of the Gunnison River. The Bear Coal
Company also dischazges to the North Fork of the Gunnison River via Outfa11002; however, this
discharge consists entirely of treated surface runoff water.
Based on WQCD general approaches, there are no dischazges composed entirely of surface runoff
water evaluated in this assessment. This is because automatic dischazges of surface runoffwater will
not occur during periods of critical low flow as surface runoffwater only occurs during precipitation
events, and any manual releases of surface runoff water discharges from ponds will be required to
meet the assimilative capacities set forth in this WQA.
The ratio of the low flow of the North Fork of the Gunnison River to the design flow from Mountain
Coal WWTFs' Outfalls 004 and 016 and Beaz /ciak WWTF Outfall 001 is greater than 150:1.
Analyses indicate that assimilative capacities for discharges to the North Fork ofthe Gunnison River
aze large due to large instream dilution.
The Mountain Coal Company, LLC is the sole known point source contributor of mine water to
Sylvester Gulch, West Sylvester Gulch, the DryFork ofMinnesota Creek, and Lone Pine Gulch; no
other point sources were identified as mine water dischazges to Sylvester Gulch, West Sylvester
Gulch, the Dry Fork of Minnesota Creek, and Lone Pine Gulch upstream or downstream. Thus, for
these four receiving waters, the findings of this assessment indicate that there is no dilution, no other
sources ofpollutants ofconcem, and that assimilative capacities are equal to the in-stream standazds
for Sylvester Gulch applied to Outfa11011; in-stream standards for the Dry Fork of Minnesota Creek
applied to Outfall 012; in-strearn standazds for Lone Pine Gulch applied to Outfall 013; and in-
stream standazds for West Sylvester Gulch applied to Outfa11017.
Information used in this assessment includes data gathered from the Mountain Coal Company, LLC,
Bear Coal Company, Inc., the U. S. Census Bureau, the WQCD, the Colorado Division of Water
Resources (DWR), the U.S. Environmental Protection Agency (EPA), the U. S. Geological Survey
(USGS), and communications with the local water commissioner. The data used in the assessment
consist of the best information available at the time of prepazation of this WQA package.
II. Water Quality
Mountain Coal WWTFs, via Outfalls 004 and 006, and the Beaz Coal WWTF, via Outfall 001,
discharge to the Water Body Identification (WBID) stream segment COGUNF02, which means the
Gunnison River Basin, North Fork of the Gunnison River Sub-basin, Stream Segment 02. This
segment is composed of the "Mainstem of North Fork ofthe Gunnison River from the confluence of
Muddy Creek and Coal Creek to the Black Bridge (41.75 Drive)." Stream segment COGUNF02 is
classified for Cold Water Aquatic Life Class 1, Class la Existing Primary Contact Recreation,
Agriculture, and Water Supply.
Appendix A Page 3 of 20 Last Revised 3/9/2004