2005-12-02_PERMIT FILE - C1981019

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 12/2/2005
• Section_Exhibit Name: Exhibit 07 Item 02 CDPS Permit, SMP, SPCC Plan
• Media Type: D
• Archive: No

Colowyo Coal Company
IV. Technical Analysis
COG-0045161
An analysis of pollutants of concern was conducted to determine the assimilative capacity of the
waterbodies at the outfalls listed in Table 2. The analysis consisted of mass balance calculations.
The mass balance calculation accounts for the upstream concentration of pollutant, critical low flow
(minimal dilution), effluent flow, effluent concentration and the water quality standard. The mass
balance equation is expressed as:
Mz _ M3Q3-MiQi
Qz
Q~ =Upstream low flow (lE3 or 30E3)
QZ =Average daily effluent flow (design capacity)
Qj =Combined downstream flow (Q~ + Qz)
M~ = Instream background pollutant concentration
Mz =Maximum allowable effluent pollutant concentration
M3 =Maximum allowable instream pollutant concentration (water quality standard)
For the dischazges to Wilson Creek, Taylor Creek, and Good Spring Creek the chronic and acute low
flows aze zero. When the low flow is zero, the maximum allowable effluent pollutant concentration
(Mz) equals the water quality standard (M3). During low flow conditions, fOr streams with a low
• flow of zero, the stream flow consists entirely of the effluent discharge therefore no assimilative
capacity is available.
Nearby Sources:
There ate no nearby discharges. The dischazge neazest the Colowyo mine outfalls is to Seeping
Spring Gulch tributary to Stinking Gulch a tributary to Milk Creek above the Wilson Creek/Milk
Creek confluence. There aze no identified significant non-point sources above the Colowyo mine.
Pollutants of Concern:
The following pollutants were identified by the WQCD as pollutants of concern for this facility:
Arsenic Cadmium Chromium
Copper Iron Lead
Manganese Selenium Silver
Zinc Cyanide Fluoride
Nitrite Nitrate Sulfate
Chloride
Colowyo Coal Company Discharges:
Colowyo Coal Company has dischazges to Wilson Creek, Taylor Creek, and Good Spring Creek.
These small drainages have little or no flow except during certain times of the year or during and
• shortly after a rainfall event. The combined design capacity or maximum dischazge of all of the
outfalls is 47.56 mgd (73.7 cfs). These discharges with th`e source and maximum flow aze shown on
Table 6, Summary of Dischazges From the Colowyo Coal Company.
WQA 7 Revised 1/24/2005