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COLORADO DEPARTMEM OF PUBLIC HEALTH,4ND ENVIRONMENT, Water Quality Control Division Rationale -Page 3. Permit No. CO-0045161 Class~~cation: Segment 3a is designated Use Protected and is classified for the following uses: Recreation, Class 2; Aquatic Life, Class 2 (warm); Agriculture. Segment 1 is classified for the following uses: Recreation, Class 1; Aquatic Life, Class 1 (cold); Water Supply; Agriculture. Numeric Standards: The standards which have been assigned in accordance with the classiftcations for segments 1 and 3a can 6e found in the Classifications and Numeric Standards for the Lower Colorado River Basin, Regulation No. 37 (5 CCR 1002-37), as amended July 14, 1997. The complete list of standards for segment 3a is: dissolved oxygen (S.0 mg/Fj, pH (6.5-9.0 s. u.) and fecal colifarm (2000/100 mPl. There are no metals or other aquatic life standards for segment 3a. B. Receiving Water Data Quality: Quality data for Good Spring Creek, Taylor Creek and Wilson Creek are unnecessary because no effluent limitations for outfalls that discharge directly to state waters are flow-based. 2. 9uantiN Acute and Chronic Low Faws.• Quantity data far Good Spring Creek, Taylor Creek and Wilson Creek are also unnecessary because no effluent limitations far outfalls that discharge directly ro state waters are flow-based. IV. FACILITY DESCRIPTION A. Indushy Description Tvpe of Industry: Colowyo Coal Company L. P. operates a large multiple pit surface coal mine currently producing 5.8 million tons per year. Current facility wide air permit allows coal production to expand to 9.0 million tons per year. The facility uses draglines, trucks and shovels to mine coal. Eight separate coal seams are mined in the East Pit, a single seam is mined in an auxiliary pit. Colowyo began developing the West Pit in 1994. Zhis pit will eventually be similar to the East Pit in size and seam configuration. Five outfalls - 001, 004. 007, 008 and 009, serve partially reclaimed areas. However, full band release for these areas is not expected for at [east thirty ar forty years. As no total site served by one of the referenced ponds meets the definition of post-mining areas found in 40 CFR 434.11(k), this permit will consider these four outfalls as serving active mining areas for determination of the appropriate e~`lueru [imitations and other permit conditions. At this time, no outfallt authorized under this permit are subject to post-mining regulations. 2. Snarrac rn the Treatment Systems: The facility generates surface runoff; and may generate pumpage from mining pit areas and water from miscellaneous sources, all on an intermitteru basis. Ihese waters are a[1 roared to the various sedimentation ponds for treatment and discharge. Table II-1 specifies which sources are treated in speditc pond systems, as well as latitude and longitude locations[ and receiving water information. Table IV 2 in section IV. B. gives pond volumes, discharge flows and precipitation data. It should be noted that surface runoff does not include any water entering production piu and subsequently pumped out to the surface runoff collection system. Once water enters a pit, it typically is considered by the Division as process water" for differentiation because of the potential longer exposure to pollutants, and additional consideration is necessary to evaluate the need for appropriate effluent [imitations and accompanying permit conditions. the exception is for water that enters an upper bench area of a pit and gravity flaws out. The permitree has presented a strong argument that such water is similar in behavior and characteristics to surface runoff. Vehicle wash water may include potentially toxic pollutants removed from the outside, underside and engine compartment of vehicles at the mine site. Examples are ail and grease from the engine and other mechanical components on the vehicles, gasoline and other fuel constituents represented by benzene, ethylbenZene, toluene and xylene (BETX), and iron from coaf dust. No sanitary wastes are discharged ro state waters. Wastewater from the shops, production offices and human resources office are treated in anon-discharging aerated pond system. Sanitary wastewater from the remaining facilities are all treated in septic systems.