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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale - Page 3. Permit No. CO-0032115. I0. FACILITY DESCRIPTION A. Industry Description The facility is a surface sub-bituminous coal mine. There aze three active pits, from which coal is mined and then hauled directly to the adjacent Craig Generating Station. All coal produced is sold to Colorado-Ute, which owns the station. The average production rate is 2.2 million tons/year, with a mazimtm rate of 2.6 million tone/year. The facility is covered under federal regulation 40 CFR 434, the Coal Mining Point Source Category, Subpart D, Alkaline Mine Drainage, and Subpart F, Miacellaneoue Provisions, Effluent Limitations for Precipitation Events. B. Wastewater Treatment Description Treatment is provided for all of the wastewater sources by sediment ponds. The wastewater sources are surface runoff, surface mine dewateriag, spoil springs, and an industrial waste pond. This waste pond receives runoff from the truck fueling area and the shop area, wastewater from the truck washing facility, and can be used to contain fuel spills from tanks. No chemicals are used for the thick washing. The pond provides settling, and two oil booms are in place near the outfall to remove oil and grease. Two concrete underground oil separator tanks are also provided after the pond outfall. The effluent then goes through two sediment ponds before discharging at 00 2. Discharge points 012, 013 and 014 are proposed but not yet constructed. The permittee plans to construct them in middle to ]ate 1991. In order to avoid a permit amendment when the points are put into active use, they are included in the permit renewal. CThe permittee must therefore submit discharge monitoring reports for these points whether they ate active or not.) For discharge points 001, 005 and 011, the parshall flume for flow monitoring is Located downstream of the sediment pond overflow. At 001, this situation will be changed in the summer of 1991, when the final pond is rebuilt and the flume incorporated into the pond overflow. At 011, the flume is 50 feet downstream, but the pond has never discharged, and so no change is considered necessary. At 005, the flume is also about 50 feet downstream. There are seeps in between the pond and the flume, and so flow could be measured at the flume while no discharge is occurring from the pond. However, the pond only discharges when the headgates are opened, which is done during spring runoff and during large storm events, and so the only problem anticipated 1n flow monitoring is in the accuracy of the readings. Therefore, the permittee will be required to submit all data collected for the past year on the seep flow volumes at 005 and 011, and then on an on-going basis to be submitted with their Discharge Monitoring Reports Csee Part I.B.2 of the permit).