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The Division proposes to grant an exemption from the use of sediment ponds for NPDES <br /> discharge points 001, 002 and 015 from underground mine workings because sediments are <br /> settled out in underground sumps before being discharged into the Colorado River. Additional <br /> ponds and treatment facilities are not necessary for these three discharge points to meet the <br /> effluent limitations of Rule 4.05.2 and applicable State and Federal water quality standards for <br /> receiving streams. <br /> In 1997, Pond 12 was designed to act as a mine water treatment pond for the mine water <br /> discharge associated with the Roadside North Portal Mine,NPDES discharge point 004. Mine <br /> water treated in Pond 12 is designed to hold mine water discharges for 2.5 days to settle out the <br /> suspended solids. The operator has proposed using a flocculent (Nalco 9806) on occasion to <br /> settle out some of the suspended clays. Sulfuric acid will also be added to reduce the pH to <br /> minimize the amount of flocculant needed to settle out the suspended solids. <br /> These discharge points are located as follows(4.05.2(3)(b)(ii)): <br /> Discharge Location NPDES Point <br /> Roadside South Mine Portal 001 <br /> Northwest Intake Portal 002 <br /> Roadside North Mine Portal 004 <br /> Roadside South Mine 2 West Portals 015 <br /> B. Diversions and Conveyance of Overland Flow <br /> 1. All conveyance structures within the permit area are designed and constructed in <br /> accordance with Rule 4.05.3. Permanent diversions above coal mine waste banks are designed <br /> and constructed in accordance with Rule 4.09.2(7). Table 13-4 of the application lists all <br /> diversion and conveyance ditches along with references to the appropriate exhibits for designs <br /> and cross sections. Calculations used to design these structures are given in appendix 13-2 of <br /> the permit application. One approved, but not yet constructed permanent diversion <br /> segment, designated South End Rip Rap Channel, on Exhibit 6C, will be installed in <br /> association with installation of drainage benches during final reclamation of the Roadside <br /> Refuse Disposal Area. <br /> C. Stream Channel Diversions <br /> Construction of the Cameo Refuse Disposal Areas involved the installation of a permanent <br /> ephemeral stream channel diversion along a segment of Coal Canyon in the vicinity of the <br /> refuse areas. A total of approximately 600 feet of the Coal Canyon drainage was diverted. <br /> The channel segment was constructed to have non-erosive velocities while passing the <br /> 100-year, 24-hour precipitation event. Four rock drop structures were installed along the <br /> diversion segment in 1998, using a D50 rip-rap size of 30" on a slope of 4h:ly. The 4 <br /> structures drop the elevation of the streambed 5 to 8 feet at each structure. Rip-rap was <br /> 25 <br />