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• <br />• <br />• <br />Seneca II: 11R0484 <br />Seneca IIW: 82R0258 <br />Yoast: 96R0542F <br />15: The pre -SMCRA (i.e., pre -1977) mining area of the Seneca II Mine exists northeast <br />of the old office area (now used by the Peabody Sage Creek Mine). The old mine pits <br />were also used at one time as a fly ash disposal area from the Hayden Station power plant. <br />Disposal of the fly ash in this area was discontinued in the early 1980's. No discharges <br />from this area enter into NPDES drainages for the Seneca II Mine. <br />16 and 17: See application form <br />18: Site Flume Capacity (mgd) <br />005 18 "w x 24 "d Parshall 11.26 <br />006 18 "w x 24 "d Parshall 11.26 <br />008 12 "w x 15 "d Parshall 3.63 <br />009 12 "w x 18 "d Parshall 4.79 <br />010 18 "w x 18 "d Parshall 7.23 <br />011 12 "w x 18"d Parshall 4.79 <br />012 12 "w x 18 "d Parshall 4.79 <br />013 2 ft. H -flume 7.10 <br />014 3 ft. H -flume 19.65 <br />015 2 ft. H -flume 7.10 <br />016 3 ft. H -flume 19.65 <br />017 3 ft. H -flume 19.65 <br />Calibrations are normally verified on a monthly basis. <br />19 and 20: See application form <br />21: Outfalls 002, 003 and 004 were transferred to the Peabody Sage Creek Mine, CPDS <br />Permit No. CO- 0048275, in 2010. The following table provides sediment pond volumes <br />(in million gallons) at the emergency spillway (i.e., "emergency" storage), the principle <br />spillway (i.e. "permanent" storage), and the difference between the two (i.e., "working" <br />storage). The reader may note that the working storage is sometimes less than the ten - <br />year storm volume (see application form Table 21). In spite of this, adequate sediment <br />retention is provided, in part due to the permanent storage and also due to the fact that the <br />principle spillway discharges during the storm event. Computer models (SEDCAD) of <br />how the storm event affects pond discharge at each site has been provide to, and approved <br />by, the CDRMS. <br />