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and constructed to minimize erosion and additional contributions of <br />suspended solids to receiving drainages. Existing diversions are shown on <br />the Mine Area Surface and Groundwater Hydrology Map, (Map 11) and the <br />Loadout Area Surface and Groundwater Hydrology Map, (Map 12). The two <br />primary diversions at the Southfield Mine are the Magpie Creek diversion <br />and the clean water diversion to the west of the coal refuse stockpile. <br />Prior to completion of reclamation, EFCI will modify the existing Magpie <br />Creek temporary diversion to meet applicable permanent diversion <br />specifications. <br />Temporary diversions are normally required to be designed for the 25-year. <br />24-hour storm event, however, the Magpie Creek diversion was originally <br />designed and constructed as a permanent diversion. Although the original <br />design does not meet current regulatory requirements for permanent <br />diversion, it does meet temporary diversion requirements and the existing <br />channel will pass peak flows resulting from a 10-year, 24-hour storm <br />event. The clean water diversion above the permanent coal refuse <br />stockpile is a permanent diversion and as such has been designed and <br />constructed to pass peak flows resulting from the 1OO•year, 24-hour storm <br />event. Specific design criteria for both of these diversions are <br />presented in Exhibit 19, Drainage and Sediment Control. <br />All sedimentation structures for Southfield mine and loadout areas have <br />been designed and constructed and are operated and maintained to effect <br />compliance with applicable regulatory effluent limitations. All surface <br />water discharges from mine disturbance areas must meet the requirements of <br />EFCI's NPDES discharge permits (Permit Nos. CO.0036595 (Mine) and CO- <br />0037109 (Loadout)). These permits have been approved and are administered <br />by the Colorado Department of Health to meet provisions of the National <br />Pollution Discharge Elimination System. Over the time interval since <br />operations began in 1978, Dorchester, and subsequently EFCI, have <br />maintained an effective record of compliance with applicable provisions of <br />NPDES permits. Copies of these permits, describing effluent limitations <br />and other discharge constraints are presented in Exhibit 4, Other Permits. <br /> <br />CIWORR\PIU\l6U8N1~R IS.R E~ <br />a.~.~~~ 2.05.6.37R Revised - April 1993 <br />