2007-10-22_PERMIT FILE - C1981014A ‎(5)‎

• Permit No: C1981014A
• IBM Index Class Name: Permit File
• Doc Date: 10/22/2007
• Section_Exhibit Name: 4.05 Hydrologic Balance
• Media Type: D
• Archive: Yes

• constituents are expected to be minor, will generally be buffered by
normal runoff from undisturbed areas, will not affect surface water use,
and will continue to meet applicable effluent limitations under EFCI's
NPDES permits. Amore detailed discussion of potential water quality
impacts is presented in Section 2.05.6, Mitigations of Surface Coal Mining
Operation Impacts.
4.05.3 HYDROLOGIC BALANCE: DIVERSIONS AND CONVEYANCE OF OVERLAND FLOW AND
SHALLOW GROUNDWATER FLOW AND EPHEMERAL STREAMS DRAINING A
WATERSHED OF LESS THAN ONE SOUARE MILE
The drainage and sediment control plan described in Section 2.05.6,
Mitigation of Surface Coal Mining Operation Impacts, provides for
temporary diversion of the ephemeral Magpie Creek drainage, and overland
flows and shallow groundwater flows from the undisturbed area upgradient
and west of permanent coal refuse stockpiles. In addition, a system of
temporary ditches in both the mine and loadout areas function to collect
• and route runoff from disturbed areas to the existing sedimentation ponds.
These ditches and other sediment control structures are shown on the Mine
Area Surface and Groundwater Hydrology Map, (Map 12), Loadout Area Surface
and Groundwater Hydrology Map, (Map 13) and Drainage and Sediment Control
Map, (Map 20). All temporary diversion structures are designed and
constructed to pass the peak runoff from a precipitation event with at
least a two (2) year recurrence interval with a minimum of 0.3 feet of
freeboard. Ditch configuration, gradient and lining requirements reflect
hydrologic design calculations and will be effective in preventing erosion
and minimizing additional contributions of suspended sediment to runoff
flows. Design methodology and hydrologic calculations for the temporary
diversion structures are presented in Exhibit 19, Drainage and Sediment
Control Plan.
Most of the temporary diversion ditches in both the mine and loadout
areas, including ditches CD-1, CD-2, CD-3, the access road collection
ditch, and the loadout area perimeter ditch, are designed to safely pass
• the peak discharge from a 5-year, 24-hour storm event. Remaining
temporary ditches including the railway and stockpile containment ditches,
and the topsoil stockpile containment ditch in the loadout area, are
4.05-1