2010-05-07_PERMIT FILE - C2006085 ‎(2)‎

• Permit No: C2006085
• IBM Index Class Name: Permit File
• Doc Date: 5/7/2010
• Section_Exhibit Name: 2.05 Operation and Reclamation Plans
• Media Type: D
• Archive: No

Northfield will construct and maintain a system of collection and
diversion ditches to effectively control surface drainage. The ditches
will route runoff from undisturbed areas around mining disturbance,
and collect and route disturbed area runoff to sedimentation
structures.
In order to pass surface runoff from undisturbed areas away from the
mine facility area, Northfield proposes to construct a temporary clean
water diversion ditch system on the west side of the facilities area.
This ditch system will be designed and constructed to safely pass peak
flows resulting from a 10 -year, 24 -hour event (North Ditch) and from a
100 -year, 24 -hour event (South Ditch). The planned configuration of
the system involves splitting the direction of flow near the center of
the facilities area so that approximately one half of the runoff is
diverted to the north and the other half to the south. Each end of the
diversion will flow into adjacent unnamed natural drainages that
eventually flow into Chandler Creek.
In the mine facilities area, two temporary collection ditches will collect
and route disturbed area runoff to Pond 1. These ditches will be
designed and constructed to safely pass the peak flows resulting from
a 10 -year, 24 -hour storm event (north ditch) and a 100 -year, 24 -hour
event (south ditch). .
Sediment control for disturbed areas that are small, where surface
runoff cannot be feasibly diverted to a sediment pond, Northfield will
propose a sediment control plan involving a request for a small area
exemption. Applicable small area exemptions will include the
ventilation shaft sites and topsoil stockpiles. Drainage and sediment
control for these areas will include berm or ditch structures to divert
surface run -on, berm or ditch structures to collect runoff, and a filter
system such as silt fencing, straw bales, or gravel to minimize
additional contributions of sediment to undisturbed areas.
Culverts will typically be used where roads or equipment travel areas
cross drainage ways. The mine haul road will have culvert crossings at
the intersection of the south collection ditch and culverts or concrete
box structures at the Chandler Creek crossing. Additional culverts in
the facilities and adjacent areas will be designed, installed, and
maintained to safely pass runoff from storm events.
Upon completion of mining, all temporary diversions, collection ditches,
berms, and culverts will be reclaimed by grading of the areas to blend
with surrounding undisturbed and reclaimed areas, replacing topsoil,
and regevetating all related disturbance. All proposed ditches, with the
2.05.3 -26 Revised 12/04/09, TR -01