2022-07-08_PERMIT FILE - C1981019A ‎(2)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 7/8/2022
• Doc Name: Performance Standards
• Section_Exhibit Name: Volume 15 Rule 4
• Media Type: D
• Archive: Yes

RULE 4 PERFORMANCE STANDARDS

Collom – Rule 4, Page 5 Revision Date: 6/20/22
Revision No.: MR-242
Collom Pit area, as needed for mine operations (please see Exhibit 7, Item 23, Part A) . A system of
clean water diversion ditches upslope from the mining activities will be constructed to divert surface
runoff away from the disturbed areas (Collom Pit). These temporary diversions will be constructed to
pass at a minimum the runoff from the precipitation event with a two-year recurrence interval.

Any topsoil stockpile areas that may be constructed outside the confines of engineered sediment control
structures will be required to have a perimeter ditch and berm constructed around the entire footprint of
the stockpile sufficient to capture and retain any rainwater/snowmelt that may be generated from the
stockpile area to preclude loss and/or contamination of the topsoil resource. A demonstration of the
effectiveness of sediment control structures to be constructed around several topsoil stockpiles planned
outside of primary sediment control may be found under Exhibit 7, Item 23, Part D.

4.05.4 Stream Channel Diversions (Relocation of Streams)

The drainage and sediment control measures described under Section 2.05.6 and presented in the Erosion
and Sedimentation Control Plan (Exhibit 7, Item 23) will provide for temporary diversion of surface
drainages within the permit area, as needed for mine operations. A system of temporary ditches will be
used to divert runoff from disturbed areas to sediment ponds. The natural drainage systems will be
restored to historic drainage patterns once diversion ditches are removed; therefore, there will be no
permanent diversions of these channels.

The only stream channel that will be impacted by the Collom Pit is the main stream of Little Collom
Gulch, an ephemeral stream draining less than one square mile at the upstream pit boundary. Clean water
diversions will be installed above the Collom Pit (Exhibit 7, Item 23, Part A) and will be removed as
mining progresses. It will also be channelized further downstream, alongside the haul road leading from
the Collom Pit to the spoil pile, where it drains greater than one square mile (Exhibit 7, Item 2, Part B).

4.05.5 Sediment Control Measures

Sediment control measures to be implemented are shown in Exhibit 7, Item 23 Erosion and Sedimentation
Control Plan, and postmining channels are shown on Map 41B. These facilities, consisting primarily of
diversion ditches and sedimentation ponds, will be located, constructed and maintained to avoid erosion
and increased contribution of sediment load to runoff.

Facilities to control sediment are typically installed in areas above and/or below the planned sites of
disturbance. “Upstream” facilities, such as clean water diversion ditches upslope from the mining
activities, serve to divert runoff away from the disturbed areas. Temporary diversion ditches below the
disturbed area of the pit will help collect runoff from disturbed areas and route it into the sedimentation
ponds. During active mining, the mining areas will aid in retaining sediment within the disturbed areas
by catching water in pits, small depressions and dozer basins, etc. Once reclaimed, the basins will drain
as they did prior to mining activities (i.e., historic drainage patterns will be re-established).

All temporary diversions will be removed and reclaimed when no longer needed for sediment control in
accordance with Rule 4.05.2(2)

Channel lining rock riprap and energy dissipaters will be used when necessary. As stated above, all
temporary diversion structures will be seeded and revegetated after removal. Colowyo does not anticipate
that there will be any significant excess material resulting from the construction of diversion ditches.

None of the diversions will drain into underground mines.