2024-08-29_PERMIT FILE - C1980007 ‎(2)‎

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 8/29/2024
• Doc Name: 2.05-15 Thru 2.05-49
• Section_Exhibit Name: 2.05.3 Operation Plan - Permit Area
• Media Type: D
• Archive: No

West Elk Mine

2.05-33 Rev. 06/05, 01/06, 03/06, 04&05/06- PR10; 01/09- MR350; 04/09- TR116; 05/09- MR354; 08/09- TR119; 5/20- MR443;
10/20- MR450; 10/21- MR456; 6/24-TR156
water is pumped up to the overhead conveyor and gravity fed through pipes into the existing MB-3
sediment pond. The tanks and piping were designed for the 50-year 6-hour storm.

The RPE area has also been treated independently of the other surface facilities. The RPE area is
located to the east of the lower refuse disposal area and east of Sylvester Gulch. The sediment pond
has been designed to completely contain the runoff from a 100-year, 24-hour storm event. The
design detail for this pond, the clean water diversion ditches, and sediment ditches can be found in
Exhibit 70.

DCW-2, the ditch immediately south of the haul road above the Lower Refuse Pile, serves as the
clean water diversion ditch for the Lower Refuse Pile (LRP). It diverts undisturbed runoff from
flowing over the LRP area and diverts it to sediment pond MB-5E. Runoff from the Lower Refuse
Pile is collected in perimeter ditches D2R-1, D2R-1a, and D2R-3, which are all sized for the 100-
year, 24-hour storm event.

During construction of the West Elk Mine, a spring was located on the site where the substation was
to be built. In order to stabilize the substation pad, a french drain system and collection pipe were
constructed to dewater it. As shown in Exhibit 43 and on Map 54, a 6-inch PVC pipe collects the
water and drains it into culvert C1-6A. MCC has designed and constructed several other french
drains around the mine site, as approved by the CDRMS, to improve stability. These french drains
are shown on Map 54. Sediment traps were constructed below the breaker building to pre-treat
(i.e., settle) wash-down water prior to flowing down to pond MB-2R. The locations of these
sediment traps are shown on Map 54. MCC also utilizes sediment traps above the inlets to ponds
MB-3 and MB-4.

General Requirements for Sedimentation Control Facilities

All storm drainage/sediment control ponds have been designed in accordance with the requirements
of the CMLRB Regulations for Coal Mining. In addition, all inspection, construction and
maintenance procedures conform to the requirements of these regulations. Flow meters have been
installed on all mine water intakes and discharges to measure flows.

Sedimentation ponds MB-3, MB-4, MB-5E, SG-1 and RPE ponds have gated dewatering systems
located above the sediment level. Refer to the designs in Exhibit 43, 47A, 48 and Exhibit 66. The
dewatering system for SG-1 is shown in Exhibit 66.

Sedimentation Pond Operation

The following discussions describe significant features associated with and the operations of
each of the sedimentation and water storage ponds located at the West Elk Mine. MCC typically
collects a pre-discharge sample from the sediment ponds to determine if the discharge will be in
compliance with MCC’s NPDES permit, prior to opening the gate to discharge the pond. The
pre-discharge sample is typically analyzed for total suspended solids.

MB-3