2025-07-30_PERMIT FILE - C1981019 ‎(7)‎

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 7/30/2025
• Section_Exhibit Name: Rule 4 Performance Standards -ST
• Media Type: D
• Archive: No

RULE 4 PERFORMANCE STANDARDS

South Taylor – Rule 4, Page 10 Revision Date: 7/21/25
Revision No.: MR-267

The area to be mined will be restored to a topography approximating pre-mining grades. The slopes of
backfilled areas, as necessary, will utilize terraces and/or contour furrows for erosion control and stability.
These terraces and contour furrows will be constructed according to the requirements outlined in Section
2.06.2. Where applicable, Colowyo will retain all overburden and spoil on the solid portion of existing
benches. The final graded slopes will not exceed the approximate original pre-mining slope grade as shown
on the Map 19. Post-mining surface drainage channels will be located to minimize erosion and to minimize
slippage.

4.14.2 General Grading Requirements

The final graded slopes at the mining operation will not exceed the approximate original pre-mining slope
grade as shown on Map 19. Colowyo will retain all overburden and spoil material on solid portions of
existing or new benches. The final highwall at the operation will be eliminated by backfilling overburden into
the final pit area.

Small depressions of a holding capacity slightly greater than one cubic yard of water may be used to create a
moist micro climate to aid in shrub establishment. See Section 2.05.4, Planting and Seeding Methods for
further information regarding these small depressions. Also, several stock watering ponds will be constructed
to compliment the post-mining land use. Providing a supply of water is an integral part of the grazing post-
mining land use. Colowyo will not be mining on any slopes above 20° as shown on Map 18A.

Final grading before topsoil placement will be conducted in a manner that minimizes erosion and provides a
surface for the topsoil that minimizes slippage. Final grading will be accomplished so that overall grades will
not exceed lv:3h. The plan for backfilling and grading is shown graphically on the Map 29.

4.14.3 Covering Coal and Acid and Toxic Forming Materials

Colowyo will not have any exposed coal seams remaining at the end of mining and reclamation. Colowyo
does not have any acid forming materials at the mine. For discussion on acid- and toxic-forming materials,
refer to Section 2.04.6. For disposal of non-coal wastes or materials constituting a fire hazard, refer to Section
4.11.4.

4.14.4 Thin Overburden

Colowyo does not have a thin overburden situation as defined in Section 4.14.4 of the regulations.

4.14.5 Thick Overburden

Colowyo does not have a thick overburden situation as defined in Section 4.14.5 of the regulations.

4.14.6 Re-grading or Stabilizing Rills and Gullies

Please see Section 4.14.6 in Volume 1.

4.15 REVEGETATION REQUIREMENTS

4.15.1 – 4.15.7 Revegetation Requirements, Various

These sections are addressed in the Volume 1.