20210903PAC to PIIC Attach 77-3 Addendum 3 Changes to Booklet.pdf

PACIFICORP
ENERGY WEST MINING COMPANY
DEER CREEK MINE MSHA ID NO. 42-00121

Mill Fork Access #2 Mains
Rilda Canyon Portals 1st Right Submains
Proposed Bulkheads – Installation and Monitoring Plan

Addendum #3 – Booklet Replacement

Addendum #3 – Booklet Replacement

The reason the entire booklet was replaced was due to the relocation of the 1st Right Bulkheads
from XC-28 to XC-4. The following lists the edits required:
Text Section:
Remedial Approaches to Containing Potentially Elevated Iron Water
• Page 8
o Number of bulkheads change from 9 to 11
• Page 9 o Second paragraph – elevation and pressure related to 1st Right XC-4
Existing Conditions
• Page 9 o Last paragraph – distance to second mining
Bulkhead Stability
• Page 10 o Table 2 – revised safety factors for 1st Right

Construction Location and Impoundment Area
• Page 14 o First paragraph – location of 1st Right bulkheads

Bulkhead Construction Sequence
• Page 15
o Construction sequence details related to 1st Right

Construction Details
• Page 17
o Last paragraph - states that the 3rd North B seals (mine separation seals)
would be constructed simultaneously with the bulkheads. This is no longer the case. MSHA District 9 approved the 3rd North B seals on April 1.
Ventilation changes in the mine will be effective 4/2/2015. Construction and
pumping of 120 psi rated seals at the 3rd North Mains crosscut #138 location
will start on Monday morning April 6th, 2015.

Rilda Canyon Concrete Plugs
• Page 17 o Section revised – includes design formula
Appendices:
Appendix B
• Revised to include drill hole near 1st Right XC-4
Appendix C
• Revised to ARMPS revised 1st Right XC-4 analysis
Appendix E
• Revised to include photos of 1st Right XC-4

Figures and Maps:
• All figures and maps were revised to reflect the relocation of 1st Right bulkheads