20210903PAC to PIIC Attach 77-3 Addendum 4.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 #4

Revised Emergency Response Plan due to Installation of the Mine Separation Seals at 3rd North

Addendum Submittal April 10, 2015

Mine Safety and Health Administration, District 9
Deer Creek Mine 42-00121
Bulkhead Application – Addendum #4
April 10, 2015 Page 1

Addendum #4
Revised Emergency Response Plan due to
Installation of the Mine Separation Seals at 3rd North

In preparation for bulkhead construction, mine closure will effectively split the mine into two
distinct districts: the southern district, which will be sealed immediately by completion of the
mine isolation seals located at 3rd North B XC-138, Meetinghouse Canyon breakouts, and the
Deer Creek portals and the northern district, where bulkhead construction will take place. The
northern district will be sealed with the completion of the bulkheads, concrete plugs and sealing
of the Rilda Canyon Left Fork portals.
With the completion of the mine separation seals at 3rd North B XC-138, the northern portion of
the Deer Creek Mine will be ventilated with the exhausting fan located at the Left Fork Portals in
Rilda Canyon (Deer Creek mine separation amendment was approved by MSHA District 9,
4/1/2015. Ventilation changes in the mine were made effective 4/2/2015. Construction and
pumping of 120 psi rated seals at the 3rd North B Mains crosscut #138 location commenced on
April 6th, 2015). Access to the northern district during the construction of the Mill Fork
bulkheads will be through either the Rilda Canyon Left Fork or the 1st Right portals. The
approved separation of the mine ventilation system provides physical access to the bulkheads
post construction for monitoring prior to final sealing of the Left Fork Portals (Energy West’s
original application dated January 20, 2015 included constructing to the extent possible both sets
of bulkheads with no access to monitor the primary set during the construction of the secondary
set).
With the mine separation seals in-place at 3rd North B Mains crosscut #138, access for
construction and monitoring of both the primary and secondary bulkheads no longer is restricted.
The construction sequence has been modified to allow access for monitoring both sets of
bulkheads. After the completion of the Mill Fork Bulkheads, the next phase will be the
installation of the portals plugs at the Rilda Canyon 1st Right portals. Ventilation circuits will be
modified to ventilate 1st Right Submains utilizing the Left Fork exhausting fan during the
installation of the plugs.
In a continued effort to mitigate and limit impacts of hydrology to Rilda Canyon, Energy West
has contracted REI drilling, a company specializing in horizontal drilling techniques, to drill a
horizontal hole in the Rilda Canyon area from the Left Fork mine workings to the Right Fork
mine workings. The purpose of the hole is to drain by gravity, potential water leakage from the
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Mine Safety and Health Administration, District 9
Deer Creek Mine 42-00121
Bulkhead Application – Addendum #4
April 10, 2015 Page 2

primary set of bulkheads located in the Mill Fork/Rilda Canyon area to the southern portion of
the Deer Creek Mine. From the outflow end of the hole, intercepted groundwater will flow by
gravity to the Deer Creek portals. The horizontal hole will be started in the Blind Canyon seam
in 10th West Mains near the Left Fork portals drilled in a 5,000’ radius arc trending slightly
upward connecting to the Hiawatha seam in 1st Right Submains. Energy West is confident in its
efforts to install bulkheads at strategic locations to mitigate potential hydrologic impacts to Rilda
Canyon. If the horizontal hole is successful, static pressures at the 1st Right bulkheads would be
reduced dramatically.
With the mine separation seals in-place at 3rd North B Mains crosscut #138, access for drilling
operations will be from the Left Fork portals. The construction sequence of the bulkheads
outlined above will allow access to the drill site area (10th West Mains) and the breakthrough
point in 1st Right. After the completion of the horizontal drilling operations, the final phase of
Deer Creek closure will conclude with the construction of portal seals at the Left Fork portals.
The Emergency Response Plan section of the plan was enhanced and outlines the detail actions
taken if certain criteria occur, such as failure of head pressure monitoring equipment, rapid
changes in head pressure, seismic activity, excessive leakage or increase in leakage without
increase in head pressure.

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