Independent Review of MSHA's Actions at Crandall Canyon Mine

Rocprops were chosen by the operator due to their capability to be pressurized between the
roof and floor, thus making them an active support. Rocprops had been used by the
company at its Aberdeen Mine for rib protection in bounce-prone, longwall headgate entries.
Chain link fence and one wire rope were used in conjunction with the Rocprops at the
Aberdeen Mine. The wire rope was either wrapped around the coal pillar or anchored in some
manner in the crosscuts to prevent the Rocprops from being dislodged in the event of a
bounce. However, at the Crandall Canyon Mine the wire ropes could not be wrapped around
the coal pillars and were anchored only on one end in the outby crosscuts due to the blockage
from the coal rubble. Three wire ropes were used to secure each Rocprop to the adjoining
Rocprops, which essentially tied them together.
Timbers with “Jackpots” were installed in the No. 1 entry in appropriate areas where
additional supports were needed in areas outby crosscut 120. Jackpots are supplemental
devices placed between a timber and the roof and expand as fluid is pumped into them
through a pressure relief valve to provide some measure of positive support. Rocprops
were used exclusively beyond crosscut 120 to provide lateral support as rescue efforts
advanced up the No. 1 entry.
As work progressed in the No. 1 entry, the method of pressurizing the Rocprops was
changed. Initially, a scoop’s power take off (PTO) was used to drive a booster pump to
increase the water pressure to 1100 psi. Later, booster pumps were mounted on the
continuous mining machine and roof bolting machine so they could be used when in the face
area. This accelerated the installation process by eliminating the need for another piece of
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Inner Tube
Wedge
Outer Tube
Loading Nozzle