Independent Review of MSHA's Actions at Crandall Canyon Mine

equipment to tram in and out of the single entry. While the company’s suggested installation
set pressure of 1100 psi was a significant increase from the 400 psi to 800 psi range at which
Rocprops are typically set in District 9 mines, it was never determined if 1100 psi was the
appropriate pressure to use in this situation. Neither MSHA nor the company contacted the
Rocprop manufacturer or distributor for a recommended pressure to use in this application.
A representative of the manufacturer later stated that a Rocprop could be installed at a
maximum pressure of just under 3000 psi. However, it was not known if the floor and/or roof
in the Crandall Canyon mine could have withstood a pressure higher than 1100 psi.
The mine roof was considered competent, and in most places the original support system was
still intact. The original roof support consisted of 5-foot long, 1-inch diameter resin bolts
installed six to a row, through wire screen. There were some areas in the No. 1 entry where a
layer of white sandstone above the coal seam had shifted during the bounce event and bent or
broke the previously installed roof bolts. As these locations were encountered, the mining
machine was trammed from the face to an outby crosscut and a roof bolting machine brought
in to replace the damaged roof bolts. Some of these areas were supported by installing steel Jchannels
against the roof, supported by the Rocprops set on both sides of the entry.
Loading of the coal in the No. 1 entry began on August 8 th after a conveyor belt tailpiece was
installed at crosscut 120 in the No. 2 entry. A remote-controlled continuous mining machine
loaded the coal into shuttle cars which transported the material to the dumping point at the
tailpiece of the beltline. Rescue efforts had advanced approximately 900 feet in the No. 1 entry
when, on August 16 th , at approximately 6:38 p.m., a bounce occurred. The bounce was just
outby the continuous mining machine and was so violent that it dislodged eight of the
Rocprops that had been installed on the right side of the No. 1 entry. The supports and a
substantial volume of coal from the right rib were blown across the entry, striking several
workers who were in this area, killing three and injuring six others. The underground recue
effort was discontinued after the victims were recovered and taken to the surface.
Independent Review Team’s Findings
Although the company proposed the use of the Rocprops and MSHA concurred, they were
not the only support considered. MSHA’s persons-in-charge considered and dismissed the
use of other support methods, such as steel arches, 3-piece steel square sets, and other standing
supports. Some of the systems were not readily available, would take much longer to install,
or would require additional entry width. In addition, some systems, such as steel arches and
3- piece steel square sets, are designed to withstand vertical loads, and have no positive roof to
floor pressure to withstand lateral forces. These systems would also require a wider area,
which conflicted with the desire to leave as much coal rubble as possible to provide lateral
confinement for the remaining pillars. Rocprops were considered the most viable option
due to their size, availability, speed of installation and ability to be pressurized between the
floor and roof. MSHA Technical Support specialists contacted Thomas Barczak, Senior
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