Independent Review of MSHA's Actions at Crandall Canyon Mine

though Owens conducted on-site evaluations of mining activities in both the North and
South Barriers, those investigations took place during development mining. It would be
prudent, in order to evaluate the additional abutment loading from pillar extraction, to
also observe pillaring operations. When pillaring operations began on the North Barrier
section on February 16, 2007, there was a roof control specialist assigned to the Price Field
Office, yet Owens did not assign him to observe retreat operations. In addition, neither
Knepp nor Davis questioned the lack of on-site observation of retreat mining operations.
In keeping with the intent of the four-stage plan approval process, an evaluation of
pillaring operations in the North Barrier section should have been used as a basis for
determining approval of pillaring in the South Barrier section. Furthermore, knowledge of
the March bounce event raised the need for observation of pillaring to an even higher level,
but such observation never took place.
Conclusion: To adequately evaluate the retreat mining process of a four-stage approval, an
on-site investigation should have been conducted while retreat mining was ongoing. The
failure of District 9 to observe pillaring operations in the North Barrier section was a missed
opportunity to obtain valuable information concerning approval of pillaring in the South
Barrier section.
Recommendation: An on-site investigation should be conducted of each phase of all unique
or non-typical mining plans.
5) Contradictions between approved plans and supporting data submitted to justify
approval. According to Owens, recommendations made by AAI were used to justify
approval to mine the North and South Barriers. However, several of the recommendations
made in the April 18, 2007, report were not implemented into the June 15, 2007, approval
for pillar extraction in the South Barrier section.
In the April report, AAI recommends that the pillars be lengthened by 37 feet. However,
the site-specific plan approved in March for development of the area was not modified to
reflect the new recommended pillar size. Although the new pillar size was implemented
by mine management, the lack of a plan change meant that it was never a requirement to
do so.
AAI concluded that skipping pillars, or leaving pillars unmined, contributed to the March
10 th bounce in the North Barrier section, and emphasized the importance of this with the
statement in the April report that, “skipping pillars should be avoided in the South Barrier,
particularly under the deepest cover.” This recommendation was not reflected in the roof
control plan. The impact of skipping pillars was not examined by the District (no modeling
of this aspect was undertaken), nor was the aspect of “deepest cover” defined in any
manner. In fact, Owens required three full rows of pillars to be skipped around the sump
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