Independent Review of MSHA's Actions at Crandall Canyon Mine

that the proposed retreat sequence in Main West will be successful in terms of ground control,
even under the deepest cover (2200 feet).”
The District 9 engineer assigned to review the AAI reports began his MSHA career in 2004 as a
co-op student while still attending the Colorado School of Mines. In May 2006, he graduated
with a Bachelor of Science degree in mechanical engineering, and in June 2006 was assigned to
the District Roof Control Branch. The engineer reviewed both AAI reports and then
conducted his own ARMPS analysis. A LAMODEL analysis was not conducted by District
personnel, nor did they request assistance from MSHA’s Technical Support Roof Control
Division.
Upon completing his review and subsequent ARMPS analysis, the engineer identified five
“inconsistencies” with the AAI reports. Even though a formal retreat mining proposal had not
yet been submitted in the form of a roof control amendment, the District responded with a
letter dated November 21, 2006, to the operator in which the five inconsistencies were
outlined. This letter described a “preliminary analysis for projected pillaring” of the barriers
to the North and South of the Main West section and stated that, “the plan, as is currently
written, would not be approved.”
MSHA did not receive a written response to the November 21 st letter, as normally would be
expected to address deficiencies. Rather, the five inconsistencies were reportedly resolved in
December 2006 via phone conversations between mine personnel and Owens.
On November 13, 2006, District 9 received a formal plan submittal requesting approval to
develop room and pillars in the North Barrier block of Main West. On November 21, 2006,
Davis approved this site-specific amendment to the roof control plan. This plan specified
development of the North Barrier with four entries on 80-foot centers and crosscuts on 90-foot
centers. The submitted mining layout would result in a 135-foot wide barrier between the No.
4 entry and the longwall gob area to the north, and a 55-foot barrier between the No. 1 entry
and the old Main West to the south. The amendment included a statement that, “Consultant
reports indicate the planned development will avoid the majority of the side-abutment stress
transferred from the adjacent longwall gobs.” Additionally, the plan stated that, “during
development of the north barrier, conditions will be monitored to determine the possibility of
pillar extraction,” and if they appear favorable, “further discussions and plans will be
submitted for approval.”
On December 1, 2006, AAI personnel conducted an on-site evaluation of conditions in the
North Barrier development mining section. This visit was used to help determine the
feasibility of retreat mining in the area. At this time, the face location was in the vicinity of
crosscut 123, under approximately 1800 feet of overburden. The entries had been advanced
approximately four crosscuts inby the seal location of Main West, which was sealed upon the
completion of mining in 2004. AAI’s December 8, 2006, report of this investigation concluded
that, “roof, floor, and rib conditions were consistent with analytical predictions.”
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