Independent Review of MSHA's Actions at Crandall Canyon Mine

Plan Approval History for Mining in the North and South Barriers
Crandall Canyon mine management first approached MSHA District 9 personnel in April 2006
about the possibility of mining the barriers surrounding Main West. This initial contact did
not consist of a formal written proposal, but rather was part of a discussion with Allyn Davis,
District 9 Manager, and Billy Owens, District 9 Roof Control Branch Supervisor, during a
meeting concerning issues with another mine owned by Andalex Resources, the parent
company of Genwal Resources, Inc. At that time, Owens informed mine management that a
proposal with supporting data would be necessary in order to evaluate the possibility of
mining in the barriers. In a September 2006 meeting with MSHA, mine management
submitted the requested supporting data in the form of two reports from Agapito Associates,
Incorporated (AAI), a consulting firm hired by the operator. A formal request for a roof
control plan amendment was still not submitted to the District at this time. Following this
meeting, Owens informed the mine operator that, upon satisfactory evaluation, plans for
mining in the North and South Barriers of Main West would only be approved in stages.
Development and retreat mining in each barrier would be approved separately, with each
approval contingent upon the successful completion of the preceding stage.
Upon receiving the consultant’s reports, Owens assigned an engineer on his staff to conduct a
review of the submitted information. The AAI report dated July 20, 2006, described an
analysis of the proposed barrier mining which primarily used LAMODEL, a numerical
modeling program developed by the National Institute for Occupational Safety and Health
(NIOSH). LAMODEL is a boundary element program used to determine stress and
convergence levels which are then used to predict ground conditions. The AAI analysis
attempted to calibrate the modeling effort by first using the LAMODEL program to simulate
historical mining in the 1 st North Left area of the Crandall Canyon Mine. After this calibration
effort, LAMODEL was then used to approximate conditions as the proposed barrier mining
took place. The report concluded that, “the proposed Main West 4-entry layout with 60-foot
by 72-foot pillars should function adequately for short-term mining in the barriers,” and that,
“Model results indicate that planned mining in the barriers will avoid the majority of the sideabutment
stress transferred from the adjacent longwall panel gobs.”
The second of the two reports submitted to MSHA in September 2006 was a copy of an August
9, 2006, AAI e-mail to mine management. This report included an additional analysis using
the NIOSH software program Analysis of Retreat Mining Pillar Stability (ARMPS). ARMPS is
an empirically based method for determining pillar stability. The same 1 st North Left area of
the mine that was used to calibrate the LAMODEL program was used to calculate an
acceptable ARMPS stability factor (SF) for the Crandall Canyon Mine. The AAI analysis
concluded that retreat mining in this area was, “generally successful with a SF of 0.37. “ AAI
rounded the SF up to a minimum of 0.40 as, “a reasonable lower limit for retreat mining at
GENWAL.” The AAI analysis concluded that, “the lowest SF for the proposed retreat
sequence in Main West barriers is 0.53 under the deepest cover…,” and that, “implications are
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