Angle of Repose
  The maximum angle from horizontal at which a given material will rest on a given surface without sliding or rolling. The angle of repose of a given surface however, is not always stable. According to a recent "Full Reclamation and Closure Plan" it is proposed that an angle of repose for Molycorp's waste rock dumps be "consistent with industry and regulatory practice...". Further, it states that "...all mine facilities are regraded to maximum slopes of 2H:1V and 3H:1V or flatter wherever possible." The mine's waste rock dumps are presently at angle-of-repose (steeper than 2H:1V) - so that it is almost impossible to add a soil cover in their current condition - and several may be unstable.
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