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Memo to Dan Mathews <br />Observations re: Powderhorn Coal Field Visit <br />page 2 <br />Refuse Disposal Area #2: <br />You expressed concern during our tour concerning the ultimate top surface configuration of <br />RDA#2. The upper most facial slope and top surface is still actively receiving waste and has not <br />been subsoiled or topsoiled. The existing and approved final configuration of the top-surface <br />slopes towards the outslope face. Your concern, as I understand it, is that if (or when) the up <br />slope diversion is compromised by mass wasting of the steep undisturbed slope above it, the <br />resulting tlow across the pile will breach the crest of the facial slope and expose, or release, <br />refuse. This is a valid concern. <br />As we discussed at the site, [believe your proposal to regrade the top surface to drain into the <br />slope would delay, if not prevent, the eventual incision of the facial crest. The existing <br />reclamation plan was, however, approved. Powderhorn Coal can elect to effect the plan and <br />accept the liability of repairing any damage which occurs within their liability period. In order to <br />encourage Powderhorn Coal to revise it's approved plan you will have to demonstrate that the <br />plan is unacceptable or convince them that it will be more cost effective for them to regrade the <br />top of RDA#2. Demonstrating that [he traditional approach is unacceptable at RDA#2 might put <br />several dozen other approved refuse pile reclamation plans in some doubt. In summary, I don't <br />disagree with your concern regarding RDA#2, but I am concerned about the sensitivity of the <br />issue. <br />The Coal Canyon Channel Geomorphology Quandary: <br />A question has arisen regarding the reach of Coal Canyon Channel which was relocated by <br />Powderhorn Coal. For purposes of brevity I will attempt to greatly simplify this discussion. <br />Powderhorn Coal received permission to relocate the channel in connection with the construction <br />of RDA#1. The regulations require that a relocated channel be "nonerosive". In hind sight I now <br />realize that Division personnel have interpreted this to mean absolutely not erosive, which at <br />times may have been over zealous and geomorphologicallyirnpractical. It is now my opinion <br />that we should interpret this requirement to mean, "not any more erosive than the natural regime <br />of the original channel and in equilibrium with the goemorphological regime of the relocated <br />channel". The creation of a relocated reach of channel which is out of equilibrium with the <br />natural regime will result in frustration, damage to the environment, and infinite maintenance <br />liability. <br />In the specific case of Coal Canyon Creek, the method intended to render the relocated channel <br />nonerosive was the installation of check dams comprised of large erratic boulders. It was <br />assumed that this would lower the gradient between the check dams to mimic the undisturbed <br />gradient of the longer natural channel. Tn fact, the check dams have served to accelerate <br />