1988-06-20_GENERAL DOCUMENTS - C1981017

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r Mike Long - 2 - May 18, 1988 Don Frickle was concerned that some of the diversions visited may not be large enough to pass the required 100-year/24-hour event. He will complete his review of these permit specifics within the next several weeks. This issue relates to the current regulation modification dehate being continued by Candy Thompson with regulatory personnel of the OSMRE, regarding requiring diversions to accommodate 100-year/24 hour versus 100-year/6-hour event runoff. In the case of the Powderhorn pile, Don Frickle is also concerned that drainage from the southwestern portion of the top of the pile may not be captured by the ditches routing drainage to the sediment pond below the pile. I have indicated verbally to the OSMRE representatives that we would be willing to remedy a permitting flaw by requiring more detailed discussions of pile diversion designs in future permits. Waste Pile Configuration The waste piles at Deserado, Orchard Valley and Mt. Gunnison No. 1 seem to have passed muster. Don Frickle is checking the diversion sizing, but Lou Hamm appeared satisfied with the structural aspects of these piles. Bob Liddle reports that Cathy Welt, environmental representative for Orchard Valley, did state that they had not been conducting compaction testing for the past year, and that their engineer had inadvertently inverted the pile facial angles. As a result the slope angle of the pile faces at Orchard Valley is closer to 1 .5:1 than the specified design maximum slope gradient of 2:1 . However, these slnpes have already been topsoiled and vegetated. Both of these issues should have been caught during normal inspection and enforcement activities at the site. Lou Hamm's only concern expressed at the Coal Basin waste pile was his opinion that the terraces could be wider, which would increase the stability of the pile. This concern stems from an on-going opinion on the part of the OSMRE (Gary Fritz) that it is deleterious to allow Mid-Continent Resources to push snow over the crest and onto the face during winter Ronths. In a lengthy debate, I attempted to present the pros and cons of this consideration. (1 ) Snow and ice must be removed from the pile, as demonstrated by the unfortunate waste flows which occurred at the old waste pile on the opposite side of the valley during May of 1984. (2) Removal of snow by loaders and truck to a designated snow disposal area will only result in an ice pile which would never melt and wnuld require added disturbance area and additional maintenance considerations. (3) Insolation on the dark waste pile face appears to melt and sublimate snow fairly rapidly during the winter months. (4) The practice of pushing snow over the crest of the pile onto its face does result in some minor debris being deposited on the terrace benches. However, this problem can be remedied by regrading of the benches in early summer.