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Mathews, Dan ~` From: Dudash, Joe Sent: Monday, July 22, 2002 3:04 PM To: Mathews, Dan Subject: RE: drainage issues at Deserado Refuse Disposal Areas Concerning your first issue, my understanding is that the refuse pile needs designed (100 year-24 hour) interim ditches around the sides and the back of the pile. The idea is to get the water off of and away from the pile as quickly as possible, so that is why ditches are used for drainage from a refuse pile. Wth the current drainage configuration, the refuse pile runoff may eventually get to the pond, but the runoff water is moving slower than if a ditch was used. By moving more slowly around the refuse pile, the water is unnecessarily saturating the toe along the sides and back of the refuse pile, thereby possibly reducing slope stability. I agree with you that the refuse pile runoff does not need to go into the permanent ditch until final reclamation. About your second concern, I believe that Rule 4.09.2(5) refers to constructed waterways, not the dispersed drainage from a mound. However, it is Rule 4.09.2(7) that talks about diverting runoff off of the fill, using ditches. Again, the idea is to get the runoff off of the refuse pile as quickly as possible. I see Rule 4.09.2(5) and Rule 4.09.2(7) working in conjunction. Rule 4.09.2(7) requires water to be diverted off of the pile, but Rule 4.09.2(5) requires that the diversion directs the runoff to the side, not down the middle of the pile. The operator wants to have an alternative design but the rules don't seem to allow for any alternative design. The lack of alternative design rules suggests to me that the geo-technical experts behind the rule- making wanted runoff off of the refuse piles fast, due to stability concerns. The operator says that they are afraid of getting equipment stuck in the muck if they have to maintain ditches on the pile. Is it possible that the muck is present because they are allowing the runoff to flow slowly off of the mound, instead of quickly, with ditches? Also, the refuse piles seem to be rather flat on top. The outslopes may be 20-25 percent, but what percent slope is the main body of the pile at? Could this be contributing to the muck problem? Also, their drying operation may be contributing to the wet conditions on the pile. It appears that a lot of wet refuse material is drying on the pile. The wet refuse may be soaking into the underlying compacted refuse and rewetting it. In summary, I would think that ditches are needed across the face of the refuse pile to gef the runoff off of the refuse pile face and to the back and sides of the pile as quickly as possible. Then, lateral and back ditches would quickly direct the runoff into the pond. The operator may have to alter the operation of the pile to allow for maintenance of the ditches. -Original Message- From: Mathews, Dan Sent: Monday, July 22, 2002 12:57 PM To: Gorham, Kent; Dudash, Joe; Baulay, Mike; Walker, Byron Cc: Brown, Sandy; Berry, David Subject: drainage issues at Deserado Refuse Disposal Areas Kent, Joe, Mike and Byron I would like to request your input regarding some refuse area drainage design issues at Deserado. The Deserado refuse areas are in rolling sagebrush country northeast of Rangely. Currently, there are three refuse "sub-areas", RP- 1 which is fully reclaimed, RP-213/4 which is active, nearing completion, and RP-5, which is active, in early stage of development. Each refuse sub-area is contained within a small (20 to 40 acre), bowl shaped watershed, that drains gently to the north. The pile final designs are basically crowned mounds, with 20% to 25%outslopes, without terraces or benches. RP-1 was reclaimed in the early 1990's. It appears to be stable, with nc erosion and more or less blends into the surrounding terrain. The two active piles were initiated during the early 1990's, althouth Pile RP-5 has been used only sporadically until the last year. The three piles share the basic features described, but there are some differences with respect to detailed designs. The questions I have are focused on RP-5, which is at an early stage of construction, such that some basic design modifications would still be feasible. During initial site development a sediment pond was constructed immediately to the north of the refuse site, at the Tower end of the watershed. A permanent, 100 year design ditch with riprap and vegetated segments was constructed just below the ridge crests along the perimeters of the watershed, concurrent with sediment pond construction. Design was such that the toe of the refuse pile side slopes would drain into these permanent design ditches. During early phases of pile construction, the pile was used intermittently, and refuse was spread in a thin veneer throughout the entire footprint of the pile area. The perimeter ditches along the sides of the watershed were at a higher elevation than the refuse, such that runoff across the compacted refuse generally was to the north, with