2002-03-04_REVISION - M1986015 (8)

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RECLAMATION PLAN occurs to 100 to 150 feet from the river and then 200 to 300 feet of overburden is used to backfill the excavation all the way to bedrock, it is less likely the river would be capable of cutting through all that material before protective action could be taken to prevent the river from cutting into the slurry wall. With overburden backfill placed all along the south side of the reservoir containment, the side closest to any potential river channel changes, extensive protection of the slurry wall investment is achieved. Installation of the slurry wall is the same irrespective of whether it is placed in native or backfilled material. The slurry wall is installed to a width of three feet and as vertical as possible with the bottom keyed into the bedrock a few feet. The distance from the slurry wall to the top of the reservoir slope is kept at a minimum distance of 20 feet and the slope into the reservoir area is constructed to a maximum steepness of 3:1 and preferably closer to 4:1. These are the same specifications used for installation in native material which will be used where such is done. The only difference between slurry wall installation in native material and in backfilled overburden is the nature of the material on each side of the slurry wall. The slurry wall length is estimated to be 6227 feet. This is for the wall shown on Exhibit F-1. Because the actual extent of the backfilling process is not known with high precision and may vary somewhat from that shown on the map, the actual length of the slurry wall when installed may be somewhat greater or somewhat less than the length stated above and shown on Exhibit F-1. However, the layout shown on Exhibit F-1 is based on the best estimate of the amount o£ available overburden, the amount o£ waste to be generated in the processing, and the characteristics of the deposit structure where the overburden will be deposited. It is assured that in the southwestern and the southeastern corners of the site, the location of the slurry wall and the amount of backfilling will closely match that shown on the map, as a minimum. If there is insufficient backfill to create the entire layout shown on Exhibit F-1 then material will be taken from less critical locations and used in these two corners which are most exposed to the river channel and its possible changes. Therefore, deviations from the layout shown on Exhibit F-1, if they occur, will be in backfill areas away from the river meanders. Water -General Requirements Water consumption for this operation is currently covered in a Substitute Water Supply Plan (SWSP #M86016). When conditions are appropriate, and as directed by rules Pueblo East Pit Amendment Exhibit E Page 5