2007-01-31_REVISION - M1986015 (2)

Home Browse Search

is finished. The sealing would create a "shadow" east of the sealed area that would extend some distance. Thus, [he new plan for Phase 1 will help prevent [ha[ shadow. But this plan for Phase 1, interestingly, would also help wells west of the site. (To aid in understanding the following please refer to Exhibit C-3A.) As a further aid to supplying water to surrounding wells, the slurry wall originally proposed for Phase 1 has been eliminated from the plan. Instead, Phase 1 will become a series of large sediment basins which will be filled primarily with wash fines and overburden. These wash fines retain a considerable amount of water, but they also slowly release [his water into the surrounding groundwater system. In effect, once Phase 1 is completely backfilled it will act in two ways relative to 25'" Lane. First, it will be asemi-permeable blockage that will allow the rate of flow through [he 25`" Lane area to decline somewhat. That will help maintain the supply coming around the north side of the Phase 2 groundwater barrier wall. But the water contained in [he Phase ]sediment basins will also spread from that area to the 25`" Lane area if the water level on 25'" Lane declines below the water level in the backfilled Phase I area. Although on the surface that is uphill, with respect to the groundwater gradient, it would be downhill. If [he water level on 25`" Lane remains higher than [he water level in Phase I then the water will flow from [he 25'" Lane area into [he backfilled Phase I area as well as down the corridor between Phase (and Phase 2. Requirement: Backfilling of Phase 1 will be done in full consideration of maintaining water flow to [he east, as well as backing up some of the flow to the west to help supply 25'" Lane wells, and ultimately produce an environment suitable for establishing a riparian forest over much of the Phase 1 area. DISCUSSION: The sediment basin approach avoids excessive evaporative losses after reclamation, maintains flow [o [he east, and backs up water somewhat to the west, and, in the reclamation, will ultimately provide an excellent substrate for the development of a rich riparian forest. This type of forest is declining throughout eastern Colorado and as a result [ha[ decline is having major impacts on 1 wildlife populations, particularly birds. This approach will allow the development of a valuable habitat where none existed previously. For more information on this aspect of the plan, please refer to Exhibit E - Reclamation Plan. Requirement: A groundwater barrier wall will be installed around Phase 2 as shown on [he maps prior [o mining Phase 2. The only land [ha[ may be mined in Phase 2 prior to installing the groundwater barrier wall will be that area in the northeastern corner of Phase 2 which is outside the area bounded by the groundwater barrier wall. Pueblo East Pit Amendment 3 (2007) Exhibit D Page 17 of 34