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Stipulation Number 5: EXHIBITS 6-7; 7-1; 7-2; 7-3; 7-4; 7-6; 10-2; Attachment 11-2, Map 1; 11-3; 13-2; Attachment 16-1, Figures 1, 2, and 3; 17-1; 17-2 WILL BE MODIFIED TO REFLECT THE APPROVED PERMIT BOUNDARIES AS DEPICTED ON ALL OTHER PERTINENT MAPS OF THE NUCLA EAST AREA. THE MAPS MUST BE SUBMITTED TO DIVISION OFFICES NO LATER THAN MARCH 15, 1989. With these stipulations, all requirements of the Act and these rules have been complied with. (2.07.6(2)(a)). Based on information contained in the permit application and other information available to the Division, the Division finds that surface coal mining and reclamation can be feasibly accomplished at the Nucla Strip Mine. (2.07.6(2)(b)). The Division finds that the operations proposed under the application have been designed to prevent damage to the hydrologic balance outside the proposed permit area. (2.07.6(2)(c)). Probable Hydrologic Consequences Ground Water The probable hydrologic consequences of mining to the around water system at the Nucla Mine will be confined to affecting shallow, localized bedrock aquifers. The effects to these regionally insignificant aquifers will be two-fold: disruption of ground water flow systems and formation of spoil aquifers. Initially, mining will interrupt flow through the overburden and coal aquifers. This will result in the re-routing of water from the ground water system to the surface water system via pit inflows and pumping to sediment ponds. Following backfilling, a single backfilled spoils aquifer will develop where there were originally two separate aquifers. Recharge from the spoils aquifer into the bedrock aquifers will result in a minor change in water quality. Water in the alluvium along Calamity and Tuttle Draws may be modified in quantity or quality both during or after mining. The underburden aquifer is not expected to be impacted by mining activities. These impacts are discussed in more detail below. The mining of Dits and their subsequent backfilling will disrupt the ground water flow system at the Nucla Mine site. The saturated thickness of the surficial Dakota Sandstone is dependent upon the recharge provided by the Lower Second Park Irrigation Ditch. Leakage and overflow from this ditch appears to be the most significant source of ground water recharge in this area. The coal aquifer also appears to be partially recharged by irrigation return flow. Peabody has predicted mine pit inflows at Nucla East utilizing two methods, the 1982 McWhorter analysis and the USGS three-dimensional finite-difference model, MODFLOW (Table 1). The McWhorter analysis predicted pit inflow volumes from current bedrock aquifer discharge while the MODFLOW model predicted pit inflow rates and annual drawdownsfrom ongoing bedrock aquifer discharge combined with corrections to model the additional recharge caused by drawdown. (As mining continues, ground water flow gradients will be directed -17-