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6.4.7 Exhibit G -Water Information Construction of the drain systems, slurry walls, reservoirs, and pond is expected to affect surface and groundwater systems. However, approved measures will mitigate the impacts of these changes. The drain systems around the slurry walls will be designed to mitigate the groundwater impacts of the slurry walls. At reclamation, major storm flows will be routed around the reservoirs by engineered trapezoidal channels. The "BokelmanM/alters Pit Groundwater Modeling and Perimeter Drain Design Report" is provided as Attachment G-1. This report addresses groundwater issues and mitigation for the mining operation and reclamation conditions. For the purpose of enabling dry mining, pore water will be pumped from within the confines of the slurry wall (Phase I -Cells 1-3). Cell 4 will be dewatered by allowing pit walls to drain to a dewatering trench which will then be pumped to a sediment pond. The sediment pond will discharge to the river through an overflow pipe. Dewatering pump rates are expected to be in the range of 400- 500 gpm. Phase II will include building a slurry wall around all mining Cells (1-3). A Substitute Water Supply Plan (SWSP) was submitted to the Office of the State Engineer on February 8, 2007 by Bishop Brogden and Associates which addresses water rights impacts of the operation. Surface Water Onsite and surrounding water features are shown on Exhibit C-1. The major surface water feature is the Big Thompson River that flows to the east, directly north of the site. The Hillsborough Ditch runs just south-southwest of the property. LRM owns shares in the Hillsborough Ditch that have historically been used to irrigate the property. An existing concrete-lined irrigation ditch occurs at the south boundary of the west permit area. This ditch will be kept active for the purpose of irrigating the reclamation revegetation effort. During mining, surface water may be affected by precipitation intercepted by the pits. Any intercepted water will be pumped from the pits to sedimentation ponds for infiltration, evaporation and direct flow to the river. At reclamation, stormwater flows will be routed around the reservoirs and ponds to the Big Thompson River via aman-made trapezoidal channel(s) with "grouted sloping boulder drop structures" or rip-rap lined. Ground Water The subsurface water table is characterized by a shallow, unconfined aquifer that exists onsite and on properties adjacent to the proposed site. A subsurface test February 20, 2006 Bokelman/Walters Pit Page 17 of 36 Regular 112 Permit Application