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August 23, 2004 Page 2 of 3 Pages not been determined. At this stage of review of the Collom Project, the Division cannot approve a proposal for a valley fill in Little Collom Gulch, as we have not been provided any information, such as swell factors or proposed post-mining topography maps, demonstrating that a permanent excess spoil valley fill is necessary. 3.1 Groundwater The plan for four bedrock monitoring locations, as identified on Plan 2 (July 2004) and in Table 3.1, appears satisfactory, assuming there is adequate monitoring of stratigraphic intervals that aze completed in any of the nearby water supply wells (State Engineer Permits 175218 and 175219). We suggest a fifth bedrock monitoring site in the SE '/. NE '/. Section 1 T3N R94W, east of the eastern edge of the life-of--mine footprint. We additionally encourage locating one of the four currently-proposed bedrock sites where the flow path of a coal spoil leachate plume would most likely occur, as a groundwater monitoring well would eventually be needed at such a location during active mining. The work plan (Table 3.1) needs to be revised to provide information on either the stratum immediately below, or on any aquifer that may be adversely affected by mining below, the lowest coal seam to be mined. The information required is described in Rule 2.04.6(2)(b)(i)(A) through (E). Alluvial. We have not yet completed our review of alluvial ground water and alluvial valley floors. Please provide us with a copy of the studies by Dames and Moore and JBR Environmental Consultants referred to in the plan to assist us in this review. 3.2 Surface water hydrology The location of alluvial valley floors and the spatial extent ofmining-related surface disturbances may have a bearing on the location of baseline surface water monitoring stations. Such disturbances could include topsoil stripping and overburden removal azeas, facility support azeas, excess spoil piles or fills, sedimentation ponds and ditches, etc. Therefore, the proposed locations of baseline surface water monitoring stations aze adequate at this stage of the Collom project, though additional baseline and operational surface water monitoring stations may be required as the extent of surface disturbance becomes more defined. Consideration might be given to relocating the Lower Straight site further downstream so as to be below the reach of potential impacts from activities in the western-most phase of mining. We additionally recommend a baseline surface water monitoring station on lower East Fork Jubb downstream of the eastern-most phase of mining. Baseline surface water monitoring sites on Wilson Creek, upstream and downstream of potential impacts from activities in the eastern-most phase of mining, may be required at some future date.