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• <br />EXHIBIT 7, ITEM 23, PART B <br />Little Collom (LCX -IN) Sump Design <br />The location of the Little Collom Sump is presented on Exh. 7 -23, Figure Al. Formerly, this <br />structure was referred to as the LCX -IN (Little Collom X Incised) structure, and the modeling <br />presented in Part A of this section still references that name. <br />This pond will be built before any other mining or construction activities occur. Construction of <br />this pond needs to be concurrent with the construction of the Little Collom Pond located <br />downstream. <br />This structure will be constructed at or near the base of the X4 coal seam. This large sump will be <br />entirely below grade with minimal embankment. Thus it will be the lowest point in the area; the <br />impoundment will be evacuated by pumping. SEDCAD modeling for the initial mining case is provided <br />in Exhibit 7, Part A. <br />This pond will provide the majority of sediment control for the Collom mine plan. It is located near the <br />downstream toe of the Temporary Spoil stockpile. <br />The design drawing for the pond is presented in Exhibit 7, Item 26, Figure 2. Total capacity of the <br />impoundment is about 103 acre -feet. Total depth is about 32 feet. <br />• This pond will not provide ultimate sediment control; that function will be provided by the Little <br />Collom Pond located downstream. <br />• <br />This structure will remain in place throughout the life of Collom mine plan and will only be removed <br />concurrent with bond release of the upstream drainage area. <br />The following tables summarize the design details and SEDCAD modeling results as presented in Part A <br />of this section.. <br />Exh. 7 -23B -1 Revision Date: 12/15/10 <br />Revision No.: PR -03 <br />