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Permit Revision Adequacy Comment Response <br />November 30, 2004 <br />Page 18 of 24 <br />After Underground Coal Mining, 1995 found that subsidence in 300-500 feet of overburden <br />MCC Response: Exhibit 60B was revised. <br />caused the stream to enter a fracture, drying up the stream bed below. Water quality was also <br />dramatically impacted. Temporary loss of stream flow is also documented in Colorado (Foidel <br />Creek mine). The potential for significant impacts to the Dry Fork above Minnesota Reservoir <br />above Panels E2 and E3 cannot be understated. Please reconsider conclusion #3. <br />99. Regarding conclusion #4 of Exhibit 60B, while the DMG agrees that visual evidence of <br />cracking in unconsolidated material (like alluvium) is rare, fracturing of bedrock immediately <br />below the alluvium has been confirmed in numerous cases. Fracturing of the underlying <br />bedrock would almost certainly result in leakage of the saturated alluvial aquifer and possibly <br />stream flow to the bedrock fractures. While this impact may equilibrate over time, stating that <br />the streams and alluvium would not be impacted may not be accurate. Rather than no impact, <br />the DMG believes that the potential for impact exists based on data provided and past <br />experience. Please reevaluate. <br />MCC Response: Exhibit 60B was revised. <br />100. Rule 2.05.6 (6)(a)(ii)(B) requires that a map show the location and configuration of structures <br />and renewable resource lands within the permit azea and adjacent area. Information on azeas <br />within the permit area and adjacent azeas to the east and south are present on Map 37, but no <br />.• information is provided in adjacent azeas to the west. Please confirm there are no such items to <br />the adjacent west. <br />MCC Response: MCC has prepared a structures map. <br />101. The application needs to describe the existing premising environmental resources [Rule <br />2.04.3(1)] within the proposed permit area and adjacent azeas that may be affected or impacted <br />[Ru]es 2.05.6(2)(a), 2.05.6(3)] by the proposed underground mining activities and remedial <br />actions, if appropriate. In this regard, please identify the wetlands [Rules 2.05.6(2)(a)(iii)(C) <br />and 4.18(5)(e)], riparian azeas [Rules 2.04.11(1) and 4.18(5)(e)], alluvial valley floors (Rules <br />2.06.8 and 4.24.2) and agricultural lands [Rule 2.06.8(5)(c)]. <br />MCC Response: MCC conducted a natural resources survey and inventory and it is <br />included as Exhibit 32B. <br />102. Please better demonstrate that there is no probable impact to the Minnesota reservoir from the <br />proposed mining plan. Potential failures that need to be addressed include failure of the dam <br />embankment structure itself due to ground subsidence, failure of the dam embankment <br />structure from seismic phenomenon, hydraulic communication with voids in underlying <br />materials from ground subsidence, reduction in pool size from subsidence-induces land slides <br />about the reservoir, and overtopping of the dam structure from rapid pool displacement due to <br />subsidence-induced landslides into the reservoir. The analyses of angles of draw demonstrate <br />• no probable impact to the dam embankment or reservoir from ground movement due to <br />subsidence of underlying materials. A level of horizontal acceleration that causes internal <br />