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West Elk Mine <br />• currently monitored. For more information, please see Section 3 (Groundwater Hydrology) in <br />Exhibit 71. Only a few springs in the West Ells Mine azea indicate a source from a local bedrock <br />aquifer. Most springs likely have sources from local aquifers in surficial material (debris flows, <br />colluvium, and possibly alluvium). <br />In contrast to surface water containment structures, such as reservoirs, ponds, streams and <br />ditches, springs and aquifers may have water sources that are either in bedrock beneath the <br />blanket of clay-rich surficial material (debris flows, alluvium, and colluvium), or have a source <br />from within the surficial material. Subsidence may affect a spring or aquifer source located in <br />bedrock, whereas effects may or may not be expected where the spring source is within the <br />surficial material. Tension cracks produced in sandstone bedrock during the subsidence process, <br />for example, may divert water to a lower rock layer and therefore change the flow location. <br />However, local aquifers in permeable zones, which aze interlayered with clay-rich zones <br />(Wasatch clays) in the surficial deposit, may yield to tensile stresses without cracking. There is <br />no field documentation known to Mr. Dunrud to either support or refute this statement. <br />Therefore, it is important to monitor all known spring flows for a few yeazs (to account for <br />seasonal variations) prior to any mining in the area. <br />S rn inrs <br />Decreed Spring 21 is located within the areas of mining influence of un-mined longwall panels <br />E5, E6, and E9 in the NE'/< of Section 5, (Township 14 South, Range 90 West). Maximum tilt <br />and strain is expected to occur in this azea, because it is located above the projected haulageway <br />and barrier pillar to the haulageway. The overburden depth at this spring site to the E seam is <br />about 650 feet. <br />Springs mapped in the South of Divide mining area, which have been found flowing at every site <br />visit, include: 1) a spring located 800 feet west, southwest of the Minnesota Reservoir dam- <br />outside the area of any planned mining influence; 2) a spring located along Dry Fork 700 feet <br />west of the confluence of Poison Creek and Dry Fork, above projected longwall panel E2 in <br />about 650 feet of overburden to the E seam; 3) a spring located south, and outside of the area of <br />influence of longwall panel E8. <br />Of the springs mapped, only the decreed Spring 21 and the spring located along Dry Fork and <br />above longwall panel E2, may be impacted by longwall mining. The source of decreed Spring <br />21 may be a local aquifer in bedrock of the Mesaverde Formation, whereas, the source of the <br />spring along Dry Fork (above longwall panel E2) is likely to be a local aquifer in colluvium or <br />alluvium derived from debris flows. <br />A ui ers <br />Horizontal strain produced during subsidence could impact local aquifers in bedrock beneath the <br />blanket of clay-rich surficial material. It also may impact local aquifers in surficial material, <br />where permeable and saturated zones are stratigraphically positioned in zones of tensile strain. <br />Impacts may occur for long periods of time, where the aquifer is located above mine boundaries <br />and barrier pillars, azeas where permanent strain occurs. On the other hand, dynamic strains and <br />related cracks produced by subsidence above moving longwall faces in a given area aQe nil and <br />close when the longwall faces move out of the azea of influence of this area. Based on the <br />2.05-754 Revised /wre 1005 PRIG, Rev. March 1006; May 1006 PRI G <br />