Laserfiche WebLink
West Elk Mine <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 are 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 years (to account for <br />seasonal variations) prior to any mining in the area. <br />Srins <br />Decreed Spring 21 is located within the areas of mining influence of un-mined longwall panels <br />E5, E6, and E9 in the NEl/4 of Section 5, (Township 14 South, Range 90 West). Maximum tilt <br />and strain is expected to occur in this area, 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 visit, <br />include: 1) a spring located 800 feet west, southwest of the Minnesota Reservoir dam-outside the area of <br />• any planned mining influence; 2) a spring located along Dry Fork 700 feet west of the confluence of <br />Poison Creek and Dry Fork, above projected longwall panel E2 in about 650 feet of overburden to the E <br />seam; 3) Deep Creek Spring over Panel E 3; 4) the 96-2-2 Spring over Panel E 4; and 5) a spring located <br />south, and outside of the area of influence of longwall panel E8. <br />Of the springs mapped, Deep Creek Spring over Panel E 3, the 96-2-2 Spring over Panel E 4, the <br />decreed Spring 21, and the spring located along Dry Fork and above longwall panel E2 (J-7), <br />may be impacted by longwall mining. The source of decreed Spring 21 may be a local aquifer in <br />bedrock of the Mesaverde Formation, Nvhereas, the source of the spring along Dry Fork (above <br />longwall panel E2) is likely to be a local aquifer in colluvium or alluvium derived from debris <br />flows. The Deep Creek Spring and the 96-2-2 springs are in colluvium in Deep Creek. <br />Aquifers <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 strati graphically positioned in zones of tensile strain. <br />impacts may occur for Iona periods of time, where the aquifer is located above mine boundaries <br />and barrier pillars, areas where pei7nanent strain occurs. On the other hand, dynamic strains and <br />related cracks produced by subsidence above moving longwall faces in a given area are nil and <br />close when the longwall faces move out of the area of influence of this area. Based on the <br />author's evaluation, any mining effects on local on aquifers can best be identified by monitoring <br />any changes in flow and water levels in springs and ground water. <br />Ground Water Wells <br />2.05-155 Revised June 200.1 PRIO, Rev. Alarch 2006; A1ay 2006 PR10, Nov. 2006TR107,Apri12007TR108; Sep. 1007 PR12; Feb. 2008 PR-12