Laserfiche WebLink
West Elk Mine <br />• Historic SprlnP Monitoring Data <br />Spring monitoring to establish baseline data and to assess the impacts of mining in the F Seam has <br />been conducted by MCC for over 10 years. Monitoring of springs potentially subject to impact <br />from B Seam mining has been conducted since 1992. The relevant data indicate that F and B Seam <br />mining has had little, if any, impact on spring flows. Specific information on spring-related mining <br />impacts for these seams can be found in the Annual Hydrology Reports from 1982 to the present. <br />Plots of spring flow hydrographs aze contained in the Annual Hydrology Reports. Considerable <br />variation from yeaz to yeaz is also apparent along with the seasonal pattern. A comparison of <br />operational data with pre-mining data reveals no discernable difference. Flow monitoring will be <br />continued by MCC in order to assess trends over time. A visual comparison of the data presented in <br />the Annual Hydrology Reports reveals a lack of correlation among spring flows. <br />MCC has been building a representative database for springs in the permit and lease areas, since <br />1978. Sufficient baseline data, in accordance with CDMG regulations have been established to <br />enable future determinations as to whether longwall mining could be affecting the springs. As <br />described in Section 2.04.7, the following springs will be added to the monitoring program 10-1, <br />E14-1, and 24-3. <br />Conceptual Description of Subsidence Impacts to Springs <br />• The key to evaluating whether or not any given spring will be adversely affected by the E Seam <br />mining in the permit azea is to define its elevation relative to both the mine seam and the ground <br />surface. Essentially, the higher the elevation of a spring (and spring source), the smaller the <br />probability of adverse impact as a consequence of fractures that extend upward from the mine. <br />However, for a spring to avoid impacts from subsidence, in addition to being above the mine <br />fracture zone, the source of the spring needs to be far enough below the ground surface to avoid <br />surface fractures that may be the result of subsidence. This phenomenon is described by Liane <br />Kadnuck (U.S. Bureau of Mines) in her paper, Response of Surface Springs to Longwall Coal <br />Mining Wasatch Plateau, Utah, where she states, "The limited spring response observed at this site <br />may be attributed to several factors; (1) The thickness and composition of overburden present which <br />contained a massive competent sandstone, which causes bridging in the overburden, limiting <br />subsidence, (Z) Presence of formations containing swelling clays, and (3) The elevation of the <br />spring above the elevation of estimated heights of fracturing and caving in the overburden." This <br />basic concept is elaborated as follows: <br />In the east panels of the Apache Rocks mining area, only B-Seam mining will occur. Only B-Seam <br />mining will occur in the Box Canyon and West Flat Iron mining azeas. In the Apache Rocks <br />western panels (Sections 28, 29, and 30), both B and E-Seam mining will occur. Within the Apache <br />Rocks mining azea, the overburden thickness for the B-Seam ranges from 600 to 2,250 feet while <br />the overburden thickness range for the E-Seam is 400 to 1,100 feet. The typical interburden <br />distance between the B and E-Seams is 200 feet. Above the LONE and I INE Iongwall panels, the <br />overburden thickness ranges from 600 to 1,200 feet. Within the Box Canyon mining area, the <br />overburden thickness for the B-Seant ranges from 500 to 2,200 feet, <br />1.05-196 Revised June 1005 PRIO, January 2006, March 2006; Rev. May 2006 PRI G <br />