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West Elk Mine <br />• 4. A limited set of cracks occurred above the barrier pillar on the east boundary of 1NW longwall <br />panel, along the east line of Section 20. Again, this area was also affected by room-and-pillaz <br />mining in the F Seam. <br />5. While mining was occurring in 8NW longwall panel, MCC received a complaint from the <br />landowner regarding cracks on his property. As a result of the complaint, CDMG conducted an <br />inspection of the surface cracks on the owner's property and wrote an inspection report <br />summarizing their observations (CDMG, 1996). Since WWE was denied access to the site by the <br />land owner, and therefore limited to low-elevation aerial reconnaissance, the discussion of the <br />mechanism behind the formation of these cracks relies mostly on the CDMG inspection report. <br />These cracks were observed in the vicinity of a relatively large, historic, episodically active <br />landslide (Dames and Moore 1993). Extensive recent landsliding was observed in the SWl/4 of <br />Section 24 in the spring of 1996. The landslide activity created numerous cracks and "graben-like <br />extensional troughs up to ten feet wide and five feet deep." These cracks were parallel to the fall <br />line, which is typical of the translation of the sliding debris as shown in Figure 19. According to <br />Dr. Pendleton of DMG, the observed features are typical of large landslide masses in the Williams <br />Fork Formation (geological equivalent of the Mesaverde Formation) and they occur prolifically <br />throughout the North Fork Valley on slopes of varying gradient and aspect. Based on his <br />experience in the Forth Fork Valley, Dr. Pendleton concluded that subsidence does not appeaz to be <br />a significant determinant in the reactivation or initiation of landslide activity. CDMG concluded <br />that "there is no evidence with which to definitively verify or discount a connection between <br />subsidence of the MCC mine workings and this active landslide." <br />Eight crack locations were visited during the CDMG inspection. While most of the surface cracks <br />were attributable to rejuvenated landslide movement, three minor cracks were reported to be the <br />result of mining subsidence (Nos. 2, 3, and 8 on Figure 19A). These cracks were three to four <br />inches wide and less than one foot deep. Field observations by MCC personnel indicated that these <br />cracks were already healing shortly after mining had occurred. Two of these cracks (Nos. 3 and 8) <br />aze typical of the dynamic subsidence process. As mining occurs, the overburden above the mined <br />portion subsides, and differential movement results between the mined and munined areas. Surface <br />cracking can occur at the location of the differential subsidence. As mining continues, the adjacent <br />overburden subsides and the surface cracks will usually close completely (DeGraff and Romesburg <br />1981). These cracks healed significantly as evident in the late summer of 1997. Additionally, the <br />overburden thickness under the areas where the cracks occurred was less than 500 feet~ne of the <br />few locations within the perrnit azea where the overburden is this shallow. <br />6. Within the Apache Rocks mining azea Mr. Dunrud has observed several additional surface cracks <br />(see report titled "Subsidence Observations, West Elk Mine, July 22-24, 2003. These include the <br />following: <br />• Location 13 -located in the NW 1/4 ,Section 28, T 13 S, R 90 W <br />• Location 3 -bluff located above the eastern part of longwall panel 14, above the eastern <br />end of longwall panel 14, in NE `/,, Section 27. <br />• Location 1 -located in massive sandstones of the Ohio Creek Formation, above the <br />approximate middle part of longwall panel 14, in the NE'/,, Section 27. <br />2.05-/!1 Revised June 1005 PRIO, Rev. March 2006; Rev. Apri12006 PRIG; May 1006 PRIO <br />