2018-09-04_PERMIT FILE - C1980007A (44)

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West Elk Mine This landslide reactivated in the spring and summer of 1996. CDMG and MCC personnel inspected the area at that time, with the landowner's approval. Written comments by CDMG provide an excellent descripfion of the rejuvenation of a typical large landslide which has experienced numerous episodic periods of movement in historic and probably prehistoric time. Although access was later denied by the surface owner, a visual study of the azea was conducted by Wright Water Engineers from a small plane. Wright Water Engineers concurs with CDMG conclusions that "one cannot verify ar discount a connection between the mining activity and the current reactivation of the landslide," and, "this landslide does not appeaz to constitute any anomalous risk to health and safety or anomalous impact to the environment " MCC will continue to repair roads and structures that may have been damaged by subsidence induced landslide activity as it has done in the past and has committed to do in Section 2.05.6 of this Mining and Reclamafion Plan document. Highway 133 Along Highway 133 east of West Elk Mine neaz Box Canyon, two lazge dormant landslides were reactivated in 1980 by highway excavation. One lies east of Box Canyon and one occurs to the west between Box Canyon and the portal of the Oliver No. 2 Mine. The eastern-most slide was reactivated again in the spring of 1993, which closed the highway for some time. Because the eastern slide lies more than 2,000 feet from the proposed longwall panels in the Box Canyon permit revision azea, only the nearer western slide will be discussed below. Regrettably few, if any, maps were made by Colorado Department of Transportation (CDOT) of the landslides, the drill holes or the remedial actions performed in this area while constructing State Highway 133 (SH-133). Most of the information compiled or used by CDOT appears to be unrecoverable. An exhaustive search of files by CDOT personnel and a review by J.W. Rold of CDOT's Central Files microfilm resulted in data on seventeen drill hole logs (with no locations), one memo on methane safety concerns, two seismic profiles and poor reductions and reproduction of a small scale map of the constructed highway. Most CDOT information is therefore limited to the memory of, and personal and telephone communications with, Bob Barrett, CDOT District Geologist and J.B. (Brandy) Gilmore, CDOT Chief Geologist. A summary of pertinent information relayed by them and gleaned from the files follows: "Before the construcfion, the slides appeazed dormant and very old." This agrees with the interpretation of aerial photos predating highway construction. 2. "Road construction reactivated the slides when the slide toes were excavated." Although the slide appeared to be a simple, fairly lazge, deep rotational slide, its movement and the drilling showed it to be a complex of fairly small slides. Each slide element is separated from the one above by a competent, stable sandstone ledge. John Rold's field investigation in October 1996 and close examination of the detailed topographic map confirms CDOT's observation. • 1.04-40 Revised November 1004 PRt 0