2009-02-23_INSPECTION - M1977211

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Southwestern Ecological Services b/ -TI- caA 37 East Colorado Avenue • Denver, Colorado 80210-3105 • (303) 722-9067 February 23, 2009 RECENM Berhan Keffelew" DEB 2 3 2009 Tony Waldron Division of Reclamation, Mining and Safety Division of ReCI. Room 215 Mining and Sd* 1313 Sherman Street dtwl 14 Denver, CO 80203ju A: Question regarding how much of Area H was open at the time of the Pikeview slope failure. r/a d (dq Dear Berhan: Your questions as to how much of Area H was opened at the time of the slope failure and what relationship TR- 11 had to the slope failure is quite relevant. But first, one must understand the concept of Area H. This part of the quarry which was defined in the 1994 amendment, is a three-dimensional concept. That is, Area H is not defined just by location but also by elevation. Basically, once the quarry floor descend below the elevation of eventual backfilling of Area H then Area H is entered. Any mining at that same location that is above that backfill elevation is not actually in Area H even though it is in the same horizontal location as Area H. That elevation is a fuzzy zone that is between the elevations of 7200' and 7225', with the higher elevation on the west side. It is defined by the backfill elevation on the reclamation plan map in the 1994 amendment. Actual mapping of floor elevations as it has descended has not been done, so it is impossible to provide a precise percentage value of the amount of Area H that was open at any one time. Area H appears to have been actually entered sometime in either late 2007 or early 2008. Once again, it is hard to tell for sure. With respect to the condition on December 2, 2008, at the time of the slope failure, all that can be provided is a rough estimate. As it turns out a couple of photos taken by Mac Shafer and included on the attached graphic help some with this estimate. The first photo was taken at about the same time of day and approximately the same time of year as the second photo which was taken after the slope failure. As you can tell, they were not taken from the same location,.but they are close enough to provide some guidance in estimating the amount that was open. Basically, the top elevation of Area H is roughly at the elevation of the plant and the main road to the plant east of the pit area. The far end of the road to the jaw is well above Area H. As a side note, it is this area that Castle has requested to mine. Clearly the deepest part of the pit is on the near end and it is probably about 50 feet down into Area H. The far end is roughly at the top of the Area H elevation. In between is one lift that is clearly down into the top of Area H by maybe 25 feet. In the photo there is a drill on that bench. As can be seen in the second photo, the main body of the slope failure went into the deepest area, but was spread across the quarry face to the north and south of the deepest area. Whether the slope failure was triggered by the deeper mining or the slope failure was a more generalized failure is beyond my area of expertise and I suspect the Colorado Geological Survey report has already addressed this to the extent they can given the limited amount of historical data they had to work with. I don't think there is much dispute that the slope failure was caused by too much load on too small of a footing. From these photos and in particular the second photo it appears that more than 25% of Area H was opened. In my estimation it may have been as high as 40%, but that may be a stretch because part of the south end of Area H which turned out not to have much limestone present is occupied by the hairpin turn in the foreground. You can estimate your own values from the images provided. In studying the plans and the impact of Area H on the slope failure, there are several points that need to be taken into account. First, the Layback Amendment (2000) only included the layback area. Unfortunately, that amendment was silent with respect to how that plan revision related to the rest of the quarry plan. As a matter of policy, this is a prime example of why amendments to permits need to address not only the area being modified but how that modification influences other related portions of the plan. As a side note, this was one of my big complaints about the layback amendment, but Castle had Banks and Gesso prepare that plan as I turned down that