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2009-02-23_INSPECTION - M1977211
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2009-02-23_INSPECTION - M1977211
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Entry Properties
Last modified
8/24/2016 3:43:47 PM
Creation date
3/5/2009 1:42:14 PM
Metadata
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Template:
DRMS Permit Index
Permit No
M1977211
IBM Index Class Name
INSPECTION
Doc Date
2/23/2009
Doc Name
Question- How much of Area H was open at the time of the Pikeview slope failure?
From
SES
To
DRMS
Inspection Date
2/10/2009
Email Name
BMK
Media Type
D
Archive
No
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Southwestern <br />Ecological <br />Services <br />b/ -TI- caA <br />37 East Colorado Avenue • Denver, Colorado 80210-3105 • (303) 722-9067 <br />February 23, 2009 RECENM <br />Berhan Keffelew" DEB 2 3 2009 <br />Tony Waldron <br />Division of Reclamation, Mining and Safety Division of ReCI. <br />Room 215 Mining and Sd* <br />1313 Sherman Street dtwl 14 Denver, CO 80203ju <br />A: Question regarding how much of Area H was open at the time of the Pikeview slope failure. r/a d (dq <br />Dear Berhan: <br />Your questions as to how much of Area H was opened at the time of the slope failure and what relationship TR- <br />11 had to the slope failure is quite relevant. But first, one must understand the concept of Area H. This part of the <br />quarry which was defined in the 1994 amendment, is a three-dimensional concept. That is, Area H is not defined just <br />by location but also by elevation. Basically, once the quarry floor descend below the elevation of eventual backfilling <br />of Area H then Area H is entered. Any mining at that same location that is above that backfill elevation is not <br />actually in Area H even though it is in the same horizontal location as Area H. That elevation is a fuzzy zone that is <br />between the elevations of 7200' and 7225', with the higher elevation on the west side. It is defined by the backfill <br />elevation on the reclamation plan map in the 1994 amendment. Actual mapping of floor elevations as it has <br />descended has not been done, so it is impossible to provide a precise percentage value of the amount of Area H that <br />was open at any one time. <br />Area H appears to have been actually entered sometime in either late 2007 or early 2008. Once again, it is hard <br />to tell for sure. With respect to the condition on December 2, 2008, at the time of the slope failure, all that can be <br />provided is a rough estimate. As it turns out a couple of photos taken by Mac Shafer and included on the attached <br />graphic help some with this estimate. The first photo was taken at about the same time of day and approximately the <br />same time of year as the second photo which was taken after the slope failure. As you can tell, they were not taken <br />from the same location,.but they are close enough to provide some guidance in estimating the amount that was <br />open. <br />Basically, the top elevation of Area H is roughly at the elevation of the plant and the main road to the plant east <br />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 <br />requested to mine. Clearly the deepest part of the pit is on the near end and it is probably about 50 feet down into <br />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 <br />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 <br />main body of the slope failure went into the deepest area, but was spread across the quarry face to the north and <br />south of the deepest area. Whether the slope failure was triggered by the deeper mining or the slope failure was a <br />more generalized failure is beyond my area of expertise and I suspect the Colorado Geological Survey report has <br />already addressed this to the extent they can given the limited amount of historical data they had to work with. I <br />don't think there is much dispute that the slope failure was caused by too much load on too small of a footing. <br />From these photos and in particular the second photo it appears that more than 25% of Area H was opened. In <br />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 <br />which turned out not to have much limestone present is occupied by the hairpin turn in the foreground. You can <br />estimate your own values from the images provided. <br />In studying the plans and the impact of Area H on the slope failure, there are several points that need to be <br />taken into account. First, the Layback Amendment (2000) only included the layback area. Unfortunately, that <br />amendment was silent with respect to how that plan revision related to the rest of the quarry plan. As a matter of <br />policy, this is a prime example of why amendments to permits need to address not only the area being modified but <br />how that modification influences other related portions of the plan. As a side note, this was one of my big <br />complaints about the layback amendment, but Castle had Banks and Gesso prepare that plan as I turned down that
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