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2009-02-23_INSPECTION - M1977211
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2009-02-23_INSPECTION - M1977211
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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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Page 2 <br />opportunity because I did not feel confident that I was qualified to do that plan. When I reviewed the plan, 1 did <br />express a concern about the lack of connection to adjacent areas to the south and to Area H which was still in the <br />plan and carried over from the 1994 amendment which I prepared. <br />Perhaps of greater importance though is the fact that after the layback plan was begun it was realized that <br />MSHA would not allow mining at the top of the quarry backwall in the Forest Service land or lower on the backwall <br />while mining immediately below at the base of the backwall. That is, the two mining areas had to be offset for safety <br />purposes. This created a situation where quarry floor mining had to move back and forth while staying out from <br />under the higher elevation mining. All of this back and forth motion on the quarry floor was begun long before the <br />top elevation of Area H was reached. Once Area H was reached, that back and forth motion had to continue to <br />produce adequate volumes of limestone to meet customer requirements. <br />The effect of this was to slow the progress on the layback because often it had to simply stop while a portion of <br />the floor was mined. In effect, everything became horribly unsynchronized between the quarry floor and the layback <br />progress. Whether this would have been addressed if the layback amendment had looked at more than just that area <br />cannot be determined, but, in my opinion, if the layback plan had looked at the linkage aspects to other portions of <br />the total permitted plan this difficulty might have been addressed. I'm not certain it would have ultimately changed <br />anything, but it is possible that it might have been recognized that at some point there would be a great deal of load <br />high on the backwall relative to the amount of support on the floor. But that is hindsight. <br />With regard to the questions on the influence of TR-11on the propagation of the slope failure, in my opinion, <br />they are not closely related. Keep in mind, until last week when you pointed out this technical revision I did not even <br />know of its existence. I obtained it from the permit file disk Jim Dupler prepared for me and have carefully <br />examined that revision. It is true that TR-11 allowed an alteration of the benching in the south end to have higher <br />walls relative to the bench. That might not have been the best idea, all things considered. But, looking at the first <br />photo, one can see the effect of TR-11. That area includes the narrow "canyon" in the foreground and that zone <br />ends at the point where the "canyon" opens to the quarry floor. The northern edge of TR-11 is at about the near <br />side of the large pile of rubble at the entrance to the "canyon." The floor of TR-11 is visible where the small road is <br />in the "canyon." Thus, the lowest elevation in TR-11 was above the top elevation of Area H whose south boundary <br />is somewhere in the middle portion of the rubble pile at the mouth of the "canyon." <br />Although support was removed in the TR-11 area, the dip of the rock here is about 4 degrees so sliding on <br />bedding plane joints in the limestone would have been minimal, as pointed out by Dr. Abel. Elsewhere the dip is <br />about 32 to 34 degrees to the east and approaches vertical right at the fault zone where the Paleozoic sediments <br />contact the PreCambrian granite. Nevertheless, there does appear to be some small amount of cracking on the <br />benches at the top of the TR-11 area. Rather than sliding cracks, these may be separations due to the limestone <br />below the south peak moving somewhat downward and rotating clockwise significantly after the middle of the <br />quarry slid down. But clearly, if there is cracking in the TR-11 area as a result of the overall slope failure then the <br />west side of the TRA 1 area has suspect stability at this point. <br />Hopefully, these two photos will help to illustrate the nature of the relationships and will help answer your excellent <br />questions regarding these features. <br />Sincerely, <br />7 <br />Mark A. Heifner <br />cc: Mac Shafer <br />Jerald Schnabel
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