2008-12-10_REVISION - C1981010 ‎(3)‎

• Permit No: C1981010
• IBM Index Class Name: REVISION
• Doc Date: 12/10/2008
• Doc Name: Response/Comment Letter
• From: Knight Piesold and Co
• To: DRMS
• Type & Sequence: PR6
• Email Name: JDM
• Media Type: D
• Archive: No

Knight Piesold
C O N S U L T I N G
Mr. Jason Musick
Environmental Protection Specialist
December 10, 2008
was removed and placed into either the Buttress Fill area or the Horse Gulch Fill. A total of
38 million cubic yards was shown in the final configuration of the Horse Gulch Fill.
The plan has been revised using three separate areas instead of two. Under the new scenario,
direct haul backfilling can begin as soon as excavation of the first third of K pit is complete. The
result is a significantly smaller Horse Gulch Fill (approximately 24.6 million cubic yards - 35%
smaller than the initial plan). As with the initial submittal, the resulting final configuration
generally meets the standards of AOC. However, the revised configuration more closely
approaches the original elevations. Map M10A, Mining and Regrade, sheet 3 has been revised to
reflect the new mine plan layout. Map M12, Post Mining Topography, and Map M14A, Post
Mining Cross-Sections have been revised to reflect the post mining configuration.
Specific responses to the Division's individual comments discussed in the letter of February 15th
are shown below.
Division Response No. 1: ...Rule 1.05.3(6)(b) requires the submittal of descriptions of
proposed disposal sites and designs of proposed disposal sites and designs of proposed spoil
disposal structures that affect the applicable requirements of Rule 4.09. Rules 2.05.3(6)(b)
and 2.05.3(6)(c) additionally specifically require the submittal of results of geotechnical
investigations of proposed spoil disposal sites and structures. Please submit the results of
the geotechnical investigations conducted in accordance with the requirements of these
rules for the Horse Gulch Fill site and structure and the K Area Buttress Fill site and
structure.
Response: Enclosed you will find two certified reports prepared by AAI. These reports are
entitled "Horse Gulch Fill Stability Analysis" and "K-Pit Buttress Fill Stability Analysis."
These reports will be inserted into Appendix T in Trapper's permit document. Material
properties were derived from field investigations and core hole data. Material properties
from geotechnical investigations are discussed in section 2 of both reports.
Division Response No. 2: ...Please provide a final version of the Agapito Associates Inc
report. Please understand that the Division cannot treat information pertaining to
geotechnical stability as confidential or proprietary.
Response: This report, entitled Trapper G-Pit Landslide Mining Assessment, is enclosed.
Division Response No. 3: ...Please provide a plan per Rules 2.05.4(2)(c) and 4.14.1(2)(d)
which describes the process by which the boxcut spoil or initial cut spoil will be returned to
K Pit in the event that mining operations proposed for K Pit cease before the volume of
excavated K Pit overburden meets the definition of "excess spoil" at Rule 1.04(43a).
DV102.00302.01 2
PR-6 Completeness Response Ltr