2012-03-23_REVISION - C1996083

• Permit No: C1996083
• IBM Index Class Name: Revision
• Doc Date: 3/23/2012
• Doc Name: Adequacy Review -Geotechnical
• From: Marcia Talvitie
• To: Brock Bowles
• Type & Sequence: TR72
• Email Name: BFB
• Email Name: MLT
• Email Name: SB1
• Media Type: D
• Archive: No

INTEROFFICE MEMORANDUM
Date: 23 March 2012
To: Brock F. Bowles, Lead Specialist
From: Marcia L. Talvitie, P.E.
Subject: Bowie No. 2 Mine (Permit No. C- 1996 -083)
TR -72 — Expansion of Coal Mine Waste Disposal Area No. 2
Preliminary Adequacy Review (Geotechnical)
In response to your request, I have conducted a preliminary review of the geotechnical aspects of
the TR -72 application submitted by J.E. Stover & Associates on behalf of Bowie Resources,
LLC (BRL). With this revision application, BRL is seeking Division approval to increase the
available storage capacity of Gob Pile 92, a Coal Mine Waste Disposal Area (CMWDA). BRL
proposes to accomplish this increase in volume by excavating a ridge of native material that
protrudes from the slope immediately west of the valley fill portion of the existing disposal area.
The volume excavated will then be backfilled with CMW.
Background
To conduct my review, I researched the permitting history of the CMW Disposal Areas (gob
piles) presently approved for the Bowie No. 2 Mine. There have been a number of modifications
to the CMW Disposal Areas on this particular hillside, and I wanted to ensure that the TR -72
proposal does not compromise or contradict determinations made with previous revisions. A
summary of the history is provided here, for discussion and reference. (Note: I have not
included "Gob Pile #3" in this chronology, as it stands separately from the others, southeast of
Bowie Road, SH 133B.)
As originally permitted, this mine included a CMW Disposal Area with a projected design life of
15 to 20 years. Design details for the disposal area were contained in Volume IV of the permit.
This disposal area filled faster than had been anticipated, and the need for a second disposal area
was realized. The original area became known as, "Gob Pile #1" with the creation of "Gob Pile
#2" further to the east.
CMW Disposal Area No. 2 was first permitted with TR -30 in 2004 and new Volume IX was
added to the permit. The application included a Geotechnical Engineering Study prepared by
Lambert & Associates, dated November 10, 2001. Stipulation No. 16 was attached to the
Decision for TR -30; it required BRL to determine moist unit weight and strength parameters of
the coal mine waste, during construction of the first bench, and demonstrate that constructing the
pile as designed would achieve a minimum factor of safety (FOS) of 1.5.