2009-07-02_REVISION - C1981010

• Permit No: C1981010
• IBM Index Class Name: Revision
• Doc Date: 7/2/2009
• Doc Name: 2nd Adequacy Review Memo
• From: Marcia Talvitie
• To: Jason D Musick
• Type & Sequence: PR6
• Email Name: JDM
• Media Type: D
• Archive: No

DIVISION of RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone; [phone]
FAX: [phone]
STATE OF COLORADO
INTEROFFICE MEMORANDUM
Date: 02 July 2009
To: Jason D. Musick
From: Marcia L. Talvitle 4111�?
Subject: Trapper Mine — Permit Igo, C- 1981.010
PR-06 — Horse Gulch Fill and K -Pit Buttress Fill
211 Adequacy Review — Engineering
COLORADO
D IV[ S I ON OF
RECLAMATION
MINING
SAFETY
Bill Ritter, Jr.
Governor
Harris D. Sherman
Executive Director
Ronald W. Cattany
Division Director
Natural Resource Trustee
Per your request, I have reviewed pertinent portions of the 05 June 2049 response to the
Division's Preliminary Adequacy Review, prepared by Trapper Mining, Inc. (TINA). My review
focused on the responses to the items I compiled in my 28 April 2009 memo to you.
TINA has contracted with Agapito Associates, Inc. (AA1) to conduct stability analyses of the HG
and K -Pit Fills. These two revised reports (intended for inclusion in Permit Appendix T), along
with the revised pages of the permit provided, were evaluated for compliance with the rules and
regulations of the Mined Land Reclamation Board.
My original comments are included below, each followed by TMI' s response and my comments
as to the adequacy of the response.
Rule 4.09.1. ; Disposal of Excess Spoil General Reamirement „
1. 4,09.1(10) requires that where the slope in the disposal area 1s steeper than 2.8h :lv (3 6
percent), or such lesser slope as maybe designated by the Division based on local
conditions, keyway cuts (excavations to stable bedrock ) or rock toe buttresses shall be
constructed to stabilize the fill. where the toe of the spoil rests on a downslope, stability
analyses shall be performed in accordance with 2,05.3(6) (b, c and d to determine the
size of the rock toe buttresses and keyway cuts.
The toe of the HG Fill coos rest on a slight downslop , but the stability analysis has
demonstrated that a Factor of Safety greater than 1. 5 can be achieved without the use of a
keyway or toe buttress. However, AA1 has identified steeper portions of natural ground
on the northern sideslope of Horse Gulch, and states that benching is required for these
areas (AA1 SIG Fill Stability Analysis Figure . Based on the auger drilling data
(Tables 1 and 2), these slopes may be composed of thick, weals dark- brown clay. The
application does not address the proposed bench configurations and dimensions.
office of Office of
Mined Land reclamation Denver • Grand Junction • Durango Active and Inactive dines