2013-01-25_REVISION - C1981019

• Permit No: C1981019
• IBM Index Class Name: Revision
• Doc Date: 1/25/2013
• Doc Name: Adequacy Letter ‎(emailed and mailed)‎
• From: DRMS
• To: Tony Tennyson, Colowyo Coal Company
• Type & Sequence: TR98
• Email Name: RDZ
• Email Name: DIH
• 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
COLORADO
ID IV I S I O N O F
RECLAMATION
MINING
SAFETY
January 25, 2013
John
G vernor enlooper
Mr. Ton Tennyson
Tony y
Mike King
Executive Director
Colowyo Coal Company
h
5731 State Highway 13
g y
Meeker, CO 81641
Loretta E. Pineda
Director
Re: Colowyo Mine, Permit No. C- 1981 -019, TR -98 Adequacy
Dear Mr. Tennyson:
Your technical revision application TR -98 (revising the West Taylor Fill temporary spoil pile design) was
considered complete for the purposes of filing on December 27, 2012.
The following three items include the Division's first adequacy comments; your responses in your letter dated
January 18, 2013; and our follow -up comments.
Item 1
DBMS: Two scenarios within the geotechnical analysis by Shannon & Wilson did not meet the minimum
required factor of safety (FS) of 1.5 as per Rule 2.05.3(6). These correspond to Case 2a and Case 2c. Please
explain how long -term stability is achieved in relation to the Division's minimum requirements for slope stability
of a temporary excess spoil pile. This explanation may include an additional slope stability analysis regarding the
temporary excess spoil fill showing that with revised input parameters (more conservative than the average values
but less conservative than the "low bound" values used previously) the proposed excess spoil pile will meet the
Division's minimum requirements of 1.5 FS.
Colowyo: Colowyo has reviewed the Colorado Mine Land Regulations and does not agree that Rule 2.05.3 (6)
addresses factor ofsafety (FS) in its entirety. Colowyo does not believe that any regulation within the Colorado
Mine Land Regulations speaks to a FS of 1.5 for a temporary spoil pile. Rule 4.09.1(7) does address a FS of 1.5
for excess spoils. However, this rule does not specifically nor directly address temporary spoil piles. The rule
does state that, covered with topsoil or substitute material in accordance with 4.06... " which indicated a
surface that is prepared for reclamation and will be a permanent surface. Thus, this statement in the rules
demonstrates that Rule 4.09.1(7) is directed towards a permanent excess spoil and not a temporary spoil that is
proposed under this technical revision.
The Division has also previously approved text in Colowyo's PAP which addresses Rule 4.09.1(7). In Exhibit 21,
Item 1, Addendum No. 3 -5, Shannon & Wilson's report addresses a FS for a permanent fill in the conclusions
section and it states, "The Colorado Mined Land Reclamation Board regulations (2005) require a long term FS
of 1.5 or greater for permanent spoil fill slopes; they do not specifically address temporary slopes. " This
statement by a professional engineer and approved by the Division previously sets precedence that the Division
agrees that the rules do not address a FS for a temporary spoil pile.
In conclusion, Colowyo firmly believes it is meeting all the requirements of the Colorado Mine Land Reclamation
Board regulations with the FS that is presented in Addendum 4 of Shannon & Wilson's report. Additionally,
because the rules do not specifically address a FS for a temporary spoil pile, Colowyo feels that a certified
professional engineering report presents the best alternative to calculating a FS utilizing current professional
judgment andpreviously approved materials, because the rules do not specifically address a FS for a temporary
spoil pile.
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines