2010-10-12_REVISION - C1981019

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 10/12/2010
• Doc Name: Adequacy Review Memo
• From: Kent Gorham
• To: Jim Stark
• Type & Sequence: TR87
• Email Name: KAG
• Email Name: SB1
• Email Name: JRS
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone] Interoffice Memo
To: Jim Stark ,,//??//
From: Kent Gorham ?I'r?a
CC: Sandy Brown
Date: October 12, 2010
RE: Adequacy review, TR-87, Colowyo Mine, #C-1981-019
COLORADO
D IV IS I ON OF
RECLAMATION
MINING
SAFETY
I have completed my review of the latest materials submitted (September 7, 2010 and
September 23, 2010) for Technical Revision No. 87 (TR-87) for the Colowyo Mine, permit
#C-81-019. My comments are as follows.
General Comments
In addition to other materials submitted, TR-87 presents and proposes three, time-specific,
SEDCAD models for the Prospect watershed demonstrating that the sediment control system
of stock tanks, diversion ditches, and the Prospect pond will treat storm runoff to the required
effluent limitations in all three scenarios. Included in the modeling are stock ponds, five of
them, within the three constructed drainages above the Prospect Pond. These five ponds are
included in the modeling if they would exist on the ground at the snap shot in time
represented by each SEDCAD model. These ponds are no longer secondary, extra sediment
control structures but are primary structures, required to be designed, constructed, and
maintained similar to a sediment pond. As primary structures, these ponds are not eligible for
any inspection waiver. They should be treated no differently than a sediment pond going
forward.
The Divisions has also asked for additional reclamation practices such as contour ditches,
surface roughening, terraces, etc over the last few years following the violation issued for the
failure at Prospect Pond. I also noticed the commitment to use surface roughening and
contour furrows in the East Pit on page 2.05-30. On the same page, I also noticed language
about contour furrows constructed 4-6 inches deep and 20-25 inches wide, spaced some 10-
75 feet apart depending on the slope. I somewhat question the contour furrow design in
terms of Colowyo's ability to construct the furrows in accordance with the design. If their
intent is what the permit states, I have no issue. However, if they do not intend to do what is
stated in the permit text, they need to propose something else now.
You also indicated that some deficiencies that I noticed with permanent drainage designs
outside of the East Pit should be handled separately in TR-81.
My specific questions are as follows, bold text as necessary regarding what we are asking for
Colowyo to submit. Let me know if you have questions.
Office of Office of
Mined Land Reclamation Denver - Grand Junction - Durango Active and Inactive Mines