2009-03-11_REVISION - C1981019

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 3/11/2009
• Doc Name: Adequacy Response Comments ‎(Memo)‎
• From: Kent Gorham
• To: Jim Stark
• Type & Sequence: TR73
• 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 Gorha
CC: Sandy Brown
Date: March 11, 2009
RE: Adequacy response review comments, TR-73, Colowyo Mine
COLORADO
DIVISION OF
RECLAMATION
MINING
SAFETY
Bill Ritter, Jr.
Governor
Harris D. Sherman
Executive Director
Ronald W. Cattany
Division Director
Natural Resource Trustee
Jim, as per your email request dated March 5, 2009 1 have completed my review of the
adequacy responses from Colowyo for Technical Revision No. 73 (TR-73) for the Colowyo
Mine, #C-81-019.
2. The Division does not agree with some of the SCS curve number ranges as presented
in Table 1 (Exhibit 7, page 3) for two main reasons.
a) Hydrologic soil groups are represented in Table 1 as B soils for all reclaimed
lands (topsoiled areas post-reclamation). According to information provided on
page 4, Exhibit 7, the Campass, Burnette, and Work Series soils are the three
dominant soils within the proposed disturbed area. The Burnette and Work
series are C soils (reference TR-55, Second Edition, June 1985, Exhibit A-1,
Hydrologic soil groups for US soils). Given that soils will likely experience
some compaction during re-application, representing all soils as being in the C
category would likely result in more accurate storm runoff modeling.
b) No site-specific evidence in the form of vegetation sampling results for total
cover was provided to justify 85% cover on areas of 1-2 years growth or the 3+
year growth areas. Please provide support for the amount of hydrologic cover
from vegetation surveys or other available data.
3. Please refer to Section 1.9 Base Flow, of the revised materials. It states "A base flow
of .15 cfs was used for the Streeter Pond design. A base flow of. 03 cfs was used for
the West Pit pond design. Base flows were not used in any other pond design." The
Division's original question was related to the pumping of pit water, through outfalls as
approved under the CDPS permit and the implications of this pumping for those pond
treatment systems where a constant base flow was not included in the design. That
was the reason for the previous language that has most recently been removed by
Colowyo. The currently approved CDPS permit allows pit water to be pumped to
Streeter, Work Area, Gossard, Gulch A, Stoker Siding, Rail Loop, West Pit, Section
16, and East Taylor.
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Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines