2013-09-20_REVISION - C1992080 ‎(2)‎

• Permit No: C1992080
• IBM Index Class Name: Revision
• Doc Date: 9/20/2013
• Doc Name: Adequacy Comments ‎(Emailed)‎
• From: Susan Burgmaier
• To: Marcia Talvitie
• Type & Sequence: TR17
• Email Name: MLT
• Email Name: SB1
• Media Type: D
• Archive: No

September 20, 2013
To: Marcia Talvitie
From: Susan Burgmaier C-0
Re: Carbon Junction Mine (Permit No. C- 1992 -080)
Technical Revision No. 17 (TR -17)
Request for Assistance - Adequacy Review
Per your request, I have reviewed the Technical Revision (TR -17) application for the Carbon Junction
Mine for compliance with Rules 2.05.4(2)(c), 4.05.3, and 4.05.4. 1 have the following comments and
questions for the operator:
1. We are unable to locate supporting documentation for the flow values used in the design
information for the Carbon Junction Permanent Diversion, the upper portion of Carbon Junction
Channel, or the unnamed channel to the east of upper Carbon Junction. Page 5 -4 of Section 2.05 of
the approved permit application package makes reference to design information contained in
Appendices 5 -2, 5 -9, and 5 -10. In the approved permit application package we are unable to locate
an Appendix 5 -10; Appendix 5 -9 consists of a minor revision for a road accessing the Ewing Mesa Pit;
and Appendix 5 -2 does not appear to include any information on the design of the above listed
channels. Appendix 5 -2 did include channel size calculations for several channels, but did not
include any documentation for the assumed discharge volumes. Please provide the supporting
documentation so that the Division can verify the anticipated discharge volume in Carbon Junction
Channel, the Carbon Junction Channel Diversion, and the Unnamed Channel east of upper Carbon
Junction (Rule 2.05.3(4)(a)).
2. The HEC -RAS output data provided by Goff Engineering and Surveying, Inc. appears to indicate that
several segments of the Carbon Junction Permanent Diversion are not adequately sized for the
design event. For all of the segments except 16 +00, it appears that the required top width of the
channel at the design flow water surface elevation is wider than the rip rap lined portion of the ditch
as constructed. DRMS independently ran a SEDCAD utility to size the channel segments, verifying
that the required flow cross sectional area exceeds the constructed channel dimensions. Please
review the HEC -RAS table and verify the required top widths for the channel segments. Where the
required top width /flow area exceeds the channel capacity (rip rapped portion) as constructed,
Oakridge Energy will need to redesign and reconstruct the channel and /or extend the channel lining
to accommodate the anticipated runoff volume and prevent scour along the sides of the channel
(Rules 4.05.4(2)(a) and (b)).
3. It appears that the runoff volume used for the Carbon Junction Permanent Diversion is based on the
previously approved design in the permit application, which may have resulted from modeling of the
site at maximum disturbance. Modeling for current conditions, using data from recent vegetation