REV104071

• Permit No: C1980001
• IBM Index Class Name: Revision
• Doc Date: 12/11/1995
• Doc Name: EDNA MINE PN C-80-001 TR 34 HYDROLOGY REVIEW
• From: DMG
• To: SUSAN BERGMAIER
• Type & Sequence: TR34
• Media Type: D
• Archive: No

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STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Deparlmenl of Natural Resources
1313 Sherman SL, Room 215
Denver, ColoniAo 80203
Phone I f03) 866 3567
FAY: 11031 83 8106
DATE: December 11, 1995
TO: Susan Burgmai4er
FROM: Erica Crosby
l~~r
RE: Edna Mine (C-80-001)
TR-34; Hydrology Review
~~
DEPARTMEIJT OF
NATURAL
RESOURCES
Roy Romer
Governor
James S Lochhead
E~ecmive Director
Michael8 Long
Division Direaa
Susan, per your request, I reviewed the hydrology calculations for the Moffat Pit area. I
have the following comments that should be directed to the operator;
1. There are several post-mine drainages depicted on Exhibit 3.4-4 that cross the
reclaimed contours. Unnamed Drainages #2, #3, #4, North Collection Ditch and
the South Collection Ditch all take sharp turns to the north crossing over the
reclaimed slopes. In comparison to the Pre-mining Topography Map, the ditches
appears unnatural crossing over the reclaimed slope. Generally, the long term
stability of permanent drainages routed across, rather than down, a slope is
questionable. When permanent diversions are constructed, the drainage design
should approximate the pre-mining configuration and blend in with the surrounding
area. Please re-evaluate the location of the drainages that cross the contours and
approximate a more natural drainage pattern.
2. P&M submitted hydrology designs for the Moffat Final Pit Drainage Area. The
Division could not locate the hydrology designs for Unnamed Drainage #1,
Unnamed Drainage #2, Unnamed Drainage #3, South Collection Ditch and the
North Collection Ditch. These drainages are all depicted on revised Exhibit 3.4-4.
Please provide the Division with the designs of these drainages, or direct us to where
they are located in the permit application.
3. Please inform the Division as to which culverts will remain on site in conjunction
with the post-mining topography. These culverts should be noted on Exhibit 3.4-4.