REV13797

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 6/2/2003
• Doc Name: Review Memo on SEDCAD Designs & nomographs
• From: Joe Dudash
• To: Jim Burnell,Sandy Brown
• Type & Sequence: MR296
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Depanment of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
fAX: [phone]
DIVISION OF
MINERALS
GEOLOGY
RECLAMATION
MINING•SAFETY
DATE: June 2, 2003
Bill Owens
Governor
TO: Jim Burnell, Sandy Brown
FROM: Joe Dudash~~
RE: West Elk M e, ermit No. C-80-007, Mountain Coal Company
Minor Revision No. 296, Sedcad Designs and Nomography for
Culverts
Greg E. Walther
Executive Director
Ronald W. Cattany
Division Director
I have finished my review of the Sedcad designs and nomography for MR-296. The
submittal uses peak flows that are presented in Table 44E, found in Exhibit 66 of Volume
8A-1. I have several comments:
Table 44E, in Volume 8A-I, needs to be revised to show that the diameter of
culvert C2R-4 is 30 inches, not 36 inches.
2. Table 44E in Volume 8A-1 shows that culvert C2-13 is a 24 inch diameter half
pipe and a 24 inch diameter full pipe. However, the designs show that a 24 inch
diameter full culvert is needed. The 24 inch diameter half pipe would appeaz to be
insufficient.
The nomograph for culvert C2-SA uses a peak flow of 18.3 cfs, instead of the
correct value of ] 5.62 cfs. However, this discrepancy only decreases the
headwater depth from 1.1 to about 0.91. The culvert size still passes the design
flow. I don't think it is worth revising the nomograph.
4. As with all culverts that use a headwater factor in their hydrology designs, the
height above the top of the culvert inlet that water can rise up to should be
checked in the field to make sure it is what the design says it is.
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