PERMFILE59327

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 5/27/2004
• Section_Exhibit Name: Exhibit 70A Refuse Pile Expansion Construction Plan
• Media Type: D
• Archive: Yes

Environmental Consultants, Inc.
April 30, 2004
Mr. Henry Barbe
Mountain Coal Company LLC
P. O. Box 591
5174 Highway 133
Somerset, CO 81434
Re: West Elk Mine
RPE Ditch and Rip-Rap Sizing
Dear Henry:
We have completed the sizing and rip-rap specifications for the south-side ditch of proposed
Refuse Pile Expansion Area (RPE) at the West Elk Mine. The ditch was sized in three reaches,
RPE-1, RPE-2, and RPE-3, as shown on Figure 1. Only RPE-2 requires rip-rap.
The analysis was prepared using the Sediment, Erosion, Discharge by Computer Aided Design
(SEDCAD Version 4) developed by Ms. Pamela J. Schwab of Civil Software Design and Dr.
Richard C. Warner, agricultural Engineering Department, University of Kentucky. The analyses
were based on a site plan provided by Mountain Coal Company and design parameters
developed for the Refuse Pile Surface/Toe Drainage Ditch in Sylvester Gulch from your existing
permit.
The design parameters used in the SEDCAD analysis are:
• 2.8 inches fora 100-year 24-hour precipitation event.
• A curve number (CN) of 57 selected for grass-oak cover, in good condition for
undisturbed slope areas.
• A CN of 91 selected for no cover on disturbed refuse pile.
• Soil is a clay loam soil with a fraction of cobble size material in hydrologic group C.
• RPE ditches 1, 2, and 3 were designed with 2.5:1 side slopes.
• RPE Ditches 1 and 3 are unlined erodible channels; Ditch 2 is lined with rip-rap.
• RPE Ditch 3 includes a flow of 22.21 cfs from the existing Refuse Pile Surface/Toe
Drainage Ditch.
The RPE ditch designs are included in the attached printout of the SEDCAD4 analysis, and
summarized in the following table.
5231 Sou[h Quebec Street • Greenwood Village, Colorado 80111
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