PERMFILE135332

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 7/19/2002
• Section_Exhibit Name: Exhibit 48-2 Modified Gravel Section & Construction Recommendations Batch Weigh Loadout Haul Road
• Media Type: D
• Archive: No

thWest Colora
Geote<hnical /Environmental Engineering • Materials Testing
May 16, 2002
Twentymile Coal Company
29515 RCR q27
Oak Creek, CO 80467
Attn: Mr. Rick Mills
Job Number: O l -5023
Subject: Modified Gravel Section and
Construction Recommendations, Balch Weigh
Loadout Haul Road, Foidel Creek Mine, Routt
County, Colorado.
Gentlemen:
As requested, NWCC, Inc. (Northwest Colorado Consultants, Inc.) has prepared this report outlining
modified gravel section recommendations for the Batch Weigh Loadout Haul Road to be constructed at the
Foidel Creek Mine (Twentymile Coal Company) in Rout[ County, Colorado. It should be noted that our
firm previously provided gravel section and construction recommendations for this haul road in a report
prepared under this job number and dated October I5, 2001. The gravel sections have been modified since
the proposed traffic loadings have been significantly reduced.
Modified Gravel Section Recommendations: Based on our conversations with your office, it is our
understanding that the proposed haul road will be subjected to a fully loaded 10-ton tandem dump truck one
time per week and by up 10 pickup truck trips per day. We had originally provided gravel section
recommendations based on the assumption that the roadway would be subjected to fully loaded 100 ton
Euclid haul trucks.
Based on the assumed subsurface conditions at the site, the given traffic loadings and our experience with
similar roadway projects at this mine, we recommend that the proposed haul road be constructed with a
gravel section wnsisting of 4 inches of base course gravels overlying a minimum of 8 inches of subbase
(pit run) sands and gravels. However, if [he subgrade is improved by placing a layer of Geogrid, such as
Tensar BXl 100 or an equivalent product over the properly prepared subgrade soils, then a gravel section
consisting of a minimum of 8 inches of I''/z (CDOT Class V) base course gravels can be used.
Based on the size of [he vehicles using this roadway and the number of trips made per day, we recommend
that the gravel section be constructed to a minimum width of 24 feet.
Construction Recommendations: The fill materials placed in the roadway embankments should be
uniformly placed and compacted in 6 to 8 inch lifts to at least 95% of the maximum modified Proctor
density and within 2 percent of the optimum moisture content determined in accordance with ASTM
D 1557.
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2580 Copper Ridge Drive, P.O. Box 775226 • Steamboat Springs, CO 80477