2002-05-13_PERMIT FILE - C1981041 (2)

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n U PROJECT DESCRIPTION This report presents the results of our geotechnical evaluation performed to determine the general subsurface conditions of the site applicable to re-constmction of the existing embankment of the sedimentation pond, designated RSN Pond l2, Roadside North Portal, Cameo, CO. A vicinity map is included in the Appendix of this report. To assist in our exploration, we were provided with some cross sections of the pond embanlanent from Powderhom Coal Company, dated 6-23-97. The Boring Location Plan attached to this report is based on that plan provided to us. We understand the proposed re-construction «1ll im~olve the existing dike of Pond 12 on the south side of the pond, separating the pond from the c-: -.e Coal Creek Flow Channel In addition, the floor area of the pond will require reworking. This projec~ :continuation of a Geotechnical Evaluation performed by Lincoln DeVore, Inc., ]ob !t 86014-2164-J, 5-28-97. This previous report was concerned with the small dike on the east • side of the pond which sepazated Pond 12 from Pond 5. Thc existing earth and embanlanent, sepazating Pond 12 from the Coal Creek Drainage Channel is approximately 300 feet long and is approximately 5 to 7 Ccet high on [he north slope (Pond 12 side) and behvcen 22 to 25 fcet high on the south side (Coal Creek Drainage Channel). This existing embanlonent and general slope configuration has been in place for several years. The width of the embankment has been reduced over the years and is planned to be reduced further due to a need for borow material and to increase the capacity of Pond 12. At the base level of Pond 12, the embankment width is to be reduced from between 75 to 100 feet to approximately 50 to 60 feet. The upper portion of the embankment, at the maximum water level of 4803 feet is to be reduced from a range of 40 to 70 feet to 1 ~ to 25 Ceet wide. At the final embankment elevation, allowing for 1 foot of free board (4804 feet), the embankment width should be approximately 12 to 18 feet wide. If the proposed site use or type of construction proposed is changed, Lincoln DeVore should be contacted to deternine if the information in this report can be used for the new constmction without further evaluation being required. • PROJECT SCOPE The purpose of our exploration was to evaluate the surface and