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Environmental Consultants, lnc. <br />January 14, 2003 <br />Mr. John W. Rozelle <br />Land Manager <br />Lafarge West, Inc. <br />1590 W. 12's Ave <br />Denver, CO 80204-3410 <br />RE: Slope Stability Analysis for Suttle Ditch Relocation <br />Dear Mr. Rozelle: <br />Greystone Environmental Consultants (Greystone) has completed its stability analysis of the <br />proposed relocation of the Suttle Ditch at your River Valley Resource Property near Steamboat <br />Springs, Colorado. The analysis was conducted using normal physical properties for sand and <br />gravel pit slopes - no site-specific samples or laboratory analyses were available. Based upon our <br />experience and the information provided, the proposed 3H:1V pit slope and 10-ft setback from <br />the pit slope crest will adequately protect the Suttle Ditch from slope failure. The following <br />paragraphs summarize the results of this study. <br />OBJECTIVE <br />The objective of this analysis was to evaluate the stability of an excavated highwall associated <br />with relocation of the Suttle Ditch at Lafarge West, Inc.'s River Valley Resource Property, <br />located near Steamboat Springs, Colorado. <br />ASSUMPTIONS <br />Based on the information provided by Lafarge, assumed normal and typical material parameters <br />were selected, as listed in the following table: <br />REPRESENTATIVE MATERIAL ANALYSIS <br />PARAMETERS <br />Soil Material Sand and gravel mix <br />Moist Soil Density 139 lb per cubic foot <br />Internal Friction Angle 30 degrees <br />Cohesion 0 Ib per square foot <br />The material is represented as a sand and gravel mix that will be cut and backfilled during road <br />construction and ditch relocation to achieve the desired 3H:1V slope. The ditch will be <br />constructed no closer than 10 feet (horizontal) from the mining face (Figure A-3). A static <br />analysis was conducted with a conservative piezometric surface connecting the ditch bottom and <br />the toe of the slope. The project site is located in an area with low seismic potential (Zone 1); <br />therefore, no pseudostatic analysis was done. <br />5231 South Quebec Street • Greenwood Village, Colorado 801 I 1 <br />Phone (303) 850-0930 • Fax (303) 721-9298 <br />