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Mr. Richard Atkinson May 5, 1981 Page Two "Consultation -Slope Stability - Colowyo Streeter Canyon Fill near Meeker, Colorado" and dated 15 August 1979. No new field investigations to determine the engineering properties of the various materials in the fill and its foundation were made as a part of this study. Instead the stability was investigated for a range of values of the engineering properties of the fill and the colluvium. The properties selected for the study were obtained from the previous in- vestigations and knowledge of the properties of similar materials. In addition to investigating the stability for a range of engineering properties, the stability was also investigated for a range of saturation levels in the fill and finally, as discussed in a subsequent paragraph, the stability was studied for the "Colowyo" configuration and an "OSM" configuration. The results of the CTL/Thompson, Inc. study were summarized in Table 1 of the report, and this table is included herein as Attachement A. To be considered stable, the fill must have a long-term static Safety Factor of at least 1.5. By examining Table 1, it is seen that the "Colowyo" configuration meets or exceeds the criteria for all cases studied except Run Nos. 1A-2-2-1, 1A-2-2-2, and 1A-2-2-3 for Water Table Nos. 1, 2 and 3 respectively. For these cases, the angle of friction (,6) of the colluvium was assigned a value of 26 degrees and high saturation levels were investigated. In the hydrologic setting of Streeter Gulch along with the permeability of the fill it is our opinion that the saturation levels studied in these three cases cannot be obtained. The water levels for Water Table Nos. 1, 2, 3 and 4 are based on a saturation line in the fill having a slope of approximately 20:1 and daylighting on the surface of the slope approximately 150, 100, 50 and 10 feet respectively above the toe of the slope. I have inspected the toe of the fill a number of times and have found no indication of seepage at this location. In addition, there is no vegetation growth on the in-place materials below the toe thus indicating that the water table is below the root zone. It is, therefore, believed that after four years of operation there has been little, if any, build-up of the water table in the fill and the level is presently lower than the minimum level (Condition 4) investigated in the report by CTL/Thompson, Inc. It is, therefore, our opinion that, for all reasonable assumptions regarding the engineering properties of the materials and saturation levels, the spoil fill in Streeter Gulch is stable. The proposed change in the configuration of the fill would result in a higher and steeper fi II above EI. 6900 than originally proposed, but would produce no change below EI. 6900. It is believed that the effect of this change on the safety factor can be qualitatively evaluated by considering the following factors: 1. As noted in the report by CTL/Thompson, Inc., the results of analyses indicate that the most critical variables are the strength of the underlying colluvium and the location of the free water table. The change in the configuration should have no effect on either of these critical items.