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D04155GE We encountered similar materials in Test Borings Three and Four which were advanced near the tae of the slope at the gravel pit site. The materials encountered in Test Borings Three and Four were significantly denser than the materials encountered in Test Borings One and Two. We encountered free subsurface water in Test Boring Three at a depth of about twenty-five (25) feet at the time of our field work. We anticipate that the subsurface water elevation below the valley floor is at a shallower depth during the Spring runoff. It is unlikely that subsurface water accumulates in the talus soils since they are a free draining material, but the matrix of the material probably becomes very moist during runoff and after precipitation. It is difficult to predict if unexpected subsurface conditions will be encountered during -- construction. Since such conditions may be found, we suggest that the owner and the contractor make provisions in their budget and construction schedule to accommodate unexpected subsurface conditions. 3.0 SLOPE STABII,ITY ANALYSIS As discussed above the materials on the slopes above the gravel pit are composed chiefly of rock, therefore it is difficult to apply conventional analysis techniques to analyze the stability of the talus. The material is essentially cohesionless, therefore the angle of repose, in this case about twenty-five (25) to thirty (30) degrees, is the range of the estimated angle of internal friction of the bulk of the talus material. The geotechnical engineering information provided below represents our interpretation of; - the geomorphology of the project site, - topographic maps and areal photography data, - the subsurface information presented on our logs of the test borings, - the laboratory strength test data, - estimated strength characteristics based on the site geometry, - the computer models generated by the data, and, - the data generated by long-hand calculations. We have provided a discussion of our analysis below. Our cross section is located in the central portion of the raveling area and is based on relatively crude field measurement and use of topographic information. We analyzed the slope stability conditions on the project site using infmite slope methods and the modified Bishops Method of Slices. ~ritC7PY~ FIYCC~ ~SSIIL`L~ttPB CONSULTING GEOTECHNICAL ENGINEERS AND -4- MATERIALS TESTING