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Tegre Corporation <br /> Job No. 3124JS057 <br /> 6.0 RECOMMENDATIONS <br /> 6.1 General <br /> The recommendations contained in this report are based on our understanding of the <br /> project criteria described in Section 2.0, Project Description, and the assumption that the <br /> subsurface conditions are those disclosed by the borings. Substantially different subsurface <br /> conditions from those described herein may be encountered or become known. Any <br /> changes in the project criteria or subsurface conditions shall be brought to our attention in <br /> writing. <br /> 6.2 Geologic Hazards <br /> The primary geologic hazard with respect to development of the gravel pit is the stability of <br /> the excavation and embankment slopes. The potential impact of these features on the <br /> proposed improvements and off-site areas is discussed in subsequent sections of this <br /> report. No other geologic hazards are expected to affect any proposed impoundment, slope, <br /> embankment, highwall, or waste within the affected area. <br /> 6.3 Design Methodology and Assumptions <br /> Stability analysis were performed to check the factor of safety against deep-seated slope <br /> failures for various slope heights and inclinations. The stability analyses were performed <br /> using the commercial computer program Slope-W. The analyses were performed for both <br /> end of construction (short-term) and long-term conditions. The end of construction <br /> condition represents the situation immediately after excavation where the embankment <br /> mobilizes new shear forces in the soil mass. Excess porewater pressures induced due to new <br /> loading conditions do not have sufficient time to dissipate and the total stress conditions <br /> prevail. <br /> The long-term condition is the situation in which the slopes are considered to have been <br /> standing sufficiently long so that the excess porewater pressures have dissipated. Soil shear <br /> strength parameters for this condition are represented by the effective cohesion (c') and <br /> the effective angle of internal friction (0'). <br /> The rapid drawdown condition was not analyzed because the groundwater table was <br /> expected to be deeper that the maximum excavation depth. <br /> Analysis were performed for two different stratigraphic profiles. The first profile consisted <br /> of the cobble and boulder layer underlain by sandstone bedrock. This stratigraphic profile <br /> 6 <br />