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12 1= v <br />4. Although surface and ground water was not believed to be a contributing factor in <br />the pit slope failure, it may be a contributing factor to the stability of the current - <br />slope and any final slope design. Surface water entering the existing fissures and <br />cracks can accumulate and produce pore water pressures that increase the driving <br />force and reduce the internal strength. Therefore, the company might consider <br />diverting surface water, particularly from the secondary scarp area, to prevent it <br />from causing further movement and instability. The final slope design should <br />consider the effects of seasonal groundwater, if any, on long-term stability. <br />5. The selection of an appropriate safety factor for mass slope stability depends on <br />several factors. Lower safety factors may be appropriate when the consequences <br />of failure are not significant and the accuracy of data used in the analysis, such as <br />the geological features, geometry, and material properties, can be determined <br />o- confidently. However, higher safety factors are prudentrwhen slope movements <br />or failure have the potential for causing loss of human life or considerable <br />economic loss. _- <br />Report Prepared By: <br />0 <br />Paul J. Donahue, P.E. <br />Civil Engineer <br /> <br />Eric J. Gottheld, P.E. <br />Civil Engineer <br />Report Approved By: <br />?'' ,, d ' <br />Darren J. 1 k, P.E. <br />Supervisory Civil Engineer