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' these alternatives must first be viewed from the standpoint of <br />safety and then should be considered from a purely economic point <br />of view (i.e., are the measures proposed cost effective when <br />compared to the cost of future incidents in terms of damage to <br />equipment and facilities and lost production). With regard to <br />1 sliding above the fan portal, alternatives for future treatment <br />fall into two broad categories: <br />i <br />1. Stabilization of the fan portal area. <br />' 2. Relocation of the fan portal. <br />' Regarding stabilization, past investigations have shown ancient <br />' slide debris to be as thick as 60 feet near the bench level. <br />Although it is speculated that this material becomes considerably <br />thinner above the bench, it is still likely to be economically <br />' unfeasible to attempt to stabilize all of the existing slide <br />debris. Aowever, it may be feasible to stabilize the near <br />' surface materials above the fan portal in order to provide <br />protection against the recurrence of similar shallow slides in <br />' the future. Construction of a buttress at the toe utilizing <br />either gravity or tieback systems along with the reconstruction <br />and drainage of the existing slide area above this buttress area <br />' to a stable slope configuration should be considered. <br />' Yet another measure which warrants consideration is the drainage <br />' and de-pressurization of the near surface bedrock to prevent the <br />"injection" of water into near surface soils at locations where <br />the thickness of soil cover is thin. Drainage would be <br />' 7 <br />