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~p~ p 1 1995 <br />4.0 Rockfall Hazard Mitigation ~eo~°9y <br />p\v~s~0° °~ M~ne~a~s & <br />This section describes options investigated to mitigate the hazards identified from the <br />CRSP modelling work. Options considered included; <br />• construction of catch fences <br />• temporary or permanent re-routing of sections of the road <br />• excavation of rock catch areas and/or construction of soil berms <br />combinations of the above options. <br />The use of catch fences was ruled out at an early stage in the study when the size of <br />potential rockfall blocks became apparent. Fences to arrest blocks with masses on the <br />order of 900,000 Ibs are not available from existing manufacturers and would be difficult <br />to obtain and maintain. <br />The scope of work for the hazards mitigation task was originally defined assuming that <br />the existing road would, temporarily, be re-routed onto the old alignment at the western <br />end of the site, in morphological zones 1-3. This option has been modified to include: <br />1. Permanent relocation of the road in morphological Zones 1 and 2. <br />2. Construction of mitigative measures above the road in Zones 3 to 5, Zone <br />9. and Zones 10 to 11. <br />4.1 Alternative Catch Areas/Berm Configurations <br />Several alternative catch area/berm configurations were analyzed for each of the sections <br />in Zones 1 to 11. The analyzed alternatives are shown in Figure 4-1 and included: <br />• Construction of a ten foot deep trench adjacent to the road. Removed <br />material is to be mounded over the road for sections of the road that could <br />be relocated. <br /> <br />20 <br />