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<br />- 24 - <br /> <br />Environmental and Economic Problems Associated with Debris Dams <br /> <br />Some of the specific problems inp1icit in the above include: <br /> <br />(1) Land requirements for debris basins large enough to even temporarily, <br /> <br />alleviate the problem will be quite high, and the basins, whether empty <br /> <br />or full, will have unfavorable aesthetic impacts. (2) If the system is <br /> <br />to remain effective, the basins will have to be cleaned out after each <br /> <br />major mud flood event. If this isn't done, the system will either <br /> <br />overflow and divert to new 'channels, or revert to the "straightpipe" <br /> <br />method described earlier which had very unfavorable impacts and possible <br /> <br />legal complications in the river flood plain area. (3) If the required <br /> <br />frequent clean-out of debris is performed, the operation will be very <br /> <br />expensive, and there will be serious problems in disposal of the debris <br /> <br />in a safe, economical, and environmentally acceptable manner. As de- <br /> <br />scribed earlier, the mudf10w debris is not suitable for road base or <br /> <br />fill material unless placed as an engineered fill. If it is placed as <br /> <br />a dumped fill, it could be expected to readily become unstable upon <br /> <br />wetting, and create the old problem at a new location. <br /> <br />If a catchment basin solution is proposed for such an area, the <br /> <br />details and long-term cost of maintenance and debris disposal as well <br /> <br />as original construction should be carefully worked out so that neces- <br /> <br />sary funding can be arranged and the responsibility for the system <br /> <br />'clearly understood. Experience with this sort of control system in <br /> <br />California and Utah has been generally disappointing in the long term <br /> <br />because of inadequate basin si~e and/or lack of necessary clean-out <br /> <br />when required. <br /> <br />GALLO BLUFF-ELl< MOUNTAIN AREA (3) <br />, <br /> <br />Area of Active Rockfall and Potential Large Landslides (3a) <br /> <br />Gallo Bluff is a steep and barren cliff that rises abruptly <br />