OCR Text |
Show Just above the observer « e head can be noticed a second barrier that was designed to be a twin of the upper one. The lower barrier, instead of being constructed 30° off the fali line, was constructed at right angles to the fali line so is not as effective as it should be. Instead of di-verting the snow, it is simply a dam. Under conditions of high speed snow, dam type barriers are very inefficient. It is our opinion that the higher barrier should be backed up by further construotion, preferrably mounds. Distance between the highway and the diversion barrier is approximately 800 ft. This área is a large gentle transition zone and appears to have large amounts of easily worked soil mantle so that by constructing mound type barriers, the highway may be afforded complete protection from any slide released from the mountain. This type of barrier was chosen from the standpoint of economics. The catchment basin is very large, and ali above timber line, therefore re-forestation is out of the question. Betention barriers in the catchment basin were considered, but the large number required would be too costly. The windward slope leading up to the catchment basin in the release zone is situated so that snow fences could be constructed to make the snow drop out before reaching the deposition zone, thereby reducing the volume of snow at the release zone, but again the amount of snow fence required was beyond the allocated budget of the State Highway Department. k |