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. ~ 000715 -2- II. DURING SOIL MASS MOVEMENT 8. There is essentially a very small window of soil mass flow rates during which human effort can effectively mitigate the potential damming of a river. There are basically four possible stages of a slide. They are: 1. The sl ide does not move. No effort required. J 3.)1 I 2. 3. The slide moves very slowly. The river erosive forces will keep the river channel open. Human effort not needed, but could be helpful. The slide moves too fast and the river cannot keep the channel open. With the aid of men and machinery, such as draglines, scrapers, bulldozers, trucks, etc, it is possible that the channel can be kept open. However, this possibility is a function of the soil mass flow rate being less than the machine and water flow excavation rate. I_ .' 4. The slide moves faster than the river, human effort and machinery could handle. A dam is being formed. If a dam is being formed, there are still a few actions that could be attempted to mitigate potential problems. 'A. Install a pipe to handle part or all of the flow. Armco (phone 455-4080), Thompson Pipe & Steel Company (phone 292-4080) and other companies usually carry a large stock of several hundred or thousand feet of 24 inch, 30 inch, 36 inch, 42 inch, and 48 inch pipe and possibly 60 inch pipe. If the resources are combined, one or more lines could be placed. (See figures 1 through 6 for pipe discharge capacities) " }. " Additional drain pipes could be installed at a anticipation of the slide continuing to move. opposite side of the moving soil mass, a ledge pipeline installed. higher elevation in If there is rock on the could be constructed and a Potential Problems With the Corrugated Metal Pipe - 1. Placement - the condu it compacted. occur. The conduits ought to be carefully placed and the fill around should be selected NON-PERMEABLE material properly If the above items are not adhered to, a piping failure could I 2. Strength Limits - The corrugated metal pipes have a strength limit. The cover (height of embankment over the conduit) is limited, depending on the size (diameter) of the conduit, the gage (thickness of the metal). If the fill limit is exceeded, the conduits could collapse and cause the slide mass to fail.