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~. Mr. Clem Parkin -2- November 21, 1985 2. Expected dump material The material that it is proposed to dump at the portals is the tunnel muck from the tunnel excavation activity. As noted in our previous letter (dated August 5, 1985), it is reasonable to expect this material to exhibit a friction angle between 20 and 40 degrees. Assuming relatively free drainage, this range imp lies a stable angle of repose for the material of about 30 degrees. Note that this is very similar to the proposed foundation material. As the material will be end dumped, allowing segregation and movement of the larger lumps of material to the base of the pile, it is expected that the drainage of the pile will be good. 3. Portal #1 The proposed portal pad extension will result in the placing of about 3500 cubic yards of tunnel muck on the existing slope. The slope on which the pile is proposed is currently between 15 and 40 degrees, decreasing to the north. The proposed pile will be end dumped from the existing road edge. The dump is expected to extend out from the current lip of the road some 15 feet, and will be about 60 feet high when fully constructed. The foundation materials appear to have adequate strength to support this load. It is recommended that the pile be dumped in such a way that water flowing from the portal, and any surface water collected in the portal area, be diverted away from the pile, thus minimizing the water flowing through the dumped pile. This will maintain the full strength of the foundation material. It is possible that during dumping, there will be some movement of materials at the toe of the pile, and some surface cracking and displacement of the crest of the pile. This is normal in waste piles, but would not be expected to be severe in this case, due to the relatively small pile height, the relatively high foundation material strength, and the lack of groundwater in the foundation materials. In order to minimize these movements, it is recommended that the soil be stripped from as much of the surface on which dumping will take place as is feasible (note that the slope of the area precludes some stripping). This will allow the pile to bear on the rocky and more compact subsoil materials. The dumped materials will weather with time, and it is recommended that the surface of the pile be revegetated as quickly as possible, in order to minimize the potential for mass wasting. The pile could, in our opinion, be safely left at the dumped angle, which would be at the angle of repose for disturbed material of this type. The slope angle of the pile would in this case be similar to the natural slope angles in the vicinity. Terra Therma Inc