Normal hardrock tunnel excavation techniques can be used for the inner tunneling work. From the north, a movable head tunneling machine should be able to mine the relatively soft shales and sandstones. Drill and shoot tunneling can be used in the shales and sandstones and this is the most probable method with the granite in the southerly length of tunnel. Controlled perimeter drilling should be able to limit overbreak of rock materially in this granite. Smaller, more closely spaced perimeter holes should minimize overbreak in all the rock types.
Ephemeral streams flow from springs at both portals.
Within the mountain, only a minimum amount of water is likely to be found within the granite. More water may be encountered within the sedimentary rocks. After this perched water is drained, minor amounts of additional water will continue to flow. In order to provide a basis for estimating support requirements, loads were calculated for six divisions of rock quality as observed along the tunnel alignment. The primary tunnel support is presumed to be shotcrete for all but 500 feet.