Preliminary report on the geology along the route of a proposed tunnel to develop hydroelectric power from Eklutna Lake, Alaska

Abstract

A preliminary investigation of the geology of the ridge north- west of the lower end of Eklutna Lake was made in the period June 11-18, 1947, by the writer, assisted by L. A. Hale. The purpose of this study was to obtain geological information bearing on the feasibility of constructing a tunnel through this ridge as part of a hydroelectric power development under consideration by the city of Anchorage. Several traverses were made up each side of the ridge in a belt judged to include the most logical routes for the proposed tunnel. For the purpose of localizing the study two tentative routes were selected, of which one would require the shortest possible length of tunnel, and tho other would be somewhat longer but would place the lower portal of the tunnel at a location considered to be the most favorable for the construction of the penstock and power plant. The first route extends northwestward from tho most westerly embayment on the north shore of the lake to the canyon about half a wile east of Pioneer Creek (see map) . The second route extends from tho same point in the lake to the nearest point on the steep slope southwest of the mouth of Goat Creek. The distance along the first route from the lake shore (elevation 862 feet) to the 800-foot contour on the north side of the ridge is 4.3 miles. The distance between corresponding points along the second route is 4.5 miles. The length of the tunnel would exceed these distances by amounts depending on the elevation and grade at which the tunnel is constructed.