Electrical Power for Valdez and the Copper River Basin-1981

INTRODUCTIONThe Alaska District, Corps of Engineers (CE) is investigating theneed for electrical energy at Valdez, Alaska and surrounding communities.In performance of this investigation, the CE analyzedvarious alternatives and has identified the hydropower potential ofAllison Lake. A detailed feasibility analysis of this project isoccurring. This final Coordination Act report is being provided tothe CE by the Western Alaska Ecological Services Field Office of theU.S. Fish and Wildlife Service (FWS) to assist in that analysis.AREA DESCRIPTIONPort Valdez is located in the northeasternmost extension of PrinceWilliam Sound, and is surrounded by the Chugach Mountains. The Portis a steep walled, glaciated fiord which is 3 miles wide and extendsin an east-west direction about 14 miles. At its western end thefiord bends to the southwest and constricts to a one mile width atValdez Narrows before opening into the Valdez Arm of Prince WilliamSound. The steep mountain slopes extend beneath the water, forminga flat bottomed trough 400 to 800 feet deep. The shore of PortValdez is steep and rocky, except where river deltas and glacialmoraines project into the fiord. Port Valdez is the northernmostice-free seaport in Alaska, and provides the shortest and mostdirect route between tidewater and the interior of Alaska. Thesouthern terminus of both the Trans-Alaska Pipeline and the RichardsonHighway are located in Valdez.Approximately 70 earthquakes with a magnitude of five or greater onthe Richter scale have been reported at Valdez since 1898, and sevenearthquakes have equaled or exceeded a magnitude of eight. The 1964Alaska Earthquake and the attendant secondary impacts virtuallydestroyed the original town of Valdez on the Lowe River Delta. Anew' town has since been constructed on the delta of Mineral Creek onthe north side of the bay.Valdez enjoys a maritime climate, characterized by heavy precipitationand relatively mild temperatures. The average annual precipitationis 59.31 inches, including 244 inches of snow. The averageannual temperature at sea level ranges from 39° to 43° F, with arecorded maximum of 87° F and a minimum of minus 28° F. Local windsare influenced by the Chugach Mountains and follow two distinctpatterns: (1) from October through March or April prevailing windsare from the northeast, and (2) from May through September prevailingwinds are from the southwest. Maximum sustained winds of 58m.p.h. and gusts of 115 m.p.h. have been recorded at Valdez.Allison Lake (Figure 1) is located near the Trans-Alaska Pipelineterminal in a glacial cirque lying in a north-south trend. A glacialmoraine extends across the valley and impounds the lake at a surfaceelevation of 1,367 feet. The lake is 1.25 miles long, approximately0.3 mile wide, and over 190 feet deep. Several small glaciers andpermanent snowfields at the head of the valley drain into the lake.The outlet stream traverses a gentle gradient for approximately 0.6mile before descending steeply to sea level.