Preliminary report on the potential waterpower of Grant, Ptarmigan, Cooper and Crescent lakes on the Kenai Peninsula, near Seward, Alaska

Abstract

Grant, Ptarmigan, Cooper, and Crescent Lakes, located in the Kenai Mountains in the upper portion of the Kenai River Basin, approximately 25 miles to the north of Seward, present favorable opportunities for the development of waterpower. Grant and Ptarmigan Lakes can be made readily accessible by roads from the Seward-Anchorage Highway which in this area practically parallels the Alaska Railroad; and Cooper and Crescent Lakes by access roads from the Sterling Highway. Geologic conditions are favorable for the construction of the various elements of a power development although some special problems may be encountered. The power sites are located in areas of severe winter temperatures, -30° to -40° or less in most winters. This climatic feature must be given due consideration in the design of the various structures required for a power development. Streamflow records are available for a 7-year period for Grant and Ptarmigan Creeks and for a 5-year period for Cooper and Crescent Creeks. Only short and incomplete records of precipitation are available in the area of the power sites but records have been kept at Seward for 30 years. The precipitation at Seward during the periods for which streamflow records are available was, in general, less than average. It seems reasonable that similar conditions would prevail over the upper Kenai Basin. Consequently, the available stream-flow records cover a period of less than average precipitation and estimates of potential power based on these figures probably are on the conservative side. Only regulated flow is considered in this report. Each of the four lakes is a favorable storage site. Adequate capacity for complete regulation of the flow on a year-to-year basis or over a period of several years can be obtained by the construction of dams ranging in height from 20 to 50 feet. Water from the reservoirs can be conveyed to the powerhouses through conduits, tunnels, or pipelines of reasonable length. The total estimated potential power for the four lakes is 11,000 kilowatts for 90 percent of the time and 14,000 kilowatts for 50 percent of the time. Transmission line distances to Seward range from 22 miles for the Ptarmigan Lake power site to as much as 50 miles for the Cooper Lake power site that would be located on the Kenai River. The transmission line distance to Anchorage will approximate 100 miles, depending on the route selected.