Beaver Falls Hydroelectric Project
The Beaver Falls Hydroelectric Project (Beaver Falls Project) is located on Beaver Falls Creek, approximately 6 miles northeast of the City of Ketchikan, Alaska. The Project occupies federal lands within Tongass National Forest and consists of two developments:
The Project provides power throughout the Ketchikan Gateway Borough and is considered Ketchikan Public Utilities’ most important generation asset, as it provides approximately 30 percent of their total electric generation.
The Silvis Development includes the naturally occurring Upper Silvis Lake, Upper Silvis Dam, concrete spillway, power conduit consisting of a tunnel and penstock, a single-unit powerhouse, and a transmission line. The Silvis Powerhouse is located at the southwest end of Lower Silvis Lake, near the natural outlet of Upper Silvis Lake. The powerhouse is a reinforced concrete structure, approximately 30-feet by 40-feet by 20-feet high, and houses a 2.1 MW Francis-type, horizontal shaft turbine-generator unit.
The Beaver Falls Development includes the natural occurring Lower Silvis Lake, Lower Silvis Dam, concrete spillway, Beaver Falls Creek Diversion Dam, two power conduits, a powerhouse containing three active and one decommissioned generating units, a switchyard, and substation. The Beaver Falls Powerhouse is located along the shoreline of George Inlet. The powerhouse is a reinforced concrete structure, approximately 30-feet by 147-feet by 25-feet high, and contains four horizontal shaft Pelton generating units, one of which has been decommissioned.
There are no transmission lines at the Beaver Falls Powerhouse. At the powerhouse, the Project is interconnected to KPU’s transmission system at the Beaver Falls Substation.
Upper and Lower Silvis Lakes are operated for hydroelectric generation only. Upper Silvis Lake provides the primary storage for the entire Beaver Falls Project and is managed between elevation 1,154 feet mean sea level (msl) and 1,055 feet msl to maintain Lower Silvis Lake’s elevation. Lower Lake Silvis is kept near a maximum elevation 827 feet msl to maximize generation head while avoiding spill.
KPU does not currently propose any operational or infrastructure changes to the Beaver Falls Project.