By Brian Yanity
Special to the Turnagain Times
Hydropower, or water power, uses the energy of falling water to turn a turbine and produce electrical or mechanical power. Hydroelectric power has been utilized in Alaska since 1893, when a small hydropower plant was built in Juneau to produce electricity. A micro-hydroelectric project has been proposed for Crow Creek, a mountain stream in an area off the power grid about 4 miles northwest of central Girdwood. Micro-hydropower is generally defined as having a generation capacity of less than 300 kilowatts (kW). A large amount of such micro-scale hydropower potential exits in both the Chugach Range and Alaska in general. The purpose of the micro-hydroelectric plant would be to displace electricity generated by single-home generators powered by diesel or gasoline, which is presently the main source of power in the Crow Creek area. These small-scale fossil fuel generation systems are polluting and subject to increasing fuel prices.
The proposed plant for Crow Creek could have a generation capacity of up to 125 kW, or enough power for the thirty or so existing homes along upper Crow Creek Road. Such an installation on Crow Creek could produce maximum output for about nine or ten months of the year. Given that the cold season corresponds to the period of peak demand for electric power, the design flow is based on the flows measured during December. The plant may have to be shut down during the period of lowest flow between February and early April, although the length of this “shutdown period” may vary depending on the flow of any given year. The natural flow of Crow Creek is too low for 125-kW of power generation during the low-flow phase of early spring, so more conventional diesel generation would have to pick up the slack during this period. During the peak flows of summer, only a small fraction of Crow Creek’s natural flow volume would need to be diverted into the plant. A hydroelectric plant on Crow Creek would be most practical as a run-of-river operation, with no dam large enough to store a significant amount of water. While a water storage reservoir would be an advantage for power generation by regulating the power plant intake flow, a true dam would not be practical for site due to the high cost of construction, as well as the environmental impacts of flooding the forested upper Crow Creek Valley.
The water intake structure for a micro-hydroelectric plant on Crow Creek would be located downstream from the Girdwood Mine, near where Crow Creek Road crosses the stream on a bridge. A diversion weir, or very small dam, would be constructed in the streambed to raise the water level and direct water into the plant intake. The plant intake structure would basically consist of a ‘silt basin’ to help remove sediment particles from the water, and a “trash-rack” to block larger objects such as rocks and sticks. The pipe that carries the water from the intake to the powerhouse, or penstock, would be buried along Crow Creek Road for a total distance of one mile, with a net head, or vertical drop in elevation, of about 550 feet. The hydroelectric plant would need a penstock pipe no larger than a foot in diameter to accommodate a design flow of about 5 cubic feet per second. The powerhouse would be a shed-type structure about the size of a pickup truck, and could be located near the Crow Creek Mine. Inside the powerhouse would be a Pelton-type water turbine driving an alternating current (AC) generator, power control electronics and other electrical equipment, as well as a diesel back-up generator. The electric cable to distribute the power would be buried next to the penstock pipe, also along the side of the road.
With a buried penstock pipe and a powerhouse shielded by trees, the hydroelectric project could easily be designed to be virtually invisible to passers-by on Crow Creek Road. Due to the natural barrier of waterfalls downstream from the proposed project site, near its confluence with Glacier Creek, no fish live in Crow Creek. No fish habitat impacts are expected, though a full environmental study needs to be carried out before site construction could be approved by state regulatory agencies such as the Department of Natural Resources, the Department of Environmental Conservation, the Department of Fish and Game. At the federal level, the project may also have to be approved by the U.S. Forest Service and the Federal Energy Regulatory Commission if any part of the hydroelectric plant is located within the boundaries of the Chugach National Forest.
Gold mining operations at the Crow Creek Mine during the first half of the twentieth century used mechanical hydropower in the form of hydraulic jets, which blasted away the creek bed and adjacent slopes. Water was diverted from Crow Creek into 22-inch steel pipes to feed the hydraulic nozzles. The Crow Creek Mine also used a Pelton water turbine to drive an air compressor, which can still be seen today. So in essence, a 21st century hydroelectric project on Crow Creek using a Pelton-type turbine would merely be a “resurrection” of the Pelton-turbine hydro-mechanical power plant installed at the same location a century before.
Ultimately, a neighborhood-scale hydroelectric plant can only be built with the organized support of the residents of the upper Crow Creek Road area. In February, Girdwood community activist Doug Wu met with the fledgling Upper Crow Creek Community Association (UCCCA) to present the concept of forming a utility cooperative that would own and operate the proposed Crow Creek hydroelectric project. Response from attendants at the meeting seemed very favorable. “I think it’s a no brainer” said UCCCA member Tom Swanson. Courtney Ruckel has lived on Crow Creek Road for five years, and with her husband Brandon is in the process of building a house in the Raven Estates area. Ruckel says that “we all live under Tesoro’s wing right now. Many of us supplement with solar power, but I think it would really empower our community to harness our main energy source--water. It would make us even more independent, greatly lower our use of fossil fuels, and possibly serve as a model for the rest of the state.”
Brian Yanity is an engineer working with an Anchorage-based Native corporation on rural Alaska energy projects. In December 2007, he completed a Master’s thesis about the Crow Creek hydroelectric project at the UAA School of Engineering.