Taking another look at Susitna hydropower
To some an elegant dream but to others a gargantuan nightmare, the prospect of a mega hydropower project on the Susitna River, in the upcountry somewhere between the Talkeetna Mountains and the Alaska Range, periodically reappears within the sights of those seeking solutions to the power generation issues facing Alaska’s Railbelt.
Originally envisaged in the 1970s in the form of a variety of dam possibilities on the upper Susitna River, and investigated in some detail as a two-dam project in the early 1980s, potential Susitna hydropower has recently received further scrutiny in a study conducted for the state by HDR Alaska Inc. This new study has dovetailed into the development of a draft Alaska Railbelt regional integrated resource plan by consultants Black & Veatch for the Alaska Energy Authority.
The new assessment considered six possible hydropower dam concepts on the upper Susitna, with power capacities ranging from 380 megawatts to 1,880 megawatts and with estimated construction costs ranging from $3.6 billion to $10 billion. Five concepts involve the building of a dam in the area of Watana Creek, in remote territory south of the Denali Highway, while one concept involves a dam between Watana and Devil’s Canyon, a few miles east of where the Alaska Railroad veers north from the Susitna River.
And most of the projects are large in relation to the scale of power demand in the Alaska Railbelt.
Reduced scale “When the Railbelt integrated resource plan (project) started we realized and they told us that most of the projects we were looking at … were too big and too expensive,” said Bob Butera, an HDR civil engineer, during a Dec. 10 AEA-organized presentation of a draft Railbelt integrated resource plan. “So essentially we looked at lower cost alternatives … and we looked at determining what’s called the firm capacity, which is the amount of power that a project can produce on a continual basis.”
Butera said that either of two Susitna projects looked to fit within an integrated resource plan scenario that assumes a high rate of growth in Railbelt electricity demand and that requires at least 50 percent of the power to be generated from renewable energy sources. One of those projects is a 600-megawatt, $4.5 billion concept called “low Watana non-expandable.” The other project is an expandable $4.9 billion version of the 600-megawatt “low Watana” system.
And the Susitna hydropower concepts are well understood, appear to be technically feasible and appear to have manageable environmental and seismic risks, Butera said.
Chakachamna? However, Black & Veatch has concluded that, for a base-case Railbelt power scenario with modest growth in power demand, considerations of cost and scale favor the construction of an alternative hydropower system that would draw water from Lake Chakachamna, next to Mount Spurr on the west side of the Cook Inlet. But the feasibility of the Chakachamna hydropower concept has been less thoroughly investigated than that of Susitna hydropower: Black & Veatch has recommended further assessment of both Chakachamna and Susitna hydropower, to enable a fully informed decision on which project to pursue.
So, a major dam across the Susitna River remains a future possibility.
—Alan Bailey
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