enlarge The Lincoln County News/Greg Foster

John Douglas, Riverbank Power Corp. CEO, explains his underground hydropower proposal to the Wiscasset Planning Board last month. “Community support is obviously a big factor here,” he said.

Click here to see a diagram of the project.

TO WATCH a video of the project, click here.

Wiscasset is being considered for the largest energy development proposal – and potentially the largest development project of any kind – in the history of the state.

A Toronto entrepreneur who has developed Canadian wind farms has floated the idea of building a massive $2 billion underground hydropower station at the old Maine Yankee nuclear power station site.

The project would be one of the first of its kind anywhere.

The proposal raises questions about impacts on the Back River and groundwater, and it would use as much energy as it creates.

But local and state officials, as well as environmentalists and others who fought an earlier proposal for a $1.5 billion coal gasification plant at the site, said the idea has a lot of appeal because of its potential to create jobs and help develop the state's clean-energy infrastructure.

"It's something new. It's innovative," said Arthur Faucher, town manager in Wiscasset.

"If this project proves to be as good as it sounds, that would be a good thing for Wiscasset, for Maine and for the environment," said Sean Mahoney, a lawyer with the Conservation Law Foundation.

The plans presented by Riverbank Development Corp. in recent meetings here and on its Web site (www.riverbankpower.com) call for the construction of cavernous reservoirs and a three-story-tall power plant carved out of the bedrock 2,000 feet beneath the ground. At times of peak electricity demand, tidal water from the Back River would surge straight down four large chutes, through power-generating turbines and into the caverns, each of which would be 100 feet tall and 1,000 feet long.

Then, when electricity demand is low and there is excess power going into the grid, the water would be pumped back to the surface.

The plant – called an Aquabank – would operate in six- to eight-hour bursts and generate 1,000 megawatts of power, more than Maine Yankee used to and more than all of Maine's hydro dams combined. It would make a profit by using power when the price is low and selling when it's high.

Although the system would use at least as much energy to pump out the underground reservoirs as it generates when filling them, experts say the power-storage system could help Maine make the shift from fossil fuels to cleaner renewable power sources.

"It's not adding new energy to the state of Maine," said Habib Dagher, a professor of engineering at the University of Maine and a proponent of offshore wind power. "But it's like buying a big battery for your house and storing energy in it. It's a huge battery."

There are pump-storage systems around the world that use surface reservoirs, but none below ground, he said.

The idea could be especially valuable because of the state's goal of developing 3,000 megawatts of wind energy by 2020, according to Dagher and others.

Because wind turbines spin whenever the wind blows, including at night, rather than when the energy demand is greatest, wind farms alone can't entirely replace fossil fuel plants. A system like the Aquabank can store that energy for the peak demand, "a very beneficial thing potentially to the offshore wind market," Dagher said.

FOURTEEN SITES IN THE RUNNING

Riverbank's chief executive officer, John Douglas, is pitching the project as Maine's wind battery.

"This project is entirely consistent with what the state is trying to do," Douglas said in an interview Friday.

The use of wind or renewable power to pump out the reservoirs at night would make the Aquabank a clean source of carbon-free power, according to the company.

Douglas spent several days meeting with community leaders, state officials and environmentalists in midcoast and southern Maine late last month, and plans to return for two days this week.

"Community support is obviously a...