Niagara Falls has meant honey moon since the late 19th century. Oscar Wilde made wisecracks about it; and a song about newlyweds shuffling off to Buffalo for a look at the falls is part of the classic 1933 musical, 42nd Street.

It's also the most powerful waterfall in North America, producing more hydroelectric power than any other waterfall in the world. They started making power here about the same time the honeymooners first arrived.

That means it's looking increasingly attractive to Ontario's government as an alternative power source as energy costs rise and the government struggles to make sure it has enough electricity.

The Ontario authorities have also vowed to shut down its coal-burning power plants.

Now the second largest tunneling project ever will bring more water to existing turbines on the Canadian side, generating enough new electricity to run 160,000 homes.

"The focus is on how to find as much clean and renewable energy as possible, and this fits the bill," says Emad Elsayed, vice president of hydroelectric development at Ontario Power Generation, which is owned by the Ontario government and operates the hydroelectric plants on the Canadian side of the falls.

The giant drilling machine, made by the Robbins Company of Solon, Ohio, will start boring through hard rock in early September. The machine cuts through about 50 feet a day. At that speed, the 6.4 mile tunnel will be ready in 2009.

At 47 feet in diameter it is 1 1/2 times the width of the Channel Tunnel between England and France. And it was a lot easier boring under the soft chalk of the English Channel than through hard rock 460 feet below Niagara Falls.

The $535-million tunnel will take 17,500 cubic feet of water per second from the Niagara River above the falls, to the Sir Adam Beck generating station below the falls.

"We are in effect adding more fuel by adding more water, making sure the existing turbines run at top capacity," says Mr. Elsayed.

The falls on the US side produce even more hydroelectric power than the Canadian side. All that water diversion means there is less water flowing over the falls. Hydroelectric projects on both the American and the Canadian sides divert 50 percent to 75 percent of the water in the Niagara River into tunnels to run turbines.