Salmon Return When Dam Removed

Luckily for Drown, the Newport number 11 dam had just been removed. Salmon do not thrive in most dammed up rivers. The older concrete blockades have no fish "passages" or "ladders" for these fish that have to travel upstream from the sea to spawn.

While the Newport dam was the first dam to be torn down to restore fish to the river, it is not the first dam to be demolished in the United States. Since the 1970s, the U.S. government has ordered hundreds of small dams removed for safety or financial reasons.

Development activists say many more may have to be destroyed around the world as 40,000 large dams and 800,000 small dams reach the end of their useful lives: 50 years, on average.

Frank Thomas, the engineer in charge of the removal, says that it took about six weeks and more than $1 million to do the job.

Thomas, who confesses that he had never taken down a dam before or studied its removal, says the small size of the dam made it quite easy to remove. In industry terms, a dam is considered large when it is more than 15 meters high. This one measured five meters.

Water levels behind the dam were lowered as far as possible and a pipe was built to divert some of the water until it was possible to wade through much of the river. Sandbags were also piled high to create a "coffer" dam above and below the concrete dam to prevent more water from flooding into the reservoir. Then section by section, the dam was blown up with explosives or removed with the help of excavators.

But dismantling dams is not always that simple.

Take the nine-meter-high Fort Edwards dam on the Hudson River in New York state, which was removed in 1973 under instructions from the federal government. More than 23 years later, the problems caused by the dam removal have not been completely solved.

This was an old dam, built in 1817 as a timber structure filled with rock. It was close to collapse at the time of its removal.

Unlike the Clyde River dam which was built in a relatively rural part of the country, the Fort Edward dam was set in a heavily industrialized section of the Hudson that served paper mills and other manufacturing facilities.

"The engineers lowered the water level and removed the dam in sections, but they had no plans for river restoration, because the state's department of environmental conservation said the river would take care of itself," says Jake Niziol, an engineer at the Niagara Mohawk Power Corporation.

But the engineers failed to take into account the logging platforms made from earth, stone, and wood that loggers had once used. When the dam was removed, debris trapped by these platforms came rushing down the river and jammed the entrance to the Champlain canal. Other debris around Rogers Island became a menace to local boats.

The engineers also overlooked the waste discharged from industries above the dam. The sediment trapped behind the dam was full of highly toxic polychlorinated biphenyls (PCBs) that washed into the flowing river. Engineers had to work for months after the dam removal to get rid of the debris and to move the PCB-contaminated sediment to secure dump sites.

Today, much of the waste remains trapped in clumps of sediment which the government continues to monitor for fear that the river will break open these toxic graves.

One U.S. state with considerable experience in removing dams is Wisconsin, where approximately 30 dams have been demolished in the last two decades.

Stephen Born, professor of planning and environmental studies at the University of Wisconsin, has compared the planning issues that had to be tackled in the removal of these structures.

According to Born, local communities are concerned about the impact of the accumulated sediment. Large sediment loads that sweep downstream can cover fish-spawning regions, damage riparian areas, and change the very shape of water channels. Communities also worry that fish species that adapted to still waters would be wiped out. Also lost would be the wetlands around the reservoirs, as well as the waterfowl and other wildlife that live there.

But most of these impacts are only temporary, argues Born.

"Over time, systems will stabilize, excess sediment will be flushed out and pre-impoundment water quality will be re-established," he says. "Carefully planned removal and restoration procedures can help minimize these impacts."

According to Born's studies, the major impetus for dam removal has so far been the matter of cost. Eleven of the 14 dams that he examined were removed for financial reasons. For example, the estimated cost of repairing the Hayman Falls dams on the Embarrass River in Wisconsin was some $800,000, while the cost of removal was $272,000.

Rita Haberman of the Rivers Network in Oregon, points out that it will cost $11 million to remove the Savage Rapids dam on the Rogue River in her state, compared to between $17 million and $24 million to repair it.

Born adds that the environmental gains should be worth the trouble in the long run. Removal of the dam at the Black Earth creek and the Mount Vernon creek in Wisconsin more than 25 years ago has allowed the return of cold-water fisheries.

A recent report by the federal Bureau of Reclamation shows that the financial value of fishing that would be created by removing the Savage Rapids dam in Oregon could be as much as $5 million a year.