THE demolition of Newport Number 11 marked a turning point in hydro- engineering history. It was, say campaigners, the first dam to be removed for purely environmental reasons. It took two years of intensive lobbying by people living near the dam on the Clyde River in Newport, Vermont, to convince the US government that Number 11 had to go. They would rather have fish in their river than the 2 megawatts of power that the dam generated, they said. Even children turned out at the hearings. “If I could catch a salmon,” 10-year-old Kate Grim told the assembled adults, “I’d turn my television off, my electric blanket and my stereo, so that we could save electricity.”
Last autumn, the dam disappeared with a bang and a roar. For the previous forty years it had stopped fish reaching their spawning grounds. But within a few weeks of the dam’s disappearance, salmon was back on the menu in restaurants upstream.
Victory on the Clyde has given new impetus to a wave of dambusting activism that is sweeping the US. In Maine, for example, the Kennebec Coalition is fighting to have the Edwards Dam on the Kennebec River in Augusta destroyed. Several campaigns are under way to remove dams on the Rogue River in Oregon and the Snake River in Idaho. And plans are being drawn up for a huge project to dismantle two dams on the Elwha River in Washington State (see “Watch this space”). Local groups have now joined forces with national organisations that share their aims, such as Trout Unlimited and American Rivers, to take their campaign to Washington DC. Under the umbrella of the Hydropower Reform Coalition, they are challenging federal government plans to relicense some 500 hydroelectric dams that have been operating for 50 years.
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Drop in the ocean
But this is a mere drop in the ocean. Worldwide, there are 40 000 “large” dams (defined as more than 15 metres in height) and more than 800 000 small ones. Many were built in the first half of this century and are now approaching the end of their useful lives. Repair and demolition are both expensive, so the world’s poorer countries have yet to face up to the problem. Environmentalists argue, however, that removing dams is not only cheaper than repair, it can also generate income from fishing and tourism.
Activists in Tasmania want the dam on the Franklin River dismantled to uncover the pink quartz beaches of Lake Pedder which were submerged by the reservoir (“Can Lake Pedder resurface?”, 91av, 3 September 1994, p 14). And in France, the environmental group SOS Loire has convinced the national government to remove the Saint Etienne du Vigan Dam on the upper Allier and the Maisons-Rouges on the Vienne River to restore passages for migratory fish through the upper Loire Valley.
However, if the environment is to benefit from dam destruction, say campaigners, engineers must consider the entire river system, not just the concrete structure itself. Small dams like the 5-metre-high Newport Number 11 may pose relatively few problems. It took about six weeks and cost just over $1 million to remove. First the engineers lowered water levels behind the dam as far as possible and built a pipe to divert incoming water past the dam. They created a dry area in which to work by building sandbag dams on either side of Number 11. Then, section by section, the dam was blown up with explosives or bulldozed away.
But it is not always this simple to dismantle dams, particularly large ones. And the environment may actually be degraded as a result. A notorious example is the nine-metre Fort Edwards dam on the northern stretch of the Hudson River in New York State, which was removed in 1973. Even today, environmental problems created by the demolition persist.
Close to collapse
Fort Edward stood on a heavily industrialised section of the Hudson that served paper mills and chemicals and engineering companies. Built in 1817 as a timber structure filled with rock, it was close to collapse at the time of its removal. “The engineers lowered the water level and removed the dam in sections,” says Jake Niziol, an engineer with the Niagara Mohawk Power Corporation, which owned the dam. “But they had no plans for river restoration because the state department of environmental conservation said the river would take care of itself.”
How wrong that assumption was. For months after the demolition, engineers had to remove debris washed downstream in the newly free-flowing river. Logging platforms made from earth, stone and wood, that jutted out into the river below the dam, had been abandoned over the decades. These were swept away by the current and jammed the entrance to the Champlain Canal. Other flotsam wreaked havoc with shipping downstream around Rogers Island. A massive operation had to be mounted to remove sediment washed into the river from behind the dam. This contained toxic polychlorinated biphenyls (PCBs), which had been used as coolants in transformers and dumped in the Hudson. Even now, much of this waste remains trapped around vegetation and other obstructions downriver in toxic “graves” that the government continues to monitor for fear that the river will eventually break them open.
In retrospect, say engineers, this problem could have been avoided by “capping” the sediment with concrete so that toxic material is separated from the flowing water by a protective shell. Environmentalists are keen to ensure that such measures are taken in future, but the engineers are only now bringing together the expertise gained from two decades of removing dams. The American Society of Civil Engineers is looking at the lessons learned so far and plans to publish technical guidelines for dam removal on 1 July. These will recommend that sediments are either removed or diverted away from rivers through alternative channels.
Meanwhile, according to Stephen Born, professor of planning and environmental studies at the University of Wisconsin, local communities want to ensure that dam removal improves river environments rather than degrades them. Wisconsin has more experience of dam removal than most states, having dismantled around thirty in the past two decades.
Toxic depths
Born’s research, published last year, shows that the people of Wisconsin are particularly worried about sediments. Even without industrial pollution, these may be toxic. In a reservoir’s dark depths organic material decomposes, using up oxygen and leaving the water acidic. This in turn reduces heavy metal salts to insoluble metals; iron, manganese and other metals accumulate in sediment at levels that kill wildlife.
And sediments don’t have to be toxic to wreak destruction. Once liberated they may wash downstream, covering fish spawning areas, damaging river habitats and changing the shape of water channels. In addition, when reservoirs are drained, all that is left is often a large foul-smelling mudflat.
Even with the most sensitive restoration of a river, there’s an environmental price to be paid. Wildfowl and other wildlife that were attracted to the wetlands created around reservoirs will be lost. As fish such as salmon return, other species adapted to stiller waters will go. Reservoir water is cooler then free-flowing water in summer and warmer in winter, so it has a more constant temperature than flowing water. Fish species adapted to more constant temperatures take up residence even several kilometres downstream if water is released regularly. But once the natural flow is restored these fish can be lost, while those that rely on thermal cues for their breeding cycles may return.
But for many species it is already too late. Almost half the stocks unique to the Pacific coast of the US, for example, have died out in the past century, often because of dam construction. Of the 214 stocks that remain, 169 are at high or moderate risk of being wiped out.
Some of the environmental disruption caused by dam-busting is only temporary. “Over time, systems will stabilise,” says Born. “Excess sediment will be flushed out and pre-impoundment water quality will be reestablished.” He argues that a carefully planned strategy for sediment removal and restoration can minimise the damage. And in the long term, environmental gains should outweigh any losses. Algal blooms, which sometimes thrive in warm, nutrient-rich reservoirs, should disappear. Fish stocks will usually increase. A recent report from the Bureau of Reclamation, for example, showed that removing the Savage Rapids Dam on the Rogue River in Oregon could generate as much as $5 million a year from fishing.
Repair costs have always been a major factor in deciding the fate of dams and it is an argument that environmentalists are keen to exploit. The 1994 National Dams Inventory shows that 20 per cent of dams in the US have a “high” or “significant” potential for developing structural problems. According to Richard Knitter, who recently retired from Wisconsin’s Department of Natural Resources, in the coming decade around 10 per cent of the 3600 dams in Wisconsin alone will need repairs costing more than $100 000 each. Demolition of unsafe and crumbling dams is nearly always cheaper.
Costly to keep
If past experience is anything to go by, many American dams will be demolished rather than restored. Born’s studies, also in Wisconsin, show that cost was the major impetus for dam removal in 11 of the 14 cases that he examined. The Hayman Falls Dam on the Embarass River, for example, cost $272 000 to remove. Repairs would have cost $800 000. And the Woolen Mills Dam on the Milwaukee River would have costs $3.3 million to make safe, but was dismantled for just $500 000.
Environmentalists such as Rita Haberman of the Rivers Network in Oregon are quick to turn economic arguments to their own ends. She estimates that the Savage Rapids Dam will cost $11 million to remove, whereas repairing it could come to anything between $17 million and $24 million. And as most of the dams currently targeted by environmentalists are fairly small or do not produce power, energy shortage is not a problem. “This country has a surplus of electricity generating capacity, so in many cases alternatives are easily found,” says activist Patrick McCully. “In the future, however, one would hope to see a switch to real renewables such as solar and wind energy.” He points out that any shortfall in energy from removing dams could be made up through improved energy conservation and efficiency.
But many engineers have yet to be convinced that destroying dams is the most cost-effective solution. Ed Carter, president of Harza North-East in Utica, New York, a major dam-building company, says that complete removal may not be necessary: there are other measures. Some bigger dams that become safety hazards could be partially lowered to decrease water pressure, he believes. Carter, who is drawing up the American Society of Civil Engineers’ guidelines on dam destruction, reckons many large dams will probably never be removed because of the astronomical costs involved. They will simply be left standing.
Margaret Bowman, who heads the Hydropower Reform Coalition, disagrees. “Some of these high-cost estimates that the companies and the government produce add in the cost of shipping the entire sediment load to another location,” she says. “That’s not always necessary because the sediment can be released gradually into the river over a period of time.” And in his recently published book called Silenced Rivers, McCully argues that companies planning to build large dams must consider the eventual decommissioning costs. “The debate has only just begun in this country,” says McCully. “But when dam regulators or owners here or abroad face major safety issues in the future, dam removal may well be the cheapest option.”
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Watch this space
WHAT price are we prepared to pay to see river ecosystems restored? An ambitious scheme to rejuvenate the Elwha River on the isolated Olympic peninsula in Washington State will test environmental resolve in the US to the limit. Last November government officials completed a feasibility study and reported that the project would cost $113 million and take up to twenty years.
Where a tribe of Native Americans, the Elwha S’Klallam, once caught Chinook salmon weighing as much as 45 kilograms, there now stand two monstrous dams. The 31.5-metre Elwha Dam and the Glines Canyon Dam, standing at twice that height, were built early this century when a young Canadian settler called Thomas Aldwell decided to harness the river’s power to generate electricity. The Elwha peoples, who continue to live in a small reservation at the mouth of the river near Port Angeles, have always campaigned for fishing to be restored. Now their case is being taken up by environmental activists.
Whether their dream becomes reality largely comes down to economics. John Kasich, a Republican who chairs a key committee on financial matters in the House of Representatives, is in favour of the project, which enjoys cross-party support. But opponents, including Slade Gorton, a Republican Senator from Washington State, say that removal is far too expensive. He chairs a financial committee in the Senate which could delay funding.
Shawn Cantrell from Friends of the Earth in Seattle is “cautiously optimistic” that the money will be found. For a start, restoring fish stocks to the river was ordered through an Act of Congress in 1992. And a study completed in 1994 indicated that dam removal is the most effective way to do this. Cantrell points out that the government has already spent $8 million on feasibility studies and set aside another $8 million to buy the dam from its private owners. He is among those who argue that the environmental benefits of removing the dams outweigh the cost.