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Dewatering the American Falls at Niagara

Mon November 07, 2011 - Northeast Edition
Mary Reed

During the course of 1969 the first moon landing took place, the Woodstock Festival was held and the American Falls at Niagara, N.Y., ceased to flow.

While the American Falls is not quite as spectacular as the neighboring Horseshoe or Canadian Falls, nevertheless between 8,000 and 15,000 cub. ft. of water flow over its crestline every second, hitting its rockstrewn base with the force of 280 tons.

It would seem impossible anything could stop it flowing, yet less than 50 years ago the U.S. Army Corps of Engineers accomplished just that feat.

Their task came about because the American Falls flows across hard rock lying over softer shale. Water action causes the shale to be gradually worn away and widens fractures in the upper layer, a combination that ultimately leads to the collapse of huge chunks of rock (talus) due to the loss of support.

Alarm bells had been sounded by claims in a 1965 newspaper editorial that unless something was done about the talus piled up at its base, the American Falls would eventually be destroyed. The same year Congress authorized the International Joint Commission to make recommendations about measures to be taken to deal with the problem. The commission, which oversees the interests of the United States and Canada in matters relating to the river boundary between the two countries, formed the American Falls International Board to examine the situation, and two years later the board announced its finding that the waterfall should be dewatered so the condition of its face, base and the riverbed above it could be scrutinized and any necessary remedial steps taken by the U.S. Corps of Engineers.

The project was certainly necessary, given the Buffalo District of the Corps stated that a 1931 rock fall involving approximately 76,000 tons, another in 1954 of about 185,000 tons, and similar collapses had contributed to the huge and growing pile of talus at the foot of the American Falls. By the 1960s talus had reached a point almost half the way up the waterfall’s face in some places.

Once it was decided the dewatering project should proceed, the Corps announced its intent to investigate the falls’ geologic condition while it was possible to access the falls and its base. Tests to be carried out included laboratory evaluation of rock samples, surveying and probing the falls and its riverbed, determining the condition of the shale layer, and using the resulting information to decide what measures could be taken to preserve the waterfall.

The dewatering of the falls was an international project, involving the Buffalo District Corps of Engineers, Niagara Frontier State Park Commission of New York, and the NY Power Authority in cooperation with the Canadian Department of Energy, Mines & Resources, the Hydro-Electric Power Commission of Ontario, Niagara Parks Commission of Ontario and Canada’s Department of Public Works.

The Albert Elia Construction Company of Niagara Falls, N.Y., was awarded the $445,412 contract for construction and removal of a 600 ft. earth cofferdam comprised of almost 28,000 tons of earth and rock fill and stretching from the mainland to Goat Island, located between the American Falls and the Horseshoe Falls.

Rick Berketa of NiagaraFrontier.Com, who has made an extensive study of the project, noted the company began work on the cofferdam on June 9, 1969, after a lifeline was strung from Goat Island to the mainland. Working in 11 hour shifts, just before noon three days later the thirty employees involved completed the task of damming the Niagara River, diverting its water from the American Falls to the Horseshoe Falls.

Thus, on June 12, 1969, the American Falls became a mere trickle. Over the course of the following months thousands of visitors flocked to the American Falls to witness the historic conditions. Such was the interest in the now virtually dry waterfall that almost 90,000 arrived over the course of two July days alone and it was reported the number of visitors to the Canadian side dropped off noticeably.

Geological work carried out during the dewatered period included mapping the face of the falls, more than 40 test borings, and installation of piezometers to measure water pressure on rock joints and extensometers to provide data on any rock movements that occurred.

Loose shale was removed from the face of the falls by workers suspended in cages dangling from the booms of two cranes. Approximately 800 ft. of 6 in. diameter water sprinklers, drawing water from the cofferdam, were installed to keep the waterfall face moist as a precaution against further deterioration and possible falls.

By mid July Corps geologists were carrying out test borings, with a view among other goals of determining how to prevent erosion. Albert Elia Construction Company employees were pressure-cleaning algae from river bed rocks with 100 lb. pressure air-water jets, augmented by sand-blasting as conditions warranted, working from the crestline for about 400 ft. up the riverbed.

In August visitors were allowed to go out about 20 ft. on the dry river bed in a fenced off section, and during the same month a platform with a protective roof was erected to protect those working on the talus, since pieces of shale occasionally fell from the face of the falls.

The work and geological tests continued until late November, when it was announced that the project was over, the cofferdam would be removed, and the American Falls would flow again.

More than 2,000 spectators gathered for the event.

At 10:05 a.m. on Nov. 25, 1969, an eleven year old boy named David sounded a horn as a signal for the drag-line operator to begin removing earth from the cofferdam. The first breach was made about 30 ft. from Goat Island and by the middle of the afternoon of the following day the American Falls were back to full strength.

Will the Falls Be Dewatered Again?

The American Falls: Yesterday Today Tomorrow, a 1973 booklet published by the International Joint Committee’s American Falls International Board, laid out suggestions on ways to enhance the beauty of the American Falls and asked for public input via a ballot in the booklet. More than 200,000 were distributed in Niagara Falls on both sides of the river. The board’s suggestions were:

• To remove all or part of the approximately 358,000 tons (280,000 cu. yds.) of rocks at the base of the falls. The estimated cost for this project was between $1 million and $10 million, the final cost depending on how much of the talus was removed.

• To increase the flow of water over the American Falls by excavating rock in the channel carrying water to the falls and equipping the channel with control gates. Estimated cost: $6 million.

• To restore the Maid of the Mist Pool below Niagara Falls to its original depth, thus returning it to a level that previously covered about a third of the rock pile. The level of the pool had fallen 20 ft. after a hydroelectric plant was built higher up the Niagara River. For this project the estimated cost was $8.7 million.

Of particular note regarding the first and second suggestions is that they would involve dewatering the American Falls for one or two seasons for the former and one season for the latter.

Five thousand votes were cast and thousands of comments sent to the board. The result was that the majority voted to leave the American Falls as they were.

Two years later the International Joint Commission issued a report to the effect that removal of the talus was not desirable at that time, although the minor risk of rock movement had to be accepted by the public. It also recommended a joint environmental study between the two countries, noting that there was some unstability on the flanks of both the American and Horseshoe Falls that should be corrected.

In 1983, the unstable rock at Terrapin Point in the northwestern side of Goat Island was removed by blasting and some remedial work was done on the island’s side of the Horseshoe Falls to stabilize the remainder. CEG

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