New York State has hired an engineering firm to find ways to reconstruct the deteriorating pedestrian bridges over the rapids above Niagara Falls, including ways to avoid blocking the flow of water over the American falls.
When first proposing the project four years ago, officials said it might be necessary to block the flow of water during work on the two 119-year-old stone spans — one from the mainland to Green Island and the other from Green Island to Goat Island.
Mark V. Mistretta, the regional director for the state Office of Parks, Recreation and Historic Preservation, said engineers from GPI, formerly Greenman-Pedersen Inc., are considering scenarios that might reduce the flow but wouldn't block it altogether.
Some ideas under consideration wouldn't block the flow at all.
The engineers' report is expected by the end of the year.
"This current phase of design and study and modelling will help inform the bridge design and construction techniques which may or may not involve shutting off the falls," Mistretta said.
The ideas could include temporary partial blockages of the Niagara River between Goat Island and the mainland that would be moved as the project proceeds.
"You could do isolated cofferdams, right around the area you're working," Mistretta said. "Or you could do a large one, like what was done back in '69."
In 1969, the American falls were blocked completely to study erosion and rock buildup at the base of the Falls.
The rising Great Lakes water levels of the last few years, with more water from Lake Erie coming down the Niagara River and over the falls, are a new factor influencing planning, Mistretta said.
The increased flows might make it harder to divert all the water over the Horseshoe Falls on the Canadian side, as any shutoff plan would require. The Horseshoe Falls already takes about 85% of the water coming down the river.
"They're exploring the water modeling of the river itself to help inform the cofferdams, whether or not we use them or where we use them, just to help inform our decisions on what approach we're going to take. As we all know, the lake levels are higher and we need to account for them," Mistretta said.
All this remains in the planning stage, as no funding has yet been allocated to carry out the reconstruction of the bridge.
Mistretta said the current cost estimate is about $35 million.
Temporary spans with their own suspension have been placed over the old stone bridges.