Explosives to Be Used in the Demolition of a Tappan Zee Bridge Span

It will sound like fireworks and take less than 30 seconds for a 6,500-ton portion of the old Tappan Zee Bridge to reach the Hudson River.

Once the smoke clears, the once-three-mile bridge that carried 140,000 cars over the Hudson River each day at its peak and connected Westchester and Rockland Counties will be one step closer to being a memory.

The 672-foot east span of the former bridge, which is closest to the Westchester side, will be demolished using explosives at 9:30 a.m. on Jan. 12.

The original plan was to dismantle the whole bridge piece by piece rather than to use explosives, which officials worried might adversely affect Hudson River fish and wildlife.

But in September, workers dismantling the east span heard a loud popping sound and soon discovered that the structure was unstable. Taking that part of the bridge apart piece by piece could lead to collapse, Tappan Zee Constructors, the company responsible for the demolition, determined.

“Through extensive engineering analysis, it has been determined that this is the safest method to proceed with lowering the span given its current state,” the company said in a statement.

After the demolition, only a portion of the west span, nearer Rockland County, will remain; it will continue to be dismantled piece by piece, according to Tappan Zee Constructors.

The instability of the east span was discovered a day after Gov. Andrew M. Cuomo led a ceremony to open the second span of the Mario M. Cuomo Bridge, the $4 billion structure named after his father. That bridge was built to replace the Tappan Zee, which opened in 1955.

State Senator David Carlucci, a Democrat who represents Rockland County and parts of Westchester, said on Saturday that he was disappointed at the change of plans because engineers have “known since September that the structure was not sound.”

Mr. Carlucci said he was concerned about the potential impact on the environment but had accepted the explosion as the “safest scenario” possible. “I’ve got to go with what the experts are telling me,” he said.

The United States Coast Guard will set up a 2,500-foot safety zone around the demolition site. Explosives will take out the east span’s legs only, causing the span to fall into the river. Barges will pull the remnants away from the river’s navigation channel.

A steel netting placed on the river bed will help trap the demolished pieces for a marine salvage company to recover over the next few weeks. Portions of the span will be visible above the water until they’re removed. All of the steel, concrete and asphalt from the bridge will be removed from the river, according to Tappan Zee Constructors.

The group said that now was an ideal time to perform the demolition because there are not as many Atlantic sturgeon, the Hudson River’s largest fish, this time of year. Controlled Demolition Inc. of Maryland, which in 2017 demolished the old Kosciuszko Bridge that connected Brooklyn and Queens, will perform this demolition.

Travel on the New York State Thruway between exits 9 and 11 will be halted at 9 a.m. in both directions for 45 minutes on Jan. 12. Metro-North Railroad service is not expected to be affected. The Mario M. Cuomo Bridge will be examined before it is reopened, officials said.

In case of inclement weather, the demolition will take place on Jan. 13.

Follow Jeffery C. Mays on Twitter: @JeffCMays

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