Tappan Zee Bridge milestone approaches in Rockland

Another major construction milestone is fast approaching on the Tappan Zee Bridge project.

Work is set to begin next week in South Nyack to build a hulking structure known as an abutment, which is where the new crossing meets land.

"To get to this point is very big," Tappan Zee Constructors construction services manager Ro DiNardo told The Journal News.

Over the coming weeks and months, there will be a whirlwind of activity on the $3.9 billion project in Rockland alone.

As many as 50 trucks a day will use special access ramps to get off and on the Thruway in South Nyack.

Thruway drivers also will begin to notice, near Interchange 10, construction of an overhead steel gantry that will hold equipment to collect bridge tolls all-electronically. The temporary system is expected to go into service in early 2016 after months of testing and be used until construction is completed in 2018.

Near the shore, crews are building the piers that will support the bridge's two spans. Work has already begun in the Hudson River, and construction of the one pier that will be built on land in South Nyack kicks off in the spring.

Starting in summer, the structural steel that will hold up the new roadway will first begin to rise on the Rockland side.

Bridge abutment

The abutment, which provides a transition between water and land, will be built in layers of steel and concrete, reaching 20 feet – the same height as the existing bridge as it passes over River Road. DiNardo said they also will start work on an abutment in Tarrytown within the month.

"Really it's just a big piece of concrete," DiNardo said. "It has a seat in it so the steel will come and actually sit in the seat and the top will be paved over. It'll be part of the road."

About 10 construction workers will build the Rockland abutment, which will eventually exclusively handle traffic coming from Westchester into Rockland. Near the end of 2016, all traffic will be shifted from the current Tappan Zee to the first new span. That will allow the Rockland landing of the current state Thruway Authority-owned bridge to be torn down so a second abutment can be built for the span handling Westchester-bound traffic.

The work, which covers the area of a basketball court and is buffered by sheet piles on one side, should be completed by April.

Between concrete trucks for the abutment work and normal equipment deliveries for the project, there could be anywhere from 5 to 50 trucks a day using redesigned access ramps to get off and on the Thruway from River Road in South Nyack. The project site is only yards away.

"Everything we'll do here, we'll be able to do with River Road being open and the Thruway staying open," he said.

Delivery of concrete by truck for the bridge's foundations at the Rockland shore had been planned from the start. Additional concrete trucks will be coming through the area to bring concrete to the river construction zone after both of the project's floating concrete plants were taken out of service following a malfunction last month.

TZC workers have had to do some preliminary work to solidify the ground where the abutment will be built because, DiNardo said, the soil was "way too soft." Instead of steel piles, they installed a series of subterranean piers made up of compacted crushed stone 30 feet deep to provide support.

"It helps the foundation stay where it has to stay," DiNardo said.

He described it as a "unique technique" that avoided the need for additional pile driving on land. Earlier pile driving led to noise complaints last summer.

Piers

A few hundred yards away from where DiNardo spoke, a dozen men were working inside what looked like a huge bathtub in the Hudson measuring 60 feet long by 25 feet wide.

The construction workers are putting in steel rods known as rebar for the foundation for what will become the pier closest to the Rockland shore. The tub will eventually be filled with concrete to form the pile cap and then columns will be built on top of that to support the roadway.

"This is just beginning," DiNardo said of the pier work. "There's a lot more to do here."

There are 43 piers in all on the project, with similar efforts taking place at different locations along the 3-mile-wide river.

The Left Coast Lifter, one largest floating crane in North America, is expected to be called into service next month.

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