Incredible Floating Machines: Concrete technology deployed at TZ work site

STORY AND PHOTOS BY JANIE ROSMAN

The first of two mobile, river-based floating concrete batch plants arrived at the New TZ Bridge project site last month for the new bridge’s in-river work, and is now in operation by Tappan Zee Constructors, LLC (TZC).

It can cast about 125 cubic yards of concrete per hour; a second such plant will be added later. The first pour (July 16) was at bridge pier 39 for a temporary working surface within its cofferdam.

“We have approximately 300,000 cubic yards of concrete to place on this job,” Tappan Zee Constructors, LLC (TZC) President Darrell Waters told reporters during a tour of the project site on last Thursday.

Unlike the main span of the current bridge that was reconstructed last year, the center span of the new bridge will be built first, and materials are being produced on the river — meaning 30,000 fewer trucks on the road during the project. While “some trucks will still be needed to support land-based activity, this is still a major benefit to the community,” Community Outreach Manager Carla Julian said.

Officials said 39 percent of the 1,000-plus piles that will support the twin-span bridge have been installed. We’re going to “hopefully erect our first piece of steel by the end of this year,” Waters said. “We feel pretty good about where we are, still an aggressive schedule.”

Hollow inside, the piles fill with river muck as they’re installed in two sections, vibrated and field welded. Once in place, a giant clamshell bucket excavates the muck, and the each pile is reinforced with concrete and rebar (reinforced steel). Installation, reinforcement and capping are ongoing through spring 2015.

Variations in the river bed require pile lengths from 100 to 330 feet long, and from 3 to 6 feet in diameter; capping them ensures a more stable foundation. The main tower concrete pile cap forms are onsite and being prepped prior to installing. Approach span pier caps, made offsite, will be shipped to the construction site.

Reporters on the tour passed one of the 14-foot thick main span platforms that will cover the main span’s steel pilings.

“It’s 360-plus feet long (with) a concrete precast bottom in it that sits over the piles,” Waters explained of the massive pile cap that will be filled with 11,000 cubic yards of concrete. “Once we put the form work in, we’re going to sink that eight feet into the water.”

Noteworthy: The project reached one million man hours without a reportable injury on July 15.

Safety measures and restrictions for recreational boaters include GPS trackers on construction equipment, a geo (electronic) fence around the work zone, an expanded RNA and new safety zone, and temporary navigational lights. Details can be found on the New NY Bridge website.

As in-river construction spares the environment, travelers will be saved a fare increase: Thruway Authority Executive Director Thomas Madison said there are no plans to make any adjustments to tolls on either the Tappan Zee Bridge or the 570-mile system in 2014.

The Thruway Board was to have considered the $256 million Environmental Facilities Corporation (EFC) loan at its August 6 meeting.

Madison said last week he’s confident the board will accept and approve the loan, which was discussed publicly. “It’s important to remember all environmental aspects of the project were completed before we (Thruway Authority) considered pursuing the loan.

Reiterated NYSTA Director of Media Relations and Communications Dan Weiller, “The Thruway Authority had to make sure each item qualified before it applied for the loan. Many of the folks who went through the process for environmental funding are the same groups that are objecting.”

The Thruway Authority will not access the second $256 million installment, which has to be approved by the PACB, until 2016.