New Bridge Takes Shape; Pile Cleansing Starts

In addition to wearing flotation devices and hard hats, we donned protective glasses before Tappan Zee Constructors, LLC (TZC) allowed us to board its boat. TZC also checked to make sure we were wearing sturdy shoes. Safety first.

Getting ready to board TZC's boat/© Janie Rosman 2014

Getting ready to board TZC’s boat/© Janie Rosman 2014

Twenty percent of the steel piles are in place, and are now being cleaned.

“Pile installation of the two main towers of the bridge has been completed, all piles are in the group in place,” NYS Thruway Authority Construction Compliance Engineer Tom McGuinness told us.

The new bridge will have 43 approach span piers — each formed by groups of piles — compared to 196 on the current bridge. Additionally, the first five approach span piers near the Westchester shoreline have piling completed.

Pile cleansing bucket/© Janie Rosman 2014

Pile cleansing bucket/© Janie Rosman 2014

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).

Variations in the river bed require pile lengths from 100 to 330 feet long, and from 3 to 6 feet in diameter. TZC is prepping and installing piles at four locations simultaneously.

Next comes capping to ensure a more stable foundation. The main tower concrete pile cap forms are on site and being prepped prior to installing. Approach span pier caps, made off site, will be shipped to the construction site.

Rockland trestle is 80% complete/© Janie Rosman 2014

Rockland trestle is 80% complete/© Janie Rosman 2014

Two 1,000-foot work trestles on each shoreline support equipment and prevent excessive shoreline dredging that could harm the river and shorelines. Part of the Rockland trestle will be dismantled, and part will remain in place as the Thruway Authority’s permanent maintenance dock.

Installation, reinforcement and capping continue through next year (spring 2015), McGuinness said.

Update: A friend who read this post said the term is pile excavation.

I’d like to know what you think.

Copyright © Janie Rosman and Kaleidoscope Eyes 2014

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