March 2, 2021

Posillico-logo.pngPosillico Reaches Major Milestone On Bergen Point Project

There’s “breaking ground” and then there’s “groundbreaking”. LICA member Posillico (as part of a JV with OHL and SELI) earned the right to use both adjectives as a result of a single milestone they recently marked at the massive Bergen Point project. Read below for details and see related photos that follow.

The Bergen Point Wastewater Treatment Plant Outfall Replacement Project achieved an important milestone in recent weeks. After over 1 year of tunneling at depths of 100 feet below grade, slurry Tunnel Boring Machine (TBM) broke through the soil after a 2.6-mile journey on January 25th, 2021. The 10-foot diameter tunnel runs under the Great South Bay connecting Suffolk County’s Bergen Point Wastewater Treatment Plant to the Barrier Island.  The new tunnel will replace an antiquated portion of the existing outfall pipe which discharges treated effluent 3 miles offshore into the Atlantic Ocean from the Bergen Point Wastewater Treatment Plant.  This is the largest construction project in Suffolk County in several decades, built by a joint venture between OHL, Posillico and SELI for the Suffolk County Department of Public Works. 

Two shafts were constructed as launch and receiving points for the TBM. A ground freezing technique was implemented to excavate the shafts to 80 and 100-feet deep.  Freeze walls extending 10-15-feet beyond the diameter of each shaft acted as support of excavation. Both shafts then received 18-36” of reinforced shotcrete to provide support once the ground freeze was turned off. The TBM allowed for precast concrete segments to be installed during tunneling operations through soft earth to fully line the newly excavated tunnel, the first of its kind on Long Island.

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