The Bergen Point Wastewater Treatment Plant (WWTP), owned and operated by Suffolk County Department of Public Works, discharges treated effluent into the Atlantic Ocean through an outfall that passes beneath the Great South Bay and underneath Jones Beach. The 14,200-foot-long segment of the outfall that extends from the WWTP to the Jones Beach Island and passes underneath Great South Bay, has been determined to be in a failing condition and replacement is necessary.
OHLA USA, as part of a joint venture, is constructing a 10-foot diameter tunnel through a mixture of soft soil materials under the Great South Bay. The new 2.6-mile tunnel will address the concerns of potential failure of the current pipe and will have a longer lifespan. No carrier pipes will be installed within the tunnel; the lined tunnel itself will serve as the replacement outfall.
The TBM entry and exit shafts are being constructed using ground freezing techniques and extend to a depth of 80 to 100 feet below ground. The tunnel is being excavated using a slurry TBM and concurrently lined with 48-inch-wide precast concrete segment rings. The shaft construction is divided into major work phases including site preparation, excavation of the launch shaft and installation of the new slurry TBM.
The scope of work also calls for replacement of the pipe and valves at the existing Final Effluent Pump Station, installation of the new site piping, gates, valve chamber, meter chamber, chamber 3B, and set up of staging and mucking areas. Piping work on the Barrier Island will extend from the receiving shaft to the new connection at the existing outfall.
Entry and exit shafts being constructed used ground freezing techniques
Tunnel excavation using a slurry TBM