Project: Harbor Siphon Tunnel – New York
Customer: Tully / OHL JV
The successful drive was completed that connected Brooklyn to Staten Island. The deep tunnel, called a siphon, will convey drinking water under New York Harbor. It replaces two existing old water mains that will be removed allowing the harbor deepening initiative that is critical to accommodate larger cargo vessels.
A mixed face Earth Pressure Balance Tunnel Boring Machine (EPB TBM) was used for the first time in New York City and drove the 12 ft. (3.6 m) diameter tunnel in highly variable clay and sands under full hydrostatic conditions. The TBM was specially designed for the difficult undersea drive and to withstand potential hydrostatic pressures of up to 8 bar. Ballard Marine Construction provided full hyperbaric chamber and personnel support.
The project had an unscheduled interruption from hurricane Sandy. The historic storm surge associated with Sandy flooded the Staten Island shaft and the excavated tunnel with sea water, severely damaging the TBM. The assessments were completed, months of repairs and testing of all TBM related equipment was completed and the project went on to completion. Following the recommissioning of the system, hyperbaric interventions were carried out to fully change the cutters.