New York plans Delaware Aqueduct bypass tunnel3 December 2010
A 3-mile (4.8-km) bypass tunnel will be constructed to repair the leaking Delaware Aqueduct, according to a design plan released by New York City’s Department of Environmental Protection (DEP) on 19 November.
Under the plan, the USD-1.2bn new bypass tunnel will be built around a portion of the aqueduct experiencing the most significant leakages and parts of the aqueduct’s concrete liner will be repaired. The alignment will run east from Newburgh, under the Hudson River, to Wappinger.
The 85-mile (136.8km) aqueduct varies in diameter from 13.5 to 19.5ft (4.1 to 5.9m) and runs as deep as 1,500ft (457m). It was constructed by drill and blast in 1944 and in most areas it is lined only with unreinforced concrete, though a steel reinforcement liner had been added later in areas of weaker rock.
DEP has called for construction on four access shafts ranging from 700 to 900ft (213 to 274m) deep with 15 to 20ft (4.6 to 6m) diameters to begin in 2013. Tunnelling, to be performed by a 22ft (6.7m) diameter TBM, is expected to start in 2015.
Equipment purchasing and contract document preparation, including for the bypass tunnel, are underway now.