Tunnel repair for aging New York aqueduct
Sep 2011
Paula Wallis, TunnelTalk
- A 3 mile bypass tunnel is part of a $2.1 billion upgrade of the Delaware Aqueduct, a vital component of New York City's drinking water supply system.
- The Rondout-West Branch Tunnel section of the 85 mile Delaware Aqueduct, claimed as the longest continuous tunnel in the world, is leaking between 15 and 35 million gallons of water each day. The aqueduct was completed in 1944 and supplies about half of New York's drinking water (500 million gallons per day) from four upstate reservoirs. More than eight million people in New York City and one million people in neighboring counties have their water supplied via the aqueduct.
Fig 1 and 2. Proposed alignment (left) and section of the bypass project
- To address the leaking issues, the New York City Department of Environmental Protection (DEP) is proposing a bypass. The tunnel and internal repairs will cost about $1.2 billion, with an additional $900 million going to projects to supplement the City's water supply during construction.
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Table 1. Project cost estimate and schedule
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- Inspections have indicated that cracking and leakage is occurring in sections where the aqueduct passes through limestone, a rock more susceptible to weathering than the sandstone, shale, gneiss and granite that hosts the majority of the vital water supply line. The tunnel's concrete lining has cracked and is leaking along a 500ft (152m) section in the Wawaring area and along a 5,000ft (1,524m) stretch in Rosenton.
- Groundbreaking on contract to build the bypass tunnel is planned by the DEP in 2013, with connection to the Delaware Aqueduct anticipated in 2019. Between 1,000 and 1,500 jobs are expected to be created by the major repair project.
Original construction of the Rondout West Branch Tunnel of the Delaware Aqueduct in 1942
Photo by NYC DEP Archive
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