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Action Examples: City Tunnel Number 3, New York City, New York


Introduction
New York City’s City Tunnel #3 project is a 55-year long project involving the construction of 64 miles of 24 foot diameter tunnel. Much of the tunnel is being built 800 feet below ground. When it is finished, the project will help connect area reservoirs to the City.

In August 1998, Stage 1 of the project was completed at a cost of approximately $1 billion; this thirteen mile segment carries water to Queens from the Hillview Reservoir in Yonkers. An outflow pipe along this segment was built higher than originally planned to accommodate possible sea-level rise.


Analysis:
A New York City water supply official felt that sea-level rise projected to occur in 15 to 25 years would trigger responses in planning and design. But if changes would not happen for 50 years or so, he felt the projections would affect thinking but not action.  He judged that economic sensitivity analysis would show the desirability of early adjustment to climatic change.  He gave an example of an outlet being raised explicitly to accommodate possible sea-level rise on a drainage structure for the city's third water tunnel. The redesign was not total, however; the designers raised the outlet to the extent possible within existing design constraints, so that the impact on cost was insignificant. 


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*All website references were accessed in April 2005.

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