New York City Department of Environmental Protection

Delaware Aqueduct System: Water Leak Detection and Repair Program

The Delaware Aqueduct System provides approximately 55 percent of New York Cityís water supply. The New York City Department of Environmental Protection, which operates and maintains the water supply system, has known since 1988 that part of the Delaware Aqueduct System (the Rondout-West Branch or RWB Tunnel) has been leaking. We examined the actions taken by the Department in monitoring and repairing these leaks.

We found the Department has not taken all the actions recommended by its engineering consultants in monitoring the leaks and has not initiated repair of the leaks. In fact, the Department has yet to develop a formal work plan for the repairs. According to Department officials, the repairs cannot be initiated until the tunnel is shut down, and the tunnel cannot be shut down until alternative sources of water can be provided to New York City and the other dependent downstate communities while the repairs are being made. The Department is addressing this issue as part of a larger, comprehensive plan for the entire water supply and distribution system, but Department officials estimate that it will take a decade or more to finalize the plan and build the individual projects recommended by the plan.

We believe that repairing the known leaks in the RWB Tunnel at the earliest time that the tunnel can be shut down would not be inconsistent with the Departmentís comprehensive plan. We therefore recommend the Department fast track the repair of the RWB Tunnel. In addition, if conditions in the RWB Tunnel deteriorate further, the water supply for millions of people could be disrupted. However, we found the Department does not have an adequate emergency response plan in place to address the sudden failure of the tunnel. We recommend such a plan be developed.

For a complete copy of Report 2005-N-7 click here.