Major Prep Steps Begin for Delaware Aqueduct Shutdown

Construction workers are installing three large siphons that will increase our ability to release water from Rondout Reservoir during the shutdown, and a second project will modify an old hydroelectric dam downstream of the reservoir, on Rondout Creek, to ensure its long-term safety and stability.

This large crane at Rondout Effluent Chamber is helping workers install new infrastructure that will anchor the siphons in place. The work is surrounded by turbidity curtains to protect water quality at the intake.

With the planned Delaware Aqueduct shutdown scheduled in 2022, we’ve begun work on two significant construction projects that will prepare Rondout Reservoir and the area downstream for additional releases of water.

Project Background

Both projects need to be substantially complete before the Delaware Aqueduct is shut down next October to finish the largest repair project in the 179-year history of New York City’s water supply system. The aqueduct will be shut down for 5–8 months while construction crews connect the new bypass tunnel under the Hudson River, permanently routing water around the largest of two leaks in the aqueduct. That leak, in Newburgh, allows 18–20 million gallons to escape the aqueduct each day. A second work crew will work during the shutdown to seal a smaller set of leaks in Wawarsing (Ulster County).

The Three Siphons

The entire scheme for managing water at Rondout Reservoir will change during the shutdown next year. For one, we will not divert water into Rondout from Cannonsville, Pepacton and Neversink. Only water from its 95-square-mile watershed will flow into the reservoir. And with the Delaware Aqueduct out of service, we need a temporary way to remove water from the reservoir and reduce the likelihood that it would pass water through its spillway. That’s why we're installing three siphons at Rondout Reservoir to help manage water levels during the shutdown. The project will be complete in May or June, 2022.

Small Dam Modification Along Rondout Creek

The former bed of Honk Lake will be reshaped as a restored stream corridor for the Rondout Creek.

To prepare the downstream area for additional water, we're also modifying a small dam that once formed Honk Lake and generated hydroelectricity for the greater Ellenville area. The old penstocks from the hydroelectric dam will be removed and the height of the dam will be reduced by 12 feet. A notch will also be cut in the middle of the dam to allow regular streamflow to pass over it like a small waterfall. Stream experts will reshape the former lakebed to create a stream that is lined by cobbles and surrounded by a new forest of native species. And material excavated from the former lakebed will be used to fill a nearby depression in the land where utilities had once quarried stone for the construction of roads.

The most critical components of the work, including work to modify and stabilize the dam, will be completed before the Delaware Aqueduct is shut down and additional water is released from Rondout Reservoir.