Gilboa Dam: One siphon down, one to go

Above: Video of the Gilboa Dam's newly installed siphon in operation. Video by the New York City Department of Environmental Protection.

The New York City Department of Environmental Protection announced on Wednesday that they had just finished installing one of two massive siphons at the Gilboa Dam, allowing the agency to lower the level of the Schoharie Reservoir by releasing water directly into the Schoharie Creek. The siphons are an important flood control mechanism for communities downstream of the dam, and local advocates have been clamoring for them to be finished since four smaller siphons were removed from the dam this summer.

Until the first siphon went into operation Wednesday morning, the only way to move water out of the Schoharie was to release it into the Shandaken Tunnel leading to the Ashokan Reservoir, an action that often required water to be released from the Ashokan as well. The DEP's turbid water releases from the Ashokan into the Lower Esopus have been fiercely opposed by Ulster County residents who live near the Lower Esopus, and have been the focus of a very public battle between the agency and Ulster County executive Mike Hein.

To finish the work on the siphons, the DEP had been making extra water releases from both the Schoharie and Ashokan reservoirs. With the new siphon installed, the DEP has put a halt to these releases, and is now relying on the one functional siphon to keep the water level low enough to finish work on the other siphon.

A press release from the agency states that the weather in the coming weeks will determine when the second siphon will be finished. The siphons are an important part of ongoing work at the Gilboa Dam, the release states:

The siphons are critical to the rehabilitation of Gilboa Dam. The Dam is currently undergoing a full-scale $400 million rehabilitation that will include reinforcing it with 234 million pounds of concrete, reconstructing the spillway, and installing a new release tunnel around the Dam from the Schoharie Reservoir to the Schoharie Creek. Reconstruction of the Gilboa Dam is expected to be completed in 2014, while the new release tunnel is expected to be finished in 2019. The two siphons will be removed once the release tunnel is operational.

The siphons will remove water from the reservoir and allow contractors to access portions of the Dam that might otherwise be obstructed by water pouring over the spillway. The siphons will also help DEP meet its commitment of removing water from the reservoir equal to 50 percent of the snow pack during winter months, while also providing additional flood protection.