The New York City Department of Environmental Protection announced Friday that contractors have finished installing the first of two siphons at the Gilboa Dam. The siphon was successfully put into operation this morning. The DEP has also stopped the special diversions through the Shandaken Tunnel and the operational releases from Ashokan Reservoir that allowed for the installation of the siphon.
The siphon is a metal pipe – 6 feet in diameter at its widest point – that moves water out of the reservoir, over the dam and into the creek below the dam. Contractors have also begun the installation of a second siphon at the Gilboa Dam. The completion date of the second siphon will depend largely on the amount of rainfall the area sees in coming weeks.
Each siphon is capable of releasing 250 million gallons of water a day from the Schoharie Reservoir into Schoharie Creek. The DEP will use the initial siphon to help prevent the reservoir from spilling, thereby allowing workers to install the second siphon.
The siphons are critical to the rehabilitation of Gilboa Dam. The Dam is undergoing a full, $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 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 the 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.
The DEP manages New York City’s water supply, providing more than 1 billion gallons of water each day to more than 9 million residents, including 8 million in New York City, as well as residents of Ulster, Orange, Putnam and Westchester counties. The water comes from the Catskill, Delaware, and Croton watersheds, which are as far as 125 miles from the city and include 19 reservoirs, three controlled lakes and numerous tunnels and aqueducts.