Gilboa Dam release mechanism may cut flood risk

PHOTOGRAPHER: Patrick Dodson

Gilboa Dam is seen on Thursday, October 30, 2014.

Work is scheduled to start this month on a five-year, $142 million project to build a release mechanism in the Schoharie Reservoir to better regulate water levels and protect downstream communities from the kind of flooding seen during Tropical Storm Irene in 2011.

When completed in 2020, the mechanism will allow the regular release of water into the Schoharie Creek for the first time since 1927, a move that state and county officials have pushed for since Irene.

“Building this release tunnel is part of a comprehensive program to improve and strengthen our critical infrastructure at Schoharie Reservoir,” New York City Department of Environmental Protection Commissioner Emily Lloyd stated in announcing the start of the project Thursday. “The release works will allow DEP to draw down the reservoir for dam maintenance and in case of emergency, while also mitigating flood risk for our downstream neighbors.”

The project is part of a $400 million program that included a $138 million rehabilitation of the Gilboa Dam that wrapped up in 2014, as well as upgrades to the Shandaken Tunnel Intake Chamber, which carries water toward New York City, and other restoration work.

According to Lloyd, the Schoharie Reservoir provides 15 percent of New York City’s drinking water, and “these projects are essential to keeping the city’s supply reliable and secure for generations to come.”

When the project was announced in March, Blenheim Town Supervisor Shawn Smith said this kind of mechanism and water-level regulation could have prevented a lot of the damage caused by Irene.

“If they had done this a few years ago, the water might not have crossed over Route 30 and it could have saved half the town,” he said then. “Drawing the reservoir down at certain times is a good idea and it will work for the city, as well.”

The project includes the construction of an intake structure at the bottom of the reservoir, more than 2,000 feet of subsurface tunnels, and a valve chamber along the Schoharie Creek, which will give DEP the ability to release water into the creek for dam maintenance, to respond to emergencies, to reduce the risk of floods downstream, and to enhance downstream habitats for fish and wildlife, according to DEP.

The reservoir was created by the construction of the Gilboa Dam on Schoharie Creek 88 years ago, and stretches across the towns of Conesville and Gilboa in Schoharie County as well as parts of Delaware and Greene counties, holding up to 19.6 billion gallons of water.

For now, temporary siphons at the Gilboa Dam are being used to occasionally release water from the dam, especially during the spring thaw, when room has to be made for melting snow.

The release works may also be used down the road for a conservation release program to provide a baseline flow in Schoharie Creek to support habitat for fish and other wildlife, as explored in a study DEP submitted to the state Department of Environmental Conservation in 2014.

While construction is set to begin this month on the release works, both the conservation release program and flood mitigation release program are still awaiting DEC review, according to DEP.