New gate system completed in overhaul of Gilboa Dam
GILBOA A gate system built as part of the massive overhaul of the Gilboa Dam is now complete, providing a means to release water downstream and relieve pressure on the concrete-and-stone dam that holds more than 17 billion gallons of water hovering over communities in the Schoharie and Mohawk valleys.
The New York City Department of Environmental Protection, which manages the dam and the Schoharie Reservoir it holds back, announced Monday the completion of an $8 million movable barrier gate system built along the 220-foot notch cut into the top of the dam in 2006.
The notch was among several emergency measures taken after engineers determined in 2005 the dam didn’t meet current standards.
It reduced the height water could reach, relieving pressure on the dam and allowed for the DEP to install 80 anchors through the dam, mounted to the bedrock below.
Now, that notch is occupied by 11 gate panels made of stainless steel. They are each 20 feet long and weigh more than 5,400 pounds, according to the DEP.
The panels are fitted with air-powered controls enabling the DEP to raise and lower them.
The gates, when lowered, will release water from a full reservoir, providing additional capacity that can be gained before a heavy rain is forecast.
The gates when raised also bring the reservoir back to its full capacity during drier times, making more drinking water available, DEP spokesman Ted Timbers said.
“It serves a dual purpose,” he said.
The gates are one of a couple elements of the $400 million reconstruction project expected to give managers more capabilities when it comes to flooding.
The DEP is also planning to build a low-level outlet consisting of a 9-foot-diameter tunnel that will be able to release water from the reservoir into the Schoharie Creek downstream.
That outlet system is planned for completion in 2018.
A low-level outlet built during the dam’s construction between 1919 and 1927 is filled with silt and no longer functions.
Dam Concerned Citizens, a citizen group formed after the dam’s integrity was called into question, has been monitoring progress in the construction.
DCC member Howard Bartholomew said having a controlled manner by which water can be released in anticipation of high water is a necessity.
“If these release works are used pre-emptively, you can get a degree of mitigation because you have water restrained in the system while it’s passing out in a controlled manner, hopefully,” Bartholomew said.
“It’s a definite step in the right direction.”
A low-level outlet and a gate system, Bartholomew said, would have helped minimize damage from flooding that took place prior to Tropical Storm Irene.
It wouldn’t do much in the face of the massive volume of floodwater Irene sent through the valley, though.
“No one expects a miracle,” Bartholomew said.
Dam Concerned Citizens is calling on government agencies, including New York City, the state’s Department of Environmental Conservation and others, to develop an organized plan that can be employed in time for water releases before major storms.