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May 9, 2017
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DEP Starts Next Phase of Construction for Release Works at Schoharie Reservoir

Micro-tunneling machine at Schoharie Reservoir

High-resolution photos from the event are available on DEP’s Flickr page

The New York City Department of Environmental Protection joined local elected leaders and public safety officials on Tuesday to mark the next phase of construction for release works at Schoharie Reservoir. City, state and local representatives visited the worksite in Gilboa where a micro-tunneling machine will be lowered this week 182 feet down a shaft to begin work on more than 2,000 feet of subsurface tunnels. The tunnels are part of a $142 million project that will provide DEP with the ability to release water from the reservoir into Schoharie Creek to facilitate dam maintenance, respond to potential emergencies, mitigate flood risk for downstream communities, and enhance downstream habitat for fish and wildlife. The release works are expected to be completed in the year 2020.

The release works are one component of a larger $400 million program aimed at strengthening the 90-year-old Gilboa Dam and ensuring that Schoharie Reservoir continues to provide reliable, high-quality drinking water to New York City in the future. The program began with the full-scale rehabilitation of Gilboa Dam, a $138 million project that finished in 2014. It will also include upgrades to the Shandaken Tunnel Intake Chamber and site restoration work. DEP implemented the program of repairs and upgrades at Schoharie Reservoir more than a decade ago to achieve modern dam safety standards at Gilboa Dam.

“DEP believes it’s important to provide regular updates to local government officials, emergency managers and residents in Schoharie County as we continue to build and upgrade infrastructure at the reservoir,” DEP Acting Commissioner Vincent Sapienza said. “New York City has depended on Schoharie Reservoir to provide nearly 15 percent of its daily drinking water, and our neighbors downstream rely on its infrastructure for public safety. The work we are doing now will ensure that both objectives are met for decades to come.”

DEP began construction of the new release works at Schoharie Reservoir in July 2015. Thus far, the City has made substantial progress on excavations for an intake at the bottom of the reservoir and a release outlet near the creek. Work crews have also completed the construction of a 182-foot-deep gate shaft that will serve as the starting point for tunneling. The 9.5-foot-diameter tunneling machine will be lowered down that gate shaft this week. Once it begins tunneling, the machine is expected to excavate about 20-40 feet per day. The micro-tunneling machine is an unmanned machine that will be operated by remote control from the surface. Operators will track the progress and performance of the machine by watching it on monitors inside a control room. While the machine drives the tunnel ahead, personnel will only enter the tunnel if the machine needs maintenance of if cutters on the head of the machine need to be changed.

The machine will drive two tunnel sections that total 2,118 feet, running as deep at 185 feet below the surface. The first leg of the tunnel will stretch 1,188 feet from the gate shaft to a valve chamber on the eastern bank of Schoharie Creek. The valve chamber will be located about 1,000 feet downstream of Gilboa Dam. A second leg of the tunnel, stretching 930 feet, will run from the gate shaft to the intake structure at the bottom of Schoharie Reservoir, several hundred feet south of the dam. Once workers bore into the bottom of the reservoir, a specialized dive team will remove the micro-tunneling machine from the 135-foot-deep water and install the remaining parts of the intake structure. The construction of both tunnel sections is expected to take 6 months.

The valve chamber—which acts as the portal that releases water into the creek—will include two valves capable of releasing about 65-1,550 million gallons of water each day. A third, smaller valve will be capable of smaller releases up to 65 million gallons per day.

Releasing water from Schoharie Reservoir will support multiple goals related to reservoir operations, public safety and conservation. The release works will provide DEP with the capability to draw down the reservoir for periodic maintenance and in response to potential emergencies. The release tunnel would also help DEP mitigate flood risk for downstream communities by releasing water to counterbalance snowpack in the Schoharie watershed. Currently, DEP releases water equivalent to 50 percent of the amount contained in the snowpack throughout the reservoir’s watershed, which creates room in the reservoir to capture additional runoff during the spring melt. In the future, the release chamber may also be used to provide a conservation release downstream of Gilboa Dam to support fish, bird and other natural habitats by providing a baseline flow in Schoharie Creek. In December 2014, DEP submitted a study to the New York State Department of Environmental Conservation (DEC) that examined the potential for a conservation release and a revamped program of flood mitigation releases. The study was a requirement of the state permit that allowed DEP to rebuild Gilboa Dam. A decision on conservation and flood mitigation releases is pending DEC’s review of the study.

Gilboa Dam was built from 1919 to 1927 and impounds Schoharie Reservoir, the northernmost reservoir in the City’s water supply system. Schoharie Reservoir can store up to 19.6 billion gallons of water, and it accounts for nearly 15 percent of the drinking water delivered to New York City each day. Schoharie Reservoir collects water from a 314-square-mile watershed. It diverts that water through the 18-mile Shandaken Tunnel, which discharges into the Esopus Creek where it travels another 11 miles before entering Ashokan Reservoir. From Ashokan Reservoir, the water flows south through the Catskill Aqueduct to New York City.

DEP manages New York City’s water supply, providing more than 1 billion gallons of high-quality water each day to more than 9.5 million New Yorkers. This includes more than 70 upstate communities and institutions in Ulster, Orange, Putnam and Westchester counties who consume an average of 110 million total gallons of drinking water daily from New York City’s water supply system. This water comes from the Catskill, Delaware, and Croton watersheds that extend more than 125 miles from the City, and the system comprises 19 reservoirs, three controlled lakes, and numerous tunnels and aqueducts. DEP has nearly 6,000 employees, including almost 1,000 scientists, engineers, surveyors, watershed maintainers and other professionals in the watershed. In addition to its $70 million payroll and $166 million in annual taxes paid in upstate counties, DEP has invested more than $1.7 billion in watershed protection programs—including partnership organizations such as the Catskill Watershed Corporation and the Watershed Agricultural Council—that support sustainable farming practices, environmentally sensitive economic development, and local economic opportunity. In addition, DEP has a robust capital program with $20.7 billion in investments planned over the next 10 years that will create up to 3,000 construction-related jobs per year. For more information, visit, like us on Facebook, or follow us on Twitter.

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