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June 16, 2011


Farrell Sklerov / Michael Saucier (718) 595-6600

DEP Begins Reconstruction of Gilboa Dam

Upgrade Will Extend Life of Dam by Up To 100 Years

Environmental Protection Commissioner Cas Holloway today announced the start of the major construction phase to upgrade the Gilboa Dam in Schoharie County. The work will extend the useful life of the dam for 50 to 100 years, and bring it into compliance with the latest state and federal standards, including an enhanced capacity to safely release water in the event of a dam safety emergency — a design feature critical to protecting the dam and communities downstream. The reconstruction of Gilboa Dam — which started with emergency stabilization work in 2005 — is the most significant dam reconstruction project in the city's water supply system.  The current phase follows the installation of crest gates to control the level of the reservoir, and site preparation to facilitate the reconstruction of the dam, which started in 2009. The major reconstruction includes a new spillway control section to safely pass reservoir overflow, the installation of anchors in the west wall of the dam, which will provide additional stability; the extension and stabilization of two other walls, which will improve drainage and stability; the refurbishing of a gate chamber and existing stone masonry, which will support the new crest gate system; and the upgrading of instrumentation and surveillance systems, which will provide enhanced monitoring and inspection capabilities. The total cost of the project, including the crest gates installation and site preparation, is approximately $350 million and is scheduled to be completed by 2016.

"Ensuring the safety of the Gilboa Dam, and all of DEP's dams, is critical for the safety of the surrounding communities and our ability to supply water to nine million New Yorkers," said Commissioner Holloway. "Since 2005, DEP has taken steps to securely stabilize Gilboa dam, and this construction work will rehabilitate and upgrade the dam to serve the water supply system for another 100 years. Mayor Bloomberg has prioritized infrastructure investments to ensure that New York City remains a place where people want to live and do business; this $350 million project — though 150 miles from the city line—is a critical component of that strategy. I would like to thank the residents of Gilboa and other surrounding communities for their patience and support for this project, which we'll work to complete as expeditiously as possible."

"NYCDEP has worked with Schoharie County to insure the safety of the county residents, by installing the anchors and siphons in 2006, as well as being a partner in the installation of the Audible Early Warning Siren System that was installed in all the towns along the Schoharie Creek from Gilboa to Esperance," said Harold Vroman, Chairman of the Schoharie County Board of Supervisors.  "NYCDEP continues to work with Schoharie County in the planning of the construction and refurbishing of the Gilboa Dam by building a  temporary bridge to keep construction traffic off the main road, by upgrading instrumentation, surveillance systems and the installation of crest gates.  NYCDEP continues to communicate with Schoharie County as this project moves along and I feel that when this project is completed, with proper maintenance, the Gilboa Dam should be durable for another 50 to 100 years."

In 2006, DEP strengthened Gilboa Dam to improve its safety after an updated assessment. A 220-foot by 5.5-foot notch was removed from the western end of the dam to lower water levels and facilitate stabilization work. Four large siphons were installed to almost double the capacity to remove water from the reservoir and also facilitate repairs, and 80 anchoring cables — consisting of bundles of 58 steel cable strands, 14 inches in diameter — were installed through the dam in order to secure it to the underlying bedrock, increasing the stability of the dam.  To accelerate the completion of the project, site preparation work began in September 2009, which allowed the initial site work to progress while the design for the dam reconstruction continued.  This work consisted of construction of site access roads, a spoils disposal area, site storm water controls, a temporary bridge, field engineer's office complex and other work to support the main construction work. Additional work in the current phase includes the construction of a concrete batch plant, demolition of existing stone and concrete, the placement of reinforced mass concrete, the construction of water diversion walls and additional reconstruction work around the surrounding walls and dam.

Since 2002, DEP has invested more than $248 million in upgrading dams as part of a multi-year capital program to upgrade and improve upstate water supply facilities. DEP is upgrading all of its dams and spillways to comply with state guidelines, starting with its oldest dams in the East-of-Hudson watersheds. Twelve dams have been upgraded over the last 25 years. DEP plans to commit another $417.5 million until 2021 to complete the dam reconstruction program.

The Gilboa Dam is part of New York City's Catskill Water Supply System, and is located within Schoharie County at the northern point of the Schoharie Reservoir in the Town of Gilboa. Constructed from 1919-1927 and placed into operation in 1927, the dam has been in service for more than 80 years. The Gilboa Dam is a classic gravity dam design, consisting of a 160-foot high by 1,324-foot long spillway constructed of mass cyclopean concrete with a 3- to 5-foot thick masonry façade of mortared quarried stone on the downstream face, and a portion of the upstream face. This gravity and embankment dam impounds the Schoharie Reservoir, the northernmost reservoir in the Catskill System.

DEP's upstate dams form the backbone of the city's drinking water supply system — impounding rivers and lakes, allowing water to collect in reservoirs, which eventually ends up in the distribution system. The city owns 32 "high hazard" dams based on the likelihood of serious economic damage, environmental harm, and loss of human life if they were to fail. In addition, DEP has purchased 69 small dams through the Land Acquisition Program since 1997.

Operating and maintaining DEP's network of dams is outlined in Strategy 2011-2014, a far-reaching strategic plan that lays out 100 distinct initiatives to make DEP the safest, most efficient, cost-effective, and transparent water utility in the nation. The new plan, the product of nearly one year of analysis and outreach, builds on PlaNYC, Mayor Bloomberg's sustainability blueprint for New York City. The plan is available on DEP's website at

DEP manages the city's water supply, providing more than one billion gallons of water each day to more than nine million residents, including eight million in New York City, and residents of Ulster, Orange, Putnam and Westchester counties. Approximately 1,000 DEP employees live and work in the watershed communities as scientists, engineers, surveyors, and administrative professionals, and perform other critical responsibilities. New York City's water is delivered from the Catskill, Delaware, and Croton watersheds that extend more than 125 miles from the City, and comprises 19 reservoirs, and three controlled lakes. The DEP police protect the watershed and its facilities, including seven wastewater treatment plants. For information, visit or follow us on Facebook at

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