• Corporate HQ, NY
  • Melville, NY
  • Iselin, NJ
  • Ossining, NY
  • Mount Laurel, NJ

Gilboa Dam Reconstruction


A HAKS-led joint venture is providing Construction Management services for the reconstruction of the Gilboa Dam. Constructed in 1927, the Gilboa gravity and embankment dam consists of a massive 155-foot-high by 1,326-foot-long stair-stepped spillway constructed with a 3- to 5-foot-thick masonry façade of mortared quarried stone blocks. The dam impounds the 5-mile Schoharie Reservoir in upstate New York, which provides 16% of New York City’s water supply. The reservoir and dam form part of the Catskill Water Supply System, which provides 40% of the city’s water. A 2005 inspection found that the facing on the dam had been damaged by freeze/thaw cycles and the mechanical components needed repair and updating.

In order to extend the life of the dam another 100 years and bring it into compliance with New York State Department of Environmental Conservation safety standards, New York City Department of Environmental Protection (NYCDEP) initiated a $400+ million reconstruction project. NYCDEP initially undertook emergency stabilization work to strengthen the dam, and interim improvements were completed in 2006.

Phase 3 of this massive undertaking, the Reconstruction of the Gilboa Dam, has been completed two years ahead of schedule in spite of $18 million in damage and a nine-month delay caused by Hurricane Irene. The $140 million dam reconstruction phase, which began in 2011, adds up to 12 feet of mass concrete to the face of the dam and required approximately 120,000 cubic yards of concrete. The project team completed reconstruction of the spillway control section, removed and reconstructed the spillway channel and plunge pool, installed a new under-drain system, modified and repaired the existing spillway training walls, modified the existing upstream embankment slope to meet current stability requirements, placed earthfill on the crest of the embankment section to create a level and uniform surface, refurbished the upper gate chamber and made further improvements to the instrumentation and surveillance system. Two 6-foot-diameter temporary siphons were installed to enable NYCDEP to draw down water levels in the reservoir for snowpack mitigation and support project construction.  Construction will continue until 2021.

Industry recognition included the 2015 ACEC New York Gold Award for Engineering Excellence and the 2014 Concrete Industry Board New York Award of Merit.