Gilboa Dam
- Location: Gilboa, NY
- Owner: New York City Department of Environmental Protection
- Technique(s) Utilized: High Capacity Dam Anchors
Background
Gilboa Dam is located in New York’s Catskill Mountains, approximately 150 miles north of New York City. The 79-year-old dam impounds the Schoharie Reservoir, which supplies a significant portion of water used by the residents of New York City.
In October 2005, a study concluded that the dam did not comply with current engineering standards for safety. In response, The New York City Department of Environmental Protection launched an emergency dam rehabilitation program in 2006. The chief component of this program is the installation of high-capacity anchors to stabilize the dam. The DEP awarded Nicholson the $20 million “Emergency Contract” for the anchors in March 2006.
Nicholson used 5 drilling rigs to install 79 anchors; 47 drilled vertically through the dam crest and 32 inclined anchors installed through the dam face from a temporary work platform designed and constructed by Nicholson. The anchors range in length from 175 to 230 feet and have loads of 1,500 to 2,040 kips. The largest anchors have 58 strands. Also included in the contract was the installation of 4 pre-production test anchors, dam instrumentation including 2 extensometers and a data acquisition system, 15 subsurface investigation borings, and the design and installation of a temporary debris fall protection system.
A project of this magnitude required a comprehensive safety and quality control plan and staff to monitor the work. In addition to a full-time Nicholson staff overseeing safety and quality control, an independent quality control firm was hired to monitor quality and an independent safety consultant was hired to monitor safety during all construction operations.
The project was completed well ahead of the contract scheduled milestone dates and well within the Owner’s budget. The project was recognized as the McGraw-Hill Construction Best 2007 Public Works project in New York Construction.
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