Gilboa Dam Information
Update: December 15, 2006
The DEC announced on December 14 that the stabilization project has been completed. This project consisted of installing a debris boom across the lake, the cutting of a notch in the top of the dam, installing 4 syphons and installing 80 anchor cables to secure the dam to the bedrock below. A full-scale reconstruction project is scheduled to begin in 2008.
The Gilboa Dam and it's Schoharie Reservoir are owned and operated by New York City's Department of Environmental Protection. Finished in 1927, the reservoir holds about 20 billion gallons of water.
On October 25, 2005, the city issued a Public Advisory stating "...recent investigations reveal that safety factors associated with modern engineering practices are not met by the Dam in its present state."
The DEP has started repairs. Two steps have been completed. The first was a 5.5 foot deep notch cut into the top of the dam. This is to allow water to spill keeping the top of the dam dry for repair work. The second is the installation of 4 syphons to draw down the water level.
Future steps will be to install anchors through the dam and into the bedrock to stabilize the dam. This is scheduled to be completed by September of 2006.
There are a number of possible triggers for a dam failure including earthquake and sabotage, however the most likely would be a gradual and prolonged inflow of water run-off into the reservoir leading to the dam's failure. Since the theoretical failure-point is when the water level reaches 1138 feet, it is likely that we will be at flood conditions long before a dam failure. This allows us to predict the possibility of a dam failure. Use the "Water Level Prediction" link to see the current water level as well as predict flood conditions.
Prior to the notch being cut, the top of the dam was at an elevation of 1130 feet above sea level. While the top of the dam hasn't changed, water will start spilling when it rises to the level of the notch at 1124.5 feet above sea level. Flood stage is when the water level rises to 1130.5 feet above sea level with a flow rate of 10,000 cubic feet per second. You can see the current water level on the Water Level Prediction* page.