Update, 11:15am: DEP deputy commissioner Paul Rush confirms in a telephone conversation with the Watershed Post that the Gilboa Dam is NOT compromised and is NOT in danger of failure, and says that the water currently spilling over the top of the dam is roughly 1/5 of the volume that was spilling on Sunday, August 28.
Rush told us that current elevation of the water level at the Gilboa Dam was 1131.45 feet, which translates into a flow rate of about 24,500 cubic feet of water per second. On August 28, he said, the elevation at its highest was up to 1137.97 feet, with a flow rate of roughly 110,000 cubic feet per second. (This is up slightly from the DEP's estimate at the time of 1137.95; Rush said the agency went back and analyzed the data, resulting in the slightly higher figure.)
Rush said that the sirens are for use in a situation in which there is potential for dam failure, not for flooding situations in general.
"The protocol for those sirens was, the only time they would be used was when there was a dam emergency. They never had a protocol in place to use them for flooding," he said.
Rush said there had been some discussion with local officials about using the sirens in flooding situations, but that a protocol for using the sirens for flooding had never been agreed upon.
"They have not implemented that," he said.
Rush could not comment on Schoharie County's decision to evacuate, or whether it was related to the dam siren failure.
From the Schoharie Tattler: A must-read post on possible scenarios involving the Gilboa Dam. Contains detailed information about what happens at different elevation/flow rate levels, the risks associated with a dam failure situation, and a very thorough and reasoned discussion of when the low-lying areas below the dam should evacuate.
9:42am: Just got it officially from Schoharie County Emergency Services: There is a Schoharie-county-wide order for residents in low-lying areas to get to higher ground. The sirens for the Gilboa Dam are not operating, so do not wait to hear them. If you are in a floodplain, get to higher ground. Here's the transcript of my call to the woman doing reverse 911 calls, which is the only number I've been able to get through on in Schoharie County:
There aren't any problems with the dam. We're notifying resident of flooding due to rainfall. The dam sirens are not working at this time. They were anticipated to be back up and running in about ten days, so they're not working now.
There is an emergency order for the whole county: we are sending out information on reverse 911 calls for anyone in low-lying areas to go to higher ground. Middleburgh, Schoharie, etc.
