Usually you only read about dams when one has failed. For a change, here is a dam that is being replaced. New Ossipee Lake Dam celebrated in Freedom
The existing dam is 135 years old, and showing signs of failure.
The upgrade was about 20 years in the making.
[DES Water Division Director Thomas] O’Donovan recalled the major flood of 1998 which he said caused $1 million worth of damage around the lake, which he said was due to the “inability to manage the impoundment correctly.”
Plans for the upgrade didn't start in 1998, but did start shortly after that in 2002. It took that long to get the design done, and approved and funding in place.
The new dam has a safer, modern spillway, has a larger flow capacity to reduce flooding and has automated spillway gates.
The old dam relies on stop logs which have to be added and removed manually, though they are currently jammed, making it impossible to manage the water level.
I can't find a decent photo of the existing dam that is in the public domain. Click the link at the top of this post for a view of the dam under construction.
New Hampshire has a couple of dozen "high hazard" dams that need attention. High Hazard refers to the potential of loss-of-life and economic impact in the event a failure, not a statement on the condition of the dam.
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