Thanks Rainman,
I had no idea what a 'coffer dam' was - but do now, thanks to YouTube
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https://www.youtube.com/watch?v=tVHV5NVCGOUBuilding a coffer dam would be an interesting project. Imagine i'd have to drain half the pond or more to get it to a level where the plates could be used to wall it off.
Another challenge is that the creek that was created from the drainage pipe - runs through a county park and into a river nearby. Not sure they would be keen on me flooding their park
I could probably get their interest though if they could visualize what would happen if the pipe had a catastrophic failure and it all drained at once. The river could easily handle the overflow.
Attached a picture to give an idea of what it looks like. The left side is shallow, and you can tell i have some water-plant issues on that end, plus a spring-fed swamp that the beavers have created. Odd thing is that we didn't have hardly any plant growth issues until about 10-12 years ago, about the same time the beavers set up shop. The right side, I've been told, was 50 ft deep when it was built in the 50's. The other side of the dam is a pretty steep hillside that goes down into a wooded valley.
