Pond Boss Forums Thread Like Summary - Repair Options For A Large Dam Breach

Hello Everyone!

I'm new here and new to pond management in general. I "had" a 5 acre pond up until 2 months ago when my area received almost 5" of rain in 48 hours which overtopped my 50 year old earthen dam (10 foot high, 40 for wide at its base, 15' wife at its top, and 150' long with no core) and breached a large hole in it (10 foot wide) and drained it down to 1/2 acre all because beavers blocked up my 2 spillways. The pond is a catch basin for a ~75 acre watershed so it rarely lost any water. In fact, it always had water flowing out of it every time it rained much.

So I would like to know if anyone has some reasonable options for repairing this large breach.

I've been told by a semi professional dam builder to take it down, bring in new clay and put in a core, and then rebuild it (extremely expensive ($50,000 at least) but I'm not sure why it would now need a core when it didn't have one for 50 years and it would still be intact if it hadn't been for a family of beavers).

My personal idea is to now use the existing breach and build a concrete wall in the center of the dam where it peaks, that extends into the existing dam 5' on either side of the breach and extends 5' below the existing pond bottom and make it about 8' tall. My question though is how thick should this concrete wall be? How would I calculate that? I would also form buttresses behind the wall and make concrete steps behind the wall so the water flowing over it won't wash out the back of the dam. I would bulldoze the existing exposed pond bottom to fill in the lost dam material. However, the semi pond expert said that material looked like it had too much organic material in it to hold water. But I'm thinking if it's just laying against a concrete wall then why would that matter? Would be be right about his thoughts just by looking at the dirt and not testing it?The dam currently has about a 5 foot amount of original material in the breached section that is holding the 1/2 acre of water back.

One other idea I was hoping would work, is the cheapest but maybe not even a good idea, would be to doze the exposed pond bottom into the breach while compacting it properly and that's all I do except unblock my spillways and try to run the beavers off or install a siphon system or other anti beaver devices to allow the pond to drain when it rains. My expert said that you can't just put new or old clay in the breached area even if you compact it with their 80,000 compactor because the water will eventually breach it again although he couldn't explain how or why. And one more thing, the dam never leaked a drop before all this.

So that's all I can think of doing. Would anyone else have any thoughts about this at all? I'm open to any/all suggestions. Thanks everyone!

It's hard to answer that question without being on-site to see what is involved, how easy/difficult it will be to get equipment there, where to source the proper fill material from, etc., etc.