Pond Boss Forums POND CONSTRUCTION Building a dam 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!

If I was in TN with that problem I would definitely get a hold of Michael Gray for an opinion on repair, and hopefully an estimate.

Ok thanks. What city does he live in?

From the Resources Guide:

Gray Construction

Contact:Jimmy Gray and Michael Gray
Address:Columbia, TN
Phone:(615) 308-5752
Email:mgrayconstruction@yahoo.com
Website:grayconstruction.net

Sorry. I thought I replied but didn't. I didn't think I could easily search his name but I found the same info Thanks.

The first repair guy said it would "probably" cost $50,000 to fix my dam. Would someone comment on that price please? Does that not seen awfully high?

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.

Plus TN ponds seem to frequently have large rock problems, something I know jack squat about (pricing or otherwise).

Oh ok. True. It's just that I read an article about a breach in NH of a city dam and it was only going to cost the city $35,000 I think it was which surprised me because it's a city and it's in NH. I would have guessed it would have been double or triple that price.

It does. There is a thick layer of sandstone 2-3 feet below the ground just about anywhere you dig.

UPDATE:

Life is crazy. Over this Memorial Day weekend I just happened to go to a lake nearby to fish, since my pond is sub par now. Before I left for the day, I went looking at the dam there and lo and behold they had about a 40 foot long concrete weir dam holding back the 225 acre lake. The freeboard of this dam was only 18" wide on top. But behind the dam face was a large amount of concrete instead of buttresses. I also don't know how deep the dam went but it was at least 10 feet thick at the bottom that tapered up to the 18" freeboard and it was about 10 foot high that I could visibly see. So as I was looking at all of that, a guy who lived next to the dam came over and asked me what I was doing. So I told him my whole story. And surprisingly, he knew the company who built that dam. So I'll be contacting them today although I have a feeling they don't work on little ponds. Anyway, I can't believe I found a lake nearby that has exactly the solution I was looking for. Now I just have to figure out how much concrete I need in case that company doesn't do small jobs. In any event, I'm fairly certain that is not going to cost me $50,000 to build a concrete dam that's only 10 feet wide. This will probably take months to get done so I'll update once a month just in case it might help someone in the future.