Pond Boss Forums POND CONSTRUCTION Building a dam More Dam issues

Hello - I am new here. I posted this as a different thread, but it seems like I should have asked it here instead.

I recently purchased a home in Vermont with a large pond. There is a 300 ft earthen dam with a 5ft wide corrugated metal vertical drain that runs into 4 ft wide horizontal drain. The metal pipes are in disrepair. They are rusted and full of holes. In addition, the LLO is inoperable.

The total pond area covers about 8 acres. The average depth is probably 4-6 feet. The deepest point is probably about 10 ft.
There is a secondary spillway that allows water to flow around the dam in case of an emergency, so I don't see the water overtopping the dam.

Is there any way to repair the spillway pipes without actually replacing them? I am told digging out the pipes and putting in new ones would be extremely expensive. But I have also heard that liners or PVC can be used as an insert to repair.

In addition, I am also wondering how to fix the LLO, since that prevents lowering the pond depth in case of an impending storm.

The state is also asking me to get soil testing & water inundation testing done. I would really appreciate any advice or contacts for inexpensive service providers.

Please help. All comments are welcome.

Wow, a 4' diameter culvert. That is a big outlet.

Is there a small creek that runs into your pond? Or do you have a gigantic watershed (drainage area) for the pond?

Why is the state involved? If your rotten culvert collapses, there is a very high probability that the dam would wash out and send all of the pond water volume downstream. Are there any humans or habitations at risk if that happens?

Sorry for the bad (apparent) news.

I am NOT a dam expert, but I believe that it would be very expensive to replace a culvert style outlet of that size.

If you had a 10" diameter outlet, you might be able to block the downstream end, fill it all with cement to remove the collapse risk, and install a siphon-style water outlet to handle your heavy rain events. That would be prohibitively expensive at the apparent sizes that your pond dam requires.

How large is your pond in surface acres? What is the average depth? What is the depth at the deepest point? Is there an emergency spillway?

If you add that information to your post, then hopefully some of the experts will chime in and give you some helpful advice.

P.S. You should probably go back and delete your other post, so all of the responses are consolidated under this "active" post.

Good luck getting your pond back into good shape!

Hello -

Thank you for the response and I appreciate your reply. I will edit my post so it includes the information you suggested and answers your questions.

Welcome to the forum! I've had a long day and can't figure out what a LLO is. Can you elaborate?

You could have a company put in a coffer dam around the rotted culvert, replace it, then pull the coffer dam. I have no experience sleeving something that big.