Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? Repairing Dam with Culvert?

I have a pasture pond that the dam washed out of at the spillway. It's eroded and cut pretty deep. I don't have the means to drain it, rebuild the core, and haul in the dirt to make it new again. What I do have is a skid steer and a couple of big metal culverts. Any chance a guy could successfully build up the eroded section with a culvert in it and salvage the pond? Or is this just asking for problems?

Bummer, catscratch.

As heavy as your skidsteer feels to load onto the trailer, it still does NOT provide much compaction.

Have you ever used a portable vibratory plate compactor or a jumping jack compactor? (I can rent either at my local place.) I believe they would compact your repair section sufficiently if you built it up in lifts and added moisture as needed.

However, either one is slow going for a large area, AND they run much more efficiently with a large, strapping lad on the business end.

I think the best piece of equipment for that job (in my limited experience) would be a compaction attachment on an excavator. I know of two styles, a rolling sheepsfoot or a vibrating plate run off of the hydraulics. However, I expect that would be a difficult piece of equipment to find as a rental. Maybe a larger construction company might have one and you could pay their operator to run it when they got rained out of their big road project for a few days? (Or some similar good luck, since those guys don't take tiny jobs unless the boss is a friend.)

What is the diameter of the new culvert? Are you going to add an anti-seep collar? The most difficult area to compact is right along the culvert. Even a trickle of water along that route will eventually move out enough particles of your fill material to create a leak.

Good luck on your dam repair job!

Is the dam only washed out at the spillway or is more of the dam washed out?

If only the spillway is washed out, the spillway needs reshaped. Mostly likely flattened and widened so it does not wash out again.

A culvert in the spillway is going to be counter productive to function of a spillway.

Check out "Letsdig18" on youtube and the other pond builders, they install culvert overflows all the time, there is a specific way to install them and if not done correctly they wont last. As was said youll need antiseep collars and proper compaction with the proper material which you can find info on a plastic culvert manufacturers website. Also, as mentioned you can't put an overflow at an outflow - not a good idea.

Also look up monk overflow and weir/spillway construction. After having this happen you do it right the next (and hopefully last) time.

If you go the route of incorporating the culvert, check out AquaBlok for the anti-seep collar. There would be no mechanical compaction needed and the product would "flow" around the contour of the pipe.

Once again, I see I may have replied after missing an important point from the OP.

My answer assumes you had a deep cut out of the dam that washed out your outlet pipe.

I think jludwig may be answering as if the dam did NOT have an outlet pipe, but rather your overflow spillway got cut out. (Reading your OP now makes me think that interpretation is more likely.)

I hate to ever argue that you can get by with LESS compaction, but if you are just replacing the top few feet of the overflow spillway, then perhaps you can get by with less than perfect compaction.

The compacted material must resist the hydrostatic pressure of the water trying to trickle through a dam, and it must make the dam strong enough to resist the lateral force of the impounded water that is trying to slide the dam down the slope. A few feet of water is much easier to resist than 22' of water at the face of the dam working against the core trench.

Further, as jludwig state above, re-shaping an overflow spillway is a big help. The lateral force can be resisted by just the bulk of a wide shallow slope on the back side of the spillway.

Finally, if not armored, then an overflow spillway must be close to perfectly level throughout its entire crest and downslope. Spreading out the erosive force of the water is the only way a vegetated spillway can function. For example, if cows cut a path down in the crest and slope, then that is going to channel all of your initial water flow. Once it starts down-cutting, all of the water will go through the cut until the pond inflow rate exceeds the outflow rate through the cut. Even when the water starts flowing over the entire face of the spillway, much more erosive force will be concentrated in the cut.

Lots of great info and stuff for me to research/learn, keep it coming guys!

The erosion is a cut in the spillway. The dam is intact, but the spillway is cut very deep. Currently no overflow tubes. My thoughts were if I could fill the erosion back in and make it level with the dam that I could add overflow tubes to keep it from eroding again. No clue if I can make it work though.

I think there are several good limestone quarries out in your area? (If you had any rock left over, I am sure you could find a good habitat use IN one of your ponds.)

One option would be to skip the culvert and make an "armored" half pipe along your overflow spillway.

I think laying down heavy landscape fabric, and then placing 10-12" quarry stone, and then backfilling the crevices with 1-3" aggregate would make an overflow spillway chute that could handle a lot of erosive force.

How often did this pond overflow in the past? If once per ten years, and only a foot deep when running full, then you could probably get by cheaper doing the culvert. However, does the culvert make it to the toe of the slope of the overflow spillway? Once erosion starts at the culvert outlet, it can rapidly chew its way back up the slope under certain conditions.

Lots of rock in the area! I suppose it'd be best if I posted some pics then ask for advice again (since you all don't exactly know what it looks like and are having to make some guesses).

I honestly don't know how often it has overflown. It's WAAAAY back in the back pasture, over the hill, and no road going to it. Never had fish in it so my visits were seldom at best. I just know it's in bad shape and other than some grunt I don't have much to put into it.

Does your dam have a pipe in it? If so, how much freeboard is between your pipe and spillway?

Flatter, wider, and gentler slope for the spillway is most likely going to fix your erosion issue.

No pipe. Just a damn with a very deeply washed out spillway at one end of it.

That makes it a bit of a challenge. The simplest solution is going to widen the spillway and reshape the existing ground behind the spillway so the water flows more gently when it leaves the pond.

The problem with putting overflow pipes here is going to restrict the flow of water and now water is going over the low point in the dam in times of emergency.


What's the height difference between the pond and the eroded spillway? Also the distance between these two points?