Pond Boss Forums POND CONSTRUCTION Building a dam Concrete dam

I’m potentially looking at a piece of ground and was interested in putting a 1/4 acre pond in the lower end of the lot. I do concrete foundations for a living, so cost for the concrete wall is not an issue. Could I potentially pour a concrete wall on the three sides marked in blue on the pic for the dam? Would I still have to mound dirt up on both sides? How would you seal something like that off to keep it from leaking? Highest point of dam would probably be 10-12’ tall

Also, another reason for the concrete walls, was to keep it as close to the property lines as possible with out needing a huge dam base thus making the pond itself smaller

I recognize that you are an expert with concrete and are probably very comfortable working with that material.

However, very few ponds of a 1/4 acre or larger are made with concrete. (It is usually used for small decorative ponds in people's yards.)

How often have you seen a basement foundation or an outdoor retaining wall that did NOT have a crack after five years? If your dam is 12' tall, there is going to be constant hydrostatic pressure trying to push water through any fine crack. Finally, how will you seal the BOTTOM of the pond?

That said, we usually try to encourage people to build ponds!

Would the seller let you go in with one of your mini-excavators from work and dig a few test trenches? Knowing your subsoils is the key to planning your pond project. If you have enough good clay, your pond project should be viable. Also, clay is "self-healing" in this application. If your dam shifts slightly, then the clay smears across itself and there is no crack for water to leak through.

I would recommend you look at the satellite view of the area around this property. If you see several ponds, then your soils are probably acceptable to build a pond.

Another step would be to use the Soil Survey to get a rough idea of the soils. Here is the link.


Web Soil Survey

(There is a little learning curve to get your soils on that site. If you can't get through, you can send me your exact location in a private message and I can pull the data for you.)

If the soils are not conducive to building a pond, and/or you really want to build very close to the property lines, then a pond liner is probably your best option.

You can put the side boundaries close to the property line where there is not much slope change from the existing slope to your pond slope. However, if you build the dam up 12' above the existing grade, you will need to back the liner with a big berm of excavated material. Usually a 1:3 slope can hold steady and be mowed, but a 1:4 slope is more stable and more comfortable to drive on your mower! That means your dam needs to be 36' or 48' from your back property line.

I hope that gives you some more ideas. Good luck on your pond project!

Good info from Rod.

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I'm no professional on the subject but a 12 ft tall concrete wall would need some support to hold it against the force of 12 ft of water I would think, which I guess if you just banked good dirt up halfway or better on the backside would create a lot of support for the wall, and the bottom half is where most of the pressure would be, that would allow you to get a little closer to the property line.

Than there would be the problem of access to the dam end of the pond, I guess you could build a walkway over the top of the wall but you will also have the issue of the depth right inside the wall. if something were to fall into it or something, you would need to swim all the way to the end of the wall to get out, or build some kind of escape stairs or ladder in several places to accommodate an accidental slip and fall.

It probably could be done, just going to need some planning, also there is the dirt that comes out of the pond on the inside to make a bowl for a deeper pond that would hold a lot more water, you'd need a place to go with that. just a wall across the end of the existing topo probably wouldn't hold a very big volume of water.

Posts like the first post in the thread makes me wish that the OP would check back in and update us. Last time they were on the forum was May 2025. Original post was September 2024

esshup - IMO most members here are just Users and Not Givers nor longer term contributors. The good useful advice they received here did not even cost them one penny. They were not thankful enough to return and update us as to what happened. I am learning this shows the mentality and attitude of many people.