Pond Boss Forums POND CONSTRUCTION Building a dam High water table and pond liner

I'm planing a 20,000 sq/ft pond. We have sandy loam soil so I bought a RPE liner to use. In the spring, the water table is at at ground level and stays high for 3-4 weeks. I'm worried the liner is going to bubble from hydrostatic pressure.

If I create a berm around the whole pond about 1ft higher than the spring high water mark, will this create enough down pressure to keep the liner from bubbling?

Is there another way to keep the liner down?

Thanks

So long as the water level in the lined pond stays higher than the water table the forces on the liner per square foot (pressure) should be greater than the forces on the non-pond side of the liner. This would keep the liner pushed against the earthen bottom and sloped sides. This assumes no spring like flows in the water table the would increase the forces to be higher in a particular area and that none of the liner is vertical...I'd keep the sides at a 45 slope or more level. 3 (run) to 1 (rise) slope (18° measured from horizontal) is pretty common for safety reasons.

Laying earth, sand, smooth gravel. or the like can also help.

Disclaimer: I have no experience with lined ponds...just know a bit about physics.

Will the hole be void of water when the liner is installed. It would be a real trick to do that otherwise.

Thanks,

Yes, I'll install the liner in the next few weeks now that the water table is bellow the deepest part of the pond.

There must be some type of hydrostatic pressure since the water flows slightly. But I'm not sure if the pressure is happening where the pond will be or up stream.

Maybe I can leave a few extra feet of liner rolled up on the edge and if I don't have enough down force I can increase the berm and still have liner to cover it.

I agree, I'd build the pond a bit higher than the surrounding land, but you still have to think about how to get water into the pond to make up for evaporation. The key to it all is not have lower water pressure in the pond than is in the surrounding soil.

I'll put in a shallow well by the pond to pump out of. In spring it will be full and hopefully in summer I can still get something from it. Worse case, we have a cabin 200ft away with a deeper drilled well we can pump from.

The pond is in a low spot that's protected from the wind, I hope evaporation isn't going to be a big problem.

Instead of drilling a shallow well, a small forage pond might be a better option.

You could dig a deep pit in one of your lowest spots at the same time you have excavation equipment on location for your big pond. That would be a very small incremental cost.

If you get the pit 5-10' below the summer groundwater level, then you could have a ready water source for the big pond when needed. Further, it is cheaper (initial cost & electricity) to use a small centrifugal pump when lifting water only a few in elevation compared to a submersible well pump.

Finally, if you size it right for your needs, then you could use it as a forage pond, grow-out pond, ornamental pond, etc.

In very wet years you could even put a trash pump in the little pond and move water on through your watershed if the groundwater elevation is starting to put some pressure on the liner of your big pond.

Just throwing out more ideas while you are still in the planning stages.

Good luck on your project!

Thanks, good idea. I might burry a culvert oriented up and down in the pit, so when it fills in, the culvert will let me access water deeper down.

Absolutely a good option if a pit doesn't fit your plans.

I have buried perforated corrugated pipe (drain tile) with a sleeve in the coarse sands of the little creek on our land. I teed it into a plastic 12" culvert set vertically. It works very well to supply our water tanks if we have to do a controlled burn during a dry spell.

Drilling holes in your culvert and just wrapping a screen prior to installation would probably be easier for your situation.