I am from Portugal and built a small pond with poliethilene liner down a hill where in the winter/rainy season runs a water stream. Well I thought that the water would go into the pond over it, superficially but it seems there is a lot of groundwater running towards the outside layer of the liner pulling it and I can hear water falling down there as if the soil has collapsed inside. I think by now this water could have filled the pond. It seems a tough job! note: this is a sandy soil.
I wonder if anyone has an opinion about the risk of this and suggestions to solve this problem. I would really appreciate to have your opinions/advice
Welcome to the forum! How much water is inside the liner?
Was the ground compacted before the liner put in place, or just excavated out, smoothed and then the liner placed?
Is the liner, where the stream runs, below the level of the stream bottom?
If the stream runs fast enough, it could carry dirt with it into the lined pond and make cleaning out the pond difficult. Or did you dig a settling pond before the lined pond, to allow the stream to slow down, which allows the dirt to settle out of the stream water before it enters the lined pond?
Worst case scenario enough soil gets washed out under the liner the liner pulls loose from it's achoring when the lined pond fills up. However that depends on how much wash out you have and how much the liner has to stretch.
If it was possible i would get as much soil as possible back into the collapsed area and fill in the lined pond ASAP. The hydrostatic pressure in the liner will hopefully hold down flow under the liner once the pond is full.
Please stay a safe distance away from the cave in and have someone else as an observer in case something happens!
I have a similar situation with a 2 meter by 2 meter by 1 meter lined pit that receives my well water that I can directe to various ponds via underground gate valves and pipe. There is a circular sand lense on the uphill north wall of the pit about 5 inches in diameter, which if I drain the lined pit allows ground water from uphill to build up under the liner. When the well is flowing and lined pit is full it's not an issue. I had some ground cave in next to the liner from which I was able to fill back in.
I used to drain the pit for the winter but no longer do. As long as the water level is below my exit pipes freezing does no harm.
Last edited by Cecil Baird1; 10/18/1411:38 PM.
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