Its called easy weave liner and easy pro produces it. Now its states that you dont need to cover it soil because the strength of the liner is stronger but you do that to balance your pond. Its basically like the xanvan liner that came out several years ago its a woven liner, As to your question about rain runnoff, there are different ways to do one would be to cut the liner into the hillsides and then cover back over the top the of the liner with soil this allows the surface water to go directly into the pond. You will need to install a drain tile under the liner as well as a over flow. The bottom drain would be a hard perforated tile that you would through the berm of the lowest point on the hillside so some escavating is needed if that makes sense to you. The overfill i would simply glue into into the same pipe that is coming from the bottom so that it all goes the same direction.
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