Sorry for all of the questions!
EPDM liners are now out of stock in most places...Until January!
If I have a 30×40×4 foot hole, vertical sides, in Virginia red earth dirt...
Will the walls cave in being vacant for 3-4 months?
Will it fill with water and not dry up?? I can use a sump pump, but rather not have muck clay left to deal with and dry out.
I'm finding reviews of HDPE contradictory. Many say all good things, others have tons of bad things. It's strong to some, not needing a liner and tougher against rips n tears. Others are opposite, saying it's weak and will scratch, which will slowly cause cracks and leaks. It's a ton lighter, which is good, because it's just me and husband who will have to carry it. I don't mind it not being super flexible, like EPDM. I've used PVC liners for the bogs, and know those are stiff and do get brittle quickly. The HDPE is supposedly a little easier to handle than PVC and much stronger.
I won't be putting any holes in the liner, will all be coming up over the edge. So, no issues with leaks from plumbing holes.
That would be the only liner available to me right now.