Worms HATE alkaline soil.
I spread a heavy coat (15' band all around) of ground limestone all around the pool twice a year and have eliminated the problem almost completely. It take me about 300# to do what I have but at $3.00 per 50# bag it is well worth it and won't hurt the grass.
A couple of years ago I opened the pool to find close to 50# of dead worms on the bottom Talked to the local Ag extention office (PSU) and got the tip from them ---- IT WORKS!!
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