peter p@n wrote:

I dug a big hole (about 9000 square feet surface; 7 feet max. depth; bank
at 4:1 slope) to make a waterfoul and wildlife pond. I have to use a
liner. The selection is between EPDM and HDPE.
which one is better?

For that size, I really think you have to go with HDPE. EPDM is way too
heavy to work with at that size (it was as much as I could handle alone for
about 250sq ft. surface - about 1000 sq.ft. of actual EPDM).

For a size where you could use either, I wouldn't say either was really
better, just different.
--
derek