I had my pool installed a little under two weeks and have noticed the there are two to three areas where the 1 inch foam underlayment is gaped by approximately 1/2inch. All the dirt is settling in those areas, which is nice and easy for vacuuming however concerned about damage the liner may endure. Am I stressing over nothing. I have contacted the installer and he said he could not quaranteed absolute smooth bottom and that separation could occur. I sure hope I here ok news because that would be expensive 600.00 more dollars of water shipped in.