Clearwell is fine structurally at this point but I'd rather not see it get any worse. I'm not sure it's a design problem because, heck, it's potable water with a pH of 6.7! And an air stripping tower was designed to remove the CO2 but never funded.
Have never used Xypex, spec'd it twice, but for water containment in an old concrete storage tank and in an underground elevator room that had moisture problems.
What I'd like to know, is what is the tolerable levels of CO2, etc that will not affect concrete. I.E. what are the limiting parameters to design new tanks without protection? I understand from a source at AWWA, there was a similar condition with a Langlier Index of +something that exhibited similar conditions. Thanks for the help.