Landfill contents leach chemicals, it is their nature.
Because it can never be predicted what chemicals will be present, or what chemicals will be formed when everything has stewed together for awhile, I don't think anyone can promise that any liner will be impervious to all leachate. Because of this, locating a landfill anywhere near a water supply seems pretty risky to me. And in that case, I suggest rabble rousing in the neighboring communities so the short-sighted ones will see a very real, very immediate threat to their wallets. It worked for us.