An acid containment pond, constructed in 1987 with an HDPE geomembrane liner is at the end of its functional life. A condition survey conducted in 2016 identified a very large number of dam-aged and deteriorated locations. Prior to exhuming the geomembrane preparatory to replacement, a pro-gram of sampling and laboratory testing was conducted to quantitatively assess the liner condition. The test results were assessed with regard to their serving as an indicator of the deterioration, and by exten-sion, the remaining functional life. The determination of index and ageing-related