The Geosynthetic Research Institute (GRI) test method GM34 “Test Methods, Test Properties and Testing Frequency for Ethylene Interpolymer Alloy (EIA = PVC + KEE) Geomembranes” sets forth a set of minimum properties that must be met, or exceeded upon manufacture. In the context of quality systems and management, this specification is targeted toward manufacturing quality control (MQC). The properties listed in this specification were obtained by testing multiple commercially available products according to the latest standard test methods established by either the American Society of Testing and Materials (ASTM) or the Geosynthetic Research Institute (GRI). The unique aspect of this specification is the requirement for long-term performance testing of the geomembranes. Three different endurance tests are specifically designated to challenge the longevity-weathering-aging of the EIA geomembrane. This paper describes the rationale of selecting the relevant test methods and the background for establishing the specified values. Also presented in this paper is the frequency required when performing the various tests.