From the GMA Techline
Subject: 3 questions
- How do I approach designing/specifying GM/GCL composite liners for MSW landfills? Do I simply adopt the GM13 standard, which is based on fundamental research, and then double-check that the leachate leakage rate is within acceptable limits for my specific project?
- What other material parameters need to be project specific? And is shear critical?
- Is there an established maximum acceptable leachate leakage rate for GM/GCL composite liners used for MSW landfills? I have read literature where typical action leakage rates (ALR) of 50–200 lphd were mentioned.
(K.O., A new IGS member)
- You should use the GRI GM13 specification for the GM and the GRI GCL13 specification for the GCL. That is exactly what they were developed for and should be used accordingly. All credible manufacturers know of their existence and produce products accordingly.
- The specifications are material specs, not design specs. Yes, shear strength of all surfaces adjacent to the GM and GCL must be assessed and compared to the site-specific shear stresses. It is a straight geotechnical design.
- ALR values are set by the regulator who is giving the permit for the project. That said, 50–200 lphd is, indeed, a common value and one that should be met using a GM/GCL composite with good CQC and CQA.