From the GMA Techline
I need some assistance in comparing two geosynthetic clay liners for a project where the specification gives a total bentonite mass required of 4500g/m2 and a target hydraulic conductivity of < 5 × 10-11.
We have an option of a liner that far exceeds the requirement of the hydraulic conductivity, with a slightly lower bentonite mass.
Are there studies available showing the advantage of extra bentonite other than achieving the hydraulic conductivity, such as the bentonite’s performance as an attenuation layer?
(Michael | New Zealand)
Reply: Good question and let me address the bentonite mass from a historical perspective.
The industry did, indeed, start at 4500g/m2 but the focus shifted to hydraulic conductivity shortly thereafter. It was found that 4000 and then 3700g/m2 was adequate from this perspective.
Thus, current specifications, such as GRI-GCL3 call for a minimum mass of 3700g/m2.
I have not had push-back from specifiers for using this value in years. That said, your value of hydraulic conductivity is right on.