From the GMA Techline
Subject: Liner thickness I use an equation from your Designing with Geosynthetics, 2nd Edition, to calculate liner thicknesses. Recently, I calculated a geomembrane thickness of 100 mils for a landfill with 200ft of waste. The supplier stated that he had never seen liner that thick used. Upon reviewing other designs, it seems that engineers commonly specify 60-mil liner without calculating a necessary thickness. In your experience, is this calculation often neglected? Is there a maximum thickness that becomes unreasonable? (Eric, New Mexico)
Reply: You ask a fair question and I stand by my technical formulation. Sure, 100 mils is thick but it is not uncommon. In Europe, all HDPE is 80- to 120-mils-thick, and it is never 60 mils. Conversely, the U.S. EPA weighed in on HDPE thickness about 20 years ago, saying that its minimum thickness should be 60 mils and everyone took this as the design or default thickness.
I doubt if thickness is calculated by most engineers and they simply “go with the flow.” Not a very good state-of-the-practice in my opinion.