Doctor G Fred Lee has some bad news for the EPA: landfill liners are going to fail. The doctor has written approximately five hundred papers and reports about landfills, groundwater, liners, and related issues; he’s been studying the matter since the 1980s.
Leachate is garbage juice that drains out of landfills as the garbage decomposes. It’s nasty stuff, composed of all the worst elements of what we throw away and concentrated in liquid form. When landfills leak, leachate can contaminate groundwater and get into water supplies. You don’t want to drink leachate.
When landfills are constructed according to EPA regulations (Subtitle D of the RCRA), a liner must be laid down before the garbage to keep leachate from entering the groundwater. This liner consists of four parts: 1) a filter layer to keep the garbage from poking holes in the liner below, 2) a leachate collection layer (gravel or something like this) to let the leachate drain, 3) a layer of HDPE plastic at least 60-mil thick, and finally, 4) a layer of clay or some material with low permeability to seal things in.
As a note: in my own ignorance, I assumed 60-mil meant millimeters. I was confused when I saw a sample of the plastic liner: it wasn’t much thicker than the cardboard cover of a hardback book. It turns out that mil refers to thousandth of an inch, which makes 60-mil about the same as 1/16th of an inch.
Liners constructed to this standard will eventually fail, says Dr Lee. “Ultimately the plastic sheeting layer of such a landfill liner will deteriorate to the point where it will be ineffective in collecting leachate” (Lee, Flawed Technology, 10). Dr Lee explained to us some of the reasons that the HDPE liner will fail:
- Installing a large sheet of plastic over hundreds of acres, even one as tough and thick as the 1/16th inch HDPE required by Subtitle-D, is not a delicate job. Heavy machinery is used and the likely-hood of gashes or holes in the plastic is high.
- Although the filter and leachate collection layers are made to protect the HDPE liner, as time passes garbage can end up near the plastic and the myriad objects present in garbage can puncture or tear the plastic as upper layers are compressed.
- Free radical polymer chain scission will cause breakdown of the plastic over time (usually 40 to 120 years). Dr Lee believes that landfills will still be producing significant leachate at this time.
In addition, the bottom clay liner will fail for different reasons, according to Dr Lee:
- The clay is subject to dessication if it does not have some amount of water present, and as it dries it will shrink and crack.
- Since the areas we are talking about are sizable, it is possible that they will settle at different rates and in time one area may be significantly lower or higher than another, leading to a fracture or breach of the clay liner.
- Clay, although it has a low permeability, is still permeable
Dr Lee says his primary role is that of an engineer; he believes that landfills are needed and sees it as his job to help people site and build them. He has several suggestions for changing landfill liner regulations, such as using a double composite liner with leak-detection system in between, better information and choices when it comes to siting landfills, and more thorough groundwater monitoring systems.
At the end of the day, Dr Lee believes the true cost of landfilling waste is somewhere between two and three times what is now commonly experienced. He asks the question, What politician is going to vote to double or triple waste disposal costs when the affects of poor regulations will only be felt by future generations.