Hydraulic Conductivity of Three Landfill Clay Liners

Clay liners have been used as a means of leachate containment at landfills in Wisconsin for over 10 years. Many of these liners are 1.22–1.52‐m (4–5‐ft) thick and their construction is well documented. Since 1980, the Wisconsin Department of Natural Resources has required “collection basin lysimeters” to be installed at most clay‐lined sites to measure the quality and quantity of leakage from a discrete portion of the liner. These devices were initially required to provide a method for monitoring soil moisture in the unsaturated zone beneath the clay liners because in most cases suction lysimeters had not functioned properly. More recently, volume measurements from regularly sampled lysimeters have been used to estimate field hydraulic conductivity of clay liners. Field hydraulic conductivities calculated from the measured rate of seepage into eight separate lysimeters at three operating landfills is always less than $1\times {10}^{-7}\mathrm{cm}/s\text{.}$