This project examines the effects of two flue gas desulfurization (FGD) sludges on 18 liner materials used to contain them. Seventy-two special test cells were constructed 1 ft. in diameter by 2 ft. high. Devices were installed to collect the leachate from each test cell for determination of the quantity of leakage and the leakage rate (permeability), and to provide storage for subsequent chemical analyses. Ten admix liner materials were mixed with a clayey silt and compacted in the bottom 6 in. of the test cells. Six spray-on and two prefabricated membrane liners were placed over 6 in. of compacted silty sand. Four gallons of sludge was then added to each test cell along with enough tap water to bring the liquid to within 4 in. of the top. Each test cell was covered and pressurized to simulate a disposal area approximately 30 ft. deep. Physical and chemical tests were conducted on the liners before exposure to the FGD sludges, and after 12 and 24 months of exposure.