This report presents the results of a research program conducted at The Ohio State University from October 2007 to May 2010, to investigate the use of a geocomposite in the construction of landfills for coal combustion products (CCP). Specific CCPs investigated were FGD gypsum, fly ash and stabilized FGD material. The objective of the research program was to determine the hydraulic conductivity of the CCPs with the geocomposite and to determine if the CCPs would go into solution and continue out through the geocomposite with the leachate. The project objective was accomplished with a coordinated program of testing and analyzing small scale laboratory specimens under controlled conditions and intermediate scale wetland experiments.
The small scale laboratory tests using the CCPs alone yielded higher hydraulic conductivities compared with the CCPs combined with the geocomposite. In the intermediate scale testing, all of the CCPs and geocomposite systems exhibited lower hydraulic conductivities than laboratory measured values for the systems, except for stabilized FGD which yielded a higher value.
The percent solids in the laboratory leachate reached low values after about two pore volumes of water had passed through the CCP and geocomposite system, 0.02% for FGD gypsum, and 0.40% for stabilized FGD. The fly ash and geocomposite system showed high percent solid values initially and clogging occurred in the effluent tubes before one pore volume of leachate was reached. Field testing showed the total suspended solids in the leachate for all CCPs decreased to below detection levels by the time three pore volumes of water had passed through the basins.