Assessing the Performance of Evapotranspiration Covers for Municipal Solid Waste Landfills in Northwestern Ohio

Evapotranspiration (ET) covers have gained considerable interest as an alternative to conventional covers for the final closure of municipal solid waste (MSW) landfills, but often produce higher rates of percolation in regions that receive more than $32\mathrm{cm}{\mathrm{year}}^{-1}$ of precipitation. The goal of this project is to design ET covers for MSW landfills in northwestern Ohio (long-term annual rate of precipitation of $83\mathrm{cm}{\mathrm{year}}^{-1}$) that produce rates of percolation $<32\mathrm{cm}{\mathrm{year}}^{-1}$, the rate considered acceptable by the Ohio Environmental Protection Agency (OEPA), and promote habitat restoration. To attain this goal, an adequate soil water-storage capacity was provided using dredged sediment amended with organic material. Two plant mixtures were tested to evaluate the performance of ET covers immediately following construction (immature plants seeded onto the soil) and in the future (mature plants transplanted from a restored tall-grass prairie that is more than 10 years old). ET covers were constructed in drainage lysimeters (1.52-m diameter, 1.52-m depth) and watered at a rate of 91.12 to $95.72\mathrm{cm}{\mathrm{year}}^{-1}$, which included simulated 100-year rain events (11.7 cm over 24 h) in July and October. During the 1-year monitoring period, the ET covers using the mature plant mixture produced considerably less percolation (0.12 to $11.44\mathrm{cm}{\mathrm{year}}^{-1}$) than the covers with the immature plant mixture (6.71 to $24.16\mathrm{cm}{\mathrm{year}}^{-1}$). Thus far, all ET covers have produced rates of percolation less than the maximum standard by the OEPA, and they will continue to be monitored.