HYDRAULIC COMPATIBILITY OF GEOTEXTILE-COMPOST SYSTEMS IN LANDFILL COVERS
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As annual generation of municipal solid waste increases every year, sustainable practices must be promoted in landfill construction. Landfill covers are required by federal regulation to cap the municipal solid waste and to prevent leachate formation. The use of compost as the vegetative layer in landfill final covers is one way to improve the sustainability of landfills. Current literature on compost shows it to be a superior vegetative facilitation material compared to the traditional topsoil material. In order to successfully use compost in landfill cover applications, hydraulic compatibility of the compost and underlying geotextile filters must be adequate. The hydraulic compatibility of various compost, topsoil, and geotextiles have been explored by performing long-term filtration (LTF) tests. Upon completion of the LTF tests, particle size analysis, permittivity tests, piping measurements, and image analysis were conducted to determine clogging and retention performances. When the clogging ratios and piping measurements were considered, every compost-geotextile and topsoil-geotextile combinations yielded acceptable clogging and retention performance. A parametric study was conducted to determine if different characteristic pore size and grain sizes influenced the laboratory observed clogging ratios; currently, no relationships exist. Existing filter selection criteria successfully predicted retention behavior and failed to predict clogging behavior. Conducting more soil-geotextile compatibility tests will be needed to propose a new filter criterion for clogging. Based on limited LTF data, compost is not likely to promote clogging in geotextiles; however, additional leaching and geotechnical tests are required to assess the nutrient leaching and shear behavior of compost layers on landfill cover slopes.