Evaluation of a Vegetative Landform Cap to Reduce Water Percolation




Master of Science (MS)


Plant, Environmental Management and Soil Sciences

Document Type



Exposure to large quantities of industrial wastes can pose significant environmental, health, and ecological concerns. A study was conducted at a Solid Waste Surface Impoundment (SWSI) in Baton Rouge, Louisiana to assess conventional and alternative landfill caps and their effects on water percolation. The objectives of this study were to evaluate 1) the establishment of common bermudagrass (Cynodon dactylon L.) and seashore paspalum (Paspalum vaginatum) soil caps; 2) chemical and physical properties of clay and topsoil and their ability to restrict water movement through soil profiles. Sixteen treatments of clay, topsoil, and/or combinations of the two soils at various capping depths up to 90 cm (36 in) in depth were constructed in 15 cm (6 in) clay lifts over the entire test area with the exception of control plots of exposed filter cake and topsoil-only capping treatments. All capping treatments were seeded with common bermudagrass and seashore paspalum. Data was subjected to analysis of variance and means were separated using Tukey¡¯s Studentized Range Test at a significance level of 0.05 (SAS 9.1, Cary, NC). Impounded waste had a high salt content, and excessive levels of calcium, magnesium, and chloride were detected. Common bermudagrass growth out competed seashore paspalum growth; therefore bermudagrass was the only grass species tested. As clay and topsoil depths increased bermudagrass coverage increased, and water percolation to the impounded waste was reduced. Soil caps comprised of 61 cm (24 in) of clay, and ¡Ý31 cm (12 in) of clay with topsoil maintained a greater barrier that limited capillary rise of salts and had ¡Ý90% bermudagrass coverage. Soil caps composed of 61 cm (24 in) of clay with or without topsoil, and 31 cm (12 in) of topsoil over 31 cm (12 in) of clay had a cumulative total of ¡Ü2.40 mL of water percolate to the impounded waste over 16 months. Based on 16 months of monitoring, the Louisiana Department of Environmental Quality standard cap composed of 15 cm (6 in) of topsoil over 61 cm (24 in) of compacted clay maintained soil stabilization, increased evapotranspiration, minimized water percolation, and contained impounded wastes.



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Committee Chair

Beasley, Jeffrey S.

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