Field Performance of a Compacted Clay Landfill Final Cover at a Humid Site |
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Authors: | William H Albright Craig H Benson Glendon W Gee Tarek Abichou Eric V McDonald Scott W Tyler Steven A Rock |
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Affiliation: | 1Associate Research Hydrogeologist, Desert Research Institute, Nevada System of Higher Education, 2215 Raggio Parkway, Reno, NV 89512. E-mail: Bill.Albright@dri.edu 2Professor and Kellet Fellow, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin–Madison, 1415 Engineering Drive, Madison, WI 53706. E-mail: benson@engr.wisc.edu 3Laboratory Fellow, Battelle Pacific Northwest Laboratories, 3200 Q Avenue, Richland, WA 99352. E-mail: glendon.gee@pnl.gov 4Associate Professor, Dept. of Civil and Environmental Engineering, Florida State Univ., Tallahassee, FL 32310. E-mail: abichou@eng.fsu.edu 5Associate Research Professor, Desert Research Institute, Nevada System of Higher Education, 2215 Raggio Parkway, Reno, NV 89512. E-mail: Eric.McDonald@dri.edu 6Professor, Dept. of Natural Resources and Environmental Sciences and Dept. of Geological Sciences and Engineering, Univ. of Nevada, Reno, Reno, NV 89557. E-mail: tylers@unr.edu 7Environmental Engineer, USEPA National Risk Management Research Laboratory, 5995 Center Hill Ave., Cincinnati, OH 45268. E-mail: Rock.Steven@epamail.epa.gov
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Abstract: | A study was conducted in southern Georgia, USA, to evaluate how the hydraulic properties of the compacted clay barrier layer in a final landfill cover changed over a 4-year service life. The cover was part of a test section constructed in a large drainage lysimeter that allowed continuous monitoring of the water balance. Patterns in the drainage (i.e., flow from the bottom of the cover) record suggest that preferential flow paths developed in the clay barrier soon after construction, apparently in response to desiccation cracking. After four years, the clay barrier was excavated and examined for changes in soil structure and hydraulic conductivity. Tests were conducted in situ with a sealed double-ring infiltrometer and two-stage borehole permeameters and in the laboratory on hand-carved blocks taken during construction and after four years of service. The in situ and laboratory tests indicated that the hydraulic conductivity increased approximately three orders of magnitude (from ≈ 10?7?to? ≈ 10?4?cm?s?1) during the service life. A dye tracer test and soil structure analysis showed that extensive cracking and root development occurred throughout the entire depth of the barrier layer. Laboratory tests on undisturbed specimens of the clay barrier indicated that the hydraulic conductivity of damaged clay barriers can be underestimated significantly if small specimens (e.g., tube samples) are used for hydraulic conductivity assessment. The findings also indicate that clay barriers must be protected from desiccation and root intrusion if they are expected to function as intended, even at sites in warm, humid locations. |
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Keywords: | Landfill Hydrogeology Compacted soils Lysimeters Dewatering Landfills Humidity |
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