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CONSTRUCTION, MONITORING, AND PERFORMANCE OF TWO SOIL LINERS
Citation:
Krapac, I. G., K. Cartwright, B. R. Hensel, B. I. Herzog, T. L. Larson, S. V. Panno, J. B. Risatti, W. J. Sue, AND et al. CONSTRUCTION, MONITORING, AND PERFORMANCE OF TWO SOIL LINERS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/S-92/024 (NTIS 92-157923), 1992.
Impact/Purpose:
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Description:
A prototype soil liner and a field-scale soil liner were constructed to test whether compacted soil barrier systems could be built to meet the standard set by the U.S. Environmental Protection Agency (EPA) for saturated hydraulic conductivity (< 1 x 10'7 cm/s). In situ ponded infiltration rates into the prototype liner were measured with the use of two large, (5-m diameter) sealed double-ring infiltrometers. The saturated hydraulic conductivity of the liner was estimated from the infiltration data to be no more than 3.6 x 10-" cm/s. Fluorescein and rhodamine WT dye were allowed to infiltrate the prototype liner for 46 days. Dye patterns observed during excavation of the prototype line indicated that lateral flow occurred between lifts and along the interface between soil clods. Although the prototype liner met the EPA requirement for hydraulic conductivity, the dye flow paths indicated a need for better bonding between lifts and for reduced soil clod sizes to eliminate preferential flow paths in the liner. The field-scale liner (7.3 x 14.6 x 0.m) consisted of 6 compacted lifts each 15-cm thick. Full-scale equipment was used for compaction. This liner was compacted at an average moisture content of 11.5%, 1.5% wetter than the optimum moisture content as determined by the Standard Proctor test. The mean dry density of the liner was 1.84 g/cm3, 93% of the maximum Standard Proctor density. Based on 1 yr of measurements of water infiltration into the liner, estimates of saturated hydraulic conductivities were 3.3 x 10* by large-ring infiltrometers, 5.3 x 10-8 by small-ring infiltrometers, and 6.7 x 10"8 cm/s by a water balance analysis. Measurements of soil tension using pressure transducer tensiometers indicated that the wetting front had reached a depth greater than 20 cm.