MOISTURE FLOW-THROUGH MUNICIPAL SOLID-WASTE - PATTERNS AND CHARACTERISTICS

Vertical moisture flow through compacted municipal waste layers is mor e complex than the one-dimensional, uniform Darcian drainage flow thro ugh a constant homogeneous medium as modeled in HELP. Channeling and f low along wetting curves produce irregular and more rapid breakthrough times and leakage rates. Tests of compacted municipal waste show dist inct channeled flow in two to three streams in cylindrical cells. Furt hermore, practical field capacity is substantially lower at 0.136 than the HELP default value of 0.292. Porosity, while similar to the defau lt value of 0.52, varies with compaction ratio from 0.58 to 0.47. As a result, practical unsaturated hydraulic conductivities are 10(4) to 1 0(5) higher at 1.2 . 10(-3) to 1.7 . 10(-2) cm/s than the HELP default of 1.2 . 10(-7) cm/s. As a result, waste default values should be rev ised in current models, while new leachate generation models need to a ccount for channeled flow.