Hydraulic characterization of municpal solid waste

The hydraulic properties of municipal solid waste (MSW) were evaluated at laboratory- and field-scales. Saturated hydraulic conductivity (K s) of MSW was measured in the laboratory at various dry unit weights and levels of decomposition using large- and small-scale permeameters. The water retention curve (WRC) and unsaturated hydraulic conductivity (K theta) were also measured in the laboratory for MSW at various dry unit weights and levels of decomposition. The field-scale Ks, WRC, and Ktheta were obtained using numerical inversion of data collected from field-scale lysimeter experiments.;Increases in the Ks of MSW were observed with increasing decomposition (at a fixed dry unit weight) because of increasing void ratio associated with solids loss. Decreases in the Ks of MSW at a given composition were observed with increasing dry unit weight because of decreases in void ratio. At field-scale, decomposition and compression occur simultaneously. Results from the DTBE indicated that solid volume lost to decomposition was high enough to increase void ratio and therefore Ks despite substantial settlement. An empirical relationship between the Ks of MSW and void ratio was developed that is applicable for MSW at various stages of decomposition with varying particle size distributions.;Changes in the WRC and Ktheta of MSW with increasing dry unit weight were consistent with expected increases in air-entry suction (i.e., decreases in the size of the largest pores) and decreases in Ktheta because of the compression of flow paths. Increasing decomposition resulted large degradable particles breaking down to smaller particles. Data obtained from the laboratory-scale WRC tests indicated increases in the size of the largest pores with increasing decomposition. Decreases in Ktheta with increasing MSW decomposition suggested that unsaturated flow through degraded MSW is confined primarily to small pores after large pores that develop because of decomposition drain under very low matric suction. At field-scale, Ktheta decreased with decomposition and compression. Empirical equations were developed to estimate parameters for unsaturated flow models using MSW dry unit weight.