Hydraulic conductivity under highly saturated conditions

FIGURE 5.8 Representative hydraulic conductivities under highly saturated conditions. (After Testa, 1994.)... 

NAPL will migrate from the liquid phase into the vapor phase until the vapor pressure is reached for that liquid. NAPL will move from the liquid phase into the water phase until the solubility is reached. Also, NAPL will move from the gas phase into any water that is not saturated with respect to that NAPL. Because hydraulic conductivities can be so low under highly unsaturated conditions, the gas phase may move much more rapidly than either of the liquid phases, and NAPLs can be transported to wetter zones where the NAPL can then move from the gas phase to a previously uncontaminated water phase. To understand and model these multiphase systems, the characteristic behavior and the diffusion coefficients for each phase must be known for each sediment or type of porous media, leading to an incredible amount of information, much of which is at present lacking. 

Transport experiments were conducted on the intact cores at a variety of water contents using saturated and unsaturated flow experimental techniques (24, 25, 38). The intact cores were epoxied into PVC pipe and enqtlaced into fabricated Plexiglas endcaps. The cores were hydraulically connected to a membrane inside the endplate to facilitate either saturated or imsaturated flow. Under saturated conditions, influent solution was ponded (1-2 cm) at the upper boundary to facilitate delivery into the cores, and efiluent was collected in a high-capacity fraction collector. Under unsaturated conditions, a vatmum-... 

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