Three Phase — Two Immiscible Liquids and Air in the Unsaturated Zone

5 Three Phase —Two Immiscible Liquids and Air in the Unsaturated Zone 

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

The viscosity of separate LNAPL products varies significantly, ranging from far less to many times that of water. Flow of LNAPL in the unsaturated zone is largely dependent upon viscosity and soil grain size. Finer-grained materials have a higher residual saturation of water, which restricts the number of pores available for LNAPL entry in this region. 

FIGURE 5.9 Relative permeability relationships controlling the flow of two immiscible fluids. (After Leverett, 1939.) 

As more LNAPL enters the soils, it increases the pressure on the moving front, which allows increasing displacement of water. If a sufficient quantity of sufficiently mobile oil is available, it can produce a pressure head large enough to displace water through the funicular zone and to form a distinct interface at the top of the capillary fringe. 

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