Obviously, the smaller is the size of the soil-pore diameter, the more likely that water will occlude that run of the soil pore. Occlusion of the soil pores with water limits product movement through soils. This second figure illustrates a latter stage of product contamination of the soil. It is apparent from this figure that not all of the soil becomes saturated with product, as a separate phase. The surface tension of the water trapped by capillary forces in the smaller pore sizes prevents the movement of free product into many of the soil pores.
Free product tends to migrate through the larger soil-pore sizes.
The product will coat the walls of the soil pores and eventually coat the surface of nearby soil particles. Product layers may coalesce with other product layers and occlude short runs of soil pores just as does water. These discrete, disjunct runs of product trapped in the capillary pores are often referred to as ganglia of product. The third figure illustrates that point in time when only clean ground water enters the system. Since only clean water is entering the soil pore system, then the flushing of contamination from the soil is now possible.