Sometimes they form a slick on the surface of a body of water and other times they will sink to the bottom to form a gooey mixture that fragments and scatters when disturbed. Soluble compounds do not necessarily form sheens or a slick. Because they are soluble, they can move with thegroundwater with relative ease. Groundwater has not been observed in the top sand layer. Gravity is the predominate force that will move the liquid down to groundwater.
Capillary pressure is the force that causes lateral movement.
The extentof the plume will be determined by factors including the volume of the spill, groundwater fluctuation and the magnitude of the slope gradient. The minimum concentration is determined by soil type and structure. However, as the lengthof time increases,the concentration of immobile residual saturation willlikely increase. The plume at Gold Creek exhibited a rapid movement towardsthe Susitna River at the beginning. Table 1 presentsthe various soil parameters for the soils found on the site.