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pHASSS OF CONTAMINATION <br /> The inadvertant_release of contaminants to the subsurface <br /> can lead to four phases of dearadation to the underlying ground <br /> - water.environment. These four phases cor list of .the fallowing: <br /> ° The adsorbed phase of contamination is the volume of j <br /> contaminant that is adsorbed by the soil matrix. -The <br /> amount of contaminants adsorbed depends on the grain <br /> size of.the impacted soils. The higher the sill: and <br /> clay content the greater the volume of contaminants <br /> adsorbed. Typically 60 - 80 percent of a loss c4�n.be <br /> " adsorbed by the underlying soils. The adsorbed phase f <br /> can be the source for vapors and/or a dissolved <br /> con <br /> cantration phase. Subsequent to development of a <br /> _ free product phave .or dissolved phase the adsorptive <br /> capacity of the sc' ls must be exceeded. <br /> ! ° The free product phase of contamination consists of the <br /> contaminant that exceeds the adsorbtive capacity of the <br /> Y !" soils and collects atop the water table or an <br /> underlying <br /> in permeable soil horizon (compacted silts 4 <br /> "i or clays), The volume of free product depends upon the <br /> e: initial amount of loss, depth to product barrier. (water <br /> table, low permeable soils) , adsortive capacity of <br /> sub soils, and length of time contaminants were exposed z <br /> to the subsurface. in some cases, the type of <br /> contaminant may be immiciable in water and free product <br /> phase adds to the magnitude of dissolved contaminant <br /> concentration and/or vapor phase plume. <br /> ° The dissolved phase consituent of a subsurface impact <br /> '_ depends on the volrme .loss, length of time in contact <br /> with the water table, and types of contaminant. The <br /> dissolved phasetends to travel faster than the free <br /> M product phase and typically is the first sign of <br /> i <br /> w.. <br /> 10 <br />