deposition morphology and dissolution behavior in natural media [Broholm et al., 1999; Frind et

al., 1999; Rivett et al., 2001; Broholm et al., 2005; Rivett andFeenstra, 2005]. Rivett and

Feenstra [2005] monitored the dissolution and plume development of an emplaced

multicomponent DNAPL source in a natural sandy aquifer. Both source mass and source

strength were monitored over a three year period by soil coring and a downgradient multilevel

sampling well transect. Dissolution fingering and groundwater flow bypass resulted in 77% of

the source mass remaining after 3 years and they predicted source longevity of 25 years. Pooling

and entrapment in low permeable media fostered lower hydraulic conductivity zones, leading to

groundwater flow bypassing. The study predicted that as pores are cleaned out by dissolution,

additional bypassing will follow these new DNAPL free paths [Rivett andFeenstra, 2005].

 This process is called aging. Over time, many groundwater flow paths are cleaned out by

dissolution. The flow paths still containing higher residual or pooled DNAPL will divert

groundwater flow around these zones, making them diffusion limited [NRC, 2005]. The aging

process may reduce plume concentration but may also increase source longevity since

groundwater preferentially flows through cleaner, higher conductivity paths. As Sages began

operation as a drycleaning facility in 1968, the single component PCE spills may have occurred

many years ago. The low groundwater velocity has limited the natural dissolution of subsurface

PCE. However, many flow paths may have been cleaned out by dissolution over time, making

Sages an aged DNAPL site.

 Because PCE is very slowly solubilized by groundwater flow, scientists and engineers

have been researching means to enhance the dissolution process. One of these methods is in situ

alcohol flushing.