Md = JA, = JdA (1-14)
 A

This can be also thought of as the spatial integration of contaminant flux across the control plane

[Basu et al., 2006]. The units of contaminant mass discharge are mass per time [M/T].

 Stroo et al. [2003] identified the need for field data of mass discharge at sites undergoing

source removal. Estimates of the mass discharge across the source zone and downgradient

transects will be evaluated over a six-year period following the 1998 ethanol flood and presented

in Chapter 3 of this thesis.

1.12 Benefits of DNAPL Source Depletion

 Mass flux may be more important than the actual mass in the source zone [Rao et al.,

2002; USEPA, 2003; NRC, 2005]. Through a contaminant source region of very slow

groundwater velocity, the mass flux maybe very small due to the low Darcy flux. However, a

small mass of residual PCE can produce a long plume of contaminated groundwater in a region

of high groundwater velocity. Large reductions in mass discharge from remedial efforts should

produce significant decreases in concentrations reaching downgradient receptors, and decrease

site longevity [Rao et al., 2002]. In the past decade several alcohol flushing field tests have

demonstrated the ability to reduce a field source zone DNAPL mass [Rao et al., 1997; Jawitz et

al., 1998; Sillan, 1999; Jawitz et al., 2000; Falta et al., 1999; Brooks et al., 2003]. Although

aggressive source removal rarely will achieve total site groundwater concentrations below

maximum contaminant limits (MCLs), contaminant flux reductions have been demonstrated.

This has spawned considerable debate on the benefits of source depletion [Sale andMcWhorter,

2001; Rao et al., 2002; Rao and Jawitz, 2003]. Due to a shift in consideration to the

downgradient receptors of a contaminant source's plume, risk based corrective action (RBCA)