dissolution [Falta et al., 2005b]. Furthermore, the model demonstrated that low NAPL

heterogeneity required greater mass removal to affect significant flux reduction, but source

longevity decreased after source depletion. The plume contained much higher concentrations,

but the source mass would be depleted more rapidly by natural dissolution [Falta at al., 2005b].

 Applying this theory to the Sages site, under only natural gradient conditions, the post-

remedial PCE distribution will act as a contaminant source for many years. However the

longevity and plume distance will decrease as a result of the 1998 flood. Additionally, the site

flux will be less concentrated than pre-remedial levels throughout the source life span.

 Another favorable outcome of DNAPL site source depletion modeling described the

reduction of plume strength and longevity with enhanced plume degradation [Falta et al., 2005b].

This leads to the selection of this site as a pilot study of the SERB technology. Residual PCE

may act as a reservoir for dissolved plume formation, but the unrecovered ethanol should foster

in situ bioremediation of PCE, reducing plume strength and longevity.

4.4 SERB Activity

 The SERB technology clearly demonstrated the ability to stimulate microbial reductive

dechlorination of PCE at the Sages site. Had this been a full scale remediation and not a pilot

test ethanol flushing technology, the mass recovery and resultant flux reduction in the RWs both

would have increased. Furthermore, greater NAPL removal would have decreased site mass

discharge and the source longevity. The site showed the common flux rebound that other

aggressive source removal projects have recorded. The four-month lag until daughter products

were detected can be attributed to microbial population growth and high residual ethanol

concentration toxicity. Ethanol concentrations needed to drop below the toxicity threshold of 1%

before biologically enhanced dissolution and degradation significantly increased.