The visualizations show the gradual increase in molar sum concentrations leaving the

source zone from 1999 to 2001. The sum peaked in 2002 and then decreased in 2003 until

dropping markedly at the end of the sampling period in 2004. For most of the monitoring period,

chlorinated ethane concentrations emanated from the mid-depth of MLS-1, the deepest locations

of MLS-7 and mid and lower regions of MLS-3. By 2004, the source zone plume was primarily

originating from the upper middle zone of MLS-1 and the mid-depth of MLS-3. MLS-7 had

essentially ceased as a source.

 Mravik et al. [2003] observed a PCE concentration rebound in the RWs and IWs to pre-

remedial levels after observing initially low concentrations immediately following the flushing

event. The source zone MLS detected a slight increase in molar concentrations in January 1999,

five months after the flood. However, the large increase in molar sum concentration detected in

2001 and 2002 was due to the stimulation and reductive dehalogenation of PCE by microbes.

Four months following the ethanol flood, December 1998, TCE concentrations increased from

non-detect to 0.17 mM. Five months following the flood, January 1999, DCE was detected in

several source zone MLS locations.

3.4 Downgradient Transect Concentrations

 In addition to monitoring the source zone, the MLS installed downgradient of the

source zone were sampled as well. The results of the downgradient control plane analysis are

summarized in Table 3-3. The transect consisted of MLS-9, MLS-10, and MLS-11 for the time

period from 1998-2003. The molar sum concentration values are lower than the source zone

transect due to dilution and dispersion in the 10 m of aquifer between the two control planes.

Looking at the mean MLS well results, the transect recorded stable behavior for the first two post

remedial-years while recording a slight increase in the center of the transect in 2000. This is an