ethanol is non-partitioning and completely miscible, thus it will be slowly carried away by the

site groundwater velocity. As ethanol was removed from the source zone by natural gradient

flow and microbial degradation, daughter products of PCE dechlorination were detected.

Table 3-1. Measured ethanol concentrations in the source zone transect at Sages.

Well Depth 12/1998 01/1999 02/2002 10/2002 10/2003
 m bgs (%) (%) (%) (%) (%)

MLS-1 8.08 0.029 0.000 0.0037 0.0006 0.00000
 8.69 0.330 0.152 0.4260 0.1475 0.00014
 9.07 1.449 1.381 0.2486 0.1328 0.00016
 9.45 0.139 0.080 0.0464 0.0004 0.00006
 9.91 3.283 2.243 0.0407 0.0009 0.00001
 Mean 1.046 0.771 0.1531 0.0565 0.00007
 Std Dev 1.373 0.999 0.1802 0.0766 0.00007

 MLS-3 8.08 0.041 0.352 0.0165 0.0001 0.00000
 8.69 1.185 1.260 0.0882 0.0640 0.00002
 9.07 3.095 4.584 0.0087 0.0133 0.00000
 9.45 2.333 1.299 0.0488 0.0017 0.00000
 9.91 5.650 5.999 0.0459 0.0016 0.00000
 Mean 2.461 2.699 0.0416 0.0161 0.00000
 Std Dev 2.126 2.449 0.0314 0.0273 0.00001

 MLS-7 8.08 0.332 0.094 0.0000 0.0000 0.00000
 8.69 1.146 0.484 0.0221 0.0005 0.00000
 9.07 1.755 1.833 0.0370 0.0009 0.00000
 9.45 1.496 0.493 0.0680 0.0006 0.00000
 9.91 0.582 0.262 0.3375 0.0002 0.00000
 Mean 1.062 0.633 0.0929 0.0004 0.00000
 Std Dev 0.600 0.691 0.1389 0.0003 0.00000


 There appeared to be a threshold toxicity of ethanol on the microbial population. Once

the ethanol concentration dropped below 1%, there were increases in TCE concentrations in

groundwater flowing across the transect. This is consistent with Mravik et al. [2003]. They

reported laboratory column degradation of PCE in Sages site materials when the ethanol

concentration was less than 1%. In Figure 3-1, the ethanol and TCE concentration is plotted for

the December 1998 sampling.