by the small PCE discharge increase. By the end of the study period, PCE and DCE flux rate
decreased significantly. As these two chlorinated ethenes dominated the sum mass discharge, it
decreased as well. As a measure of total risk to downgradient water supplies, the decrease at the
end of the study is favorable.
The numerical integration of the PCE curve in Figure 3-5 determined that 2.65 L of PCE
reached the downgradient transect over the six-year post-remedial monitoring. The source zone
PCE curve integration calculated that 4.01 L removed from the source zone by enhanced
microbial dissolution over the same time period. The difference in these values was the
enhanced natural attenuation in the 10 m between transects. Thus, 1.36L of PCE was
biodegraded over the six years. The average rate of the PCE plume biodegradation over the six-
years of this study was determined to be 1.02 g/day.