In contrast to the AFO barrier, the iron concentrations within the ZVI barrier are high, with most of the samples in the first 0.5 m of the barrier exceeding 6 mg/L. Redox conditions within the ZVI barrier are extremely reducing with no measurable dissolved oxygen and extremely negative oxidation reduction potential values in the range of -500 to -600 millivolts. Dissolved iron concentrations decrease substantially in the last 0.2 meter of the ZVI barrier as well as downgradient of the barrier.