|Attenuated Anaerobic Dechlorination of Groundwater Using HRC® MACTEC - Harding ESE
The primary objective of the demonstration was to determine the effectiveness of a permeable reactive barrier wall in eliminating trichloroethene (TCE) and its degradation products from a ground water plume. Specifically, the developer claimed that 90 percent of the samples collected from the downgradient "critical" wells would meet the Massachusetts ground water criteria (GW-1) after a reasonable period (about four months). GW-1 criteria for the target contaminants are as follows: TCE (5 parts per billion), cis and trans-1,2-dichloroethene (70 parts per billion combined) and vinyl chloride (2 parts per billion).
The demonstration was initially expected to last about six to nine months, which was anticipated to be ample time for determining if the primary objective had been met. In fact, the demonstration was extended to over 24 months as TCE concentrations were found to decrease more slowly than expected. Water level measurements indicated the project area to be very flat. Although this would suggest low flow of water, analysis of various parameters indicated that movement of Hydrogen Release Compound® and other constituents was occurring. Concentrations of volatile organic compounds (VOCs) and other parameters varied in adjacent wells throughout the evaluation, possibly due to nonuniformity in the formation; nevertheless, each well showed similar trends in VOC changes.