Formatted Title
Installation of a Successful Activated Carbon-Based Permeable Reactive Barrier for Petroleum Hydrocarbons and 1,2-DCA
Background/Objectives
Managing dissolved contamination along property boundaries or adjacent to sensitive receptors has been an area of focus for the environmental industry as risk control measures are often required in conjunction with risk assessment or remediation. In the 1990s, permeable reactive barrier (PRB) using zero valent iron (ZVI) was pioneered which has since been widely applied for the treatment of chlorinated volatile organic compounds (cVOCs). Unfortunately, this “Iron Wall” is ineffective for petroleum hydrocarbons (PHCs). For years attempts have been made at creating a passive PRB for the long-term and sustained treatment of PHCs. Recently, the use of activated carbon-based injectates (CBIs) has been increasing and evolving. The objective of this talk is to present a case study completed at the field scale that presents how two different CBIs were used to create an injected PRB to effectively treat and control the migration of dissolved-phase PHCs across a property boundary. An interesting aspect of this work also included the requirement to treat the chlorinated solvent 1,2-dichloroethane (1,2-DCA) which was historically used in gasolines as a lead scavenger. This talk will summarize the staged implementation of the CBI PRB including design considerations, injection techniques used, results of the remedial design characterization, and lessons learned. Focus will be placed on a performance assessment of the two CBIs used (colloidal and powdered activated carbon) in addition to the impact of using KB-1® to address residual 1,2‑DCA impacts.
Approach/Activities
Field data will be presented from a case study where two types of CBI and modified KB-1® were used. The injection techniques will be discussed, one of which involved the injection of a slurry via a grid of interlocking, depth-targeted, temporary injection intervals to create the full-scale long-term PRB. A review of the geology, hydrogeology, injection program and the corresponding in-field and post-injection monitoring data will be presented, including the results of the robust remedial design characterization program.
Results/Lessons Learned
The presentation will ultimately review the persistence of the site owner, whose focus on the use of CBI led to the successful PRB installation. The first stage of the CBI PRB installation resulted in increased petroleum hydrocarbon groundwater concentrations along some portions of the PRB. A robust site characterization program was completed which allowed for a more thorough PRB design. The PHC groundwater concentrations decreased to generic standards after the second stage of the CBI PRB installation; however, minor exceedances of 1,2-DCA remained. The third and final stage of the PRB installation was the introduction of 1,2-DCA cultured KB-1® which ultimately led to the installation of the fully functioning and effective CBI PRB. All in all, the lessons learned from the above installation approach will be presented, along with how CBI can be used to successfully inject a PRB for PHCs and additionally how creativity and KB-1® can be applied to effectively treat 1,2-DCA commingled with PHC plumes.