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Two funnel-and-gate permeable reactive barriers (PRBs) with settling ponds comprised of a composite liner (geomembrane and geosynthetic clay liners (GCL)) were installed at Resolution Island (BAF-5), Nunavut to contain residual polychlorinated biphenyls (PCBs) moving with the sediment and annual snowmelt. The long-term performance of the geosynthetics used in the PRB funnels is studied for physical integrity and diffusive barrier properties after nine years of operation. Exhumed geomembrane specimens are compared with virgin material by index testing: diffusive resistance to benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds, as well as puncture, burst, and tensile strength. Exhumed GCLs are evaluated concerning hydraulic conductivity, the mass of bentonite per unit area, and swell index. The migration of PCBs through the composite liner system by diffusion is modelled and the diffusive and sorptive properties of the geomembrane (D g = 1.7 × 10−14 m2/s, S gf = 160,000) and GCL (D e = 3.1 × 10−10 m2/s, bentonite plus fibers layer K d = 15 mL/g, cover geotextile K d = 12,000 mL/g, and carrier geotextile K d = 16,000 mL/g) were calculated. Modelling results estimate that the composite liner was successfully containing PCBs. This was confirmed by downgradient monitoring. The challenges of the location and terrain, PRB design, construction, and maintenance are discussed along with recommendations for designing PRBs in other remote and cold region environments. [ABSTRACT FROM AUTHOR]

Over the course of three years, several surface permeable reactive barriers were designed and constructed to deal with leftover site contamination at a site located on the summit of Resolution Island, Nunavut, just southeast of Baffin Island at 61° 35′N and 60° 40′W. The site was part of a North American military defense system established in the 1950s that became heavily contaminated with polychlorinated biphenyls (PCBs) during and subsequent to, its operational years. Each of the three barrier designs has a different configuration, to meet the needs of the targeted remediation area, based on their unique contaminant histories. Modifications were made to the barrier designs based on both field observations and laboratory results. The comparison of field and laboratory results indicated that areas with higher concentrations of PCB contamination behaved differently than areas with lower concentrations of PCB contaminated soil. Previous laboratory studies only partially replicated field observations and results. It had previously been hypothesized that particle retention was the most important factor in trapping and capturing PCBs. However, rinsed filter samples from the field indicated that partitioning of PCBs between contaminated soil and granular activated carbon (GAC) filter particles were occurring at levels of 62 ± 11%, suggesting that sequestration of the PCBs from the environment should be a primary focus of the barrier. This sequestration requires both particle retention (within the granular sorptive filters) as well as maintained contact time between particles for sorption processes to proceed. This mechanism – partitioning of PCB to GAC – was more important in areas with higher PCB concentration. These results suggest that it may be possible to tailor future barrier designs to their unique site histories and locations. [Copyright &y& Elsevier]

The site BAF-5 is located on the summit of Resolution Island, Nunavut, just southeast of Baffin Island at 61° 35′N and 60° 40′W. The site was part of a North American military defense system established in the 1950s that became heavily contaminated with PCBs during and subsequent, its operational years. Remediation through excavation of the PCB contaminated soil at Resolution Island began in 1999 and at its completion in 2006 approximately 5 tonnes of pure PCBs in approximately 20,000 m3 of soil were remediated. Remediation strategies were based on both quantity of soil and level of contamination in the soil. Excavation removed 96% of the PCB contaminated soil on site. In 2003, a surface funnel-and-gate permeable reactive barrier was design and constructed to treat the remaining contamination left in rock crevices and inaccessible areas of the site. Excavation had destabilized contaminated soil in the area, enabling contaminant migration through erosion and runoff pathways. The barrier was designed to maximize sedimentation through settling ponds. This bulk removal enabled the treatment of highly contaminated fines and water through a permeable gate. The increased sediment loading during excavation required both modifications to the funnel and a shift to a more permeable, granular system. Granulated activated charcoal was chosen for its ability to both act as a particle retention filter and adsorptive filter. The reduction in mass of PCB and volume of soils trapped by the funnel of the barrier indicate that soils are re-stabilizing. In 2007, nonwoven geotextiles were re-introduced back into the filtration system as fine filtering could be achieved without clogging. Monitoring sites downstream indicate that the barrier system is effective. This paper describes the field progress of PCB remediation at Resolution Island. [Copyright &y& Elsevier]