Performance monitoring of a Permeable Reactive Barrier at the Somersworth, NH Landfill Superfund Site, submitted for publication in the ACS volume Innovative Strategies for the Remediation of Chlorinated Solvents and DNAPLs in the Subsurface

Abstract: Over a six-month period, the performance of a pilot-scale PRB at the Somersworth, NH Landfill Superfund Site was evaluated. The 21-ft long PRB was installed in November 1999 to test a construction technique that uses a biodegradable polymer slurry to support an open excavation while a granular iron/sand mixture was placed into the subsurface. Criteria used to assess the PRB’s performance included (1) hydraulic testing to evaluate potential fluid viscosity effects related to the use of the biopolymer, (2) monitoring of VOCs, groundwater parameters (pH, DO, ORP, specific conductance) and inorganic parameters (including metals, major ions and nutrients), (3) microbial characterization of groundwater, (4) reactivity testing of cored iron material, and (5) advanced surface analysis of cored iron material. As permeable reactive barriers (PRBs) containing zero-valent iron become more widely used to remediate contaminated groundwaters, there remains uncertainty in the prediction of their long-term performance. While a number of accelerated aging laboratory and pilot-scale tests have not indicated any significant performance issues caused by the build-up of surface precipitates or bio-fouling, there has been relatively little performance dat