Interest in site-specific evaluations of permeable reactive barrier (PRB) performance is high, particularly with regard to issues relating to media longevity and hydraulic performance. This chapter provides an update on the contaminant removal efficiency of this PRB after 14 years of operation. In 1999, a pilot-scale injection of sodium dithionite was conducted to evaluate the response of the source-zone hexavalent chromium. The evaluation of the Elizabeth City PRB consisted of detailed groundwater sampling, hydrologic characterization, and core collection and solid-phase studies. A detailed monitoring network of over 130 subsurface sampling points was installed in November 1996 to provide detailed information on spatial and temporal changes in pore water geochemistry and hydrology. The highest concentrations of chromium have been observed over the depth interval from 4 to 5 m below ground surface. The Elizabeth City PRB is one example that has shown positive results for the treatment of hexavalent chromium and trichloroethene.