Abstract: | Permeable reactive barriers made of zero‐valent iron (ZVI PRBs) have become a prominent remediation technology in addressing groundwater contamination by chlorinated solvents. Many ZVI PRBs have been installed across the United States, some as research projects, some at the pilot scale, and many at full scale. As a passive and in situ remediation technology, ZVI PRBs have many attractive features and advantages over other approaches to groundwater remediation. Ten ZVI PRBs installed in California were evaluated for their performance. Of those ten, three are discussed in greater detail to illustrate the complexities that arise when quantifying the performance of ZVI PRBs, and to provide comment on the national debate concerning the downgradient effects of source‐zone removal or treatment on plumes of contaminated groundwater. © 2009 Wiley Periodicals, Inc. |