Permeable reactive barriers (PRBs) are alternatives to common active groundwater remediation technologies including those based on pump and treat [1-5]. PRB is a passive in situ groundwater remediation technique that avoids several inherent technical drawbacks of active systems a priori. A PRB is defined as an in situ method for remediating contaminated groundwater which combines a passive chemical or biological treatment zone with subsurface fluid flow management [6]. PRBs that were first installed in the United States in the early 1990s used zero-valent iron (e.g., elementary iron). Due to the inability of iron (Fe) to efficiently remediate polycyclic aromatic hydrocarbons (PAHs), for the past 15 years, activated carbon has been used in PRBs as an additional adsorbent for PAHs and other related organic compounds [7,8].