The year 2011 marked the 20th year anniversary of the first pilot testing of the permeable reactive barrier (PRB) as an in situ groundwater remedy by University of Waterloo researchers at the Canadian Forces Base Borden site in Ontario, Canada. Although exact wording has morphed over the past two decades, the generally accepted definition of a PRB, as modified from Interstate Technology and Regulatory Council is an engineered, continuous, in situ permeable treatment zone designed to intercept and remediate a contaminant plume. Modern sustainable hydraulic enhancements may include the use of solar or wind-driven, low-rate groundwater pumps, or passive-siphon action to further control and route affected groundwater through a PRB. Aside from monitored natural attenuation or intrinsic remediation strategies, there may be no other primary groundwater remediation method that conveys the concept of a green and sustainable system as well as the PRB.