The US Permeable reactive barrier (PRB) guidance provides a more extended definition, which includes injection zones. Although the PRB concept was first developed in North America in the early 1990s, European projects have also played an important part in the development of the technology. The total number of active European projects has reached around 50 by 2014, of which more than 25 are full scale. In Europe, drain-and-gate or “Efficiently Controllable” PRBs, where the groundwater flow is directed and controlled by drainage, pipes, or even by active pumping are now common. A groundwater contamination by chlorinated volatile organic carbons at Edenkoben was attributed to the former use of chlorinated hydrocarbon solvents for production processes on-site. Several hot spots were found on the property, partly situated below some buildings. Organic contaminants were removed with very high efficiency by the PRB biofiltration system.