A vertical engineered barrier, or “VEB,” is a wall built below ground to control the flow of groundwater. VEBs may divert the flow direction of contaminated groundwater to keep it from reaching drinking water wells, wetlands or streams. They also may contain and isolate contaminated soil and groundwater to keep them from mixing with clean groundwater. VEBs differ from permeable reactive barriers in that they do not clean up contaminated groundwater. VEBs are often used together with cleanup methods that treat the isolated soil or groundwater.