Britannica Sources used in this answer

How can cutoff walls contain groundwater pollution at a hazardous-waste site?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

radioactive waste — hazardous-waste management Employees loading transuranic waste into a shipping container at Vallecitos Nuclear Center, a nuclear research facility in Alameda county, California.

Cutoff walls are used in hazardous-waste management as a method of full containment to prevent the lateral migration of contaminated groundwater.1

To effectively contain pollution, these walls are constructed around the perimeter of a site, extending deep enough to reach a natural layer of impervious soil or rock. This configuration creates a vertical barrier that, when combined with the underlying impervious layer, prevents water from flowing into or out of the contaminated area.1

The construction process involves the following steps:
* Trenching: Trenches are excavated around the site without disturbing the waste material.1
* Stabilization: The trenches are filled with a bentonite clay slurry to prevent collapse during the excavation process.1
* Sealing: The trenches are backfilled with a mixture of soil and cement that solidifies into an impermeable barrier.1

By blocking the lateral flow of groundwater, cutoff walls help isolate the waste and minimize the risk of environmental contamination.1