What process involves creating a defined area to contain a hazardous materials release?

The process that involves creating a defined area to contain a hazardous materials release is containment. Containment is crucial during a hazardous materials spill as it prevents the spread of contaminants to surrounding areas, protecting both the environment and human health. This is typically accomplished by using physical barriers such as dikes, berms, or absorbent materials to isolate the hazardous substance.

Retention, while related, more specifically refers to the act of holding or storing hazardous materials in a designated area, rather than creating a barrier around a release to prevent further dispersion. Therefore, while both retention and containment involve managing hazardous materials, containment directly addresses the immediate need to control and isolate a release.