When abandoning an underground tank, which method must be avoided to prevent safety hazards?

When abandoning an underground tank, pulling a vacuum is a method that must be avoided due to the inherent safety hazards it presents. This technique can create a situation where the tank could collapse, especially if it is not properly supported or if there is not enough structural integrity in the surrounding soil. Additionally, pulling a vacuum could potentially lead to the release of hazardous vapors or materials that may be trapped inside the tank, posing risks to both the environment and human health. Therefore, safe abandonment practices favor methods that ensure the tank is properly filled or removed, rather than those that might destabilize the tank structure or create dangerous conditions during the abandonment process.