A method is disclosed for constructing, verifying, and maintaining underground vaults that isolate and contain radioactive burial sites. The method employs a buoyant lift technique to isolate a block of soil containing the contaminates from the surrounding soil. An impermeable synthetic liner is embedded in the vault to enhance the integrity of the system. The integrity of the vault is monitored by a system of sensors placed both inside and outside of the sealed vault. The method eliminates the need to excavate or drill in the contaminated areas.