A removal action may be performed at any stage of the response process, if the Department determines that there is a release or substantial threat of release of hazardous substances into the environment that should be removed, stabilized, or otherwise mitigated. In an emergency, the Department may perform a removal action immediately. If the Department determines that time allows, before beginning a removal action the Department shall make an effort to identify the responsible persons and determine whether those persons will perform the removal action properly and in a timely manner. If a person other than the Department performs the removal, the Department may perform a managerial or oversight function and has the authority to approve, disapprove, or alter the manner in which the removal is being conducted. Unless the Department determines that a removal action will be done properly and in a timely manner by a responsible person, the Department may perform the removal. Extent of Removal. Removal is terminated when the Department determines that the threat of release no longer exists or is otherwise mitigated. If the Department determines that the removal action does not fully address the threat and the release may require further remedial action, there shall be an orderly transition from removal to remedial response activities.