If the secretary makes a written declaration that actions must be undertaken immediately or within a time too short to allow full compliance with SEPA requirements; and that such actions are necessary to avoid an imminent threat to public health or safety, or to prevent an imminent danger to public or private property, or to prevent an imminent threat of serious environmental degradation; then such actions may be undertaken without complying with SEPA requirements: Provided, That the department is the lead agency for such actions.