Are on-site contractors responsible for EHSs brought on-site?

For Section 302 purposes, if a contractor brings an extremely hazardous substance (EHS) on-site to a facility over the threshold planning quantity, is the owner/operator of the facility or the contractor required to make the notification to the LEPC? 

For Section 304 purposes, if a contractor bursts a tank at a facility and causes a release of reportable quantity (RQ) of an EHS, should the contractor or the owner/operator of the facility notify the community emergency coordinator?

For both Sections 302 and 304, a contractor could be considered an operator of the facility or of a portion of the facility depending on if he/she has enough authority.  The definition of operator is not defined by statue or in the regulations.  If the contractor is considered an "operator," he or she could be held liable for not making the required notifications under Sections 302 or 304.  If no notification is made under sections 302 and 304, owner and operator will be held liable.