33 CFR § 401.73 - Cleaning tanks - hazardous cargo vessels.
(a) Cleaning and gas freeing of tanks shall not take place:
(1) In a canal or a lock;
(2) In an area that is not clear of other vessels or structures; and
(3) Before gas freeing and tank cleaning has been reported to the nearest Seaway station.
(b) Hot work permission. Before any hot work, defined as any work that uses flame or that can produce a source of ignition, cutting or welding, is carried out by any vessel on any designated St. Lawrence Seaway Management Corporation (SLSMC) approach walls or wharfs, a written request must be sent to the SLSMC, preferably 24 hours prior to the vessel's arrival on SLSMC approach walls or wharfs. The hot work shall not commence until approval is obtained from an SLSMC Traffic Control Center.
(c) Special requirements for tankers performing hot work. Prior to arriving at any SLSMC designated approach wall or wharf, a tanker must be gas free or have tanks inerted. The gas-free certificate must be sent to the SLSMC Traffic Control Center in order to obtain clearance for the vessel to commence hot work.