7 Whenever
visible traces of oil are observed on or below the surface of the
water in the immediate vicinity of a ship or its wake, the Governments
of Parties to the present Convention should, to the extent they are
reasonably able to do so, promptly investigate the facts bearing on
the issue of whether there has been a violation of the provisions
of this regulation. The investigation should include, in particular,
the wind and sea conditions, the track and speed of the ship, other
possible sources of the visible traces in the vicinity, and any relevant
oil discharge records.
8 No
discharge into the sea shall contain chemicals or other substances
in quantities or concentrations which are hazardous to the marine
environment or chemicals or other substances introduced for the purpose
of circumventing the conditions of discharge specified in this regulation.
9 The
oil residues which cannot be discharged into the sea in compliance
with paragraphs 1 and 3 of this regulation shall be retained on board
for subsequent discharge to reception facilities.