A study by the Pacific States/British Columbia Oil Spill Task Force (2002) found areas of higher grounding or collision risk 25 nautical miles from land along the entire West Coast, except (for Canadian waters) off northwestern BC, where the high risk area extended to 100 NM offshore.
Ces marées peuvent être causées par des collisions, des échouages ou des rejets illégaux d’eau de cale polluée.