Kewalo Basin has had several oil spills from fishing vessels and has its share of mystery spills too. Shore based activities from non-maritime sources are the major cause of spills on Oahu. Shoreline spills, although numerous, are generally just sheens. They typically occur from street or parking runoff which gets flushed by rainwater into a storm drain and then to the waterway. The second chart only graphs spills from known maritime sources.
Public vessels have a lot of oil spills, but they average less than one gallon.
U.S. fishing vessels are a major maritime source for oil spills resulting in the largest impact in Oahu. MAUI Passenger vessels and recreational boaters operating out of Lahaina are the biggest polluters on Maui. Most of the mystery spills also occur in this harbor. Operators of passenger vessels are licensed by the Coast Guard and are familiar with spill reporting requirements. The number of spills associated with passenger vessels should be expected to be higher than other sources.