Most of these reported incidents are minor in nature, for example a loose hose clamp causes a "spill" of one gallon of antifreeze. The oil companies and their support industries are still obligated to report these under current EPA regulations. I remember one incident that took place on the north slope. A seawater treatment plant spilled 250 gallons of seawater on the ocean ice. It was still reported as a spill, and characterized as a contaminant. I have a hard time understanding the reasoning in that but I'm certain it helped someone in the EPA justify their job/funding.
I have no doubt of that. But -- a couple gallons here, a couple gallons there, and eventually it could accumulate into a problem.