See: Tier 1 Spill.
Oil spills get classified into the three categories. The least destructive receive the distinction of "tier 1." Those are localized and can usually be taken care of by the oil producer itself.
The worst spills get the label "tier 3." These are the ones that might wipe out entire marine species or force an entire village of Kazakhstanis to move to a different part of the country. Or the world.
Tier 2 sits in the middle. Not a "don't worry about the situation, we'll handle it" kind of deal. But also not an event that will get mentioned in general history books. It's a big, destructive oil spill that requires the authorities to get involved. But it's generally contained, at least compared to a tier 3 horror show.
