DEFINITION of 'Tier 1 Spill'
One of the three categorized levels of oil spills. Tier 1 spills are the most mild, causing localized damage usually near the company's own facilities. In most cases, this type of spill occurs as a result of the company's own activities.
BREAKING DOWN 'Tier 1 Spill'
Oil companies are usually expected to clean up their own Tier 1 spills. They must therefore maintain an appropriate level of preparedness for this event at all times. The International Petroleum Industry Environmental Conservation Association has defined the three tiers according to various characteristics.