The environmental risk of an oil spill is defined as the product of:

1. The probability of occurrence of the spill, and
2. The environmental impact of the spill.

At SL Ross most contingency planning projects for specific areas or specific petroleum activities begin with an oil spill risk assessment of the situation. This means identification of the major sources of spills in the study area, an assessment of spill probability, and an assessment of the potential impact of spills from these sources. The goal is to identify "worst-case" and average-size spills that should be the focus of contingency planning and response preparedness.