Containment, control and mitigation of oil spills are a concern for owners and operators of electric supply substations. The environmental impact of oil spills and their mitigation is regulated by governmental agencies, necessitating increased attention in substations to the need for secondary oil containment. Beyond the threat to the environment, mitigation costs associated with oil spills continue to escalate, and the adverse community response to any spill is becoming increasingly unacceptable. This guide identifies some governmental regulations, sources of oil spills, and typical methods and plans to contain, control and mitigate them. (Definition: "Oil" includes mineral oil and alternative insulating fluids)