This guide discusses the significance of oil-spillage regulations and their applicability to electric supply substations; identifies the sources of oil spills; discusses typical designs and methods for dealing with oil containment and control of oil spills; and provides guidelines for preparation of a typical Spill Prevention Control and Countermeasure (SPCC) plan. This guide excludes polychlorinated biphenyl (PCB) handling and disposal considerations. It is not the intent of this guide to interpret the applicability of the governmental regulations or the oil-containment systems presented. Such interpretation is left to each individual user. The guide is intended to identify concerns, offer solutions, and let users make their own evaluations. This guide applies only to insulating oil containing less than 50 ppm of PCB, which is considered to be non-PCB oil. Non-PCB oils have a PCB content that has been designated by the U.S. Environmental Protection Agency (EPA) as nonhazardous to the public, and they are not deemed to be toxic substances. While the effectiveness of the containment methods described in this guide is generally not affected by the PCB content of the oil, the regulations governing cleanup and handling of oil spills containing PCB are much more restrictive.