Why is secondary containment needed for oil filled transformers?

Secondary containment is needed to prevent leaked oil from reaching soil, drains, or water and to reduce fire and cleanup risk. Even minor seepage can create environmental violations and corrosion or slip hazards, while a major internal fault can release a large oil volume quickly. Containment is implemented with bund walls, lined pits, sumps, and oil water separators sized for worst case spill scenarios. It also supports compliant stormwater management and faster emergency response.