Why is transformer oil containment required in substations?

Containment is required to prevent leaked oil from reaching soil, drains, or water, and to reduce fire spread and cleanup costs. Even small leaks can cause environmental violations and corrosion hazards, while major failures can release large volumes rapidly. Substations implement containment using bund walls, lined pits, sumps with oil water separators, drain valves locked in normal position, and absorbent or boom equipment for emergency response. Designs often include fire barriers and routing of runoff to collection points, ensuring compliance with environmental and safety regulations.