Containment requirements for oil-filled transformers focus on preventing oil spills and managing leaks to protect the environment and ensure safety. Facilities must implement secondary containment systems, such as dikes or bunding, with sufficient capacity to hold at least 110% of the transformer’s oil volume. This containment area must be waterproof and constructed with materials resistant to chemical degradation from the oil. Additionally, regular inspections and maintenance of containment structures are vital to ensure their integrity. Proper drainage systems must also be established to prevent water accumulation in containment areas. These measures are essential for compliance with environmental regulations and minimizing risks associated with oil-filled transformer containment.