What are the key requirements for transformer oil containment design?

Containment design aims to prevent oil reaching soil or water during leaks, failures, or fire. Key requirements include a bunded area or pit sized for at least the full oil volume (often plus rain allowance), impermeable liners, drainage control with oil water separators, fire safe layouts, and easy access for cleanup. Substations often use gravel layers to reduce pooling and support fire suppression, plus monitoring for sump levels. Local environmental rules determine exact capacity, materials, and reporting obligations.