The SPCC Plan must address Secondary Containment for all applicable oil product storage tanks. Generally, the size requirement of the containment must be sufficient to hold the total volume of the largest tank plus “freeboard” excluding the area occupied by all tanks, separators and equipment other than the largest vessel.
There are two acceptable means of applying the necessary freeboard.
- The 25 year, 24 Hour Rainfall Events for that particular location
2. 110% of the largest oil vessel.
The following chart is an example of a Spillco Secondary Containment calculations that are certified by a Professional Engineer for an oil production facility. The exact method included in the SPCC plan will vary with each specific facility. Properly designed double walled tanks are generally self-contained and require no berm, etc.