What is the SPCC Rule?
The SPCC rule, codified in 40 CFR Part 112, is designed to prevent oil discharges into navigable waters of the United States. It applies to facilities that drill, produce, store, refine, or consume oil and oil products.
Under the SPCC rule, "oil" is defined broadly. It includes petroleum, fuel oil, sludge, synthetic oils, mineral oils, and even animal or vegetable oils.
Applicability: The 1,320-Gallon Threshold
A facility is subject to the SPCC rule if its total aggregate aboveground oil storage capacity is greater than 1,320 gallons (or completely buried capacity exceeds 42,000 gallons).
When calculating your total site capacity, you only count containers with a capacity of 55 gallons or greater. This includes drums, totes, bulk storage tanks, and oil-filled operating equipment like transformers. Crucially, the rule looks at container capacity, not the actual volume of oil currently stored.
General vs. Sized Secondary Containment
The rule distinguishes between general containment and specific (sized) containment. General containment is required for all areas where oil is handled, such as loading zones, and can consist of active measures like spill kits or temporary berms designed to address the most likely discharge.
Specific, or sized, secondary containment is required for bulk storage containers. These passive structures (like concrete berms or double-walled tanks) must be large enough to hold the entire contents of the largest single tank within the containment area.
How to Calculate Sized Secondary Containment Volume
For bulk storage, the secondary containment must be sized to hold 100% of the capacity of the largest single container within it, plus "sufficient freeboard" to allow for precipitation if the area is exposed to weather.
Calculation Rule: Total Required Volume = 100% of Largest Tank + Precipitation Allowance. The EPA does not mandate a specific freeboard amount, but industry standard often uses the 25-year, 24-hour storm event for the region, or a rule of thumb of 110% of the tank's capacity. For example, a 1,000-gallon tank outdoors would typically require a containment basin of at least 1,100 gallons.
Frequently asked questions
Do empty tanks count toward the 1,320-gallon SPCC threshold?
Yes. If an empty tank is 55 gallons or larger and has not been permanently closed (e.g., cleaned, disconnected, and marked as closed), its shell capacity counts toward your total threshold.
Can double-walled tanks serve as secondary containment?
Yes, shop-built double-walled tanks inherently meet the requirement for sized secondary containment, provided they are properly maintained and protected from vehicular traffic.
Who can certify an SPCC Plan?
An SPCC Plan generally must be certified by a licensed Professional Engineer (PE). However, qualified facilities that meet specific criteria (less than 10,000 gallons total capacity and no recent spills) can self-certify.
What defines sufficient freeboard?
The EPA deliberately leaves 'sufficient freeboard' undefined to allow for regional climate differences. Engineers typically calculate the volume based on local precipitation data for a 25-year, 24-hour storm.