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How this calculator works
The SPCC calculator checks your oil storage against the EPA thresholds in 40 CFR 112.1:
- Does the rule apply? SPCC applies only where a discharge could reasonably reach navigable waters or adjoining shorelines, so the calculator asks that first.
- Inventory. You list each oil container. Only containers of 55 gallons or more count. Aboveground capacity is added up and compared with 1,320 gallons; completely buried capacity is compared with 42,000 gallons. Exempt containers, such as USTs regulated under 40 CFR 280/281, motive-power containers and residential heating oil, are shown but not counted.
- Result. SPCC applies when aggregate aboveground capacity is more than 1,320 gallons, or buried capacity is more than 42,000 gallons, and a discharge could reach navigable waters. Farms use the separate thresholds set by the 2014 WRRDA amendments.
- Plan type. With 10,000 gallons or less aboveground and a clean 3-year spill history, you are a Qualified Facility and can self-certify: Tier I if no container exceeds 5,000 gallons, otherwise Tier II. Other facilities need a Professional Engineer to certify the plan.
- Containment estimate. The rule requires secondary containment for the largest container plus freeboard for precipitation. The calculator uses 110% of the largest container as a common rule of thumb.
SPCC is a plan requirement, not a reporting requirement. Review and evaluate the plan at least every 5 years. The calculator is a screening tool; confirm the result with EPA guidance or a qualified professional.