Under the EPA’s SPCC (Spill Prevention, Control, and Countermeasure) rule, facilities with more than 1,320 gallons of aboveground oil storage capacity (counting containers of 55 gallons or more) that could reasonably discharge to waterways need secondary containment and a spill plan. Other rules, fire codes, and insurers may also call for containment of non-oil chemistries. This is general information, not compliance advice; here’s the math and the practical setup.
The 110% rule of thumb
SPCC requires containment sized for the full capacity of the largest container plus freeboard for precipitation if outdoors uncovered; sizing to 110% of the largest container is the common rule of thumb. For a single 330-gallon tote, that’s 363 gallons of containment. For four totes stored together, it’s still sized to the largest single tote, not the aggregate — the assumption is that all totes won’t fail simultaneously. Some other regulations use different formulas, so confirm which rules apply to you.
Precipitation allowance
If your containment is outdoors and uncovered, you need to add freeboard for precipitation, commonly sized to a design storm such as the 25-year, 24-hour event (roughly 4 inches in the Cleveland area; check NOAA data for your site). Each inch of rain on 25 square feet of pan adds about 15.6 gallons, so 4 inches is roughly 60 gallons per 25 square feet. Most operations cover the containment or add drainage with manual valves that stay closed unless inspecting.
Pan options
Three common pan types:
- Poly secondary containment pallet: Available in single-tote and two-tote sizes. Drop-in, no construction required. Drains via a removable plug. Standard for small-shop installations.
- Concrete-curbed area: Permanent installation, requires a sealed concrete floor with a curb or berm. Cost scales with the area and site work, so get a contractor’s quote. Required for many state-permitted bulk storage installations.
- Modular plastic berm: Lay-flat berms with an internal liner, sized to the footprint. Lower profile, easier to install, but punctures more easily than rigid pans.
Common errors
Sizing to total inventory instead of largest container: usually overspecs, sometimes underspecs depending on container sizes. Read the actual rule.
Forgetting precipitation: outdoor uncovered installations almost always fail their first inspection on this.
Drain valves left open: the containment is useless if the drain is permanently open. Keep it closed (locking it is good practice), with a manual procedure to drain only after inspecting the water.
Containment under stacked totes: a containment pan rated for one tote will overflow if a stacked top tote fails. If you stack, size containment for the total stack’s top container.
SPCC plan
For oil storage at or above the SPCC thresholds, you need a written SPCC plan, certified by a PE for facilities above certain thresholds. The plan covers spill response, training, inspections, and recordkeeping. An environmental consultant or PE familiar with Ohio facilities is the right person to prepare it.
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