Spill Containment Calculator: EPA SPCC 40 CFR 112 Sizing

How It Works

1. Enter Tank Data

   Input the number of tanks, their individual capacities in gallons, and physical dimensions (diameter and height). The calculator identifies the largest tank for the 110% rule.

2. Calculate Base Containment Volume

   The required volume is 110% of the largest single tank capacity. Some states require 110% of all tanks combined, so check local regulations.

3. Add Precipitation and Displacement

   Enter the 25-year/24-hour rainfall depth for your location from NOAA Atlas 14. The calculator adds precipitation volume over the containment area and subtracts volume displaced by tank foundations and piping.

4. Review Berm Dimensions

   See the required containment area, effective volume after displacement and precipitation, and recommended berm height. Verify the design meets the 110% rule with adequate freeboard above the calculated liquid level.

Built For

• Environmental managers sizing new secondary containment berms for bulk diesel and lube oil tanks at industrial facilities
• Plant engineers verifying existing containment still meets 110% after adding a new tank inside the same bermed area
• SPCC plan preparers calculating exact berm heights and volumes for EPA plan documentation and PE certification
• Fuel farm operators at airports and military bases sizing containment for multiple jet fuel and AVGAS tanks
• Agricultural cooperatives designing containment for above-ground bulk fertilizer and herbicide storage tanks
• Construction site managers sizing temporary containment berms for diesel fuel tanks and generator day tanks
• Environmental consultants auditing existing containment volumes against NOAA Atlas 14 precipitation data for the site location

Features & Capabilities

110% Largest Tank Rule

Calculates the minimum containment volume as 110% of the largest single tank capacity per EPA 40 CFR 112. Flags when containment falls short.

Precipitation Volume

Adds the 25-year/24-hour rainfall volume over the containment footprint. Enter rainfall depth from NOAA Atlas 14 for your location.

Tank Displacement Subtraction

Subtracts the volume occupied by tanks, pedestals, and piping inside the berm to calculate net available containment volume.

Berm Height Output

Calculates the required berm wall height given the containment footprint area. Shows freeboard above the calculated maximum liquid level.

Multi-Tank Support

Handles containment areas with multiple tanks of different sizes. Identifies the controlling tank and computes combined displacement.

PDF Export

Export containment calculations as a branded PDF for SPCC plans, PE review submittals, and regulatory inspection files.

Assumptions

• Minimum containment volume is 110% of the largest single tank capacity per EPA 40 CFR 112.7(c)
• Precipitation allowance uses the 25-year, 24-hour rainfall event depth from NOAA Atlas 14 for the facility location
• Tank displacement volume subtracted from gross containment volume based on entered tank physical dimensions
• Containment area is assumed rectangular with vertical berm walls — sloped or irregular berms require adjusted geometry
• Oil includes petroleum products, vegetable oils, animal fats, and synthetic oils per EPA 40 CFR 112 definitions
• SPCC plan threshold: facility stores more than 1,320 gallons aboveground (no single container under 55 gallons) with reasonable expectation of discharge to navigable waters

Limitations

• Does not determine whether your facility meets the SPCC threshold — consult EPA 40 CFR 112.1 applicability criteria
• State regulations may require containment exceeding the federal 110% rule (some states require 110% of total aggregate volume)
• Does not account for piping, transfer hose, pump, or manifold failures outside the bermed area — these may require separate containment
• Precipitation accumulation from storms smaller than the 25-year event can reduce available containment if rainwater is not drained regularly
• Does not evaluate containment material compatibility with the stored product (chemical resistance of liners, coatings, and concrete)
• Freeboard above calculated liquid level is not automatically included — design should add 6 inches minimum above the calculated berm height
• Underground storage tank (UST) containment requirements under 40 CFR 280 are separate from SPCC and are not addressed

References

• EPA 40 CFR 112 — Oil Pollution Prevention (SPCC Rule: secondary containment, facility response plans)
• EPA SPCC Guidance for Regional Inspectors — Chapters 2 and 4 (containment sizing and qualified facility provisions)
• NOAA Atlas 14 — Precipitation-Frequency Atlas of the United States (hdsc.nws.noaa.gov for 25-year/24-hour rainfall depths)
• API Standard 650 — Welded Tanks for Oil Storage (tank dimensions and foundation requirements)
• NFPA 30 — Flammable and Combustible Liquids Code (secondary containment for flammable liquid storage)
• EPA Publication 832-F-02-019 — Overview of SPCC Requirements for Facilities

Frequently Asked Questions