What is an Underground Fuel Tank (UST)?
An underground fuel storage tank (UST) is a subterranean containment vessel buried below ground level to store petroleum products at commercial service stations and industrial facilities. USTs save surface space and can help reduce exposure to aboveground hazards, but they require appropriate leak detection and regulatory controls.
For federal UST regulations, refer to the EPA Learn About Underground Storage Tanks.
Underground Fuel Tank (UST) Formulas
Cylindrical UST Volume Formula:
Volume = π × r² × Length + Head Caps Volume
95% Max Fill Safety Limit:
Max UST Fill = Gross Volume × 0.95
How to Calculate UST Storage Volume
- Record Internal Diameter: Measure inside tank diameter.
- Record Tank Length: Measure horizontal shell length.
- Calculate Cylinder & Dished End Volume: Sum main cylinder body and end cap volumes.
- Convert to US Gallons / Litres: Convert cubic measurement to fuel storage units.
UST Numerical Walkthrough
For a standard 10,000 Gallon Underground Fuel Storage Tank measuring 8 ft diameter and 27 ft length:
Total Volume = 3.14159 × (4)² × 27 = 1,357.17 ft³Gross Gallons = 1,357.17 × 7.48052 ≈ 10,152.34 US Gallons
Standard UST Capacity & Dimensions Chart
| UST Capacity | Dimensions (Diameter × Length) | Gallons | Litres |
|---|---|---|---|
| 5,000 Gal UST | 8 ft × 13.5 ft (2.44m × 4.11m) | 5,000 gal | 18,927 L |
| 10,000 Gal UST | 8 ft × 27.0 ft (2.44m × 8.23m) | 10,000 gal | 37,854 L |
| 12,000 Gal UST | 9 ft × 25.0 ft (2.74m × 7.62m) | 12,000 gal | 45,425 L |
| 15,000 Gal UST | 10 ft × 25.5 ft (3.05m × 7.77m) | 15,000 gal | 56,781 L |
| 20,000 Gal UST | 10 ft × 34.0 ft (3.05m × 10.36m) | 20,000 gal | 75,708 L |
EPA Leak Detection & Interstitial Monitoring
Underground storage tanks require double-walled construction with interstitial vacuum sensors and automatic tank gauging (ATG) to detect leaks before soil contamination occurs.
Underground Tank Sizing & Soil Pressure Safety
Underground fuel storage tanks must resist hydrostatic pressure from elevated groundwater tables as well as soil overburden loads. When calculating storage capacity, ensure that tank anchors, ballast slabs, and backfill specifications meet localized environmental containment standards.