Technical Glossary & Regulatory Definitions

An aboveground storage tank (AST) is a stationary, surface-installed container engineered under UL 142 or UL 2085 standards to store petroleum fluids, chemicals, or biofuels, offering rapid visual leak inspections and lower installation costs compared to subsurface vessels.

An underground storage tank (UST) is a subsurface containment vessel governed by EPA 40 CFR Part 280 and UL 58 standards, built with double-wall steel construction and cathodic or composite corrosion protection to conserve surface acreage and prevent groundwater contamination.

UL 142 is the Underwriters Laboratories standard governing steel aboveground tanks for flammable and combustible liquids, establishing structural wall thicknesses, normal and emergency venting requirements, and atmospheric leak tightness for single- and double-wall installations.

UL 2085 is the standard for protected aboveground tanks, requiring an insulated double-wall steel vessel that delivers a two-hour liquid pool fire rating, non-welded ballistic impact resistance, and heavy vehicular impact resistance under NFPA 30 and 30A codes.

Fireguard® is a Steel Tank Institute (STI) licensed, UL 2085 listed thermally insulated double-wall aboveground storage tank featuring lightweight monolithic thermal insulation between walls that restricts temperature rise during a two-hour catastrophic fire.

Flameshield® is a Steel Tank Institute (STI) manufactured double-wall aboveground tank tested under UL 142 with a 2-hour fire endurance rating, providing 110% secondary containment without requiring heavy insulating concrete slurry.

UL 58 is the standard for steel underground tanks for flammable and combustible liquids, regulating welding integrity, head dishing, internal vacuum structural capacity, and secondary containment shell geometry under dynamic subterranean soil overburden.

STI-P3® is a Steel Tank Institute standard for underground steel tanks incorporating three levels of corrosion defense: heavy-duty dielectric coating, electrical isolation bushings at all pipe connections, and pre-engineered sacrificial zinc or magnesium anodes.

ACT-100® and ACT-100-U® designate composite underground steel tanks factory-clad with 100 mils of glass-fiber-reinforced polyester or polyurethane resin, eliminating the need for underground sacrificial anodes while retaining steel structural strength.

EPA Spill Prevention, Control, and Countermeasure (SPCC) is a federal environmental regulation requiring commercial facilities storing over 1,320 gallons of petroleum to implement certified secondary containment, monthly visual inspections, and integrity testing.

An oil-water separator is an engineered wastewater treatment vessel utilizing oleophilic inclined plate coalescing media packs to accelerate gravitational separation of free hydrocarbons from stormwater, discharging effluent water containing less than 10 ppm hydrocarbons.

TCEQ Title 30 Texas Administrative Code Chapter 334 regulates underground and aboveground storage tanks in Texas, mandating certified Stage I/II vapor recovery, continuous release detection monitoring, and direct filing of environmental compliance reports.

The interstitial space is the hollow annular cavity between primary and secondary containment walls in a double-wall tank, plumbed with vacuum, pressure, or electronic sensors to detect leaks before product escapes into the environment.

A thief hatch is a spring-loaded pressure-vacuum relief access door mounted atop oilfield production stock tanks, allowing manual fluid sampling (gauging) while preventing volatile vapor loss and atmospheric moisture ingress.

NFPA 30 is the Flammable and Combustible Liquids Code, and NFPA 30A is the Motor Fuel Dispensing Facilities Code, both defining mandatory setback distances, emergency venting calculations, and spill control boundaries for fueling facilities.