EPA added new operation and maintenance requirements and addressed UST systems deferred in the 1988 UST regulation. The changes: Added secondary containment requirements for new and replaced tanks and piping Added operator training requirements Added periodic operation and maintenance requirements for UST systems Added requirements to ensure UST system compatibility before storing certain biofuel blends Removed past deferrals for emergency generator tanks, field constructed tanks, and airport hydrant systems Updated codes of practice Made editorial and technical corrections. Tank types Underground storage tanks fall into four different types: Steel/aluminum tanks, made by manufacturers in most states and conforming to standards set by the Steel Tank Institute. Composite overwrapped, a metal tank (aluminum/steel) with filament windings like glass fiber/aramid or carbon fiber or a plastic compound around the metal cylinder for corrosion protection and to form an interstitial space. Tanks made from composite material, fiberglass/aramid or carbon fiber with a metal liner (aluminum or steel). See metal matrix composite. Composite tanks such as carbon fiber with a polymer liner (thermoplastic). See rotational molding and fibre-reinforced plastic (FRP). Underground storage tanks for water are traditionally called cisterns and are usually constructed from bricks and mortar or concrete. Petroleum underground storage tanks Petroleum USTs are used throughout North America at automobile filling stations and by the US military. Many have leaked, allowing petroleum to contaminate the soil and groundwater and enter as vapor into buildings, ending up as brownfields or Superfund sites. Many USTs installed before 1980 consisted of bare steel pipes, which corrode over time. Faulty installation can also cause structural failure of the tank or piping, causing leaks. Regulation in the US The 1984 Hazardous and Solid Waste Amendments to the Resource Conservation and Recovery Act (RCRA) required EPA to develop regulations for the underground storage of motor fuels to minimize and prevent environmental damage, by mandating owners and operators of UST systems to verify, maintain, and clean up sites damaged by petroleum contamination. In December 1988, EPA regulations asking owners to locate, remove, upgrade, or replace underground storage tanks became effective. Each state was given authority to establish such a program within its own jurisdiction, to compensate owners for the cleanup of underground petroleum leaks, to set standards and licensing for installers, and to register and inspect underground tanks. Most upgrades to USTs consisted of the installation of corrosion control (cathodic protection, interior lining, or a combination of cathodic protection