Underground Storage Tanks (or UST) is a storage tank , excluding any underground piping linked to the tank, with not less than 10 percent of its volume underground. It is used to hold regulated substances such as heating, oil, motor oil, or can be used as a septic tank. Owners are held accountable for any leak or releases connected with the operation of the tanks.
In September 1988, The U.S. Environmental Protection Agency ordered all operators to enhance their tanks with leak detection and spill prevention. These changes will help prevent UST releases, which can lead to water contamination. The changes include: Adding a secondary containment area for new, as well as replaced tanks and piping; Increased operator training requirements; and Added requirements for maintenance of UST systems. It also now requires all UST systems to be checked before certain biofuels can be stored and includes updating its code of practice.
There are four types of UST: The first is a steel or aluminum tank which is made by most manufacturers and meets the standards set by the Steel Tank Institute. The second is a composite overwrapped tank which is a metal tank with filament windings like glass fiber or carbon fiber to protect it against corrosion. The third is a tank which is made from a composite material like fiberglass or carbon fiber and comes with a metal liner. The last type is the Composite tanks like carbon fiber and instead of metal, it uses a polymer liner.
USTs are most used as storage for gasoline in gas stations as well as the military. However, many have leaked causing soil and water contamination. USTs before 1980 consisted of steel pipes which corrode as time passes. Incorrect or faulty installation of the tank can lead to a leak, caused by the structural failure of the tank.
In the U.S., USTs are regulated to prevent release of gas and to prevent the contamination of the soil, air and water. The 1984 Resource Conservation and Recovery Act (known as the RCRA) required the EPA to establish regulations in terms of motor fuel underground storage to prevent environmental damage, by mandating operators and owners of UST systems to maintain and clean up areas which were damaged by UST storage.
In 1988, EPA regulations telling owners to upgrade, or replace USTs became effective. Each state was given the right to start its own program, to compensate owners for the cleanup of UST leaks, and to set standards for installers. It also must inspect all underground tanks.
Most of the upgrades consisted of corrosion control, which is an inner lining in the tank, overfill protection, spill containment, as well as leak detection in both the tank and the piping. During this 10-year program, many USTs were removed without replacement. Many more were replaced with tanks made of materials resistant to corrosion. Others were built as double wall tanks which allowed for detection of leaks by using vacuum, or a sensor. Monitoring systems were installed to alert tank operators of leaks, as well as potential leaks. Regulations state that all systems must be tested by an expert, and that systems be maintained for safe operation. Some owners chose to switch to above ground tanks for storage of motor fuels. However, many states prohibit this.
As of 2008, an estimated 500,000 tanks were found to have leaks. In 2009 there are approximately 600,000 active USTs in 223,000 sites subject of federal laws. The EPA, in 2012, demonstrated a method how to inspect buildings that are vulnerable to petroleum intrusion. And in 2015 the EPA released its
Underground Storage Tanks UST Regulations
An underground storage tank (UST) system is a tank (or a combination of tanks) and connected underground piping having at least 10 percent of their combined volume underground. The tank system includes the tank, underground connected piping, underground ancillary equipment, and any containment system. The federal UST regulations apply only to UST systems storing either petroleum or certain hazardous substances. When the UST program began, there were approximately 2.1 million regulated UST systems in the United States. Today there are far fewer since many substandard UST systems have been closed. For the most current statistics, see UST Performance Measures. Nearly all USTs regulated by the underground storage tank requirements contain petroleum. UST owners include marketers who sell gasoline to the public (such as service stations and convenience stores) and non marketers who use tanks solely for their own needs (such as fleet service operators and local governments). EPA estimates that less than 10,000 tanks hold hazardous substances covered by the UST regulations.
Read more at the EPA.gov site