Underground storage tank
Encyclopedia
An Underground Storage Tank
(UST), in United States environmental law, is a tank and any underground piping connected to the tank that has at least 10 percent of its combined volume underground.
USTs, used to store petroleum
, are regulated in the United States
to prevent release of petroleum and contamination of groundwater
. They are used throughout North America
at automobile
filling stations, and many have leaked, allowing petroleum to contaminate the soil
and groundwater
.
Many USTs installed before 1980 consisted of bare steel
pipes, which corrode
over time and may eventually result in leakage. Faulty installation and inadequate handling may also cause leaks.
In 1984, in the United States, the Congress developed laws to minimize and prevent environmental damage, by charging owners with the task of verifying, maintaining, and, if necessary, cleaning up sites damaged by petroleum contamination.
Legislation requiring owners to locate, remove, upgrade, or replace underground storage tanks became effective December 24, 1989. Each state was given authority to establish a program within its own jurisdiction to set up a program 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
), overfill protection (to prevent overfills of the tank during tank filling operations), spill containment
(to catch spills when filling), and leak detection for both the tank and piping.
Many USTs were removed without replacement during the 10-year program and many thousands of old underground tanks were replaced with newer tanks made of corrosion resistant materials (such as fiberglass
) and constructed as double walled tanks to catch leaks from the inner tanks and to give an interstitial space to accommodate leak detection sensors. Piping was replaced during the same period with much of the new piping being double-wall construction and made of fiberglass or plastic
materials.
Tank monitoring systems capable of detecting leaks as small as 0.1 gallons-per-hour were installed and other methods were adopted to alert the tank operator of leaks and potential leaks.
Regulations included a requirement that UST cathodic protection systems be tested by a cathodic protection expert (minimum every three years) and that systems be monitored to ensure continued compliant operation.
Many owners, who previously stored fuel in underground tanks, switched to above-ground tanks to enable closer environmental monitoring of fuel storage and to reduce costs. Many states, however, do not permit above-ground storage of motor fuel for resale to the public.
The United States Environmental Protection Agency
(EPA) Underground Storage Tank Program is generally considered to have been very successful. The national inventory of underground tanks has been reduced by more than half, and most of the rest have been replaced or upgraded to much safer standards. But of the approximately one million underground storage tanks sites in the United States as of 2008, most of which handle some type of fuel, an estimated 500,000 have had leaks. As of 2009, there were approximately 600,000 active USTs at 223,000 sites subject to federal regulation.
for consumptive use on the premises, or septic tank
s.
In 1988, EPA published stringent underground storage tank regulations, including a 10-year phase-in period that required all operators to upgrade their USTs with spill prevention and leak detection equipment.
Storage tank
A storage tank is a container, usually for holding liquids, sometimes for compressed gases . The term can be used for reservoirs , and for manufactured containers. The usage of the word tank for reservoirs is common or universal in Indian English, American English and moderately common in British...
(UST), in United States environmental law, is a tank and any underground piping connected to the tank that has at least 10 percent of its combined volume underground.
Tank types
Underground storage tanks generally fall into four different types:- SteelSteelSteel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
/aluminum tank, made by manufacturers in most states and conforming to standards set by the Steel Tank Institute. - Composite overwrappedComposite materialComposite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
, a metal tank (aluminum/steel) with filament windings like glass fiber/aramidAramidAramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic rated body armor fabric and ballistic composites, in bicycle tires, and as an asbestos substitute. The name is a portmanteau of "aromatic polyamide"...
or carbon fiberCarbon fiberCarbon fiber, alternatively graphite fiber, carbon graphite or CF, is a material consisting of fibers about 5–10 μm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in crystals that are more or less aligned parallel to the long axis of the fiber...
or a plastic compound around the metal cylinder for corrosion protection and to form an interstitial space. - Tanks made from compositeComposite materialComposite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
material, fiberglassFiberglassGlass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...
/aramidAramidAramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic rated body armor fabric and ballistic composites, in bicycle tires, and as an asbestos substitute. The name is a portmanteau of "aromatic polyamide"...
or carbon fiberCarbon fiberCarbon fiber, alternatively graphite fiber, carbon graphite or CF, is a material consisting of fibers about 5–10 μm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in crystals that are more or less aligned parallel to the long axis of the fiber...
with a metal liner (aluminum or steel). See metal matrix compositeMetal matrix compositeA metal matrix composite is composite material with at least two constituent parts, one being a metal. The other material may be a different metal or another material, such as a ceramic or organic compound. When at least three materials are present, it is called a hybrid composite...
. - Composite tanks such as carbon fiber with a polymer liner (thermoplasticThermoplasticThermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...
). See rotational moldingRotational moldingRotational molding, also known as rotomolding, rotocasting or spin casting, is a molding process for creating many kinds of mostly hollow items, typically of plastic....
and fibre-reinforced plasticFibre-reinforced plasticFibre-reinforced plastic is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually fibreglass, carbon, or aramid, while the polymer is usually an epoxy, vinylester or polyester thermosetting plastic...
(FRP).
Petroleum underground storage tanks
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
, are regulated in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
to prevent release of petroleum and contamination of groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
. They are used throughout North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
at automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
filling stations, and many have leaked, allowing petroleum to contaminate the soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
and groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
.
Many USTs installed before 1980 consisted of bare steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
pipes, which corrode
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
over time and may eventually result in leakage. Faulty installation and inadequate handling may also cause leaks.
In 1984, in the United States, the Congress developed laws to minimize and prevent environmental damage, by charging owners with the task of verifying, maintaining, and, if necessary, cleaning up sites damaged by petroleum contamination.
Legislation requiring owners to locate, remove, upgrade, or replace underground storage tanks became effective December 24, 1989. Each state was given authority to establish a program within its own jurisdiction to set up a program 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
Cathodic protection
Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. The simplest method to apply CP is by connecting the metal to be protected with another more easily corroded "sacrificial metal" to act as the anode of the...
), overfill protection (to prevent overfills of the tank during tank filling operations), spill containment
Oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...
(to catch spills when filling), and leak detection for both the tank and piping.
Many USTs were removed without replacement during the 10-year program and many thousands of old underground tanks were replaced with newer tanks made of corrosion resistant materials (such as fiberglass
Fiberglass
Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...
) and constructed as double walled tanks to catch leaks from the inner tanks and to give an interstitial space to accommodate leak detection sensors. Piping was replaced during the same period with much of the new piping being double-wall construction and made of fiberglass or plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
materials.
Tank monitoring systems capable of detecting leaks as small as 0.1 gallons-per-hour were installed and other methods were adopted to alert the tank operator of leaks and potential leaks.
Regulations included a requirement that UST cathodic protection systems be tested by a cathodic protection expert (minimum every three years) and that systems be monitored to ensure continued compliant operation.
Many owners, who previously stored fuel in underground tanks, switched to above-ground tanks to enable closer environmental monitoring of fuel storage and to reduce costs. Many states, however, do not permit above-ground storage of motor fuel for resale to the public.
The United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
(EPA) Underground Storage Tank Program is generally considered to have been very successful. The national inventory of underground tanks has been reduced by more than half, and most of the rest have been replaced or upgraded to much safer standards. But of the approximately one million underground storage tanks sites in the United States as of 2008, most of which handle some type of fuel, an estimated 500,000 have had leaks. As of 2009, there were approximately 600,000 active USTs at 223,000 sites subject to federal regulation.
Defined in federal law
Underground storage tank or UST means any one or combination of tanks (including underground pipes connected thereto) that is used to contain an accumulation of regulated substances, and the volume of which (including the volume of underground pipes connected thereto) is 10 percent or more beneath the surface of the ground. This does not include, among other things, any farm or residential tank of 1,100 gallons or less capacity used for storing motor fuel for noncommercial purposes, tanks used for storing heating oilHeating oil
Heating oil, or oil heat, is a low viscosity, flammable liquid petroleum product used as a fuel for furnaces or boilers in buildings. Home heating oil is often abbreviated as HHO...
for consumptive use on the premises, or septic tank
Septic tank
A septic tank is a key component of the septic system, a small-scale sewage treatment system common in areas with no connection to main sewage pipes provided by local governments or private corporations...
s.
In 1988, EPA published stringent underground storage tank regulations, including a 10-year phase-in period that required all operators to upgrade their USTs with spill prevention and leak detection equipment.