Underground storage tank systems (USTs) store petroleum products or certain other hazardous liquids that can harm the environment and human health if the contents are released into the environment.  Underground storage tanks are subject to federal regulations. Idaho has about 3,500 regulated USTs; there are about 680,000 nationwide. 

While many types of storage tanks may be buried underground, the term "underground storage tank" refers specifically to certain types of tanks that are federally regulated.  These tanks are those that are buried at least 10% underground and store either petroleum products (gasoline, diesel, kerosene, jet fuel) or certain hazardous substances.  The underground piping connected to the tanks is also considered part of the UST.  Underground storage tanks are most often found at gas stations and other fueling facilities. 

Certain types of tanks are specifically exempt from federal UST regulations:

• Small tanks that hold 110 gallons or less.
• Farm and residential tanks that hold 1,100 gallons or less of motor fuel used for noncommercial purposes.
• Tanks storing heating oil used on the premises where it is stored.
• Tanks on or above the floor of underground areas, such as basements.
• Septic tanks and systems for collecting storm water and wastewater.
• Emergency spill and overfill tanks.

On August 8, 2005, President Bush signed the Energy Policy Act of 2005. Title XV, Subtitle B of this act, entitled the Underground Storage Tank Compliance Act of 2005 (pdf 79 kb, 15 pages), amending Subtitle I of the Solid Waste Disposal Act, the original legislation that created the underground storage tank program. Federal regulations entitled Technical Standards and Corrective Action Requirements for Owners and Operators of Underground Storage Tanks (40 CFR Part 280) (pdf 365 kb, 70 pages) also regulate USTs.

The federal Underground Storage Tank Compliance Act of 2005 required states that receive federal funding to comply with the requirements of the federal law and regulations. On February 23, 2007, the Idaho Legislature passed the Idaho Underground Storage Tank Act, which gave DEQ the authority to establish an underground storage tank program. DEQ subsequently conducted a negotiated rulemaking to develop Idaho's rules to regulate underground storage tanks. The Rules Regulating Underground Storage Tank Systems (IDAPA 58.01.07) took effect April 2, 2008. They contain contain the following sections:

• Federal Technical Standards and Corrective Action Requirements for Owners and Operators of Underground Storage Tanks, 40 CFR Part 280
• Additional Measures to Protect Ground Water from Contamination
• Release Reporting Requirements
• Training Requirements
• Inspections
• Delivery Prohibition
• Maintenance of the Petroleum Underground Storage Tank Database

› Link to A Summary of DEQ's Underground Storage Tank Rules.
  (DEQ Fact Sheet: April 2008: pdf 57 kb, 2 pages)

Simply put, a leaking underground storage tank (LUST) is any UST that is leaking.  However, any type of underground tank that is leaking (even if it is not a federally regulated "UST") can harm the environment and may be subject to state cleanup requirements, so all tank owners need to be vigilant about leaks.

Most USTs installed through the 1980s were bare steel tanks, which eventually corrode and leak.  Many old tanks have reached or passed this point.  Faulty installation or inadequate operation and maintenance also can cause USTs to release their contents into the environment.

In 1984, Congress directed the U.S. Environmental Protection Agency (EPA) to publish regulations that require owners and operators of USTs to prevent, detect, and clean up releases. Congress also banned the installation of unprotected steel tanks and piping beginning in 1985.  New tanks include a corrosion resistant covering or are made of non-corrodible materials.  Old steel tanks also had to be retrofitted with a corrosion protection system by December 1998.  Each steel tank and its corrosion protection system must be tested and/or inspected at least once every three years.

The greatest potential hazard from a LUST is that the petroleum or other hazardous substance can seep into the soil and contaminate ground water.  In Idaho, ground water supplies about 95% of the population's drinking water, so keeping it clean is a high priority.   

When an UST leaks, the liquid seeps down through unsaturated soil to the water table.  At the water table, the liquid usually forms a pool on top of the water, because most substances in USTs (e.g., petroleum) are less dense than water.  Once at the water table, the liquid slowly moves in the same direction as the ground water. 

Even a hole the size of a pinhead can eventually leak enough liquid to cause widespread contamination.  In the past there were not very good methods for detecting leaks and many went unnoticed until contamination was widespread.  Testing methods have improved, however, and current rules require owners to monitor for leaks on a regular basis. 

Once a leak is detected, the general extent of the contamination is determined.  Next, monitoring wells are usually drilled to obtain a more detailed assessment of ground water contamination.  Once the extent of contamination has been determined, a remediation (cleanup) plan is developed and implemented.    

DEQ maintains information on LUST sites and on all known active and closed UST sites across the state.  All regulated USTs must be registered with DEQ and all petroleum releases (from regulated and unregulated tanks) must be reported to DEQ (see IDAPA 58.01.02.851).   

› Link to LUST interactive mapping at DEQ's Waste Division Inventory.

Petroleum spills and leaks account for a significant number of costly environmental problems. Tank owners can be held financially responsible for costs associated with cleaning up releases and compensating third parties in the event of a leak or spill.  Federal law requires owners to carry pollution liability coverage for regulated USTs to demonstrate they have the resources to pay for cleanup and compensatory costs.

Most commercial and homeowner's insurance policies contain what is commonly referred to as an "absolute pollution exclusion" which specifically excludes pollution-related claims. Idaho's Petroleum Storage Tank Fund (PSTF) operates as a nonprofit insurance company and is responsible for administering the Idaho Petroleum Clean Water Trust Fund. The petroleum liability insurance policies issued to owners and operators of regulated USTs through the PSTF satisfies the federal financial responsibility requirements. The PSTF also provides insurance coverage to owners of all eligible unregulated above ground and underground petroleum storage tanks, including farm, ranch, home, and commercial heating oil tanks.  PSTF's policy does not provide coverage for preexisting contamination or tank installation, removal, repair, or replacement.

If you own, or plan to buy or sell, property that you suspect may contain an UST (even one that is no longer in use), it is important to find out.  The question of possible contamination from a leaking tank (past or present) will almost certainly come up in any transaction involving property which has or has had an UST. Any past or newly discovered contamination must be disclosed to any potential buyer and reported to DEQ to determine if remedial action is warranted.

A walk-through of a property may uncover evidence of abandoned USTs, but won't always.  There may be nothing visible above ground to indicate the presence of USTs below ground. While certain types of property are more likely than others to house USTs, any property could—USTs have been found in many unusual places.  Underground storage tanks are commonly found at gasoline stations, convenience stores, bus terminals, railroad yards, airfields, and auto dealerships, but have also been found at schools, auto repair shops, farms, homes, factories, retail facilities, and other locations.

If you have any reason to suspect an UST on your property, check the Waste Division Inventory on DEQ's Web site. DEQ maintains information on active and closed UST sites across the state and may have information on your property.  If DEQ does not have a record of an UST on the property, you may want to have it investigated. You (or the property owner, if you are considering buying the property) can hire a contractor to conduct an environmental site assessment. Lenders often require a site assessment before they make a loan on certain types of commercial properties anyway. 

For more information on buying or selling property containing USTs, read Real Estate Professionals and Underground Storage Tanks (DEQ Publication, May 2002: pdf 75 kb, 12 pages).

Thousands of homes in Idaho are heated with heating oil stored in underground tanks on the owner’s property and thousands more have old heating oil tanks that are no longer used buried on the property.  Many of these unused tanks still contain heating oil.  While heating oil tanks are not federally regulated under UST regulations, a leaking tank can harm the environment and may be subject to state cleanup requirements.

It takes about 30 years before corrosion will make an underground heating oil tank prone to leaking; however, the life of an individual tank can vary widely depending on the properties of the surrounding soil. A leaking underground heating oil tank can contaminate the environment and cause problems for the landowner.  Even tiny amounts of heating oil left in a seemingly empty tank can leak.  Potential problems caused by a leaking tank can include:

• Liability. The property owner can be held liable for damage caused by contamination from the tank.
• Soil Contamination. Leaks can contaminate soil on the site and neighboring property.
• Water Contamination. Leaks can contaminate ground water and possibly the residents’ well water.
• Cave-Ins. Cave-ins can happen when tanks deteriorate from corrosion and the tank walls collapse.

In addition, more and more lending institutions and buyers require closure of unused heating oil tanks before they will finalize a residential sale.  Even if you don’t intend to sell the property, you may want to consider closing the tank for your own protection. 

If your heating oil tank is still in use, watch for signs that it may be leaking, such as your furnace using more fuel than usual (consider other possible reasons as well, such as unusual weather or furnace malfunction.)  You may also wish to actively check for leaks. 

For more information on closing a residential heating oil tanks and checking for leaks, see Real Estate Professionals and Underground Storage Tanks (DEQ Publication, May 2002: pdf 75 kb, 12 pages) or contact your local DEQ regional office.