Department of
Environmental Quality

A leaking underground storage tank (LUST) is any underground storage tank (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 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.

Hazards of Leaking Tanks

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. Under Section 851 of Idaho's Water Quality Standards (IDAPA 58.01.02), all regulated USTs must be registered with DEQ and all petroleum releases (from regulated and unregulated tanks) must be reported to DEQ.

Petroleum Storage Tank Fund

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.