Department of
Environmental Quality

Underground storage tanks (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.

What is an Underground Storage Tank?

While many types of storage tanks may be buried, the term "underground storage tank" refers specifically to certain types of tanks that are federally regulated.  These tanks are those in which 10% of their contents are underground and store either petroleum products (gasoline, diesel, kerosene, jet fuel, etc.) or certain hazardous substances. The underground piping connected to the tanks is also considered part of the UST system.

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

• Small tanks with capacities of 110 gallons or less
• Farm and residential tanks with capacities of 1,100 gallons or less of motor fuel used for noncommercial purposes
• Tanks storing heating oil for on-site consumption
• 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

Regulation of Underground Storage Tanks

In February 2007, the Idaho Legislature passed the Idaho Underground Storage Tank Act, which authorized DEQ to establish an underground storage tank program. DEQ subsequently conducted negotiated rulemaking to develop Idaho's rules to regulate USTs. The Rules Regulating Underground Storage Tank Systems (IDAPA 58.01.07) took effect April 2, 2008. The rules 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 UST Database

• Summary of DEQ's Underground Storage Tank Rules

How to Learn if Your Property Contains an UST

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 if an UST exists or has existed at the property. The question of possible contamination from a leaking UST (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 required.

A visit to the property may uncover evidence of abandoned USTs. In many cases, there may be no above ground indicators of the presence of an UST below ground. While certain property types are more likely than others to house USTs, any property could contain an UST. USTs are routinely found in unusual places. USTs are commonly found at gasoline stations, convenience stores, bus terminals, railroad yards, airfields, and auto dealerships. USTs have also been found at schools, auto repair shops, farms, homes, factories, retail facilities, and other locations. 

DEQ maintains a database of active and closed UST sites across the state. Regardless of whether DEQ has a record of an UST on property of interest, you may wish to investigate as a normal course of due diligence. If you are considering buying or selling a property, you may wish to hire a contractor to conduct an environmental site assessment. Lenders often require site assessments before loaning on certain types of properties.

• Database of UST-LUST Sites in Idaho