Closing underground storage tanks

• After 12 months of temporary closure, the company must permanently close the UST.
• Notify the implementing agency at least 30 days before permanently closing the UST.

Tank closure is one way to help protect human health and the environment, particularly groundwater, from the threats posed by many older underground storage tanks. The company can close the underground storage tank (UST) temporarily or permanently.

Temporary closings

The company may temporarily close the UST for up to 12 months by following these requirements:

• Continue to maintain and monitor corrosion protection systems;
• Continue to maintain financial responsibility;
• The company’s operators must be trained;
• If the temporarily closed UST is not empty, the company must also:
  • Continue to monitor for leaks by performing release detection,
  • Perform monthly walkthrough inspections for release detection,
  • Perform annual inspections and tests of release detection equipment, and
  • Perform three-year containment sump testing if using the containment sump for interstitial monitoring of the piping.
• If a release is discovered, quickly stop the release, notify the implementing agency, and take appropriate action to clean up the site;
• If the UST remains temporarily closed for more than three months, leave vent lines open, but cap and secure all other lines, pumps, manways, and ancillary equipment.

USTs in temporary closure are not required to meet the following requirements:

• Spill testing
• Overfill inspections

Empty USTs do not require:

• Release detection
• Annual release detection testing and inspections
• Monthly walkthrough inspections
• Three-year containment sump testing

A UST is considered empty if no more than one inch of residue is present or not more than 0.3 percent by weight of the total capacity of the UST system remains in the system.

After 12 months of temporary closure, the company must permanently close the UST. The company’s UST, however, can remain temporarily closed indefinitely if it meets the requirements for new or upgraded USTs, except that spill and overfill requirements do not have to be met, and the company meets the requirements above for temporarily closed USTs.

Permanent closings

Notify the implementing agency at least 30 days before permanently closing the UST.

In addition, the company must determine if contamination from the UST is present in the surrounding environment. If there is contamination, the company will have to take remedial action.

The company can either remove the UST from the ground or leave it in the ground. In both cases, the tank must be emptied and cleaned by removing all liquids, dangerous vapor levels, and accumulated sludge. These potentially very hazardous actions need to be carried out carefully by following standard safety practices. (See www.epa.gov/oust/cmplastc/standard.htm for a safe closure standard.)

If the company leaves the UST in the ground, they must also either fill it with a harmless, chemically inactive solid, like sand, or close it in place in a manner approved by the implementing agency.

The implementing agency can help the company decide how best to close the UST so that it meets local requirements for closure.