Emergency Preparedness and Response, Special Topics in Environmental Management

Quick Guide to Petroleum UST Requirements

Corrosion Protection

New tanks must be constructed of coated and cathodically protected steel, fiberglass, or steel clad with fiberglass. New piping must be made of coated and cathodically protected steel or of fiberglass as provided in 40 CFR 280.20. All cathodic protection systems must be tested within 6 months of installation and at least every 3 years thereafter.

Spill and Overfill Prevention

Tanks must be equipped with catchment basins and one of the following: automatic shutoff devices, overfill alarms, or ball float valves as provided in 40 CFR 280.30. UST owners must follow correct tank filling practices. If a UST never receives more than 25 gallons (gal) at a time, the UST does not have to meet the overfill protection requirements.


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Leak Detection

Leak detection mechanisms must meet three basic requirements:

  • The leak detection must be able to detect a leak from any portion of the tank or its piping that routinely contains petroleum.
  • It must be installed, calibrated, operated, and maintained in accordance with the manufacturer’s instructions.
  • The leak detection must meet the performance requirements described in the federal regulations under 40 CFR 280.43 and 40 CFR 280.44.

Owners and operators of petroleum USTs must use one of the two leak detection methods below – monthly monitoring or monthly inventory control — or other methods approved by their state agency.

Monthly Monitoring

Monthly monitoring includes:

  • Secondary containment and interstitial monitoring. This involves placing a barrier between the UST and the environment. The barrier provides secondary containment and can be a vault, liner, or the outer wall of a double-walled structure. Interstitial monitoring methods range from a simple dip stick to automated vapor or liquid sensors permanently installed in the system. All USTs holding hazardous substances that were installed after December 22, 1988, must use this method.
  • Automatic tank gauging (ATG) systems. ATGs use monitors permanently installed in the tank. These monitors are linked electronically to a nearby control device to provide information on product level and temperature. The gauging system can automatically calculate the changes in product volume that can indicate a leaking tank. This method does not work on piping.
  • Vapor monitoring. Vapor monitors sense and measure product vapor in the soil around the tank and piping to determine the presence of a leak. This method requires installation of carefully placed monitoring wells. Vapor monitoring can be performed periodically using manual devices or continuously using permanently installed equipment.
  • Groundwater monitoring. Groundwater monitoring devices sense the presence of liquid product floating on the groundwater. This method requires installation of monitoring wells at strategic locations in the ground near the tank and along the piping runs. To discover if leaked product has reached groundwater, these wells can be checked periodically by hand or continuously with permanently installed equipment. This method is effective only at sites where groundwater is within 20 feet of the surface.
  • Statistical inventory reconciliation (SIR). SIR uses sophisticated computer software to determine whether a tank system is leaking. The computer conducts a statistical analysis of inventory, delivery, and dispensing data collected over a period of time and as provided by the operator to a vendor.
  • Manual tank gauging. Manual tank gauging can be used only on tanks 2,000 gal or smaller. This method does NOT work on tanks larger than 2,000 gal or on piping. This method requires taking the tank out of service for at least 36 hours each week to take measurements of the tank’s contents. Tanks of 1,000 gal or less can use this method alone. Tanks from 1,001 to 2,000 gal can use this method only when it is combined with periodic tank tightness testing and only for 10 years after installing a new UST or upgrading a UST with corrosion protection. After 10 years, UST owners and operators must use one of the other listed leak detection methods.

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Monthly Inventory Control

The leak detection method of monthly inventory control and tank tightness testing every 5 years can be used for only 10 years after installing a new UST or upgrading a UST with corrosion protection. After the 10-year period, monthly monitoring is required.

Tank tightness testing requires periodic tests conducted by those who temporarily install special equipment that tests the soundness of the tank. Tank tightness testing must be used in combination with inventory control. Inventory control requires taking daily accurate measurements of the tank’s contents and performing monthly calculations to determine that the system is not leaking.

See tomorrow’s Advisor for more on petroleum USTs.