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Tank Tightness Testing With Inventory Control

When performed according to the manufacturer's specifications, periodic tank tightness testing combined with monthly inventory control can temporarily meet the federal leak detection requirements for tanks (this method does not detect piping leaks). Inventory control alone does NOT meet the federal requirements for leak detection for tanks.

Tightness testing (if conducted at least every 3 years) is also an option for underground piping.

Tank Tightness Testing

How does tank tightness testing work?

Tightness tests include a wide variety of methods. Other terms used for these methods include "precision," "volumetric," and "nonvolumetric" testing.

The features of tank tightness testing are:

What are the regulatory requirements for tank tightness testing?

Anything else about tank tightness testing that you should consider?

Inventory Control

How does inventory control work?

Inventory control requires daily measurements of tank contents and mathematical calculations that let you compare your "stick" inventory (what you've measured) to your "book" inventory (what ym your "stick" and "book" inventory is too large, your tank may be leaking.

OUST has produced a booklet available from our web site, Doing Inventory Control Right, that clearly explains how to do inventory control with simple step-by-step directions. The booklet also includes standard forms used to record inventory data.

The features of inventory control are:

What are the regulatory requirements for inventory control?

Anything else about inventory control that you should consider?

Time restrictions on the use of this combined method...

Existing UST systems those installed before December 1988 that have not been fully upgraded with spill, overfill, and corrosion protection must have tank tightness tests annually until December 1998, after which these tanks must be upgraded, replaced, or closed.

The combined method using tank tightness testing every 5 years is valid only after the entire UST system has met spill, overfill, and corrosion protection standards. Following entire UST system upgrade, this combined method may be used for 10 years (or until December 1998, whichever is later) after the date the tank was installed or upgraded with corrosion protection. Note that the end date is based on the compliance status of the tank only, not the entire UST system. As a result, some USTs may not be able to use this combined method for as long as 10 years (see discussion below). At the end of the valid time period, you must use one of the monthly monitoring leak detection choices described in this booklet.

Unique time restriction for some existing USTs...

For some existing USTs those which had corrosion protection before the entire UST system met upgrade standards this combined method of inventory control and tightness testing every 5 years may be valid for less than 10 years.

Federal regulations state that the combined method can be used:

  1. until December 1998 or 10 years after the tank is protected from corrosion (whichever date is later), and
  2. the period of validity cannot begin until the entire UST system meets upgrade standards.

Therefore, in those cases where the tank had corrosion protection before the UST system met upgrade standards, the period of validity is less than 10 years. The effect of this restriction will be clear in the following example: a bare steel tank upgraded with corrosion prote upgrades were not added system met years after the tank has corrosion protection). In this example, the UST may use the combined method to meet federal leak detection requirements only for three years (from 1995 to 1998).

Correspondingly, when the period of validity is less than 10 years, fewer periodic tightness tests may be required. Check with your implementing agency for guidance.

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