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The importance of leak detection and integrity testing


Associate – Risk Consulting, Environmental, AXA XL

550,000. That’s how many underground storage tanks (USTs) are estimated to be buried across the US, storing petroleum and other hazardous substances. Several hundred thousand dollars or more. That’s the average potential price tag of what a cleanup could cost should these tanks leak and contaminate the surrounding environment.

The greatest threat posed by a leaking UST is contamination of groundwater, the source of drinking water for nearly half of all Americans. Average cleanup costs can often escalate when contaminated groundwater is discovered that impacts larger areas on- or off-site.

Across the US, many regulatory agencies, state tank funds, and property owners are dealing with the implications of aging and leaking USTs. USTs that are 30 years or older are past their warranty period and present a threat to public health if not properly maintained, monitored and operated.

Even UST systems that are less than 30 years old and meeting regulatory compliance requirements can still have smaller undetected releases. According to industry statistics, approximately 1% to 1.5% of operating USTs will fail in a given year. When releases, including overfills, go undetected or unaddressed for a long time, the impacts can be significant.

That’s why to manage environmental liability and minimize unexpected cleanup costs, any operation with onsite USTs must keep a watchful eye. Since the physical condition of underground piping and tanks cannot be visually inspected, UST owners and operators must rely on compliance with leak detection systems and equipment testing protocols to prevent component failure and product releases.

However, based on data from September 2019, the United States Environment Protection Agency (USEPA) estimated that only 68% of regulated USTs have met the most significant operational compliance requirements. That means there is a lot of room for improvement.


On the look-out for leaks

USEPA does not endorse a particular leak detection method but they provide details on techniques for operating UST owners. Leak detection guidance methods fall into four categories internal, external, interstitial and piping. Internal involves monitoring the tank’s liquid level, external is when something is installed outside the tank system, interstitial monitors the area between the UST and secondary containment, and piping includes line leak detectors or integrity testing. The technology associated with the four general categories can be further subdivided into these broad categories:

  • Electronic leak detection (ELD) methods detect changes in pressure or volume automatically and they're connected to computers to keep track of changes, they are highly accurate and can detect very small leaks.
  • Line leak detection (LLD) methods are similar to ELD, but apply the technology to the UST piping and lines
  • Mechanical leak detection (MLD) methods rely on a variety of testing devices including sensors inside and outside the tank itself


A matter of integrity

Tank tightness testing is integral for USTs. It allows owners and operators to verify the integrity of their tanks and prevent potential risks. Tightness testing is only required upon the installation of a new tank, but is also considered a best practice for unregulated or exempt USTs. 

Unregulated or abandoned tanks need integrity testing because they still have the potential to contaminate the environment, especially because they don’t have leak detection systems. Abandoned or unregulated tanks are often found during redevelopments of neighborhoods and they are extremely costly to take care of after the fact.

Since the physical condition of underground piping and tanks cannot be visually inspected, UST owners and operators must rely on compliance with leak detection systems and equipment testing protocols to prevent component failure and product releases.

Adopting best practices

To minimize environmental risks and ensure that all regulations and industry standards are being upheld, developing an operation and maintenance (O&M) plan is critical in maintaining and monitoring UST systems safely. An effective plan requires three key components:

  • Description of the equipment located onsite (including release detection, spill and overfill protection, and corrosion protection)
  • Inspection procedures, including the frequency of inspections and required testing elements
  • Outline of response actions to be taken in the event of an identified or suspected release

For larger companies with multiple sites and tanks to monitor, a management program should take its plan a step further and include a tank schedule for each site that outlines tank age, content, construction details and monitoring requirements.

Identifying responsible parties and establishing training requirements also contribute to an effective UST management program. And to help assure that ongoing regulatory requirements and best management practices are used, a tracking system and auditing program are also essential.

To help develop an effective program, the USEPA website offers guidance and resources for UST owners and operators.


Under a watchful eye

A UST management program that follows federal and state regulations, as well as industry codes and standards, is a must but it can be challenging. Unfortunately, there is no single government regulation that governs every UST. USEPA issued UST regulations many years ago that included certain exemptions. There are also individual state and territorial program standards. To avoid conflict, approximately 40 states have been USEPA-approved to administer UST programs so that owners and operators do not need to comply with two sets of regulations.

Given the available compliance options, there are many factors that dictate what oversight should be provided by an UST management program. For example, petroleum USTs require financial responsibility mechanisms to ensure adequate funding or insurance for corrective action or closure, while USTs storing other hazardous substances may only need to meet the same physical system requirements without a State-mandated financial responsibility.

To minimize risks to the environment and to public health, USTs need to be monitored, maintained, and operated to the highest standards. Leak detection systems and integrity testing protocols are not foolproof and depending on their sensitivity may not readily detect small releases occurring from old USTs. It is important for UST owners to budget accordingly for system upgrades before it is too late. Old, unregulated, abandoned USTs can be costly for owners, and the environment. Read more in AXA XL’s Environmental Risk Bulletin -- Underground storage tank management: leak detection and integrity testing.


Mark Creager is a Risk Consulting Associate with AXA XL’s Environmental Insurance business. He can be reached at

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