Top 6 Causes of Underground Storage Tank Leaks


Top 6 Causes of Underground Storage Tank Leaks

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Aging assets: repair or replace?

Owning and operating an underground storage tank (UST) is a serious responsibility, practically and legally.

These systems have the potential to leak, which can go unnoticed for long periods of time, resulting in serious environmental damage and clean-up costs.

It’s important to address the common causes of UST leaks and have the right mechanisms in place to pick up changes in your fuel levels and detect any losses from your underground systems.

So, what are the top 6 causes of UST leaks?


What causes Underground Storage Tank fuel leaks?  
1. Quality of installation

Installer quality is the single biggest risk with new tank installations. Our experience in testing thousands of new installations indicates 90% of new or remodelled sites have small leaks from pipes and fittings that need to be fixed before concreting.

For older steel systems, the quality of the original installation is also a key contributing factor along with ground disturbance and changing soil conditions.

2. Corrosion  

Corrosion of underground fuel systems is a major source of leaks. Old single-walled steel tanks without cathodic protection and steel pipelines are particularly susceptible.

The risk of leaks due to corrosion depends on the:

  • Age of the tank
  • Type of fuel
  • Type of soil
  • Presence of groundwater
  • Use of cathodic protection (protecting the steel tank by connecting it to a more easily corroded metal).
3. Incompatible materials 

Using materials in underground fuel systems that are not compatible with the type of product being stored can increase the risk of leaks. For example, a fibreglass resin tank is not compatible with ethanol as it can compromise the integrity of the fibreglass.

4. Backfill condition 

Quality of backfill around underground tanks is important, including strength, permeability and moisture content. Poor quality backfill can increase the risk of leaks. For example, it can cause concrete to sink which impacts tank and pipework integrity.

5. External causes

Factors outside the immediate fuel system or installation can also cause leaks. The effects of these can be immediate or over time, such as:

  • Puncture of tank or pipework from external works e.g. drilling
  • Ground movement due to drought
  • Movement of tanks by groundwater.

Most leaks tend to start small but gradually increase over time, so early detection is critical.

Leaks, and the impact of leaks, can be made worse by:

  • Poorly maintained leak detection equipment (or none at all)
  • Testing not being done after UST modification or upgrade
  • Inventory control methods with potentially high levels of administrative error
  • Lack of secondary containment for tanks or lines
  • Failure of sensor/alarm systems
  • Delayed response to leaks
6. Spills

In addition to leaks, spills can be caused by:

  • Overfilling underground tanks
  • Pump leaks
  • Pressure line fittings failing or not sealing properly
  • Delivery spills
  • Customers spilling fuel by overfilling vehicle tanks
  • Shut-off valve on nozzle not operational

It’s important to clean up spills quickly and appropriately. You should have a procedure on site that can be followed by all operators.

What are the risks of fuel leaks?

Now that we’ve reviewed the causes, let’s understand the risks and consequences of having a leaking underground storage tank:

Environmental: Leaks from underground fuel systems can have serious environmental consequences. Pollution from a UST can contaminate the soil, groundwater, nearby rivers and streams, and the air, damaging local ecosystems and water sources for many years. Even slow leaks can contaminate soil and groundwater beyond your site.

Health and safety: Fuels found at service stations are classified as hazardous chemicals. Petrol is highly flammable and some of its hydrocarbon components are toxic and carcinogenic. Release of petroleumbased fuels into the environment poses significant risks to peoples’ health and safety

Commercial: Leaks can result in direct financial loss through loss of product. However, the clean-up and remediation of contaminated soil or groundwater can be far more costly. Nearby properties can also be affected and, as an owner or operator, you may be liable for third party damages. There will also be a loss of revenue if your business cannot operate during remediation works

Regulatory: Fines for non-compliance with UST regulations can cost tens or even hundreds of thousands of dollars. Remediation works, or upgrades required to meet regulatory standards, can cost into the millions of dollars.

This CAN happen to you  

Fuel leaks can, and do, happen. In fact, leaks can happen at any time, on any site, large or small. If you aren’t monitoring or testing, how do you know that you don’t have a leak, or simply haven’t found it yet?


Download the UST Risk Management toolkit

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