An inside look at aging underground storage tanks

Underground storage tanks are aging, and becoming an increasingly frequent topic of discussion, research, and concern. As single-walled tanks, both fiberglass and steel, approach the end of their useful life they need to be removed from service, relined, or tested more frequently. In order to accomplish this, large operators may be looking at a significant capital expenditure and sometimes, strict deadlines. Some tanks may have deteriorated, while some may be in good working condition and pose less of an environmental risk. From the forecourt, operators might not know which category their tanks fall into.

TankCam HD® Inspections, an industry-leading and patent-pending technology from Tanknology Inc., offers a clear view inside an underground storage tank. More than 5,000 TankCam Inspections have been conducted globally since Tanknology introduced the service in 2015, with no requirement for manned entry or fuel removal. Many of the inspections have been featured in Tanknology’s popular Tank Trouble Tuesday series that aims to showcase problems commonly found inside USTs that may be impossible to see from the forecourt. Reasons for TankCam inspections vary, as some tanks have been inspected as part of large scale capital expenditure planning, while others have been inspected by proactive and risk averse operators. Many other tanks have been inspected ahead of acquisitions.

In the USA, the assumed “life” of a tank is 30 years. Research on national trends by ASTSWMO and the EPA reveals that the average historical UST lifespan is closer to 20 years; based on the age at removal. Yet forty percent of operating USTs in the United States are more than 30 years old, with an average age of 25 years. Some states require tanks to be removed by their 30th birthday, while others, including California and Florida, have deadlines requiring operators to upgrade from single-walled to double-walled USTs.

These requirements cannot prevent every leak, and operators must assume a tank can pose a risk at any age.

Best practices in managing USTs necessitates a multi-faceted approach in evaluating tanks and establishing a risk management practice. A tank operator should consider their plan in the context of leak detection equipment, spill and overfill equipment, cathodic protection, inspections completed, tank tightness tests, and local regulations, among other factors.

Site risk factors to aging USTs may include: the removal or installation of other tanks, settling or degrading of the tank slab, fluctuating groundwater conditions, changes in product storage and compatibility (particularly as it relates to E10 and biodiesel), excessive loading, or natural disasters, such as floods or earthquakes.

When considering risk management of an individual tank, site operators should review the UST manufacturer, model, and age, type of cathodic protection (on steel tanks), maintenance records, leak detection history and type of leak detection used, and a history of problems with similar systems. Water management in storage systems is also more important than ever before, especially with prolonged use of ethanol, biodiesel, and ULSD.

Tanknology’s experience conducting remote internal tank video inspections began with the introduction of the PetroScope® system in 1991. With nearly 20 years of expertise in visual inspections and over 5,000 TankCam inspections, Tanknology offers the following insights into what may go wrong in a UST.

Operators of fiberglass tanks must be aware of the following risks: deflection and/or flattening of the tank bottom and degradation of the tank interior and gel coating that can lead to blistering, delamination, and exposed fibers. Cracks may form anywhere inside the tank, but are most often found along the rib lines.

Severe flaking on most surfaces of a fiberglass tank. Diligent monitoring of leak detection results and periodic follow-up inspections recommended to detect possible crack formation. | © Tanknology Inc.

Steel tanks operators must contend with corrosion as their foremost concern. External corrosion may occur if cathodic protection systems have not been properly maintained. Internal corrosion is typically worse in tanks containing ultra-low sulfur diesel, but can be found in tanks containing other fuels. This is often accompanied by water issues, high moisture or humidity, and is especially prevalent in tanks that have not been properly maintained or cleaned. Steel tanks may also form cracks, particularly along welds. Additionally, the condition of a tank lining must also be periodically reviewed and assessed for damage.

Significant corrosion on tank top, walls, and ball float in a steel tank containing E10. | © Tanknology Inc.

Lining detached from the surface of a steel tank. — Significant corrosion on tank top, walls, and ball float in a steel tank containing E10. | © Tanknology Inc.

Both steel and fiberglass tanks may form cracks, holes, or other perforations in the tank wall resulting in an ingress of ground water, or a catastrophic release into the environment. And while cracks are most often found in older tanks, TankCam inspections have found holes in tanks of every age.

Ingress of water through crack in tank wall of fiberglass tank. | © Tanknology Inc.

A TankCam Inspection is a proactive step in reducing risk for an aging UST system. Tanknology partners with tank operators to determine the best course of action in a full evaluation of their tank system, and the inspection may be paired with a tank tightness test, deflection test for fiberglass tanks, and fuel analysis. Large operators may deploy custom-developed rubrics to assist with prioritizing replacement, including grading scales based on the presence of corrosion, delamination, and more.

TankCam HD is available nationwide in the US and for international license. Contact Tanknology at sales@tanknology.com to learn more about this service and its role in evaluating aging tanks. Contact Tanknology at international@tanknology.com to discuss international licensing opportunities.