The legacy of underground storage tanks

Published on 9 March 2022

Underground petroleum storage tanks

The history of underground storage tanks is strongly connected to the oil industry. Soon after oil was discovered, and more uses for it were revealed, the need for storage became evident. At first oil was stored in whiskey barrels and other improvised containers, but these did not satisfy the long term nor the large capacity needed. Steel tanks were invented sometime at the end of the 19th century. While they were built initially to store petroleum products, their use expanded to any liquid chemical requiring storage in large volumes.

Urban tank use is correlated with the mass distribution of petroleum products during the expansion of the automobile industry. The fuel was initially stored within the dispenser because small quantities were needed, however evolved to above ground storage tanks. Underground storage tanks quickly followed, mostly as a response to safety concerns (collisions) and a smarter utilization of expensive urban space. Tank sizes increased, but their structure remained mostly unchanged for decades.

The main concern associated with steel tanks was corrosion. Different corrosion prevention methods were adopted, some more successful than others. They included installing the tank in plastic wrapping, coating with different materials, cathodic protection, and secondary containment. When environmental monitoring became increasingly common, attention was also attributed to the pumps, boxes, and sumps. Non-metallic tanks were eventually developed; this was done concurrently with improvements in flexible tubing, standardized sumps and vapour recovery equipment.

Tanks became standardized at the beginning of the 20th century. Provincial and federal regulatory deadlines were imposed to implement the new changes. The government requirements had two main consequences:

  1. a decrease in UST sites as more users decided to not use onsite tanks for their fuelling supplies, resulting in a concentration of fuelling services;
  2. the implementation of safer tanks and associated infrastructure.

The years when steel tanks were buried with minimal monitoring represent a significant environmental legacy. Tank owners not aware of environmental damages combined with very cheap fuel meant that leaks went unnoticed for years. This was the time when science magazines were claiming that engine oil could be properly disposed of in holes in the ground. Numerous soil and groundwater contamination plumes have their origins in the mid- to late-20th century. Outdated remediation methods, such as spreading the contamination throughout the property, only added to the issue.

Governments understood the liability associated with leaky underground storage tanks and took steps to help mitigate the problem. In the 1990s they began documenting and registering existing tanks. The Government of Alberta helped over 1,000 small owners of gas stations and municipalities remove old tanks and cleanup sites between 2000 and 2018 through a grant offered by Alberta Municipal Affairs. This program was very successful and our contaminated sites inventory would look completely different nowadays without it.

Underground storage tanks only draw the public’s attention when a municipality suffers from the effects of fuel leaking from tanks. The recent 2021 Iqaluit water emergency is a tragic example of how an entire municipality can be affected by a historical underground fuel spill. Nonetheless, this is not an exception. There are numerous underground fuel leaks that affect residents by vapour intrusion or by contaminating the water source.

How can we address the environmental impact of old underground storage tanks? We cannot expect to fix decades of improper practices instantly, however, prioritizing the damage caused by underground storage tanks is an important first step in preventing future disasters.

Government should not adopt a punitive approach

Owners of sites with historical contamination associated with underground storage tanks have no incentive at this moment to investigate the environmental status of the property. A historical leak is treated in a similar manner as a new spill by Alberta Environment.

We hear from owners of properties with former tanks that they are hesitant to start an investigation because they do not have the financial means to deal with the problem, and Alberta Environment will force them instead of helping. An independent owner of a property which was formerly a gas station in the 1960s, now decommissioned, is likely not the party that profited from the fuel sales at that time. In this scenario, they purchased the property at a time when environmental assessments were not standard practice with regards to transacting properties. Now, they are left to deal with the realities of a society that is increasingly aware of environmental concerns.

Does the fault lie with the current landowner? Should they bear the cost of this societal change?

Learn from the success of the Tank Removal Program implemented in 2000-2018

This initiative of the government to remove the tanks was done with minimal cost (a little over $100 million dollars to our knowledge) and a handful of very competent people. The owners still had to deal with a portion of the cost (GST) and the operational cost of closing down gas stations for a longer period of time, to allow environmental consultants to remediate the sites.

When contamination was a significantly greater volume than expected, moved offsite, or required long term monitoring, the owner often took over the extra cost or inconvenience in order to have an ultimately clean site. Numerous municipalities dealt with very old tanks and remediated offsite plumes that were threatening nearby residences or drinking water supplies.

The cost of dealing with the contamination now from the hundreds of tanks removed under this program would be exponentially higher. If we extrapolate this to the current cost to clean up existing UST-associated contamination, and then to the cost we will have to bear in the future, it becomes clear that we require government assistance to remediate historical contamination.

Mandate perimeter monitoring for existing tank owners

Since historical underground storage tanks created so many problems in the past, you would expect the problem to be fixed. While tanks today are safer and better monitored, and tank owners more aware, we are still seeing lack of complete monitoring of existing UST systems. Annual perimeter testing of groundwater around existing tanks and filing of results in the public ESAR database would mean full accountability of tank owners, as well as a chance to deal with leaks in a manageable time frame. Monitoring of four groundwater monitoring wells around the tank nest and pump island once a year is an operational cost that any owner of a gas station can afford. This would indicate that any leak that impacts groundwater is detected no later than one year and remediation can be undertaken at a time when it can make a difference. It would also prevent owners of nearby properties to undertake unnecessary subsurface investigations in order to refinance or resell their property.

Invest in research of current fuel solutions

Current fuel solutions are developed by petroleum marketers but not supervised from an environmental perspective. For example, use of leaded gasoline created contamination plumes that we still struggle with, and MTBE caused serious environmental issues. The current use of ethanol as an octane booster will likely prove to have environmental ramifications and be replaced by another solution during our lifetime. Ethanol production meant displacement of healthy agricultural or other land uses with corn crops that are water intensive and greenhouse gas rich. Ethanol is also a co-solvent, which means that gasoline plumes will likely be bigger because ethanol dissolves in both gasoline and water. The ethanol craze will soon be replaced by another octane booster dictated by the petroleum industry with no research or input from the environmental industry.

We live in a world where we need fuel to remediate a former underground storage tank site. So long as fuel is part of our day-to-day life, our first responsibility should be to prevent repeating old mistakes; and our Government’s responsibility should be to subsequently support the parties that are attempting to do their due diligence as well as protect the public interest and the health of our communities.