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Underground Storage Tanks and Environmental Risk

Underground Storage Tanks and Environmental Risk

In Canada, early commercial and residential heating systems were fired using fuel oil or diesel fuel. Because of the size of the tanks, it was common to use underground storage tanks (USTs) for fuel storage. The presence of a UST is indicated by the presence of fill ports that are generally flush with the ground surface and vent pipes that are located above grade. USTs can vary in size and are commonly used for the storage of fuel oil, gasoline, diesel, and solvents. Storage tanks that are placed in a basement of a structure are not considered to be a UST. Storage tanks that are placed inside a building or along the exterior of a structure are considered to be aboveground storage tanks (ASTs). ASTs can also vary in size and are commonly used for the storage of waste oil, gasoline, diesel, and fuel oil.

Why are storage tanks an issue?

Older tanks constructed prior to the mid-1980s were made of thin, uncoated mild steel, which is highly likely to corrode over a period of time. These older tanks were usually placed directly into the ground without secondary containment, and as the UST rusts away, the contents of the tank are allowed to escape and discharge into the surrounding soil and/or ground water.

ASTs that are placed along the exterior of a building where surroundings are not maintained properly, can cause an increase of moisture to build-up along the belly of the AST due to overgrown vegetation, which leads to rust-out followed by a discharge of the tank contents.
The presence, or potential presence of USTs and ASTs are common sources of soil contamination in Ontario. If contamination is expected or detected from a storage tank, the tank should be removed prior to causing further subsurface contamination.

Who regulates storage tanks?

In Ontario, the Technical Standards and Safety Authority (TSSA) regulates storage tanks used to store petroleum products. The TSSA registers qualified contractors and inspectors that work with fuel tanks and systems, that by law, are required to be trained and certified as petroleum mechanics. These certified contractors are who you want to retain to conduct repairs, inspections, and tank removals to ensure that the tank is properly examined, and the issue is dealt with in accordance to regulations and protocols.

I have an Underground Storage Tank on my property! How do I remove it?

In order to remove a UST, a qualified and experienced environmental contractor is retained to conduct the tank removal. The removal begins with removal of the remaining tank contents and any vapours are purged from the tank. Once the tank is deemed “clean”, surface coverings and soil in the vicinity of the tank are removed. Once the tank and piping are exposed, the piping is disconnected and removed, followed by removal, shearing, and off-Site disposal of the tank. Subsequently, verification soil sampling of the walls and floor of the former tank nest is conducted to confirm that no soil impacts are present. If there is evidence of potential impacts to ground water, than monitoring wells should be installed followed by the collection of samples for laboratory analyses. Once laboratory results indicate that the remaining material in the vicinity of the former tank meet the applicable Site Condition Standards, the excavated area is backfilled, graded, and restored. Upon completion of the UST removal and a successful soil and/or ground water sampling program, a report is developed and provided to the TSSA for regulatory review and compliance.

How can I minimize risk to the environment while having a tank on my property?

Early detection of a leak and/or spill associated with a storage tank, identifying the source of the release, and assessing the soil and/or ground water conditions in the vicinity of the tank are three important factors. Leaking tanks can have impacts on property value, drinking water wells, and the build-up of vapours in underground structures in close proximity of a tank can cause human health and safety impacts.
In order to minimize risk to the environment, a tank and associated piping must be inspected and maintained regularly. Generally, a tank tightness test is conducted to verify and/or refute if a leak is occurring and proper management of liquid levels can reveal a significant loss of liquid in a short period of time.

If a leak is suspected or confirmed, the source of the release should be minimized immediately. Commence the tank repair/removal process and have the surrounding soil sampled and analyzed for any contaminants of potential concern associated with the released liquid.