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How to Prevent Underground Storage Tank Flotation

July 22, 2016 | Posted in Underground Storage Tanks

It may seem counterintuitive that an underground storage tank could float. After all, these structures are not only buried under the ground, but they are also incredibly heavy. So why would you need to worry about flotation? The culprit in this situation is buoyancy. Learn everything you need to know about underground storage tank flotation and how to prevent it in today’s blog, below.

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How do underground storage tanks float?
To understand the buoyancy of USTs, think about a water bottle that has been half-filled with water. If you throw the bottle into a body of water, it will float due to the fact that the air within the bottle exerts a strong upward force. This phenomenon is known as buoyancy and the same principle applies to underground storage tanks as well. If floodwaters reach a certain stage or the water table rises enough, then the air inside of your UST will begin exerting upward force. Since USTs often contain a large volume of liquid, the force of the buoyancy can be incredibly strong and can even potentially cause your UST to break through the earth above! Luckily, there are a few things you can do to help prevent this from happening.

Preventing underground storage tank floatation

  • Bury your UST deeper. By burying your UST more deeply underground, the weight of the backfill will generate more downward force that will counteract the effects of buoyancy.
  • Use deadman anchors. In cases where burial depth can’t be increased, deadman anchors provide an alternative. Made of reinforced concrete, these anchors will help prevent floatation and also provide additional stability.
  • Use a thick paving slab. When placing paving slabs on top of the earth above your UST, using a thicker grade paving slab will create more downward force and help keep your UST in place.
  • Install a bottom hold down slab. This concrete paving slab is installed underneath your underground storage tank. The tank is then anchored to the bottom hold down slab which provides a downward force that counteracts buoyancy and also offers more stability for the UST.

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