It may seem counterintuitive that an underground storage tank could float. After all, these structures are not only buried deep 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.

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 because the air within the bottle exerts an upward force. This phenomenon is known as buoyancy, and the same principle applies to underground storage tanks. If floodwaters reach a particular stage or the water table rises enough, the air inside the underground storage tank will begin exerting upward force. Since USTs often contain a large volume of liquid, the buoyancy force can be powerful and 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 increase, deadman anchors provide an alternative. Made of reinforced concrete, these anchors will help prevent floatation and 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. Then, the tank is anchored to the bottom hold-down slab, providing a downward force that counteracts buoyancy and offers more stability for the UST.

Have questions about how underground storage tanks float or what to do when it happens, contact us now!