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Storage Tanks Versus Floodwaters – A Guide

How to Prepare, Protect, and Recover Underground and Aboveground Tanks Before and After Severe Weather – 

When floodwaters rise, your storage tanks could become your biggest liability. From tank displacement and environmental contamination to costly operational downtime, extreme flooding can trigger a cascade of problems. Underground Storage Tanks (USTs) and Aboveground Storage Tanks (ASTs) face significant risks when hurricanes, heavy storms, or rising waters breach your site perimeter.

But proactive preparation, smart design, and careful recovery planning can put you in control long before—and after—the storm hits. This practical guide provides underground and aboveground tank operators with the tools to fight back and maintain system integrity when it matters most.

Understanding the Threat: Why Floodwaters Endanger USTs

USTs contain both fuel and air inside a closed system. During a flood, water fills the space around the tank, adding hydrostatic pressure. Like a beach ball held underwater, the air inside makes the tank buoyant—pushing it upward through the ground. This can cause:

  • Tank displacement or surfacing
  • Cracking of tanks or piping
  • Product leaks and environmental contamination
  • Electrical system damage and system failure
  • Long-term erosion or soil shifting around the tank

As severe weather becomes more common in formerly low-risk areas, preparing now is critical even if your facility hasn’t flooded in the past.

Designing Against Disaster: UST Flood Protection Before It Happens

If your UST system is located near water or in flood-prone areas, consider these protective installation strategies:

  • Increase Burial Depth: Deeper placement and added pavement/pad weight can counter buoyancy.
  • Anchor Your Tanks: Installing tank anchors or deadman systems helps physically hold the tank in place.
  • Vent Pipe Extensions & Shutoff Valves: Install upgrades that prevent floodwater and debris from entering.
  • Check Local Conditions: Follow tank manufacturer recommendations and evaluate site-specific soil and drainage.

Before the Storm: Flood Preparedness for UST Systems

When flooding is forecasted—from hurricanes to heavy rainfall events—use this preparation checklist to protect your tanks:

  • Shut Off All Power: Disconnect electricity to dispensers, pumps, turbines, leak detection systems, and other equipment.
  • Inventory Fuel and Measure Water Levels: Take accurate readings to identify any future leaks or displacement.
  • Fill Tanks with Product: A full tank is heavier, reducing the chance of floating. Never fill with water.
  • Tightly Secure All Openings: Cap and lock all fill ports, spill buckets, sump lids, and access points.
  • Check Spill Bucket Plunger Seals: Ensure seals are in place and operational to prevent water from entering.
  • Close Shear Valves on Pressurized Lines
  • Temporarily Cap Vent Pipes: Helps prevent water intrusion. (Remember to remove caps before restart.)
  • Weigh Down Tank Area If Possible: Place sandbags, dumpsters, or heavy containers over tank areas for added resistance.

Minimal Flooding? Take These Steps

If floodwaters remain below critical levels:

  • Keep system power OFF throughout the storm event.
  • Secure or inspect vent pipes and above-ground components for possible damage.
  • Monitor conditions and delay restart until flooding has fully passed.

Severe Flooding? Respond Carefully Before Restart

Once officials say it is safe to return and flooding has receded:

✔ Check Structural Integrity and Movement: Inspect the tank pad area and surrounding soil for cracking, gaps, or tank movement. If any structural anomalies are observed, contact a qualified contractor before proceeding.

✔ Use Leak Detection Tools: Use your ATG to test for leaks. For high water, use a manual gauge with water-finding paste to check for product loss or water inside.

✔ Pump Out Water and Debris: Remove standing water and inspect each tank individually. If water is found, consult disposal guidelines.

Important: Ethanol-blended fuels are sensitive to even small amounts of water. Phase separation can occur rapidly, making the fuel unusable. Diesel and conventional fuels can temporarily tolerate small amounts—but this is not recommended long-term.

✔ Tightness Testing & Equipment Checks: Conduct a tightness test on all tanks and lines:

  • Inspect and clean sumps—including those under dispensers and fill areas
  • Check pumps, valves, fill caps, vent pipes, and piping connections
  • Confirm leak detection systems are working
  • Test cathodic protection and bottom-flatness for fiberglass tanks

Out of Fuel?

Turn off all submersible turbine pumps (STPs) to prevent severe damage caused by dry running.

Temporary Closure Guidance

If you cannot safely resume operations:

  • Maintain corrosion protection systems during downtime.
  • Secure, isolate, and document all equipment.
  • Keep vent lines open if closure exceeds three months.
  • Continue spill monitoring, inspections, and financial responsibilities per local and state requirements.

ASTs vs. Floodwaters: Safety Considerations for Aboveground Storage Tanks

ASTs face different—but no less serious—challenges during storms and flooding. Operators should:

  • Inspect Tanks and Piping for Visible Damage before restart.
  • Ensure Tanks Are Water-Free prior to fueling or restocking.
  • Have Emergency Fire and Spill Response Equipment On-Site
  • Check All Vents, including emergency and primary systems, for obstructions like nests or debris.
  • If necessary, schedule a professional inspection before restarting full operations.

Prepare Now with an Emergency Response Plan

Proactive planning saves time, protects the environment, and avoids costly compliance violations. Ensure your site has:

  • A written spill containment and emergency response plan
  • Site-specific flooding procedures and evacuation protocols
  • Designated emergency contacts and agency notification procedures
  • Regular staff training and drills

Floods may be inevitable—but costly damage isn’t. The key to protecting your facility’s underground and aboveground tanks is preparation, vigilance, and informed action during critical moments. With the right strategy in place, storage tanks can withstand even the worst weather, and your operations can return to normal more quickly and safely.

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For questions or assistance contact Karen Buniak, VP Business Development at karenb@ttienv.com or Bill Stafford, Senior VP Contracting & Construction at bills@ttienv.com