Building in flood-prone areas requires careful consideration of both safety standards and insurance implications. These considerations apply not only to homes and building structures, but even to chemical storage systems.
If you build your system, including your tanks and structures, above the flood zone, you're in great shape. However, if you build within a flood zone, it is critical to know and follow the International Building Code’s regulations.
The International Building Code (IBC), which California adopts as the California Building Code (CBC) with some modifications, provides specific guidelines for structures in flood zones.
According to Chapter 16 of the IBC/CBC, any structure designed in a flood zone must follow ASCE 24-14 guidelines. These guidelines present building owners with two primary options.
Base flood elevation (BFE) is the level that surface water will likely reach during a base flood. “Base flood” refers to a flood that has a 1% chance of being either equaled or exceeded in a given area in a given year.
Put another way, a BFE shows how high water may rise during a 100-year flood (i.e., a flood that has a 1% chance of happening in any given year).
Design Flood elevation is the Base Flood Elevation (BFE) plus freeboard, as required by the 2022 CBC and ASCE 24-14.
Be sure to set your building high enough on a path so it sits above the Design Flood Elevation (DFE) established by FEMA, 2022 CBC and ASCE 24-14. When your structure is positioned above this elevation, no special floodproofing measures are required.
If elevation above the DFE isn't feasible, floodproofing becomes necessary. The building must be floodproofed up to the DFE level. For example, if your building sits two feet below the BFE, you must implement floodproofing measures for those two feet, plus the required freeboard per CBC 2022 and ASCE24-14, to effectively protect the structure. The required freeboard depth is based on the building’s risk category.
The same requirements apply to minor structures and any equipment that service the main building. This includes:
These components must either be elevated above the DFE, or properly floodproofed if positioned below the BFE.
If you’re in a flood zone, you must have proper flood insurance for your building, chemical tank system, and other auxiliary structures and equipment. Your building's position, relative to the BFE, directly impacts your insurance requirements.
Structures positioned above the BFE may qualify for exemption from flood zone classification. This exemption can be obtained by filing appropriate documentation with FEMA. Buildings below the BFE will require flood insurance coverage.
Proper tank restraint systems are critical in flood zones, because polyethylene tanks float. We've seen floods in New Orleans and other places where the plastic chemical storage tanks floated so much that they pulled the cables right out of the ground.
Be sure to design your chemical storage system with the following considerations in mind:
Design Purpose:
Be aware of key limitations during the design phase of your chemical tank. For example:
For tanks subject to seismic or flood conditions (especially below BFE), stronger restraint systems like cages may be necessary, as standard cable restraints may not be adequate for these loading conditions.
Understanding and adhering to flood zone requirements under the IBC is essential not only for regulatory compliance, but also for protecting your investment and potentially reducing insurance costs. Whether you choose to elevate your structure or implement floodproofing measures, ensuring that your building and equipment meet these standards is a critical step in the development process.
Design with confidence — talk to a chemical storage tank engineer today.