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When fire safety concerns or limited available real estate are issues with your need for fuel storage, steel underground storage tanks can provide a solution. Southern Tank manufactures the sti-P3® and ACT-100-U® underground storage tanks.

Underground storage tanks are undergoing another federal mandate phase requiring individual states to choose between two options. One of those options would require mandatory secondary containment for new or replacement installations. Both the sti-p3® and ACT-100-U® tanks would satisfy this secondary containment requirement if purchased as double-wall units. They are both available in single-wall construction as well in sizes ranging from 100 gallons to 20,000 gallons. Double-wall tanks are shipped with a vacuum applied to the interstice. The interstitial monitor pipe also allows for easy leak detection either manually or electronically.

Both tank designs meet or exceed EPA federal regulations for underground petroleum storage. Available internal linings allow water, jet fuels and most chemicals to be safely stored (many chemicals will require secondary containment). Steel underground storage tanks are structurally superior to fiberglass construction, making steel the number one choice for underground tanks.


The sti-P3® is constructed with a pre-engineered factory installed cathodic protection system. A UL-58 steel tank receives a corrosion resistant polyurethane coating. The coating combined with dielectric bushings and sacrificial anodes gives you the peace of mind that your underground tank will be protected against corrosion. A permanently buried reference cell provides an easy and simple method for monitoring the anodes to make sure they are working as designed. Striker plates protect the inside of the tank from internal damage. The sti-P3® is available in sizes from 100 to 20,000 gallons.


The ACT-100-U® is the newest technology in composite tank construction. A steel UL 58 inner tank receives a minimum 70 mils corrosion resistant self-reinforced polyurethane coating. FibreThane Plus has been proven to outperform 100 mils of FRP (fiberglass reinforced polyester) in every respect. FibreThane is environmentally friendly and is not classified as a hazardous material. The 70 mil coating does not require sacrificial anodes thus eliminating the 3-year testing requirement. All ACT-100-U® tanks have dielectric bushings and striker plates and are available in sizes from 1000 to 20,000 gallons.

Both the sti-P3® and the ACT-100-U® can be constructed with multiple compartments. Other construction options include a stainless steel inner tank, custom linings, reverse flanged manways, extensions, sumps, internal ladders, hold down straps, etc. Special openings are also available such as 150# flanges.

When you need to store fuel underground, contact Southern Tank and let us provide you with a steel underground storage tank – structural strength and time-tested reliability.

For more details on the federal guidelines regarding secondary containment and underground tanks click here.