In today’s world, underground storage tanks (USTs) contain an assortment of products ranging from gasoline to diesel to biofuels to hazardous chemical substances. Because of the wide swath of fuels and chemical substances available, it is imperative for tank owners to ensure that the tank itself is compatible with the substance stored. Storing certain fuels that are incompatible with the tanks threatens the overall integrity of the UST. 

Compatibility issues are not new to the UST community. Over 30 years ago, the U.S. Environmental Protection Agency (EPA) and states began the tedious process of phasing out bare steel tanks because of the growing concern that these tanks were corroding with time and leaking. It was not unusual for UST systems to break down and release product that subsequently led to significant environmental cleanups and costly enforcement penalties.

After the bare steel tank ban, UST owners have a more recent corrosion hurdle to overcome—storing biofuels. Sure, tanks are built to last much longer these days and likely are jacketed or made of fiberglass. However, over the last decade, blended fuels have become commonplace as alternative fuels with different chemical properties have been discovered and put on the market. These include biofuels E10 (contains 10 percent ethanol and 90 percent gasoline) and B20 (contains 20 percent biodiesel and 80 percent petroleum diesel). To make compatibility matters more complicated, it is projected that the fuel market will continue to unveil more biobased fuel varieties over the next few years.

What does it mean to be compatible?

The EPA requires that all UST systems (including tank components) be made of or lined with materials compatible with the substances stored. Under 40 CFR 280.12, the EPA defines compatibility as the ability of two or more substances to maintain their respective physical and chemical properties upon contact with one another for the design life of the tank system under conditions likely to be encountered in the UST.

The definition of compatibility is quite simple in theory, but it may be more complicated in practical terms. How does a tank owner actually know if the tank is compatible, after all, tanks are built to last for decades, yet the fuel market keeps evolving?

To combat this problem, the EPA, after nearly 30 years of regulatory dormancy, updated the federal requirements for USTs and added new compatibility requirements to assist tank owners and operators.

Mastering compatibility compliance

Because of these emerging fuels and the traditional longevity associated with USTs, EPA’s 2015 regulations now require tank owners to notify, demonstrate compatibility, and maintain records.

The following tank owners must notify the implementing state agency or the EPA within 30 days when:

• Switching to a regulated substance containing greater than 10 percent ethanol;
• Switching to a regulated substance containing greater than 20 percent biodiesel; or
• Switching to another regulated substance identified by the specified implementing agency

In addition to providing notification to the regulatory authorities that the tank’s contents have been substituted to one of the above products, tank owners also have the burden of demonstrating compatibility. To demonstrate that the tank and all of the components are indeed compatible with the substance stored, tank owners must:

• Verify compatibility with the certification or listing of the UST system equipment by a nationally recognized, independent testing laboratory; or
• Verify in writing from the manufacturer that the equipment or component is compatible and provide the potential range of compatible biofuel blends.

Lastly, tank owners must keep records. The 2015 regulations specify that any tank owner storing regulated substances greater than E10, B20, or a substance identified by the implementing agency, must keep records showing that the UST system is compatible with those substances. The records must be kept and maintained for as long as the tank stores the substances.

Additional must knows

Some states have their own state program approval from the EPA to implement their own UST regulations. It is critical that UST owners check with their state implementing agency for different or more stringent compatibility requirements than the federal regulations.

As technology continues to advance and the future of blended fuels becomes ordinary, it is likely that some older tanks will need to be retrofitted with newer, compatible equipment, if the tank owner elects to store a higher level biofuel blend. Tank owners should consider upgrading their equipment as an initial investment to save money in the long run should their tank leak or they face staggering compliance penalties, or both.