Introduction

Countless retail facilities, such as gas stations, and non-retail fueling facilities store biofuels, ethanol, and biodiesel in their UST systems. Emerging fuels include biofuels, like ethanol, biodiesel, and butanol. It also includes new formulations of petroleum-based fuels, like ultra-low sulfur gasoline and ultra-low sulfur diesel, renewable diesel, and combinations of several kinds of fuels. Since biofuels and biofuel blends have different properties than conventional fuels, they display differences in environmental behavior. This can lead to concerns over underground storage tank (UST) compatibility and the likelihood of corrosion. This Fact File gives a detailed look at the connection between emerging fuels and USTs. It explains internal and external corrosion potential with USTs and how to demonstrate compatibility.

Background

The federal UST regulation requires that owners have corrosion protection for their UST systems’ metal components in contact with the ground. However, corrosion protection is not required for metal components inside USTs or in sumps. Corrosion in USTs by itself is not a direct violation of federal UST requirements. But UST owners and operators must ensure corrosion does not disturb equipment functionality. If UST equipment does not function like it should, it may violate the federal UST regulation. Or it can lead to harmful releases into the environment.

Ensuring UST systems are compatible with the substances they store is crucial to preventing releases of regulated substances. This means that the WHOLE UST system (tanks, pumps, ancillary equipment, lines, gaskets, and sealants) need to be compatible with the fuel stored. As of October 2015, if you store regulated substances with over 10 percent ethanol, more than 20 percent biodiesel, or other substances identified by your implementing agency, you must keep records showing that your UST system is compatible with those substances. You need to keep these records for as long as you store these substances.

Internal UST corrosion with emerging fuels

Emerging fuel release situations arise from the use of incompatible materials in equipment, such as storage tanks, hosing, piping, and dispensers. Particularly, older UST system components may not be compatible with biofuels. This could include sealing and jointing materials for pipe runs and turns. The solvent nature of biofuel can scour the sediment, sludge, rust, and scale accumulated in a UST system deposited from formerly stored conventional fuels. The scoured material is especially bad because it may expose previously plugged pinholes in storage tanks formed due to corrosion.

Also, leak detection equipment can fail if it is incompatible with the biofuel being stored. The increased conductivity of biofuels, compared to petroleum hydrocarbons, can cause metal corrosion. Common examples of capability issues include:

• Zinc, brass, lead, and aluminum are sensitive to high-blend alcohol fuels.
• Plated steel and lead-based solder are not compatible with E85.
• Natural rubber, cork, leather, polyurethane, polyvinyl chloride (PVC), polyamides, methyl-methacrylate plastics, and some kinds of thermoset and thermoplastic polymers may degrade in high-blend alcohol fuels.
• Certain elastomers, metals, and plastics are not compatible with B100, whereas biodiesel blends of 20 percent or lower usually have a more reduced effect on these materials.

Internal corrosion can decrease the lifespan or affect the serviceability of components. This may include limiting the movement of floats on automatic tank gauging systems, reducing operability of mechanical devices meant to prevent overfilling the tank, or hurting the ability of shear valves to shut off flow of product when a release happens

Demonstrating compatibility

Some biofuels could affect compatibility and functionality of UST equipment. Biofuels with ethanol can affect the amount of water absorbed or retained in fuel. A few kinds of release detection equipment rely on advanced technologies to evaluate product levels in USTs. These methods for leak detection could be negatively impacted by ethanol’s ability to dissolve and mix with water. This could prevent them from functioning correctly as a release detection device in fuels blended with ethanol. If you find that you cannot demonstrate capability for your entire UST system when you wish to store biofuels, you have three options:

1. Use targeted retrofits of precise equipment to upgrade your existing UST systems.
2. Install a new UST system that can show compatibility with the substance to be stored. When installing a new system for this purpose, an owner should request equipment that is compatible with regulated substances with more than 10 percent ethanol and 20 percent biodiesel.
3. Not store the substance. This will ensure no releases happen due to substance incompatibility.

Applicable laws & regulations

40 CFR 280 – Technical Standards and Corrective Action Requirements for Owners and Operators of Underground Storage Tanks (UST)

Related definitions

“Biodiesel” means a diesel fuel made from vegetable oils, animal fats, or recycled greases.

“Biofuel” means a transportation fuel like ethanol and biomass-based diesel fuel that are made from biomass resources.

“Ethanol” means a clear, colorless alcohol made from an assortment of biomass materials called feedstocks.

“Renewable Diesel” means non-ester-based diesel fuels derived from nonpetroleum resources that can be processed in conventional refineries separately or with petroleum stocks using hydrotreating methods.

“Solvent” means a liquid that is a single chemical, or a mixture of chemicals used to dissolve a substance or material

Key to remember

Keep in mind that there are notification requirements when you switch to emerging fuels. You must notify your implementing agency at least 30 days before switching to any of the following:

• Regulated substances with over 10 percent ethanol
• Regulated substances with over 20 percent biodiesel
• Any other regulated substance recognized by your implementing agency

In your notification letter include the following:

• The regulated substance you intended to store,
• The start date of when you will store it,
• Your UST system identification number,
• Compartment number if applicable,
• Facility address, and
• Phone number so your UST implementing agency can contact you with any possible questions.

Real world example

USTs aren’t the only tanks that face emerging fuel leak and corrosion issues. Above-ground storage tanks are just as vulnerable. In 2018, the Washington Department of Ecology fined a Lewiston-based fuel retailer $189,000 for spilling 3,840 gallons of biodiesel. It came from a corroded underground pipe at a bulk oil plant. The fuel contaminated surrounding soil and groundwater. It oozed into the Columbia River. The company had a 20,000-gallon above-ground storage tank connected to the corroded pipe which they failed to monitor levels properly. On top of the fine, the company needs to reimburse the state $213,400 for its costs to respond to the spill. This is a situation that could have easily been prevented if correct fuel level monitoring was in place in the tank. Try not to be like this company. Never turn a blind eye to corrosion and fuel issues with a tank. If you correctly comply with tank regulations related to biofuels, you should avoid being like this company.