Underground Storage Tanks (USTs)

Alternative Fuels and Underground Storage Tanks (USTs)

Introduction

EPA’s underground storage tank (UST) regulations require that tank systems are compatible with the substances stored in them. The use of alternative fuels in the United States is growing, and federal mandates require a significant increase in biofuels production. Many retail facilities, such as gas stations, and private fueling facilities already store and dispense ethanol and biodiesel in their UST systems. Ethanol and biodiesel are commonly blended with gasoline and diesel, respectively, and are referred to by their biofuel percentage of the blend: E10, E15, or B20. These fuels are also available in some retail markets as non-blended biofuels E98 or B100. The development and availability of other alternative fuels, such as isobutanol, are growing rapidly. 

Each alternative fuel or alternative fuel blend has unique chemical characteristics that may be different from those of purely petroleum derived gasoline or diesel fuel. Those chemical characteristics may affect how the fuel interacts with UST system materials. Some materials in some USTs may actually not perform as intended if storing certain fuels or blends and may be incompatible with those fuels. If UST materials are not compatible with substances stored in USTs, releases to the environment can occur. Prior to storing alternative fuels, UST owners and operators should be aware of potential issues and regulations to ensure fuels are stored safely in USTs. 

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2015 Compatibility Requirements

In 2015, EPA revised the underground storage tank (UST) regulations. See below for the 2015 requirements.

Owners and operators must use an UST system made of or lined with materials that are compatible with the substance stored in the UST system.

Compatibility is the ability of two or more substances (for example the tank or piping material and petroleum) to maintain their respective physical and chemical properties upon contact with one another. These substances need to remain compatible for the design life of the tank and under conditions likely to be encountered in the UST.

Beginning on October 13, 2015 owners and operators must notify their implementing agency at least 30 days prior to switching to one of the following:

  • Regulated substances containing greater than 10 percent ethanol;
  • Regulated substances containing greater than 20 percent biodiesel; or
  • Any other regulated substance identified by the implementing agency.

This notification gives the implementing agency an opportunity to inquire about the compatibility of the UST system before the owner and operator begins storing the regulated substance.

In addition, owners and operators storing one of these regulated substances must meet one of the following:

  • Demonstrate compatibility of the UST system (this includes the tank, piping, containment sumps, pumping equipment, release detection equipment, spill equipment, and overfill equipment) by using one of the following options:
    • Certification or listing of UST system equipment or components by a nationally recognized, independent testing laboratory for use with the regulated substance stored
    • Equipment or component manufacturer approval – this approval must be in writing, indicate an affirmative statement of compatibility, specify the range of biofuel blends the equipment or component is compatible with, and be from the equipment or component manufacturer
  • Use another option determined by the implementing agency to be no less protective of human health and the environment than the two options above.

Owners and operators must maintain records that document compliance with the compatibility requirement if they store regulated substances containing greater than 10 percent ethanol, greater than 20 percent biodiesel, or any other regulated substance identified by the implementing agency. These records must be maintained for as long as the UST system is used to store one of these regulated substances.


2011 Guidance on Demonstrating Compatibility

EPA's 2011 guidance provides options for UST owners and operators to use in complying with the federal compatibility requirement for UST systems storing gasoline containing greater than 10 percent ethanol or diesel containing greater than 20 percent biodiesel.

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For more information, contact Ryan Haerer at haerer.ryan@epa.gov or 202-564-0762.

About Alternative Fuels

You will need Adobe Reader to view some of the files on this page. See EPA’s About PDF page to learn more.

These resources provide general information about biodiesel and ethanol.

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Biodiesel and Biodiesel Blends

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Ethanol and Ethanol Blends

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Ensuring Compatibility of Alternative Fuels with USTs and Converting Equipment to Store Alternative Fuels

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These resources provide information regarding UST system compatibility with biodiesel, ethanol, and other alternative fuels. They also provide information on how to correctly convert UST systems and store biodiesel, ethanol, and other alternative fuels.

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Compatibility of Biodiesel and Biodiesel Blends

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Compatibility of Ethanol and Ethanol Blends

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Converting Equipment to Ensure Compatibility

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Safety and Handling of Alternative Fuels; Cleaning Up Releases

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These resources provide information on safety, handling, releases, and cleaning up releases of alternative fuels.

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Biodiesel and Biodiesel Blends

  • Environmental and Safety Information (PDF) (1 pg, 24 K)
    This fact sheet, developed by the National Biodiesel Board, presents information on biodiesel's biodegradability, oral and skin toxicity, aquatic toxicity, and flash point.
  • Toxicology, Biodegradability and Environmental Benefits of Biodiesel (PDF) (5 pp, 13 K)
    This paper presents the results of research conducted at the University of Idaho's Department of Biological and Agricultural Engineering on the toxicity, biodegradability, and emissions of biodiesel.
  • Biodiesel Material Safety Data Sheet (PDF) (3 pp, 43 K)
    This Material Safety Data Sheet, prepared by the National Biodiesel Board, presents detailed information on storing, handling, safety, and regulatory status of biodiesel.
  • Fuel Quality and Performance Guide (PDF) (20 pp, 463 K)
    Created by the Iowa Renewable Fuels Association, this guide provides detailed advice on buying, storing, and handling biodiesel. It includes ASTM specifications, a list of additional resources, and a troubleshooting checklist.
  • Keeping Water Out of Your Storage System (PDF) (13 pp, 192 K)
    Prepared by the Steel Tank Institute, this resource discusses ways in which water can enter an underground storage tank (UST) system, economic impacts of water intrusion, and methods for the protection of UST systems against water intrusion. Microbial contamination and other issues related to storing ethanol and biodiesel blends are discussed.
  • Phytoremediation of Petroleum Diesel and Biodiesel Contaminated Soil
    This Web page contains an abstract summarizing research conducted by the USDA Natural Resources Conservation Service in partnership with the Illinois State University Department of Agriculture regarding remediation of petroleum diesel- and biodiesel-contaminated soil. The Web page includes a link to download a PDF document with additional details on the research.

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Ethanol and Ethanol Blends

  • Advisory Guidance: Emergency Response Involving Ethanol and Gasoline Fuel Mixtures (PDF) (2 pp, 135 K)
    This fact sheet, developed by the U.S. Department of Transportation's Pipeline and Hazardous Materials Safety Administration, presents information on safety procedures and chemical properties of ethanol blends.
  • A Circle Vicious: What Do We Know About the Other Oxygenates?
    Published in L.U.S.T.Line, a technical newsletter for underground storage tank (UST) stakeholders, this article presents information on ether oxygenates and ethanol. Remediation technologies for ethanol cleanup are discussed.
  • E85 Safety Concerns
    Developed by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy as part of the E85 Fleet Toolkit, this Web page includes information and links to resources pertaining to E85 safety concerns.
  • International Chemical Safety Card
    Vermont Safety Information Resources, Inc. developed this Web page which includes detailed ethanol safety information including symptoms, first aid, firefighting strategies, and routes of exposure.

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Corrosion of Metal Components in USTs Storing Diesel and Gasoline-Ethanol Blends

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Corrosion has been commonly reported in USTs storing diesel fuel and gasoline-ethanol blended fuels.  The corrosion generally appears in different areas of the UST system for each fuel.  When storing diesel fuel, corrosion generally appears on metal components inside USTs.  When storing ethanol blended fuels, corrosion generally appears in sumps.  Instances of this corrosion began appearing about a decade ago.

The corrosion in USTs storing emerging fuels discussed here does not violate federal UST requirements.  The federal UST regulation requires UST owners have corrosion protection for their UST system metal components in contact with the ground.  But corrosion protection is not required for metal components inside USTs or in sumps.  

However, UST owners and operators must ensure corrosion does not affect the functionality of their equipment.  If UST equipment does not function as intended, it may violate the federal UST regulation or lead to releases into the environment.  Owners and operators should contact their state UST implementing agencies because they may impose requirements more stringent than the federal regulation.  

Corrosion of Internal Components in USTs Storing Diesel Fuel

EPA conducted research on 42 actively operating underground tanks storing diesel fuel at facilities all across the United States and found that 83 percent (or 35 USTs) exhibited moderate or severe corrosion of metal components inside the tank system.  EPA’s July 2016 report discusses that research.  Industry provided invaluable assistance to EPA in research design, operational coordination, and report reviews over the course of the research effort.  EPA will continue to coordinate with industry to understand the corrosion issue and identify solutions.  

EPA cannot project the actual percentage of USTs storing diesel that are affected by corrosion nationwide.  However, this could be a widespread and potentially significant problem for owners of underground tanks storing diesel fuel. 

The corrosion may cause metal components inside both steel and fiberglass UST systems to corrode.  This can possibly shorten the lifespan or affect the serviceability of components, including limiting the movement of floats on automatic tank gauging systems, operability of mechanical devices designed to prevent the chance of overfilling the tank, or ability of valves to shut off flow of product in the event of a release.  Corrosion may cause dispenser filters to clog and be replaced more frequently.  Corrosion could potentially limit the proper functionality of sheer valves or equipment designed to test for leaks in fuel product lines.  EPA recommends UST owners check for corrosion in their tank systems storing diesel fuel, and if they find corrosion, repair or replace equipment as necessary to ensure proper functionality. 

Other Resources

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Corrosion in Submersible Turbine Pump Spaces in USTs Storing Ethanol Blended Fuels

External corrosion is commonly found coating metal components in the submersible turbine pump spaces (sumps) of USTs storing gasoline blended with ethanol.  This type of corrosion can be caused by bacteria through a process called microbiologically-influenced corrosion and may impact the serviceability or functionality of equipment in the sumps.  The information below may be helpful to minimize corrosion in sumps storing ethanol blended fuels. 

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