What Is an Underground Storage Tank (UST)?

Underground Storage Tanks (USTs) are common systems used for storing petroleum products, such as gasoline or diesel, and other hazardous substances. Their management and oversight are subjects of public interest due to their potential impact on environmental safety, particularly concerning soil and groundwater quality.

Defining Underground Storage Tanks

An Underground Storage Tank (UST) is defined by regulatory bodies as a tank and any underground piping connected to the tank that has at least 10 percent of its combined volume underground. These systems are extensively used across the United States to store a variety of substances, with petroleum products like gasoline, diesel fuel, and heating oil being among the most common. Beyond fuels, USTs can also hold chemicals, solvents, and other hazardous materials used in industrial processes or commercial operations. Historically, older USTs, particularly those made of bare steel, were prone to corrosion and leaks over time. These leaks could release stored substances into the surrounding soil and groundwater, posing significant environmental and health risks. The potential for widespread contamination from leaking tanks led to the development of comprehensive regulations designed to prevent such incidents.

Components of a UST System

A UST system comprises several integral parts for storing and dispensing regulated substances. The tank itself is constructed from materials such as fiberglass, steel, or a combination, often with protective coatings to resist corrosion. A network of piping connects to the tank, including supply lines that carry fuel to dispensers, return lines for vapor recovery, and vent lines that allow air to enter and exit the tank during filling and dispensing.

The system also includes essential ancillary equipment designed for safety and environmental protection. Dispensing pumps are a visible component, facilitating the transfer of substances from the tank to vehicles or other containers. Systems are equipped with release detection mechanisms, which may include automatic tank gauging that continuously monitors tank levels and temperatures, or vapor monitoring systems that detect chemical vapors in the soil around the tank. Spill prevention equipment, such as spill buckets around the fill pipe, catches drips or small spills during delivery, while overfill prevention devices, like automatic shutoff valves, prevent tanks from being filled beyond their capacity.

Regulatory Framework for USTs

The regulatory environment governing Underground Storage Tanks is primarily established at the federal level, with significant implementation and enforcement responsibilities delegated to state agencies. The U.S. Environmental Protection Agency (EPA) sets the foundational rules for USTs under Subtitle I of the Resource Conservation and Recovery Act (RCRA). This federal mandate aims to prevent and detect leaks from USTs, ensuring the protection of groundwater and surface water from contamination. State environmental agencies play a crucial role in administering these federal regulations, often developing their own programs that are at least as stringent as the EPA’s requirements. These state programs are responsible for permitting, inspecting, and enforcing compliance among UST owners and operators within their jurisdictions.

Key Compliance Requirements

Owners and operators of Underground Storage Tanks must adhere to a comprehensive set of compliance requirements throughout the system’s operational life.

Release Detection

One primary obligation involves implementing effective release detection methods, which means regularly monitoring the tank and piping for any signs of leaks. This can include employing automatic tank gauging systems that alert operators to potential losses, or conducting periodic tightness tests on the piping to ensure its integrity.

Spill and Overfill Prevention

Another requirement focuses on spill and overfill prevention, necessitating the use of equipment like spill buckets at the fill pipe and overfill protection devices within the tank. These measures are designed to prevent accidental releases during the delivery of substances.

Corrosion Protection

Corrosion protection is also mandatory for steel tanks and piping, often achieved through cathodic protection systems or corrosion-resistant materials, to prevent degradation that could lead to leaks.

Record Keeping and Reporting

Maintaining meticulous records is an ongoing compliance task, encompassing documentation of release detection monitoring results, maintenance activities, and repair logs. Owners are also required to report specific incidents, such as suspected or confirmed releases, to regulatory agencies promptly.

Operator Training

Designated operators must undergo training to ensure they are knowledgeable about UST operation, emergency procedures, and regulatory responsibilities.

Financial Responsibility

Demonstrating financial responsibility is a significant requirement, where owners must prove they have the financial capability, often through insurance or other mechanisms, to cover the costs of potential cleanup and third-party damages in the event of a release.

UST Management Phases

The lifecycle of an Underground Storage Tank system involves several distinct management phases, each with specific regulatory considerations.

Installation

The initial phase is installation, which requires adherence to strict construction and placement standards, often involving certified installers and necessary permits from local and state authorities.

Operational Phase

Following installation, the system enters its operational phase, during which it is actively used for substance storage and dispensing.

Modification or Upgrade

Should significant changes be required, the modification or upgrade phase addresses alterations such as adding new piping or updating monitoring equipment, which also necessitates specific regulatory approvals and oversight to ensure continued compliance.

Temporary Closure

When a UST is temporarily taken out of service, it enters a temporary closure phase. During this period, certain monitoring requirements may still apply, and precautions must be taken to prevent releases.

Permanent Closure

The final stage is permanent closure, where the UST system is permanently removed from service, either by physical removal from the ground or by filling it in place with an inert material like sand or concrete. This phase typically requires a site assessment to confirm that no contamination occurred during the system’s operational life.