Underground Storage Tank Removal - Montana Dept of Environmental Quality

What is the Underground Storage Tank Abandonment Process

Understanding the Underground Storage Tank Abandonment Process

The underground storage tank abandonment process is a complex series of construction and demolition tasks that now require intensive environmental regulation and oversight. An underground storage tank, or “UST,” is a large vessel, usually comprising steel or fiberglass, that serves to hold large volumes of liquid. These tanks typically hold petroleum products, such as gasoline or oil. Similarly, USTs frequently contain other non-petroleum hazardous substances, such as solvents and wastewater. And each UST system typically includes piping and dispenser ports that trend above the ground surface. Nonetheless, all of the recognizable environmental conditions with UST systems are underground. Updated June 7, 2021.

Underground Storage Tank Removal - Montana Dept of Environmental Quality

Underground Storage Tank Removal – Montana Dept of Environmental Quality

Reasons for Removal

Unless the tank is in good condition and actively in use for storage, environmental professionals always recommend performing the underground storage tank abandonment process. In fact, the sooner the better. This is because the longer a UST exists underground, the more likely soil contamination occurs. And typically, this means the costlier the contamination remediation process. There are several reasons why excavation needs to occur prior to abandoning the tank and its components. Whatever the reason happens to be, the UST removal process will be generally similar.

UST Abandonment (source USPS Office of Inspector General)

UST Abandonment (source USPS Office of Inspector General)

Out-of-Use Tanks

Sometimes a property owner simply does not use their UST anymore. Perhaps their business no longer requires this type of underground storage tank. Or, maybe a newer UST is in use, and the old one remains underground. Nonetheless, unusable tanks pose a threat to the environment, and best practices and laws suggest removal. For instance, in California, if a UST is out of use for longer than one year, it must be permanently abandoned. It is possible that a property owner unwittingly comes into possession of an old underground storage tank that happens to already exist on the property.

Leaking Tanks

In some cases, the underground storage tank may be discoverable during a Phase 1 Environmental Site Assessment (ESA). And the surrounding soil may comprise contamination according to the Phase 2 Environmental Site Assessment. This is essentially another example of a UST that comes with a site. But this situation presents the additional problem of contamination to the subsurface. For instance, soil-gas, soil, and groundwater. In this case, environmental professionals typically advise that the UST undergo excavation and disposal, prior to commencing with contamination remediation. In fact, some smaller extents of subsurface contamination from underground gasoline tanks may undergo remediation by excavation during the UST removal process. Ultimately, the first step to proceed would be to have a professional geologist to prepare a soil management plan and remedial action plan outlining the clean-up process.

Replacing a Tank

In this scenario, an older and obsolete UST may require removal and replacement in order to operate in compliance with new regulations. For instance, modern upgrades include double- or triple-wall tanks, which are now the regulation requirements in most jurisdictions. In fact, a recent law in California requires that all single-wall USTs be permanently by the year 2025. Upgrading UST systems may also include enhancements to the product piping and dispenser system. And these improvements further reduce the likelihood of a leak. In all these examples, a professional geologist can make sure the removal process is straightforward, safe, and compliant with all regulations.

Underground Storage Tank Abandonment Process & Permit

Underground Storage Tank Abandonment Process & Permit

The Underground Storage Tank Abandonment Process


Before getting the permits for underground storage tank abandonment, certain requirements must be in place. This includes the approval to conduct the necessary confirmation soil sampling, as well as the drilling. Additionally, there are likely to be prerequisites permits for the final UST removal permit. For instance, drilling for confirmation soil sampling may require a drilling permit via the local environmental health department. Moreover, plans and details will be necessary. These can comprise a series of site maps that note the locations of all UST excavations. And the information must describe the size, history, content, and status of the tanks on-site. Furthermore, the applicant must submit a copy of the contractor’s license for the company leading the project. Lastly, the application and supporting documents must get clearance and approval from to the appropriate plan check office for approval. For instance, the local fire and hazmat department, or building department.


The California Environmental Protection Agency (CalEPA) is the regulatory authority responsible for overseeing the state-wide implementation of regulations regarding underground storage tank abandonment. CalEPA delegates this responsibility at the County-level to Certification Unified Program Agencies (CUPAs). For example, in Los Angeles County, the Fire Department’s Health Hazardous Materials Division is responsible for ensuring that professionals follow the standards. And these standards include those set forth by CalEPA, the Department of Toxic Substances Control (DTSC), the State Water Resources Control Board (SWRQCB), and others. Thus, in Los Angeles, the first step is to apply for a Division 5 Permit from the local LA City Fire Department.

Permit application process (source City of Hayward, California)

Permit application process (source City of Hayward, California)

Abandonment in Place

Although rare, there are special cases where it is necessary to leave the tank as is, and fill it with concrete in order to stabilize it. This is only allowable if the tank is inaccessible for removal. For instance, if the UST is directly under a building or retaining wall. In such a case, the placement of the UST is necessary to maintain structural integrity. Under these conditions, a special permit becomes necessary, in addition to the original UST abandonment permit. And these processes also involve on-site inspections by the appropriate CUPA.

Fieldwork for the Underground Storage Tank Abandonment & Removal Process

Regardless of the reason the tank is being removed, there are standard procedures that will be followed to complete the UST removal process. There are many steps involved that require applying for permits, navigating the regulatory authorities, testing the soil, and possible remediation if the site proves to be contaminated. Fortunately, if you find a contractor that is a good fit for your project, the process will be much simpler. The right contractor will be able to handle all the regulatory correspondence and permitting along with the physical removal of the UST.

Preparing the Site for UST Removal

Before the excavation can begin, there are steps that must be taken prior to the removal. These steps are primarily aimed at properly identifying the contents (if any) of the UST, and making sure the site is as safe as possible for the entire process.

Emptying the Tank

It is first necessary to make sure the tank is empty, and remove any liquid or residue that remains inside. Often times the contents of these tanks are flammable or hazardous, and must be handled accordingly. The transportation and disposal of such materials may require additional permits, along with regulation by appropriate government agencies.

Avoiding Combustion

If the tank has been recently emptied of combustible material, it is important to replace the flammable gasses inside with a non-combustible gas. This can be accomplished by placing dry ice (carbon dioxide) inside the tank, which will displace the oxygen and other vapors that may have been present, which will make the removal process much safer by greatly reducing the risk of explosion. It is mandatory to keep the site free of any flames or sparks unless the tank has been Certified Clean.

Certified Clean Tanks

Only certain Certified Professionals can declare a UST clean, meaning there are no sludges, debris, or vapors inside the tank. With a “Clean Certificate” there are more options available on-site, such as cutting methods that use heat or flames, and tools that produce sparks. Such methods comprise what is known as “Hot Work.”

UST Permit for Hot Work by OSHA.gov

UST Permit for Hot Work by OSHA.gov

Excavating the Site

Typically, a Soils Management Plan is the leading guideline for the excavation process of removing a UST. The process of physically removing the UST will commence with digging, using standard construction equipment such as backhoes and excavators. This same equipment applies to hoist the underground storage tank out of the hole, by securing it with chains and lifting. For very large tanks, contractors will require using a crane to raise the UST out of the pit. All of the soil burdens from the ground must remain on-site until the soil sampling and laboratory analysis is complete.

Confirmation Soil Sampling

Under the direction of a professional geologist or engineer, the soil around the UST must be tested for contamination. If the soil is found to be free of petroleum products and other hazardous materials, then the soil that was removed may be used to backfill the excavation pit. Otherwise, the contaminated soil must be removed under hazardous material guidelines, new clean soil must be used to fill the pit, and further testing will be necessary to determine the best course of action for remediation.

Disposal of the UST Materials

After the tank is removed from the ground, it will need to be cleaned thoroughly before it can be recycled. The tank may be transported off-site to be cleaned and dismantled.  Or, if the tank has already been Certified Clean on-site, then it is ready to be transported directly to a facility that receives metal for recycling.

Underground Storage Tank Abandonment Report Writing

The professional geologist or engineer leading the project will be responsible for submitting an “Underground Storage Tank Abandonment Report.” This final report will summarize the on-site activities as well as the results of the soil analysis. If further action is necessary, then recommendations for the next steps will also be in the report. A professional geologist or engineer must sign and stamp this document prior to submitting it to the regulatory agency. For example, the Los Angeles Fire Department requires a professional geologist to stamp UST closure report. And these reports are frequently under additional review by other geologists at the Regional Water Quality Control Board. Copies of this report also remain with the property owner, as well as the other regulatory agencies with involvement.


Completion of the underground Storage tank abandonment process occurs after successfully performing all of the above requirements. At this stage, the engineering consultant files all the relatable documents together. This includes the original permit application. Unless there is an ongoing remediation project at the site, this is where the UST removal process ends.


Written By: Michael Joseph Sabo

Edited By: Adam Azad Kaligi, PG