Tanks are a Normal Part of Construction – The Basics Part 1 of 2

Anna Saindon, P.E., R.G., Ph.D., AEG Member, St. Louis Chapter

Environmental Senior Project Manager – Geotechnology, Inc.

Unknown tanks are often discovered during construction activities, demolition activities, subsurface explorations, environmental due diligence, and geohazard mitigation projects.  This occurs significantly more often in urban areas, but the unknown tanks you find in small towns are where you’ll find some creativity in how things were put together.  This two-part blog post covers the basics to help minimize impacts to the environment and your project.

I’m using the common term “tanks” instead of the official term Underground Storage Tanks (USTs).  The term UST is used by regulatory agencies and environmental professionals.  Aboveground Storage Tanks (ASTs) are not included in this discussion since the regulations and methods for removals and closures are different.  This is a general and not a state specific discussion on tank removals because there are too many states to fit into a blog post. 

Photo 1 shows a regular day at the office for someone in the environmental industry even if we don’t specialize in tanks.  We get a call from a general contractor saying the soil smells like diesel and they need help.  Once we arrive, we confirm the issue with observations and field equipment, collect soil and groundwater samples where appropriate, and poke around a bit if we think a tank is a likely source.  In the instance shown in Photo 1, they were constructing stormwater structures between a new building under construction and an historic building being preserved.  All construction in this area had to be put on hold until the tank and the impacted soils were addressed. 

Fortunately, in the case described, we were able to identify the tank as an out-of-use heating oil tank for the historic building.  Heating oil tanks are not regulated in Federal regulations nor the State this tank was discovered in.  Even though a tank may not be regulated, you are still obligated to substantially follow the closure and cleanup activities required for a regulated tank.  Notifications to the State or Federal agencies, fire marshall, or sending a report for regulatory approval is not required for unregulated tanks and cuts substantial time off the tank cleaning and removal process.  For the client/owner documentation and reduction of business risk for the future, a report documenting what was done, the sampling and testing results, and disposal of the tank and impacted material should still be provided.

The Federal unregulated tank list includes tanks that are a low risk of impacts to the environment or safety compared to the effort it would take to regulate them.  Many of the tanks types in this list were in place long before environmental regulations occurred in the USA and can’t be tracked, even if we wanted to, due to the quantity and unknown locations.  The following is the list of Federally unregulated tanks, though some States will regulate additional tank types so check with an environmental professional or State agency prior to making the regulatory determination.

  • Farm and residential tanks of 1,100 gallons or less capacity holding motor fuel used for noncommercial purposes;
  • Tanks storing heating oil used on the premises where it is stored;
  • Tanks on or above the floor of underground areas, such as basements or tunnels;
  • Septic tanks and systems for collecting storm water and wastewater;
  • Flow-through process tanks;
  • Tanks of 110 gallons or less capacity; and
  • Emergency spill and overfill tanks.

Tank Removal Basics – For a Typical Regulated Tank

Tanks are typically removed and recycled at the end of their useful life.  The public can access state UST registries to verify if the onsite tank they have is registered, needs to be registered, or may be eligible for petroleum storage tank insurance funds.   Petroleum storage tank insurance funds vary widely in what they cover and what information they need, so just like State specific regulations, insurance fund requirements will not be discussed here.

The first step is notifying the state regulatory agency and state fire marshal that there is a tank that will be removed.  Some states require the state fire marshal to be on site during the removal activities.  Some counties also require additional notifications or permits that can take up to 30 days to obtain.

Next, the remaining liquid contents are removed from the tank and disposed of by a licensed company for either recycling or disposal as special or hazardous waste prior to additional work to reduce the potential for spills during the removal process. (Photo 2).  The overburden is then removed to expose the tank and placed in a separate pile for analytical testing and potential reuse as backfill.  The tank air is made explosion safe before the confined space procedures start.  The tank is removed, placed on plastic, cut open, and cleaned prior to recycling or disposal.

Soil sampling and analytical testing occur on the floor and walls of the tank pit, typically biased toward areas that have obvious contamination based on staining, odors and elevated field screening readings. Often, a small amount of impacted soils can be removed with the tank without triggering a full remedial action as long as it is tested, manifested, and disposed of properly.  Groundwater sampling and analytical testing occurs if groundwater enters the tank excavation. Impacted soils are tested, disposal permits obtained, and the soils are commonly disposed of at a permitted non-hazardous landfill.  The tank cleaning material is also tested and disposed of appropriately.  Clean backfill is compacted into the tank pit based on the client’s requirements for future use.  

A tank closure report is submitted to the regulatory agencies and either a No Further Action (NFA) letter is obtained or further remedial action occurs.

This tank removal process is both time and financially effective as long as there is enough excavation space, no utility issues, and the activities are not disrupting site operations.  Complications and solutions for tank removals will be covered in the next post.

For more general information on tanks:

Basic USEPA UST Program Fact Sheet – https://www.epa.gov/sites/production/files/2020-11/documents/ust-program-facts.pdf

Basic USEPA UST information page - https://www.epa.gov/ust/learn-about-underground-storage-tanks-usts


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