A property is being prepared for construction, but an old site plan shows an underground storage tank that no one can account for. There is no clear record of its removal, and nothing visible at the surface confirms whether it is still there.
Can GPR locate underground storage tanks? Yes. Ground Penetrating Radar can help detect suspected steel and fiberglass tanks when site conditions allow. It can also provide information about their approximate location, depth, and boundaries. In some cases, GPR may even reveal evidence of a tank that was removed years ago.
For contractors, environmental consultants, and property owners, those findings can help narrow down where further investigation is needed before excavation begins.
There are limits to what radar can tell us, though. A GPR survey cannot confirm that a buried object is a storage tank, identify what’s inside it, or determine whether the surrounding soil is contaminated.
Why Underground Storage Tanks Need to Be Located Before Excavation
Underground storage tanks (USTs) have been used at gas stations, industrial facilities, maintenance yards, and other properties where fuel or chemicals needed to be stored.
Some are still in service. Others were removed years ago, while certain tanks were closed and left underground under applicable requirements.
The problem arises when the property’s history is incomplete.
An old gas station may have been torn down years ago, with a new building and parking lot now covering the property. After several owners and construction projects, it can be difficult to piece together what was buried, what was removed, and what might still be underground.
For someone preparing to excavate, those missing details matter.
A buried tank can interfere with planned construction and may present additional safety concerns if it contains fuel, vapors, or other hazardous materials. Older tanks can also raise environmental concerns because corrosion or other failures may have allowed stored substances to escape.
The U.S. Environmental Protection Agency (EPA) considers a tank and its connected underground piping a UST system when at least 10% of their combined volume is below ground. Federal regulations cover many of these systems when they store petroleum or certain hazardous substances, although some are excluded.
Locating a suspected tank can also be important during property transactions. If a property has a history of fuel storage but no documentation showing what happened to the tanks, a buyer or environmental consultant may need more information before deciding what to do with the site.
How Do Phase I and Phase II Environmental Site Assessments Help Identify Underground Storage Tanks?
An underground storage tank may first come to light during a Phase I Environmental Site Assessment (ESA). As part of that process, environmental professionals review historical property records, past land uses, and other available information to identify potential environmental concerns.
For example, old records may show that a gas station or industrial facility once operated on the property. They might also indicate that an underground storage tank was installed, even though there is no documentation showing whether it was removed.
When further investigation is warranted, a Phase II ESA may include a GPR survey to look for the suspected tank or evidence of a former tank excavation. The survey can help environmental professionals determine where additional investigation may be needed.
GPR can provide useful information during this process, but it cannot confirm that a tank was properly removed or that the surrounding soil is free of contamination. Those questions may require additional records, physical investigation, or environmental testing.
How Does GPR Locate Underground Storage Tanks?
Ground Penetrating Radar sends electromagnetic pulses into the ground. When those pulses encounter materials with different electrical properties, some of the energy reflects toward the surface.
The equipment records those reflections as the technician moves across the survey area.
A buried storage tank may produce a recognizable response because its material, shape, and surrounding conditions differ from the surrounding soil. By collecting data along multiple survey lines, the technician can evaluate the location and apparent extent of a suspected buried object.
The EPA identifies GPR as a geophysical method for locating underground tanks, utilities, and other buried features.
At Echo GPR, we use ground-penetrating radar technology to investigate suspected underground storage tank locations. Our underground storage tank locating services can help identify possible buried tanks, estimate their location and depth, and investigate areas where tanks may have been removed.
Can GPR Detect Steel and Fiberglass Tanks?
Yes. Both steel and fiberglass underground storage tanks can produce detectable radar responses.
Steel generally creates a strong reflection because metal has electrical properties that differ from the surrounding ground. That can make steel tanks easier to recognize when the radar signal reaches them.
GPR can pick up fiberglass tanks, too. They don’t usually produce the same strong radar reflections as steel tanks, so they can be harder to find, particularly when buried deep or in wet, clay-heavy soil.
The EPA’s Expedited Site Assessment Tools for Underground Storage Tank Sites identify steel, fiberglass, composite, and steel-reinforced concrete tanks as potential GPR targets.
A strong radar reflection does not automatically confirm that a tank has been found. Buried metal debris, concrete structures, and other underground objects can produce responses that require further interpretation.
What Can GPR Tell You About a Suspected Underground Storage Tank?
When ground conditions are favorable, a GPR survey may provide several pieces of information that help the project team plan its next steps.
- Approximate location: A survey may identify where a suspected tank or other buried structure is located within the investigation area.
- Estimated depth: Radar data can sometimes be used to estimate the depth to a detected feature. Accuracy depends partly on how well the radar signal’s travel speed through the ground is understood.
- Possible size and orientation: Multiple survey passes may help establish the apparent extent and direction of a buried object, although radar does not necessarily reveal its exact dimensions.
- Nearby subsurface features: GPR may identify piping, buried structures, disturbed soil, or other anomalies associated with the suspected tank area.
This information can narrow the area requiring further investigation.
For example, an environmental consultant may have a historical drawing showing a tank somewhere near a former building. A GPR survey could identify an anomaly consistent with buried storage infrastructure and provide a more focused location for additional evaluation.
There is an important distinction between identifying a possible tank and confirming one.
GPR records subsurface reflections. A technician interprets those reflections using their characteristics, surrounding evidence, and available site information. The results may support the presence of a suspected tank, but physical confirmation can still be necessary.
Can GPR Confirm That a Tank Is Present?
Not on its own.
A radar response may be consistent with a buried storage tank, especially when its apparent shape and location agree with historical information. However, other underground features can produce similar responses.
A technician may recommend additional investigation when the data does not identify an object.
The absence of a recognizable tank response also does not guarantee that no tank exists. A tank may be too deep to detect under the prevailing conditions, or other subsurface materials may interfere with the radar signal.
Can GPR Find Where an Underground Storage Tank Was Removed?
A tank doesn’t have to remain underground for a previous excavation to leave evidence.
When an underground storage tank is removed, the surrounding soil is excavated, and the resulting pit is typically backfilled. That backfilled area may have different characteristics from the undisturbed ground around it.
GPR can sometimes detect those differences.
At Echo GPR, we can investigate suspected former tank locations and evaluate radar responses that may indicate the boundaries of a previously excavated pit. GPR may help identify the old tank excavation, even when the property records don’t show where the tank was once located.
It can also help environmental consultants understand the location of a former tank excavation before planning additional investigation.
What Does a Former Tank Pit Look Like in GPR Data?
A former excavation may appear as an area where subsurface reflections or soil-layer patterns change.
After a tank is taken out, the hole is filled with soil or other material. Depending on what was used to fill it, GPR may pick up differences between that area and the surrounding ground.
The USDA Natural Resources Conservation Service identifies disturbed soils and fill among the subsurface features GPR can investigate.
Whether a former tank pit can be identified depends on the contrast between the backfill and surrounding ground, the depth of the excavation, and conditions at the site.
An apparent excavation boundary cannot establish that a tank was once present or that it was properly removed. Historical records and other investigation methods may be needed to determine what occurred.
What Can Affect GPR Results When Locating Underground Tanks?
GPR performance varies from one property to another.
The radar signal must travel through the ground before it can reflect from a buried feature. Certain soil conditions can weaken that signal and make deeper objects difficult to detect.
Clay-rich soils, highly conductive ground, saline conditions, and moisture can all affect radar penetration.
The USDA explains that soils with high electrical conductivity reduce radar effectiveness. Sandy, well-drained soils generally provide more favorable conditions for deeper radar penetration than poorly drained, clay-rich soils.
Burial depth also matters. A tank located relatively close to the surface may be easier to investigate than one buried deeper beneath conductive soil.
Other site conditions can affect the survey, including reinforced pavement, buried debris, nearby utilities, uneven terrain, and limited access.
The technician must consider those conditions when evaluating the data.
Sometimes another geophysical method may provide useful supporting information. Metal detection, magnetometry, or electromagnetic locating may help investigate metallic objects or other subsurface features, depending on the site.
The EPA discusses these methods in its guidance for underground storage tank site assessments.
A combination of methods may be appropriate when the suspected tank location is uncertain, or the available GPR data is inconclusive.
What Happens After a Suspected Underground Storage Tank Is Located?
Finding an area consistent with a buried tank gives the project team a place to investigate further.
The next step depends on the property’s history, the planned work, and what the survey identified.
Finding a possible tank can put excavation plans on hold while the site is investigated further. If the concern was identified during a Phase I ESA, the environmental consultant may recommend additional work as part of a Phase II ESA. That could include investigating the suspected tank location, reviewing available removal records, or collecting soil and groundwater samples when appropriate.
Underground utilities may also be near the suspected tank.
Former fueling facilities can contain buried product lines, electrical conduits, and other infrastructure associated with the original operation. Those features may still be present even when the buildings or tanks have been removed.
Before drilling or excavation, our private utility locating services can help investigate buried infrastructure that may not be included in public utility markings.
We also evaluate proposed boring locations as part of environmental investigations when subsurface utilities or obstructions could interfere with drilling.
Can GPR Determine Whether a Tank Has Leaked?
A standard GPR tank-locating survey cannot establish whether a tank has leaked or whether the surrounding soil is contaminated.
Radar responds to differences in subsurface electrical properties. Some contamination-related changes may influence radar data under particular conditions, but those responses are not specific enough to confirm a petroleum release.
GPR also cannot identify the contents of a buried tank or measure contaminant concentrations.
To check for contamination, environmental teams may collect soil or groundwater samples from the property and send them to a laboratory for testing.
A GPR survey can help identify locations that deserve attention during that investigation. It does not replace environmental testing.
The Echo GPR Perspective
On an older property, the available records don’t always match what is found in the field.
A drawing may show a tank that was removed years ago. Another property may have no tank records at all, even though its history suggests fuel storage once took place.
We use that background information to help guide the investigation, then evaluate what the radar data shows.
The radar data may show signs of a buried tank, an old excavation, or something else underground. At some properties, the soil makes it difficult to tell what caused the radar response.
Our responsibility is to communicate what we found, what the data suggests, and where uncertainty remains. That gives the environmental or construction team information they can use to decide what happens next.
The Bottom Line
Can GPR locate underground storage tanks? Yes. Ground Penetrating Radar can help identify suspected steel and fiberglass tanks, estimate their location and depth, and investigate areas where tanks may have been removed.
It can also provide useful information about nearby subsurface features before excavation or environmental drilling begins.
Results depend on ground conditions and the characteristics of the buried feature. Additional investigation may be necessary to confirm a tank’s identity, determine its condition, or evaluate possible contamination.
Based in Olathe, Kansas, we provide underground storage tank locating and other GPR services for residential, commercial, industrial, and government properties throughout the Kansas City area and surrounding Midwest.
If you’re investigating a suspected underground storage tank or planning excavation on a property with a history of fuel storage, request a quote from Echo GPR or call (913) 879-2200 to discuss your project.
Frequently Asked Questions
How Deep Can GPR Detect an Underground Storage Tank?
That depends on ground conditions and how deep the tank is buried. In sandy soils, radar signals may travel deeper than they would in wet, clay-heavy ground. A tank buried several feet down may be detectable at one property and difficult to locate at another.
Can GPR Find an Abandoned Underground Storage Tank?
Yes, an abandoned tank may still produce a detectable radar response if it remains underground and conditions are favorable. GPR cannot determine whether the tank was properly closed or whether it contains hazardous materials.
Can GPR Locate a Fiberglass Underground Storage Tank?
Yes, GPR can locate fiberglass tanks. They can be harder to detect than steel tanks, especially when they’re buried deeper or the soil interferes with the signal. A technician will look at the radar patterns and surrounding conditions to determine whether a buried feature could be a tank.
Can GPR Locate a Tank That Has Already Been Removed?
GPR cannot locate a tank that is no longer there, but it may identify disturbed soil or backfill associated with the former tank excavation. These findings can help estimate where the tank pit was located.
Can GPR Confirm That No Underground Storage Tanks Are Present?
No. A survey that does not identify a tank cannot guarantee that none exists. Poor ground conditions, excessive burial depth, or other subsurface features may limit detection.
Can GPR Tell Whether an Underground Storage Tank Is Empty?
No. GPR should not be relied on to determine whether a buried tank is empty or identify what it contains. Those questions require appropriate inspection or investigation methods.
Why Locate Underground Storage Tanks Before Buying Property?
A property with a history of fuel or chemical storage may have undocumented underground infrastructure. A geophysical investigation can help identify suspected tanks or former excavation areas, giving the buyer and environmental consultant additional information to consider during due diligence.