Finding Buried Tanks & Pipes with Ground Penetrating Radar (GPR)
The number one method for finding buried objects such as petroleum tanks, water lines, sewer lines and other buried objects is by performing a Ground Penetrating Radar (GPR) survey. GPR surveys are non destructive evaluation (tank sweep) of buried objects.
The white rectangle in the photo represents a buried underground storage tank (UST). No indications of the tank was present prior to the GPR survey. A real estate transaction found that the property once had oil as a heating source. The current owner had no knowledge of an oil tank and hired Curren to completed a tank GPR scan of the site to determine if a tank was present.
GPR Uses & Applications
- Locate buried tanks
- Identify former tank excavations.
- Finding water and sewer lines.
- Locate metallic and nonmetallic pipes and utility cable
- Delineate pits and trenches containing metallic and nonmetallic debris
- Delineate previously excavated and backfilled areas
- Find subsurface obstacles such as rocks and old foundations
GPR Operation & Application
What is GPR (ground Penetrating Radar)?
A GPR radiates short pulses of high-frequency EM energy into the ground from a transmitting antenna. When this EM energy (wave) encounters the interface of two materials having different dielectric properties (i.e., tank buried in the ground), a portion of the energy is reflected back to the surface, where it is detected by a receiver antenna and transmitted to a control unit for processing and display. In short buried solid objects such as tanks or pipes reflect the EM signal back to the surface, where it is read and logged. If the signal does not encounter a buried object the EM signals goes deeper into the ground. The difference between these two readings is what allows a GPR technician to determine a buried object from normal soils.
Q. How do you GPR for a buried tank or utility?
A. The GPR system is mounted on a wheeled carrier (about the size of a lawn mower) vehicle which is manually pushed by the GPR operator. The GPR system transmits radar waves into the ground and reflected back to the surface by the radar unit. As the radar unit is moved along the ground scans are collected and interpreted by the operator. So real time locating of buried oil tanks can be made.
Q Is GPR the same as an Xray?
A. No x rays and GPR are two different methods of scanning. GPR is the more popular for finding buried objects.
Q. How deep can GPR penetrate or see below the ground?
A. Effective depth of penetration ranges from about one foot in moist clay to 50 feet or more, in dry granular rocks and sediments. Also higher frequency signals are attenuated faster then lower frequencies.
Q. Can you use GPR to find buried tanks and buried utilities in concrete?
A. Depending on what you are looking for i.e, a buried tank or a utility that is encased in a concrete floor, there are specific radar antennas that can be used. An example is this is that when you are performing concrete inspections, a different GPR antenna would be utilized than if you were looking for a buried tank.
Q. Can radar go through concrete and asphalt?
A. Ground penetrating radar can go through asphalt and concrete to locate buried utilities and tanks.
Q. How do you identify buried objects such as tank and pipes with radar?
A. When the GPR unit has gone over an area that contains subsurface information, the GPR technician records the information, including location and buried depth. Our Geophysical technician then accurately marks the ground at the position of the object with spray paint. Once the area has been marked the GPR survey can continue.
Q. If I find a buried oil tank or former tank grave (excavation) can Curren remove and test the area?
A Yes Curren is a licensed tank removal and testing company. Curren can remove and test the tank location or do soil borings to test the soil where a tank was previously buried.
Q. Should I be concerned if a buried oil tank was on my property, but was removed?
A. Yes and No. Yes you should be concerned because the tank may have leaked and that question needs to be definitively answered. By definitive we mean that you have a muti page report documenting the tank was removed and testing was performed with a written statement from the tank removal/testing company stating that the tank did not leak. If you do not have this information, then yes you need to be concerned.
Now the No answer. If you have a report documenting the tank removal with soil tests stating the tank did not leak, then no you do not need to be worried.
Q. I am buying or selling a house and the only information I have concerning the tank removal is a permit from the township stating the tank was removed and approved. Is that permit enough?
A. No it is not enough because it is not from an environmental company documenting that the tank did not leak.