Buried Utilities GPR
Examples of GPR profiles demonstrating identification of pipes with various contents
GPR is routinely used to locate precisely a wide variety of buried utilities. The antenna of choice is at 400 MHz. In the examples shown, the utility, commonly a pipe, is located at the apex of the hyperbola in the radargram. The color banding of the hyperbola may provide information about the contents of the pipe.
Fig. 1. 400 MHz GPR profile showing three hyperbolas indicating three pipes located at the apices of the hyperbolas and oriented at an angle to the profile. The middle diffraction hyperbola has a strong, upper black band signaling that this diffraction has a negative phase polarity. This indicates that the pipe is air-filled (empty) PVC (known to be 8“ in diameter).*
Fig. 2. 400 MHz GPR profile across a road showing one bright hyperbola indicative of a pipe located at its apex. The diffraction hyperbola has a white upper band which means a positive phase polarity. This signals either that the pipe is full of water or is composed of metal. Both alternatives, at this location, imply the pipe is a water main.*
Fig. 3. 400 MHz GPR with several bright, stacked diffraction hyperbolas. Several pipes must be located at the apex of this hyperbola cluster. Note dipping left upper edge of a trench above and to left of the hyperbolas. Survey site is adjacent to an industrial building. The bank of conduits feeds into the building. *
Fig. 4. 3D GPR radargram of a 50 ft x 40 ft area showing several utility lines (bright white lines) on a horizontal slice at a depth of 4 ft. Data collected with a 400-MHz antenna. Utility lines probably dip at a slight angle and so would be apparent on other depth slices.*
* Geophysical Survey Systems, Inc., 2015a, Radan 7 Manual.