Underground Utility and Pipe Locating Using GPR

Locating underground storage tanks using GPRUtility locating service performed by Penhall Technologies can identify subsurface hazards or obstructions exist in the ground within private property. They can range from: gas lines, sewer and drainage lines, sewer and drainage lines, etc. Additionally, our trained analysts can estimate the depth of both metallic and nonmetallic objects. Penhall Technologies’ trained analysts perform the service in most effective manner. We also provide concrete scanning and x-ray imaging.

Common Subsurface Utilities

Buried underground utilities

According to the Common Ground Alliance, there are more than 20 million miles of buried utilities in the United States. The most common underground utilities are:Electrical, water, gas, communication, sewer and storm drain lines/utilities.


Utility Locating Methods and Equipment

Underground utility locating requires sophisticated equipment and technologies to complete a project properly. Each project is very different and unique. As a result, there are many variables to take into consideration such as:

  • Which utilities need to be identified
  • Moisture content of the soil
  • Terrain
  • Natural and man-made obstacles

At Penhall Technologies, our analysts utilize industry-leading equipment to perform the service with highest level of accuracy.

1. RD 7000 Series Pipe and Utility Locator

utility locating equipment

The RD 7000+ Pipe and Utility Locator is the backbone of modern utility locating.  With multiple frequencies, power modes, and both passive and active systems, the RD is almost always the proper way to start any utility locate. The RD system works by applying a current via the transmitter to the metal pipe, valve, or tracer wire and using the receiver to trace the electromagnetic field down the length of the pipe or wire.

The receiver can accurately locate both the position of the utility and the depth below surface.  For non-metallic utilities with access ports, a metal fish tape or rod with the sonde accessory can be used to help trace the utility.

2. GSSI Utility Locating Cart with 400MHz antenna

The GSSI manufactured utility cart with 400MHz antenna can locate both metallic and non-metallic utilities to a maximum depth of approximately 9ft under ideal soil conditions.

Utility Locating Device with GPR technoloy

GPR penetration and resolution is entirely dependent on soil conditions.  GPR prefers dense, resistive mediums and will be limited in wet or conductive soils.  Despite those limitations, GPR is often the only way to detect abandoned lines, utilities with no surface valves, PVC, transite (asbestos-cement), or similar non-metallic utilities.



The Science of Electromagnetic Induction

electromagnetic induction to locate utilitiesProducing a force or voltage by moving a conductor across a magnetic field is known as electromagnetic induction. It can be found in many technological applications such as generators, transformers, and utility locating equipment.

Utility locating devices  transmit a radio wave at a certain frequency and this radio wave is electromagnetic by nature. The magnetic field inherent in the radio wave moves across an object and generates a voltage that runs along it’s length. This current, which has been induced, generates its own electromagnetic field. Most of the voltage travels down the outside of the object, such as a pipe or wire, rather than penetrating the inside.Placing a receiver on the ground directly above the buried utilities will detect the electromagnetic field allowing an analyst to locate a metal pipe or cable that is buried in the ground. The distance a signal can travel down a pipe or wire is determined by the resistivity of the surrounding soil and pipe itself, as well as the frequency, transmission power, distance from the transmitter, and capacitance of the pipe or cable.

Utility Marking Standards

Color codes are used to mark existing underground utilities to protect them from damage during excavation. Markings can be made by spray painting lines, using flags, or both to highlight the location. Penhall Technologies adheres to the standard underground utility locating color chart used all over North America.  This color protocol conforms with both the Concrete Sawing & Drilling Association (CSDA) and the American Public Works Association (APWA) marking depiction of underground utilities. Below is the color scheme:

Redelectrical lines, conduit, and cables
Orangetelecommunication lines
Yellowgas, oil, steam, and petroleum
Greensewers and storm drain
Bluedrinking water
Purplereclaimed water and irrigation
Pinktemporary or unknown survey markings
Whiteproposed survey or excavation area


How does Ground Penetrating Radar help with Utility Locating?

Unlike traditional utility locating systems, GPR can detect plastic, concrete, and metal pipes. In regards, GPR is an ideal technology to locate in ground utilities of all kinds.GPR technology works by sending a flash of energy into a surface material like concrete or ground soil via special antenna. Each GPR unit embedded with computer system can register the time and strength required for the return of any reflected signals. Dynamic subsurface differences will create reflections that are logged by the system and archived. These reflections are produced by several variables such as conduit or pipes. As a result, GPR only requires access to one side which is an added benefit when needing to search for utilities.

What are the consequences of hitting an underground utility?

Striking an underground utility can be absolutely disastrous both in terms of monetary cost and loss of life. The cost of hitting an underground utility can range in the thousands of dollars and more importantly can cause injury or even death.  The best way to reduce the chances of a safety accident on your next project is to contact Penhall Technologies to locate all underground utilities prior to trenching.

Natural Gas Pipeline Explosing

When should I use a private utility locator?

You are probably OK digging a few inches in your home garden. However, the more you dig or cut, the more risk it is for you to accidentally hit a utility. Underground hazards can be anywhere that only GPR analysts can detect. At Penhall, safety is our No.1 priority in excavating. Without the right skill sets and equipment, scanning for utilities can be a potentially disastrous gamble.

  • 811 will not locate utilities on privately owned property
  • Property owners are responsible for damaged utilities on private property.

Experienced utility locator identifying sewer lines

We Locate and Identify

  • Sewer Pipes
  • Gas & Propane Lines
  • Sprinkler Lines & Pipes
  • Storm & Drainage Pipes
  • Electric Cables & Conduit
  • Telecommunication Lines