Utility Locating Services Explained

Utility locating comes in two primary forms, public and private utility locating services.

Utility locating services

States provide a public utility locating service free to anyone excavating to prevent public utility strikes. The contractor involved is required to call 811 to avoid this subsurface damage. 811 services are often referred to by different names depending on the state, such as Dig Alert, Digline, Onecall, etc. 811 services are limited to public utilities exclusively as they do not account for private utilities. 

Public utilities account for water, electrical, gas, communications, and sewer lines. However, once a line connects into the infrastructure of a private facility, it is no longer considered a public utility. 811 services are often highly requested services as they are required for every project that breaks ground. However, 811 services only provide a base level of information and detail for each project. Private companies such as GPRS can provide a greater level of detail such as line depth, location of abandoned lines, and more. Private companies can provide high-quality digital maps and deliverables that 811 typically doesn’t offer.

GPRS providing many critical subsurface damage prevention services, such as utility locating, subsurface leak detection, CCTV video pipe inspection, and concrete imaging.

Clients should contact both public and private utility locators like GPRS for best practices. GPRS provides many critical subsurface damage prevention services, such as utility locating, subsurface leak detection, CCTV video pipe inspection, and concrete imaging.

GPRS refers to their utility locating technicians as Project Managers. GPRS makes this distinction due to the significant difference in the quality of service performed by their Project Managers in comparison to a standard technician. 

Before utility locating, Project Managers must consider multiple factors. A professional locator must consider the size of the area, whether there are existing maps for the site, if there are visible utilities to connect to directly, and more. Additionally, locators must consider the type of surface being scanned, as different materials will reflect GPR signals differently.

Traditional utility locating requires non-destructive testing equipment to identify subsurface utilities and obstructions. Here, we will briefly overview how our ground penetrating radar and EM locating equipment works.

Ground Penetrating Radar

There are two primary utility locating methods: ground penetrating radar and electromagnetic (EM) locating. 

It is crucial to find information about subsurface infrastructure without breaking ground because it provides critical subsurface infrastructure information in a non-invasive way. Utility location is typically conducted with GPR or ground penetrating radar equipment. Ground penetrating radar is a non-invasive method of subsurface locating that uses electromagnetic waves to identify what lies beneath the ground.

Although GPR equipment comes in many different forms, its function remains the same. An antenna emits electromagnetic waves of a specific frequency into the ground through a transmitter. At this point, those waves are reflected up to the antenna’s receiver at varying travel times and different signal intensities (or amplitudes). A visual display is then generated for the operator by encoding and sending this information to the control unit. This data is displayed in the form of an image. 

Ground Penetrating Radar

The electrical conductivity of the earth or concrete being scanned, the frequencies being transmitted, and the radiated power contribute to the effective range of ground penetrating radar. The more conductive the ground scanned is, the more challenging it is for electromagnetic waves to penetrate it. This is because the electromagnetic wave is attenuated. Due to these factors, there are often compromises on either depth or the image’s resolution generated by the electromagnetic waves. Higher frequencies provide a higher resolution but cannot penetrate the ground as far as lower frequencies and vice versa. For example, scanning ice may produce precise GPR results up to hundreds of feet deep; dry sand or concrete may have an image of up to 20 ft, but wet materials like clay soils may only allow inches of penetration. In most use cases, GPR is used to render images of the ground between five to ten feet deep.

The most challenging aspect of ground penetrating radar is that it requires highly qualified experts to use the equipment. This data is challenging to analyze because the collected information creates layers or hyperbola that requires expert-level understanding. Trained experts can distinguish the difference between clear versus obstructed areas. Additionally, GPR experts can identify the differences between subsurface obstructions like tree roots, rocks, USTs, pipes, conduits, and more. 

While GPR is an excellent tool to use in certain circumstances, when given the opportunity to connect to a line directly, electromagnetic locating can be a great option.


Electromagnetic Locating

Electromagnetic Locating

Electromagnetic locating, also referred to as EM locating, is another primary method of non-destructive utility locating. There are two methods of electromagnetic locating, active locating and passive locating.

Active locating is when a frequency is actively transmitted through the conductive material of the underground utility. Different utilities require the transmitter to be connected through various points. Water pipes are located by connecting the transmitter to them through a riser, hydrant, or valve. Signals are typically applied to a cable system such as electric or telephone by joining to the grounding structure of the utility. Power lines can be located by connecting to a meter box, transformer, or ground wire. Telephone and cable television systems can be found by applying a signal to the ground cables in a pedestal, manhole, or interface box.

A device referred to as a wand is then waved over the ground, detecting the electromagnetic fields. The field technician notes the location of the detected waves, mapping or indicating the path of the subsurface utilities.

Electromagnetic Locating

Due to the frequency being transmitted through the conductive material, the makeup of the ground does not affect locating as much as GPR. Electromagnetic locating can work in almost any condition, from concrete slabs to soil and clay, and even over water. EM locating is an excellent method of detecting utilities in less-than-ideal conditions, like inside buildings or congested environments.

Passive utility location involves detecting a field that is traveling along the utility from a source that is not applied by the locator, such as active power or radio waves. Often, these frequencies can be less reliable, so active locating is always preferred. It is often tricky for utility locators to distinguish between the different passive signals produced by various utilities. Any conductive utility has the potential to be carrying a passive signal including water, natural gas, steam, cable television, and copper telephone lines.


Utility Location Markings

Utility Location Markings & Deliverables

Utility locating deliverables are not universal between utility locating companies, and it’s important to know what products and services can be offered.

Physical Flags or Markings

Physical Flags or Markings

Clients often receive field markings in the form of paint, pin flags, stakes, or any other method they request. GPRS trains our Project Managers to ensure that all the field markings they apply are clear and easy to understand. Additionally, each GPRS Project Manager creates a GPS Mapping sketch and produces our automated mapping deliverables for outdoor utility locates.

KMZ and PDF Maps

KMZ and PDF Maps

It’s essential to know the difference between a pdf and a kmz map. Pdf files are images that visually communicate what utilities are located where. Think of a pdf file as a physical paper map that you can view on a computer device or a monitor. However, kmz files are tagged with geolocated points that indicate specific utilities, lines, and other features. GPRS offers a complimentary pdf and kmz map with every utility locating project.

CAD Renderings / 3D Models

CAD Renderings / 3D Models

CAD files can be 2D or 3D renderings of space. This service allows contractors, engineers, and owners to develop or update as-built drawings. Clients use these files for preplanning, to avoid utilities, or to document the history of their site on various CAD and GIS systems. The GPRS Deliverables Department can create CAD files documenting our outdoor utility locating results.

The Future of Utility Locating

While any look towards the future of an industry is primarily speculation, we must look ahead to what’s on the horizon.

We’ve seen an incredible technological jump in the last 20 years, and now we’re seeing a convergence of those technologies. Due to battery capacity and compactness innovation, drones have become a more viable solution for unmanned and affordable aircraft. GPRS can detect subsurface voids, leaks, and utilities from hundreds of feet in the air using thermographic and magnetic imagery. Additionally, image capturing drones can provide excellent building façade imagery and documentation that would previously have proved impossible to produce.

Legislation is also a significant factor to consider when speculating what the future of utility locating looks like. Because of the massive amounts of damages and the severe safety risk posed when striking utilities, it’s possible that hiring a private utility locator will be a legal mandate. SUE services may also become mandatory for specific excavation or construction processes to mitigate the damage.

While water and sewer lines are under the ground, it’s common for electrical and communication lines to be strung from towers and poles above. These lines may be undergrounded in the future to prevent damages and safety hazards. 

Utility Locating

Additionally, with the cloud becoming a more significant part of our everyday lives, we can predict that databases will one day be the primary storage of utility lines and location data. Currently, data is siloed and challenging to access between areas and companies. Eventually, a centralized service could store and collect utility location data. This data will most likely be acquired and managed by private utility locators through a shared database or individual methods.

These databases would be valuable storehouses of information that could benefit facility owners and managers in perpetuity.

While no one can perfectly predict what the future will hold for utilities and utility locating, it is a certainty that methods will evolve as we continue to advance technologically.

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