Whether you’re a homeowner planting a tree, or a professional excavator laying fiber optic cable, you’re required by law to contact 811 before you break ground.

811 is the national call-before-you dig phone number. Anyone who plans to dig should call 811 or visit their state 811 center’s website a few business days before digging to request that the approximate location of buried, public utilities be marked with paint or flags. This is done to ensure you don’t unintentionally dig into an underground utility line.

811 is a vital step in keeping you and your community safe from the dangers of a utility strike, but it only locates public utilities. You should also employ a private utility locating service such as GPRS to ensure that there are no private utility lines where you’re intending to dig. 

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What is Utility Locating?

Utility locating is the detection of underground utilities and other subsurface findings using ground penetrating radar (GPR) and other tools. Utilities and other findings can be located and marked out in a safe, non-destructive manner.

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What Types of Utilities Can be Located?

Electric, steam, telecommunications, water pipes, gas & oil pipes, sewer pipes & storm sewer lines, and many other primary and secondary utility services can be located.

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How Long are Utility Locates Valid?

Utility locates are valid if the markings are visible, and no utilities have been added or removed. A more permanent record can also be produced to preserve the information gathered during a utility locate, however, this too needs updated if utilities are added or removed.

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How do Utility Locates Work?

You first need to contact your utility locating service of choice to schedule a site visit. 

A trained utility locator will then visit your site to determine if a full locate is possible based on site conditions. Ground penetrating radar (GPR) is the most efficient and accurate tool for modern utility locating, but it does have limitations – it cannot penetrate as deeply into clay soils, for example. So, the site visit is a vital step in ensuring the proper technology is used to locate utilities where you are planning to dig.

Once the site visit is complete, the utility locating technician will scan your site using GPR and other complimentary technologies, such as electromagnetic (EM) locating. This information is then marked or mapped out using paint and/or flags so that you have a clear picture of areas to avoid when excavating or performing other invasive groundwork.

How Does Utility Locating Equipment Work? 

As mentioned above, GPR has become the primary tool for utility locating. 

GPR is a non-destructive detection and imaging method which identifies subsurface elements either underground or within a surface such as concrete. It can detect both metallic and non-metallic objects, giving it a wide range of applications. It reveals all types of utilities, including electrical conduit, steam pipes, telecommunications lines, gas & oil lines, water lines, and sewer & storm pipes. 

GPR works by sending a radio signal into a structure and reading the “bounce” of those radio waves off any material they encounter. This creates a reading that displays those bounces as hyperbolas. An experienced GPR technician interprets this reading to determine the type of material located.

EM locating is a complimentary technology to GPR. An electromagnetic signal is either sent through an underground utility line by a transmitter, or the receiver searches for an existing electromagnetic signal in an active line.

The data from these various technologies is compiled by an experienced technician to create an accurate map of the underground infrastructure on your property. 

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What Colors Are Used to Mark Out Utility Locations?

Universal colors commonly used for utility location include:

• Red – Electrical, Conduit, Lighting
• Orange – Telecommunications, TV, Alarm or Signal
• Yellow – Gas, Oil, Steam, Petroleum
• Green – Sewer, Storm Drain
• Blue – Potable Water
• Purple – Reclaimed Water, Irrigation
• Pink – Temporary Marking
• White – Proposed Excavation

 Please note: While the above are the national standards for utility locate markings, there are occasionally regional differences. GPRS Project Managers follow regional marking guidelines when conducting a utility locate. 

Is it Difficult to Locate Underground Utilities?

Utility locating equipment such as GPR scanners are in a constant cycle of improvement and affordability, making them more user friendly. However, the effectiveness of this equipment still relies heavily on the knowledge and experience of its operator.

The best utility locating technicians complete an intensive, months-long training regimen before they ever attempt a utility locate on their own. They receive 320 hours of mentored field training. They log 80 hours of classroom training, where they tackle real-world scanning scenarios in a safe and structure environment. All this training ensures that these professionals can properly interpret the readings provided by utility locating equipment.

On average, a single utility strike costs $56,000 to repair, so you want to be sure you’re not going to strike one before you break ground. For that, you need the talents of a qualified professional.

How Much Does Utility Locating Cost?

The cost of a private utility locate varies depending on the size and specifics of the site being scanned, as well as other factors. Utility locates are not cheap, but as mentioned above they are a vital service and significantly less expensive than the cost – both financial and otherwise – of striking a utility line. 

How Does Surface Area Impact Utility Locating?

While surface area can impact the amount of time it takes to perform a scan, the number of subsurface findings plays a larger factor. 

A smaller urban area may take longer to scan than an empty plot of land due to the complexity of the underground utilities present.

Does the Type of Utility Being Located Have Any Impact on the Locating Process?

Certain materials are easier to locate due to the signal they produce when interacting with GPR equipment. For example, electrical wiring may be easier to detect than non-conductive PVC piping. Certain utilities are also buried deeper than others, and may require the use of additional scanning equipment – such as EM locating – to aid in detection.

Does Weather Impact Utility Locating?

Yes, weather conditions do play a role in the accuracy of GPR and other utility locating equipment. Wet conditions make it harder for the equipment to pick up a signal. Performing a utility locate in rainy or snowy conditions may not be possible. An experienced technician will be able to determine if conditions are right for performing a utility locate.

Why Should I Hire GPRS to Perform Private Utility Locates for Me or My Business? 

With over 400 elite Project Managers strategically stationed across the country, GPRS ensures you always have a qualified utility locating service near you. 

Our Project Managers are required to complete the industry-leading Subsurface Investigation Methodology (SIM) program. This method of locating includes specifications for underground utility locating and concrete scanning.

SIM focuses on a three-step approach to achieve the most accurate results when performing non-destructive subsurface testing:

• The need for experienced technicians
• The understanding and proper utilization of applicable technology
• The adherence to proven methodologies

SIM establishes the industry standard that private utility locating currently lacks. The use of SIM ensures site safety, and limits damage to subsurface and structural elements.

SIM-certified GPRS Project Managers receive a minimum of four weeks of field mentoring and then 80 hours of classroom training followed by an additional four weeks of field mentoring prior to being released into the field under the supervision of a senior Project Manager. This is well above the industry standard and a big part of why GPRS maintains a 99.8% accuracy rate for concrete scanning and utility locating. 

GPRS strives for 100% subsurface damage prevention. We tailor our suite of infrastructure visualization services to our clients’ needs, helping them Intelligently Visualize The Built World™ while keeping their projects on time, on budget, and safe. GPRS provides complimentary .KMZ and PDF files for every outdoor utility locate we do, so you see what we see, and where you can dig safely. 

What can we help you visualize? Click here to schedule a service today!

Note: GPRS does not provide geophysical, geological, land surveying or engineering services. If you need such services, please contact an appropriate professional.