Common Misconceptions of Utility Locating

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Evan Mowbray

Common Misconceptions of Utility Locating Services

Determining the location of underground utilities and subsurface structures is a complex ordeal. There are a number of misconceptions on the service, some being somewhat grounded (undergrounded?) in truth, to conceptions being completely false. Today we’re discussing and debunking a few of the common myths of utility locating along with the facts that’ll help you for your projects going forward.

The largest and most common misconception is that an 811 or one-call service will mark out all utilities. This is not the case. The 811 system is mainly put in place to protect public utility lines. A large number of utilities buried underground are private utilities and won’t be marked by 811 contractors. Only a qualified private utility locating service, such as our team at Trinity Subsurface, will locate private utilities. The mindset that 811 will protect all lines can lead to an increased risk of accidents and/or injuries during excavation or construction activities. With that being said, utility locating isn’t just for construction sites. Work occurs in yards and streets  across towns and cities all the time, including utility repairs, gardening, fence installations and driveway repairs.

The next myth comes from the quality level of utility data and ground penetrating radar scanning technology. Ground penetrating radar and electromagnetic locating are useful in determining the horizontal locations of utilities and structures, allowing clients to determine where to avoid digging. It may even give you a rough idea of how deep a structure is, depending on the right conditions. However, ground penetrating radar isn’t a guarantee for the exact depth of a utility or subsurface structure, and Trinity will never guarantee an exact utility location with ground penetrating radar alone. GPR will only give you Quality Level B utility information. In order to find the exact utility location and gain that Quality Level A data, you’ll need to use vacuum excavation to safely find the exact depth and other characteristics.

Another misconception is that each type of utility requires the same techniques to locate through a relatively straightforward process. While tools like ground penetrating radar and electromagnetic locating are commonly used in locating, scanning over the surface isn’t the only step involved with the process. Oftentimes our locators will have to examine a site for surface features, open up access points or manholes, and apply a transmitter signal to specific lines to determine their location. For sewers, we may run a tracer via a duct rod into the existing pipes to better determine the signal and uncover the line.

Utilities aren’t always accurately mapped, either. A lot of older utility infrastructure systems may be lacking when it comes to records. Any adjustments to utility systems will likely not be adjusted on older plans. Relying on existing as-built plans may not be the best option. In one case, our team was faced with locating a water line leading outside of a building scheduled for demolition, drawn going straight into the line perpendicularly on the plans. In reality, the line was installed on an angle, going against what the drawings would tell anyone working at the site. 

There’s also the case of unlocatable utilities. Not every utility can be located with a scan. A number of factors play into this, including soil and site conditions (including lack of access to parts of a site to confirm utilities), construction materials, whether the utility has tracer wire or not, and the depth of a utility can all be reasons why a utility can’t be located using GPR. Our team at Trinity always aims to determine the most accurate location information possible with both ground penetrating radar and vacuum excavation services, but it’s important to always be cautious when working around areas with existing utilities.If you need help clearing up the utility myths within your work site, our team at Trinity can help locate subsurface utilities and structures at your site. Visit our website to find out all of the services we have to offer.

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