Today’s job sites are becoming increasingly more complex and congested. With a plethora of underground interferences, properly locating a job site is the most effective way for contractors to stay safe and successful. So, whose job is it? As the industry has evolved, damage mitigation has become a team effort with two parties playing key roles — utility locate professionals and vacuum excavation operators.

While locating has been the standard for avoiding underground utilities, vacuum excavation has quickly become an essential tool in the process. In fact, exposing utilities with a vacuum excavator is the most surefire way to prevent a utility strike or cross bore. But it’s not one approach or the other. Using both methods can help keep people safe and minimize costly downtime.

SUCCESSFULLY LOCATING A UTILITY

The first step in any underground construction project should be to call 811 and have a utility locating professional come out to the job site to navigate the underground blueprint. From there, contractors can work to develop an educated construction plan.  

When utility locate technician arrives, they’ll use a locator to connect to each utility, find the correct frequency to send down the utility line and trace that signal through the ticketed area. The key to tracing the utility through the entire job site is identifying the right frequency to use. Each frequency level has different benefits, but the main challenge is the possibility of job site interference.

Interference refers to objects or sources that can disrupt or distort the frequency of a locator, making it more difficult to trace the utility and potentially leading to a mislocate. Interference can be both active and passive in nature. Active interference comes from sources that have their own electrical signal — such as underground fences or cable lines. Passive interference comes from sources without their own signal, like chain-link fences. A visual inspection of the job site can help locate technicians identify any signs of active or passive interference.

To find the correct frequency, locate technicians should start with the lowest possible frequency, usually between 263hz and 870hz, and move up to higher frequencies in small increments if they are unable to find the utility. While higher frequencies like 8.01khz are often easier to pick up by a locator — meaning it’s usually easier and faster to complete a locate — they also run a higher risk of bleeding off onto sources of interference, which can lead to a mislocate.

Finding and following the best frequency will allow locate technicians to accurately trace and mark a utility, helping contractors better understand the job site and plan their construction path to mitigate damage.

EXPOSING UTILITIES TO SUPPORT DAMAGE PREVENTION

The next step in making educated decisions on underground construction job sites is to expose the utilities. When used in addition to utility locating, which gives contractors a readout of where utilities are, exposing a utility enables contractors to see it and ensure that they avoid it. There are three primary reasons contractors take the time to expose a utility, also called daylighting.

If it’s near another utility. A utility should always be exposed if it is near a new utility installation, even if the locate technician found the utility deeper or shallower than the level of construction.

If it’s in the path of construction. It’s important to expose any utilities that may veer into the path of construction. This is typically done by potholing when working parallel to a utility. While every municipality will have its own regulations on potholing, this technique helps contractors confirm that a utility’s path is consistent. For example, if construction is 20 feet from a utility, a crew may pothole every 50 feet to confirm the locate.

To get visual confirmation. Visually confirming a locate is the most thorough way to avoid utility strikes or cross bores, which reduces the chance of costly and dangerous downtime.

Soft excavation methods are ideal for this, which is why vacuum excavation has become a popular way to expose utilities. To increase operator efficiency, it is essential that contractors keep their vacuum excavator nozzle 8 inches away from the utility to prevent equipment and utility damage. Air or water pressure should be kept below 3,000 psi and the nozzle should be constantly moving when excavating. This allows for the most efficient and safe excavation and will help contractors expose utilities more easily.

WORKING IN TANDEM

Damage mitigation is a team game, and everyone has the same goal — keep people safe on the job and avoid unnecessary downtime. However, as demand for underground construction projects continues to increase, and more and more infrastructure gets put into the ground, it’s important for all underground construction professionals to work together in lockstep.

Properly troubleshooting interference and finding the most accurate locate helps contractors better understand the job site and plan their construction path to mitigate damage. And properly exposing utilities is the best way for them to confirm there aren’t any additional surprises. When the damage prevention duo comes together, utility locate professionals and vacuum excavation operators can support damage prevention, boost productivity and ensure the success of the job site.

ABOUT THE AUTHORS

Chris Thompson is the vacuum excavation product manager at Ditch Witch; and Rudy Cabello is the utility locating product manager at Subsite Electronics.