How locators and vacuum excavators work together to mitigate jobsite damage
By: Chris Thompson, Vacuum Excavation Product Manager and Rudy Cabello, Utility Locating Product Manager at Subsite
Strikes or cross bores can be costly and dangerous for an underground construction jobsite. As the industry evolves and underground environments become more complex, keeping crews safe and jobsites on schedule has become a team effort. Everyone plays a part in damage mitigation, and locate technicians and vacuum excavation operators are two of the key positions.
Locating a jobsite is the most efficient way for contractors to avoid underground utilities and prevent damage, while exposing utilities with a vacuum excavator is the best way to prevent a utility strike or cross bore. With both processes, underground construction crews can navigate around existing utilities.
Locating Best Practices
The first step to a successful underground construction job is locating utilities. Contractors need to call 811 before digging, but what does the actual locating process entail?
First, a locate technician must connect to a utility and find the correct frequency to send down the line. Their goal is to trace that frequency through the ticketed area.
Different frequencies have different benefits, but the main challenge to consider when selecting one is jobsite interference, which can disrupt locater data. There are two types: Active interference comes from sources with an electrical signal, such as cable lines; passive interference comes from sources without a signal, like chain-link fences.
Locate technicians should identify any interference before beginning a locate. It’s also good for them to begin at a low frequency between 263Hz and 870Hz and move to a higher one, like 8.0lkHz. While higher frequencies are easier for locators to detect, they run the risk of bleeding off. Locate technicians should also avoid developing a “favorite” frequency, as it may not be the best choice for every jobsite.
Properly Exposing Utilities
While locating utilities is the first step, exposing or “daylighting” them is the most thorough way to avoid strikes or cross bores. Unlike locating, which only tells contractors where utilities are, daylighting lets crews see and avoid them.
There are three reasons to do this: First, a utility needs to be exposed if it’s in the path of installation, even if it was found at a different depth than construction. Second, exposing a utility ensures it doesn’t veer into the path of construction, something typically done by potholing when working parallel with a utility. Third, double-checking a locate by exposing the utility will reduce the chance of a strike.
Soft excavation with a vacuum excavator is the best way to mitigate damage, although following best practices is pivotal. Contractors need to keep water or air pressure below 3,000 psi, hold the vacuum nozzle eight inches away from the utility, and move it consistently.
In This Together
As demand for underground construction increases, keep in mind that underground professionals are in it together, and locating and excavating utilities will help both contractors and locators be safe and successful You can stay efficient and avoid unnecessary downtime by getting the most accurate locate possible and exposing utilities safely.
