Vacuum excavation, also known as soft digging, is one of the ways we make important observations about utilities. Vacuum excavation gives you an absolute positive location of your utility services. It’s what separates Quality Level B and Quality Level A utility data. However, vacuum excavation is not always used in the utility locating process. Why? How do you determine when vacuum excavation is needed? How do we know when scanning data may require additional test hole investigations for a fuller picture of the puzzle?
To start, we’ll have to talk about non-destructive testing and its benefits. The obvious benefit to scanning is that it’s not invasive to existing construction (other than spray paint and flags). Both electromagnetic detection and GPR scanning services rely on transmitted radio frequencies and electro-magnetic fields that can be read and interpreted from the surface. It doesn’t rely on any digging to understand what’s under the surface and can be used on the ground, walls, columns, and more to locate utility lines and other structural features.
It wouldn’t be recommended to just rely on Level A utility data without gathering levels D through B first. If you had to dig everywhere to find utilities using vacuum excavation without radar, surface features, or other existing information – you’d just end up with holes all over the place without any methodology or plan to determine where to dig. That’s why vacuum excavation is considered a supplemental service to Level B scanning and a quarter of the overall subsurface utility engineering investigation process. The only time where vacuum excavation stands alone is by replacing mechanical excavation as a safety precaution.
Sometimes, scanning may tell the story of an area full of congested and overlapping utilities. Scanning even along a straight line can find multiple parallel utilities eventually weaving over top of each other. We’ve been able to find areas where ten different lines overlap with each other and soft digging a test hole reveals the true nature of the intersections. In these cases, test holes would be beneficial to understand how they overlap and we’d recommend it if it’s not already part of the scope. It can also help identify unknown structures that may have been abandoned.
Another situation is understanding the depth and direction of a utility. After performing a scan, you may get a rough estimate of the depth of a line, but not always exact due to various soil conditions. Vacuum Excavation is vital in determining true elevation for tie-in of wet utilities to existing infrastructure. Level B data typically focuses on getting accurate horizontal data rather than vertical data as a result. Digging a test hole will tell you how far down a utility is, what direction it’s facing, and information about the material and size of the line. In some cases, test holes will be dug in multiple areas along the same marked out line to see if there are any changes in elevation.
Each locating technique offers something to the overall package of subsurface utility engineering, and vacuum excavation is an important part to making sense of findings along with other investigation methods. That’s why our team at Trinity Subsurface performs utility locating, air and hydro vacuum excavation, video pipe inspection and more to create a full suite of services. Give us a call or visit our website to find out more information on how we can assist on your next project.
