Construction – Quark Scan

07 Jun 2022

Electrical conduits embedded in concrete have been marked through scanning — can we drill/core in cleared spaces near them?

Concrete Scanning, Construction, Ground Penetrating Radar, Underground Utility LocatingConcrete Scanning, Ground Penetrating Radar, utility locating

The answer to the question seems to be obvious. Since the electrical conduits have been marked through scanning, why can't we drill/core in those cleared areas? We will keep a few inches away from those marked conduits, isn't it good enough? Unfortunately, it might not be. Are you telling us that the conduits are not marked accurately? Well, ground penetrating radar (GPR) can be as accurate as within an inch in finding conduits and other objects embedded in concrete. However, GPR accuracy is not the main issue here. The main issue lies in the limitations of scanning technologies. Due to the nature of scanning methods including GPR and cable/pipe locators, generally there are no guarantees that all conduits can be…

18 Nov 2021

By Shan Wei

Cross-polarized GPR scanning – a useful technique for locating utilities embedded in reinforced concrete

Concrete Scanning, Construction, Ground Penetrating Radar, Underground Utility LocatingConcrete Scanning, GPR, Ground Penetrating Radar, underground utility locating

Above is an image showing two concrete ground penetrating radar (GPR) scanning profiles along the same line with normal and cross-polarized antenna orientations, respectively. Although the electrical conduit is visible in both profiles, it's easier to spot it in the cross-polarized profile than in the normal orientation profile. In the cross-polarized profile, the reinforcement's signature pretty much disappear; the conduit's signature also dials down, but remain very noticeable. So their differences are greatly amplified in the cross-polarized profile compared to the normal orientation profile. This tells us that the two signatures most likely represent two different objects, and it's most likely caused by the difference in their diameters. Of course, there are other possibilities such as differences in orientations or…

27 Oct 2021

By Shan Wei

Underground Utility Locating: Access! Access! Access!

Construction, Underground Utility Locatingunderground utility locating

During a survey for locating underground utilities, access to the survey area is apparently needed. However, due to the lack of understanding of how underground utility surveys are conducted, survey sites are often found not prepared well for access after surveyors arrive. As a result, survey results are often less ideal and sometimes surveys are not effective at all. Most people understand that a survey area needs to be “scanned”, so the access to the survey area, at least in a walkable condition, should be granted. However, this is only the minimal requirement for the access. The whole access issue is far more beyond that, especially when the ground penetrating radar (GPR) depth is limited. When the GPR performance is…

15 Oct 2021

By Shan Wei

Provide utility maps to your underground utility locators whenever possible

Construction, Ground Penetrating Radar, Underground Utility Locatingunderground utility locating

Before scheduling a private utility markout service for your site, try to find related utility maps whenever possible. They might provide important clues for utility locators to locate some underground utilities. Of course, there are many utilities buried without any records. Also, if there are records, they could be inaccurate or outdated. But it doesn't mean they are not useful. Underground utility locators work like detectives: not every clue is useful and some might be even misleading, but some clues could lead to important discoveries. For the best result of underground utility locating, try to help your utility locator by feeding him/her with clues such as utility maps, historical documents, or even telltales about the site. During an underground utility…