Would you like to learn more about what happens during an underground utility detection survey? You have come to the right place! The following information is a brief guide into the survey methods we commonly use to undertake an underground utility detection survey (PAS 128, Type B Survey).
What is an Underground Utility Detection Survey?
An underground utility detection survey aims to give information on the position, depth and type of underground infrastructure. Records are obtained from all asset owners and are used during the survey as a guide to the expected position of the infrastructure. During the survey, each of the assets are searched for using both Electromagnetic Location (EML) and Ground Penetrating Radar (GPR).
Using Electromagnetic Location
Most utilities that have conductive properties can be detected by using electromagnetic location (EML). An operative can apply a known frequency to a cable of or pipe with a metallic composition using a signal generator. This creates an electromagnetic field and is detected using a handheld receiver. The information of the assets is marked on the surface using temporary spray paint. The signal can be applied in a variety of ways that may include cover lifting, direction connection or induction methods.
Using Ground Penetrating Radar (GPR)
Ground Penetrating Radar (GPR) is commonly used to detect metallic and non-metallic utilities. An antenna is typically pushed in a trolley configuration with the data that is collected viewed on a laptop. The system transmits pulses of high-frequency radio waves into the ground which reflects off all buried objects and can detect distinct differences in the earth materials. A reflection known as a radargram can be viewed on the laptop, and from this information the operator can distinguish buried assets.
Recording data from GPR
In many cases, it is suitable to mark the GPR findings on the surface of the ground with temporary spray paint and to record these markings along with the utilities detected using EML techniques as previously mentioned. The data can also be stored and analysed in an office environment after being processed which allows for further filtering and production of results.
To collect this data, a grid can be marked on the ground for the GPR operator to follow and record. A towable multi-polarised array capable of capturing the grid in one direction using a GPS or a Total Station for correct positioning can also be used. The method of recording depends on the site and project needs, and the technique used is largely dependent of the accessibility and time available for the survey.
The perfect combination for a Utility Detection Survey
EML and GPR are the most common techniques, and both should be used to provide the best chance of detecting known and unknown buried assets. There are limitations present in each method when used alone, however combining these techniques, along with records and experience can provide invaluable information for the life-span of a construction project.
To preserve the survey and create a map, the detected utility markings and topographic features of the survey area are recorded using geospatial techniques. Total stations, Global Navigation Satellite Systems (GNSS), laser scanning and other land surveying principles are used to achieve this. The information collected can be used to project drawing in 2D and 3D models for the client.
What are the benefits of a Utility Detection Survey?
When implemented early in the design phase of a project, this survey can eliminate many costs and delays due to unexpected encounters with underground utilities.
There are many advantages which are obtained from a well-executed detection survey, including:
- Improvements in the safety and wellbeing of the workforce and public
- Risk Management
- Minimise utility damage and associated costs
- Minimise project delays
- Allow for efficient planning and design
- Avoid unnecessary and abortive work
- Non-intrusive survey method
If you are interested in the Utility Detection services Catsurveys have to offer, please do not hesitate to contact us today for a quote!