Utility Detection and Surveying

Advanced Investigation Systems undertakes underground service detection to ensure that our Clients can carry out safe intrusive investigation work that meets HSE obligations (HSG47, Avoiding Danger from Underground Services) and CDM regulations.

The detection, identification and accurate tracing of utilities, prior to ground investigation works commencing, reduces the risk to operatives and prevents damage and subsequent costly repairs to underground plant (ie: gas, electric, water, telecom, surface water and foul water (sewer) drainage systems).

Radiodetection
We employ the electro-location (radiodetection) techniques to locate utilities. Using these systems, both metallic and power carrying underground services can be quickly located and traced. Both passive and active electro-location methods are used to detect and trace services:

• Passive methods use the electro-magnetic fields already present    around the underground utility. These can originate either from a    flowing electrical current or ambient ‘natural’ radio signals    concentrated within a conductor and re-radiated.

• Active methods employ artificially generated signals from an external    transmitter and can allow different services to be individually    identified. In addition, it is often possible to determine the depth of    the service in this mode. The transmitter can impart a signal to a    service either by direct connection or remote induction. Direct    connection involves the application of an active signal to a    conductor using a clip, magnetic clamp, cable clamp or mains signal    injector. Remote induction involves a signal being radiated from the    internal antenna of the transmitter where it is induced to any    conducting services in the vicinity and re-radiated and detected at    surface. Generally 33KHz frequencies are used for active methods    for unambiguous signal detection.

Pipe Tracing Cable & Sondes
Drainage pipes can be located, traced and depth determined when radiodetection units are employed in conjunction with a flexible tracing cable and sonde, facilitated by the lifting of all manhole and inspection chambers, gullies and valve covers.

Cover Locating
Specialist metal detectors are used to locate significant buried metallic objects such as inspection covers, drums, tanks etc.

The depth of investigation will depend on the conditions of the site. In general, radiodetection will detect services up to 3m below the ground surface.

Service Level
Several levels of utility detection are available and the one most appropriate to both the nature and size of the Site can be selected to give the most cost effective coverage. Service levels range from a sweep of limited areas such as borehole and/or trial pit positions to a comprehensive site survey with utilities traced and marked to their full extent across a Site.