Surface markers such as stakes, flags or paint can be obscured by vegetation or destroyed by weather conditions or vandalism. 3M has been investing research and development dollars for more than 30 years to investigate solutions to enable location and identification of underground assets. The company has over 25 million markers buried worldwide. The latest version of the markers uses RFiD technology to enable unique identification of underground utilities.

How does it work?

The electronic marker system (EMS) iD balls can be programmed to include customer-specific information such as facility data, type of application, material type, size, placement date and other important details. The iD markers come programmed with a unique number, which is also attached to the marker on a removable bar-coded tag for future reference. Additional information can be programmed and locked by the user via the series locators.

EMS markers are passive antennas with no internal power source that runs down and they will function indefinitely. The locator transmits a radio signal to the buried marker. The marker reflects the signal back to the locator, and the location is indicated by both a visual meter reading and an audible tone.

When sent a ‘read’ command signal, the iD markers respond with the data previously stored. Read data may be easily transferred to the user’s PC for future reference or sent directly to select GPS/GIS mapping devices for real time mapping. The iD markers 100 mm diameter makes them easy to drop in a standard sized trench and they can be located and read from a depth of 1.5 metres. The free-floating design in a tough polyethylene shell ensures that the self-levelling marker is always in an accurate horizontal position, regardless of how it is placed in the ground.

3M highlights that the product is time saving and will also reduce disruption. New Business Development Manager Phil Rowlands said “The marker technology will quickly get you to within a spade’s width of the position above the marker allowing an accurate dig.” The use of RFiD technology allows for unique identification of a particular point in the underground asset. This can both facilitate asset management and also can store relevant information on the chip such as whether someone else’s asset is nearby or overlapping. “We have a range of markers suited to either new installations or retro-fit,” said Mr Rowlands.

In the trenches

The need to identify buried features is highlighted by the US Office of Pipeline Safety. In the first six months of 2006, there were 16 incidents of third-party excavation damage to natural gas distribution pipelines at a cost of $US1.22 million, one related death, and two serious injuries; and four incidents of third-party excavation damage to transmission pipelines, which totalled $US173,000 in damages.

BP Gas adopted iD markers for protection of rural road pipeline crossings in northwest New Mexico USA, which oversees 8,850 square kilometres in three counties, including several thousand natural gas wells and nearly 500 rural road pipeline crossings. Road crews need accurate and dependable information on the depth of every pipeline before they can safely grade a road. Since BP’s ground-disturbance policy forbids mechanical equipment within one metre of buried facilities to safeguard against injury, shield the underground infrastructure from damage, and protect the environment, iD markers provided a practical solution.

BP began marking every road crossing in the region, using three programmed ball markers per crossing; one over the pipe on each side of the road and one in the centre of the road. The marking program allowed the distance from the ground surface to the marker and distance to pipe to be recorded, making calculation of the total surface-to-pipe distance for each marker easy. This means that contractors can now access maps with the correct location and depth of each buried gas line crossing and BP plans to periodically monitor gas line depths throughout the region.

BP anticipates measurable cost savings with 3M’s iD markers, as they eliminate the need to periodically pothole each road crossing to maintain accuracy of pipe depth records.