How might better detect, identify and map out underground utilities without the need for excavation?

Water Supply (Network) Department, Water Reclamation (Network) Department - Project Management Division

Sewer and water pipe construction typically involves deep shaft excavation, open cut, micro-tunnelling, and pipe jacking works. Prior to carrying out any work, it is critical to identify all existing underground utilities and verify their exact locations and depths, so as to prevent damaging them or to divert them before constructing the pipes. Currently, the detection and identification of underground utilities are done by referring to drawings, and trial trenching. Trial trenching is a process whereby small trenches are dug to reveal the underground contents. However, this process can be inefficient and increase the amount of time, effort and costs required to seek approval to allow trenching in the following scenarios: 

●  The utilities are under major roads with heavy traffic;
●  The alignment of the utilities is inaccurate and multiple trenches are required to locate the utilities; and/or
●  The utilities are buried too deep and require the design and submission of Earth Retaining and Stabilising Structures for the trenching work to reach the desired deep depth. 

Currently, there is no alternative method to reliably and comprehensively detect and identify existing underground utilities other than to physically expose the utilities by trial trenching. 

The pipes could be installed to depths of 1m to 40m. Besides pipes, common utilities found underground are telecommunication cables (typically at shallower depths of 1.2m to 3m) and power cables (at depth of 1.2m to 5m). 

Some of the common materials of water and sewer pipes are ductile and cast iron, steel, reinforced and polymer concrete, and vitrified clay. Electrical cables and telco cables are normally housed in protective sleeves using HDPE/PVC pipes, however certain stretches may not be housed in protective sleeves at all.

We are interested in solutions that support the detection and identification of underground utilities and services. The solution must be able to function without causing any interference or disruption to the utilities and their environment. Ideally, the solution should provide better accuracy and easier execution over conventional solutions.

Other than determining the presence of underground utilities, the solution should also differentiate the type and characteristics of underground utilities found (eg. Material, width) accurately and precisely. This information will validate our findings and further assure relevant utility owners that their services have been accounted for before commencement of excavation works.

●  The detection range is able to reach depth of at least 3m, but methods with an extended range of 5 meter or more would be more advantageous and favorably considered for implementation. 

●  The detection method shall maintain high accuracy even if there are interferences from road compositions, soil geology, environmental factors, including the presence of groundwater. 

 ●  The accuracy of detection should consistently be within a tolerance of +/- 0.1m which is important if the result is to be used to guide underground pipe construction. 

●  If your solution is able to differentiate utilities that are closely stacked, please include the details of your detection and identification method in your proposal.

Electromagnetic locator
●  Mainly effective in detecting conductive materials
●  Not effective in differentiating power cables that are closely laid or stacked 

Ground-Penetrating Radar (GPR)
●  Validation on the technology’s ability to detect utilities under the effect of external interference, such as groundwater, soil conditions, and the presence of other utilities, is required.
●  The current GPR solution has only an effective detection range of 3m
●  Post processing of the data is needed to support the interpretation and visualisation by officers
●  The collected data might have insufficient information to distinguish between different types of utilities 

In addition, PUB has been liaising with vendors who are researching into the use of cold atom interferometry-based sensing for underground mapping and is open to learning more about new innovations for this technology type.

Upon request (email to pub_openinnovation@pub.gov.sg)
●  Example of a trial trenching report (includes drawing and recorded pictures) 

After selection
●  PUB work sites as test sites

Total project period : less than 18 months
Solution development : up to 6 months
Testing and review of the solution : up to 6 months
Establish reporting outputs : up to 3 months

A site-tested prototype system that is able to detect, identify and differentiate the various underground utilities to depths of at least 3m, without the need to physically expose the utilities. The system should have a display to provide a real-time data output for on-site investigation. Post-processing of the data should be generated into a report format (minimally with a cross-sectional drawing of the area detected and spatial information of the detected utilities) to reliably guide future underground pipe construction.  

If the pilot is successful, the solution would be recommended to PUB’s service contractors.