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Minimising risk and maximising client benefit

The Australian Standard, AS 5488-2013, Classification of Subsurface Utility Information (SUI) enables more reliable information about the location and condition of subsurface utilities to be sourced. The SUI delivers vastly improved public safety and reduces the risk of damaging existing assets.

Developed by Standards Australia Committee IT-036, Subsurface Utility Engineering Information, the new standard provides utility owners, operators, and locators with a framework of consistent classification of information to manage subsurface utilities.

The standard delivers greater rigour around dealing with underground assets, which translates to savings in project time and money.

The standard builds on previous research that indicated the subsurface utility engineering process provides considerable cost-savings, if procedures are undertaken at the earliest phase of a project. Early implementation enables designs to be altered to ensure utilities are avoided and/or utility relocation can occur during the construction phase.

In a study commissioned by the Pennsylvania Department of Transport in the US, researchers determined that on average for every $US1 spent on SUI there was an average saving of $US21. With those figures in mind, there is no doubt that subsurface utility engineering has an important role to play in construction, energy, geotechnical, transport, mining, environment and defence projects.

In Australia, Cardno is a leading provider of mapping and management of existing subsurface utilities, and excavating within high-risk and sensitive environments. Cardno has a strong track record in helping clients to deliver projects that don’t disrupt services, fracture assets, require design amendments, and/or cause disputes or injuries.

In addition to the company’s Australian expertise, Cardno is also a market leader in subsurface utility engineering in the US and has contributed to the development of SUI Standards in the US, UK and a standard for Canada is currently underway.

Understanding the process

Using principles of civil engineering, geophysical methods, surveying and mapping techniques, non-destructive vacuum technology and asset management practices, subsurface utility engineering professionals identify and classify utility information for various quality levels, providing accurate information on the vertical and horizontal position of utilities, which allows utility conflicts to be resolved before any damage or delay occurs.

The four quality levels of SUI can be implemented individually to meet the needs of a client; however, it is more advantageous for them to be used collectively to obtain a comprehensive understanding of utilities within a project.

  • Quality Level D: Gather utility records from all available sources. This can be completed by contacting communication and utility companies, contractors and/or site personnel directly who have a historical understanding of the site. All information obtained is then compiled into a composite drawing and labeled as Quality Level D.
  • Quality Level C: A site visit is made to identify visible surface features associated with existing underground utilities (e.g. hydrants, manholes, valves). This information is added to the composite drawing completed during the Quality Level D investigation and known as Quality Level C.
  • Quality Level B: At this point a decision is made as to which utilities may have an impact on the proposed design and require further investigation. Using a variety of geophysical techniques (e.g. pipe and cable locators, ground penetrating radar), the approximate horizontal and vertical position of these utilities is determined. This information is compiled into the utility drawing as Quality Level B data.
  • By taking utility information from the Quality Level B data and referencing it with the proposed design, utility conflict areas are identified and organised in a database known as a conflict matrix. The conflict matrix identifies potential conflicts (e.g. existing utilities crossing the path of the proposed design) and allows the designers to make educated decisions regarding relocation of utilities or project redesign. Many times, significant conflicts will appear on the plans, the cross-sections, drainage profiles, and staging plans.
  • Quality Level A: Once potential conflicts are identified, the final step is to verify utilities at recognised conflicts, by vacuum excavation. Data obtained at this stage includes, the exact size, material type, depth and orientation of the utilities being investigated. The test whole information is surveyed and included in the utility drawings, which are now certified as Quality Level A information.
  • The additional data gathered from the completed test holes is added to the conflict matrix. At this point, designers are able to review all options the conflict matrix presents and decide the most economical course of action.

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