AS5488-2013 Classification of Subsurface Utility Information provides a consistent method of conveying subsurface utility information for a variety of purposes throughout the lifecycle of the asset, fit for purpose. In the February 2015 edition of Utility, AS5488-2013 committee member Bruce Potter discussed some of the background to the development of the standard and how it is intended to be used. Now he explains how the standard benefits the lifecycle of subsurface utility information for a variety of stakeholders and the challenges currently experienced.
The lifecycle of subsurface utility information, particularly through the design stages, is a constantly revolving four-stage linked process – Investigation, Design, Construction and As Constructed. Throughout this process, the main stakeholders involved are the utility locator, engineering professional and authority/asset owner, each with a different perspective with a common cause – AS5488-2013.
Of the stakeholders involved in the lifecycle of subsurface utility information, utility locators are currently the most experienced users of AS5488-2013, as it represents their industry. They are frequently called upon to provide recommendations, in particular, for the engineering professional who may be unfamiliar with AS5488-2013 and the equipment and techniques used to obtain utility information.
In the planning stage, the number, interval and physical location of excavations (potholes, strip trenches) and electronic detectable points are invaluable for the utility locator to adequately procure appropriate equipment to meet the tolerances in accordance with AS5488-2013.
Procuring an appropriate vacuum excavation unit for example is largely dependent on the volume of excavated material, taking into consideration operational logistics, including proximity to the site area, terrain, waste disposal and on-board resources. These considerations are in addition to procuring traffic management planning, including permits and the design of traffic guidance systems.
To the engineering professional, knowing where existing, designed and newly-constructed subsurface utilities are spatially located is critical to understand the constraints they face, and to confidently assess and rectify the effects of potential underground utility conflicts throughout various stages of design.
Without a consistent approach to classifying subsurface utility information, the risk of conflicting and inaccurate information dramatically increases. This risk ultimately undermines confidence in knowing which source/s of utility information to trust and how best to utilise this information, knowing they are liable for the outputs and decisions made.
A lack of confidence provides an opportunity to misinterpret; make assumptions by attempting to ‘fill in the gaps’; and then share this inaccurate information, often leading to unnecessary design conflicts, ill-informed design decisions and a misrepresentation of the location and characteristics of a subsurface utility.
The ‘errors’ are transferred onto those involved in construction, causing issues with redesigns, procurement, timeframes, costly conflicts and financial friction by all parties involved.
The challenge for the engineering professional is breaking from current practices of transferring the risks associated with a poor attempt to obtain, collate and convey subsurface utilities, regardless of their status, during the design stage. A design based on poorly-interpreted subsurface utility information questions the validity of the design and brings into contention the legalities of the engineering professional’s duty of care.
In general, engineering professionals are unaware information contained within their utility designs essentially mirrors those in AS5488-2013.
A stormwater, sewer or water main detailed design, for example, would usually consist of sufficient information to construct, including horizontal absolute spatial position (easting, northing & AHS surface level), invert or obvert level (AHD), utility size, configuration, material and trench type, and metadata information including date, revision, and supplementary information contained within notes.
In essence, the utility design shares the same attributes and metadata as Quality Level A (QLA) of AS5488-2013, meaning the engineering professional can adopt this standard as a guide to indicate an appropriate level of utility design information required though the various stages of design.
As a guide, utilities designed during the concept stage generally would require Quality Level D (QLD) accuracy, and utilities designed during detailed design would require Quality Level A accuracy. Quality Level C (QLC) and Quality Level B (QLB) would indicate utilities designed during preliminary and design development stages respectively.
To obtain existing subsurface utility information, the engineering professional has an obligation to properly convey their accuracy requirements by acknowledging the attributes and metadata in each quality level. A general understanding of the equipment used for each quality level, including its associated tolerances and the expected deliverables in terms of point and line data, would greatly benefit the development of a utility survey scope of works.
Many authorities across Australia are either considering, in the process of implementing, or now require newly-constructed subsurface utility infrastructure, utility attribute and metadata information to be documented in accordance with AS5488-2013 Quality Level A (QLA).
This initiative by authorities and asset owners suggests a shift in thinking from previous methods regarding how subsurface utility information is obtained and conveyed from the As Constructed/As Built process, but is limited to newly-constructed subsurface utility infrastructure collected and conveyed prior to backfilling.
The challenge for authorities and asset owners is knowing how to manage incoming As Constructed/As Built and data gap AS5488-2013 information while maintaining an existing database that may not be classified by quality levels.
If inconsistent information is uploaded to the likes of Dial Before You Dig, or provided directly, the end users also receive the same inconsistent level of information.
Currently, Telstra is the only asset owner listed on DBYD who now supplies their data to Quality Level D in accordance with AS5488-2013. Other authorities and asset owners alike have an opportunity to adopt AS5488-2013 and nominate an appropriate quality level on the subsurface utility information they supply.
Ultimately, AS5488-2013 provides the framework and a common language for the utility locator, engineering professional and authority/asset owner, replacing current inconsistent practices commonly plaguing the accuracy of and confidence in of subsurface utility information throughout an asset lifecycle.
Bruce Potter is a current Standards Australia, Subsurface Utility Engineering committee member (IT-036), who represented Engineers Australia in the development of Australian Standard AS5488-2013 Classification of Subsurface Utility Information (SUI). He is a Certified Engineering Technologist (CEngT) experienced in all aspects of civil engineering and utility design and a specialist in the field of Subsurface Utility Engineering, encompassing professional utility coordination, utility data management, field data gathering and utility asset management.