Accurate as-built information is critical for infrastructure construction and utility locating alike. However, as-built documentation is frequently incomplete, out of date or simply not available. This leads to numerous challenges for designers and engineers delivering projects. This article explores what "as-builts" are, why they are so important to utility mapping, the issues within the industry, and what can be done to improve for the future. 

What are as-builts?  

As-builts refer to the final set of drawings and documents that depict the physical attributes of a structure or utility system as it was constructed. They enable a side-by-side comparison of the originally designed specifications, against all modifications made during the construction process, showing precise dimensions, geometry, and the exact location of every element completed under a contract. The accuracy of as-builts plays a pivotal role in ensuring the success, safety, and sustainability of infrastructure projects. 

Why are accurate as-builts so important for the infrastructure industry? 

As-builts play a crucial role as the authoritative record of a completed project. These records are important resources serving as essential references for future projects, maintenance, renovations and expansions. They also evidence that the constructed infrastructure aligns with the approved designs and complies with regulatory standards. This documentation also becomes instrumental for stakeholders in identifying any deviations from the original plan. 

When inaccurately documented, however, they can foster misunderstanding, disputes, and even legal challenge. 

In the worst-case scenario, inaccurate, or incomplete as-builts can, lead to utility strikes during construction. Excavators relying solely on poor as-built documentation when digging can end up causing physical harm or even death, and damaging utilities, leading to costly repairs and project delays. 

What is the current problem with as-builts? 

Historically, as-builts have been created by engineers or contractors in formats that reflect an individual’s interpretation of a site. For example, older as-builts may consist of handwritten notes on utility locations using land markers that, over time, may have shifted or even been removed. 

There is no recognized standard for as-builts, so each asset owner defines their own requirements based on their own needs. As a result, as-builts cannot be compared directly or mapped in a common environment. 

Finally, due to budget and time constraints, some as-builts are simply not completed at all by the contractor on the project site, and information is copied directly from the design plans into the final document – regardless of whether changes happened on the ground during construction. 

Other issues arise as historic as-builts are rarely supported with photographic evidence or sufficiently detailed drawings. Throughout a project’s timeline, as-built records can pass through several hands; multiple versions are created, which then need to be consolidated at the end of the project to create a complete data source.

Reveal has found the lack of standard practice is particularly evident when sourcing utility plans from asset owners to inform project planning, with each owner having several years of dated plans in different formats, from paper, PDF, 2D and 3D CAD.  This often leads to conflicting data sets and utilities being discovered several meters away from their documented locations.

This has led to utility strikes, where utilities have been damaged during digging.  Depending on the severity of the strike and the critical nature of the asset, utility strikes can set projects back days, to years, and cost from thousands in direct and indirect costs, to several million dollars. 

In a paper published by Bahati, P. (2022), several UK-based contractors were interviewed on their encounters with utility strikes, the various causes, and the impacts to their projects. The results showed 96% of participants had experienced a utility strike while on site, 88% had financial consequences, and 91% agreed that the strikes resulted in delays. The most common reasons for utility strikes given by participants were poor or missing utility records and utilities laid at shallow depths and not recorded.

In the Utility Strikes Damages Report by USAG, “assets not being on relevant plans” was the third highest reason for utility strikes in 2017 and 2018. Other years saw “assets not being on relevant plans” among the top two reasons for strikes. This issue has stayed as one of the main causes from 2014 to 2019. In addition to this, “inaccuracy of plans” has been amongst the top four reasons throughout the six-years.

These findings are consistent with research into utility records and as-built accuracy over the past decade. Metje et al., (2015) reported that of 187 utility incidents, it was found 52% of the utilities were not shown on the reviewed utility drawings. Out of the 89 that were on drawings, 75 (84%) stated that the location of the asset struck was inaccurately drawn.

The economic impact of utility strikes is well documented with the UK reporting 60,000 utility strikes each year, costing £2.4 billion. In New Zealand, in 2020, 12,861 reported utility strikes had a direct cost to the economy of approximately $89.6 million New Zealand dollars, and in the US, there is an estimated $30 billion in societal costs annually from underground infrastructure damage. A common cause across all economies is that utilities have not been marked, or marked inaccurately, on ‘as-builts’ or on site.

So, what can be done to improve this situation?

As subsurface utility engineers, Reveal know the best time to document precise utility location is during excavation, or relocation, when the ground is open, and the utilities can be seen. Providing accurate ‘as-builts’ is the responsibility of the on-site contractor. To improve the accuracy of records, the use of photographs and photogrammetry should be introduced into workflows prior to utility trenches being filled. Photograms in particular can then be georeferenced into GIS software and used to support as-builts with accurate visual location of assets; aiding future projects through risk mitigation from more accurate and complete underground utilities data.  This in turn reduces the likelihood of expensive budget and timeline overruns.

Conclusion

Underground infrastructure is a complex and important environment. If confidence in the exact position of utilities is low or their location is unknown, there will always be a risk of encountering them, resulting in delays and extra cost, that impact project delivery.

As cities evolve towards becoming smarter and more connected, precise, as-built records of utilities will become indispensable for avoiding disruption, optimizing resource allocation, and enhancing overall urban planning. The industry should do better by investing in the time, technology and resources to do the job right.

#Infrastructure #UtilityMapping #WorksiteSafety #AsBuilts