When a giant sinkhole opened beneath one of Wellington’s main road transport routes, it required a massive operation that disrupted traffic and the lives of residents across the city.

In February 2021 a stretch of stormwater drain collapsed on Jervois Quay. Two lanes of the main arterial route were closed and traffic diverted through the CBD.

Careful examination with ground-penetrating radar and CCTV revealed that the stormwater pipe had cracked in multiple areas. Seawater was encroaching through cracks and joins in the pipe, and barnacles were clearly visible, indicating the damage has been building up for several years.

During the initial cleaning and repair process, the earthenware pipe suffered further collapses, and Reveal’s ground-penetrating radar scan discovered two more areas of concern under the road’s surface.

Sinkholes or voids are rare, but they represent a major hazard for excavating teams that can result in serious injury or death if the ground gives way during digging. They also create significant disruption until the cause is identified and repaired.

Wellington Water wanted repairs completed as swiftly as possible to reduce both the impact to drivers and residents, and to minimize the risk of flooding of the CBD while the stormwater pipe was being replaced. A further hazard appeared, with the drinking water main that supplied most of the inner city also located in the excavation zone.

Reveal’s subsurface data set was able to provide valuable insights to the team on the ground – specifically, identifying the location of reinforced concrete which could have caused serious delays.

Armed with Reveal’s data, Wellington Water cut out and removed the concrete layer under the road, set up sediment control and treatment systems to manage the flow of water through the trenches and laid the first three sections of replacement pipe from the TSB Arena to Jervois Quay, via a trench two meters wide and three meters deep.

The information Reveal was able to discover about the underground network allowed WCC’s engineers to create a detailed remediation plan and work much more efficiently. Work that would have required more than six weeks was able to be completed over the course a holiday weekend.

Wellington Water Group Manager of Network Delivery and Development Tonia Haskell said “I’m exceptionally proud of what we’ve achieved in a very short amount of time with a team that have collaborated, problem solved and worked hard and effectively, to bring this project in ahead of time and with a high quality result.”

These types of discoveries demonstrate why proactive subsurface mapping and establishing a true and accurate picture of the underground environment are critical for civil engineers and planners. High risk environments need to be thoroughly mapped and managed before they turn catastrophic, and the information shared with all stakeholders so efficient and collaborative decision-making can take place.

By using platforms like RevealTwin, we can help reduce the number of workplace accidents and the time spent on repairs to city infrastructure, benefitting contractors, ratepayers and residents.