Auckland’s Ferry Building is an historic landmark in the New Zealand city. In the 100 years since it was built, the sea wall supporting the structure was gradually eroded by constant sea movement and wash from ferries docking and leaving the port.
Divers discovered a large three-metre scour at the base of the sea wall that needed to be repaired and stabilised to ensure the safety and longevity of the building and underlying structure. After closer inspection a number of additional holes in the seawall were discovered.
To ensure there was no damage to the building during repair works, Auckland Transport enlisted the services of CKL – a local engineering and surveying firm – to monitor the structure. CKL has done a lot of work for AT in the past and is therefore trusted to deliver reliable and precise results.
Following a presentation by positioning solutions provider Position Partners, CKL decided to use a new wireless vibration monitoring system made by UK-based company Senceive. “Although we continued to use total station measurements as a failsafe and gross error check mechanism, the Senceive monitoring system gave us constant updates on the building and any movements in real time,” said Malcolm Dawson, a senior surveyor at CKL who worked on the project.
The team at Auckland Transport was also happy to know in real time how the building was behaving so that early warning could be initiated in an alarm situation.
Position Partners worked with CKL to position the sensors under the wharf along the sea wall. “Initially we had some difficulties getting the sensors positioned correctly so that the data was transmitted, but the team at Position Partners helped get it setup and working well,” Mr Dawson said.
Senceive nodes can be installed in almost any environment or structure and they work by transmitting position data via a wireless gateway that can be viewed online via a web portal. Position Partners helped to setup alert levels as set by Auckland Transport so that any movement could be prioritised and escalated to the team at CKL accordingly.
“Our experience with the technology was extremely positive and the client Auckland Transport loved it because they could login themselves and get up to the minute data whenever they liked,” he added.
The wireless vibration monitoring setup saved CKL considerable amounts of labour and costs compared with manual monitoring of the structure. “Because we had visibility of the data on an ongoing basis, we only needed to manually check on site once a week,” Mr Dawson said.
“Without Senceive, we would have had survey crews on site every day, so it saved Auckland Transport a lot of time and money in that regard,” he added.
Overall, CKL and Auckland Transport were very satisfied with the setup and results from the project. “We were happy with the product and the data and look forward to using it again on another job,” Mr Dawson said. “Another impressive thing was that after being installed on the sea wall for 18 months, when we took the Senceive nodes off they looked brand new, there was no corrosion or damage despite being exposed to saltwater and the elements all that time.”
With the sea wall successfully repaired, the ferry terminal and building can continue to serve the Auckland community and visitors alike for many years to come.