On the night of Wednesday 23rd January a rain event caused an existing brick culvert to blow out under a property in Moir St. The culvert was a 640mm dia. brick structure pre-dating the property that was constructed in 1892. An amazing piece of engineering that is at the end of it’s life.
The asset had been blocked with debris that was caught on a communications service that had been drilled through the culvert. The resulting blow out undermined some of the foundation piles of the house, undermined the driveway and lifted the concrete footpath. It caused debris to blow out into the basement and into the street. A bit of a mess.
On 25th January WWL and GPFL attended the site to put together a plan to repair the damage and get the culvert back into operation. By 7th February the culvert was back in operation, the house foundations had been repaired, the manhole had been replaced and the road had been put back together. Concrete for the footpath and driveway followed over the next couple of weeks.
Moir St is a typical narrow Wellington street in a built up residential area. The available space for construction was tiny and had to be negotiated with the residents. The street is a dead end meaning that access for plant and vehicles to the workface was a real challenge. Our traffic management team did an outstanding job of keeping things moving for the work and the residents.
We engaged a specialist to assess the stability of the structure and install an arrangement to support the undermined piles off the adjacent piles. Once this was completed we were able to dig out the blockage, get the culvert flowing and create a launch pit to make an access into the culvert.
We slip lined the existing culvert with a 560OD PE100 SDR17 pipe – the largest that could be fitted. This task was a real challenge as there is no access to the upstream end of the existing culvert. A pipe of this diameter is fairly inflexible and the available space for a launch pit was limited. With a can do attitude and a bit of Kiwi ingenuity the team on site got the job done.
Confined spaces were identified early in the delivery as a potential risk that would need to be managed. With no access to the upstream end of the repair; connecting the liner to the existing pipe and manhole was a bit of a puzzle. GPFL wanted to eliminate any requirement for a person to enter the pipe so we installed a CIPP patchliner to seal the liner to the existing culvert and manhole. An engineering solution that put People First.
A key feature that made this project a success was the way the way that all of the parties in the supply chain were able to collaborate and deliver a solution that was the best outcome for the customer. On Moir St the delivery of the product was complimented by a strong focus on the customer experience. We were working in peoples gardens, in the access to their property and outside their living room windows. We undertook to get to know the property owners and tenants who had been affected by the incident and would be affected by the work. We distributed regular email updates so that the stakeholders were kept up to date with progress. They understood who to talk to if they had any issues to raise and the project was able to work with them to manage access to the street and to the properties as required.
We reacted quickly to respond to an emergency repair situation on the Stormwater network. We collaborated with WWL to develop a solution and then we successfully executed that solution on site. The result was an operational asset in only 14 days from go to whoa. We focused on customer experience throughout the delivery – minimising disruption caused by the original blowout and subsequent construction works was a key deliverable of the project. We engaged with the affected stakeholders and kept them up to date throughout the work. Feedback during construction and after completion has been excellent. Even through the project was on the fast track we kept Health and Safety at the heart of the planning and execution of the work. By implementing an engineering solution that eliminated confined space working we demonstrated that we put our people first.
The WWL Contracts Officer responsible for managing the operational asset was satisfied with the result and said:
“Having Contractors, like GPFL that WWL can rely on to react quickly and effectively is critical to maintaining an operational network.”
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Damage to the existing culvert
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Sliplining with a 560OD PE100 SDR17 pipe
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Before
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After
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