Innovation key to stormwater renewal

Innovation key to stormwater renewal
The project involved replacing two existing stormwater pipes in poor condition, located under the closed landfill on the estate.

The successful completion of the Chelsea Estate Heritage Park stormwater renewals project for Auckland Council demonstrates the capabilities of March Cato to deliver innovative solutions, says company project manager Nicholas Gulley.
The project involved replacing two existing stormwater pipes in poor condition, located under the closed landfill on the estate, with a new tunnelled pipeline 2100mm in diameter, with two drives totalling 450m ranging in depth from 4m to 11m. In addition, a new stormwater diversion was also completed of the existing Huka Road stormwater pipeline into the new pipeline in the Estate Park via a new directionally drilled 355OD PE pipeline.
The project also included diversion of the existing Rawene Road stormwater pipeline to convey flows via a new directionally drilled 455OD PE pipeline to a new outlet in Chelsea Bay, abandonment of the redundant stormwater pipelines and additional works including finalising the design and constructing the 4-metre diameter manholes on the tunnelled pipeline, modifications to existing inlet structures, construction of a new 2100mm diameter outlet and installation of a stormwater treatment device.
Nicholas says it was a complex project due to its size, the fact there are heritage buildings on the site and there is unrestricted public access to the area. The methodology to pipe jack the new major pipelines and directionally drill the smaller diameter pipelines resulted in the safe installation of the pipelines with minimal disruption to affected stake-holders and an overall cost-effective solution.
March Cato‘s technical capabilities and the skills of its team enabled the company to achieve the required horizontal and vertical alignment and hydraulic performance, he says.As March Cato had previously worked for Auckland Council on a number of projects this existing relationship also helped the project to run smoothly, says Nicholas.
“Through the construction phases we worked collaboratively with Auckland Council’s representatives, designers and advisors to ensure the successful completion of this project while meeting the client’s requirements and providing value for money to Auckland Council and its stakeholders,” Nicholas says.
By getting involved early on in the project March Cato was able to come up with innovative solutions to save the client money and create efficiencies enhancing the project flow.
“For example, the original consented design for the pipe jacked section was to install 1950mm diameter pipe from MH 3/1 to MH 2/1 and install 1350mm diameter pipe from MH 2/1 to MH 1/1. “With two different pipe diameters, this would require two tunnel boring machines – which had the potential to add considerable cost to the project if they had to be bought or hired.
“During the expression of interest and request for tender phases, March Cato offered alternatives and the final design resulted in only one tunnel boring machine and one pipe size being necessary,” he explains.

Innovation key to stormwater renewal
The project included diversion of the existing Rawene Road stormwater pipeline to a new outlet in Chelsea Bay.

Other key project outcomes included accomplishing zero harm to the construction crew, client staff and members of the public and minimising disruption to the public and nearby residents. Environmental requirements were also an important part of the project including prevention of the discharge of drill fluids and muds to sensitive environments and minimising vegetation removal and adverse impacts on the park.
Nicholas says that a collaborative approach to the works was adopted from the start of the project including regular liaison between the client, its representatives and the March Cato team. Even with a couple of delays encountered at the start the overall project was completed to the agreed time-frame with approved extensions of time.
“Our track record in delivering trenched and trenchless solutions for varying diameters, in all ground conditions and environments and in accordance with the Health and Safety at Work Act and the Mining Regulations, enabled us to deliver this project safely and on budget. “This project is an example of how March Cato is able to assist clients and their consultants in identifying feasible, cost effective and long-term solutions.”
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