In order to accommodate increased waste water flows from the local Heinz Watties plant nearby who wish to cease disposing of their waste to land, the existing DN525 waste water main required upgrading between Hayton Road to Alloy Street and Nga Mahi Road. Part of this upgraded alignment passed under the Kiwirail rail corridor. As the rail corridor had to remain operational at all times, this necessitated this 37m length of main to be replaced using trenchless techniques.
This project required construction of large diameter pipelines, temporary works, traffic management, working around services & service relocations, live sewer flows including managing bypass flows, road construction and reinstatement, stakeholder management. March was head contractor for the new gravity trunk sewer pipeline comprising DN900 & DN1000 Perfect Pipe (up to 4.5m deep), PVC collector pipe/laterals, manholes, a large, lined manhole (over 100 tons of concrete), and design/construction of a bypass to construct the in-situ confluence structure over the existing sewer pipe.
To address the ongoing H2S levels in the sewer network, the pipe was lined with PE and manholes were either coated with Situclad EHD or a PE liner. March was the first contractor to install the Perfect Pipe system and underwent training with the Hynds technical team to ensure pipe was installed in accordance with the manufacturers guidelines. The works included 36m of pipe installed by micro-tunnelling under a live KiwiRail corridor. March utilised the expertise of Rob Carr to overcome challenging ground conditions to successfully complete the tunnelled section.
The entire works involved the installation of sheetpiles to shore the excavation and provide a safe environment to lay the pipes. The construction of the large cast in-situ downstream manhole required the design and installation of a bespoke sheetpile system, also incorporating a gravity wastewater diversion to divert the 900mm diameter existing flows around the works. All temporary works were designed in house. The micro-tunnelling operations required significant temporary works including a working platform, concrete entrance ring and concrete thrust block, all of this within a sheet piled excavation