Peka Peka to Otaki Pipe Ramming



Fletcher Construction Infrastructure/NZTA




Apr 2018 – Feb 2019


Mobile Plant Fleet, Rail Crossing, Pipe Ramming

Customer Type:



Installation of 3no. 12m long 406.2mm casings under the rail corridor by Pipe ramming

Installation of 180m of 406.2mm casing by open trenching

Installation of a 40m long 608mm casing under SH1 by Pipe Ramming

Peka Peka to Otaki (PP2O) is an extension of the RONS project north on SH1. It is a complex infrastructure project being undertaken by Fletcher Construction Infrastructure on behalf of NZTA. The project includes a series of service diversions and renewals associated with changing the alignment of the main carriageway and the NIMT rail line that runs parallel to it.

We won a package of work to construct three steel sleeves that would take service diversions from one side of the construction corridor to the other. That involved installation of three sleeves under the existing rail corridor by pipe ramming and extension of those sleeves across the site by open trenching a further 180m. The pipe ramming operation was completed from outside the rail corridor with the rail running live at all times.

Pipe ramming is specialist work and requires the right tools to be used by trained and experienced people. We used a Grundoram Koloss pipe ramming tool capable of ramming casings up to 1200mm diameter and up to approximately 70m depending on ground conditions. Our team has received training from TT Technologies both in NZ and abroad, they have completed a series of successful projects in the region over the last decade.

The ground conditions in this location were large river boulders. These had presented a challenge for the project already and there had been some aborted attempts to undertake horizontal directional drilling in this ground. The pipe ramming was largely unaffected by the boulders with the operation going to plan. The team did experience some difficulties in cleaning out the casing as some of the boulders were almost a tight fit inside it. We persevered and handed over a high quality product.

Following on from the success of the first three pipe rams we were approached by the project to ram a 40m long casing under SH1. We proposed a 508mm diameter casing in order to mitigate the issues caused by the large boulders during the first rams. The casing was rammed in 12m lengths each joined to the previous with full penetration butt welds. Similarly to the previous rams this work was completed from outside the road corridor and with the carriageway live at all times.

By selecting to ram these crossings rather than construct them traditionally the project was able to avoid interruption to services on strategic road and rail networks. This eliminated some significant risks associated with working in a rail/road environment, working out of hours and undertaking deep excavations. It allowed the project to deliver to a tight programme despite difficult ground conditions.


An example of the boulders that were cleaned out of the installed casings.

A section of casing that was installed by open trenching.