Specialist Installations


250mm and 450mm SDR9 stormwater Rail Crossing by Directional Drilling - 630m of 100mm dia horizontal drain – 30m of 450mm PE and 2 x 50m x 160mm dia subsoil drain outlets installed under North Island Main Trunk Railway Line. Water buildup new pipes to drain water away. Two gravity drill shots under the rail while overhead power is switched off. Subcontract to GHD who are upgrading a slumping area of rail.

Completion of installations via HDD is effective but requires specific rules for working in and around Kiwi Rail corridor. Smythes have successfully undertaken HDD under railway lines, by either thrusting or pipe ramming. This project involved two rail crossings using thrusting methodology.

All drill shots under the rail network were achieved to a high standard and within the allotted time frame. We are proud of our teams ability to work in remote setting within the allowed time frame. All project Health and Safety, Environmental and Quality documentation to meet contractor and Kiwirail standards was achieved; completed within 2 weeks, on budget.


Smythes completed this project for Thermarock Engineering- Ngati Tuwharetoa Geothermal Assets Ltd. Supply and installation of steel casing pipe beneath SH34/ Tamarangi Drive and the Kiwirail line, including supply and construction of approximately 40m of wooden retaining walls and 2 x headwalls within the retained structures, plus 40m of safety fencing above the retaining walls and all reinstatement works including hydroseeding.

Each piece of welding was completed just prior to installation. Sand could have presented a challenge but this was mitigated by Kawerau Mill erecting a high spec retaining wall for the drill’s position; everything went very smoothly. Smythes directionally drilled under the KiwiRail lines successfully amongst existing utilities without issue. Effective process resulted in successful installation within a 2 week timeframe and within very hot conditions of 400C summer days, slightly over budget.

See our Services and Utilities projects