Wairarapa Tunnels Renewals (WMUP3)

Supporting one of KiwiRail and GWRC’s critical and high risk renewal projects in delivery and design.

Vitruvius are supporting one of our key clients KiwiRail and their WMUP management team with multiple vital roles with the WMUPIII Wairarapa Tunnels Renewals Project delivery. What initially began as Drainage Design and Delivery support / MSQA (led by Matt Stuart and Luis Alcaide), has grown to include Engineers Rep to the drainage contract, the Project Director role (Neil Mason), Project Engineer support (TJ Rasmussen) and further Project Management strength to drive the critical laydown constructions with challenging planning and stakeholder requirements (Brad Hunt).

The Remutaka Tunnel (renamed from Rimutaka in 2017), is an 8.8km single bore Railway tunnel constructed from 1951 to 1954 and opened in November 1955, replacing the Rimutaka Incline railway that had made its way over the Remutaka Hills since 1878 (now known as the Rail Trail to local hikers and bikers). The tunnel runs through New Zealand’s Remutaka Range and is the second longest railway tunnel in the country. The location of this tunnel and the regular use for freight and passenger services makes maintenance periods difficult to come by.

The majority of the components within this tunnel have not been replaced since the track was first constructed in the 1950s and the windows for renewals are particularly short given the amount of drainage and track that is to be renewed throughout, requiring an innovative and collaborative approach to construction. The hard deadlines for construction require designers, contractors, project managers, programmers, construction managers and commercial teams to work closely together to provide a proactive and safe plan of attack. The success of this project will come down to each stakeholder feeling a part of the team and buying in to the project goals.

 

Drainage Design & Delivery:

Designing a drainage system in a tunnel environment that is able to be safely removed, recycled at the next renewal and takes into account productivity / available track time is no easy feat. Vitruvius are undertaking the lead role on the drainage design for both tunnels. One of the more complex principals requirements was to design a drainage system that could withstand the loads from track panel lifters that were to be utilised to complete track relay works through both tunnels. The solution also had to convey an unknown flow rate through the short c. 650m Maoribank and the significantly longer c. 8.8km Remutaka tunnel. Following initial site investigations, remote flow rate monitoring was installed to aid in the design of the drainage system and water samples were collected to test for the presence of contaminants and iron.

An initial concept design was produced for the internal tunnel drainage only with a number of recommendations to the client to ensure a whole system approach to upgrading the drainage had been considered. In order to progress to detailed design, Vitruvius requested further surveys be undertaken of the external tunnel drainage to identify the asset condition, location and outfalls. This meant a full system design could be provided to prevent downstream defects causing an overflow of the tunnel drainage.

The detailed design offered two solutions for differing scenarios within the tunnel, the more complex of the two for higher flow rates comprised of a Megaflo system throughout the tunnel with a layer of drainage metal, a filter layer of sand and geofabric working in unison to increase the design life of the solution and a walkway that provided adequate underfoot conditions for maintenance. For increased efficiency within the tunnel a second option for lower flow rates was also proposed that allowed for the removal of the Megaflo and sand from areas of the tunnel where the flow rate was considered lower than 0.2l per s.

The design underwent review and requests were made by the construction team to amend certain aspects to allow for quicker install to match available work windows. Quick turnaround times for review and approvals of changes in the design have allowed for a solution that works in the tunnel environment and can be installed by the contractor in the allowable time. The value in having a strong design manager and having the contractor at the table for these discussions, with the client, was not lost in the lead up to commencement on site.

 

Civil & Laydowns:

On short notice, Vitruvius were brought in to act as Principals Project Manager and Rep to the newly awarded NZS:3915 contract to construct 3 laydowns as part of the enabling works with commencement deadlines looming and a handful of critical risks open that threatened that commencement. “Taking a proactive approach and understanding the right way through these risks was important to mitigating them within the short space of time available to do so”, Brad says. “Through the different stakeholder streams, legal and planning reviews and developing relationships for shared benefit across many of these risk areas, the critical laydowns were able to commence and complete with no disruption to the critical path drainage works”. Vitruvius are proud to help and navigate through such potential blockers with the vital support of the wider project team, “it couldn’t have been done without every person and part of the project acting towards our common goal”.

 

Project Director:

Neil Mason, with all of his available time (now he is not our Managing Director), was asked to step in as Project Director for the WRAPA Tunnels 1 & 2 delivery in August this year and support best practice long tunnel project delivery. Having now worked on all long tunnels in Aotearoa in some capacity, Neil brings a wealth of experience in safe / practical delivery of long tunnel work to support the WMUP team in achieving the programme of works in a complex safety and stakeholder project environment – “the kind of complex we thrive in”, says Neil.

Vitruvius initially began on the project in February 2023 with support and advisory requirements increasing over time. We have been grateful to join our valued client on this project delivery journey and bring not just our Rail knowledge, but our project delivery expertise as well in support of their project goals to safely deliver these critical works to programme. So far so good!”

Vitruvius would like to acknowledge all of the fantastic people that are involved in delivering this project and their companies – Our Client & Partner KiwiRail, consultants Tonkin & Taylor, WSP and Aurecon, Track & Drainage construction – Titan Contracting Group, Civil & Laydowns – Mills Albert, Tunnel Ventilation – BEST Engineering, and the vast network of sub-contractors and suppliers that make a project of this scale a success.