Flaxmill & Wanstead Roading Upgrade

Work continues with Russell Roads who are upgrading Porangahau Road between Flaxmill and Wanstead Bridges, Stage 2 and 3 sees the lift of the road by approx. 800mm.

Flaxmill / Wanstead Roading Upgrade – Stage 2

Work is underway on Stage 2 of the Flaxmill, where clearing works are underway, as well as installation of new culverts and drainage prior to milling and preparing to lift the section of road, Stage 2 and 3 see the road lifted by approx. 800mm to improve resilience and flooding risk.

Separable Portion 1 is now complete. This is the first of five sections in this project - keep an eye on our updates to follow the next sections in this programme of work. 

Works are progressing well with the road lift as part of Stage 1 just north of Flaxmill Bridge, the road has been milled back preparing to have the additional fill added in to lift the road in stages – progressing as planned and on track to be completed by the end of May.

The Flaxmill and Wanstead Road Upgrade project is also progressing well, with most of the clearing work done and the installation of a subsoil drain underway. This week the team at Russell Roads will be continuing to work on shoulder widening and the installation of a subsoil drain.

On March 29th, we held the blessing to commence the Flaxmill Roading Upgrade around Flaxmill bridge and north to Wanstead bridge. Our contractor Russell Roads is establishing onsite this week to lift the road as the first of five separable portions. The blessing was led by local hapu Ngati Kere, and was well attended by local landowners, CHBDC councillors, staff, our design team Stantec, our contractor Russell Roads and our funder the Provincial Development Unit. A pretty exciting moment in the programme to get our flagship project underway!

Hydraulic modelling identifies that Porangahau Rd has a <2year LOS, with the lowest levels being along a 1300m length adjacent to Wanstead Swamp wetland.

An engineering options assessment indicates that a 10 year LOS is achievable within the funding and timeframe constraints of the PGF, and a further lift to a 75 year LOS is considered feasible if a longer timeframe is available and funding outside the PGF is obtained.

Therefore, the preferred option strategy is:

• Online road raising: raise the road embankment level between Wanstead Bridge and Flaxmill Bridge to a 10 year LOS, with associated improvements to Flaxmill Bridge and Ugly Hill Corner culverts, using PGF funding and taking advantage of a scope of work that is online within the road reserve and likely to have a straightforward consenting process. The cost estimate for the works is $8.2M.
• Future online and offline works: begin planning (including consultation) for associated future online and offline works that would further raise the LOS to 75 years capacity for an additional budget cost of $3.3M. This offline work is mainly stream and channel widening through private land and provides improvement works to offset future projected climate change impacts.

You can read our report on the Flaxmill Inundation project here.