Hawkins Infrastructure is midway through completing the $16.5m realignment of SH2 at Muldoon's Corner in the Rimutaka Ranges; the sharpest and tightest corner on the hill road. The project aim is to improve safety by easing a number of tight curves, including Muldoon's Corner, through improved visibility and protection from the drop into the valley.

The project involves the construction and widening of the existing roadway, including installation of large waterway culverts, and mitigation and re-vegetation of the native plant species. It is expected that by the end of the project a total 230,000m³ of earthworks will have been completed along the one kilometre road length.

The extensive earthworks are being undertaken in a difficult environment from very high, steep hills to very deep, steep gullies. The highest cut on the project is at 55m above the road, meaning great care has been placed on the safety of operations to ensure public and road safety at all times and to ensure that the road is able to function effectively, as it is a critical lifeline between the Wairarapa and Wellington, providing access to regional facilities such as the port, airport and hospital. Traffic management has been an integral part of site safety. Large construction trucks and vehicles have to cross the state highway to access the cut and fill sites.

Environmental management on this project has been a key issue. Hawkins cannot carry out any earthworks on the project that would affect these streams between 1 May and 31 August each year, so as not to disturb the fish spawning during that period. The project site is prone to large volumes of rainfall and, as such, great lengths have been taken to protect the surrounding streams from sediment and mud that runs off the work site, including the establishment of holding ponds to allow sediment to settle and the clean water to then flow into the storm water drains.

Large concrete culverts have been installed to carry water under the new road and down to the bottom of the gullies. Each culvert is buried within compacted fill and will join into an energy dissipation unit. This is a large concrete chamber 3.3m high, 5.6m long, and 4.5m wide, which will reduce the speed of the water flow before eventually running into the stream at the bottom of the gully.

There are many fish species within the Rimutaka Hill streams and, in order to make sure the culvert allows the migration of fish between the valley floor, watercourses and streams further up the hill, small ledges have been set along the lower half of the precast concrete pipes forming the culvert.

As part of the contract, extensive work is involved in the mitigation and re-vegetation of native plant species. Important specimens have been identified and will be protected on site or relocated temporarily during the construction phase. Other key tasks for the landscape works include:

• Collection & transplantation of existing seedlings & native plant debris
• Tree surgery/arboriculture
• Supply and installation of 30ha of native plant species
• Hydroseeding with grass and native seeds
• Supply and installation of composted mulch (28,000m2)
• Vegetation control and protection from noxious weeds