Introduction

The Rangiriri Bypass is recognised as a Road of National Significance (RONS). The project included 4.9km of greenfield construction which provided a new four lane highway with grade separated diamond interchanges.

Project Scope

The Rangiriri Section is part of the Waikato Expressway that included greenfields construction of a 4.9 km long four- lane divided carriageway to expressway standard with two grade separated diamond interchanges. Approximately 5 km of local road network was also realigned to optimise connectivity with the expressway. A feature of the project was extensive wetland development in sympathy with the surrounding environment and consistent with local iwi expectations.

Project Challenge

The expressway passes through the historic Rangiriri Pa and battle site and much of the length is located on highly compressible and potentially liquefiable soils, presenting significant challenges to the design team. A feature of the project was extensive wetland development in sympathy with the surrounding environment and consistent with local iwi expectations. Rangiriri is also subject to flooding and has been designed to withstand a 1:100 flood while being flexible enough for part of the formation to act as a spillway for one off spillway events (WRC approved release valve for the Waikato River)

Project Solution / Result

An extensive wetland treatment has been developed that aligns with the area’s natural ecology. The Rangiriri area has significant historical and cultural importance to Waikato Tainui and other iwi. MWH prepared an archaeological report, ecological report, cultural and historical impact assessment report and were involved in formulating a mitigation strategy. MWH also developed and implemented an iwi consultation strategy that was so successful that it has subsequently been adopted on other Waikato Expressway projects.