Donnybrook Road East Branch Sewer Project

Abstract

The Donnybrook Road East Branch Sewer project (DREBS) is an integral piece of Yarra Valley Water’s infrastructure required to service the Northern Growth Corridor which include some of the fastest growing suburbs in Australia. The works comprise approximately 3.6km of pipework between 600mm and 750mm diameter at depths varying between 3m and 14m, the project connects development along Donnybrook Rd to the Amaroo Main Sewer. The tunnel alignment is constructed predominantly within private land which has sections that are within residential developments under construction. Given the depth of works and access restrictions within private land the predominant construction method selected for the project was to utilise trenchless technology. The project was separated into Separable Portions with separate contractors engaged to complete the works, this exposed the project to a range of trenchless techniques such as micro tunnelling (free boring and pipe jacking), and auger boring. These techniques were exposed to highly variable ground conditions ranging from soft clays to extremely high strength basalt. This paper will explore how each trenchless technique was utilised on the project, the challenges that were presented and how these challenges were overcome. Construction works commenced in February 2018 and are scheduled for completion in September 2019.