Adjusting the Donvale Branch Sewer Design to Achieve a Successful 470m Long HDD Bore

Abstract

Donvale is an established suburb on Melbourne's north-eastern urban fringe and when the area developed in the 1950’s, the undulating topography and high cost to construct sewers meant that 1,200 properties were not sewered. By late 2017, Yarra Valley Water were two years into the project to construct the 4km long Donvale Branch Sewer; the backbone of a much wider project to take these properties off aging septic tank systems and onto a sustainable sewerage solution. Micro-tunneling methods were being used to construct the sewer, but challenging ground conditions experienced during construction, combined with an even more challenging section of the project still to be built, caused Yarra Valley Water to rethink its approach and relocate a 470m long section of the design out of customers’ properties and into the nearby road reserve. This paper explores how experiences gained from nearby challenging ground conditions were used to adjust the sewer design and how this decision greatly reduced the impact of the project to private properties by paving the way for this section to be constructed using horizontal directional drilling in one continuous bore. This section of the 400mm diameter sewer was constructed in 2018 by AHD Trenchless and MFJ Constructions.

Techniques