Epping Main Sewer Pipejack: Challenges and Resolutions

Abstract

This paper will discuss a new installation of sewer pipeline utilising Microtunnelling/pipe jacking technique. The Epping Main Sewer project comprises 2.3km of 1600mm and 1800mm internal diameter sewer at depths ranging from 15m up to 42m. Five manholes will be installed after the completion of the tunnel drives. The alignment connects the Epping Branch Sewer to the Merri Creek Main Sewer, and services the Northern Growth Corridor removing the need for existing temporary pump stations and allowing for the future growth of Melbourne’s Northern Suburbs. The tunnel alignment crosses under the Hume Freeway and Merri Creek, before crossing near the Merri Creek to connect to the Merri Creek Main Sewer at the downstream end. The alignment predominantly passes through public open space, including the Barry Road Grassland and Whittlesea Gardens, with some sections traversing privately owned land. The pipejacking/microtunnelling works comprises of 4 straight drives, 400m, 570m, 610m and 730m in length. Each tunnel drive faces unique challenges on this project including tunnelling through high strength Basalt formation; mixed geology of Melbourne Formation, Paleo Clay and Basalt; creek crossing with shallow overburden and launching and jacking from a 40m shaft. Careful planning and risk assessment were carried out prior the tunnelling activities, in turn mitigation measures and an innovative solution were put in place to tackle these challenges. John Holland was able to complete all 4 tunnel drives with great success and without any major safety incidents. This paper will provide an overview of this project and focus on the microtunnelling/pipejacking aspect of the project. Page 1 of 11 No-Dig Down Under 2019 Epping Main Sewer Pipejack: Challenges and Resolutions Jiang Aizezi and Ashley Hamer 1. PROJECT OVERVIEW 1.1 Project Background and Scope Following several extensions of the Urban Growth Boundary (UGB) by the Government, Melbourne’s Northern Growth Area (NGA) is expected to accommodate an additional 128,000 properties by 2040. This growth necessitates a significant increase in downstream sewerage system capacity to transfer flows to the metropolitan system and reduce the risk of spilling to the environment. In 2008 Yarra Valley Water (YVW) developed the Epping Craigieburn Sewerage Strategy to provide the capacity to service growth. This strategy included the construction of the Epping Main Sewer, a 2.4km sewer which links the Epping sewage catchment to the Merri Creek Main Sewer (refer Figure 1 for a locality plan), providing the required capacity for growth in the north. The strategy also identified temporary arrangements involving two temporary pump stations to divert flows to alternate catchments, allowing the construction of the Epping Main Sewer to be deferred by eight years. This interim servicing strategy is approaching capacity and the Epping Main Sewer is required by 2020. Existing Sewer Epping Main Sewer Tunnel Alignment Figure 1 - Locality Plan A workshop was held to identify the most appropriate delivery model for the project. A design and construct delivery model were preferred as it allows contractors to identify the most efficient construction methodology and depth for the sewer, this was especially significant given the depth and differing ground conditions. In June 2017 the Epping Main Sewer Project was awarded to John Holland as a Design and Construct Contract to be completed by Mid-2019. The Epping Main Sewer project comprises 2.3km of 1603mm and 1850mm internal diameter sewer at depths ranging from 15m up to 42m. Five manholes will be installed after the completion of the tunnel drives. The alignment connects the Epping Branch Sewer to the Merri Creek Main Sewer, and services the Northern Growth Corridor removing the need for existing temporary pump stations and allowing for the future growth of Melbourne’s Northern Suburbs. The tunnel alignment crosses under the Hume Freeway and Merri Creek, before crossing near the Merri Creek to connect to the Merri Creek Main Sewer at the downstream end. The alignment predominantly passes through public open space, including the Barry Road Grassland and Whittlesea Gardens, with some sections traversing privately owned land. Page 2 of 11 No-Dig Down Under 2019 Epping Main Sewer Pipejack: Challenges and Resolutions Jiang Aizezi and Ashley Hamer