Scope of Works
Haberfield & Leichardt
Sydney Trains 11kV feeders 533A and 533B previously provided connection between Lewisham and Strathfield substations. These feeders cross Hawthorne Parade Canal in Haberfield over a footbridge, which was no longer safe for pedestrian use and has been replaced by an alternative bridge, approximately 130 metres north of the existing bridge. The objective was to relocate the 11kV feeders (533A and 533B) from the retired footbridge to the new Transport for NSW (TfNSW) footbridge, which was constructed with four spare conduits suitable for accommodating the feeders in anticipation of this project. UEA’s scope of works included the construction of two underbores required for this project (see below figure): an underbore at Barton Avenue, and an underbore at Darley Road under the Light Rail corridor.
Erskineville (Eveleigh Yard)
Sydney Trains constructed an 11kV cable route inside Eveleigh Yard for feeders 512 and 515. Part of this route involves an underline crossing (ULX) below seven tracks inside the maintenance yard. UEA’s team was tasked with the construction of the underbore required for this project. Working with the brief provided by the client, UEA undertook an additional topographical survey of the proposed route to develop a comprehensive underbore design for each section. This enabled the design in both plan and longitudinal cross-sectional views in MGA coordinates. Jemena was consulted due to the vicinity of the Secondary Gas Main (SGM) in Haberfield, and while working with the Jemena Gas Protection officers, the SGM was positively identified using Non-Destructive Digging techniques. Once located, a steel protection plate was installed in front of the SGM, in line with Jemena’s guidelines and UEA’s underboring methodology. Upon approval of the underbore designs, UEA completed surveying to mark and peg out each of the underbore alignments.
A Track Sediment Monitoring Program was required for two of three of the completed underbores. The underbore designs provided the data required to develop and implement the program, in which a number of monitoring targets are placed in key positions on and around the track along the underbore routes prior to the commencement of work. This allows a remote monitoring station to be set up nearby, in order to establish a baseline of data showing the preconstruction levels of the tracks and surrounding surfaces. The remote monitoring station was utilised to constantly record readings before, during and after the underboring works. As part of the Track Sediment Monitoring Program, UEA engaged a track protection officer to allow the team’s HDD operatives to track the underbore across live rail tracks safely. Works were completed predominately outside of a track possession, so trains were still active across the network.
Each site had limited access to site as well as a limited area to setup the HDD rig and associated equipment. As a result, the welding and stringing of the HDPE electrical conduits had to take place adjacent to the site itself. On completion of the conduit welding, UEA used custom-made spacers to form a bundle ready for pipe pull.
Due to the combination of soft clay and rock ground conditions for the first two underbores, UEA had the flexibility to use a second HDD rig and a variety of associated tooling. While working on the third underbore, fill ground conditions was encountered, which complicated the removal of material from the borehole during the reaming process. This include material such as ballast and unused track sleepers.
UEA used the team’s own pipe rollers and highly skilled HDD operatives to minimise the risk of pipe damage during pipe pull.
Taking into consideration the tight project schedule, UEA managed to successfully complete all three underbores while working through constant wet weather and changing ground conditions.