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Airport opts for underground construction

Sydney Airport is upgrading its Northern Pond Apron Bays 83, 84 and 85 from layover positions to serviced active bays, which will be capable of bussed arrivals and departures.  

To support the operations of active bays, the current infrastructure in these locations required an upgrade for refuelling capabilities, aircraft ground power and preconditioned air.  

To facilitate this refuelling ability, an existing 450 NB fuel feed feedline was extended from its existing termination point to a new junction pit at Bay 83, and Rob Carr was contracted to complete these complex installation works.  

A trenchless solution  

Rob Carr Construction Manager Andrew Scarr said the project included constructing a 523 m long DN900 reinforced concrete jacking pipeline using slurry pressure balanced microtunnelling to install it in three separate drives.  

These drives were carried out predominately through saturated ground conditions consisting of silt, sand and fill.  

To complete the tunnelling and allow for the installation of the 450 NB fuel pipeline within the DN900 concrete pipe, Rob Carr also constructed in situ concrete caissons.  

“The project also included the construction of two 9 m ID caissons and two 4 m ID caissons, which provided a dry and safe working environment for the tunnelling crews to conduct operations,” said Mr Scarr.  

“Caissons were also chosen to minimise dewatering”.  

Mr Scarr said the construction of the second 4 m ID caisson was challenging due to its location, being adjacent to the runway, which required all plant and equipment within the obstacle limitation service; however, at this location it was only 1.4 m above ground level.  

To overcome this challenge, Rob Carr locally lowered the ground level, reduced lift/pour heights on the caisson and only worked while the runway was closed from 11pm-5am and mobilising and demobilising required plant and equipment for each shift.  

Additionally, Mr Scarr said some challenging drilling conditions were encountered with large amounts of foreign material being encountered on the second line.  

“This was able to be dealt with due to the correct selection of microtunnel boring machines (MTBMs), a highly experienced MTBM operator and the perseverance of the MTBM crew enabling the line to be finally completed on line and level.”  

Mr Scarr adds that Rob Carr was also responsible for the management and treatment onsite of assets, the management and disposal of drilling water and the establishment of compounds. 

Working alongside Mr Scarr was Rob Carr Operations Manager Justin Croucamp, with the two men responsible for overseeing the overall construction program and management of the works.  

Additionally, Mr Scarr and Mr Croucamp provided support to both the project’s Project Engineer and Supervisor, being Jamie Leal and Damian Coward respectively.  

“Though the conditions were quite challenging, the project was completed successfully and well ahead of the contract schedule.”  

For more information visit the Rob Carr website. 

This article was featured in the March 2021 edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet or mobile device, click here.

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