Green Square Stormwater Drain

Project Overview

UEA was contracted to add the relocation of a DN750 underground water main utility service, to allow for future bridge and road construction. Multiple installation methodologies were provided to our client as a package to meet installation requirements.


Huntley Street, Alexandria NSW


Saturated sand with high water table


DG Alliance & Sydney Water


100 linear metres




Conventional open cut excavation, GBM thrust boring

Scope of Works

UEA Pty Ltd was engaged to supply the materials necessary to undertake the below scope of works, along with the installation and commissioning of the main itself:

  • Complete a 60 metre underbore, installing a DN1050 mild steel carrier pipe on grade within water charged ground conditions
  • Temporary work designs certified for use onsite by appropriately qualified personnel
  • Protection of existing services where required
  • Excavation and disposal of all materials necessary to construct the works
  • Supply and install shoring in accordance with approved temporary work designs
  • Dewater all excavations using dewatering well points into a nominated onsite discharge point (via a sediment tank and flowmeter to treat prior to discharge)
  • Install the OD 813 SCL product pipe within carrier pipe, pump scour, outlet pipe and associated fittings
  • Centralise product pipe within the carrier pipe and grout into position
  • Supply and install bedding and backfill material as per specified requirements
  • Supply and install concrete thrust blocks
  • Connect to existing water main in accordance with Sydney Water shutdown protocols
  • Decommission of old redundant pipework
  • Restoration of site to council restoration requirements upon completion of works


The design was provided to UEA by the client via a third-party design team, and Sydney Water was intimately involved during the design and construct process. Any RFI’s or design changes encountered during construction were approved, installed and captured on WAC drawings. Any obstacles encountered onsite were worked through favourably in order to achieve suitable end goals. Through in-depth consultation with both the client and designer, UEA provided a PW bore beneath the existing Alexandria canal in a highly congested utility area, while also delivering an in-depth cutover during a 72-hour shutdown meeting all design requirements.

Technical Details

All construction complied with Sydney Water’s “WSA 03-2002-Water supply code of Australia_V2.3”, “WSA 03-2011 Water supply code of Australia_V3.1” and all other relevant WSAA, Australian and council standards deemed necessary.


  • Open cut trenching and microtunnelling of a loose sand geology, up to depths of seven metres deep in highly water charged grounds
  • Excavation of microtunnelling shafts and associated pipe installation trenches in a tight work zone, alongside continuous live traffic
  • Installation of a 90m PW thrust bore and rising connections parallel to the crown of Huntley Street, passing underneath a live stormwater canal and various other live utilities in the alignment of the PW relocation
  • Detailed and complex water main cutover procedure when connecting to a DN750 water main within a 72-hour shutdown timeframe
  • Scheduling our works within a fast paced, large scale infrastructure project with numerous work faces
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