Gerringong Critical Main Renewal

Project Overview

As several towns in the south coast region of New South Wales were receiving potable water supplied through a single-source line experiencing sustainability issues, this project was required be undertaken by a highly skilled and efficient panel contractor. UEA was initially engaged by a major water authority for early contractor involvement via assistance in asset location, expert know-how on HDD installation and general water main constructive design advice. UEA’s unrivalled understanding of the scope was key in attaining the award of the project.

Location

Gerringong NSW

Geology

Client

Sydney Water Corporation

Length

800 metres

Pipe

250PE PN16, 500PE PN16 & 500PE PN20

Technique

HDD & open-cut

Scope of Works

The installation of the 800 metres of potable was installed using separate techniques:
  • Stage 1: 550 metres of 250PE PN16 temporary bypass, including two under pressure cut-in connections
  • Stage 2: 200 metres of 500PE PN20 drilled under railway line
  • Stage 3: 50 metres of 500PE PN16 installed via open-cut trench and connections
The initial temporary bypass design required an extension of approximately 170 metres, which eliminated the need for a major shutdown to these towns. The risk mitigation of this extension, recommended by UEA, was favourably looked upon by both the client and also by the local community, as the summer period was approaching.

Design

UEA was given a preliminary design by the client, and in consultation with the client’s designer, UEA helped develop key elements such as the temporary bypass and bore design.

Technical Details

The polyethylene pipe had different pressure ratings to suit the ground and pulling conditions in the project. All other fittings, structures and associated installations were constructed to their given technical drawings, and in particular to both water authority standards and project specific details.

Challenges

  • Client request to accelerate project by two months
  • Flow Isolation safety protocols
  • Track monitoring of the South Coast Railway Line through surveyors and geotechnical engineers
  • Management of ground water
  • UPCIC/hot tap connections on different pipe types
  • Installing complex fittings and assets
  • Weather challenges with heavy storm conditions
  • Existing assets had failure points in network
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