Sewer Surcharge Package 9B



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Project Details

This project, referred to as 9B, formed part of a Sydney Water package to upgrade sewerage infrastructure in the south Sydney region. The project was run by Monadelphous Engineering (ASX:MND).

Scope of Works

UEA’s Civil Construction team was tasked with providing a turnkey package to Monadelphous for the management and installation of additional gravity sewer main works for the Sydney Water surcharge program. The works consisted of 90 lineal metres of thrust boring and 65 lineal metres of open cut excavation, and ground conditions included Sydney sand, sandstone and clay, as well as groundwater up to depths of five metres. Works also required the installation of maintenance holes ranging in a few sizes, from DN1050 and DN1200, up to DN1800 (lined). The pipe specification was DN225 & DN300 uPVC SCJ DWV pipe, with three of the five maintenance hole structures constructed over an existing sewer asset. The design was provided by ENSure (GHD) for Sydney Water and Monadelphous.

Technical Details

All construction complied with Sydney Water’s “WSA 02-2002-Sewerage Code of Australia_V4.0 and “Deem-To-Comply” drawings, as well as with Sydney Water’s “Civil Technical Specification v7”.

Challenges

  • Groundwater encountered at close to 5.0 metres in depth in the region of DN1800 MH. The client supplied a de-watering system and maintained by UEA to enable safe works.
  • An existing sewer pipe required a bypass setup to enable the installation of DN1800 (lined) MH. Existing sewer line within MH was removed due to its size, shape and specification (450mm oviform nil-RRJ)
  • An area of high environmental importance with a nearby waterway and a small park. UEA minimised the amount of material left on the surface and incorporated the use of large bins for material storage.
  • Higher than average flow conditions during connection, while making the sewer main “live”.
  • Medium to high trafficable road (Roach Street). This included management of access and driveways for residents nearby (Mount Street) as the area is fairly populated.
  • House service lines for various utilities (gas, water and sewer) were encountered in unfavourable locations. UEA co-ordinated these relocations to ensure works proceeded with minimal delay.