Primary Sedimentation Tank 8 Rehabilitation - Aqua Metro Pty Ltd
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Primary Sedimentation Tank 8 Rehabilitation

Primary Sedimentation Tank 8 Rehabilitation

Small Scale Capital Program


Melbourne Water


Western Treatment Plant

Key Sector

Water and Sewer

Contract Type



9 Months
October 2019 to July 2020

Key Facts

  • The Primary Sedimentation Tanks (PST) at the Eastern Treatment Plant (ETP) have been in continuous operation since commissioning in 1975.
  • Primary Sedimentation tanks are used in the primary treatment stages of sewerage treatment process.
  • During routine maintenance of PST8 significant cracking was observed in and around various concrete structures.
  • The main structural components of the tank Include: reinforced concrete (RC) floor and walls, square RC columns, walkway beams, and tie beams.


Rehabilitation of Columns and other structures needed to take place in a safe manner with limited disruption to the operations of PST8 and adjoining facilities. Purpose of the Rehabilitation work was to mitigate the risk of asset collapse within the PST area.

Scope of Service

The scope of work comprised of the following:

  • Emptying and cleaning of PST8.
  • Undertake appropriate NDT scanning to identify any hidden services.
  • Design and fabricate any temporary structures/platforms required to carry out the works.
  • Design of a long-term solution to rehabilitate the column.
  • Carry out rehabilitation works on column S21.
  • Replace sealant in the gullwing expansion joints.
  • Design, fabricate and install stainless steel brackets at the primary beams to increase the design life of the roof structure.
  • Remediate spalled and cracked concrete.
  • Apply a protective coating to the underside of the roof structure.
  • Remove the failing waterproof membrane and install a new waterproof membrane.
  • Rehabilitate existing drain port entries at the roof level and provide additional rainwater relief points.
  • Provide reports on the remediation works.


  • Working from heights were managed through innovating a rolling platform on the roof, thereby eliminating live edges while giving full access to site crew for coating application.


  • Works were carried out with controls in place to ensure no hazardous liquid could not enter stormwater system on site.

Stakeholder Engagement

  • All works were carried out in coordination with Operations team at Eastern Treatment Plant and Major Capital Delivery team.