Grahamstown Water Treatment Plant Upgrades

NSW
Hunter Water
2020
4

sediment tanks replaced

75%

daily supply for region

4

hose-down connection points

3D

survey technology used

The Grahamstown Water Treatment Plant treats raw water to produce quality water suitable for drinking. As part of the Hunter Water Growth Plan, Abergeldie was engaged by Hunter Water to upgrade the sediment tank. Delivered under brownfield conditions, Abergeldie ensured that the tank remained available for the benefit of the many people it services throughout the works.

Scope of works

The scope of work included:

  • Replacement of the sludge removal system in the four sedimentation tanks and associated mechanical, electrical and communication works Removal and disposal of the existing travelling bridge sludge scraper system including remediation of cast-in items.
  • Assembly and installation of the MRI hoseless Cable-Vac sludge collector system (two per sedimentation tank), including electrical control panels.
  • Supply and installation of electrical and communication cables.
  • Design, supply and installation of rake guide rails.
  • Installation of a common sludge outlet pipe per sedimentation tank with a mass flow meter.
  • Extension of the service water system to four new hose-down connection points.
  • Automation development, integration, and commissioning.

Remedial works in the sedimentation and flocculation tanks and appurtenances included: 

  • Survey (including 3D point cloud) to identify all concrete delamination and cracking areas.
  • Break-out, removal and repair of all delaminated concrete.
  • Removal of existing asbestos-containing joint sealant where required, and reinstatement with a new joint sealant.
  • Application of epoxy waterproof lining within tanks and on tops of tank walls.
  • Repairs to major cracks and failed joints in the walls of the sedimentation and flocculation tanks, and injection of sealant into other concrete cracks of 0.15 mm or greater width.
  • Replacement of non-compliant accessways.
  • Replacement of the manually operated flocculation tank inlet penstocks with new stainless-steel penstocks, stop boards and stop board guides.
  • Replacement of damaged or broken timber paddles on flocculation chamber paddle wheels and broken fixed steel baffles (stators).

Brownfield conditions and asbestos mitigation measures

Works were carried out under brownfield conditions and staged to enable the existing plant to continue operation. 

Particular care was taken during the removal of existing process components, piping materials, structural elements, and repairs to waterproof joints, as the old sealant material was known to contain asbestos. 

As a separable portion, dowels at the footing of the tank floor slab joints were exposed by hydroblasting at three sample locations to enable detailed inspection. This was done in consultation with Hunter Water to determine the extent and nature of the repairs required and to agree on the most appropriate remediation methodology and cost.


Sustaining crucial water resources 

The Grahamstown Wastewater Treatment Plant upgrade was integral to Hunter Water's Growth Plan, which aimed to bolster the region's position as the leading regional economy in Australia by 2036. Serving a population approaching 600,000 people in homes and businesses across the Lower Hunter, Hunter Water provides essential services including drinking water, wastewater treatment, recycled water, and some stormwater management. The upgrade ensures the sustained operation and efficiency of the Grahamstown Water Treatment Plant, which holds the capacity to treat water from Grahamstown Dam and/or Tomago Sandbeds, with a peak supply capacity of 257 megalitres per day, thus securing vital water resources for the community's needs.