Western Trunk Sewerage Scheme (Oakey to Wetalla WRF)

The Oakey wastewater treatment plant was constructed over 60 years ago and has undergone minimal improvements since then.  Located on a flood plain, the plant is susceptible to flood inundation with consequent damage and release of sewage to the environment.  Furthermore, the plant is at capacity with difficulty meeting EPA licence discharge conditions.

The plant sustained major flood damage during the heavy rainfall of 10 and 11 January 2011.  Council subsequently considered options for the future management of Oakey wastewater flows and decided that the pumping of sewage to the Wetalla WRF would be the best option.

It was chosen because of the following advantages:

• Avoids the costly (circa $21 million) augmentation of the current Oakey treatment plant and sourcing suitable land for both the new plant and effluent reuse areas
• Better caters for future growth of Oakey
• Disposal of Oakey effluent through the Wetalla WRF licence and third party effluent reusers
• Assists in carbon loading to the Wetalla WRF which will improve the operation of this plant
• Lower operating and maintenance costs, and
• Greater flexibility in the operation of the proposed Kingsthorpe/Gowrie Junction sewerage schemes.

 The Western Trunk Sewerage Scheme comprises four major sewage pumping stations (SPS) and over 29 km of pipelines with the following elements:

• Diversion of three pressure mains in Oakey township to a major new sewage pump station (approx 3,800 metres)
• A major new Oakey sewage pumping station at council's Lorrimer Street Depot
• Construction of a pipeline from the Oakey SPS to the Kingsthorpe SPS approx 11.4 km long (DN 300mm pressure pipe and DN 450 mm gravity main pipe)
• A major new Kingsthorpe sewage pumping station on Gowrie Street (opposite East Street Road) that will also take sewage from the proposed Kingsthorpe sewerage scheme
• Construction of a pipeline from the Kingsthorpe SPS to the Gowrie Junction SPS approx 7.6 km long (DN 375mm pressure pipe)
• A major new (Gowrie Junction) sewage pumping station on Old Homebush Road (near Gowrie Creek crossing) that will also take sewage from the proposed Gowrie Junction sewerage scheme
• Construction of a pipeline from the Gowrie Junction SPS to the Kooringa Valley SPS approx 3.4 km long (DN 375mm pressure pipe and DN 600 mm gravity main pipe)
• A major new (Kooringa Valley) sewage pumping station off Hermitage Road  (between Boundary and Nugent Pinch roads) that will also take sewage from the Kooringa Valley subdivision and

Construction of a pipeline from the Kooringa Valley SPS to the Wetalla WRF approx 3.2 km long (DN 450 mm pressure pipe and DN 750 mm gravity main pipe).

Upon commissioning of the scheme, the Oakey wastewater treatment plant will be decommissioned.

Sizing of the sewage pumping stations and pipelines will provide for medium-term growth in the areas serviced by the scheme with potential for other nearby areas to be connected.