Lauderdale Sewerage Scheme Project feasibility
What is the Lauderdale Sewerage Scheme?
The challenge of addressing the issue of the wastewater (sewerage) management for the 2,400 residents of Lauderdale on Hobart’s Eastern Shore has now passed from the Clarence City Council (CCC) to Southern Water. The existing sewerage infrastructure for Lauderdale dwellings comprises onsite effluent disposal methods (predominately septic tanks and soakage trenches). These present potential health issues and constraints on future development.
To address these issues, CCC started construction of the Lauderdale scheme to provide residents of Lauderdale with a new reticulated, wastewater system and this was intended to be constructed in a number of stages over a number of years. The first stage began in early 2009 and focused on developing the backbone of the system, consisting of a major pump station, two minor pump stations, a pipeline and some minor associated works. Southern Water took over responsibility for the scheme on 1 July 2009 and we have now completed work on stage 1.
Stage 2 - pressure sewer system
The traditional method for sewering an area is to construct a gravity sewerage system. This consists of pipes which follow the lay of the land with the collected wastewater flowing by gravity towards a main pumping station before it is pumped to a wastewater treatment plant (WWTP). Lauderdale however, with its low lying position close to the water’s edge, would not successfully support such a solution. With relatively flat gradients there is an increased risk of sedimentation and subsequent blockages in a gravity system.
For stage 2 of the scheme Southern Water’s solution to the challenge is a pressure sewer system. Pressure sewerage technology is a recent arrival to Australia having only had installations of it occurring over the last 5 -10 years. However the technology has been in existence around the world effectively since 1972. In Australia it has enjoyed success in servicing those existing areas that have previously been deemed to be either too costly or too technically difficult to service using conventional sewerage technology. Typically this has been where development has occurred in areas that are extremely flat, where there is significant distance between properties, where there is a high water table, where the area is subject to flooding or where there is a high rock content.
This pressure arrangement consists of a common collection system of fully sealed pipes, explains project manager Lis Chaffey. “These are fed by small pressure sewer units (PSU) located at each connected property.
“Household wastewater is delivered to the small pumping station unit located on the property, where it is then pumped under low pressure to the collection mains located in the street via a small pipeline in the property. The collection main will transfer wastewater to the Lauderdale pumping station which was constructed during Stage 1 of the project. From here the waste will be pumped to the Rokeby WWTP,” Lis says.
The new sewerage system will play an integral role in ensuring the health and wellbeing of the Lauderdale community, eliminating amongst other things, dirty water seepage and ongoing property dampness.
March 2012
Southern Water is aware of the Tasmanian Coastal Adaptation Decision Pathways (TCAP) investigations being conducted by Clarence City Council, in relation to climate change, flooding and sea level rise affecting Lauderdale.
These inundation concerns are just one of the factors behind Southern Water’s conclusion that a pressure sewer system is the most suitable solution for the area.
Existing on-site systems may not operate adequately in times of storms or flooding. Therefore the pressure sewer system, the design of which will consider inundation in the area, and provides an alternative solution to affected properties.
We do not expect the Lauderdale Sewerage Scheme to be impacted by the outcomes of the Clarence City Council community consultation process associated with the TCAP.
April 2012
Southern Water has appointed the Designer & Supplier to take the Lauderdale sewerage scheme forward.
If you would like to be contacted direct please email us at lauderdale@southernwatertas.com.au