A major pump upgrade to the City of Logan’s largest wastewater pump station, involving 3D laser surveying and the reuse of existing pump station components, has won an industry award for its innovative design and cost-savings measures.
The Alfred Street Pump Station, located at Slacks Creek in Logan City, has operated since 1984, taking wastewater from properties to the Loganholme Wastewater Treatment Plant for processing. A $7.7 million project to upgrade the pump station and reduce the risk of wastewater overflows was completed by the Logan Water Infrastructure Alliance – a public and private sector enterprise comprising Logan City Council, Downer, Cardno, and WSP | Parsons Brinckerhoff.
The success of the upgrade was recognised when the project won the 2016 Institute of Public Works Engineering Australasia Queensland (IPWEAQ) Excellence Award in the water, wastewater and drought management category.
Principal Water Engineer Anthony Domanti led the design of project over several years and said that correctly selecting the new dry-mounted pumps was an important element during the design development of the project.
“The new pumps selected for the project were KSB Amarex KRT-K, 500kW (dry-mounted) pumps with a single duty point of 1,175 L/s at 35m,” Mr Domanti said.
Mr Domanti said these pumps were selected based on certain criteria, including the ability to use the existing overhead bridge crane, and the ability to pump to separate discharge points.
“Upgrading the existing overhead crane at the pump station would be expensive and probably require the existing building roof to be raised, further adding to costs.
“Originally the Alfred Street Pump Station site was connected to a set of rising mains before discharging to the Loganholme Wastewater Treatment Plant. However, following a master planning review of the Logan North wastewater catchment, a new $50 million rising main (7km x DN1200) was constructed on a different alignment,” Mr Domanti said.
The new rising main is usually operated by SPS69 (one of two pump stations on site at Alfred Street complex), but the new pumps installed at SPS02 (the other pump station on site which was substantially upgraded) had to be able to operate effectively via this new conveyance direction.
The original pumps that were replaced were Thompsons, Kelly & Lewis 600/700 VS wastewater pumps.
These were driven via a line shaft from two speed motors mounted at the mezzanine level.
Reduce, reuse, re-purpose
The Logan Water Infrastructure Alliance (LoganWIA) decided to reuse existing pump station components in the project, saving $1 million. Mr Domanti said the aim of this was to ensure value for money and reduce the impacts of major construction.
“LoganWIA adopted an asset management strategy to extend the operational life of the Alfred Street Pump Station. During detailed planning and design of the upgrade, the team identified several opportunities to re-purpose existing pump station components,” Mr Domanti said.
These opportunities included reusing the existing electricity supply including site transformers, substation compound and standby generator; maintenance of the existing bridge crane; the optimisation of existing buildings; and avoiding significant modifications to the pump station roof and overhead crane system (influencing pump selection). The project also avoided the construction of a new electrical control building by reusing an existing structure.
Other aspects of the pump station were also upgraded, including a new switchboard room which was built utilising existing space within the SPS02 building.
“This offered a significant reduction in new cable supply compared to providing a new structure elsewhere on site,” Mr Domanti said.
This also allowed the provision of current industry-standard facilities. Operations and maintenance personnel are no longer exposed to a potential arcing fault hazard and the asset now operates reliably.
“All mains cables were routed outside the building to avoid cable penetrations between the machinery hall and the new control room, which further minimised the risk of corrosive gas affecting the electrical system,” Mr Domanti said.
Utilising 3D surveying
Mr Domanti said a key construction challenge during the project involved the safe removal of the existing steel framework system. A construction hazard assessment (HAZCON) was undertaken, which addressed the construction risks and sequencing of works. Following the HAZCON, the existing steel framework system was able to be removed by using a knuckle boom spider elevated work platform (EWP).
“The key features of the machine were its small footprint, it reaches 15m in height, and the turret, which rotates 359 degrees, thereby achieving full access to the upper section of the dry well,” Mr Domanti said.
In the end, the implementation of the EWP was five times cheaper than using conventional scaffolding.
Due to the limited as-constructed information available, 3D laser surveying was used to design the new pump arrangements, and understand potential operational issues and prevent them from occurring.
“Use of this technology for brownfield sites is more cost-effective than manual measurement processes which are error prone and require a greater length of time to complete,” Mr Domanti said.
The reliable 3D survey was used for all aspects of design development, such as confirming the exact pipework lengths, obtaining difficult-to-reach measurements and ensuring safety in design obligations were met.
“It was also used extensively to develop a safe demolition sequence associated with removing the pump line shaft framework system, and associated platforms,” Mr Domanti said.
What can other contractors learn?
Mr Domanti said the innovative design and construction methods and the challenges of this project taught him several lessons that he now shares with young engineers and other project teams.
The top six things he took away from the Alfred Street Pump Station upgrade include:
- 3D laser surveying is an effective tool that enables designers, constructors and operators to better understand and eliminate safety risks
- Overseas-produced fittings may be incorrectly labelled as being in accordance with Australian standards and need to be checked for this reason
- Allow for as much pipework connection flexibility as possible to accommodate for potential misalignments
- Recognise that tolerances are a part of the manufacturing process and their impacts must be considered during the design phase
- It is beneficial when the pump supplier replicates (as close as possible) site conditions when performing factory acceptance tests
- Suction specific speed is a key parameter for selecting high flow pumps
Mr Domanti said the upgrade was a career-defining project for him, as well as those involved from Logan City Council, Downer, WSP | Parsons Brinckerhoff, and Cardno.
“It is appreciated when your team receives an industry award. It’s like a ‘thank you’ for all the effort, long hours and innovation that goes with meeting the challenges of a project like this.”