BEGINNING WITH THE END IN MIND: OPERATOR CENTRIC SPS RENEWALS

Laurence Marano, Associate Civil Engineer, Logan Water Partnership (WSP) Regan Ridgway, Senior Civil Engineer, Logan Water Partnership (WSP)

Introduction
Renewals projects are commonly viewed as necessary for one of two reasons: the need to replace infrastructure at the end of its design life, or the need to upgrade assets to meet increased capacity demands. However, renewal projects also present a valuable opportunity to reassess site conditions and incorporate improvements in safety, operability, and accessibility. 

A future-ready asset begins with a clear understanding of its intended function. Therefore, beginning with the end in mind is key to any asset improvement we do. Designers must go beyond simply applying standards - they need to consider how the asset will perform under real-world conditions, particularly during extreme events. Building resilience into the design is essential to ensure long-term functionality and reliability.

Managing growth and renewals
The City of Logan is experiencing rapid growth, with greenfield expansion and brownfield redevelopment placing increasing pressure on Logan Water’s existing infrastructure. Much of the brownfield network, built during Australia’s post-war boom (1960s–1980s), is now approaching the end of its design life. This convergence of ageing assets and new development demands has created what’s often referred to as the ‘infrastructure cliff’. 

To continue delivering reliable water and wastewater services, while funding new infrastructure, Logan Water needed to rethink its approach to renewals. Enter the Logan Water Partnership—a collaboration between Logan Water, Downer, WSP, and Stantec—established to deliver future-ready infrastructure that is aligned with the city’s sustained growth. Now celebrating 15 years, the partnership has evolved to deliver not only technical excellence, but also broader community and operational benefits

An operator-centric philosophy
Logan Water’s partnership model spans the entire asset lifecycle, fostering collaboration across disciplines that traditionally operate in silos. One of its most valuable outcomes has been bridging the gap between textbook design and operational practicality. 

Asset engineers and designers, working closely with the Logan Water operations and maintenance personnel, have ensured the root cause of a problem is understood and addressed, not just the effect or symptom. This engagement ensures design efforts are targeted where they matter most, supporting routine and reactive maintenance. The insights of operators allow for smart and safer solutions that directly addresses concerns of the end user.

Operator-centric case study
The Spanns Road Sewage Pump Station (SPS) is a terminal facility that was (initially) within the Beenleigh wastewater catchment, conveying flows directly to the Beenleigh Wastewater Treatment Plant (WWTP). This SPS is a 14.2m deep, 9.5m diameter wet well, with an ultimate capacity of 380L/s, which was constructed in 2007 (refer to Figure 1). 

Due to capacity constraints at the Beenleigh WWTP, a new transfer strategy was developed to redirect flows from the Spanns Road SPS to the Loganholme WWTP - supporting a more centralised treatment approach for much of Logan’s sewerage catchment. 

A renewals-based study was undertaken to identify the upgrades required to enable this redirection. The design process was shaped by close collaboration with operational staff, ensuring the solution addressed real-world challenges. This partnership approach enabled the integration of operator-focused enhancements, delivering practical, safe, and efficient outcomes.

Operational Resilience
Inlet hydraulics:
The previous inlet structure was designed with an encased dropper pipe, leading to a central hollow column, which discharged the flow out each side in a direction parallel to the pump line (refer to Figure 2). This arrangement did not promote a smooth flow profile to the cycling duty pump, which increased the chance of air entrainment, poor performance and blockages. These risks were all exacerbated as it is a terminal Figure 4: Cover upgrades. pump station receiving a high level of grit and rags. 

To address these issues, the inlet was redesigned with a dropper pipe that delivers flow axially to the pumps, allowing for the integration of a knife gate valve within the wet well. 

Computational Fluid Dynamics (CFD) modelling and a review of operating levels were used to optimise the design and mitigate risks commonly associated with drop structures, such as odour generation.

Flow balancing:
As a function of the flow diversion, with multiple pumps now pumping to a common inlet at the WWTP, a single flowmeter at the discharge point was no longer feasible. The previous methodology involved cross checking the existing flowmeter at the discharge end against the wet well levels and pump operation in SCADA – this introduces unnecessary risks. As a result, a new flowmeter was installed at the pump station, providing the ability for instantaneous flow balancing and flow pacing to optimise system wide pumping

Bypassing and Isolation:
The existing pump station setup had an emergency bypass connection point; however, it required confined space entry inside the valve chamber for operation and connection. It also warranted a significant length of pipework, as it was not near the nominated bypass pump setup position. 

Contingency planning was undertaken to develop a preferred bypass strategy. As a result, the proposed solution was to cut in a new bypass connection to the rising main downstream of the valve chamber, with a buried bypass line back to where the bypass pumps would be set up. The new bypass connection point provided safe access for operators at ground level and removed any requirement for confined space entry when bypassing was occurring.

Maintainability and Accessibility
Flood levels:
To address climate-related risks, flood modelling was updated and contingency scenarios were workshopped to guide infrastructure placement and redundancy measures. Fortunately, the wet well’s top slab sits above the 1% Annual Exceedance Probability (AEP) level, providing inherent flood resilience. The switchboard location was revised, and a termination box was added adjacent to the wet well to manage pump cables more safely. This simple addition significantly reduces manual handling risks during pump removal.

Emergency overflow relief:
Historically, the emergency overflow screening structure for this catchment was located within a Queensland Rail corridor, limiting access during critical events. To eliminate this operational risk, a new screening device, with dedicated access, was integrated into the pump station design. Traditional static screens require manual cleaning post-event, which is labour-intensive and unpleasant. 

To improve safety and efficiency, a self - cleansing screening device - the WATSOL Sewer Comb, supplied from Drapper Environmental Consultants (refer to Figure 3), was installed in a nearby upstream maintenance hole. This system uses static combs and a hydrostatically actuated ball valve to capture solids during overflow events. Once flows subside, the retained material is conveyed back to the WWTP inlet screens, reducing operator workload and environmental impact.

Lifting:
The existing monorail crane was at the end of it’s design life, and did not have the lifting capacity to cater for the new ultimate sized pumps. Rather than a like for like replacement, a new jib crane was installed for increased functionality.

Access covers:
The original access cover setup relied on rope netting as fall from heights risk mitigation. This was a significant deficiency which was addressed with modernised replacements (refer to Figure 4). 

The existing covers, and the opening of the wet well and chambers, were designed to cater for a four-pump solution. Following a review of the future hydraulic requirements, two pumps were adequate in a duty/standby configuration, meaning the openings were effectively oversized. Logan Water worked with a local supplier, Mass Products, to develop a tailored solution to minimise the size of the opening, using fixed panels to minimise the size of the hinged opening to reduce manual handling and fall from heights risk exposure. Pump cable hooks were also relocated to the suitably designed frame, based on operator pump lifting procedures

Operator and public safety:
The Spanns Road SPS is situated in open parkland, adjacent to residences (refer to Figure 5). To provide a safe working environment and reduce public exposure to site risks the pump station was provided with site fencing and programmable smart locks to control access and move away from the typical daisy chain setup.

What is scalable?
Including those who control and operate the infrastructure ensures the efficient delivery of improvements that not only meet serviceability requirements, but can also resolve operability issues and safety concerns of the end user. Common areas of focus, as highlighted through this case study, include: 

• Improving access conditions 

• Improving lifting arrangements 

• automating manual tasks 

• enhancing redundancy measures. 

Logan Water’s operator centric approach has been adopted widely, ensuring a sustainable renewals program for both water and wastewater infrastructure can continue to be delivered.

Acknowledgements 

The authors would like to acknowledge the support of key operations and design staff from the Logan Water team including but not limited to, Scott Dicker, Dean Baker, Col Barton, Mick Westaway, Bill Smith and Angus Heares. The support from suppliers Drapper Environmental Consultants and Mass Products was also important to the success of the project.