Cranbourne Line Upgrade – Eumemmerring Creek Bridge – Environmental Outcomes

The Eumemmerring Creek Bridge was constructed as part of the Cranbourne Line Upgrade, delivered by the Level Crossing Removal Project’s Western Program Alliance (LXRP, MTM, McConnell Dowell, Mott MacDonald and Arup) and involved the duplication of the train track over the Hallam Main Drain and Eumemmerring Creek (E creek). The project is part of the Victorian Government’s commitment to remove 110 dangerous and congested level crossings by 2030.

With construction to occur at heights, near an active rail corridor, and over environmentally sensitive watercourses; the team devised a new way to deliver the project safely while protecting the existing environment. Our approach to environment and sustainability was comprehensive and focussed on enhancing opportunities for a thriving environment, as well as mitigating potential impacts:
• We designed an innovative 63-metre, 340-tonne steel, “floating” bridge without foundations or pillars installed into the waterway eliminating the need for crane pad construction (protecting the creek’s ecosystem):

• The 340-tonne bridge structure was safely assembled on the ground adjacent to the final location before launching into place over the creek
• The 162-tonne launch nose was reused from another project, saving over 300 tonnes of carbon emissions
• Horizontal directional drilling was completed under the watercourse to prevent any potential drilling fluid risks to the sensitive ecology
• First construction site in Victoria to use recycled content geofabric liner material (Bidim Green) to control ERSED risks.
  • Used innovative digital engineering techniques (e.g. a "digital twin", 4D model) to anticipate and address design challenges from working within a narrow 30-metre rail corridor while avoiding impacts to waterways and trees:
• Provided a clear visual representation of the complex engineering solution to facilitate understanding and collaboration across disciplines
• Ran virtual rehearsals of constructing the bridge to obtain valuable insights critical for successful transport, coordination, assemble, and launch.
  • Established a Tree Protection Plan – significant portions of native River Red Gums were retained, and environmental no-go zones established through clear delineation, signage and education
  • Maximised early engagement during the design phase with the community and stakeholders:
• Established a common commitment with the 'Friends of Eumemmerring Creek' and the Traditional Custodians to protect and enhance the environment
• Previously part of a ”carrum swamp land” (a significant food source for Traditional Custodians), their connection to country was incorporated into urban design. Food symbols on timber totems (felled timber from the site) were carved by a local Aboriginal men’s shed
• A dedicated environmental team maintained communication through regular meetings, joint onsite inspections and poster campaigns, with internal/external environmental stakeholders
• Organised clean-up days.
  • Temporary steel walkways and fibreglass grating were used to allow site access without disturbing flora and fauna, supported by the land owner water authority, used during construction for opportune access for weed management, survey etc.
  Eumemmerring Creek flows into and forms part of the nationally significant Port Phillip Bay. Through long-term protection of the watercourse and its downstream ecology, the project assisted in supporting a wide variety of natural habitats and aquaculture industries.

Over several years of design development, stakeholder consultation/reviews, construction delivery and recent landscape maintenance, the existing vegetation within the rail corridor, adjacent to and within the watercourse flood zones were considered, protected, and maintained. The result is a technically advanced rail bridge parallel to the existing bridge, large native trees retained adjacent to steel and concrete structures, enjoyed by thousands of passing train commuters every day, while the highly responsive to rainfall non-impacted water courses below, direct water downstream to a larger river system discharging into Port Phillip Bay.

The ecological connectivity maintained within the rail corridor throughout the watercourses further connected by extensive planting of native grasses, plants and trees is testament to a successful technical, environmental, and sustainable rail bridge and track duplication within a highly sensitive and maintained natural aquatic landscape.

The design of the steel-truss railway bridge launched over the watercourse revolutionises the construction of permanent rail infrastructure, with particular focus towards ecologically sensitive environments and terrains. It allows teams to incorporate the existing ecology into the temporary design and allow for the construction of permanent works while protecting the watercourse from potential aquatic and terrestrial environmental risks and impacts.

In particular, the team noted that mobilising a suitably large crane – in this case, a 1200/1600-tonne crawler – would require work to take place in the danger zone within the rail corridor, interface with overhead power and require extensive civil works to prepare a suitable crane pad area.

Alternative bridge construction techniques were industry-tested, with alternatives proposed by specialist heavy lift contractors. To determine the best solution the team undertook a multi-criteria risk assessment, which encompassed a number of key variables such as, environment, safety, rail safety, cost, and efficiency. The outcome of the assessment was a 'dry-dock' assembly and launch was chosen as the ideal methodology and enabled the bridge to be built in a ‘dry’ environment outside of the creek.

The digital engineering team developed a 4D structure model showing how the bridge would be built and identifying key risks, making an early analysis of the components, what sort of equipment was needed in transporting all elements to the site, and coordinating how it was assembled. 4D modelling also allowed them to identify and rectify early problems, including a clash between temporary and permanent retaining walls, and signalling cables and wall panels. The model provided a clear visual representation of a complex engineering solution, meaning team members across disciplines could easily understand the information.

After months of detailed planning, a ‘virtual launch’ of the 63-metre, 340-tonne steel bridge structure allowed the team to check every element of the design and construction before the real bridge launch occurred. This full digital rehearsal process helped the workforce provide informed feedback on how to complete the work safely.

The team used the 4D model in a series of Construction Risk Assessment Workshop (CRAW) sessions, which focused on how to control the heavy loads being lifted into place. These workshops included team members across disciplines and encouraged open collaboration about managing risk.

The bridge was assembled on a ‘dry-dock’ launching area with strand jacks comprising tension cables, sliding plates, and counterweights. This assembly process enabled the bridge to slide over the creek safely, a slow process moving at approximately8m per hour. This method minimised numerous hazardous working conditions, given its minimal interface with live trains and a reduced need to work from heights and over a body of water.

After actively and transparently sharing controls and lessons learnt internally and externally with stakeholders, councils, projects, and alliances, we also knew the project lessons could positively contribute to the industry. This was achieved by sharing our initiatives on social media and being featured on engineering websites such as Create Digital – powered by Engineers Australia and written for engineering professionals renowned as leaders in shaping a sustainable world.

Future implementation of this methodology will also provide benefits to the wider community:
• The bridge is assembled off site with no impacts to the existing track, so there will be minimal line disruptions
• Projects can be completed ahead of schedule.

Assembling the bridge offline reduced impacts to the existing rail bridge and minimised disruptions to commuters. The works were completed almost a year ahead of schedule. Trains now run every 10 minutes on average in the morning peak, for passengers travelling on the Cranbourne Line.

WPA maintained relationships to benefit several stakeholders:
• Bunuroung People of the Kulin Nation – Traditional Custodians of the land, performed smoking ceremony to open the public spaces – these :”parklets” were constructed to create a thriving environment for the entire community to enjoy
• EPA Victoria – our Environmental Management team offered EPA inspections during construction so they had visual context of risk profile and associated extensive environmental controls
• Melbourne Water – we donated 60 large root balls for fish habitats, and granted access (via temporary walkways) throughout multiple project areas to undertake weed spraying and survey that couldn't be done otherwise. We alleviated the risk of site water overflowing into stormwater assets by installing 300kL sediment runoff basin in catchment area upslope of stormwater outlet
• Dandenong Council and Casey Council – we donated plants, grasses, and timbers
• Heritage Rail – we donated rail materials, including concrete sleepers, steel track, and ballast
• Friends of Eumemmerring Creek – local environment group we consulted to alleviate fears regarding impacts to the ecologically sensitive creek and surrounding land forms. The group works to continually improve the creek by planting indigenous plants along the banks and cleaning up creek parklands.

This success has changed how the WPA team approaches the design and construction of bridges, specifically:
• The Old Geelong Road Level Crossing Removal Project team used the on ground assembly principle when developing Hoppers Crossing Station overpass
• Prefabrication was adopted by Mt Derrimut Road and Webb Street Level Crossing Removal Project teams for bridge girder works.

The design and methodology of the bridge have been shared with experts from different companies across the industry. Approximately 200 visitors attended Eumemmerring Creek in April 2021 to watch as the steel bridge was launched into place. Excellent feedback was received from attendees, many keen to receive the design drawings.

With its clever design and outstanding safety outcomes, the Eumemmerring Creek rail bridge methodology is easily replicated and suitable for rail bridge projects across Victoria and the broader rail industry.

Eumemmerring Creek is home to two endangered native freshwater fish species protected by the National Environment Protection and Biodiversity Conservation Act:
• Dwarf Galaxias – found in shallow, slow-flowing creeks and have become endangered due to habitat destruction
• Australian Graylings (a.k.a. the cucumber mullet) – found in cool, clear rivers and streams and have become endangered due to construction of artificial barriers that restrict their migration.

The project team’s ultimate goal was to ensure these endangered species were protected by eliminating any work that could have a negative impact on the creek’s ecosystem and to seek opportunities to create a thriving surrounding environment. We aimed to leave a positive legacy by:
• Engineering and building a single-span steel truss bridge that did not require a support structure in the creek (SDG 6)
• Horizontal directional drilling under watercourses, 4 and 6m below invert, (SDG 6 and 14) combined with the above point meant that water quality impacts to the creek were avoided as works within the riparian zone were avoided
• Maximising tree protection (SDG 15)
• Using recycled materials (SDG 15)
• Engaging with the First Peoples as Traditional Custodians of the land (SDG 17)
• Landscaping and First Peoples story telling (SDG 15 and 17).

We ensured the long-term protection of Eumemmerring Creek and its’ downstream ecology into Port Phillip Bay by dedicating our design and construction efforts to avoid touching the creek or any sensitive flora or fauna.
• Flora and fauna were completely undisturbed, because steel walkways and fibreglass grating were used to allow site access, and the bridge was built entirely outside of the creek’s environment. (SDG 6, 14 and 15)
• Although we were permitted to remove 9.6Ha, the non-destructive digging, selective limb clearance, no-go zones and other methods detailed in our Tree Protection Plan resulted in only needing to remove 5.8Ha, therefore retaining 30,000m2 of which was mature River Red Gum. (SDG 15)

• 80% (2.9688 Ha) of this retained vegetation was classed as Class D Open Woodland and the remaining 20% retained (0.7422Ha) was classed as Class I Grassland
• In total, the retention of this 3.711Ha of vegetation saved 993.0636T of CO2 emissions.
  • Successfully educated workforce by introducing targeted signage and awareness of protection of the River Red Gums
  • Steel structures fabricated for sheet pile walls and bridge assembly were successfully reused on another Level Crossing Removal Project, diverting approximately 10T from the project waste stream / refabrication. (SDG 15)
  • The 162-tonne launch nose was reused from another project, which saved over 300T of carbon emissions. (SDG 15)
  • Diesel required for a 300-tonne crane to otherwise carry a structure of this size was also saved.

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