Design solution

Level crossing removal projects are big and complex.

The Victorian Government has established The Level Crossing Removal Authority (LXRA) to oversee the delivery of 50 level crossing removals around Melbourne.

Each individual site is unique – what works in one location might not be suited to another. Detailed planning and technical work helps to identify the risks and opportunities at each level crossing removal location.

LXRA has developed a unique approach for removing the Seaford Road level crossing that lowers the road by up to 1.5 metres and places the rail line on to a planted embankment to separate road from rail.

This level crossing has been fast tracked for removal with a tender phase to start in 2017 and construction to start in 2018. The crossing will be fully removed and the project completed in 2019.

Removing the Seaford Road level crossing will help improve safety, reduce congestion and create new opportunities for the Seaford community.

LXRA has developed a unique hybrid approach for removing the Seaford Road level crossing. It involves lowering Seaford Road and placing the rail line on to a planted embankment.

Seaford Road will be lowered by approximately 1.5 metres, which is considered a safe depth without increasing the risks to the nearby wetlands and Kananook Creek. By lowering the road, the extent of rail construction is shortened from 900 metres to 700 metres.

Given the amount of space on either side of the rail line, sloped embankments with significant landscaping are possible in Seaford. These embankments would help to improve the appearance of the rail line, reducing the use of hard concrete structures. Architectural treatments are also being considered.

The hybrid solution significantly reduces environmental risks, compared with a rail trench option. Seaford Road will be lowered by around 1.5 metres which does not trigger any significant environmental risks.

Edithvale-Seaford wetlands

The Edithvale-Seaford wetlands are of international importance, listed under the Ramsar Convention on Wetlands Treaty 1971. The wetlands were listed as Ramsar wetlands in 2001.

Located approximately 700 metres to the north east of the Seaford Road level crossing, the site is connected hydrologically and hydrogeologically with the Seaford component of the wetlands.

The wetlands at Seaford are much closer to the level crossing than other sites, such as Edithvale and Bonbeach. This means there is a much higher risk of long term impacts to the wetlands at Seaford under a trench solution.

Highlighted distance of 700 metres between Edithvale-Seaford Wetlands Environment Area and Seaford Road level crossing. Interactive map link below.

View the interactive map

Kananook Creek

Kananook Creek flows parallel to the west of the Seaford Road level crossing.

Kananook Creek is already flow deprived and at only 10 percent of its historic flow. To maintain the health of this river, Melbourne Water pumps up to 160 ML/d of water from Patterson Lakes to Kananook Creek. Groundwater changes will have a negative effect on the health of Kananook Creek.

View the interactive map

Environmental risks

The natural environment is an important part of Seaford's local character.

When considering the best way to remove the Seaford Road level crossing, environmental factors are particularly challenging in terms of groundwater flows, flooding and potential impacts to the nearby Edithvale-Seaford wetlands and Kananook Creek.

These environmental problems ruled out the building of a trench at this site. This image shows the underground conditions at Seaford. In Seaford, there are clay layers that are close to the surface.

This is notably different to underground conditions in Edithvale and Bonbeach where this is more sandy soil which allows groundwater to pass through more easily.

A trench structure, combined with the clay, would change groundwater flow, as water would need to divert around the trench. This means that water levels on the inland side could rise, causing potential impacts to the wetlands. Water levels on the coastal side could fall, which would in turn affect the environmental values of Kananook Creek.

Diagram highlights rail trench between groundwater drawing down from the coast and groundwater mounding up from the inlands. Kananook Creek sits above the groundwater drawing down. The entire ground underneath is clay.

Our investigations into a trench at Seaford have identified risks for up to four different criteria that give the wetlands their international significance, causing threats to the site's ecological values.

The wetlands are a groundwater dependent ecosystem and changes to water levels or quality could have a significant impact on the ecological character of the wetland, including impacts to vegetation and habitat provided for the threatened and migratory species that the wetland supports.

Geotechnical drilling, where boreholes are drilled up to 40 metres beneath the earth's surface, help to build an underground profile of the area. It is important to understand the ground conditions and underground water levels before starting any major construction project.

These maps show the modelled long-term impacts to groundwater at Bonbeach and Seaford under a rail trench scenario. The impacts at Seaford are more far-reaching.

Community considerations

Community consultation and feedback is an important part of any major project. LXRA seeks the views of the community and stakeholders on what is important in the local area and uses that information to assess the potential benefits of the design, as well as likely impacts and how they can be mitigated.

Feedback

The project needs to be in keeping with the local character of the area.

Technical response

The design solution lowers the road to minimise the visual presence of the rail line as far as possible without compromising the water table, triggering flood management issues or significantly impacting the environment.

LXRA will work with the community regarding specific design features, which might include wooden cladding, additional vegetation on planted embankments and new walking and cycling paths.

Feedback

The natural environment is an important part of Seaford's local character.

Technical response

We've undertaken flora and fauna assessments and extensive geotechnical drilling to help us understand potential environmental impacts. We are lowering Seaford Road by around 1.5 metres, which will not compromise the water table or groundwater flows.

While there will be some vegetation removal, there are no recorded threatened species or significant Ecological Vegetation Classes in the area. We will provide significant planting and landscaping as part of the project, boosting environmental values in the area.

Feedback

There was community feedback which indicated a preference for a rail trench.

Technical response

All feasible options have been fully investigated and designs have been amended and reassessed to identify the best possible outcome under all criteria.

After undertaking technical investigations, we have had to rule out a trench option because of the impact on the plant and wildlife of the Seaford wetlands, which are internationally significant and protected.

However, taking in to account local concerns about the rail bridge option we presented last year, we've developed a unique hybrid solution for Seaford where the road will be lowered and the rail raised on a short planted embankment.

A rail bridge would have been 8 metres high, but this will only be 5 metres above the existing road level.

We're looking at innovative ways to ensure the rail line fits with the character of the area, including significant planting and embankments.

View the PDF print version of the technical report PDF, 1.4 MB