The first stage of important conservation works being carried out by the City of Fremantle at one of Western Australia's most significant heritage sites has been completed.
Since 2018 the severely eroded limestone cliffs at Arthur Head, the site of Fremantle's historic Round House, have been fenced off due to the safety risk from falling rocks.
Last year the City of Fremantle and the state government committed matching funding of $500,000 each for urgent works to stabilise and repair the cliffs.
The first stage of the conservation works was to repair the huge limestone wall on the eastern side of Arthur Head to the north of the Whalers Tunnel.
City of Fremantle Heritage Coordinator Gena Binet said a lot of effort was made to restore the wall to as close to its original condition as possible.
"The work involved filling in the badly eroded sections of the wall and repointing it with a lime mortar, while also preserving the visible areas of natural cap rock," Ms Binet said.
"We chose to use a lime mortar and render because it will allow the surface to breathe and naturally expel moisture, unlike the cement renders used in previous decades which contributed to the degradation of the wall.
"The pointing style is based upon existing physical evidence, knowledge of tradition building techniques and documentary evidence from historic photographs.
"We trialled a number of different combinations of local sands to achieve a mortar colour that most closely matched remnants of the early pointing in the area, with the mortar on the main face having a more pinkish tone while we used a whiter tone for the wall built around the top of the cliff face.
"Historically the sand for mortar was collected on site. The pinkish sand, called Terra Rosa or Spearwood Red, is found in pockets in the limestone cliffs while the white sand is found in eroding parts of the cliff face and also throughout coastal areas of Fremantle.
"The variation in mortar colour between the main face and the top wall is thought to have occurred because the original works were undertaken at different times as separate projects.
"I think the final result is an excellent outcome which preserves the heritage significance of the wall and also makes it structurally sound and safer for the public."
Although the restoration of the wall is now complete the car park at its base will remain fenced off and used as a set-down area for the next stage of the project, which is due to begin in March.
The second stage will involve extending the limestone retaining wall to the south of the Whalers Tunnel near the railway line.
This will be done by covering the exposed cliff face with plastic fibre reinforcement, extending the limestone retaining wall by about 15 metres and filling the gap between the wall and the cliff with concrete.
The final stage, scheduled to begin in May, will involve stabilising the cliff face above the western entrance to the Whalers Tunnel, reinforcing the entrance to the tunnel and building a new rockfall canopy.
The new canopy will be clad in corten steel and have Aboriginal artworks incorporated into the design. It will be supported on custom-made hydraulic buffers to cushion the impact in the event of a rockfall.
The project also includes the removal and restoration of the steel gates at the western end of the Whalers Tunnel and additional fencing around the site.
Planned future stages that are subject to further budget allocations include repairing the limestone walls around the top of Arthur Head, restoring the stairs and the eastern entrance to the Whalers Tunnel and works to repair and conserve the Round House itself.
A multi-disciplinary team led by Hocking Heritage Architects investigated and designed the solutions to stabilise the cliff faces. The team included structural engineers, historians and geotechnical engineers.
Between 1833 and the 1960s Arthur Head was extensively quarried to provide building material and to facilitate works on Fremantle Port and the railway.
The quarrying left the cliff faces exposed to the harsh coastal environment and has contributed to ongoing issues with cliff instability and erosion.
