The second stage of conservation works to repair erosion and stabilise the cliffs at Fremantle's historic Arthur Head has been completed.
Arthur Head is the site of the state heritage listed Round House, WA's oldest public building.
Stage two of the conservation works involved the extension of the large limestone retaining wall on the eastern side of Arthur Head, adjacent to the railway line.
The completion of the second stage means the footpath running parallel to the railway line will reopen on Friday, with work on the third stage - including the installation of a new rockfall canopy at the western end of the Whalers Tunnel - to begin next week.
Arthur Head Project Officer Paul De Young said the construction of the retaining wall proved to be a challenging and time-consuming exercise.
"Our original intent was to anchor the new limestone wall to the eroded cliff face and then backfill it with concrete, but when we started drilling the anchor points we discovered a large number of voids in the cliff and that the whole face was quite unstable," Mr De Young said.
"We revised the angle of the wall design to make it a gravity retaining wall, which we had to build layer by layer and then backfill with concrete as we went.
"As an added complication, to be sympathetic to the heritage of the site we were using a traditional lime mortar which took a long time to dry, especially with all the wet weather we've had over the past few months.
"Now that the wall is finished it means we can move around to the western side and get started on dismantling all the scaffolding and installing the new rockfall canopy at the entrance to the Whalers Tunnel."
The third stage of the Arthur Head conservation project will involve stabilising the cliff face above the western entrance to the Whalers Tunnel, reinforcing the entrance to the tunnel and building the new rockfall canopy.
The new canopy is custom made and will be clad in corten steel, with Aboriginal artworks incorporated into the design.
To allow for the installation of the canopy the Whalers Tunnel will be closed to pedestrians from Monday and detours will be in place.
Since 2018 the severely eroded limestone cliffs at Arthur Head 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.
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.
The first stage to repair and repoint the imposing limestone wall to the north of the Whalers Tunnel was completed in January.
Planned future stages, including repairs to 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, are subject to further grant allocations.
The Round House was the first permanent building in the Swan River Colony and is the oldest public building still standing in Western Australia.
It was built as a jail and opened in 1831, with the Whalers Tunnel added in 1838.
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.
