Workers uncovered several dozen ballast stones during reticulation works at the jetty, all roughly the same cut and weighing about 20kg each.
Initially, the rocks were believed to have been used to build the existing seawall but given the possibility that they had some historical significance, the City of Rockingham invited a geomorphologist to examine the rocks more closely.
The geomorphology report identified the rocks as being predominantly granite, some basalt and an ‘odd old brick’, and appear to have come from several different areas, including Bunbury, the Goldfields and possibly the Darling Scarp.
‘It is not possible to determine if they were used initially as ballast and then re-used in the seawall, or if they were brought in by road specifically as building material for the seawall,’ City of Rockingham Mayor Barry Sammels said.
‘Either way, the rocks discovered during the recent works are believed to be leftover quantities from the construction of the wall.’
A selection of the rocks has been provided to the Rockingham Museum. But the City does not plan to display the rocks in any other location or format as it believed the rock wall itself was a fitting display.
The finishing touches to landscaping are being applied around the jetty, which is expected to be completed and reopened by the end of the month.
The jetty construction has cost about $3.4 million.