An investigation into the cause of cracks in the walls at Roche Park Recreation Centre has found the facility was partly built over the old Wallsend Open Cut mine.
The Shire of Collie commissioned the investigation, which was carried out by Bunbury-based WML Consultants, after last year setting aside $65,000 to stabilise and repair the centre's walls.
WML's report, completed this month, found the south-eastern corner of the centre was built over the former pit.
After the mine was decommissioned, it was used as a tip until 1977 and excavations found the smell of decaying material about 1.5m below the surface. The pit may have reached up to 24m in depth.
"Due to the extensive nature of the mine workings and unknown depth of refuse, the future behaviour of the building can not be readily predicted," the consultants said.
On Tuesday, May 28, the council voted to carry out some of WML's proposed works at a cost of about $5000, which included lifting the pavers to determine the footings below the kitchen and change rooms, and carrying out a floor level survey to determine the magnitude of the settlement.
It also voted to conduct ongoing monitoring of the building over the next 12-24 months and to spend $10,000 plus GST for brickwork repair to internal and external walls.
The Roche Park Recreation Centre was completed in 1988, and structural cracking and subsidence to the building was first noted in 1992 in the minor sport hall, kitchen and change room areas. The cracking was repaired for aesthetic reasons, but has continued to worsen.
WML provided four options for the council to consider, the cost of which would have to be measured against the fact the centre was already 32 years into its expected 50-year lifespan.
The first was to use piling to shore up the slab. Shire building services manager Scott Geere advised the method would work, but was not financially viable.
Soil grouting could also be used to lift the slab back to the previous level, but it was difficult to predict the effectiveness or longevity of this solution. The third option was to continue patching the centre, but this may eventually lead to an unacceptable risk. The final option was to do nothing, but conduct ongoing monitoring.
