The City of Canning has spent more than $400,000 on the Centenary Park West site in Wilson and is investigating the effectiveness of the planted wetlands in filtering nutrients and heavy metals.
Two other sites, lots 3007 and 3008 Bywater Way in Wilson and 300 Adenia Road in Riverton, also require investigation.
An Environment Regulation Department spokesperson said there were various options available to intercept or mitigate the flow of contaminants.
‘Constructed wetlands have been shown to be an effective means of treating contamination which may be migrating from disused waste disposal sites into aquatic environments,’ the spokesperson said.
‘Where options such as constructed wetlands are not an effective remedial approach, other technologies can be considered, such as sub-surface impermeable or permeable reactive barriers, walls or drains.’
Swan River Trust river systems management manager Mark Cugley said the sites along the Canning River had contaminants such as metals, pesticides and petroleum by-products.
He said the Trust and the Department of Water had held a study of contaminants in the sediments and waters of the Canning Estuary at Clontarf Bay adjacent to Centenary Park.
‘Contaminant levels in this area were generally low and the site is not ranked as a priority when compared to other locations that have been examined throughout the Swan Canning estuary,’ he said.