When Yangebup Lake reaches its control level, the excess water is drained via the Woodman Point Wastewater Treatment Plant’s contingency outfall 1.8km offshore.
But Cockburn MLA Fran Logan said last week that Water Corp should stop doing that because Yangebup Lake was contaminated by an old wool scouring operation in Yangebup.
‘(I’m) disgusted that Water Corp is still pumping water from a lake which contains heavy metals and toxins straight into Cockburn Sound,’ he said.
‘It is totally unacceptable for Water Corp to transfer excess water from Yangebup Lake into a marine environment which is popular for fishing.’
The Water Corporation’s Perth regional manager Steve Dorricott said the transfer was safe and necessary under the South Jandakot Drainage Scheme’s environmental management plan, approved by the Environmental Protection Authority.
‘Maintaining the control level of the lake is important to prevent flooding of roads, properties and vegetation,’ he said.
The Water Corporation has promised to carry out regular water sampling at the point where it is drawn from Yangebup Lake, as it has done during previous water transfers.
‘The analysis of the daily water sampling indicates that there are no negative impacts of the discharge to Cockburn Sound,’ Mr Dorricott said.
A spokeswoman for the EPA backed the transfer: ‘This discharge was assessed by the EPA and is authorised by environmental approvals.’
Cockburn’s engineering and works director Michael Littleton admitted the City believes the lake’s sediment is contaminated but was confident there was no risk to people or Cockburn Sound.
He said of more concern was an excess of nutrients within the water which leads to algal blooms, providing a food source for nuisance midges.
‘There is little concern in terms of heavy metals, as these are thought to be locked up within the sediment,’ he said.
‘The City believes that flushing the lake will have positive impacts on the water quality within Yangebup Lake.’