Putrid sediment ponds in Lime Kiln Bay Wetland to be cleaned out

A sediment pond in Lime Kiln Bay Wetland.
A sediment pond in Lime Kiln Bay Wetland.

Georges River Council is moving to clean out putrid sediment ponds in Lime Kiln Bay Wetland and refocus future maintenance efforts.

The state of the ponds was revealed by the Leader in February, with environmental groups blaming increased development for growing stormwater pollution.

The ponds capture coarse sediments and pollutants that have got through gross pollutant traps upstream in Daisy Creek.

Lime Kiln Bay Wetland.

Lime Kiln Bay Wetland.

They are covered by algae, which feeds off concentrated levels of nitrates and phosphates, from detergents, fertilisers and dissolving dog droppings. 

Chair of Botany Bay and Catchment Alliance, Brian Shaw, contacted Oatley MP Mark Coure about the situation, and he wrote to the council.

Council general manager Gail Connolly replied, saying sediment was last removed from the wetland in October, 2014.

Ms Connolly said the the maintenance and operation plan stated desilting of the wetland was required only every seven to 10 years.

”However, council staff recently visited the wetlands and agreed that further partial removal of sediment from the first two sediment ponds would be beneficial,” she wrote.

”Council staff are currently investigating potential funding sources for this work to be undertaken."

A sediment pond in Lime Kiln Bay Wetland.

A sediment pond in Lime Kiln Bay Wetland.

A council spokesman told the Leader the former Hurstville City Council had concentrated more on removing sediment from the constructed wetland, and undertook only partial removal from the first two sediment ponds.

“Georges River Council will now focus on removing sediment from the first two sediment ponds and not the constructed wetland,” he said.

Mr Shaw said it was pleasing the council was planning to clean out the ponds.

“But, they may do much better by working on stopping the silt from Oatley West, Mortdale and Mortdale Heights from entering it in the first place,” he said.

”Modern thought would have rain gardens and swales placed in parks and footpath/gutters would help extensively.”

Mr Shaw said he was certain state and federal MPs from the area would be open to approaches to secure funding for such initiatives.

Streams running into Georges River through Lime Kiln Bay Wetland and the adjoining area have also been polluted by raw sewage.

Heavy rainfall in February and March caused sewage pipes to overflow on numerous occasions.

Geoff Francis, a member of Oatley Flora & Fauna Conservation Society and a Georges River bushcare volunteer, was advised by Sydney Water on March 13 of sewage overflows in Myles Dunphy Reserve on February 26, March 1, and March 3.

There had also been an overflow during dry weather upstream of Lime Kiln Bay Wetland on the afternoon of Saturday, March 11.

Mr Francis said Sydney Water measuring equipment gave an accurate time for the start of overflows, but not when they finished.

The recorded end times were when the sewage level dropped below a sensor in the pipe, not when the overflow stopped.

”On March 3, I observed a small overflow going at 4.25pm, and suspect that the sewer was overflowing more or less continuously from 10.20am until late at night,” he said.

Mr Francis said Sydney Water said the dry weather overflow on March 11 was caused by a tree root blockage.

“One of the problems of locating sewers in bushland reserves is that tree roots growing towards moist areas break into sewer pipes,” he said.