UPGRADE: An artist's impression of the new labyrinth spillway to be installed at Lake Macdonald.
UPGRADE: An artist's impression of the new labyrinth spillway to be installed at Lake Macdonald.

Have your say about dam work

SEQWATER is now entering the community consultation phase of its $100 million plans to upgrade the safety of Lake Macdonald's dam.

Residents are invited to have their say on "the potential impacts of the project and provide input for project planning”.

But what do we know and not know so far?

Noosa News met with Noosa Landcare general manager Phillip Moran, who is also a member of the Community Reference Group for the project.

"The dam is now 52 years old, and it's time for some maintenance,” Mr Moran said.

"The last work done on it was when it was raised in 1980.”

Mr Moran said the 8000-megalitre dam supplied half of Noosa's water supply, the other half coming from the Mary River.

In the past, the two-year project would have been simpler, "but since the Forest Acres estate was developed, there has to be more importance placed on social impacts”.

Mr Moran said contrary to some beliefs, the dam walls on the water treatment plant side would not get any higher, as the major work was at the spillway, where there are fears that it might not be able to withstand an earthquake.

"The spillway is the weakest point; its 'labyrinth' spillway replacement will control water overflow better,” he said.

Mr Moran said Seqwater was well-advanced in considering the environmental impacts, including the proposed "draw-down” of water to enable the works to be undertaken; this will see a controlled release of water into Six Mile Creek to drop the dam level by up to six metres.

He said most fish would go with the water release during the draw-down; the dam's edges would stabilise, a weed called water primrose would likely flourish but gradually disappear again as the dam re-filled.

A coffer dam will be installed to hold water back during the building of the new spillway.

But plans for traffic routes and management to handle what will be large volumes of truck movements are still in the planning process.

And there are no decisions yet on what volumes of traffic will access the site via Sivyers, Gumboil and Collwood roads, and through or round Cooroy into Lake Macdonald Drive, however, Mr Moran suggested Collwood Rd could be sealed as a result, and the Sivyers/Cooroy Noosa Road intersection would have to be assessed for traffic management.

"There will be a concrete batching plant built on-site,” Mr Moran said, indicating it would likely occupy space near or in the cod hatchery or scout camp grounds, both of which have closed for the duration.

He said the most likely issues for residents of the area would be the water draw-down, the concrete plant, and truck movements. Mr Moran said project work would be mostly confined to 6am-6pm weekdays, with occasional weekends.

Noosa Landcare general manager Phillip Moran with the Lake Macdonald Dam spillway in the background.
Phillip Moran at the spillway site. Alan Lander

Perch Park on Lake Macdonald Drive would close for the duration, but the Botanic Gardens would remain open and unaffected.

As for timing, he said the project would likely commence after the rainy months; perhaps in May or June 2019.

Seqwater wants to be made aware of all impacts in affected areas as part of its impact assessment phase, and residents can go to https://yourseqwater.com.au or visit Cooroy Library on August 14, 18 and 21.