Residents have voiced their fears over potential contamination of one of the region's most popular beaches after a downpour sent mud flowing into Coolum's First Bay.

Tuesday's deluge inundated Mosaic Property Group's First Bay development site on David Low Way, with residents capturing footage of mud and silt flowing through their neighbouring unit block, and what appeared to be mud flowing from the stormwater drain in front of the development site out into First Bay.

Mae Kelly said she noticed it about 4pm Tuesday when she got home from work.

"It was just pouring through the side of our house," she said.

She said she couldn't see any barrier or run-off diversion at her back fence next to the high-end apartment development site.

But the developers have assured no contaminated water entered the bay as a result of the "record-breaking" downpour, and that sediment containment measures were in place.

Ms Kelly said she looked out across the road to the usually pristine First Bay and was dismayed to see the silt flowing into the ocean on Tuesday afternoon.

"It was just red from all of the run-off," she said.

Mosaic Property Group managing director Brook Monahan said they had been working through the storms on Tuesday until "very late" to ensure additional measures were in place to increase their "already robust sediment controls in place".

"This was a 10-year record breaking downpour," Mr Monahan said.

He said they had effective and approved sediment control measures in place on the site, and they were in accordance with Sunshine Coast Council requirements.

"These measures did not fail - they worked as designed," he said.

"Unfortunately due to the severe nature of the rain event and the velocity of the water, there was some very minor sediment run-off for a short period of time.

DOWNPOUR: Tuesday's downpour sent run-off from a First Bay development site at Coolum.
DOWNPOUR: Tuesday's downpour sent run-off from a First Bay development site at Coolum.

"The team on site attempted to secure the boundary as best they could.

"The vast bulk of all sediment was contained by the sediment fence, which is not designed to stop water. It is designed to settle water and allow the bulk to overflow, capturing sediment before it does so.

"This is exactly what occurred yesterday, except some of the overflow water contained very low levels of natural earth sediments, which often happens in events of this nature. But this was not contaminated water."

Mr Monahan said Mosaic was installing additional measures "above and beyond council requirements" to try to anticipate as best they could further extreme rainfall events that could occur.

More rain is forecast for most of the week.

Storm water at Mosaic’s building site at First Bay, Coolum. Photo Patrick Woods / Sunshine Coast Daily.
Storm water at Mosaic’s building site at First Bay, Coolum. Photo Patrick Woods / Sunshine Coast Daily.

He said the amount of run-off that flowed on Tuesday was no greater than what would have been experienced if it had not been a construction site, and had been a vacant block without sediment fences.

"We also were hit with substantial sediment water flowing onto our site above on Coolum Tce, which was simply a result of the extreme weather event," Mr Monahan said.

Ms Kelly said her two-year-old daughter swam in the bay every day and she was worried about possible contamination from debris on the building site, and said there was now a "couple of inches" of red clay at the back of her unit block.

She said it wasn't the first time they'd had issues with water run-off on the site, and they'd contacted developers Mosaic previously about it.

She has lived in her unit for the past two years.

Heavy rain lashed Mosaic’s building site at First Bay, Coolum, on Tuesday. Photo Patrick Woods / Sunshine Coast Daily.
Heavy rain lashed Mosaic’s building site at First Bay, Coolum, on Tuesday. Photo Patrick Woods / Sunshine Coast Daily.

She said she thought the developer should be notifying the public about the run-off, as she feared the water quality in First Bay would be affected for some time, and she was concerned about the forecast for the rest of the week, with the potential for more run-off to occur.

Mr Monahan said Mosaic was "very mindful of our obligations to the community", and that had been recognised in their approach to their last development, Drift.

"We encourage open dialogue with stakeholders, listening and responding to concerns," he said.

"Site representatives were onsite last night and were in discussion with council regarding the situation, the remedies in place and the course of action implemented to rectify today (Wednesday), that is all currently underway."

Mosaic representatives said they had not recorded any run-off issues at their Avalon development site in Duporth Ave, Maroochydore, after Tuesday's heavy rainfall.

The Daily has also contacted Sunshine Coast Council for comment.



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