Sewage spill closes Tasmanian oyster farms ahead of peak Christmas trade

A sewage spill has cost four southern Tasmanian oyster farmers hundreds of thousand of dollars in lost Christmas sales.

The farms will close for three weeks after an intense downpour of rain 10 days ago caused an overflow at a wastewater pumping station, spilling sewage into the Coal River near Richmond.

The spill has affected about 10 per cent of the industry, amounting to 80,000 to 90,000 dozen oysters bound for the interstate market.

Employees have been laid off because harvesting has been halted.

Oysters Tasmania is concerned about the impact on the industry's export brand but spokesman Adam Saddler assured the public that all oysters currently for sale in the state were safe to eat.

He said it was the worst time of year for it to happen and it would have a big impact on farmers.

"It's a significant impact, it's hundreds of thousands of dollars," Mr Saddler said.

"The monetary impact of not being able to sell their product, secondly there's employment and people have been laid off and that's because they can't harvest."

TasWater is analysing water samples from the area and investigating ways to prevent the overflow from happening again.

One of the affected growers, John Poke, does not want to see a repeat.

"Any business must control their waste, TasWater is no different to anyone else," he said.

"The councils are the shareholders of TasWater, we've just got to explore what possibilities we can to stop it happening again.

"This one, I think, was not a high flow of water, while it was localised to the Richmond area and just one pump station, we think there's engineering issues that can be undertaken to overcome it."

Last year, there were calls for urgent improvements to sewerage infrastructure after similar incidents affected oyster farms.