In a statement on Friday, Cedae said a network of new underground drains will redirect sewage from the Gloria Marina to a submarine outlet at Ipanema beach in the city's south.

The announcement comes less than two months after Guanabara Bay's waters was criticised by local and international competitors during an Olympic test event.

"Work will start immediately because the most difficult part - the acquisition of special pipes - has already been completed," Cedae president Wagner Victer said.

Backed by Rio's state government, the project has been budgeted at USD 6 million and is expected to be completed by October 2015.

The new system will comprise 1km of "collector" drains ranging from 40 to 70 centimetres in diameter. It will also boast a pumping station capable of releasing 450 liters of sewage per second.

According to Cedae, the environmental impact of excavation will be minimised by the use of tunneling shields.

Last month government spokesman Leonardo Espindola said 50 percent of sewage that flows into Guanabara Bay now receives treatment compared to only 15 percent in 2007.

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