The city’s last remaining ocean outfalls that discharge untreated sewage pose ‘‘very high’’ risks to public health, according to a report commissioned by Sydney Water.

The agency hopes the independent pollution study into the three discharge points at Vaucluse and Diamond Bay in Sydney’s east would prompt their closure.

About 2000 people a year have ‘‘primary contact’’ with the wastewater through swimming, spearfishing and scuba in the otherwise inaccessible section of the coast.

Visible plumes from the sewage outlets, labelled as ‘‘critical’’ health risks, sometimes extend more than 100 metres from the coastline. Modelling of bacteria pathogens indicate ‘‘the area is not suitable for swimming’’, the report said.

Risks to the environment are ‘‘high’’, with localised impacts including the formation of ‘‘brown fuzz’’, a mixture of algae, bacteria and hydroids, or jellyfish-like species, the report said.

‘‘[A]s the discharge wastewater is not treated, there is no capture of solid materials (e.g. toilet paper, sanitary products, wet wipes),’’ the report noted. Wipes and plastics were also found to be accumulating on the sea floor.

Kevin Young, Sydney Water’s Managing Director, said popular beaches such as Bondi continued to report good water quality despite their proximity to the discharge, given the ocean’s ability to dissipate the waste. Still, the pollution report was ‘‘the most comprehensive piece of work that we’ve done for decades’’, modelling health and environmental risks more precisely than before, Mr Young told the Herald. "It provides a strong case for moving forward."

The outfalls – which date from 1916, 1932 and 1936 – take waste from 10,500 people living nearby. Average daily flows amount to about 4 million litres, released close to the sea surface.

Sydney’s untreated waste ocean outfalls have been discontinued over the decades but closure of the three near Vaucluse has been stymied for decades in part because of local disagreement.

Concerns have ranged from whether upgrading the waste network would clear the way for an increase in housing development in the region, to possible negative impacts on property values from tunnelling.

Community consultation will begin next month to determine how the outfalls should be closed, with the most likely outcome involving diversion of waste to a treatment plant at Bondi Beach.

Sydney Water will look to include the project by the end of next year - if agreement is reached - in its next round of infrastructure works that will not begin before 2020.

Jeff Angel, head of the Total Environment Centre, said "it's about time" steps were being taken.

"Closing the outfalls should have been done in the 1980s," Mr Angel said. "Too much untreated sewage along with all the plastics pollution have gone into the ocean."

Gabrielle Upton, the member for Vaucluse and Environment Minister, also welcomed Sydney Water's report.

"Any outcome requires collaboration, so I’m urging our local community to actively participate in Sydney Water’s public consultation so we can both protect what the local community values and the environment," Mr Upton said.

Her colleague, Bruce Notley-Smith, the member for Coogee, said the report was "important for our marine environment which is so dear to the people of my electorate".

"These are the last untreated wastewater outfalls - this would surprise many in the community, and it’s simply time for them to go," Mr Notley-Smith said.

Justin Field, the Greens urban water spokesman, agreed it was "hard to believe that in 2018 we are still sending raw sewage out into our ocean".

“The public were expecting a government commitment and funding announcement to fix this pollution, not another round of consultation," Mr Field said.

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