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.

Part of the Vaucluse coastline where Sydney's last three ocean outfalls discharge untreated waste. Credit:Wolter Peeters

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.