Specialist divers are expected to begin repairs on a damaged sewer pipe beneath the Anglesea River today.
A leak in the main, which was carrying about 85 per cent Class C recycled water from Aireys Inlet and 15 per cent sewage from west Anglesea, was discovered last week.
Barwon Water's General Manager Water Systems Carl Bicknell said a diver who inspected the pipe on Monday identified a 12cm-long damaged section.
He said a dive team would conduct a further assessment of the pipe today.
"Working underwater poses a number of challenges, not the least the lack of visibility," Mr Bicknell said.
"The team today will clean around the pipe with specialist equipment to enable a more thorough assessment of the damage before commencing repairs."
The pipe crosses the river between River Reserve Road and Wray Street, Anglesea, and connects with the town's water reclamation plant.
The pipe was shut down as soon the leak was located, warning signs erected along the river and relevant agencies, including the Environment Protection Authority and Corangamite CMA, notified.
Testing showed only moderately elevated levels of E.coli near the spill site.
"Samples taken when the spill was detected showed a maximum reading of 2,900 organisms per 100 millilitres. By comparison, raw sewage is more than 1 million organisms per 100 mL, or more than 340 times greater than the sample," Mr Bicknell said.
"Within 48 hours the reading at the spill site was 310 — well below the acceptable level of 1,000."
The signs were removed when monitoring showed water quality was within safe levels.
Mr Bicknell said the signs were placed at the site of the spill because it was very localised.
"The effects of the spill were significantly reduced further downstream due to the high volume of recycled water and the dilution effect of the river," he said.
"We are confident there was absolutely no risk to the community"
Mr Bicknell reassured residents the yellow foam present in the river was not related to the spill.
He said the EPA had advised the yellow substance was pollen.