Sewage treated at the plant exceeded the annual median limit for four of the Environment Protection Authority’s eight licence conditions, including for levels of E. coli, ammonia, phosphorous and suspended solids.

But Coliban’s water quality performance and regulation general manager David Sheehan said the breaches did not represent an “unacceptable risk”.

“Our risk assessment indicates that these additional discharges do not pose an unacceptable risk to downstream users, wildlife, livestock or the environment,” he said.

“We have conducted a risk assessment on the implications for downstream users, and as the water being released into the river is treated, we have advised Goulburn-Murray Water to inform their customers that river water is safe to use for irrigation, and stock and domestic purposes.”

But EPA acting north-west manager Paul Ratajczyk said while the breaches only presented a low risk to waterway health, the organisation was still considering whether Coliban would receive any sanctions based on any environmental impacts stemming from its management of the discharge.

“EPA has also taken samples from the Campaspe River and the upstream environment to determine any impacts/risks as a result of the discharge – these results are due within the next two weeks,” he said.

“EPA has also requested that Coliban Water prepare and submit a revised environmental risk assessment of its site – work is already under way to address the site’s capacity constraints.”

Mr Sheehan said while it was too early to assess licence performance for the current financial year, the current flow in the Campaspe River meant Coliban was now compliant with the dilution requirement of its licence.

The water is released into the Campaspe River north of Kyneton, eventually making its way to Lake Eppalock.