A pond at Rotorua's Wastewater Treatment Plant has overflowed and flowed into the Puarenga Stream.
On its website, Rotorua Lakes Council said there had been a "very high inflow" into the treatment plant yesterday and overnight which "exceeded the rate at which our pumps can pump treated wastewater to theforest".
"That has caused an overflow of the pond which stores treated wastewater and from where it is pumped to the forest. The treated wastewater - which has been further diluted by rainwater - has flowed to the Puarenga Stream.
"The pond started overflowing at about 4am today and the pumps are working at full capacity in an effort to stem the overflow. All systems at the plant are operating at capacity."
The same occurred last month following two weather events within one week.
"Excess amounts of rainwater have flowed into the sewer network and gone through the treatment plant, along with wastewater, which has exceeded capacity and caused the overflow."
It said the council would over the next few months review its programme to identify where stormwater is entering the wastewater system.
"However, this will not be a quick process and there is no temporary fix."
The proposed upgrade of the wastewater treatment plant will increase the plant's capacity and treat wastewater to even higher levels, reducing the potential for such incidents to occur in future.
