The Taupo township received more than 85mm of rainfall in a two hour period on Friday night, causing stormwater to pour into the wastewater system and a suspected spill into Lake Taupo.
The thunderstorm saw 85.2mm of rain recorded at the Taupo Airport between 7pm and 9pm.
Operational services group manager Kevin Strongman said with rainfall of that intensity, some of it entering the wastewater system was unavoidable.
The suspected spill at Two Mile Bay, near Matuku Street, was notified to the council on Saturday afternoon and staff acted quickly to take water samples and have them tested. Signs were erected in the vicinity as a precaution, warning swimmers to stay out of the water in the area.
Mr Strongman said it was difficult to confirm the Ecoli readings were a result of a wastewater spill as in extremely heavy rain, the runoff could also contain Ecoli due to animal faeces and other contaminants being washed into the stormwater system.
"The readings are highest at the stormwater outlet so it may in fact have been run off, rather than a spill. We were alerted because a manhole had become dislodged due to stormwater entering the system at speed," he said.
"Regardless, the results have shown Ecoli readings above the recommended levels so we are following the Ministry of Health guidelines and leaving the signage in place in the affected area."
Water samples were being taken daily and it was hoped the readings would have returned to acceptable levels by tomorrow.
4 December 2017
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