Health warning to remain on Lake Rotorua despite reduced bacteria levels

Wastewater overflowed from a maintenance hole and went into Lake Rotorua, promting a public health warning to stay out of the water. Photo / NZME

Bacterial levels have dropped in Lake Rotorua following a wastewater spill but a health warning will remain in place for at least another 24 hours.

The latest test results for the site of the wastewater overflow near Arnold St and Waiteti Rd in Ngongotahā have been analysed today and all showed reduced bacteria levels to below the recommended safe swimming level.

The test samples of lake water were taken yesterday at five points along the lakeshore in the area of last week's overflow.

A maintenance hole overflowed and spilt wastewater, described by locals as brown water "spraying like a fountain". It flowed from a manhole at a property, across the ground and into the lake.

The spill, blamed on a computer fault at the pump station, happened at 7pm on October 18. It is estimated that up to 20 cubic metres of wastewater may have reached the lake over three hours.

The council said in a statement that despite the favourable test results, Toi Te Ora Public Health had requested the health warning stay in place as a precaution until a set of secondary results indicated the water was safe for swimming.

The health warning, and the signage on-site, will remain in place for at least another 24 hours until further testing can be completed and analysed.

"Council officers are keeping in mind that rain overnight, and further rain forecast for this evening, may affect tomorrow's test results as it's typical to see elevated levels of bacteria in water after rain," the statement said.