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The Waikouaiti River has been tested for lead and results are expected next week.
An Otago Regional Council spokesman said the river was tested regularly, but not for lead unless the council had a reason to believe it may be present.
The regional council was first made aware on January 18 of heightened lead levels at Waikouaiti and Karitane sites, and it tested the river after the no-drink notice was issued on Tuesday.
The spokesman said the reason for the two-week gap was because, on January 18, the Dunedin City Council had asked if the regional council’s compliance team was aware of any upstream discharges or pollution incidents on the Waikouaiti River that could account for slight increases in lead levels in the city council’s sampling of the water treatment plant.
The regional council told the city council it had no record of any activities, environmental incidents or discharges that could account for any increased levels.
Further information on the lead levels at the raw water reservoir were received on Wednesday this week, following the no-drink notice.
"At that time, it was determined that water sampling would be undertaken to identify whether lead levels are present in the source water of the Waikouaiti River," the spokesman said.
Testing drinking water was the responsibility of the water supplier, and while the regional council tested the river monthly, it was not screened for heavy metals.
It has also been confirmed the Macraes mine is not the source of the lead contamination.
The regional council spokesman said OceanaGold was required to monitor water quality, including lead and other heavy metal levels, each month in the upper North Branch of the river as part of the mine’s consent.
All results supplied to the regional council, which are conducted by an independent laboratory, had complied with the safe amount.
OceanaGold issued a statement on Thursday saying the contamination of the water supply was not associated with the Macraes operation or its gold mining activities.
"If the elevated lead levels were a result of our activities, the council would be aware of it through the extensive data we provide," the statement said.
The regional council spokesman said the city council’s helicopter flyover on Wednesday identified two areas of interest for the regional council to follow up, but when staff did so on Thursday, they ruled them out as sources of elevated lead levels.