E coli outbreak cause not fully determined
An Otago Regional Council investigation into an e coli contamination in Lake Hawea’s reticulated water supply has proven inconclusive, but a council engineer believes stock effluent was the cause.
Council environmental officer Stephen Smith said the investigation was conducted about two weeks after the contamination was found on January 7.
At a Wanaka Community Board meeting on January 28 Queenstown Lakes District Council infrastructure engineer Nicola Greaves told the board the contamination was likely caused by nearby stock effluent.
‘‘Finding out the cause two weeks later is difficult to conclude,’’ Mr Smith said.
Several factors could cause e coli contaminations including bacteria found in human, animal and bird faeces.
There was evidence of ‘‘pugging and erosion of the river bank’’, Mr Smith said.
He spoke to the farmer of the land who was adamant there had not been stock in the area since September. While it was not an offence to have stock in the lake or river, it was if it caused contamination.
The area was a ‘‘ minor tributary’’ and ‘‘swampy environment’’ and could stay static for a very long time, Mr Smith said.
‘‘The water doesn’t run regularly down it,’’ he said.
The investigation, while ‘‘certainly justified’’, could not conclude what the cause was.
The farmer was provided with information about his obligations under the water quality rules.
The Queenstown Lakes District Council has indicated the town’s water supply should start to be taken from new underground bores located at Scott’s Beach from mid-year.
The water would be subject to UV treatment only and should eliminate the need to have periodic chlorine treatment, which has been required in the past when e coli contamination had been detected in the water sourced directly from the lake.
Eilish Keane started at Wanaka Primary School on February 3.