The main reservoir which holds Lake Hawea's residential water supply is likely to be cleaned after ongoing tests confirmed the unacceptably high presence of potential E. coli contaminants
Residents had been notified by Queenstown Lakes District Council water contractors they should boil drinking water after the presence of E. coli was detected in the township's drinking water supply in December.
QLDC 3 waters manager Gerry Essenberg told Wanaka Community Board members this week ongoing tests had produced results with a very high incidence of coliform bacteria at a Lake Hawea reticulation station on Lakeview Tce.
Mr Essenberg said the high coliform count was probably due to a dirty reservoir.
About 100ml of silt is estimated to be settled on the bottom of the town's main reservoir, which, to his knowledge, had never been cleaned, he said.
Contractors intend to shut the reservoir down for water blasting, which should take about three days, during April or May, he said.
Water supplies for residential households should not be affected as existing lake intakes will pump straight into the township's reticulated system during the purge, he said.
A chlorination of and flushing out of the system is expected to clear reservoir and reticulation of residual coliform bacteria.
However, the empty reservoir could potentially disrupt firefighting requirements as water pressure in the township dropped.
A water tanker would be required on standby in the case of an emergency callout, Mr Essenberg said.
