Chlorination of the Hastings district water supply looks set to continue for the foreseeable future as the council awaits further information about the security of the water supply, and endeavours to ensure adequate water volume is available over the peak-demand summer months.
The management of drinking water supplies for Hastings, Flaxmere, Havelock North and Bridge Pa has come under the spotlight following the contamination of Havelock North's water in August, and is to be considered by the Hastings District Council at a full council meeting today.
As a result of the contamination, chlorine was introduced to treat the water for a three-month period, but this will need to be extended in light of further positive E.coli test results in the water supply, and the need to provide extra water over summer.
In a report to the council, group manager asset management Craig Thew and chief executive Ross McLeod said that after the Havelock North water supply was switched over to come from the Hastings supply following the campylobacter outbreak, positive E.coli results were found during testing.
These included two positive tests at the Wilson Rd bore on August 19 and September 21 and one at the Willowpark bore on October 1 - although subsequent tests, which are being carried out daily, have been clear since.
These tests were carried out in the well water, which is treated with chlorine further down the pipework.
"The transgressions that have occurred have significant implications for the Hastings supply, and complicate any council or community aspiration to remove treatment via chlorination in the short to medium term," the report said.
"This is particularly the case in respect of the Wilson Rd bore. At present, chlorination is the only safeguard in place to protect consumers from a source of water that has recently twice tested positive for E.coli."
The Wilson Rd water source was a vital part of the Hastings water supply, it said, and could not be turned off in the short-term.
To bolster the water supply over the summer months, it's been proposed to use Brookvale Bore 3, with up to $500,000 spent on treating it with UV, cartridge filtration and chlorine.
Hastings mayor Lawrence Yule said to his knowledge this bore, which was not running at the time of the gastro outbreak, had never tested positive for campylobacter, but had recorded low levels of E.coli contamination.
This supply would not be operational until signed off by the district health board's drinking water assessors, and the report noted that with treatment it would meet national drinking water standards.
Any decisions on treatment options were also influenced by GNS Science testing being undertaken to determine the age of the council's water supplies - where older water was more secure, while newer water less than a year old was considered more prone to contamination.
Mr Yule said these factors meant the council had a legal requirement to continue chlorination at this point in time, until other potential alternatives could be consulted on, such as UV treatment.
"We could forgo chlorination and have UV treatment but that could be at a cost of $5 million.
"At this point we have got to get through this summer with drinking water that is safe. Hopefully in March next year when the government inquiry has been completed and we have detailed costings of other options such as UV we will be able to do a major consultation with the community.
"At the moment we have no choice under the drinking water standards to keep the chlorine, at least in the short term."