Brookvale Road bore No.2, near Havelock North. This is one of the bores at the centre of an investigation into how the town's water supply became contaminated.

Assessments of the Havelock North water bores before the town's gastro outbreak by engineering firm MWH is under scrutiny after one of the bores was found to have a possible leak.

Testing of the bores undertaken this week by Hawke's Bay Regional Council has shown that surface water was unlikely to have entered the two bores during heavy rain in the days before the outbreak, but questions remain as to how MWH did not find a possible leak point in the bore head of bore No.1.

The MWH 'bore security assessment' of the district council's bores was completed on August 10 after site inspections made in May. The May inspections followed others made in June, 2014, when "some deficiencies" were discovered.

Marty Sharpe Brookvale Road bore No.1, near Havelock North. An inspection after the outbreak found a possible leak point in around the cable glands of this bore.

These had been fixed by the time of the May inspections, and the consultants concluded that "some minor works to remove the surface rust on the headworks is recommended for the future", but otherwise the two bores providing Havelock North's water were "now considered to be secure as currently constructed".

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SUPPLIED This shows the location of the bores that provide water for Havelock North (bore 3 has not been used since last year). The sunbursts show sites where the HB Regional Council has found significant loads of e.coli in surface water. The sunburst at the bottom is the test from the Mangateretere Stream.

​Hastings mayor Lawrence Yule said that in spite of these findings an inspection of the bores after the outbreak had "highlighted a possible leak point around the cable glands that pass through the No.1 bore head down into the bore shaft".

But it is unlikely the leak would have allowed contaminated water into the bore as flood testing of the bore this week had shown that its sump pumps and flood alarms had worked when water entered the bore surrounds, indicating that any water getting into the bores would not have been able to rise high enough to enter the the leak point. The flood alarm has also activated when the power was turned off, simulating the power cut that occurred during the storm of August 5-7.

Flood testing of Bore No.2 had shown that its pumps and flood alarms had also worked as intended.

Supplied This shows as red droplets the location of the 3 water supply bores in relation to Havelock North and the Tukituki River. The green boxes are other bores where no E. coli has been detected. The light orange boxes are water samples from the Tukituki River where typically low levels of E. coli have been detected. The red boxes indicate where low levels of total coliforms have been detected in bores. This is not E. coli. It is bacteria found in soil or vegetation.The sunburst shows where a high level of total coliforms was found in a bore.

Further testing will occur until late November in a bid to discover how the bug entered the water.

MWH was contacted for comment on Wednesday but has yet to respond.

The August outbreak made 5200 people sick and hospitalised 22. One woman, April Singh, has developed a serious neurological condition associated with campylobacteriosis, and two elderly women who died were found to have contracted campylobacter, but both had other health issues.

Last week FairfaxMedia revealed that there had been a previous campylobacter outbreak in Havelock North in July 1998 when bore No.2 was found to have been contaminated by two types of campylobacter.



