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Drinking water Management Current Issues Update 7


Interesting findings to date from the national inquiry

25 th January 2017

The Government Inquiry into Havelock North Drinking Water (stage one issue 8 session) (future actions to ensure a safe drinking water for Havelock North) occurred on the 12 th and 13 th December 2016.

The remaining stage one issues (legal responsibilities; prior knowledge; source and cause; possible person or organisational failure; facts and incident management response; contingency planning and appropriate responses) starts on the 30 th January 2016 and is expected to take 2 – 3 weeks.

Issue 8 was brought forward to December due to Hastings District Councils need to plan for treatment options in order to meet the expected summer demand. Since the contamination event Havelock North has been supplied via a cross connection from the Hastings water supply scheme, but this is not expected to be able to cope with peak summer demand. The proposed solution is to install a treatment process of cartridge filter / UV and chlorine dosing on to the Brookvale Road bore 3, this is the newest of the 3 bores and was not in service last year. The current planned commissioning date for this is the 2 nd week in February.

This treatment process will provide for 5 log removal, recognising that 5 log treatment could be potentially more than is required to meet the minimum requirements as set out in the DWSNZ. However the driver for Council is to comply with the standard from day one rather than waiting for the results of 12 months of cryptosporidium monitoring. There is also a need to provide confidence to residents that the water supply is safe, and these considerations outweigh the costs of a cartridge filter installation for Hastings District Council.

It is also proposed to install online turbidity and conductivity instruments on the bore pre-treatment to provide additional real time monitoring and protection. Hastings District Council are currently considering if this should be applied to all bores in their region.

Hawkes Bay Regional Council withdrew the pending prosecution against Hastings District Council. Before a prosecution proceeds there are two factors that need to be taken into account, the first being that a prosecutor is satisfied that there is sufficient evidence to provide a reasonable prospect of conviction. The second is whether the public interest requires a prosecution. The second factor was seriously questioned during the Inquiries first day in December, resulting in the withdrawal of the prosecution and issuing an infringement notice instead.

A vacuum test was carried out on the Brookvale Road bore heads to see if they would hold a vacuum. The theory being that if a vacuum could be held this would indicate that the bore casing does not have a hole in it above the static water level. The vacuum test identified that the cable glands required some maintenance in order maintain the bore head integrity.

Brookvale Road bores one and two are housed in underground chambers, similar to other water supply bores in New Zealand. Brookvale Road bore three is newer and located above ground. Hastings District Council has been working on raising the bore heads in the region above ground and doing away with the chambers. One of the checks that have been carried out to ascertain the integrity of the Brookvale bores 1 & 2 chambers was to turn off the chamber sump pumps and flood the chamber to see if they hold water

A number of water supplies including Hastings District Council have gone away from relying on a presence / absence E.coli sample taken every few days as per the minimum requirement of the DWSNZ - to a numerated E.coli sample every day. This is still a 100 ml sample as a representation of up to many mega litres that could have passed through that bore in that day. One of the recommendations from the December inquiry session was to carry out 2 litre E.coli samples rather than a 100ml sample. I am unsure on how the logistics of this are working out for the laboratories, but I will let you know when I find out.

Fluorescent dye trace testing has been carried out in the surrounding area with the bores running to waste. There have been some challenges with the online detection instrument, but the preliminary results indicate that there is a potential path between a pond that occasionally occurs in the nearby Mangateretere stream and Brookvale Road bore one. This potential path could take only a few days for the water to transport from the pond to the bore. More information is expected on this prior to the inquiry resuming on the 30 th January.

Sheep faeces have been confirmed as the most likely source of the campylobacter.