Waiwhetu Aquifer- chlorination

The recent chlorination of Lower Hutt’s water supply is to continue while investigations into the source of recent positive E.coli test results are underway. The water remains safe to drink.

A sample from a bore in the Waterloo wellfield returned a positive E.coli result on 12 April 2017. This was the third positive E.coli result in five months from water sourced from the Waiwhetu Aquifer. This, plus recent water quality testing across the aquifer showing an increasing amount of bacterial activity, has led to the decision to keep chlorinating the Lower Hutt water supply network while investigations are ongoing.

The public fountains at Buick Street (Petone) and Dowse Square (central Lower Hutt) have been closed as a precautionary measure because they can’t be chlorinated.

Frequently asked questions - updated 28 June 2017

1. Where does my water come from?

We have three water treatment plants that supply water to Wellington, Porirua, Upper Hutt and Lower Hutt:

  • Te Marua Water Treatment Plant
  • Wainuiomata Water Treatment Plant
  • Waterloo Water Treatment Plant

Te Marua Water Treatment Plant usually supplies Upper Hutt, Manor Park, Stokes Valley, Porirua and the western suburbs of Wellington, as far south as Karori. This supply comes from the Hutt River and is chlorinated.

Wainuiomata Water Treatment Plant usually supplies water for Wainuiomata and, together with the Waterloo Water Treatment Plant, Wellington's business district and the city's southern and eastern suburbs. This supply comes from the Wainuiomata and Orongorongo rivers and is chlorinated.

Waterloo Water Treatment Plant sources it water from the Waiwhetu Aquifer and supplies both Lower Hutt and Wellington. The Wellington supply is chlorinated and, blended with water from Wainuiomata Water Treatment Plant, supplies Wellington's business district and southern and eastern suburbs. The Lower Hutt supply is currently being chlorinated due to the increased bacterial activity being found in the aquifer and supplies Lower Hutt (apart from Manor Park and Stokes Valley, which are supplied from Te Marua).

2. If the recent water quality tests come back clear, why are you still chlorinating?

We are seeing a trend of increased bacteria activity in the aquifer which, together with the recent positive E.coli indicator test, we are treating as a signal for further investigation. We’re exercising a high level of precaution and are continuing to chlorinate the water we take from the aquifer while further evidence is gathered around why this is happening. Public safety is our number one priority which means we have to chlorinate as a precaution.

3. What do the health authorities say?

Wellington Water is working closely with Regional Public Health. Regional Public Health is satisfied with the measures put in place to ensure the water is safe and advise that there is no need to boil it before drinking.

4. What is the history of positive E.coli test results in comparison to this year?

In the last five months, we’ve had three positive E.coli results in Lower Hutt. These are indicator tests and are a sign that further testing is needed. In all three cases, further tests came back negative.

However, most importantly, two of these recent positive results have come from the water source, not in the distribution network. Before December 2016, we hadn’t ever had a positive E.coli result from the aquifer source. More specifically, there is also an increasing number of total coliforms (indicator bacteria) being found in the source water. This is an indication that something has changed within the aquifer and further investigation is needed.

Last five months:
  12 April 2017 – positive E.coli test from Mahoe St bore. All further tests have been clear, chlorination remains in place. Bore taken out of service.
  4 February 2017 – positive E.coli test from Naenae Reservoir. All further tests were clear, chlorination remained in place for three days of clear testing. 
  2 December 2016 – positive E.coli test from Colin St bore. All further tests were clear, chlorination remained in place for three days of clear testing. Bore remains out of service.

5. How long will the aquifer water be chlorinated for?

This depends on the results of Wellington Water’s investigations. These investigations are expected to take a number of months to complete and the water sourced from the aquifer will remain chlorinated during this time. Depending on the outcome of Wellington Water’s investigations, there is a likelihood that a permanent treatment solution will be required at the Waterloo Water Treatment Plant (such as chlorination and ultraviolet light), in line with the treatment standards in place for the rest of the metropolitan Wellington.

6. Why did you close the public fountains at Buick Street (Petone) and Dowse Square (central Lower Hutt)? When will they be open again?

The Buick Street fountain in Petone is now open with UV, non-chemical treatment. The Dowse Square fountain will open again in the next few weeks with the same treatment. 

7. Why didn’t you shut the public fountains the first two times E.coli was found?

Only recently has the number of Total Coliforms found in the aquifer water been increasing. This, plus the third positive E.coli result in five months, led to the decision to keep chlorinating the Lower Hutt water supply network and to close the public fountains.

8. I haven’t been feeling well for the past few days, could this positive E.coli result be the reason?

No. Your tap water has been and remains safe to drink. If you have any health concerns please see your doctor or contact Healthline (0800 611 116).

9. Is the water safe to drink for children and the elderly?

Yes, the tap water has been and remains safe to drink. If you have any health concerns please see your doctor or contact Healthline (0800 611 116).

10. Will chlorine affect my health?

Current studies indicate that using or drinking water with small amounts of chlorine does not cause harmful health effects. Its widespread use has been a major factor in reducing illness from waterborne diseases.

If you feel your skin getting dry or ‘itchy’ use moisturiser after having a shower or bath. If you notice increased skin irritation, asthma symptoms or other symptoms – seek medical advice. Even with the small volumes of chlorine used, some people will be able to taste it and some will notice the smell.

11. Can chlorine affect existing conditions?

Yes, in a small number of people chlorine can be an irritant for an existing condition such as asthma or eczema. If you notice increased skin irritation, asthma symptoms or other symptoms - seek medical advice.

You can contact Heathline 24/7 free on 0800 611 116 or your family doctor (GP).

12. Why can’t the public fountains be reopened with a warning that this water should be boiled before drinking?

The Buick Street fountain in Petone is now open with UV, non-chemical treatment. The Dowse Square fountain will open again in the next few weeks with the same treatment.

13. What are the investigations that Wellington Water is carrying out?

There are four broad areas of investigation in progress to help provide some answers into what might have caused the increased activity, and what are the next steps:

  1. Possible sources of contamination at the borefield 
  2. Alternative supply options in the event that the borefield is closed permanently
  3. Possible influences on the wider borefield area 
  4. Treatment options to ensure the safety of the drinking water

We’re also helping Greater Wellington Regional Council carry out wider investigations into potential sources of contamination for the aquifer.

The investigations into the possible sources of contamination are focusing on the security of the bores which draw water from the aquifer. The bore casings descend approximately 30 metres below ground level into the aquifer, so the casing seals and boreheads at the surface are being tested to ensure they are not leaking. This work is set to be complete in late June, after which decisions on long term treatment requirements can be made.

14. When will the results of these investigations be known?

The investigation into the possible sources of contamination at the borefield is due to be completed by late June. The investigation into the treatment options to ensure the safety of the drinking water is also expected to be finished by late June. The results of other investigation streams (supply options in the event the borefield is closed permanently, and possible influences on the wider borefield area) are still a number of months away.

Updates will be available on Wellington Water’s and Hutt City Council’s websites.

15. How likely is it that the aquifer water will be permanently chlorinated?

A decision on the permanent chlorination of Lower Hutt’s aquifer water has yet to be made. This decision depends on the result of Wellington Water’s investigations and further discussions between Regional Public Health, Greater Wellington Regional Council, Hutt City Council and Wellington Water. Depending on the outcome of Wellington Water’s investigations, there is a likelihood that a permanent treatment solution will be required at the Waterloo Water Treatment Plant (such as chlorination and ultraviolet light), in line with the treatment standards in place for the rest of the metropolitan Wellington.

16. The earthquake was in November 2016, why have you waited until now (five months later) to decide the aquifer needs to be investigated?

Wellington Water has been carrying investigations into the aquifer since the earthquake. These investigations will take a number of months to complete.

17. How will you keep us updated on the situation?

Wellington Water and Hutt City Council will be updating their websites and Facebook pages on a regular basis.

18. Is this related to the November 2016 earthquake?

It may be as the recent positive E.coli results and the increasing bacterial activity in the aquifer water started after the earthquake. Wellington Water will be looking into this as part of their investigations.

19. Is this related to farming?

No, the aquifer is located below an urban area.  

20. Is there any place in Lower Hutt to get access to unchlorinated water now?

The Buick Street fountain in Petone is now open with UV, non-chemical treatment. The Dowse Square fountain will open again in the next few weeks with the same treatment.

If your water has a chlorine taste, try putting the water in a container or jug in the fridge (this helps the chlorine dissipate from the water). Boiling the water also helps take the chlorine taste out of the water.

You may find that using a water filter that uses carbon filtration helps. Please consult the manufacturer's instructions on recommended use.

21. Can people still drink water taken from the public artesian wells before it was closed?

Yes. Other water quality tests taken at the same time and since the positive E.coli test result have been negative. The public fountains have been closed as a precaution as they can’t be chlorinated.

22. What if I have drunk water from the fountain recently?

Water quality tests at other locations taken at the same time as the positive E.coli test (and since) have been negative. The public fountains have been closed as a precaution as they can’t be chlorinated.If you have any health concerns please see your doctor or contact Healthline (0800 611 116).

23. What role will central Government have in this?

Wellington Water is working closely with Regional Public Health. Regional Public Health is satisfied with the measures put in place to ensure the water is safe and advise that there is no need to boil it before drinking

24. Is this issue similar to the water quality incident in Havelock North last year?

No. Havelock North had a number of unwell residents (that was traced to the water supply) while we have none. The elevated bacterial level in our aquifer water is an indicator that we need to investigate and we are taking a precautionary approach by chlorinating the water supply.

25. Now that chlorine has been added to our water supply, will fluoride be added to the water supplied to Petone and Korokoro?

Our focus is on investigating the positive E.coli test results and the increased bacterial activity in the source water. There are no plans to change the current fluoride status in Petone and Korokoro.

26. Who is responsible for the water network?

Each city council owns their respective reticulation network (i.e. Hutt City Council owns the reticulation network in Lower Hutt). Greater Wellington Regional Council owns the bulk water network and is responsible for the consents to take water from the Waiwhetu Aquifer. Wellington Water manages the entire water network on behalf of its five council owners (Greater Wellington Regional Council, Hutt City Council, Wellington City Council, Porirua City Council and Upper Hutt City Council).

27. Is this just a ploy to permanently chlorinate the water because it’s easier to do?

No. A decision on the permanent chlorination of Lower Hutt’s aquifer water has yet to be made. This decision depends on the result of Wellington Water’s investigations and further discussions between Regional Public Health, Greater Wellington Regional Council, Hutt City Council and Wellington Water. Depending on the outcome of Wellington Water’s investigations, there is a likelihood that a permanent treatment solution will be required at the Waterloo Water Treatment Plant (such as chlorination and ultraviolet light), in line with the treatment standards in place for the rest of the metropolitan Wellington.

28. What are total coliforms and why are they a concern?

Total coliforms refer to a group of 16 different types of bacteria. These bacteria are found in soil, vegetation, animal waste and human sewage and many are not harmful.

Total coliforms can be an indicator of the existence of a potential pathway for contamination of the aquifer. This is being investigated.

29. I have a private bore. Is it safe to drink from it?

No, we recommend that you do not drink water taken from a private bore.

30. I’m a home brewer. How does the public water supply differ from the water from the public fountains?

The public water supply does have a higher pH and alkalinity of water compared to the public fountains. Home brewers often dechlorinate with sodium metabisulphate kits.

We have chemical analysis of the water supplied from each of our water treatment plants on our website.