In order to build the houses we need to combat this housing crisis one the major prerequisites of this is infrastructure, without it, the development couldn’t succeed. This post is about a highly but often forgotten element of infrastructure Three Waters – Water Supply, Wastewater & Stormwater focusing in this part on Wastewater.

Central Interceptor Video

Watercare defines wastewater in simple terms as “Wastewater, also known as ‘sewage’, is 99.97 percent water as the majority comes from showers, baths, and washing machines. The remainder includes organic matter such as human waste and food scraps, fats, oil and grease, and debris such as sand, grit, and plastic. Wastewater can also include such things as household chemicals, paint, and pharmaceuticals that can be harmful to our health and to our harbours and waterways”

In the current Metropolitan Area Watercare has wastewater treatment plants at Rosedale, Māngere, Army Bay and Pukekohe. The first major wastewater system built in Auckland was the Orakei Mains in 1914 which was effective at removing wastewater but polluted the waters heavily. The Mangere treatment plant was opened in 1960 (Extended 1980 & Upgraded 2005) alongside the Eastern & Western Interceptors which connect to Mangere treatment plant after opposition was made to the previous 1930s proposal for Browns Island. Later the Southern Interceptor was built in 1965 & the South-West Interceptor in the 1980s. In the North Rosedale treatment plant was opened 1962, with multi-stage upgrades occurring since the 1990s. Hibiscus Coast is served by Army Bay treatment plant which was built 1982 (Upgraded 1998 & 2005). Treatment areas also exist in the non-metropolitan area at Denehurst, Omaha, SnellsAlgies, Helensville, Waiwera, Warkworth, Kawakawa Bay, Bombay, Waiuku, Kingseat, Clarks Beach/Glenbrook/Waiau, Clevedon, Beachlands / Maraetai and Wellsford.

However going forward we will need to make major upgrades to our wastewater system if we are to serve the growth, many of these have been budgeted in the Long Term Plan such as

  1. Central Interceptor; ($944m) a tunnel stretching 13 kilometres from Māngere Wastewater Treatment Plant to Western Springs, which will replace an ageing system and provide additional capacity in central, southern and eastern Auckland. The project will also deliver environmental benefits by reducing the volume of wet weather overflows into Auckland’s harbours by 80 per cent. The project also provides support for the ageing Western Inteceptor tunnel under the Manukau Harbour – 2017 – 2025.
  2. Northern Interceptor Stage 1; ($135m) The complete Northern Interceptor will move the West wastewater to Rosedale from Mangere, as well as provide wastewater infrastructure to the growing North-west taking pressure off the Mangere treatment plant & enabling the North-west development. Stage 1 is a pipeline between Rosedale & Hobsonville – 2015 – 2021.
  3. Northern Interceptor Stage 2; ($102m) This stage runs a pipeline from Hobsonville to Te Atatu diverting wastewater to Rosedale from Swanson, Massey and Glen Eden as well as enabling growth in Redhills, Whenuapai, Kumeu, Huapai and Riverhead. 2022 – 2028
  4. Waterfront Interceptor ($350m) 3.5 km conveyance and storage tunnel from Ponsonby to St Mary’s Bay increases capacity & reduce overflows. Requires Central Interceptor. 2026 – 2035.
  5. Central Interceptor Optimisation Works ($299m) Additional works to maximise investment in Central Interceptor Spine through collector and link sewers maximising the large investment which is the Central Interceptor. 2026 – 2035.
  6. Māngere Wastewater Treatment Plant Upgrade (75m) Needed to provide capacity for growth. 2015 – 2025.
  7. Rosedale Wastewater Treatment Plant upgrade (48m) Needed to provide capacity for growth. 2015 – 2020.
  8. Pukekohe Trunk Sewer and Wastewater Treatment Plant upgrade ($106m) Needed to provide for growth at Pukekohe, Paerata, Tuakau and Pokeno. 2015 – 2025
  9. Pukekohe Wastewater Treatment Plant capacity upgrade ($95m)

These projects are integral if we are to provide for the growth to tackle this housing crisis, however, it is key that an integrated approach is taken to infrastructure where AC/AT/NZTA/Watercare/Panuku/Crown work together on each area as a complete package of Three Waters, Transport, Planning & Community/Social Services to make work & not in isolation of each other.

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38 comments

    1. Drink it?

      Like Raveen Jaduram (chief exec of Watercare) is doing in the picture in yesterday’s Auckland City Harbour News. Loved the resident’s comment: “One of the advantages of living in New Zealand is good quality drinking water made by nature, not by man.” Ha ha. So Waikato River water is preferable to treated sewage?

      The article says the CCO was “looking at the possibility of reusing treated sewage for either human consumption, industry, agriculture or reinjection into the aquifer”.

      I’ve said it before and I’ll say it again, we need to have fingers of agricultural / horticultural / forestry land snaking through the city, fertilised by our own waste. Totally feasible in this day and age, and far less burden on the surrounding countryside and waterways.

    1. “Many of these have been budgeted in the Long Term Plan such as”

      Don’t believe that was LTP Budget.

  1. $2.154b over 20 years…around 100 million a year…I guess thats the 3% increase they served us from 1 July

    1. Wastewater is provided by Watercare so is technically funded by Watercare charges rather than rates.

      Unless you mean Watercare charges increased then apologies

  2. Harriet have you requested the business case for the third main? Radio NZ is reporting the Minister has tried to stop the release.

    1. Such blatant ministerial interference in the availability of public information. Bridges and his office are pretty arrogant with respect to this issue. Not defensible in my view when Kiwirail are happy to release the info…

  3. Excellent to have all this information in one place. Thanks, Harriet.

    When I was studying wastewater, the industrial waste inputs were considered to present a bigger toxic problem than household chemicals. Has the situation changed? I’d like to think industrial waste is being treated before discharge to the extent that it is now the lower load, but that would be a big change from 30 years ago.

    The opportunity to deal more locally with the three waters would be one of the few benefits (to my mind) of greenfields developments. New developments could quite easily separate industrial waste from household waste. If surrounded by treecrops or forestry, there is an opportunity for using the waste – if not toxic – as fertiliser. They could even go so far as to use one of the many treatment options that don’t require mixing of waste with expensive, treated pure water just for the purposes of transportation. Civil engineers haven’t liked multiple local treatment systems historically, but the field has improved so much over the last few decades that more progressive systems need to be a top priority.

    Omaha is a good example of where the entire load is from households. Initiatives to spread the treated sludge on forestry land in the area were resisted by faecaphobes… do you know whether those initiatives had any success? Education of the public about eco-friendlier cleaners and better ways to wash paint brushes won’t ever be perfect, but creating a useful but not quite perfect fertiliser is better than treating all as waste to be landfilled or incinerated at huge cost.

  4. The other important point is the city needs a belt and braces approach to wastewater treatment – as Christchurch found out. The end-of-the road portaloos were heavily despised, and assistance – in the form of workshops on how to build a simple composting toilet – was necessary. In an civil emergency, Auckland needs to be better prepared. Transition Point Chevalier harnessed the expertise of James Bellamy – who advised communities in Christchurch – and ran a workshop on how to make emergency composting toilets. Thanks to the progressive local board for providing funds for this. Ideally, at least one household in every 50 would have the expertise to spread the information if suddenly required.

    1. Heidi do you have anything to support your statements? “as Christchurch found out. The end-of-the road portaloos were heavily despised”

      I can tell you as an essential services worker in Christchurch after both quakes that your opinion is very different to what I saw personally while working there.

      1. No statistics, I’m afraid, Ted.

        The portaloos were probably the best that could be organised quickly, but they had the obvious disadvantage that people had to leave their homes whenever they needed to go to the toilet. For many people, this is impractical – think of the large number of people who need the toilet in the middle of the night, and often they are people who are not in the best of health and strength. Not many people like having to use a public toilet, relying on the personal cleanliness of everyone else. When you have a little child, even a slightly wet or unsanitary portaloo is awful, from personal experience.

        This article refers to the the Christchurch experience:

        http://www.stuff.co.nz/the-press/news/christchurch-earthquake-2011/5393000/Compost-toilets-convenient-in-Chch

        “The feedback on Christchurch’s chemical toilets was that they were “not nice to deal with”, [Bellamy] said.”

        Apart from that I only have the opinion of friends, and knowledge passed onto me by people who attended the Pt Chevalier workshop.

        Again, as Jeff Tumlin said at the talk on Tuesday night: “From Oakland to Auckland…The Insider’s Guide to Changing Your City”

        If you design for women, children and old people, you design for everyone.

  5. Is there any detail available on the proposed “Waterfront Interceptor” Seems the Central Interceptor isn’t actually going to help the situation in the Coxs Bay and the rest of the Inner West much at all?

    Also, many of the houses the houses that have been renovated in the last 10 years or so would have been forced to installed stormwater retention tanks as part of Resource Consent. Is this having an impact or just a delaying tactic for the public infrastructure?

    1. I wonder why would they not just extend the CI along the waterfront? Wouldn’t it be much easier/cost effective to consolidate the two?!!

  6. Between the Central Interceptor, the Waterfront Interceptor, and the “optimization works”, that comes to $1.6b for the inner suburbs alone. How much would it cost to just do the job properly and install separate stormwater pipes?

      1. Also that amount would be entirely funded by rates rather than out of water charges so wouldn’t be quite so hidden in terms of charging.

  7. Is the Whangaparoa discharge at Army Bay still untreated ? The present system is screening only. The Rosedale outfall is off Campbells Bay ( 2.7km) but treatment isnt to the same standard as Mangere

  8. Missed mentioning the small treatment plant on Waiheke which I believe only treats wastewater from the commercial area on Waiheke.

  9. The anti-sprawlers always claim that intensification means less pipes. But given that the Isthmus is about the furthermost point from water treatment and wastewater plants I have never understood their claim.

    1. Tbf fair large chunk of cost is duplication of aging western interceptor under Manukau Harbour and tbh its the older properties that are more the problem more than any new ones.

    2. Dairy Flat and Ponsonby are both 12km from their nearest treatment plant. 10,000 new homes in Ponsonby would only require the trunk to be built.

      1. Of course the trunk to Ponsonby needs to be built through an existing urban area, significantly increasing the cost.

    3. Yes this isthmus is about the furthermost point from water treatment you could build new homes in, except for the southern and northwest growth areas that is.

  10. Interesting that Tuakau and Pokeno are mentioned with Pukekohe waste treatment plant expansion. Pokeno and Tuakau are in the Waikato District. Does the funding for this come from Waikato District?

  11. Many of these projects, e.g. the central interceptor, have nothing to do with population growth and are about maintenance or existing infrastructure being at the end of its life. The western interceptor where it passes under the harbour is stuffed. The central area discharges to sea whenever it rains. The central interceptor will take the load from these areas.
    They should have been budgeted for as part of depreciating the existing assets

    1. These projects are budgeted for and Watercare can afford to pay for them. Watercare in 2016 allowed for $216m in depreciation paid for by current customers.

  12. In that the central city areas seem to have problems with sewerage discharges in periods of heavy rain there appears to be a need for many of the older areas to be eyeballed and those who are discharging storm water into sewers given an ultimatum about separating their flows.

    1. Sewerage pipes used to drain to the sea locally. That’s not a great solution so main pipes that literally intercepted these local pipes were installed. They took the waste away- initially elsewhere to be pumped into the sea and later for further treatment.

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