Wellington Scoop

Pollution alert: the council agrees with some concerns, but disagrees on others

by Nicci Wood
Planning Engineer, Wellington City Council Infrastructure Dept

The Council does not deny that Jim Mikoz has made a considerable contribution to researching and writing about the marine environment. What we are concerned about, though, is Mr Mikoz’ assertions regarding the Council’s operation of its sewage and stormwater networks, including the Moa Point treatment plant.

We do not dispute that urban environments have negative impacts on ‘aquatic receiving environments’ – in laypeople’s terms, streams and the sea.

During heavy rain, parts of the sewerage system cannot cope with heavy flows due to cross-connections from the stormwater system to the sewerage system and vice versa. Sewage and stormwater – including some chemicals and other contaminants – does from time to time end up overflowing to the harbour or South Coast. The situation isn’t ideal. We understand that.

Some of the issues mentioned by Mr Mikoz are inherited from our forefathers. The poorly-designed and relatively primitive Houghton Bay landfill, which operated from 1950 to 1971, has an influence on stormwater quality in the bay.


As Mr Mikoz has shown with his photograph, orange-coloured precipitate sometimes flows from the outfall. A moderately offensive odour can also sometimes be evident on the beach.

The Council is very aware of the leachate. Sampling has shown that the concentrations are generally within acceptable levels (ANZECC, 1992, Water Quality Guidelines for Fresh and Marine Waters). However we totally agree that the leachate pollution is unacceptable and we are working to rectify the situation. This may involve relining and sealing the stormwater pipe under the landfill or connecting it to the sewerage system.

The Council appreciates there are some issues with our wastewater and stormwater networks, and these systems occasionally impinge on water quality in the harbour and around the south coast. However these issues aren’t specific to Wellington. They are common to any urban environment in New Zealand or around the world.

To put it all into perspective, to renew and/or upgrade the sewerage and stormwater networks to further reduce pollution in the harbour and around Wellington’s coast would cost an estimated $1.2 billion. This equates to about $6800 per person in Wellington City. We have to be realistic and pragmatic and agree that such spending on this infrastructure has to be spread out over many years – otherwise the city would go broke.

As a council we also have to balance our spending against other priorities and the interests of a wide audience of ratepayers.

Wellington City has separate sewerage and stormwater drainage systems. However like many other urban areas in New Zealand we have had a problem with the contamination of stormwater with sewage and vice versa. The direct causes of the problem are ‘leaky’ sewers and wet-weather overflows from sewers and pump stations. The underlying causes are the older sewer pipes in our network, illegal cross-connections between sewer and stormwater drains, inflow and infiltration (I&I) and, in some cases, under-capacity sewers and pump stations.

In 1993, the City Council initiated a 15-year, $70 million, programme of investigation, works and monitoring aimed at progressively eliminating sewage pollution from coastal waters. We also spent $170 million on the construction of the sewage treatment plants at Moa Point and South Karori. We also gained 12 resource consents to discharge contaminated stormwater from significant catchments. The consent conditions prescribed a programme of works and monitoring to be implemented over 15 years.


One of the conditions of these consents was to place and maintain signs at the shore at and around the stormwater outfalls to warn the public about swimming or collecting and eating shellfish. The wording on the signs is approved by the Greater Wellington Regional Council. The warning messages are also of a standard used around New Zealand.

Our infrastructure work has already radically improved water quality in the harbour and around the coast.

Our focus is now not only on from microbiological contamination but also on the management of risks associated with contaminated sediment and the heavy metal content of stormwater discharges and their effects on our waterways, the harbour and the sea.

The Council has applied for discharge consents under the Resource Management Act for all stormwater discharges to the coastal marine area. This includes conditions for further investigation of the effects of stormwater on the local marine environment and management of the risks associated with the stormwater discharges.

Mr Mikoz makes much of the presence of chemicals and human diseases transported in sewage. The Moa Point and Karori treatment plants were not constructed to remove these contaminants. They were built principally to remove what the community generally considered to be a far bigger problem – the serious pollution of the harbour and especially the South Coast by human waste.

Let’s be clear here. A cocktail of chemicals – everything from antibiotics and contraceptive based hormones to heavy metals from antiperspirants – ends up in the sewerage system. The Council has little control over what individuals introduce to the wastewater network.

At the moment the discharges of these chemicals such as the endrocrines described by Mr Mikoz are not deemed significant enough by MfE or GWRC to set standards or require the Council to monitor for them or their effects.

In terms of Mr Mikoz’ claims about deformed fish, we’d ask him to hand over any examples so we can work with the likes of NIWA and Ministry of Fisheries to understand how and what has led to the deformities.

Regrding Mr Mikoz’ comments about caustic soda (NaOH) his claims are baseless. Yes, caustic soda is used at Moa Point to help in the odour ‘scrubbing’ process. In laypersons’ terms, it is incorporated into a spraying process designed to mitigate the smell of sewage. It is not used for pH control or for sterilisation or for any other purpose.

In more detailed terms, the caustic soda works with sodium hypochlorite to oxidise and precipitate (‘scrub’) sulphur compounds from the air. In the process the caustic soda is broken down to salt and water. The pH of the scrubber effluent is roughly 8 – very similar to that of water.

About 400 litres of salt and water goes down the Moa Point outfall each day. Moa Point treats about 74 million litres of effluent each day – which tends to put the impact of the caustic soda into perspective. No caustic soda is required to mitigate the wastewater contribution from Taylor Preston. Taylor Preston has its own treatment plant on site which ensures any wastewater leaving the abattoir site meets strict trade waste requirements before entering the sewerage network. These requirements include biological oxygen demand (BOD) and suspended solids.

Regarding Mr Mikoz’ comments about the ‘slick’ or plume discharging from the Moa Point long outfall into Cook Strait, the fact is the ‘slick’ is fresh water coming out of the outfall. Fresh water is less dense than salt water – so in calm conditions it rises to the surface and collects – but the tides quickly dissipate the fresh water. If however there are any visible signs of discolouration please tell us when it happens. If necessary we will investigate.

Mr Mikoz has long expressed concerns about the length – and depth – of the Moa Point outfall. He says the Wellington Recreational Marine Fishers Association has asked that the outfall – which already extends 1800 metres out beyond Lyall Bay and into 22-metre deep water in Cook Strait – be extended to a depth of 50 metres.

He says: “Our request was rubbished.” That is obviously an emotive way of saying that the Council and other agencies don’t think it necessary to spend many millions of dollars to extend the outfall for no apparent benefit. Anyone who remembers the long debate – and the resource consent process – that preceded the construction of Moa Point treatment plant will recall that the length of the outfall and indeed the necessity for a treatment plant at all was central to the debate. Most observers agree that the outfall is of more than adequate length and that Cook Strait’s turbulence generally makes short work of the discharge.

Mr Mikoz also claims there is no life in intertidal zone rock pools on Wellington’s south coast. He says: “If anyone thinks wastewater has no impact, they only have to look for marine life at the Wellington City Council emergency wastewater pipe in Tarakena Bay, between Moa Point and Palmer Head, just around the corner from the boat ramp.” Our response is that the emergency outfall, which in fact is in Lavender Bay, not Tarakena Bay, is very rarely used – and that marine life in the area appears to be thriving. It is certainly in better shape than it was until the late 1990s (the new Moa Point plant opened in 1998) – when the water in the area was coloured a rich brown by milliscreened human excrement.

We make no secret of the fact that the Council does not treat stormwater, including road runoff, in any way. Road runoff is a cocktail of contaminants including sediments, heavy metals and chemicals. The pollutants come from vehicle exhaust, road wear, and compounds deposited on roads as a result of tyre and brake pad wear. They may also come from paint and fuel spills.

We do not dispute Mr Mikoz’ comments regards land runoff poisoning aquatic environments – although ‘poisoning’ may be a little strong a term. Uncontrolled sediments and associated contaminants, toxins and heavy metals are ending up in streams and ultimately the sea, threatening aquatic life. Many potentially toxic chemicals adhere to tiny particles which are then taken up by plankton and benthos animals. In this way, the toxins are concentrated upward within marine food chains. They are also known to accumulate in benthic environments, such as harbour sediments.

To this end the Wellington Harbour Sediment Quality Investigation has been conducted to identify the nature, severity and extent of the contamination of harbour-bed sediments, much of which can be attributed to stormwater. Sampling and analysis was funded by Greater Wellington, Wellington City Council and the Hutt City Council. The work allowed an assessment of the harbour’s sediment quality and benthic community health that will provide a scientific basis for future management response in relation to urban stormwater discharges. The work also enables any changes in sediment quality and benthic community health over time to be detected, thereby allowing the ongoing evaluation of urban stormwater management actions directed at maintaining or enhancing the harbour.

Part of the problem of pollutants in the coastal area is discarded human rubbish, generally plastics. Discarded plastic bags and other forms of plastic waste finish up in the ocean – presenting dangers to wildlife and fisheries. Toxic additives used in the manufacture of plastic materials can leach out into their surroundings when exposed to water.

Wellingtonians need to, individually, pollute less. For this there must be social and political will, together with a major shift in awareness, so more people understand and respect their environment and are less disposed to abusing it.At an operational level, standards, regulations, and national and local government participation is needed. The NZ Coastal Policy Statement is key to this.

The Marine Reserve is another practical means of promoting the values of aquatic ecosystems and addressing ecological and cultural concerns relating to stormwater management.

The Council has worked closely with DOC to progress the Marine Reserve while recognising the importance of the Council’s ability to operate its stormwater and wastewater systems.

There is not just one solution to effective stormwater management and improving water quality. It’s a combined approach that includes preventing the contamination of stormwater flowing into the waterways by sewage or anything else, replacing and maintaining the pipe network, public education and behaviour change.


  1. Jason Christensen, 29. August 2009, 12:29

    Thanks for the article it was very informative. In fact, in some ways it painted a pretty picture. The problem is it’s not all that pretty really is it?

    That article told me that yes, GWRC intend to clean things up, and we’ve come along way since the 1970’s. Sure, that’s a no brainer. I’m happy that some effort is being made.

    Resource consents as based on what information is available, and what guidelines are currently set for tolerances of any one contaminant. Would that not be a fair comment? This being the case, in some situations it is very obvious that lack of knowledge in many of these key areas sets these limits far too high, or assumptions are made on what is deemed a tolerable limit due to a complete lack of knowledge all together. Setting limits on what might be tolerable for humans at any one time does not mean that those limits being consistantly pumped into our marine environment are tolerable to that environment as a whole.

    I absolutely agree that more personal responsibility should be put into creating a communal awareness of how our interactions on our invironment affect it. Many are becoming aware, and it is through such debates as this that that awareness comes about.

    I believe Mr. Mikoz’s concerns outline this issue. I also believe his comments should not be disregarded. This is evident in the comment above regarding land run off. This also includes sediment run off, which doesn’t just pollute, it smothers. Once an area is smothered nothing grows there. The area becomes barren. There is a very obvious example of this at Glenburn Station on the Wairarapa coast where a natural land slip has flowed into a stream and then on into the sea. For several hundred metres in the direction of current flow along this coast a grey sludge can be seen. There is no life there. No paua, crayfish, fish, plants or anything else. It is incredibly destructive.

    Areas that have already been destroyed are the areas where research should be being done to develop avoidance planning and the setting of tolerances in order to prevent man made examples of the above. These should be the guidelines adhered to in order to grant resource consents. Researching areas that are currently healthy or potentially under threat are not areas that should be used as models. They are the areas that must be monitored. What is learned from the areas already severly threatened or destroyed is what should be put in place to avoid it happening where it can be prevented, and often it can.

    “The Council appreciates there are some issues with our wastewater and stormwater networks, and these systems occasionally impinge on water quality in the harbour and around the south coast. However these issues aren’t specific to Wellington. They are common to any urban environment in New Zealand or around the world.”

    Calling upon people to accept that we aren’t the only ones in this country, or the world that discharge waste in this way is a cop out. People have made it clear that they do not want this to happen. We are in effect “crapping in our own nest”, and it’s time to say it is no longer acceptable. We now know better.

    Wellington prides itself on its people, and promotes an educated city. How about we get educated and start to work harder at making our city the first in the world to say we won’t stand for this.

    Let’s clean it up.

  2. Unframe, 16. September 2009, 17:08