What's polluting our urban harbours and streams?

Friday, 5 May 2017

Friends of Owhiro Stream co-ordinator Martin Payne says restoring urban streams requires a dual approach - donning gumboots and gardening gloves to clean and replant, and a suit and tie for resource consent hearings, to oppose contaminants entering waterways.

The Environment Ministry's landmark Our Fresh Water 2017 report concluded New Zealand's most degraded streams were in urban areas. Nikki Macdonald investigates the state of the Wellington region's streams and harbours, and what's ailing them._

Owhiro Bay resident Jane Poata found a dead eel in the polluted Owhiro Stream. Scientists have also found snails with deformed shells.

From the creek mouth, the plume of brown pushes all the way across Owhiro Bay, dumping its toxic filth straight into the capital's Taputeranga Marine Reserve.

Upstream, past the junked plastic crate and garden hose unfurled like a sea snake along the creek bed, two young apple trees are heavy with rosy fruit. Their owner is now weighing up whether they're safe to eat, their roots diving deep into the contaminated orange sludge that's been periodically pulsing down from the T&T landfill upstream since November.

The landfill-contaminated Owhiro Stream, just before it meets Taputeranga Marine Reserve, on Wellington's South Coast.

The creek's resident eels have names and dedicated feeders. The skinny elvers have disappeared but MoFo is still there. Another old-timer was found dead in the creek bed a few weeks earlier.

Upstream further still, before the dead gull, Martin Payne and 60 other volunteers are cleaning up the stream's litter-strewn banks. Over two hours and 300m of stream, they remove 120kg of rubbish. About half is polystyrene and soft plastics - shopping bags washed down from the city council landfill, caught in the same branches where a juvenile shag perches.

While the water upstream of T&T landfill is clear, downstream the creek is muddy and brown. Researchers found 80 per cent fewer macroinvertebrates just below the landfill site.

Payne and his Friends of Owhiro Stream team are among thousands of weekend warriors nationwide, who give up their time and energy cleaning and replanting scrappy little urban streams. They might not look like much, but they're often spawning grounds for threatened native fish and conduits for contaminants that end up in harbours and estuaries.

But gumboots and gardening gloves are only a small part of the solution. The health of a stream depends not just on the habitat around it, but on what's going into the water coursing through it.

Resource management scientist Juliet Milne talks about the impacts of stormwater contamination. For more mini-docos about Porirua Harbour, see livingwatersdoco.co.nz. First published May 2017.

Payne's an electrical engineer by training. 'I haven't been doing so much of that lately,' he laughs. He estimates the streamcare group collectively invests well over 1000 hours a year. But that's not all potting out plants, because when the stream is full of toxic landfill leachate that might as well be for nothing.

'It's a mix of physical restoration work and then we put our suits on to go to resource consent hearings. It's only when you have those two things together that you can actually make progress.'

CHEMICAL CONTAMINATION

A dead gull on the banks of the contaminated Owhiro Stream

Owhiro Stream is a perfect microcosm of the pressures making water quality in urban streams worse than their much-talked-about rural neighbours. Rural waterways have hogged the headlines, because of their rapid and alarming decline in the face of nutrient overload from intensified farming, which leads to rivers and lakes choked with algae.

But urban streams and harbours are also sick - smothered in sediment running off pasture, forestry, roadworks and bare-earth subdivisions; putrid with ammonia and sewage leaking from ageing and cracked wastewater pipes; contaminated with metals washing off impermeable landscapes at levels so high they're toxic even without heavy rain runoff.

A new report assessing the ecological impact of the T&T landfill contamination suggests authorities have known about the problem for five years.

Greater Wellington Regional Council last year trialled fish counts at seven randomly selected stream sites around the region. Wairarapa's Waipoua River, just below the Tararua Range, clocked in with 177 fish from seven different species, including eight endangered longfin eels. In Stokes Valley Stream and Masterton's Opaki Stream, however, researchers failed to find a single fish.

Freshwater scientist Dr Mike Joy meets the creatures living in urban streams and talks about the threats to their habitat. For more mini-docos about Porirua Harbour, see livingwatersdoco.co.nz

The most common chemical contaminants running through urban streams and into harbours are copper and zinc, picked up by stormwater as it sloshes over hard city surfaces.

Latest monitoring found Karori Stream at Makara Mountain Bike Park and Waiwhetu Stream had ongoing zinc levels exceeding toxicity guidelines. However, an earlier more comprehensive report found half of Wellington streams had acute toxic copper or zinc levels, even after minor rainfall.

Zinc comes from galvanised iron roofs and car tyres; copper from the wear and tear of brake pads. Both consistently high levels, and acute rainwater spikes, can be toxic to stream and marine life. And even if they survive, their growth can be affected.

A PhD thesis examining the impact of metal contamination on kina larvae, by Victoria University student Agnes Mireille Rouchon, found even low copper concentrations stunted growth, made them up to four times more likely to die in subsequent toxic spikes and could impair later spawning.

Porirua Harbour Trust chairman Grant Baker wants less talk and more action to improve Porirua's nationally significant estuary habitat

And then there are the legacy contaminants - Wellington Harbour's industrial history is written in its sediments, a constant reminder that what goes into streams today can affect harbour health for decades.

In the Porirua Harbour catchment, earthworks make up just 1 per cent of land area, but account for 24 per cent of sediment entering the harbour.

Pesticide DDT was banned in urban areas in 1989, almost 30 years ago. Yet all but one sample site in Wellington Harbour exceed early warning levels for DDT and mercury, both of which bioaccumulate - increasing in concentration up the food chain to high levels in large, long-lived species such as dolphins and birds of prey. Lead is the only historical contaminant that appears to be reducing.

Leigh Stevens, of Wriggle Coastal Management, says Porirua Harbour sediment is becoming muddier, reducing the amount of life within it.

Greater Wellington marine scientist Megan Oliver says metal contamination risks removing sensitive species and leaving only hardened, invasive species - 'the rats and pigeons of the marine world'. That in turn affects the whole food chain.

The shallow-sloping flats of estuaries make great sinks for contamination

'In any ecosystem you need biodiversity. Every organism has a role to play, whether it's waste removal, or converting one product into another. That's also true of streams and harbours.'

The Hutt Valley's Waiwhetu Stream was once the country's most polluted waterway. In 2009. the regional council spent $6 million removing a toxic sludge - remnant of the area's industrial past. However, its water quality remains 'poor' and zinc levels exceed toxic warning levels. It's also the sink for the Hutt Valley's sewage overflow when its Seaview plant can't cope in heavy rain.

And then there are the careless homeowners who wash their paint brushes in drains that feed into stormwater, or use toxic pesticides and detergents without thinking about where they'll end up.

In the case of Owhiro Stream, the contamination source is the T&T construction landfill. Greater Wellington has acknowledged the discharge breaches the landfill's consent, and says it's working with T&T to fix it.

But Payne says that, while the problem has got much worse since November, he's been complaining about it since 2013. The latest monitoring report identifies 'spikes' in contaminant concentrations as far back as January 2012, with 'significant adverse effects' on stream life.

Researchers found an 80 per cent reduction in macroinvertebrates such as worms and koura just below the T&T discharge, and downstream snails are an orangey colour, with munted shells.

GW environmental regulation manager Al Cross says T&T's resource consent requires it to construct a stormwater diversion system in the final stages of the landfill, which have not yet been reached. The 2012 contamination incident did spur attempts to accelerate that work, but a design change required an additional consent and the approval of Wellington City Council, which part-owns the land and controls drainage.

'If we knew then what we know now we could have pushed harder,' Cross concedes.

T&T declined to comment, saying all the relevant information was on the regional council's website.

Payne is also concerned about Wellington City Council's plans to extend its southern landfill, which would engulf a section of an Owhiro Stream tributary.

The current landfill area only has eight years of useful life remaining. It has put its extension application on hold following the stream group's opposition. Payne wants to see efforts to reduce waste, rather than simply appropriating more space to accommodate it.

Councillor Iona Pannett agrees. She also wants to see plastic bags outlawed - the council has spent $20,000 trying to prevent rubbish blowing away, but acknowledges its landfill is the likely source of Payne's 60kg of collected plastic and polystyrene trash.

'We need to look at the whole waste system,' Pannett says. 'We are so far behind on this in New Zealand.'

Sediment smothers streambeds, obliterating fish habitat. In this extreme example, a structure in Wainui Stream is completely submerged within seven years. PHOTO: SUPPLIED

SMOTHERING SEDIMENT

In 2007, Niwa marine ecologist Kura Paul-Burke mapped the mussel beds in the Bay of Plenty's Ohiwa Harbour. 'It was fantastic', she recalls - a 2km continuous stretch of mussels, numbering an estimated 112 million.

In 2009 she put on her dive gear and went down again. The usually grey harbour bed was alive with a carpet of orange sea stars. Pretty, she thought, until she saw the devastation.

'Behind them was this distinct line - mussels ahead and dead shells behind them.'

She estimated the mussel numbers had dropped to 16 million, with 58 per cent of the area of the original bed wiped out.

In 2016, she went down again. The visibility was so bad she needed a torch to see and had to wipe the silt from mussel-shaped objects to check they were actually shellfish. In just 10 years the mussel count had fallen from 112 million to 480,000 and Paul-Burke has no doubt of the cause.

'Humans - our activities. Forestry, farming, horticulture, people building houses, roads - all of that gets washed into our harbour.'

Sediment is also the biggest issue facing Porirua Harbour and its nationally significant estuary habitat. Unlike Ohiwa Harbour, its cockle beds had been recovering - until last year. The 2016 cockle count was down, although it's not yet clear exactly what that means.

But the harbour is far from out of the woods.

Porirua Harbour Trust chairman Grant Baker stands at the mouth of Porirua Stream, where it empties into the Onepoto arm of Porirua Harbour.

'The quality of the harbour is totally dependent on what is coming down from the catchment,' he says.

All these hard surfaces - the concrete stream sides and piped outlets, prevent fish travelling upstream and coming out onto the banks to spawn.

On the ridge beyond the highway, a digger bucket swings as it munches at the other side of the hill, clearing sections for the Aotea subdivision. On the stream-side of the hill, workers are planting to limit erosion.

On the harbour's Pauatahanui Inlet side, behind Duck Creek, roads give way to bare clay as another new subdivision goes in. Further back still, satellite photos show denuded hilltops where pine trees are being harvested.

What you can't see is the Transmission Gully roadworks. Even with their 'state of the art' sediment control, they're expected to dump up to 2500 tonnes a year into the harbour - 7 per cent of its annual sediment load.

While pasture is the biggest contributor to sediment running into Porirua Harbour, earthworks have the most disproportionate impact, making up just 1 per cent of the catchment but 24 per cent of sedimentation.

Marine ecologist Leigh Stevens, from Wriggle Coastal Management, has been regularly surveying Porirua Harbour, which he says is becoming muddier.

Fine muds affect water clarity, preventing sunlight getting through the water, killing off critical sea-grass beds.

'From an ecological perspective that's bad, because they help trap those fine sediments and improve water clarity. So you get a double whammy.'

Muds also affect the creatures living within the estuary beds, filling in the spaces so oxygen can't penetrate. You lose sensitive species and there's less liveable habitat, so fewer critters.

'And those are the things birds and fish live on. So it hammers it that way.'

While cockle numbers in Porirua Harbour are holding up, they're getting smaller, as they have to use more energy filtering sediment as they feed.

Around the country, estuaries are in serious trouble, due to algal choking caused by nutrient overload (usually from intensive farming), Stevens says. New River and Jacobs River estuaries in Southland are among the worst.

'There's no oxygen in the sediments. They're black, they're muddy, they stink of sulphides and there's just nothing living in them. They're toxic.'

Sediment also chokes stream life, says freshwater ecologist Mike Joy. By radio-tagging native bullies and galaxiids he discovered they spent 90 per cent of their time in the spaces between rocks and boulders in healthy streams. Smothering those rocks in sediment is like forcing a building of apartment dwellers to live only on the roof.

Sediment monitoring often misses the point, as it focuses on cloudiness, which measures suspended sediment rather than what is deposited on the stream bed, Joy says.

'It's a bit like if the house is on fire and there's a whole lot of smoke but you can get down low and get out of it and then hopefully it blows away and you're alright. It's what gets left behind that they can't handle. That's when the habitat gets lost.'

Joy wants to see stricter monitoring of earthworks to improve sediment retention.

It's five years since the Porirua Harbour Strategy was introduced to improve the harbour's health. Baker says there's been plenty of planning, but little tangible progress.

'Show us something that has actually improved. Tell us what change you are making. Because we don't believe there's any evidence of change.'

However, Porirua Harbour Strategy co-ordinator Keith Calder defends the strategy's record. A huge amount of work is going on behind the scenes and it was always expected to take 10 years to make meaningful change, he says.

'We're getting all the bits of the jigsaw puzzle in place.'

Progress so far includes special recognition of the harbour in regional planning documents, new trade waste, wastewater and stormwater bylaws and a new land management officer, employed to work on sediment reduction.

They've set up school education programmes and plan to label drains running straight to the sea.

Greater Wellington Regional Council has also set up a whaitua committee - the second of five catchment-based groups of local people who will decide how water is to be managed in their area. Committees for the Wellington Harbour and Hutt Valley, Kapiti Coast and Wairarapa Coast are yet to be established.

As part of the whaitua process, scientists up and down the country are modelling possibilities for different land uses, business as usual and water-sensitive design.

Progress has been hampered, however, by four major floods in the past two years, which will inevitably blow out sediment loads. The big question, Calder says, is is this the new normal?

A juvenile shag perches on an outfall running into Owhiro Stream. PHOTO: NIKKI MACDONALD/FAIRFAX NZ

SEWAGE SEEP AND OVERFLOW

Back at Owhiro Bay, there's a sign warning against swimming after heavy rain. Like many waterways around the region, Owhiro Stream swells with stormwater and faecal matter after rain, contributing to the bay's D grade for swimming.

Wellington City Council disposes of sewage sludge at the Happy Valley landfill, but they're adamant that's not the source of faecal contamination. Which leaves the common culprit - leakage from cracked and ageing wastewater pipes and illegal connections pumping toilet water into stormwater drains, which bleed out into streams and harbours.

Mike Joy says wastewater infrastructure around the country is 'stuffed' and councils aren't spending enough on upgrades. Porirua's treatment plant overflowed 17 times last year, discharging partially treated sewage into the sea west of Titahi Bay.

Wellington Water, which manages sewerage, water and stormwater in Wellington, Hutt Valley and Porirua, says the Porirua plant is its oldest. A planned upgrade by 2020 will help reduce wet weather overflows.

In the glow of rose-tinted nostalgia, let's not forget how far we've come. Until 1892, raw sewage ran in open drains from Wellington city to the harbour, taking with it 548 lives - the majority infants - from cholera, typhoid and other infectious diseases.

Progress is as much about attitudes as enforcement, says Greater Wellington's Megan Oliver.

'Much of this is about social change; people taking an interest; being responsible for what they want to see in their environment, what they want to do in it.'

THE POLLUTERS

Greater Wellington Regional Council controls 689 resource consents to discharge potential contaminants either directly to waterways, or to land in a way which might affect waterways.

They include: GW staff using pesticides to control aquatic weed; district councils discharging sewage to rivers or the sea in heavy rainfall, industries such as Winstone Aggregates, road builders and landfills discharging stormwater contaminated with sediment and chemicals; and farms discharging effluent to land.

In 2015 and 2016, there were 278 incidents of non-compliance with consents, ranging from farm overstocking to excessive sediment discharge.

Over the same period, there were 707 reported incidents of water contamination, resulting in:

▪ 44 infringement notices

▪ 10 abatement notices

▪ 88 formal warnings

▪ 57 advisory notices

▪ 332 advice letters

Reported incidents included:

▪ Red dye in a stream in Fraser Park (no enforcement action)

▪ GWRC workers spraying chemicals into Kuripuni Stream, where people collect cress (advice letter sent)

▪ Wet cement dumped into Kaiwharawhara Stream (formal warning issued)

▪ 22 dead eels, after a mulch pile caught fire and the run-off spilt into Waikanae's Waimeha Stream (formal warning issued)

▪ A Masterton portaloo tipped over, spilling into a stream (no enforcement action)

▪ White paint dumped into Masterton's Solway Stream. Had happened before, resulting in death of neighbouring sheep (no enforcement action)

▪ Bright red water gushing from stormwater drains at Island Bay Beach (formal warning)

▪ Decapitated goat in Pauatahanui Inlet (no enforcement action)

Health warning signs are erected every time sewage is discharged into the sea from Wellington's Moa Point treatment plant. PHOTO: ROBERT KITCHIN/FAIRFAX NZ

SEWAGE CONTAMINATION FROM TREATMENT PLANT OVERFLOWS

During heavy rain, the Moa Point, Porirua and Seaview treatment plants can't cope with the water volumes, so discharge sewage to rivers or the sea. Kapiti District Council, however, has storm basins, which store untreated wastewater during heavy rain, so it can be treated after the storm has passed.

While fully treated sewage is technically safe, authorities warn against swimming nearby for 48 hours.

DISCHARGES FROM PORIRUA TREATMENT PLANT TO THE SEA, WEST OF TITAHI BAY

2016/17 - 17 discharges of partially treated sewage, totalling 30,877 cubic metres

2015/16 - 19 discharges, totalling 44,474 cubic metres

Wellington Water says Porirua is its oldest treatment plant. It underwent an upgrade in March 2016 and another upgrade, due to be completed by 2020, will help reduce heavy rain overflows.

DISCHARGES FROM MOA POINT TREATMENT PLANT TO OUTER LYALL BAY

2016/17 - 7 discharges, totalling 852,071 cubic metres, of which 94,333 cubic metres was only partially treated

2015/16 - 1 discharge of 20,748 cubic metres, of which 1477 cubic metres was only partially treated

Wellington City Council says it is investigating options to improve the city's sewerage system, including increasing the Moa Point plant's capacity and increasing sewerage system storage to reduce peak flows.

DISCHARGES FROM SEAVIEW TREATMENT PLANT TO WAIWHETU STREAM

2016/17 - 13 discharges of fully-treated sewage, totalling 777,072 cubic metres (488,889 of that was for maintenance rather than rain)

2015/16 - 2 discharges, totalling 14,898 cubic metres.