Green tracking in Rotterdam, Holland

This is a guest post from Ed Clayton

While this post concerns how to develop a transport network that improves water quality, to do this first we need to look at the upcoming water reforms and why reliance on cars and e-vehicles is incompatible with ensuring clean freshwater for future generations.

Aotearoa New Zealand has a new national direction governing water management with the introduction of the Essential Freshwater reforms. This demands immediate improvement to our freshwater systems and the need to bring waterways to a healthy state within a generation. Te Mana o te Wai is the central concept of this and sets out the directions councils need to take to improve waterways. Key to this are the principles of governance and stewardship, where those with authority must prioritize (improving and enhancing where required) the health of waterways now and into the future to ensure the needs of future generations are sustained.

To give effect to Te Mana o te Wai councils must apply the hierarchies of obligation, being the following:

  1. the health and well-being of water;
  2. the health needs of people; and
  3. the social, economic and cultural well-being of people and communities.

Following such directions, it can be reasonably interpreted that councils should take steps to ensure that infrastructure supports Te Mana o te Wai. For transport this means building infrastructure that firstly has low pollutant generation and secondly can actively treat pollutant loads through sequestering contaminants within its structure, ensuring any discharged water is filtered and cleaned before entering the receiving environment.

But our current transport paradigm is inherently polluting. Centering cars and private vehicles in our urban spaces creates swathes of impervious surfaces. This results in “Urban Stream Syndrome”, where paved areas create faster runoff, leading to streams that have higher flood peaks and more erosive power, transport more pollutants and sediment and have fewer species and less complex ecosystems. Compounding this is that the more we drive not only do we require more impervious surfaces to drive on, we increase the number of tyres. And tyres are major sources of heavy metals and microplastics. Tyres are 1-2% zinc oxide by weight, added during vulcanization to make tyres harder wearing and longer lasting. In Auckland zinc is a major contaminant in our marine receiving environments, where too much zinc creates toxic conditions for the little critters that are integral parts of the food web. And tyres also produce microplastics from wear and tear on road surfaces with it being estimated that 10% of all microplastics in the world’s oceans are directly sourced from tyre wear.

None of the above is new. Auckland Council recognizes that roads carrying more than 10,000 vehicles per day are high contaminant generating activities. To mitigate this, such roads should have treatment devices within the corridor that can do a mix of reducing pollution and runoff. Yet retrofitting existing roads is challenging because these treatments devices generally take up more room than is available without a drastic reshaping of the corridor. And changing our vehicle fleet from ICE cars to electric vehicles will not address tyre wear either.

Knowing that we need to improve our waterways and knowing that cars create toxic freshwater environments leads to incompatible outcomes. The requirements of Te Mana o te Wai legislation will place responsibilities on local government that creates conflict with building roads as normal. We need to ask the question “What would urban transport look like if the fundamental requirement was a net-gain in water quality?”

We may have an answer if we can build a light rail network that is integrated with engineered swales and biofiltration devices. Overseas, the use of “lawn tracking” in light rails is extensive in Europe and implemented in a range of other countries including China, the U.S.A and Australia. These tracks incorporate grasses and groundcover plants over infilled soil. Often the only visible parts of the light rail network will be the rails themselves and the overhead wires. Such designs have important benefits. Compared to a standard concrete light rail surface, they reduce the noise associated with light rail vehicle movement, lower urban heat island effects and have lower embedded emissions as there is less concrete used in construction. They improve air quality through helping filter airborne contaminants and help improve community wellbeing through increased visual green space. And most importantly for this discussion, they allow surface water to soak in, thereby removing contaminants and slowing stormwater runoff with studies showing up to 90% of rain falling within the rail corridor soaking in and being used by the plants. Yet these tracks are not designed with water quality outcomes as a priority. Usually, lawn tracks are built to delineate the light rail lines, stop cars from using them and provide aesthetic quality to local areas.

Green tracks in Barcelona, Spain (left) and Grenoble, France (right)

While the final alignment of Auckland light rail is yet to be decided, it is likely to go via either Sandringham Road or Dominion Road in the central isthmus before heading to Onehunga and then on to Mangere. This alignment will likely be adjacent to roads carrying between 15,000 and 25,000 vpd, all classified as high contaminant generating activities. In the isthmus, some of it overlies fractured basalt zones where stormwater is directed to soakage (and then to aquifers) or combined stormwater/sewer networks. These soakage systems feed the Meola and Motions Creeks catchments that in turn discharge to coastal areas under permanent swimming bans. Other areas have more standard stormwater systems that discharge directly to urban streams. Treatment for these roads is sporadic at best with gross pollutant traps only at a select few locations (usually not good enough to filter out microplastics and particulate bound contaminants such as zinc). Making a conscious decision to put water quality outcomes first means that we could build light rail with swales and raingardens that can treat all of the runoff from adjacent road surfaces.

How this might look is similar to the photos of overseas examples but with specific engineered soils designed to infiltrate and treat contaminants. Cross sections would be altered to drain water from road surfaces to a center running light rail line. Effective treatment trains would consist of vegetated swales for pre-treatment before discharge to raingardens, removing sediment in swales and ensuring efficient infiltration in the raingardens. Native plants could be used to provide a rough surface texture that slows water movement, keeping water visible at the surface when it rains and providing food for bees and pollinators when dry.  In areas where road stormwater discharges to streams and marine areas, we could remove contaminants generated from tyres. Where possible, clean water would soak to the aquifers below in much the same way as it does now, but at slower and more manageable rates. In places where the corridor has a wide margin, such as the section between Mt Roskill and Onehunga running adjacent to the motorway, trees could be planted to create a linear forest. We know that climate change is likely to deliver more extreme heat events that impact on rail systems, trees can create a more consistent microclimate that shade and protect the infrastructure.

As an example, to treat the 4.9 km stretch of Dominion Road between the two proposed stations at Mt Roskill Junction and Dominion Road Junction (see the proposed Dominion Road route map), only 1500 m of swales and 150 m of raingardens would be needed (assuming treatment efficiencies as described in Auckland Council’s GD01 document). And these would not be needed in a continuous stretch, rather short sections of treatment could be targeted at suitable areas with enough hard space in between for stations, vehicle crossings and intersections (although let’s face it, more is better!).

Possible raingarden design, Jellicoe St Auckland (left) and a vegetated swale example from Seattle (right)

We could build such a system to tie into a revitalized Queen Street that has been returned to the Waihorotiu, making a green and blue space that, if extended to additional parts of the proposed light rail line, created a stunning biophilic linear transport network from the city center to Mangere.

So how can we make this happen? Currently the Auckland Light Rail Establishment Unit is beginning to consult with the public. What this entails is not clear as well-deserved criticism has emphasized already. We may only have 6-months to seize this opportunity to create a sustainable light rail network that can achieve Te Mana o te Wai. This could be the example we need to put our freshwater systems first when we plan infrastructure. And it must be part of an urban design process that addresses not just the light rail line but the adjacent land use too. At a personal level these ideas need to be communicated as widely as possible so spread and share this post on social media. Tāmaki Makarau deserves great public transport. Let’s make it happen.

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  1. +1,000. Great to read a positive forward thinking post rather than another sad diatribe on AT’s woeful performance. I hope these ideas prevail.

    1. Agree 1000%, what a great and inspiring post.

      And of course the proportion of positive, forward-looking posts will rise as councils and transport agencies rapidly shift their line of travel and show what’s possible.

      You know, like a feedback loop (of the kind we’re witnessing with chaotic climate events) but the good sort.

      Anything is possible. Heck, everything has to be possible. Especially now that we can see what happens with runoff when it has nowhere else to run.

  2. As local and central government allocates large amount to the three waters, a better investment would be in strategies to reduce storm water from runoff (with light rail and pervious surfaces), sewage by supporting compost toilets, and fresh water with rain water collection tanks. A sympoosium is being held in Wellington next Monday, supported by Greater wellington regional council

    1. Some years ago Auckland Council was actively discouraging rain water collection tanks. When the water crisis struck last year I believe that they changed their stance.
      I too, would be interested in the outcomes from the symposium.

      Great article, Thanks Ed!

  3. If you live on Dominion Road you will need to buy a four wheel drive so you can drive across the grass when you turn right into or out of your driveway.

    1. miffy, I wouldn’t think there will right turns out of private driveways across a light rail system (or any other rapid, frequent, service). They just wouldn’t be practical.
      More likely you would turn left and use the road network to get to the nearest intersection with a right turn signal.

        1. How else would you do it? Let’s slow down rail vehicles because people are sore about not being able to turn right

        2. Right turning onto or off busy arterials is craziness anyway. The medians might have been alright when traffic volumes were lower in the 80s, but now its just a free for all encouraging people to dash across multiple lanes without taking the time to look for smaller vehicles. Most of the main routes in the isthmus for example should absolutely already have a solid median banning right turns.

          Like speed cameras, It might not be popular, but it absolutely would be practical. Far more practical than today. U turns for smaller vehicles at lights. Large truck and trailer units dont really need any encouragement to be in urban areas, and if they are, usually (or should) follow pre-determined routes to and from job sites.

        3. No right turns, left in left out like any light rail corridor in the world, and most main roads for that matter.

          If you want to turn right that isn’t at a set of lights, you drive to the next set of lights to make a u turn with the right turn phase.

        4. This assumes that those people living along the route will still want to drive their single occupancy car, instead of taking the LRT

      1. Honestly getting rid of most of the uncontrolled right turns is one of the big advantages.
        I cannot tell you how many times I’ve almost been hit from someone rushing to cross multiple lanes of traffic turning right onto or off an arterial.

        Adding a couple more sets of lights along the arterials to break up the distance between crossings and right turns would help a lot. Decent signal preemption would mean its not a problem for light rail vehicles.

  4. This is a great idea. The best thing is that this technology isn’t even new; it already exists and is successful. It’s simply a case of specifying it in Auckland. Ok, maybe not “simply” but it’s certainly a great way to deliver a cooler, better-draining, more attractive streetscape. Imagine something like Twin Oak Drive in Cornwall Park, but with tramlines. Now imagine avenues like this throughout Auckland.,174.787465,3a,75y,198.16h,84.63t/data=!3m7!1e1!3m5!1sto35F_3FHeeR9-r0epMbyg!2e0!!7i16384!8i8192

  5. If you turn a berm into a creek (Swale) cars won’t be able to park on them. It wouldn’t be toddler friendly though. We used to have creeks instead of gutters back in the day on our street in Christchurch. The local kids used to catch frogs and tadpoles. Back to the future. I love the grassed rail tracks though.

    1. I remember all the old Christchurch suburbs (Knowles Street in St Albans where my grandmother lived) used to have grass and trees planted on the verge of the road with a gutter between this verge and the footpath. Water would first run off the road surface onto the grass and soak in. Any remaining surface water would be taken by the gutter.

      Now those grass verges have been sealed over – presumably to provide on street parking. You can still see them in the pattern of the metalled seal. A huge lost opportunity. Now CCC have installed street side ‘rain gardens’ that don’t have a connection to the road surface except through a bubble up drain – this is better than nothing… but I regret the loss of this large grassed road surface.

      Another consequence is that effectively these roads got wider and road speed increased. In Wade Street, Addington you can see the loss of the verges have created a crazy wide road which has the highest local speeds (4 to 7 km/h higher) compared to the other side streets.
      (source: )

      I’d like to see more vegetated sections of roads – whether for light rail or road level rain gardens / pedestrian bump outs / parking dividers / street tree gratings / median strips / round-abouts – too often engineers engineer gutters and hard surfaces where it would be cheaper and more effective to take a softer approach.

      1. Heard that AT is requiring new develop to have rain gardens or street trees to prevent berm parking

        1. Lol. Funny. They could just enforce! Took more photos today of all the muddy damage being done.

  6. A street level rail track would use sleepers and low amounts of concrete.
    An underground metro line would require a channel about 6m wide with a roof. And a very large quantity of high emissions concrete.
    About 4500 cubic meters of concrete for each kilometre of line.
    Sadly AT always goes for the option that uses the most amount of concrete.

    1. Good point JFamilton – gotta hope those material costs and trade-offs are very very clear in the minds of the light rail establishment unit – and communicated to the public as well.

      1. Concrete needs lots of water and produces lots of highly alkaline run off – aspecially as AT just love their exposed aggregate footpaths. The alkaline run off is extremely bad for the Harbour- no matter how careful you are, there will be pollution.

        1. Need to start adding sulphur back into fuels to bring the acid rain in to balance it all out

  7. Such a timely read, in the wake of wet weather events here and all over the world! So many alarming images of cars swamped, stranded, bobbing along, or tumbled on end in a wall of debris. A river of metaphors, you might say.

    Even without climate-change in the picture, it’s clear we need to “green” our streets to reduce the pollutants pouring into our streams and beaches. The post makes a great case that on-street light rail could be a high-profile demonstration project on a major corridor or two.

    And what about all the rest of our roading? This line is very familiar to anyone advocating for sustainable light transport:

    “Yet retrofitting existing roads is challenging because these treatment devices generally take up more room than is available without a drastic reshaping of the corridor.”

    Drastic, or just the path we need to take? The average Auckland arterial would surely have plenty of space for swales *and* bike lanes if it didn’t have to allow for parking along both sides, or multiple traffic lanes in each direction…

    1. Thanks Jolisa, agree we need to take action somehow! How we prioritise road space needs urgent reconsideration – roads are public space and we need to balance multiple requirements in the limited area we have

  8. Agreed. We should take opportunities to green our city.

    A concerns is the maintenance cost of lawn mowing the track. Who would like to pay for it? Council or AT?

    1. Thanks Kelvin, you’re right that it would require maintenance/mowing. Hopefully any design would incorporate native low maintenace ground cover planting to reduce this to a minimum

  9. This was an awesome read. I really hope that the design team can incorporate this. Even if they can’t get the 1500m, at least some local pockets would make a huge difference for stormwater and microclimate.

  10. Concrete needs lots of water and produces lots of highly alkaline run off – aspecially as AT just love their exposed aggregate footpaths. The alkaline run off is extremely bad for the Harbour- no matter how careful you are, there will be pollution.

  11. Good article. Nz is many years behind, but it’s never too late.
    Something else we need to get our head around is green public places, rather than continuing with seas of hard surfaces like Britomart Place. concrete

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