Somewhat hidden as an addendum to the Unitary Plan is information about where and how Auckland will sprawl over the next 30 years to accommodate the 160,000 dwellings (larger than Wellington or Christchurch) planned for outside the current urban limits. There are three main greenfield areas where the bulk of this growth will be located – the south, the northwest and the north.
In the south, there are a number of different options being looked at for where growth could occur – an expansion of options presented late last year. Here’s the most recent range of options being looked at: Perhaps the most interesting addition to this map from its previous version is what I’ve highlighted in red – a connection between Karaka and Weymouth. This is the first time we’ve seen this connection in any of the Council’s plans – it doesn’t come up in the transport network map in the Auckland Plan or the Integrated Transport Programme.
The main reason for the inclusion of the possible future project in the maps seems to be a few paragraphs in the engagement report about the earlier options, which highlight feedback from Auckland Transport and NZTA:
Preliminary feedback from Auckland Transport (AT) and the New Zealand Transport Agency (NZTA) highlights some key concerns about the impact of growth on the function of the transport network (particularly State Highway 1) in the southern area. AT and NZTA recognise the need for significant areas of greenfield development and recognise that a significant amount of transport investment will be required to support this growth. Locating and sequencing growth in a way that promotes employment self‐sufficiency, makes best use of existing infrastructure where spare capacity exists, encourages the use public transport, discourages long distance car journeys and avoids attracting local trips onto strategic transport routes (i.e. SH1) is encouraged by AT and NZTA. AT and NZTA are particularly interested in mechanisms to control the release of land for development so that it can be linked with the provision of transport infrastructure.
Preliminary transport modelling by AT and NZTA of the residential and employment growth proposed shows substantial congestion on SH1, SH22, Hingaia Road and at Drury, even with Mill Road and rail network upgrades and greater public transport trip share and local employment rates. This would cause significant trip suppression from congestion and impact on the inter‐regional connection and freight corridor functions. In order to retain the functionality of State Highway 1, a major new north-south corridor (most likely a Karaka to Weymouth bridge connection) will be needed to accommodate the levels of growth proposed for the south. While areas east of SH1, close to Pukekohe and close to existing infrastructure of the rail network are preferred to more distant areas, it is likely that the need for additional transport connections will remain the same no matter where the RUB is located.
In a way this result is unsurprising. Planning for so much growth to the south of Drury, when the natural landform of the harbour inlets creates a number of bottlenecks is always going to result in huge pressure on the existing routes across those bottlenecks and increase demand for additional links. As the feedback summary above notes, the main issue seems to be having most growth to the west of State Highway 1 whereas the additional planned Mill Road corridor is to the east of the motorway. And while it is advantageous and utterly essential to have the railway running right through the middle of the growth area, the sheer scale of growth seems like it overwhelms the transport network – creating pressure for this new connection.
Of course, such a link would hardly be cheap. Let’s take a look at just the bridge crossing itself – which seems most likely to follow roughly the alignment shown below:That is one pretty long bridge we’re talking about here – even if a small amount of the southern end could be constructed as a causeway. If you push the bridge to the next landing point to the southeast (to keep a straighter road) then it’s about 1.2 km in length – longer than the Auckland Harbour Bridge!
In addition to this, the road would need to be linked back to the existing road network at both ends in a sensible way. The earlier map suggested on the southern side this would be around the corner of SH22 and Glenbrook Road – resulting in over 9 km of new road/expressway/motorway needing to be built through to the southern abutment:
At the northern end it seems likely the existing roads would need to be widened – both Weymouth Road and Roscommon Road. For Weymouth Road in particular, which is currently a pretty quiet road serving a pretty quiet local community, the impact of the widening and the vast increase in traffic flows would be huge. Looking at the aerials it seems like widening would be required in the area shown below at the very least:
Fortunately along the western side of Weymouth Road there seems quite a large setback, so the widening would be possible without having to acquire a huge number of properties (looks like this connection has been planned for a very long time!) Even so you’re probably looking at a lot of cost and certainly a lot of impact on the local community as it seems likely this would be a very busy road. An earlier study, with lower growth projections, showed that the bridge would be used by a very large number of vehicles per day.
The issue of this bridge highlights the conundrums which occur when you plan for so much growth through urban sprawl. Don’t build this bridge and State Highway 1 is likely to become increasingly clogged up, unable to perform its important inter-regional connection role. Roads like State Highway 22 – which really needs to change its function to more of an urban arterial over time – would be so incredibly busy the road engineers will end up wanting it to be six or eight lanes wide. The transport network as a whole would also not be very resilient – extremely vulnerable at pinch points around Drury and Takanini.
But build the bridge and for a start you have the simply massive cost (my rough guess is that the whole thing including southern and northern approaches would probably be close to a billion dollars, as in 2006 it was costed at $650 million. You then have the potential environmental impact on what seems to be a fairly sensitive environment – from reading through other specialist input on the growth options in the area – which may curtail attempts to put any of the bridge onto a causeway to save costs. Then you have the community impact on Weymouth as their quiet little peninsula will end up having a hugely widened and massively busy expressway right through the middle of it. And then there’s the question of where all this traffic actually goes. Straight onto State Highway 20 to clog that motorway up? Back across to State Highway 1 to clog it up again? Inevitably with road building it seems like we find ourselves “shifting the problem” rather than solving it.
I struggle to see the benefits of the Karaka-Weymouth connection outweighing its costs – the financial, environmental and social costs. But if the level of growth in the south is dependent upon having this connection built does that mean the growth numbers need to be revisited if the ‘powers to be’ decide they really don’t want to see this project happen? That seems like the big elephant in the room question that needs to be answered.