…$1.4 billion strategic upgrade of State Highway 1 from Puhoi to Wellsford…
It would seem to me that this is the cost of the whole Puhoi-Wellsford stretch, and not just the Puhoi-Warkworth first stage. It seems as though the second stage is the more complex (or at least that’s what NZTA are saying), so perhaps it might be realistic to expect the Warkworth-Wellsford bit to be the more costly, particularly as it’s a bit longer that the Puhoi-Warkworth stretch. So let’s just say perhaps an $600 million/$800 million split for the two projects. Now how realistic is that kind of budget? Let’s have a look at the southern portion first, where I have matched up the route diagram in NZTA’s information booklet with Google Earth, to show where the proposed route alignment will go – and the rather large hills that it seems to encounter on the way: Two areas that would seem to be particularly problematic are labelled as “steep slopes”. There’s a rather tricky hairpin corner for the southern one, while for the northern one the current alignment is pretty straight but quite steep (I can’t understand why NZTA would want to shift from that current alignment there actually.)
Now while I am sure that nothing here is impossible, there would be quite significant earthworks required and perhaps even some expensive bridging or tunnelling. Keeping in mind that the Orewa-Puhoi motorway was only 6km long and yet cost $360 million to construct, it may be a tad optimistic to suggest that a 15km motorway could be constructed to a similar standard (and across what appears to be similarly challenging terrain) for not even double the cost.
The Warkworth to Wellsford stage is even trickier, as you can see in the diagram below. The current road winds its way through the “Dome Valley”, which is very hilly terrain and is well forested. I would suspect that some serious tunnelling (or alternatively some pretty horrendous earthworks) will be necessary to bring this section of road to fruition. Which means that $800 million might really be pushing it for this stretch of road. I guess ultimately it comes down to comparing the “per-kilometre” cost of this new road against the Orewa-Puhoi one, which we know cost $360 million for around 6km – so $60 million per kilometre. Of course that included a tunnel, which might have bumped things up a bit, but I think it’s unlikely we would get away with building this 38km road through mountainous terrain without any tunnel. 38 km by $60 million per kilometre comes to a total of nearly $2.3 billion – quite a bit more than the estimated $1.4 billion that NZTA have come up with here.
That’s a pretty expensive upgrade for something that is only used by around 15,000 vehicles a day. A basic Warkworth bypass would be only 5km long, and across pretty flat land. That might cost around $100-150 million, and I suspect would achieve many of the same benefits that this super-expensive holiday highway is meant to provide. Surely that’s a more sensible option?