Expressways and earthquakes – what if?

Given recent events in Christchurch, it is impossible not to think what the impact would have been in our community had it happened here.

It hasn’t of course but it is distinctly possible at some time in the future. What could happen transport wise, if NZTA has completed construction of the expressway on the route it wants?

Picture if you will, the stretch from the overbridge proposed at Marycrest to the overbridge in Ōtaki. At no point will the expressway, the current State Highway 1 and the railway be more than a hundred metres or so from each other. The collapse or damage of the Marycrest overbridge would close all three transport options. The collapse or damage of the Ōtaki overbridge would close all three route options. Having all three Ōtaki River bridges (Expressway, Rail and local road) so close together could see blockage and subsequent disruption for a year or more. And remember, earthquakes can be greater that 7.1 and they do not need to be that great to cause significant damage.

Is NZTA conscious of this danger? How could they not be you ask. In fact the Te Horo Road Action Committee chairman, Ōtaki resident Peter Curling, comments “Whilst not identifying that particular scenario, the THRAC submissions highlighted the lack of disaster separation in the NZTA proposal. Earthquake damage could cause many months of chaotic disruption. Both overbridges, but Ōtaki in particular, are extremely vulnerable to any incident such as significant flooding or, say, a petrol tanker accident and all three transport routes could be taken out.”

Whilst evidently included in submissions presented during the consultation process, we are told that the submissions outcome report to the NZTA Board was silent on the issue of accident or natural disaster threats to the NZTA preferred route. Equally, we are told that there has been no Board reaction to the dangers again identified by THRAC in its hearing before the Board in June.

In any event, isn’t road closure and months of disruption something we just have to accept as we choose to live in an earthquake prone area? “To some extent yes,” says Curling “but alternative routes available separate the local and State Highway roads so that the likelihood of both being seriously damaged is significantly reduced. That means that traffic could simply be diverted onto the unblocked or less damaged road allowing local and through traffic and facilitating more speedy repair of the blocked or more seriously damaged road.”

Mr Curling says “having had the possibilities pointed out, isn’t it irresponsible of the NZTA and its Board to continue with a proposal that will leave local and through traffic as vulnerable to total disruption as ever? You be the judge.”