Anything less than 34 per cent is earthquake-prone.
It was decided the building would need to be vacated, meaning finding a new home for patients and services in a system already struggling with significant capacity constraints.
So it was somewhat surprising when it emerged this draft assessment was yet to be peer reviewed. A second opinion is critical in the engineering landscape because it often results in a different outcome, and sometimes a substantial one.
Engineering is not an exact science and those in the industry have acknowledged it's easy to be conservative, but difficult to be realistic.
In the case of the Heretaunga Block, a second opinion resulted in just one element of the building being earthquake-prone (the precast concrete façade panels), instead of several.
In other words, the situation wasn't as bad as first thought.
But it wasn't great either. Board papers show the concrete floor diaphragm and moment-resisting frame have only been rated at 34 per cent NBS.
That is literally 1 per cent away from being earthquake-prone.
The concrete shear walls aren't much better at 35 per cent, while the gravity columns are 40 per cent.
The stairs are more convincing at 60 per cent.
The specific ratings of all these elements were not publicly available when Lower Hutt mayor Campbell Barry raised concerns about the DHB's intention to "plough ahead" with its original plans to vacate the building.
"What is it? Either the building is a significant earthquake risk and needs to be vacated, or it can be mitigated as the latest information suggests," Barry said.
While the initial engineering report is materially different to the peer-reviewed version, the circumstances going forward appear to be more or less the same.
The reports haven't really created a one or the other scenario.
The DHB is looking at remediation options to strengthen the building to 67 per cent NBS.
The slightly improved, but still low, ratings are nowhere near that target and will still need significant strengthening too.
For this reason DHB bosses still expect the scope, cost and time for remediation to be similar to initial indications before the peer-review.
They considered these to be neither feasible or cost effective while the building continued to be occupied.
It's not unreasonable for the DHB to want to draw the line at 67 per cent.
Many corporates and Government departments have a much higher threshold for earthquake ratings than what legislation requires, as has been exemplified in Wellington City countless times.
Furthermore, in a hospital building like this one anything scored as 34-60 per cent NBS is still classified as an earthquake risk.
The DHB has a strong argument in bringing the whole of the Heretaunga Block up to a higher standard, or rebuilding.
Otherwise it runs the risk of those parts of the building currently sitting at 34 per cent NBS eventually becoming earthquake-prone as legislation and engineering thinking changes.
Or worse, they don't perform very well in a significant earthquake and the hospital can't be used in its full capacity when it is needed most.
