Drill results will help shape future city

Despite insurers and the Earthquake Commission having earlier fallen out on talks over a joint drilling programme, they are now forging their drill results together on a joint website.

The Canterbury Geotechnical Database is designed to give geotechnical and structural engineers access to information about the region's quake-damaged land, and has been set up by the Canterbury Earthquake Recovery Authority (Cera).

The site will allow insurers and engineers to share their knowledge to assist further analysis on buildings and foundations, Cera said.

Talks between the EQC and insurers on collaborative drilling broke down a couple of months ago after long negotiations particularly on over-cap Christchurch properties.

The EQC has been managing a drilling programme for "under- cap" technical category 3 (TC3) properties - those with less than $100,000 of repairs needed while insurers are doing the remaining over-cap TC3 properties.

EQC chief executive Ian Simpson said the commission's drilling programme was still slated to finish by March, with the potential to finish earlier, based on the 12 to 15 working rigs. The private sector was drilling in parallel.

With the drilling work the EQC and others were now doing, geotechnical maps showing soil conditions could be "to the nearest 10 metres to show land conditions for every single section across Canterbury".

The drilling was required on the weaker TC3 land, which is more prone to earthquake damage, but EQC has also been drilling on other land.

"There's the broader data we're capturing and have been for a while around the land conditions. All of that is being fed into a Cera database, so will be available going forward," Simpson said.

The EQC worked on the basis that all the earthquake or disaster information generated, that was not of a personal or private nature, "becomes a public good," commission chairman Michael Wintringham added.

Simpson said the EQC had been running both cone petrometer tests and vertical boreholes.

It had completed 2800 CPTs and 743 boreholes on both TC3 land and that where homes had suffered substantial foundation damage.

The closeness of the holes depended on the apparent damage. "It depends on what we find, how closely we need to do the bores. So if the information is consistent over a relatively wide area, we can leave it wide and in other places (narrow the spacing)," he said.

A Cera spokesperson said the database would provide efficiencies with up to 20,000 individual deep investigations to be undertaken during the post-earthquake rebuild of Canterbury.

All the data would be publicly available after a building consent was lodged for a site, however it would not otherwise be readily accessible.

The collection of data would help with hazard analysis, flood management and geotechnical investigations.

Simpson said the EQC had so far paid out almost $4 billion in its programme, shared with Fletcher EQR, of repairing 170,000 houses and property settlements.

Those houses with repairs totalling from $50,000 up to the $100,000 cap would be repaired by the end of 2013 and the remainder finished by the end of 2015.

The view that TC3 land needed super-strong designs could again be taken to the extreme in preparing for a one-in-500-year event when houses had only a 50-year life frame, Simpson said.

The Press