Liquefaction becomes a reality

The focus of Christchurch civic leaders remains largely fixed on the inner city and the many photo opportunities but many residents remain without water and only have intermittent power.

Worst affected are residents in the Avonside Drive/River Road area along the Avon River close to the centre of the city and in coastal suburbs like New Brighton, Bexley and Kaiapoi.

These residents have been told they may not get piped water again for weeks.

Emergency supplies and above-ground piping is being supplied to some, allowing them to use toilets again, although sewerage is being discharged into the Avon.

Anywhere near a waterway, swamp or old creek has been particularly badly affected by liquefaction and subsidence.

Liquefaction became evident immediately the quake stopped shaking on Saturday morning at 4.30. Many residents checking the outside of their homes in the eerily quiet aftermath would have heard the sound of water running.

For hours afterward it was assumed that water mains had burst because water bubbled up through crack in concrete like springs. But it brought black silty soil with it that covered driveways. When wet it had the consistency of heavy jelly.

In some cases small truckloads were deposited out the front of homes, raising concerns about whether there will be more slumping. When the silt dries it turns almost white and blows away in the breeze causing dust clouds.

Where the water and silt was trapped under concrete, paths and roads were pushed upward, tilting and breaking homes and creating mounds on roads and paths. The tar seal crust on many of these roads is now breaking up into rubble.

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