Susceptibility to Liquefaction

[Sam_Carissa]

We recently made a conditional offer for a property in Ennis Ave, Pakuranga Heights. Based on the LIM report we obtained, it mentioned that there is uncertainty over the susceptibility to liquefaction.

The report further mentioned that this property is in an area where the liquefaction susceptibility ranges from very high to negligible and that it is not possible to assign a single value on this matter due to the proximity of the property to boundaries of geological data used in the assessment.

Can anyone give us further details on this matter? How is Ennis Ave in general and is there any issue / problem with regards to this should we purchase the property? Also, will this have any effect on the price?

Your views will be most appreciated! Thanks!

[Re@der]

This is usually soil creep down a hill.
From wikipedia
Soil liquefaction describes the behavior of soils that, when loaded, suddenly suffer a transition from a solid state to a liquefied state, or having the consistency of a heavy liquid. Liquefaction[1] is more likely to occur in loose to moderately saturated granular soils with poor drainage, such as silty sands or sands and gravels capped or containing seams of impermeable sediments [2]. During loading, usually cyclic undrained loading, e.g. earthquake loading, loose sands tend to decrease in volume, which produces an increase in their porewater pressures and consequently a decrease in shear strength, i.e. reduction in effective stress.

[drelly]

QUICKSAND!!! ruuuuuun!!!

[Bulldog]

Worth getting a specialist to do a pre purchase inspection. Ring Steven Price 4897872 might be able to advise you over the phone.

[ambitious]

I would suggest talk to an expert, however, dont totally treat this as a major....it may well be that all the houses on that side of the street have the same issue, and, it is probably nothing, or, not a big issue....it could be that drainage and side walls/excavation may fix it, however good to get estimate on costs....aside from that, this is a good opportunity to negotiate the price, with these issues in mind.....but, depends on risk profiles I guess

[Davo36]

I have a note on the council file for my home saying it has 'unstable soil'. But it's Titirangi, it's all hills, so I don't care.

It depends on the angle of the slope. Mine is around 25 degrees, much more than that and I would worry about it.

Do you have big old trees on or near the property? Have they been there for ages? And look like they're not moving? If so that's a good, positive indication I reckon.

But if it's all sort of lawn or something, there may be noting stopping it from moving.

A geotech report would help but costs maybe $1500 min and more if they drill etc.

David

[Samuelj]

As i understand it liquefaction is a concern only with regards to major earthquakes ... i recall reading an article on earthquakes in nz which suggested that (for example) much of the centre of christchurch is considerd at risk of liquefaction when the big one arrives.

inshort, while it sounds alarming, you're going to need a direct line to God to know for sure if you need to worry about it.

Make some inquiries with the council etc by all means but my guess is it all comes down to how risk adverse you are

.... and earthquakes are a risk factor that nobody living in this country can completely avoid.

[Re@der]

SamuelJ
liquefaction during earthquakes is the same process but a different beast that allows a wave to go across sedimentary baisins river valleys etc that just lifts and falls everything in its path.
This example is a slower localised process and can often be seen in steep farms as a type of terracing as the soil slowly moves down the hill