Dialogue: That sinking feeling comes much too close to home

Events at Waihi have heightened the fears of residents of the Auckland suburb of Three Kings about the incompatibility of quarrying and mining in housing areas, writes CORINNE McLAREN*.

The question of who pays compensation to homeowners whose properties are damaged by subsidence has arisen yet again with the collapse of, and danger to, several properties in Waihi.

In Auckland, 10 minutes' drive from the city centre, members of the community and local pressure groups are battling quarry operator Winstone Aggregates over its ever-expanding operation at the 15ha scoria quarry in Three Kings.

Because of dewatering,,Winstone Aggregates has established a three-tiered zone of influence which contains about 2000 homes within about a 1km radius.

On conservative estimates, these properties are worth about $600 million. This amount does not include buildings such as shops, schools and factories, or council infrastructure and services.

The three tiers within the zone of influence refer to the potential levels of subsidence: zone 1 is closest to the quarry.

Damage to homes caused by manmade subsidence is not covered by insurance companies. Nor is it covered by the Earthquake Commission. It is up to the residents to prove that any damage has been caused by quarrying or mining activities.

Who would decide how the damage was caused? Who would pay for any damage caused by subsidence? Who would help the residents? What would happen to property values and the question of compensation?

Winstone, in response to residents' fears and concerns expressed over many months, drew up a deed of indemnity and a performance guarantee bond.

The deed of indemnity gives the property owners the option to make any claims of damage up to a maximum of $10,000. But this would cover only very minor repairs.

Any claims above this amount involve direct contact with Winstone, and possible lengthy litigation to prove the company's liability.

Why should residents have this worry when they have invested hundreds of thousands of dollars in their properties?

The thought of court action is unfair and inequitable when residents have to fight a large corporation and its technical experts and lawyers. The residents often do not have the same access to legal and technical counsel or the financial resources to find and pay for them.



Residents also argue that the performance bond of $5 million is inadequate. Repeated calls to local authorities and Winstone for a baseline engineering survey to measure existing surface levels on each property within the zones have fallen on deaf ears.

There are a number of parallels with the Waihi disaster. To expand and deepen the Three Kings quarry to sea level, about 80 m below, the operator is dewatering the volcanic basin by up to 5000cu m a day. At Waihi, the amount of water being taken is from 7776 to 15,000 cu m a day to deepen the open-cast mine by 60m.

(Dewatering the quarry at Three Kings was the only way Winstone could pursue its expansion plans. Community groups have also been successful in stopping this suspect water supply being piped for domestic use).

Numerous large volcanic vents and tubes are known to be below properties throughout Epsom, Mt Eden, Hillsborough, Three Kings and Mt Roskill.

In Waihi properties are believed to be above abandoned mine shafts and drives.

Many residents bought houses in these Auckland suburbs before Winstone notified its desire to pursue the expansion and dewatering programme.

The Auckland City Council continues to issue building permits for all types of housing in the area, particularly for infill housing developments within tier one of the zone of influence.

Are these new property owners aware that their home is in this tier?

Already numerous trigger points relating to the dewatering process have lead to a review because the computer model predictions and what has happened are different. This has alarmed residents who are waiting for the results with some apprehension.

There has been ground movement of up to 8mm within the zone of influence in Hillsborough.

This resulted in pumping levels being reduced for a short time until the Auckland Regional Council, the resource consent provider, allowed Winstone to continue.

Residents say previous inquiries about ground movement have met with no definite conclusions. They are not convinced that it is not caused by dewatering.

While subsidence may not occur now, continued dewatering over at least another few years could have significant impact, say, in seven to 12 years.

Subsidence is irreversible once it starts and the consequences are devastating. Imagine the effect to property values should subsidence of any measure occur in these suburbs. Where is the guarantee of titles?

Winstone has also been criticised for its lack of detail.

Numerous properties have been left off the indemnity property index, including many new apartment blocks and infill housing built in the past 12 months.

Community groups are aghast that the regulatory bodies gave resource consent approval to the quarry-mining company's applications to carry on activities in the middle of a densely residential area.

Quarrying or mining in residential areas is not compatible, and regulatory authorities should review planning policies when there is such a huge social and environmental impact.

* Corinne McLaren is president of the Three Kings United Group.