Frequently Asked Questions
Q. Isn't the problem just due to the river rising (rather than the ground sinking)?
A. No. The level of the river has not changed. There is a daily fluctuation in river level as Mighty River Power (MRP) operate the control gates on the Ohakuri dam downstream of Ohaaki, but the operating range has not changed, and can not be changed, by MRP. The operating range is set by conditions of consent for the Ohakuri dam. MRP can not exceed these levels without breaking the law and there are river level monitors in place to check on this.
The problem is definitely being caused by ground subsidence. This is a result of depressurisation of the geothermal strata about 100 metres below ground. The drop in pressure has been caused by the extraction of steam to operate the power station. As the pressure drops, the strata compresses, and the ground above it subsides.
The problem is definitely being caused by ground subsidence. This is a result of depressurisation of the geothermal strata about 100 metres below ground. The drop in pressure has been caused by the extraction of steam to operate the power station. As the pressure drops, the strata compresses, and the ground above it subsides.
Q. Why not just turn off the power station?
A. Subsidence will not stop, even if the power station was turned off tomorrow. There is no practical way to stop it until it has 'run its course'. On current trends, the land around the Marae is expected to eventually drop to between 0.3 and 1.3 metres below high water level. These predictions will be updated when the next scheduled ground level survey has been completed in April 2010.
Q. What happens to existing land titles?
A. In the event that the Marae is relocated / rebuilt, there will be no change of ownership at the existing site, even if it goes under water it will still belong to the iwi.
Q. Do Contact Energy benefit if the Marae is shifted?
A. No. Contact Energy would prefer that the Marae stays as it is. But if subsidence predictions are correct then it will be untenable for the Marae to remain at its current site and still operate. If so then Contact are obligated to remedy the situation. They will meet the costs of relocating / rebuilding the Marae.
Q. Are there other options than relocating the Marae?
A. The Working Party have investigated a range of options including building up the ground level of the existing site, building dykes, pumping water in to the ground to try and counter the depressurisation, or just 'doing nothing'. These options are discussed in detail in the Sept 2004 Working Party Report. Having considered all of these options the Working Party agreed that the relocation option is best. This was the option that the Working Party recommended to, and had confirmed by, the hui-a-iwi on the 12th of February 2005. If that position changes (for example, on consideration of the recent slow-down in subsidence trends) then it will be for the iwi to decide. In the meantime the Working Party is continuing to work toward securing the preferred relocation site so that this option is at least available if required.