Huntly Power Station

Norman Hill (Rāhui Pōkeka iwi) liaises between Genesis Energy and his iwi of Huntly. He has been researching the Waikato River environment in relation to his people for over 7 years.

Huntly power station

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Huntly power station in the North Island of New Zealand is a coal and gas fired steam plant. Coal or gas is burnt to generate steam at 540ºC and 166 bars (2,300 psi) pressure, which drives a generator.

Rights: The University of Waikato Te Whare Wānanga o Waikato

During his involvement with iwi and the river, Norman spent a summer managing the monitoring of the river for Huntly Power Station (HPS). He looked at the impacts HPS has on the river, the environment and the community and how Genesis Energy (owners and operators of HPS) manage these impacts.

HPS is the largest thermal power station in New Zealand and is situated on the banks of the Waikato River in Huntly. The original four generators were built between 1973 and 1985, and the station was upgraded with a gas turbine plant in 2004. A further upgrade in 2007 increased the station’s production of power from an original 1000 megawatts (MW) of electricity to 1485 MW. The station supplies about 17% of the country’s electrical power.

HPS and the river

To make electricity, the station uses steam to turn turbines that produce electricity. Coal and gas is used to heat water from the river to produce steam. The water is then returned to the river.

Norman’s work included monitoring the water intake and discharge. Restrictions are placed on the amount of water taken, and screens through which the water passes have been modified to reduce damage to fish (such as īnanga elvers and smelt). Hot water discharging into the river can kill organisms that live in the river. HPS is designed so that water is cooled to 25°C or less before it is discharged. Adhering to these conditions mean that, on very hot summer days, the station cannot operate at maximum capacity and has sometimes effectively been shut down. A new cooling tower (where heat can be transferred to the atmosphere) has been built as part of expansion works at the site. This allows one 250 MW unit to run at full load even during hot summer days.

Submerged curved concrete walls (Iowa vanes) were built to channel water entering and leaving the station close to the left bank. This is intended to decrease entrainment of fish and larvae in the intake, to enhance mixing of the cooling water into the river and to limit sedimentation. A canal was dug so that tuna (eels) could bypass the intake and discharge area.

The combustion of coal at the station produces ash that needs to be disposed of. It is mixed with water, and this slurry is pumped from the station to ash ponds. The ash settles, and decant water is pumped back to the station, added to the cooling water and discharged. The water is monitored to ensure it achieves water quality limits. Steps are being taken to minimise leakage of water from ash ponds where water can’t be returned due to poor water quality.

Stormwater is also monitored – mainly to check that it does not carry high sediment loads (from coal particles). Air is monitored for limits of contaminants from combustion such as carbon monoxide, sulfur dioxide, nitrogen oxides and coal particles.

Norman’s work now brings groups of people together for the restoration of the river. Genesis Energy continues to monitor HPS to keep interference to the river and environment to a minimum. They have also undertaken to enhance and maintain a number of river restoration projects.

Cultural impacts

Before HPS was built, a kuia had predicted that an octopus would be built in Huntly. Iwi believe the octopus is HPS and liken the interrelated infrastructure and activity, such as roading and mining, to the tentacles of the octopus.

A marae formerly occupied the site on which HPS is built, and the local iwi tell of hearing frogs, collecting swan’s eggs and fishing for the once plentiful tuna.

Along with other factors such as the introduction of exotic species, overfishing, draining wetlands and farming intensification, HPS may have contributed to the decline of the health of the river. This decline has impacted on the people of the river. For example, it was the function of the kaumātua to pass on mātauranga to the youth. With the decline of the river resources, the need to know about them became redundant – and so did the job of the kaumātua along with the loss of his mana.

Another example describes early Huntly as ‘the seat of the King’ because of the abundance of food (particularly tuna) that was taken from the river. Dignitaries were hosted there for this reason. The decline of the health of the river and loss of food resources has meant this no longer happens. This also impacts on the mana of hapū.

Iwi appreciate the power that HPS supplies. They appreciate the work that it provides for their people – including work in the surrounding coalmines (providing coal for the station). They would have preferred that HPS was not in their backyard. Compromises were made. Genesis Energy now endeavours to meet the requirements set by resource consents to help restore the health of the river.