Turitea Wind Farm

16/05/2022

Overview

When generation connects to the national grid at the Linton Substation, the Turitea Wind Farm will be the largest wind farm in New Zealand and the first large-scale addition since 2014. The wind farm will comprise of 50 3.6MW turbines split between two 220kV-33kV substations. It is also believed to be the in the top 5% of wind generation sites worldwide.

Once both zones (North and South) are complete, the wind farm will generate 470 GWh per annum - enough electricity to power 375,000 electric vehicles every year.

For both zones, Downer has provided the Electrical and Civil Balance of Plant, including the design, construction and delivery of the roading infrastructure, turbine foundations, 220kV substation, 33kV switchroom and 47km of underground 33kV electricity collector groups with connections to the 50 wind turbine generators (WTGs) in addition to co-ordinating the grid connection to Transpower.

Challenges

The ridgeline location and environment of the Turitea Wind Farm proved to be a challenge. Turitea Wind Farm is located in the Turitea Reserve which is a major water catchment area for Palmerston North and is also the habitat of many flora and fauna - many native, including reptiles, bats and birds. These factors meant that strong environmental management was essential.

The topography and climate conditions of the wind farm's location were also challenging. Intense rainfall, high winds, snow during winter, and dry conditions during summer meant that construction was often hindered or even delayed.

Due to the single access and narrow ridgeline roads co-ordination between the civil roading and electrical cabling works to ensure deadline were met. DBD (Design – Build - Deliver) all engineering specifications, proposals and studies needed approvals from all parties which extended durations in some cases, where multiple rounds of approvals were required.

Solution

To protect the environment, Downer installed several different controls through more than 210 individual devices.

These included:

• sediment retention ponds
• decanting grit traps
• decanting earth bunds,
• clean and dirty water diversion bunds
• silt fences
• super silt fences
• smaller grit traps
• fish-passage culverts

Downer also conducted daily checks on all vehicles and plant before work commenced and kept them well-maintained to reduce risk of spills. Members from the International Erosion Control Association will be visiting the wind farm in mid-2022 due to the extraordinary nature of the scale and scope of erosion and sediment control devices on site.

With respect to  weather conditions, Downer implemented strategic planning to take advantage of periods of favourable conditions and co-ordinate activities.

Downer also undertook three major productivity initiatives:

The first was to drive innovations within the existing programme to minimise the heavy truck movements that were disrupting the local community. This included resurveying volumetric design of the haulage road connection the North and South site, acquiring a second concrete batching plant, improving on-site cut-to-fill ratios, and maximising existing heavy truck fleet productivity during the construction season.

The second was to propose a completely new haulage road to the southern end that would completely bypass Kahuterawa Road. Downer engaged all relevant consultants and designed a haulage road. This initiative was stopped only by the loss of one landowner signature – others were strongly in support. The client Mercury Energy were sufficiently persuaded that they even contemplated buying out the entire farm to achieve this haul road.

The third initiative was to successfully persuade Mercury Energy to increase the heavy truck haul limits by altering the original resource consent limits. Downer drove the formation of the evidence and marshalled consultants and legal team. The proposal was publicly notified, and the local community were engaged. Palmerston North City Council initially opposed any such change, but with careful evidence in mitigation they were persuaded not only to recommend the proposal directly to the Environment Court, but also to report that a truck movement increase was possible with certain extra mitigations.

In April 2022, Downer then advised Mercury Energy that the on-site programme innovations were now enough to obviate the need for changing the consents.

On Downer’s advice Mercury Energy wrote to the Environment Court and Palmerston North Council that proceedings were stopped due to successful progress on site.

The result was viewed by local media, by Palmerston North Council, and by the community as a huge win for all.

Senior Mercury staff praised Downer staff for the open, productive and effective manner in which they had solved this problem together.

Outcomes

Weekly inspections of the site controls from the Horizons Regional Council have resulted in a compliance score of 98.8% (2021) and 99.1% (2022 to date). Senior Project Director and Project Managers strict adherence to Downer HSE practices.  Their approach to the programme delivery has ensured strong environmental performance.