As straight
as you can.
North Island Grid
Upgrade.

Given the project’s scale, there was understandable public opposition towards the project. Large-scale infrastructural projects impinge not just on the landscape but also on the rights of private property holders, but without such infrastructure the country’s ability to support itself is compromised. In this case, the aim was to devise a route of least impact for the transmission line.

Early research of transmission lines provided the designers with an opportunity to ‘get inside the skin’ of the infrastructure. Close observation and measurement of existing 220-kilovolt lines allowed factors influencing prominence and the degree of effect at different distances to be distilled. The measurements showed that the degree of effect fell away at a faster rate over the first few hundred metres and then tapered off at a slower rate.

The research also revealed the principle that straight lines are less obtrusive than those that weave around landforms and vegetation. Isthmus designed a set of principles for the detailed design of the line that included straight alignments, avoiding doglegs and heavy strain towers, and using small angles where changes in direction were necessary. Like ships, the larger the transmission line the more smoothly they need to turn. Consistency in tower height and spacing was another principle.

Designing the route for the transmission line meant taking a place in the inner circle of decision makers (a position not always afforded designers in large-scale projects). The approach the team followed was attributed the acronym ACRE: Area, Corridor, Route and Easement, which required assessing alternatives at progressively finer scales. The team initially assessed the entire ‘Area’ between the Kaimai Range to the east and the Tasman Sea to the west, approximately 200 kilometres long and 80 kilometres wide.

The exercise was repeated in more detail as the corridors and routes were narrowed. At the stage of designing an indicative alignment (or ‘easement’) in the two short-listed routes, the design process became more ‘analogue’, undertaken initially by three people in a car – engineer, planner, landscape architect – drawing alignments by hand on a map.

Given the great public interest in the project, transparency of documentation was a particular requirement, with an initial peer-reviewed methodology report prior to starting the project, separate reports for the Area, Corridor, Route and Alignment phases, and a technical report for the Assessment of Environmental Effects (AEE) produced. Isthmus prepared approximately 100 photo-simulations of the transmission line as part of the process.

Subsequently, NIGUP was examined by way of a Board of Inquiry, which sat for more than three months before approving the project in 2009. One of the Board requirements was that an ‘Augier’ condition relating to offsite landscape mitigation. Transpower offered landscape mitigation to residents deemed to have adverse visual effects within one kilometre of the line. Managed by Isthmus, the mitigation required the planting of trees to screen views of pylons and was carried out on approximately 440 properties over a five-year period.

The North Island Grid Upgrade Project is not categorised easily – the work does not fit neatly within either environmental assessment or design. Rather, it integrates research, environmental assessment, design and mitigation within the framework of the Resource Management Act (1991). In short, the project pushes the influence of the landscape architect on such complex infrastructure projects.