Future-proofing RNZ's infrastructure

Radio New Zealand (RNZ) successfully replaced two ageing AM broadcast masts with one new mast at the Henderson transmission site, securing Auckland's emergency broadcasting capability for the next generation. Kordia played a major role in the project with the design of the new mast, development of the works methodology and the rigging works on site.

RNZ’s Henderson transmission site had long been the backbone of AM broadcasting for the wider Auckland region, carrying AM radio services from two ageing masts: a 122-metre structure over 90 years old, and a 153-metre mast dating back more than 70 years.

The challenges were significant:

• The proximity of high voltage power lines, critical underground services, transmitter building, roads and the Northwestern Motorway limited the methodologies that could be used for the works. The ground condition on the two sites required specialist crane access track and hardstand engineering, and trees on boundary areas created consenting complications that took months to resolve.

• Throughout the project, RNZ’s AM services, including its emergency broadcasting function, had to remain available with minimal disruption.

Kordia's structural engineering and specialist rigging teams developed a comprehensive plan to decommission both masts and install a new 110-metre replacement – the height determined by RNZ's AM operating frequency requirements.

The design drew on proven methodology from a prior Kordia mast project at Porirua’s Titahi Bay, adapted for Henderson's unique site constraints. The new mast was engineered with a minimum 50-year design life.

Constructed in six-metre sections for transport efficiency, the mast was assembled by Kordia riggers into four larger sections on site before crane installation. Each section required temporary and permanent guy wire installation before the next could be lifted into place.

Removing the 153-metre southern mast presented a distinct engineering challenge. With hook heights beyond crane reach for the upper portion, and space constraints preventing ground-level operations, the top 40 metres required helicopter removal. Sections were cut to weigh no more than 800 kilograms – well within safe lifting limits – and the helicopter navigated between guy wires to place each section within the restricted site area.

Service continuity was built into the project from the outset, with careful management of outage windows. Emergency broadcasting protocols were established to halt work and restore services immediately if critical announcements were required.