"I just jumped in to have a go and my supervisor pushed me in and saw a bit of potential," Tau said.
"I went in, had a go and ended up winning it."
He will drive a Hitachi Zaxis-130 excavator as he battles for the national title.
Tau said some of the skills from work translated to the competition, but it was quite a different task.
"It requires a bit more finesse. As for practising, I'm unsure what the tasks are so it's a bit hard to prepare for. But I'm ready.
"The old knees are knocking a bit, but I just want to go in, have fun doing it and meet all the guys."
This year marks the 27th anniversary of the annual competition, organised by Civil Contractors New Zealand to raise awareness of the skill involved in excavator operation and the rewarding careers available in civil construction.
Civil Contractors New Zealand chief executive Peter Silcock said the competition's mix of entertainment, skill and hi-tech machinery was expected to draw a big crowd.
"Every year the competition gets bigger and better. It's an ideal way to showcase the outstanding skill of New Zealand's excavator operators and the capability of the impressive machines they operate.
"Whether you're considering a career in the industry, or just looking for a fun day out with the family, this is the place to be."
Tau was looking forward to the challenge and was excited to see what he could do in front of his wife and kids.
"It should be fun, just give it my best shot and enjoy the moment."