Substandard steel imported from China has forced contractors building the Huntly section of the Waikato Expressway to redesign the piles for two bridges.
The $458 million project, a joint venture between Fulton Hogan and HEB Construction, hit a hiccup when steel tube piles arrived from China and tests discovered they weren't up to scratch.
The steel tubes were meant to be driven into the ground and used as piles. However, they have now essentially been filled with concrete and used as reinforced concrete piles in two of the four bridges.
"This approach has been successful and does not compromise on quality or safety of the end design," Fulton Hogan project director Tony Dickens said in a statement.
Replacement steel tube piles may be used on the other two bridges. They were talking with the unnamed supplier about the problem.
The New Zealand Transport Agency says it won't be out of pocket.
"The costs for redesigning construction and replacing materials is borne by the contractor - there is zero cost to the taxpayer," highways manager Tommy Parker said.
The new pile design was independently peer reviewed and approved.
"There is absolutely no quality compromise between steel pipe piles and reinforced concrete piles," he said.
"Both do exactly the same job and last exactly the same time."
The project would not be delayed because the problem had been picked up early and the contractors came up with the alternative design within six weeks, he said.