Whanganui's new $39 million wastewater treatment plant is on track to be operating by June.
The last of the construction work, including mechanical and electrical work, is still being completed but Whanganui District Council infrastructure general manager Mark Hughes said some testing was already under way.
Overall the project was running on time.
"In some areas, we are ahead of time. We have started some testing and pre-commissioning earlier than planned," Mr Hughes said.