Horizons Regional Council says the diesel spill in the lower reaches of the Whanganui River has been contained and recovered as much as possible.

The spill was reported on Thursday morning.

Horizons’ emergency management manager Ian Lowe said staff were onsite until Thursday evening recovering what they could.

“We trawled an absorbent boom between two boats through the area to soak up as much as possible.

 “As diesel spreads out easily when in contact with water, and can cast a shiny film over a wide area, it’s not possible to determine exactly how much there was although we suspect it was a small quantity.”

When staff left the site there were minimal visual traces left on the water between the river mouth and boat ramp.

“Horizons staff met Whanganui iwi and hapū, who are providing leadership and support in the response, on site this morning (Friday) to check for remnants and discuss next steps,” Lowe said.

“Visually the site was clear today, however there may be some residue left which we expect the tide to either draw out or evaporate in the wind and sunshine.”

An investigation into the possible source and cause of the spill were ongoing and the situation would be monitored over the weekend, alongside hapū and iwi, Lowe said.

To its knowledge, there hadn’t been an impact on local wildlife, Department of Conservation (DoC) acting operation manager Whanganui, Jim Campbell said.

“DoC connected with Horizons yesterday and offered support in their response which hasn’t been required to date.

“This morning three rangers visited the South Mole and adjoining estuarine area to check for impacts from the spill on wildlife. Staff collected a significant amount of rubbish but did not see any signs of the spill.”

Horizons’ compliance team collected samples of the contaminant from the site for testing to confirm the substance and possibly provide insight into where it had come from, Lowe said.

“The team spent most of yesterday trying to find the source, which included checking some stormwater drains.

“We will continue to do what we can to determine what happened.”

The river management work under way for the Te Pūwaha port revitalisation project at the North Mole and boats in the port have been ruled out as sources of the spill.