Toxic sludge removed from the Waiwhetu stream has been spilt on a road in Lower Hutt.
The sludge slopped out of the back of a truck after it had to stop suddenly for a pedestrian at a roundabout.
Wellington Regional Council says half a cubic metre of the ooze was cleaned off the road and sand was spread to absorb any remnants of the sludge.
Hutt City Council is to inspect the clean-up.
Removal of toxic soil from a landfill in Wainuiomata began on Thursday, after contractors were locked out of the site.
Lead-contaminated soil came from the banks of the Waiwhetu stream was wrongly taken to the landfill in October.
The clean up was supposed to start on Wednesday but the regional council says the owner of the landfill stopped contractors from going in.
WRC says the owner wanted an abatement notice that proves the council has been ordered to remove the material, so he won't be prosecuted for allowing the contractors to do the work.
Up to 15 truckloads of material will be removed from the landfill.
WRC says the landfill will then be tested for contaminants and more material will be removed if necessary.