A further $2.2 million is needed to complete the Dudley Creek flood remediation project.
The total budget was $49 million, but the city council needs $51 million to complete the work, which will ease flooding risk to more than 550 properties in the area.
Contractors have started widening St Albans Creek and Shirley Stream, which would return the areas around Shirley Stream and Edgeware Rd back to pre-earthquake flood risk.
But the work has proved more costly than expected.
That included $600,000 to remove contaminated land in Stapletons Rd and the Shirley Rd culvert being more expensive than expected.
The cost of increasing St Albans Creek’s capacity had gone up from $4.8 million to $6.1 million.
City councillors will decide today whether to approve putting a further $2.2 million into the project, which would be met with savings from the Bells Creek flood remediation project.
The area around Flockton St has already been returned to its pre-quake flood risk at part of the project, following the widening of Dudley Creek and the installation of an 800m bypass.