After property owners threatened to file a lawsuit over an anticipated street-paving assessment, the Urbandale City Council voted unanimously Tuesday to approve a $1.9 million tax and an incentive package to encourage contractors to finish the job on time.

“We will sue you and we will crush you,” warned Gregory Nepstad, 3512 156th St., one of 17 property owners who spoke during a two-hour public hearing on the special assessment, many of whom joined Nepstad and his wife, Mary Sloan, in saying they would band together to file a lawsuit challenging the assessments.

At issue is a $6.7 million project to widen a 1 1/2-mile stretch of 156th Street to five lanes and add sidewalks and a bike trail. Longtime residents told the council that they had hoped the area would remain rural. Development has added residential and commercial developments and an increase in traffic. Councilman Tom Gayman remarked that he recently took a drive on the street and counted 165 potholes or other defects. “The street is in need of repair,” he said.

Special assessments related to the project affect 228 properties, with fees on 139 prepaid by developers. The levies have ranged from about $200 to more than $140,000, and it was the discrepancy that irked many landowners, particularly owners of large-lot acreages.

Nepstad said the special assessment on his 6 1/2-acre property was $45,000.

As part of the project, the City Council approved an incentive package worth a maximum $150,000 to contractors if the project, slated to begin this spring and end by December 5, comes in ahead of schedule. Contractors would pay a penalty of $1,500 for every day they miss a series of target dates.