Three highway engineers have been reprimanded in the wake of a botched paving job on Interstate 40 that will cost the state more than $18 million to repair.

Transportation Secretary Lyndo Tippett on Friday issued his final report into flawed pavement on a 10-mile stretch of I-40 in Durham County. Within months of a major widening project, pavement began crumbling on the highway between the Durham Freeway and U.S. Highway 15/501.

Inspectors determined that expansion joints weren't installed properly when a new layer of concrete was laid over I-40 during the widening. Tippett said in his report that the expansion joints fell through the cracks because of shifting responsibilities within the Department of Transportation and contractors, badly written contracts and a lack of on-site inspection.

 Granite Construction Co., the contractor on the widening project, agreed to absorb $3 million of the cost to fix the pavement, and the DOT plans to take legal action against HNTB, an engineering firm that the state hired to inspect the I-40 widening, Tippett said. HNTB has denied any responsibility for the problem, he said.

DOT engineers Victor Barbour, Wiley Jones III and Tracy Parrott received written warnings for their involvement in the project, Tippett said. State Highway Administrator Len Sanderson decided to retire at the end of the year.

Tippett said the DOT would implement new controls to prevent future problems in the future, including more on-site inspections by senior engineers and requiring contractors to provide performance warranties.