The Pennsylvania Department of Transportation (PennDOT) in the US has selected Plenary Walsh Keystone Partnership to replace 558 bridges across the state.

Plenary Walsh Keystone Partnership includes 11 Pennsylvania-based subcontractors who submitted an $899m proposal for the replacement project, which will be done in a public-private partnership.

The project is expected to begin in 2015 and completed within 36 months.

"The goal for this project is not only finding cost savings, but also to minimise impact to the travelling public."

The bridges will be under the ownership of the state but the company will be responsible for redesigning and maintenance of the bridges for 25 years.

The project will pay an annual cost of $65m for the 28-year contract term with an average design, construction and maintenance cost of approximately $1.6m for each bridge.

The new project awarded to Plenary Walsh Keystone is said to be the biggest ever project awarded by PennDOT to manage the structurally defective bridges in the state.

The Plenary Walsh team was selected due to its past record and its financial capability to carry out the project.

The team is planning to issue $772m private activity bonds to fund the project.

PennDOT secretary Barry J Schoch said: "This agreement helps Pennsylvania take a big step to cutting further into its backlog of structurally deficient bridges."

"The goal for this project is not only finding cost savings, but also to minimise impact to the travelling public.

"This team has thoroughly detailed their traffic control plans and expects to finish construction eight months earlier than required."