Nearly a dozen state bridges in Butler County will be replaced as part of an initiative by the state Department of Transportation.

PennDOT is preparing to choose a private-sector team to replace at least 558 bridges statewide and maintain them for 25 years.

The Rapid Bridge Replacement initiative bundles hundreds of bridges into a single contract to take advantage of design similarities of the bridges and economies of scale to reduce the cost to taxpayers.

The bridges to be replaced are:

• Zelienople borough bridge carrying Route 68 over Glade Run in Zelienople

• Route 308 bridge near Rider Church Road over a tributary of Stone Run in Center Township

• Freeport Road bridge near Caldwell Drive over a tributary of Thorn Creek in Jefferson Township

• Bonniebrook Road bridge near Ringneck Lane over Bonnie Brook in Summit Township

• Saxonburg Boulevard over Bull Creek in Clinton Township

• McCalmont Road over Connoquenessing Creek in Butler Township

• Brownsdale Road over Glade Run in Forward Township

• Cruikshank Road over a tributary of Glade Run in Middlesex Township

• Seneca School Road over Connoquenessing Creek in Jackson Township

• Thompsontown Road bridge south of Queen Junction Road over B&LE rail tracks in Clay Township

• Route 19 southbound ramp over Route 19 northbound in Jackson Township

The 11 bridges in the county carry a combined 34,000 vehicles on a typical day.

The busiest of the bridges is the Freeport Road bridge near Caldwell Drive, which averages more than 8,500 vehicles per day.

The bridges and ramps span 24 to 145 feet, with the Route 19 southbound ramp being the largest.

All of the bridges are considered structurally deficient by the state. However, that does not mean the bridges are unsafe.

A bridge is considered structurally deficient if there is deterioration to one or more of its major components.

The McCalmont Road and Thompsontown Road bridges both have posted weight limits.

Four private industry teams are competing for the contract and PennDOT expects to name a winner at the end of October. The winning team will provide its own financing and be reimbursed by PennDOT over the life of the 28 and-a-half-year contract.

Construction of the new bridges is expected to start in the summer of 2015. All bridges must be completed within the first three-and-a-half years of the contract. The winning team also assumes responsibility for major maintenance for 25 years.

The state will maintain ownership of the bridges and will handle snow and weed removal. The state also has right to close a bridge in an emergency.

The teams competing for the contract are Plenary Walsh Keystone Partners, Keystone Bridge Partners, Commonwealth Bridge Partners and Pennsylvania Crossings.