The demolition is part of a $23.7 million replacement project that involved construction of a new bridge approximately 100 feet upstream from the old structure.

The deck of the old 1,051-foot-long steel truss bridge was removed in recent weeks after traffic was shifted to one lane on the new bridge.

The remaining steel beams and truss members were severed today by 160 shaped explosive charges that were placed in 28 locations on the remaining superstructure, which then dropped into the Allegheny River in pieces for removal. The demolition contractor is Demtech of Butler, PA.

PennDOT’s northwest region has been preparing for the environmental impact of the bridge construction and demolition over the past ten years by removing approximately 155,000 mussels from the Allegheny River at the construction area under the bridge and sending them to other waterways in Pennsylvania and six other states.

Approximately 105,000 of those mussels were federally listed threatened and endangered species. The effort is thought to be the largest translocation of threatened and endangered species ever undertaken in North America.

“This project has been a long time coming, and we are very proud of the work that District 1 has done every step of the way; from design to environmental mitigation and construction,” said PennDOT District Executive William G. Petit.

Traffic will continue to be restricted to one lane on the bridge, and controlled by temporary traffic signals.

The one-lane traffic pattern and temporary signals were installed as part of an alternative construction plan that the contractor and PennDOT agreed upon to eliminate the need for the more than 40-mile-long detour that was originally expected to be required for the project.

The project involves construction of a new 1,124-foot-long, four-span continuous composite steel plate girder bridge upstream from the old Hunter Station Bridge. Work includes new concrete and asphalt roadway approaches and updated drainage, guiderail, landscaping and pavement markings, along with other miscellaneous work.

Work on the bridge replacement project started September 12, 2016, and the project is expected to be completed by March 28, 2018.

The contractor is the Mekis Construction Corporation of Fenelton, PA. The contract cost is $23,774,703.87, which is being paid entirely with federal funds.

PennDOT urges motorists to slow down when driving in work zones, and also to be alert to changing conditions, avoid distractions and to pay attention to signs and flaggers. Drive responsibly in work zones for your safety and the safety of the workers.

For more information on projects occurring or being bid this year, those made possible by or accelerated by the state transportation funding plan (Act 89), or those on the department’s Four and Twelve Year Plans, visit www.projects.penndot.gov.

Motorists can check conditions on major roadways by visiting www.511PA.com. 511PA, which is free and available 24 hours a day, provides traffic delay warnings, weather forecasts, traffic speed information and access to more than 825 traffic cameras.