The Commercial Street Bridge over Interstate 376 came down in a controlled implosion Thursday morning, kicking off a 25-day effort to replace the aging span while minimizing long-term traffic disruptions on one of Pittsburgh's busiest highways.

PennDOT said the bridge, built in 1959, was demolished at about 6 a.m. July 16 after months of preparation. The agency had planned to bring down the bridge a day earlier but delayed the implosion to allow crews more time to prepare the structure.

The bridge carries Commercial Street over the Parkway East (Interstate 376) between the Edgewood/Swissvale interchange and the Squirrel Hill Tunnel.

The stretch of highway beneath the bridge sees about 100,000 vehicles each day, making it one of the busiest roadways in western Pennsylvania, according to CBS Pittsburgh.

Before the demolition, police and construction crews established an 800-foot safety zone around the bridge while PennDOT warned nearby residents to expect a loud blast and a temporary dust cloud.

No evacuations were ordered, and the area was cleared before explosives were detonated, CBS Pittsburgh reported.

The demolition is part of a $95 million bridge replacement project that uses Accelerated Bridge Construction (ABC), a method that allows much of the new bridge to be built before the old one is removed.

Rather than replacing the structure over several construction seasons with recurring lane closures, PennDOT constructed the replacement bridge alongside the existing span, according to TribLive,

With the old bridge now gone, crews will clear debris before sliding the new bridge sideways into its permanent position over Interstate 376. PennDOT said the move will be one of the largest lateral bridge slide operations ever performed in Pennsylvania.

The Parkway East closed at 9 p.m. Wednesday for the project and is expected to remain closed until Aug. 3. According to PennDOT, completing the replacement during a single 25-day closure will eliminate about four years of lane restrictions and traffic shifts that would have been required using traditional construction methods.

CBS Pittsburgh reported that PennDOT livestreamed the implosion so residents could watch from a safe distance instead of gathering near the work zone. Officials also encouraged motorists to avoid the area and follow posted detour routes throughout the closure.

Once the replacement bridge is in place, crews will pave the roadway, install barriers, reconnect utilities, apply pavement markings and complete inspections before reopening Interstate 376, PennDOT said.

The Commercial Street Bridge replacement has been under construction for nearly two years. The project is designed to replace the aging structure while reducing the overall impact on motorists by compressing years of work into less than a month of highway closures, according to TribLive.

Sources: CBS Pittsburgh, TribLive