Dips on Parkway East may have been caused by imploded Greenfield Bridge
February 20, 2016 12:00 AM
Crews from Mosites Construction work to clear Interstate 376's westbound and eastbound lanes of the remains of the Greenfield Bridge which had been imploded.
By Ed Blazina / Pittsburgh Post-Gazette
PennDOT and Pittsburgh officials are monitoring three slight dips in the road surface on the Parkway East that may be residual damage from the implosion of the Greenfield Bridge above the highway in late December.
Representatives from PennDOT, the city and bridge contractor Mosites Heavy Construction confirmed Friday that they are watching dips in three areas: the right outbound lane of the parkway, the right inbound lane, and the ramp from Forward Avenue in Squirrel Hill to the highway. If the conditions worsen this spring, the contractor may have to replace sections of the pavement.
The outbound dip definitely is related to dropping the bridge onto the highway, but Derrick Jeannerette, project manager for Mosites, said the company isn’t convinced the other areas are related to the bridge implosion.
Pat Hassett, the city’s assistant public works director overseeing the bridge project, referred to the damage as “very slight dips.” Falling debris also damaged the outbound shoulder beneath the bridge and caused cracks on the road surface there, but those were fixed before the road was opened four days after the implosion, he said.
“While there was evidence of structural damage, there was nothing very serious,” he said. ”We’ll take counsel from PennDOT on whether we need to do anything else in the spring.”
Subcontractors Dykon Explosives Demolition Corp. and Kesco Inc. used 1,400 pounds of explosives Dec. 28 to drop the bridge onto a cushion of dirt that had been placed on the highway to protect it. Mosites has a $17.5 million contract to replace the old concrete bridge with a steel structure.
“There is a slight dip [in several areas],” said PennDOT spokesman Steve Cowan. ”If it did become significant, we would have them fix it. We’re just monitoring the situation at this point.”
Mr. Hassett and Mr. Jeannerette said the outbound shoulder damage and surface dip occurred in an area where there was a column from the safety bridge that had been built beneath the Greenfield Bridge in 2003 to catch falling debris. Both men said the damage was ”preventable” but it’s not an indication that anything was done incorrectly.
“You plan your demolition to get it to fall a certain way and it doesn’t always happen,” Mr. Jeannerette said. “Everything kind of came down at that one spot. It seemed like everything folded in right there.”
The damage occurred for one of three reasons, Mr. Hassett said: not enough cushioning, a large mass of the old bridge falling in one place, or the surface had a pre-existing condition that came to light as a result of the implosion.
“This is an acceptable level of impact,” he said. “I think we took all of the necessary precautions. What we are seeing before us are minor consequences given the magnitude of the project.”
Mr. Jennerette said he doesn’t expect the dips to get any worse. If they do, his company is on the hook to make repairs.
“I think overall we were very pleased,” he said. ”I think given what went on there, we consider the demolition to be a success.”
Mr. Cowan agreed.
“We work very closely with the city of Pittsburgh and have a good relationship,” he said. “They took all of the precautions possible.”
Ed Blazina: firstname.lastname@example.org or 412-263-1470.
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