By Linda Kaplan
On December 28th, several ASCE Pittsburgh Section Younger Member Forum (YMF) members eagerly waited to catch sight of the Greenfield Bridge implosion. Best known as the site of the “bridge under a bridge,” the Greenfield Bridge has been a poster-child for failing infrastructure in the area and the necessity for smarter investing.
Originally constructed in 1921, the Greenfield Bridge carried Beechwood Boulevard over I-376 (Parkway East) near the Squirrel Hill Tunnel. The concrete open spandrel deck arch had a 466’ total length with a 274’ main span over the Interstate. When chunks of concrete began falling off of the structure causing safety concerns for traffic on I-376 below, $700,000 was spent to build a simple steel structure below the bridge, to catch the falling debris. The situation even gained national attention when it was featured in a 60 Minutes piece and a Last Week Tonight episode on failing infrastructure.
A contract for full replacement of the structure was awarded in August of 2015, and on December 28th, the existing structure was demolished. A large soil “pad” consisting of 4000 cubic yards of fill was piled 10 feet high on the section of 376 that was below the bridges and both the Greenfield Bridge and the “catch” bridge were imploded, collapsing onto the Interstate below.
YMF members joined 1000s of other spectators in Schenley Park to watch the implosion live. When asked why they were there two hours early, section Director and YMF Past-President Linda Kaplan, PE, told WTAE news “We really wanted to make sure we got a good spot for the view, and being a bunch of bridge engineers, we really thought it was going to be very crowded because we assumed everyone would be this excited about it.” Ms. Kaplan was also interviewed for the on-air reporting and can be seen discussing the implosion at the end of the video here. All members who attended agreed that it was well worth the cold 2 hour wait to see the implosion live. Other members reported feeling the shockwave as far away as Greentree.
Material from the demolished bridge is part of a massive reuse and recycling project. Concrete will be ground down to be used as fill, and the steel is being trucked to Josh Steel Co in Braddock. A Post-Gazette article describes the details of the program.
Construction will now begin on the new steel arch structure designed by HDR, Inc. The new bridge is scheduled to open in the Spring of 2017 at an approved cost of $15,500,000. Included in the design are nods to the historic nature of the old bridge, including urns and ornate lampposts. Considering the extensive repairs that were done on the existing structure over the years, Section History and Heritage Chair, Todd Wilson says “At least in some ways, the new bridge might pay more tribute to the original idea of the bridge than the previous bridge in its current state.”