On April 7, a significant landslide resulted in the closure of Pennsylvania State Route 30 in Allegheny County. The route is a principal artery to Pittsburgh and supports more than 22,000 vehicles per day. The slide demolished one apartment building, severely damaged another, and impacted a single-family home.
The Pennsylvania Department of Transportation (PennDOT) called on Gannett Fleming, as a proven partner on similar emergency projects, to provide expertise and assistance. This included performing a visual reconnaissance of the site, executing a cursory review of the available record drawings, and slide remediation advisement for the continued sinking condition of the roadway. Gannett Fleming also consulted with PennDOT on installing bypass pumps of storm drains around the site to limit water infiltration.
“Fortunately, after some initial evaluation of accelerating slope movements, PennDOT and Gannett Fleming decided to close the roadway and evacuate residents at the toe of the slope, including those who lived in the apartment building,” said Brian Heinzl, PE, Gannett Fleming geotechnical project manager. “This collaboration was a monumental feat that demonstrates Gannett Fleming’s commitment to the safety of our communities and maintains our position as trusted partners to our clients.”
Under Heinzl’s leadership, Gannett Fleming prepared a comprehensive landslide remediation design and prepared a bid package in just eight working days, which included:
- Design-build roadway plans for roadway surface and drainage repairs
- Details for excavation and benching to remove the landslide material and replace it with durable rock embankment
- Final structure plans for construction of a 400-foot-long anchored soldier pile and lagging retaining wall to support the new embankment
- Special provisions needed for PennDOT to advertise the project for bid.
Contractors had four days to review the drawings and prepare a bid. The accepted bid was approximately $6.5 million, only 1 percent more than Gannett Fleming’s estimate.
The recovery project schedule requires 24/7 operations to remove 35,000 cubic yards of material, construct the anchored wall, and rebuild the 90-foot-high slope with engineered fill materials. The goal is to reopen the road by the end of June.