SR 30 Emergency Landslide Repair

POWERFUL TEAMWORK SAVES LIVES AND RECONNECTS ALLEGHENY COUNTY COMMUNITIES AFTER THE COLLAPSE OF A KEY TRAVEL ARTERY

Quick thinking by an engineering team before the collapse of Route 30 near Pittsburgh likely saved dozens of lives. An extraordinary engineering effort minimized the widespread disruption caused by the collapse. On April 7, 2018, a landslide crumbled the Route 30 roadway and dropped thousands of tons of debris down an adjacent hillside, damaging two apartment buildings beyond repair. Hours earlier, a team of Gannett Fleming and Pennsylvania Department of Transportation (PennDOT) engineers initiated the evacuation of residents. No one was injured, but the closure of the roadway threatened to paralyze the region, as 30,000 motorists depend on this stretch of Route 30 daily.

Working around the clock, Gannett Fleming delivered a comprehensive landslide remediation design and bid package in 10 days—work that usually takes 10 weeks, even under emergency conditions. The remarkable effort kicked off construction and enabled reopening of the highway in 80 days, instead of a more typical two years. By meeting the intense deadline, the team restored mobility to the region within three months, ending the 5-mile-long backups that snarled rush-hour traffic in the days following the closure. It re-established full service for 10 regional bus routes affected by the landslide, reinstating a dozen temporarily eliminated stops and reducing travel times that had escalated by 30 minutes or more.

What We Did

An unconventional design approach helped the team meet an aggressive schedule. Geotechnical engineers gathered as much subsurface condition data as they could as quickly as possible, based on visual observations and regional mapping. Designers then began their work, using data on-hand and prior experience with slide-prone landforms in the region. Analyzing new information as it came in and developing the design simultaneously allowed the team to achieve a successful solution in an exceptionally short period of time. At the team’s direction, excavators removed debris from specific areas to enable drill rigs to access nine core sample borings along an anticipated retaining wall alignment. Geotechnical engineers analyzed samples on the spot to determine how actual conditions aligned with the estimates. Data was conveyed instantly from the field to designers, who refined the design models as needed.

The team further accelerated the project by using geographic coordinates to define the retaining wall location, eliminating the need to wait for roadway alignment data, which likely would have taken surveyors a week to safely collect across the unstable ground. The bid package included design-build provisions for the contractor to perform these services once emergency crews removed the debris. This decision allowed the design to advance quickly, without putting surveyors at risk. The results of the team’s approach were astonishing: final structure design for a 400-foot retaining wall and construction details for a 90-foot embankment delivered in just 10 days.

Key Features

Details for excavation and benching to remove the landslide material and replace it with a durable 90-foot-high rock embankment.
Final structure plans for construction of a 400-foot-long, 20-foot-high anchored soldier pile and lagging retaining wall to support the embankment and protect nearby residences.
Special provisions needed for PennDOT to advertise the project for bid.

Awards & Recognition

Outstanding Environmental and Engineering Geologic Project Award, 2020, Association of Environmental and Engineering Geologists.
National Recognition Award, 2019, American Council of Engineering Companies (ACEC), Engineering Excellence Awards.
Outstanding Highway Engineering Award, Between $7 Million and $20 Million, 2019, American Society of Highway Engineers (ASHE) Pittsburgh Section.
Best Project, Small Projects, 2019, Engineering News-Record (ENR) Mid-Atlantic, Regional Best Projects.
Award of Merit, 2018, American Society of Civil Engineers (ASCE) Pittsburgh Section.
Emergency Remediation Project of the Year, 2018, Engineer’s Society of Western Pennsylvania (ESWP).