Pittsburgh, Pa.

Mt. Washington Landslide Mitigation

Client: City of Pittsburgh
Our Role: Design

Aerial view of a wooded hillside rising above riverfront highways and rail lines, with residential buildings along the ridge and fall foliage throughout the slope.

Pittsburgh is a city characterized by its iconic three rivers, deep valleys, and steep hills. The city’s Mt. Washington neighborhood is situated on steep urban hillsides defined by cyclical layers of sedimentary geologic deposits including low-strength claystone bedrock, making the terrain highly sensitive to development, groundwater fluctuations, and freeze-thaw cycles. Landslides in the area threatened roadways, including emergency access routes, along with utilities, and hillside residences in a highly populated urban setting. Recurring landslides increased public safety risk and emergency response costs. The City of Pittsburgh sought a resilience solution to stabilize high-risk corridors, reduce long-term geotechnical risk, and protect critical transportation infrastructure in this dense urban setting.

This resilience initiative, led by the City of Pittsburgh Department of Mobility and Infrastructure and funded by the Federal Emergency Management Agency (FEMA) through the Pennsylvania Emergency Management Agency (PEMA), addressed three geologically unstable corridors within Mt. Washington:

William Street.
Greenleaf Street.
Reese Street.

GFT delivered geotechnical and roadway design services to stabilize steep slopes under constrained urban conditions. Each corridor required tailored solutions based on subsurface conditions, depositional history, limited access, and neighborhood impacts.

Our team designed integrated slope stabilization systems to arrest slope movements and restore public infrastructure tailored to the site’s steep slopes and limited footprints. Geotechnical treatments included:

Ground improvement by deep soil mixing to increase the in-situ strength of deep, ancient landslide soil deposits.
Soil nail reinforcement with high-strength steel mesh to restore roadway failures and support trail reconstruction.
Geogrid reinforced soil slope construction to re-establish trail passages.
Rock buttresses to stabilize active slides.
Mine void grouting with video verification to prevent surface subsidence.
Rock scaling to reduce future rockfall hazards.
Drainage improvements to collect seepage and reduce soil saturation.
Plantings and erosion control improvements to support regrowth.

Key structural system elements included:

Drilled shafts.
Soldier beam and lagging retaining walls.
Rock anchors.
Micropiles.

The work was delivered between 2023 and 2025 while keeping local circulation open, limiting neighborhood disruption and maintaining emergency services and adjacent residents’ access under constrained urban conditions.

Key Features

Stabilization of three landslide corridors within the Mt. Washington neighborhood.
Integration of multiple geotechnical systems under constrained urban conditions.
Restoration of roadways, emergency access routes, and park trails.
Drainage, erosion control, and rockfall mitigation to reduce future risk.

Outcomes

Returns critical infrastructure assets to safe, functional public use.
Protects homes, streets, trails, utilities, and emergency routes.
Reduces long-term geological risk and future emergency response costs.
Supports long-term community mobility, resiliency, and public safety.
Engineers’ Society of Western Pennsylvania, 2025, Outstanding Project — Geotechnical.