By rosebell
The Allegheny County Sanitary Authority (ALCOSAN) has broken ground on the Ohio River Tunnel (ORT) in Pittsburgh, Pennsylvania, marking the start of a major wastewater infrastructure project aimed at reducing sewer overflows during wet weather.
Steel City Tunnel Partners, a joint venture between Lane Corporation and Brayman Construction Corporation, is delivering the project under a US$1 billion contract. Initial work will focus on constructing access shafts ahead of the planned arrival of the tunnel boring machine (TBM) in late 2027. Eight construction sites are planned along the tunnel alignment.
The main tunnel will extend approximately 6km from Pittsburgh’s North Shore to ALCOSAN’s wastewater treatment plant. It will have a diameter of 5.5m. Including smaller connecting tunnels, the project will involve nearly 8km of excavation, with connections designed to capture wastewater flows from the Saw Mill Run and Chartiers Creek areas.
The Ohio River Tunnel is the first component of ALCOSAN’s Regional Tunnel System, which is designed to capture excess wastewater during wet weather and convey it to the treatment plant for processing. The system forms a central part of the authority’s multi-billion-dollar Clean Water Plan to modernise regional wastewater infrastructure and improve water quality.
The ORT will also serve as a connection point for two additional planned tunnels: the Allegheny River Tunnel (ART) and the Monongahela River Tunnel (MRT).
The approximately 10km-long ART remains in the design phase, with design completion expected in late 2027 or early 2028. The nearly 7.5km-long MRT is at the early conceptual planning stage.
Together, the three tunnels are intended to strengthen the region’s wastewater management capacity and help reduce overflows into local waterways during periods of heavy rainfall.
