Pre-construction activities begin on the Ohio River Tunnel project in Pittsburgh
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Advancing clean water infrastructure in Pittsburgh
Pre-construction activities have started on the Ohio River Tunnel (ORT) project in Allegheny County, Pennsylvania, following the award of the over $1 billion construction contract to Brayman-Lane JV. The ORT is the first of three tunnels planned under the Allegheny County Sanitary Authority’s (ALCOSAN’s) Clean Water Plan, developed to meet compliance with the federal Clean Water Act. Once the Clean Water Plan improvements are complete, the system will reduce combined sewer overflows (CSOs) by seven billion gallons annually and eliminate sanitary sewage overflows for 83 Allegheny County communities, including the City of Pittsburgh.
Providing innovative solutions to meet complex needs
As the prime design consultant, we leveraged our global team of multidisciplinary experts to deliver ALCOSAN’s first regional wet weather tunnel design. We provided hydraulic modeling and design, site/civil planning and design, electrical design, 3D modeling, geotechnical exploration and reporting, structural design, surveying, permitting, easement documentation, public outreach, and tunnel, shaft and near-surface facility design. We collaborated closely with ALCOSAN throughout the design process, sharing our collective expertise in tunnel engineering, water resources, environmental permitting, and project management from similar projects, like Thames Tideway in the UK and Project Clean Lake in Cleveland, Ohio.
The ORT comprises 4.9 miles (7.9 km) of segmentally lined deep rock tunnels with diameters of 14 to 18 feet (4.3 to 5.5 m), as well as eight deep shafts and several smaller connector tunnels. We performed a comprehensive geotechnical investigation program and undertook detailed hydraulic design for the project. Permitting and environmental work was extensive; we interfaced with numerous municipal, county, state and federal regulatory agencies and utilities to prepare and submit over 100 permit applications. Our team has also been proactively involved in community outreach, developed four separate early action bid packages for the demolition of existing structures and initial site preparation, along with the development of a robust plan for management of excavated materials.
Looking ahead
The ORT sets a precedent for the next two tunnels in ALCOSAN’s Clean Water Plan. Our work demonstrates how major wet weather infrastructure can be advanced in a dense urban environment through disciplined coordination and excellent design.
Kim Kennedy, PE, director of engineering and construction at ALCOSAN, said, "We are incredibly pleased with Mott MacDonald’s design of the ORT, and all the work associated with it."
Construction of the ORT will continue through 2032, followed by construction of the Allegheny River Tunnel and the Monongahela River Tunnel. Together, this three-tunnel system will protect sensitive riverfront areas, eliminate CSOs at various outfalls and improve water quality for Pittsburgh and the surrounding communities.
