AS1 Site
Site overview
The AS1 site is where construction of the main Ohio River Tunnel begins. It will serve as the launch point for the tunnel boring machine (TBM), the massive piece of equipment that will excavate the tunnel deep underground and will function as the primary construction hub for the project.
AS1 also plays an important role in the future regional tunnel system. It is planned to serve as the connection point for the future Allegheny River Tunnel and Monongahela River Tunnel, linking these systems to the broader regional tunnel network and making AS1 one of the most important locations in the overall system.
Work at AS1 includes relocating underground utilities, excavating a deep shaft, staging equipment and materials for tunnel construction, and supporting ongoing tunnel operations throughout construction.
Chestnut Street & Progress Street, City of Pittsburgh Directions: Google Maps Apple Maps
Beneath the surface
Go beyond the construction fence and explore the AS1 site.
Underground Cross Section
Cross-section illustration of the Ohio River Tunnel facilities underneath the AS1 site located near the intersection of Progress Street and Chestnut Street in the North Side. This is the main tunnel construction site, which features a vertical access shaft approximately 160 feet deep and 70 feet in diameter. The access shaft connects the Ohio River Tunnel, the Ohio River Tail Tunnel/Allegheny River Starter Tunnel, and the future Monongahela River Tunnel, located about 140 feet below ground surface. The image also shows surface buildings, streets, trees, and subsurface soil and bedrock layers to illustrate the local context.
Aerial Site Plan
Aerial site plan showing the location of the Ohio River Tunnel facilities underneath the AS1 site located near the intersection of Progress Street and Chestnutt Street on the North Side. The Ohio River Tunnel (ORT), approximately 150 feet below ground, is highlighted in green beneath the site. A drop shaft (70 feet in diameter) connects to the ORT, the ORT tail and start of the Allegheny River Tunnel and the start of the Monongahela River Tunnel. The site layout also shows the location of a new sewer, a construction area of approximately five acres, a building that will remain in place, and designated office and trailer parking areas. Nearby roads, railroad infrastructure, industrial buildings, and the Allegheny riverfront provide context for the tunnel construction site.
What to expect during construction
Nearby residents will likely experience construction impacts, such as intermittent noise during shaft excavation, potential noise from authorized night work, and increased truck traffic during specific phases of the project.
ALCOSAN is committed to working with residents and local businesses to minimize disruption and will be holding regular information sessions to inform residents on what to expect during each phase of the project.
Permitted work hours at this site will be:
General work hours*
- 6:00 a.m. and 8:00 p.m., Monday through Friday
- 7:00 a.m. and 8:00 p.m., Saturday and Sunday
*Impact construction activities, such as pile driving and jackhammering, are limited to 8:00 a.m. to 6:00 p.m., Monday through Saturday.
Extended hours for specific activities
Certain activities at the AS1 site will occur outside of the general work hours. These include:
- TBM tunneling and support activities: Tunnel boring machine operations and associated support activities may continue during extended hours.
What's happening at AS1
Closures, public meetings and construction updates for the AS1 site.
