The regional tunnel system is a critical component of the Clean Water Plan aimed at improving and protecting the water quality of the region’s streams and rivers. Watch the video or read more to learn about the system and its benefits!
The new regional tunnel system will capture wet weather combined sewer flows and move them to the plant for treatment. It will consist of three major tunnel projects. The Ohio River Tunnel (ORT) project is the first of the three projects. The other two projects are the Allegheny River Tunnel (ART) and the Monongahela River Tunnel (MRT). The ORT will be implemented concurrent with the new Wet Weather Pump Station.
Learn More about the Allegheny River Tunnel project
Learn More about the Ohio River Tunnel project
Coming Soon
The proposed facilities will tie to the existing combined sewer system and divert excess wet weather flows away from the outfalls, moving them instead to the treatment plant.
The facilities will include:
Most infrastructure will be below ground with tunnels sitting at about 120-150 feet below ground.
The new facilities will include over 16 miles of wet weather tunnel, 40 regulators, and 31 shafts as well as about 4 miles of consolidation sewer. These facilities will connect to the existing combined sewer system, which includes similar facilities consisting of approximately 31 miles of deep tunnel interceptors, over 200 combined sewer regulators and associated shafts, and 13 access shafts.
Regulators are underground structures that are built along existing sewers to control where sewage is sent. Regulators allow normal dry weather flow to continue to the existing sewer network but during wet weather they divert flow to drop structures and into the tunnel via consolidation sewers.
It is anticipated that these regulator structures will be sized from 6-feet by 12-feet to 28-feet by 50-feet.
Consolidation sewers are anticipated to range between 24-inches and 144-inches in diameter with depths ranging between 10-feet and 50-feet below ground. Depending on conditions at the location the consolidation sewers could be built using micro-tunneling techniques or an open-trench approach.
Drop shafts are deep, vertical structures that transfer the combined sewage from the surface to the tunnels.
Their design includes hydraulic structures to manage the flow as it drops and to dissipate the energy generated to prevent damage to the drop shaft and the tunnels. The drop shafts are anticipated to range between around 15 feet and 50 feet in diameter depending on location.
The size of the construction area depends on the diameter of the drop shafts. Typically, an acre is required for safe and efficient construction.
After construction, once the hole is covered, only access for maintenance activities is required.
The new deep tunnels are underground structures designed to convey the combined sewage from the drop shafts to the new wet weather pump station for treatment at ALCOSAN’s wastewater treatment plant (WWTP) during wet weather events. At times the tunnel system will temporarily store excess flow until it can be treated at the WWTP.
The main tunnels will primarily be constructed using large tunnel boring machines (TBM) that will be lowered from the surface and later retrieved via construction shafts.
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The FAQs above include the most common questions we receive about the Regional Tunnel System, but there's much more to explore! Explore our additional FAQs and see how the Clean Water Plan is making a difference in your community.