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Work began earlier this month on a billion-dollar tunnel project intended to reduce untreated sewage and stormwater in the region’s rivers — contamination that fouls waterways, threatens public health, and degrades habitat for fish and other aquatic life.
The Ohio River Tunnel is the first of three tunnels planned over the next decade, which are the centerpiece of ALCOSAN’s Clean Water Plan, a massive public works project expected to cost more than $4.5 billion. Contractors will begin at sites in Pittsburgh and McKees Rocks.
At the heart of the problem is the region’s combined sewer system. In many older communities, the same pipes carry both sewage from homes and businesses as well as stormwater from streets, roofs, and parking lots.
During heavy rain, the system can become overwhelmed, forcing a mix of stormwater and untreated sewage into rivers and streams.
Pittsburgh is not alone in its overflow problem. Cities and towns across the country, including Washington, D.C., and New York City, face similar challenges.
The Clean Water Plan, funded primarily by ratepayers, will reduce the overflow in Allegheny County.
The Clean Water Plan has several components: tunnels to capture overflows, expansion of ALCOSAN’s treatment plant, efforts to take over more municipal sewer infrastructure, and grants to help communities reduce stormwater before it reaches the sewer system.
ALCOSAN is building 16 miles of underground tunnels to capture overflows for treatment.
The basic idea is to create enormous underground storage capacity. Rather than allow overflows to discharge into waterways, the tunnels would hold the wastewater until it can be sent to ALCOSAN’s treatment plant.
In April, the sewer authority awarded a $1.1 billion contract to Brayman Construction Corporation and The Lane Construction Corporation, known together as Steel City Tunnel Partners, to build the Ohio River Tunnel. The Lane Construction Corporation is a subsidiary of Webuild Group, based in Milan.
So far, ALCOSAN has spent around $80 million on the tunnels. In total, they account for 70% of the Clean Water Plan’s budget.
The Ohio River Tunnel is the first test of whether that large-tunnel strategy can deliver the promised overflow reductions — and whether the region can manage the cost, disruption, and long construction timeline that comes with it.
ALCOSAN serves 83 municipalities in Allegheny County. That regional footprint is part of what makes the Clean Water Plan so complex: the authority treats wastewater from communities across the county, but much of the sewer infrastructure that feeds into its system is owned and maintained by individual municipalities.
Through a process ALCOSAN calls “regionalization,” the authority is asking municipal customers to transfer ownership of their sewer infrastructure.
The transfer is voluntary, but municipalities that choose to participate gain a key benefit: ALCOSAN assumes responsibility for maintenance, said Julia Spicher, manager of regionalization.
“Regionalization basically allows ALCOSAN to come in and take that burden off of the municipalities,” she said.
For municipalities, that can mean relief from the cost and technical challenges of maintaining aging pipes. For ALCOSAN, it can mean more direct control over the system feeding into its treatment plant — and greater ability to determine where repairs, upgrades, or eliminations of overflow points should occur.
The sewer authority has spent just under $26 million on regionalization since 2008, Spicher said.
Last fall, ALCOSAN increased its treatment capacity from 250 to 295 million gallons per day — an expansion it estimates reduced overflows by nearly 1,900 million gallons each year.
This matters because tunnels solve only part of the problem. Capturing more wastewater is useful only if the treatment plant can eventually process it. Expanding plant capacity is therefore another major component of the Clean Water Plan. Long term, the goal is to increase capacity to 600 million gallons per day.
Plant expansion has cost $382 million through March 2026.
ALCOSAN’s grant program, known as Green Revitalization of Our Waterways, or GROW, funds green infrastructure projects. These include municipal sewer separation projects in several places such as McKees Rocks, Braddock, and Crafton.
The renovation of water infrastructure at Squirrel Hill’s Wightman Park has received the largest share of GROW funds so far, at $3.3 million.
These projects are smaller than the tunnel system, but they aim to address the problem by keeping stormwater out of the sewer system in the first place. Green infrastructure can include projects that absorb, slow, or redirect rainwater before it overwhelms the pipes.
The sewer authority said it has distributed $43 million through GROW.
ALCOSAN said it has spent $750 million on the Clean Water Plan to date. In total, the cost of the plan has increased by more than $1 billion — from $3.6 billion to $4.5 billion.
John Detisch, of H2O Headwaters to the Ohio Water Network, commends efforts to reduce overflows but is concerned about ratepayers.
“It’s great, but we’re really putting a lot of pressure on people who can’t pay their bills now or are having a hard time paying their bills now,” Detisch said.
Since 2019, the average annual bill has increased from $381 to $612, KDKA reported.
What’s more, the Clean Water Plan will not solve the problem entirely, said Jonathan Burgess, director of the Pittsburgh Water Collaboratory at the University of Pittsburgh.
After the projects are complete, there will still be around 2 billion gallons of overflows discharged each year.
“We’re still going to be needing additional investments,” he said.
The Northeastern United States is projected to become wetter as climate change alters regional weather patterns. Yet ALCOSAN’s Clean Water Plan is based on 2003 rainfall data and may not fully capture more recent conditions, according to RAND’s 2017 study on stormwater management in the Pittsburgh region.
“I would say that stormwater managers nationwide are starting to incorporate future climate projections... but that this is not yet standard practice,” said Jordan Fischbach of The Water Institute, who led the study while working as a policy researcher at RAND.
ALCOSAN said 2003 was selected as the most representative year based on historical rainfall data. The authority added that it follows EPA guidance and has considered climate change in its infrastructure planning.
Hannah Frances Johansson is a reporter for the Pittsburgh Media Partnership newsroom. She holds a master's degree from the UC Berkeley Graduate School of Journalism. Reach her at hannah.johansson@pointpark.edu.
The PMP Newsroom is a regional news service that focuses on government and enterprise reporting in southwestern Pennsylvania. Find out more information on foundation and corporate funders here.
Header image: Bridge on June 2, 2026, as seen through the arch of Piazza Lavaro, an architectural facade at Allegheny Landing. Hannah Frances Johansson/Pittsburgh Media Partnership Newsroom
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