The Allegheny County Sanitary Authority has released new details about a 16.5-mile tunnel system to be built under Pittsburgh and the three rivers to better manage sewage and stormwater runoff. The system — which is part of the authority's $2 billion "Clean Water Plan" — aims to reduce sewage overflow by seven billion gallons per year.
“The newly constructed system will also stop sewage overflows to sensitive areas such as riverfront parks, marinas, recreational areas, boat launches and areas near drinking water intakes,” said Michael Lichte, the authority’s director of regional conveyance at a public meeting Wednesday.
The system is one component of the authority’s Clean Water Plan, which confronts the region’s need to upgrade infrastructure for waste and stormwater collection originally built in the 1950s. The system currently dumps about nine billion gallons of sewage and rainwater into local waterways every year.
The authority argues the tunnels would make their system more efficient and improve water quality. ALCOSAN plans to pay for it with a series of rate increases through 2036.
According to Kimberly Kennedy, the authority’s director of engineering and construction, customers will experience multi-year increases starting with a 7% jump for the years 2022 through 2026. “This year, the cost of the ALCOSAN wastewater treatment and conveyance services will be around $549 dollars [annually] for a typical residential customer,” she said. That averages to about $45.75 per month.
A subterranean waste network
The tunnel system is broken down into three main tubes named for the river they will be built along: the Allegheny River Tunnel, the Ohio River Tunnel and the Monongahela River Tunnel.
The first tunnel to be built will be the Ohio River Tunnel, which would run deep under parts of the North Side and I-579. Part of the tunnel would cross under the river at the West End and McKees Rocks bridges. The Ohio River Tunnel is expected to be completed by 2029.
The next two tunnels would push water toward the Ohio River Tunnel which leads to ALCOSAN’s wastewater treatment plant in Marshall-Shadeland.
In 2028, the authority plans to dig the Allegheny River Tunnel. It would crisscross under that river from Highland Park to Sharpsburg and through parts of Lawrenceville. It would eventually connect under Troy Hill, where it'd meet the nearby Ohio River Tunnel. The tunnel is scheduled to be completed by 2033.
Construction on the Monongahela River Tunnel is scheduled to begin in 2031. This tunnel would begin near the Glenwood Bridge in Hays and cross under the Monongahela River through parts of Hazelwood to the South Side. It'd eventually run beneath parts of Downtown and the Strip District before crossing the Allegheny River to the Ohio River Tunnel.
A spokesman for ALCOSAN noted that the route is subject to change. The tunnel system will be placed 150 feet below ground, which is 50 feet below the existing tunnels and 120 feet below the rivers.
The system will pass through nine municipalities and require surface construction in several. All nine municipalities must approve the amended plan. Etna Borough, West Homestead Borough, Millvale Borough and O’Hara Township have accepted, according to ALCOSAN.
Pittsburgh, McKees Rocks, Aspinwall and Shaler have not yet signed on, though ALCOSAN noted in its report that it has conditional support from the Hampton-Shaler Water Authority as long as the system doesn’t affect its well field adjacent to the Allegheny River.
It’s not yet clear where Pittsburgh and Aspinwall stand, but McKees Rocks is opposing the tunnel system. The borough sued the authority last year, alleging the system would place a large outflow near its business district. That case has since been moved to federal court and remains pending.
ALCOSAN declined to comment on proposed sites for sewage outflow, though the map shows a space for a “connector, consolidation or outfall sewer” at the area named in the lawsuit along West Carson Street.
At Wednesday’s meeting, ALCOSAN also explained how the project’s price tag went from $3.6 billion to $2 billion. The authority originally planned to have the tunnel system completed by 2026, but the new plan splits construction into two phases and extends the timeframe for phase one to 2036, which brought down costs.
The first phase includes the construction of the three tunnels and the new wet weather pump system at ALCOSAN’s wastewater treatment plant in Marshall-Shadeland.
“There will need to be a phase beyond 2036,” said Kennedy to address the remaining 2 billion gallons of sewage and rainwater that will still pour into waterways after the tunnel system is created.
“This was the compromise,” she said.
The public’s chance to weigh in
Members of the public have 30 days to submit comments on the proposals. ALCOSAN held two virtual public sessions to discuss the plan Wednesday. After a presentation by the authority, representatives from the nonprofit Riverlife and Pittsburgh United spoke in favor of the amendments.
“We’re hopeful that the investment contemplated is able to leverage additional resources and partnerships to ensure that these construction sites… can also be home to new improvements that benefit ratepayers in additional ways,” said Gavin White, Riverlife’s director of planning and projects. “To ensure that there are above ground benefits as well as those significant and important tunnels that you’re constructing.”
Riverlife released an extensive plan last week that would improve a 15-mile loop of trails and parks around Pittsburgh’s Golden Triangle. Several projects have timelines tied to ALCOSAN’s regional tunnel system.
Anna Coleman, an environmental justice organizer with Pittsburgh United, urged ALCOSAN to use every cent of the plan’s budget carefully and to be flexible as construction phases transpire over the next decade.
“This project represents one of the largest public works projects in our county’s history,” she said. “I’m also anxious to make sure that these funds are used as effectively as possible.”
Coleman stressed that the tunnel system planning must consider the future of Pittsburgh’s climate and how to make sure tunnels can manage even higher amounts of storm and wastewater.
“Rain generally, as well as extreme rain events, are likely to only worsen in the region due to climate change. So we just need a system that can adapt,” she warned.
Members of the public who wish to comment on the tunnel system can do so by emailing the authority or submitting a form on the ALCOSAN website.
