By Sean P. Ray | Managing Editor

As Allegheny County Sanitary Authority (ALCOSAN) gets closer to when it will begin boring underground across Pittsburgh for its new regional tunnel system, the municipal organization is taking the time to inform Northsiders on what they can expect once the first phase of the project begins in 2025.

ALCOSAN held a public meeting on Jan. 30 at Allegheny Center Alliance Church to detail the upcoming Ohio River tunnel project, as well as the future of the overall regional tunnel system construction. While The Chronicle was unable to attend the meeting due to overlap with the February edition deadline, ALCOSAN Director of Engineering and Construction Kimberly Kennedy and Director of Operations and Maintenance and Deputy Executive Director Douglas Jackson spoke with The Chronicle over a video call to review the information presented at the meeting and answer questions.

The regional tunnel system is part of an effort by ALCOSAN to comply with a consent decree originally established in 2008 with the Environmental Protection Agency to adhere to federal regulations and reduce the amount of sewage overflow the authority is currently dumping into Pittsburgh waterways.

Jackson said in a year with typical rainfall, ALCOSAN discharges around 9 billion gallons of undiluted sewage into the environment. ALCOSAN’s current piping system in the City of Pittsburgh is unable to handle much rainfall or snowmelt, with Jackson saying as little as one-tenth of an inch of rain being enough to cause an overflow and causing undiluted, untreated sewage to spill into rivers and streams.

The new tunnels are intended to be able to catch excess water whenever the main pipes overflow due to rainfall, snowmelt or similar occurrences. While the tunnels won’t completely eliminate untreated sewage discharges, ALCOSAN is attempting to reduce the amount of discharges to around 3 billion gallons. “The goal isn’t to go to zero,” Jackson said. “You can’t address every rain event.”

The new tunnels will follow ALCOSAN’s existing water system, which straddle Pittsburgh’s three rivers. Kennedy said the tunnels will be 150 feet underground, though there will be a surface access shaft located on the Northside — specifically in the vicinity of South Canal Street — during construction. While that will mean an open pit in the ground during construction, Kennedy said the area will be restored afterwards, save for a manhole or similar surface access area for any future maintenance.

The boring will be done in three phases, starting with the Ohio River tunnel in 2025 and running through 2029. Starting from the Northside access shaft, ALCOSAN’s contractor will dig underground to McKees Rocks, where a second access shaft will be dug.

The second phase of construction, the Allegheny River tunnel, will start in 2028. As before, ALCOSAN’s contractors will begin at the Northside access tunnel and instead dig along the Allegheny River, cutting through Etna and Sharpsburg and ending across the river from Aspinwall.

The final stage, the construction of the Monongahela River tunnel, will occur from 2030 to 2036. The consent decree requires that ALCOSAN be finished by 2036. Even after the project is finished, ALCOSAN will not be in compliance with federal regulations, and further improvements will be necessary after 2036.

While digging for the Ohio River tunnel is technically supposed to start next year, Kennedy said it may be some time off. The massive drills used for such a construction will likely take a year and a half to deliver once ordered, and ALCOSAN has yet to go to bid for the project.

“We will go to bid, even if it’s late this year, we will go to bid in 2024,” she said.

Despite the size of these drills, Kenendy said they only have a lifespan of around 5 miles, so the same drill cannot be reused on a different tunnel.

Kennedy said Northsiders will hear noise from around the access tunnel while construction is taking place. However, she said they shouldn’t expect to start smelling raw sewage in the area.

“The odors will be much less of a concern,” she said. “By the time the flow gets to this tunnel, it’s pretty diluted.”

Further, construction will have some impact on the Allegheny River part of the Three Rivers Heritage Trail during construction and some detours may have to be posted, but residents will never lose access to the trail. She also said ALCOSAN is not planning to demolish 855 South Canal St., a building located within ALCOSAN’s planned construction area for the Northside access shaft, which the authority is seeking to seize through eminent domain.

Otherwise, however, Kennedy said there will be no above ground construction as part of the project and there will be little sign of the drilling actually occurring.

“Nobody is going to see that,” she said. “Nobody is going to know where that boring machine is on any given day.”

The tunnels are not the only project ALCOSAN is undertaking to address the raw sewage discharge. The authority is also seeking to increase the amount of sewer lines it is responsible for connecting to their system — as many are overseen by various municipalities instead of by ALCOSAN — and it is undertaking a roughly $500 million expansion of its treatment plant to increase the amount of water it is able to process in a day.

According to Jackson, the treatment plant expansion would increase the daily treatment capacity from 250 million gallons per day to 600 million gallons per day. This will accommodate the increased flow from the additional tunnels being dug.

Finally, ALCOSAN is investing $90 million into the Green Revitalization of Our Waterways (GROW) program to reduce excess water from already entering the sewer system.

Residents interested in learning more about ALCOSAN and its plans can do so either at their contractor outreach event taking place on May 2 at Sheraton Station Square or at the ALCOSAN treatment plant’s open house, taking place on Sept. 14.