ALCOSAN advances major sewer projects targeting 550 million gallons in CSO reduction
Allegheny County Sanitary Authority, Pennsylvania · Meeting date: June 11, 2026 · Published: June 15, 2026
The utility's Professional Services Committee approved a $1.9 million design modification for the Upper Allegheny Consolidation Sewer and shortlisted three engineering firms for the Scully Yard Relief Sewer design.
Key points
- A $1.9 million design modification was approved for DLZ to finalize plans for the Upper Allegheny Consolidation Sewer, extending the contract by 18 months.
- The 72-inch Upper Allegheny sewer will capture 300 million gallons of combined sewer overflows, navigating complex brownfield conditions at the Allegheny Shores development site.
- HDR, Wade Trim, and WRA were shortlisted from 11 interested firms to design the Scully Yard Relief Sewer.
- The Scully Yard project will alleviate a choke point in the Chartiers Creek interceptor, enabling an additional 250 million gallons of flow to reach the treatment plant.
Full report
The Allegheny County Sanitary Authority (ALCOSAN) Professional Services Committee moved to advance two critical conveyance projects on June 11, 2026, targeting a combined 550 million gallons in annual combined sewer overflow (CSO) reductions.
The committee recommended a $1.9 million modification to DLZ’s service authorization for the final design and bidding support of the Upper Allegheny Consolidation Sewer. The project involves 1.25 miles of 72-inch diameter shallow consolidation sewer designed to capture overflows from Sharpsburg to the Allegheny River Trail Park in Aspinwall. According to Director of Regional Conveyance Michael Liscia, the completed project will reduce CSOs by approximately 300 million gallons.
The design modification, which extends DLZ's contract by 18 months through the end of 2026, was driven by significant scope adjustments since the project launched in 2023. Liscia noted that the sewer alignment runs directly through the Allegheny Shores development, a 52-acre Act II brownfield site in Sharpsburg, requiring expanded environmental and drilling programs. The scope also included the accelerated $2.5 million Aspinwall sewer replacement, which was completed in early 2025 to address ongoing overflows and backups. The additional funding will take the project through biddable plans by the fall of 2027.
In a separate action, the committee approved a shortlist of three engineering firms—HDR, Wade Trim, and WRA—for the Scully Yard Relief Sewer design. The firms were selected from a pool of 11 interested bidders. The project will address a choke point in the lower Chartiers Creek interceptor system located near a former rail yard in the Wind Gap and McKees Rocks area.
Once ALCOSAN’s treatment plant is expanded to a capacity of 480 million gallons per day, the new relief sewer will direct considerably more volume to the facility. Liscia estimated that the project could reduce overflows by up to 250 million gallons in a typical year.
Additionally, the committee recommended a $377,800 service authorization for Rios Williams Architects to design process area upgrades at the main facility. Director of Engineering and Construction Kim Kennedy stated the scope includes designing two new truck scales in the sludge processing building, upgrading three aging elevators across multiple processing buildings, and repurposing existing spaces into women's locker rooms. The upgrades are expected to conclude in the first quarter of 2028.
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Source: Professional Services Committee, Allegheny County Sanitary Authority