ALCOSAN advances Upper Allegheny Consolidation Sewer with $1.9M final design modification

ALCOSAN advances Upper Allegheny Consolidation Sewer with $1.9M final design modificationThe utility has extended its engineering contract with DLZ to navigate complex brownfield conditions and federal permitting for a deep microtunneling project designed to significantly reduce sewer overflows.

The ALCOSAN board approved a $1.9 million modification to DLZ's service authorization, extending the design and bidding support timeline by 18 months.

The project features 1.25 miles of consolidation sewer, to be microtunnelled at depths of 30 to 40 feet.

The new infrastructure is projected to deliver approximately 300 million gallons of overflow reduction.

Design complexities include expanded environmental boring at a former brownfield site and a pending Section 408 permit review by the U.S. Army Corps of Engineers.

The Allegheny County Sanitary Authority (ALCOSAN) board of directors has approved a $1.9 million contract modification for DLZ to complete final design and bidding support services for the Upper Allegheny Consolidation Sewer. The project, officially renamed from 'Allegheny River Tunnel Near Surface Facilities Package No. 6' during the June 25 meeting, is a major component of the utility's ongoing overflow reduction efforts. According to Director of Regional Conveyance Mike Lister, the project is expected to deliver approximately 300 million gallons of overflow reduction. The core infrastructure will consist of roughly 1.25 miles of consolidation sewer. Lister noted that the pipe will be installed via microtunneling at depths ranging from 30 to 40 feet. The $1.9 million modification, which extends DLZ's contract by 18 months through December 31, 2026, was driven by multiple scope changes and complex site conditions. ALCOSAN had to expand its environmental program and conduct additional soil borings to accommodate coordination with the Allegheny Shores development, a former brownfield site governed by state Act 2 environmental regulations. Additionally, the utility opted to advance a specific portion of the project near the Pittsburgh Water Treatment Plant to expedite overflow mitigation in that area, requiring a shift in the overall design schedule. The project's alignment also introduces federal regulatory hurdles. Because of the sewer's close proximity to the Highland Park Dam, Lister indicated that the design will require a Section 408 review process with the U.S. Army Corps of Engineers to verify the suitability of the plans. The contract extension is anticipated to carry the project through the completion of final design documents and an upcoming bidding phase, which the utility expects to initiate within the 18-month window. In a related effort to optimize system capacity and prevent river water intrusion, the board also authorized the preparation of bids for Contract 1844. That project will replace deteriorated and leaking flap gates and valves at multiple sites, including a large 96-by-84-inch gate at Adams Street and a 24-inch gate in Lawrenceville.