The Allegheny County Sanitary Authority (ALCOSAN) has broken ground on the Ohio River Tunnel, the first project in a planned three-tunnel system to reduce wet-weather sewer overflows. 

The tunnel is intended to reduce sewer overflows by seven billion gallons annually by directing excess flows to ALCOSAN’s treatment plant for processing, according to the authority. 

This 4.9-mile project will include six construction sites in Pittsburgh and two in McKees Rocks. Its main section will run from the North Shore to the treatment plant, with connecting tunnels collecting flows from the Saw Mill Run and Chartiers Creek areas. 

Steel City Tunnel Partners, a joint venture (JV) between The Lane Construction and Brayman Construction, will begin drilling access shafts at the construction site, with a tunnel boring machine expected to arrive late next year. 

In June this year, the JV secured a $1bn contract to construct the first major tunnel for the Ohio River Tunnel. 

ALCOSAN executive director Arletta Scott Williams said: “This groundbreaking is more than the start of construction. Reaching this day required grit, determination, and commitment from countless people.  

“Today is a day to celebrate, but we also know there is work ahead. We have the people, the expertise and the resolve to carry us through the next phase, and I am incredibly proud of the work that’s been done to get us here.” 

The Ohio River Tunnel forms part of ALCOSAN’s Regional Tunnel System, which also includes planned tunnels along the Allegheny and Monongahela rivers.  

The authority includes the system in its Clean Water Plan, alongside treatment plant expansion, regionalisation and green infrastructure delivered through its GROW programme. 

Recently, ALCOSAN increased its wet-weather treatment capacity to 480 million gallons per day, meeting a key compliance requirement under its Consent Decree. 

The expanded capacity is expected to reduce overflows by a further 3.4 billion gallons annually.