Construction on the tunnel shafts began in January 2018.
The tunnel-boring machine arrived at the site in multiple shipments throughout September and October 2018. It was then lowered into the tunnel in pieces and reassembled for operation. Boring of the 22-foot diameter tunnel, which is approximately 18 stories below ground, was completed in September 2020.
Currently, crews are forming a 1-foot concrete lining of the tunnel to prevent any water from leaking in or out to the environment and completing the drop shafts that will transfer the combined sewer overflows to the tunnel when operational.
When operational in 2022, the tunnel will store up to 55 million gallons of combined rainwater and wastewater when it rains.