Columbus construction crews achieved a massive breakthrough — quite literally — on Wednesday when an excavation machine penetrated the final stretch of a massive three-mile long sewer overflow tunnel.
The machine bored through a concrete wall at the bottom of a 50-foot hole near Tuttle Park just before 3 p.m. As the machine broke through with a loud bang, contractor crews and employees with Columbus Water and Power cheered from above the hole.
Columbus has been building the Lower Olentangy Tunnel for nearly four years. When complete in late 2026, the $250 million project will help prevent sewage overflow during increasingly common severe storms from polluting waterways like the Olentangy River.
The hole at Tuttle Park is at the end of a three-mile underground tunnel track following the river down to Vine Street near the confluence with the Scioto River. It connects along the way with sewer lines that flow between sewage lines and water treatment plants.
The hole is 12 feet in diameter and runs an average of 50 feet deep along its length.
The complicated system this tunnel is part of could help keep waterways clean during heavy rain storms that are more common now because of climate change.
It connects with seven Combined Sewer Overflow (CSO) structures located along the lower portion of the Olentangy River by relieving the Olentangy Scioto Intercepting Sewer. These CSO structures are located at First Avenue, Third Avenue, King Avenue, Indianola Avenue, Frambes Street, Doe Alley and Hudson Street.
Project manager Jeremy Cawley told WOSU that before a project like this came online, the heavy rain would cause sewer overflow to go into the Olentangy River, presenting problems with water pollution and water quality for the key source of the city of Columbus' drinking water.
"It'll be an overflow tunnel for the main trunks. And then we can hold it in the tunnel for a couple of days until the plant can handle it. Because that's usually what happens. The plants get overwhelmed and they just can't treat it all," Cawley said.
Cawley said the project went well and he was glad to work on it.
"This is the biggest project I've been on. It's actually, I think, the second largest the city's ever bid. So yeah, it's an honor to be on a project of this size," Cawley said.
Cawley said they nicknamed the project "Mighty Quinn."
When the machine broke through the concrete wall, rock flew into the base of the tunnel. The slow-moving, but powerful machine broke through the remaining parts of the wall and spewed a white liquid into the basin.
The $250 million project was funded mostly by city utility rates with help from Ohio EPA loans.
The city of Columbus is under two Ohio Environmental Protection Agency consent orders to improve water quality and reduce the potential for human contact with waterborne pollutants by reducing overflows from the sewer system into creeks and rivers during wet weather events.
The project was so large, the city constructed a railway track along the tunnel to help transport waste, materials and rubble.
Cawley said eventually the city could expand the tunnel further north by a few miles to the Clintonville area. He said the growth of the Columbus area, particularly the New Albany Intel plant, is creating the need for more projects like this.
He said this project will have at least a 100-year lifespan, if not more.
Cawley said once complete, the hole at Tuttle Park will have a concrete cap placed on top and the work area will be resurfaced partly as a parking lot near the Tuttle Park pool and more than 100 new trees will be planted over time.
