Residents in northwest Columbus might see relief for their sewer overflow issues starting in 2025 with the creation of a new sewer tunnel.

Columbus officials said they are working on finalizing plans for the Lower Olentangy Tunnel that will be operational by 2025.

The city plans to begin construction in 2021 of the $250 million Lower Olentangy Tunnel, a sanitary trunk sewer that is expected to improve the sewage situation. The project reportedly will start near Maynard Avenue in Clintonville and travel under state Route 315 and into downtown Columbus. It is projected to help prevent sewer overflows during heavey rains.

The project is expected to be finished in 2025, but the city is studying the Knolls and nearby areas to see whether short-term improvements are possible sooner.

The tunnel will help to improve overflows in the area, according to information from the city of Columbus department of public utilities.

Representatives from the Columbus Department of Public Utilities spoke during the March 4 Northwest Civic Association meeting.

John Newsome, division of sewerage and drainage administration, said the reason the sewer issues have taken so long to resolve is that the project was actually conceptualized in 2012.

He said a prior project, the Olentangy Scioto Intercepton Sewer Augmentation and Relief Sewer, also known as the OARS tunnel, had to be created before the Lower Olentangy Tunnel could be built and extended. It was completed in 2017

City records show the OARS tunnel is 20-foot-diameter, 4.5-mile tunnel. The $372 million tunnel is 180 feet below downtown Columbus and was designed to provide relief to the 80-plus-year-old Olentangy-Scioto Interceptor Sewer. The OARS tunnel extends from the Arena District to the Jackson Pike Waste Water Treatment Plant.

At a cost of $370 million, the OARS project is the largest capital-improvements project in the history of Columbus according to city officials.

"This, just thinking about it today, is probably the second-largest capital project " Newsome said of the lower Olentangy Tunnel.

He said residents should be getting some relief starting this spring and summer through a lining project of the area's sewers.

"We have a contractor that comes out and basically puts a pipe within a pipe," he said.

Newsome said this would help prevent a lot of water from infiltrating the sanitary sewer system.

He said Knolls and neighboring residents should not be worried about new development backing up sewers. He said the city has a complex model of how different developments would affect the city's sewer system.

For The Knolls in particular, he said the issue is with the sewer into which the neighborhood's lines tie in.

Nick Cipiti, chairman of the Northwest Civic Association board, said the flooding issue has been a "hot topic" among residents of the Knolls. He said residents have experienced sewer overflow and toxic waste backing up onto streets during periods of heavy rains.

For residents who have issues with basement flooding, Newsome said the city has a program called Project Dry Basement to help prevent sewer backflow for residents citywide, particularly after a rain event.

He said any residents experiencing issues with their basements should call 614-645-7102 anytime to report the issue.

Once the issue has been reported, the city will verify the property and cover the cost of a backflow-prevention device.