In Greater Cleveland, crews have reached a milestone on one of the final tunnels connected to the $3 billion Project Clean Lake program. The Southerly Storage Tunnel is a massive deep-rock infrastructure project measuring 18,100 ft. long and 23 ft. wide.
“It's very exciting to see them get past the halfway point,” Northeast Ohio Regional Sewer District (NEORSD) project manager Doug Lopata, told Construction Equipment Guide. “It's a massive project, and I'm glad to see the tunnel boring machine [TBM] is working well on its second project in the NEORSD program. These projects are impactful to the community during construction, and afterwards with the water quality benefits to the region.”
Project Clean Lake is a combination of large tunnels, treatment plant improvements and expansion and green infrastructure designed to reduce the volume of combined sewer overflow discharging to Lake Erie. The program was launched by NEORSD in 2011 to meet Clean Water Act standards established to protect the lake from billions of gallons of raw sewage and overflow.
Work on the Southerly Storage Tunnel and Consolidation Project (SOTC) started in early 2024, with the tunnel portion scheduled to be finished in early 2028. The follow-on pump station project, which is needed to activate the system, should be completed in 2030.
“The project was bid at $328 million, and the pump station is out to bid now at $71 million,” said Lopata. “The main consolidation sewer project was also bid at $103 million. The total program is funded entirely by the rate payers of northeast Ohio.”
The project will hold 63 million gal. of sewage during a storm event that would have polluted the Cuyahoga River. Over a typical year, the tunnel, pump station and consolidation sewer system will capture and treat 760 million gal.
McNally Tunneling Corporation of Westlake, Ohio, is the SOTC contractor. According to Lopata, crews have literally had their work cut out for them.
“The SOTC project is our second large diameter soft ground project. The other large tunnels have been in shale/rock. The soft ground is a challenge to control pressures in front of the TBM, and to not let the TBM remain stationary for the ground to squeeze around it. The soft ground material is also harder to manage on the surface and dispose of, as it's the consistency of toothpaste.”
The concrete tunnel segments are almost complete. The shafts and diversion structures are nearly excavated to make the future connections to The Burke Brook and Morgan Run Culverts.
TBM tunneling and shaft work continues at sites 2 and 3, as well as excavation around the 100-year-old Southerly Interceptor in East 49th Street. Setting a flume pipe to maintain sanitary flows to the plant is also required to allow a 72-in. micro tunnel to be installed to connect the interceptor to the Southerly Tunnel.
“The site work is all being done to facilitate the tunnel and shaft excavation,” said Lopata. “Site work will move into restoration after the large cast-in-place concrete structures are complete in 2027, and the sites are turned over to other contractors.
“Completion of the second half of the tunnel by early 2027 is the critical path. The cast-in-place structures are very complicated to construct on the way up and out of these deep excavations.”
Lopata said working on an underground storage tunnel designed to capture and hold combined sewer overflows during heavy storms requires a great deal of focus.
“Work safety in a tunnel is always most important. This involves running three shifts during tunneling, while trying to keep the TBM productive and managing the large volume of tunnel muck for disposal. This project also has very deep connections to the existing culverts that were buried many years ago.”
The tunnel will generate 355,919 cu. yds. of material. The four shafts total more than 60,000 cu. yds. of spoils.
Large cranes are being used at the job site, along with conveyor systems, excavators to load dump trucks, large slurry wall and secant pile equipment, excavators and cranes to dig the shafts, a 72-in. micro tunnel machine and the 300-ft. long TBM.
“This was the same TBM that constructed our Shoreline Tunnel, but the contractor made some improvements to the system,” said Lopata. “It's working very well and includes over 300 ft. of trailing support gears for grease, grout, ventilation, survey guidance and other support equipment to keep the machine moving forward, and segments being built behind the TBM. The cutter teeth are not showing much wear through the halfway point in the clays/silty ground. They have ingested some small boulders and rocks thus far.”
Lopata explained that lowering the 800-ton structure down the tunnel shaft is no small feat.
“This process is very tedious and takes a lot of preparation and calculations by the contractor and their specialty lift subcontractor. It can really only be described with a picture of the TBM lifted over the shaft, and it takes about a day to slowly and gently lower it down 180 feet and move it into position.”
Lopata also noted that Ohio weather can be challenging for crews.
“The winters can make the tunnel process difficult with the conveyor system and anything involving water freeze. The contractor has to build some extra enclosures for the winter or provide some protection for their workers to get production during the cold Ohio winters.
“Also, the cranes have to lower for lightning, but the tunnel is a pretty constant 50-degree temperature once you get down there.”
Big Creek Storage Tunnel (BCT) is the last of the seven large-diameter combined sewer overflow (CSO) storage tunnels that will help reduce 4.5 billion gal. of CSO released into Lake Erie and other local waterways. This final project will have a notice to proceed in late 2026.
“It will run approximately four years before a follow-on consolidation project will finish the BCT system by 2032,” said Lopata. “This would signify the completion of a nearly 25-year program of CSO control that was built ahead of schedule and under budget for the northeast Ohio region.
“These last two tunnels are a little further upstream on the Cuyahoga and Big Creek watersheds, but they still make a big impact on the water quality that the communities will see. Ultimately, the water gets back into Lake Erie and will make for a cleaner recreational environment and drinking water source.”
Lopata acknowledged the overall project can be overwhelming at times, but the accomplishments can't be overstated.
“We are over three-fourths through the program. We're happy to report we are ahead of schedule and under budget. As we go forward, the challenges move to our O&M team to operate all the new facilities and keep the treatment going longer at each plant.”
