Photo courtesy of Thomarios/City of Akron
The city worked closely with officials to reduce environmental impact to the park’s natural features by optimizing design of the project to reduce tree clearing and impact to key features.
Construction crews in Ohio are tackling a multi-year sewer project that involves building a 16.5-ft. internal diameter tunnel. Work on the city of Akron's $215 million Northside Interceptor Tunnel (NSIT) assignment began in fall of 2023.
"The tunnel will reduce combined sewer overflows to the Cuyahoga River, which will improve water quality in Akron," said city of Akron senior engineer Heather Ullinger. "This benefits the local community and the adjacent and downstream communities, including Cuyahoga Falls, the Cuyahoga Valley National Park, Cleveland and Lake Erie.
Photo courtesy of Thomarios/City of Akron
"The improvements made by the Akron Waterways Renewed Program have dramatically improved water quality for our region. The tunnel also will replace a major portion of the city's Northside Interceptor sewer, which was built more than 100 years ago."
The NSIT undertaking is one of the final projects of the EPA-mandated consent decree, entered in 2014, to improve the city's sewer infrastructure and reduce combined sewer overflows (CSOs). The tunnel will collect and store CSOs from four overflow locations. It will be 6,660 ft. long, more than 100 ft. below ground in rock and will be able to store more than 10 million gal. of combined flow.
The design for the tunnel was completed in early 2023.
"The most detailed element is the tunnel diversion structure [TDS]," Ullinger said. "This is the heart of the project. It's the downstream end of the mainline tunnel and receives flow from the Rack 32 consolidation sewer. The TDS conveys dry weather and typical year flows to the existing interceptor sewer to dewater the tunnel. It includes floatable screening and baffle drops to slow flows."
Because of the deadlines set in the federally-mandated decree, the project schedule is aggressive.
"From a construction standpoint, the project involves about 2,500 feet of a soft ground tunnel," said Ullinger. "Access to the shaft location and geotechnical conditions for this consolidation sewer are challenging. This is happening right alongside another major, multi-stage project, the Gorge Dam removal. Coordinating the two requires daily communication and teamwork."
To determine underground conditions, officials implemented an extensive geotechnical program which started in 2020. Currently, crews are preparing the site by stripping topsoil and grading in the area of the TDS. Tree removal is complete and utility relocation continues.
No blasting is anticipated; however, to reduce the impact of the project, the city of Akron decided to keep all spoils from tunneling and other earthwork on-site permanently.
"This requires a sophisticated work plan for the project's main staging area to ensure there's enough room for the stored materials and day-to-day operations. The project is occurring in a Summit Metro Park, with beautiful views of the Cuyahoga River."
The city worked closely with officials to reduce environmental impact to the park's natural features by optimizing design of the project to reduce tree clearing and impact to key features.
Ullinger noted that more than 150,000 cu. yds. of tunnel muck and excavated material will be placed adjacent to the construction site, reducing hauling mileage and providing an environmental solution.
Crews also must monitor outdoor conditions.
"Inclement weather, such as heavy rain, snow or extreme heat, can lead to delays with NSIT," said Ullinger. "Wet or frozen ground can be challenging to work with, making excavation, concrete placements and concrete curing problematic."
Equipment on site includes a Cat 470G excavator; Terex TA30 articulating dump truck; Dynapac rubber tire smooth drum roller; Cat 950 loader; Komatsu 65PXi bulldozer; four Komatsu HM300 articulating dump trucks; a Cat CP-563E sheepsfoot roller; woodchippers and bulldozers.
Photo courtesy of Thomarios/City of Akron
Overseeing construction of a 16.5-ft. internal diameter tunnel is demanding, but not overwhelming, according to Ullinger.
"The city is experienced in managing large, challenging projects. We have completed 24 out of 26 projects in our federally-mandated consent decree, which have cost almost a billion dollars."
Once construction is completed, Akron will reportedly reduce CSO and water reclamation facility secondary bypass by more than 2 billion gal. The city will be capturing and treating 99 percent of wet weather flows and reducing the number of CSO events by almost 100 percent.
Funding for the project will be awarded through Ohio EPA's Water Pollution Control Loan Fund (WPCLF). Additionally, the city has worked with Ohio EPA and partners across the state to sponsor more than half-a-dozen projects that serve to protect valuable habitat and water resources.
Thomarios is the construction manager of the project, while Granite Construction Company serves as the contractor.
"Members of the Granite team were involved in construction of the city's first tunnel," said Ullinger. "They have local experience and relationships that will contribute to the project's success."
Ullinger said that while the project is far from glamorous, it serves a critical need.
"Sewers are essential to every community, but they're not like other infrastructure improvements, which can be easily seen. The improvements we see and celebrate are the water quality benefits, which are highlighted in our local and regional parks, trails and greenways." CEG
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