Built around 1900, the oldest sewers in greater Cleveland carry sewage, stormwater, and industrial waste in a single pipe. More than 60 times a year, after heavy rainfall, sewers in the Euclid Creek area overflow, threatening the quality of waterways.
The Mill Creek Tunnel was built as part of a major project to reduce the number of combined sewage overflows (CSOs). However, the tunnel project was plagued by cost overruns and allegations of corruption in the sewer district.
In 2010, the sewer district reached agreement with the US and Ohio EPA and the US Department of Justice on a new plan to meet the requirements of the Clean Water Act over a period of 25 years.
The Euclid Creek Tunnel is the first of seven planned storage tunnels that will relieve overflows in the Cleveland sewer system. (See video.) According to the Northeast Ohio Regional Sewer District (NEORSD), the tunnel will be able to hold about 70 million gallons of combined stormwater and wastewater. After each heavy rain, the combined sewage will be pumped to the Easterly Wastewater Treatment Plant.
Located 190 to 220 feet below ground, the tunnel will be 18,000 feet long and 24 feet in diameter. About 3,000 feet of the tunnel will pass underneath Lake Erie. A tunnel boring machine (TBM) known as Mackenzie is boring through shale to create the tunnel.
Mott MacDonald is the lead consultant responsible for overall project management, overall project administration, TBM specifications, and design of the tunnel lining, ventilation, and other aspects of the project.
Mott MacDonald introduced several key innovations:
- Bolted, gasketed, precast concrete segments are being used to build the tunnel. The use of concrete segments in rock is rare, and few if any projects have used them in shale.
- The concrete segments are reinforced with steel fiber instead of rebar, another feature that is rare in the US.
- A two-part grout system is being used that may be the only one of its kind in the world. In order to fill the space between the concrete segments and the rock wall, grout is being injected through the tail of the TBM.
Our work on the tunnel required a successful collaboration between contractor, machine supplier, grouting specialists, and others.
The use of steel-fiber-reinforced concrete segments cut four months from the construction schedule and saved the sewer district considerable costs. The sewer district plans to use similar techniques for its Dugway tunnel, for which Mott MacDonald is considering the use of plastic fiber instead of steel — a potential world first.
Our design enabled one-pass construction of the tunnel, reducing risks due to overbreaks and mine stoppages, decreased infiltration, and an increase in quality and safety. The contractor was able to bore the tunnel at rates of up to 110 to 130 feet per day.
When the tunnel is complete in 2015, it will prevent millions of gallons of overflow sewage from reaching Euclid Creek and Lake Erie, helping safeguard public health and the environment in the greater Cleveland area.