City Plans Tunnel Project to Combat Sewer, Stormwater Overflows

Planning is now underway for a $244 million, 1.2-mile tunnel system, pump station and enhanced high-rate treatment facility in Cincinnati, OH, that could reduce the mixture of sewage and stormwater that enters local waterways, improving the quality of life for the more than 2 million people living in the metropolitan area.

Planning is now underway for a $244 million, 1.2-mile tunnel system, pump station and enhanced high-rate treatment facility in Cincinnati, OH, that could reduce the mixture of sewage and stormwater that enters local waterways, improving the quality of life for the more than 2 million people living in the metropolitan area.

Black & Veatch is designing the Lower Mill Creek Tunnel that could be a part of the Metropolitan Sewer District of Greater Cincinnati's Project Groundwork, a multi-billion dollar and multi-year public works program that will reduce combined sewer overflows by 85 percent and eliminate all sanitary sewer overflows.

The Metropolitan Sewer District is also exploring alternatives or supplements to the tunnel, such as source control solutions, stormwater detention basins, rain gardens and stream separations.

"Tunnels are an inherently sustainable design method for capturing combined sewer and sanitary sewer overflows," said David Egger, Vice President and Heavy Civil Lead in Black & Veatch's global water business. "Because the majority of construction takes place deep underground, there are fewer disturbances and delays to the local community when compared with open cut, or 'trenched,' construction methods."

In metropolitan communities across the country, sewer overflows occur when there is too much water for the existing infrastructure to handle, usually during or after a heavy rainstorm. To relieve pressure in the system and minimize backups into homes and businesses, excess sewage is discharged into local waterways. Tunnels provide wastewater and stormwater utilities with additional holding capacity to significantly reduce or eliminate overflow discharges.

"Tunnel design and implementation for reducing sewer overflows is a steadily growing practice at Black & Veatch," said Dan McCarthy, President and CEO of Black & Veatch's global water business. "We expect this growth to continue as more cities - both large and small - work to reduce their sewer overflows."

Black & Veatch engineers are currently conducting geotechnical investigations that will determine the location and route of the potential 30-foot diameter tunnel and how far underground it would need to be placed. If approved, detailed design is expected to begin in 2011, with overall project construction to be completed in 2018.

At 1.2 miles in length and 30 feet in diameter, the Lower Mill Creek Tunnel would be able to hold more than 33 million gallons of sewer overflows.

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