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Two Potential Solutions in Lower Mill Creek
The Lower Mill Creek watershed, which drains into the Mill Creek, contributes more than 7 billion gallons (or >50%) of the total 14 billion gallons that overflow annually from combined sewers across Hamilton County.
Under Project Groundwork, we must eliminate 2 billion gallons1 of these combined sewer overflows (CSOs) from the Lower Mill Creek Watershed by 2018.
To achieve this goal, we are evaluating two different solutions: default solution or alternative solution. MSD has until December 2012 to select the preferred solution. In the interim, MSD is proceeding with planning and design on both solutions.
- Default Solution. The U.S. EPA-designated "default solution" is a deep storage tunnel (30 feet in diameter and 1.5 miles long). Excess flows would be captured and stored during rain events and then discharged to an enhanced high rate treatment (EHRT) facility.
- Alternative solution. The alternative solution seeks to control CSOs by reducing the amount of stormwater entering combined sewers during heavy rains. These solutions are often called "source control" because the control the source of the problem: stormwater.
Source control solutions can include:- Replacing combined sewers with separate stormwater and sanitary sewers
- Building detention or retention basins to hold large volumes of water during rain events
- Restoration of existing or defunct streams to properly handle natural drainage
- Removal of stormwater inlets into combined sewers, etc.
The Lower Mill Creek watershed includes nine sub-watersheds, eight of which contribute significantly to the volume of CSOs in Hamilton County.2
Source control opportunities are being considered in a number of these watersheds as part of the alternative solution.
Focus on Lower Mill Creek Watershed
The Lower Mill Creek watershed includes nine smaller watersheds that drain to the Mill Creek. The watershed includes almost 50 Cincinnati neighborhoods, as well as Amberley Village, City of Cheviot, Elmwood Place, Golf Manor, Norwood, St. Bernard, and portions of Coumbia Township, Green Township, and Springfield Township.
Lower Mill Creek Watershed Map
The Lower Mill Creek Watershed covers approximately 40,000 acres (62.5 square miles) in the heart of Hamilton County.
1A reduction of 400 million gallons has already been accounted for through real-time controls at CSO outfalls. Real-time controls include gates, pumps and inflatable dams, etc. that are constructed inside sewer lines to divert excess flows to a different part of the sewer system.
2The Gest Watershed is the only subwatershed that doesn't significantly contribute to CSOs.