Focusing on the Lower Mill Creek Watershed
The Lower Mill Creek watershed, which drains into the Mill Creek, contributes more than 7 billion gallons or >50% of the total overflows that occur annually from combined sewers in Hamilton County.
Under Project Groundwork, MSD must eliminate 2 billion gallons of CSOs from this watershed by 2018. The Lower Mill Creek watershed includes nine sub-watersheds, eight of which contribute significantly to the volume of CSOs in Hamilton County1.
1The Gest Watershed is the only subwatershed that does not significantly contribute to CSOs.
Two Different Solutions
To achieve this goal, MSD is evaluating two different solutions to determine the best, most locally preferred solutions to eliminate 1.6 million gallons of CSOs. Note: A reduction of 400 million gallons has already been achieved through other projects.
The two solutions are:
Default Solution (Tunnel): The regulator's default solution is a deep storage tunnel (about 30 feet in diameter and 1.2 miles long) beneath the Mill Creek. Excess flows would be captured and stored during rain events and then discharged to an enhanced high-rate treatment facility (EHRT).
Alternative Solutions: As part of the regulators' mandate, MSD has the opportunity to explore alternatives to the tunnel. One alternative is the use of sustainable infrastructure to control stormwater at the "source." These source control projects, such as separating combined sewers and installing stormwater retention basins, delay or prevent stormwater and natural drainage from reaching combined sewers, thus reducing overflows.
MSD must submit its preferred solution for reducing overflows in Lower Mill Creek to the regulators by December 2012. In the interim, MSD is proceeding with planning and design on both solutions. The regulators are anticipated to make a determination regarding an alternative remedy by the second quarter of 2013.
Alternative Sustainable Infrastructure Solutions
Sustainable infrastructure, also referred to as green infrastructure, focuses on retaining and treating stormwater as close to the source as possible, allowing it to infiltrate into the ground or evaporate into the atmosphere and rediscovering and restoring natural systems to receive stormwater.
MSD is currently evaluating stormwater "source control" opportunities in eight sub-watersheds of Lower Mill Creek: Bloody Run, Clifton, Denham, Kings Run, Lick Run, Mitchell, Ross Run and West Fork.
These watersheds have undergone a formal evaluation known as the Sustainable Watershed Evaluation Process (SWEP) to
- Characterize each watershed
- Identify opportunities and constraints
- Recommend solutions
- Implement solutions.
Based on the results of the SWEP, source control opportunities are being advanced now in four watersheds - Bloody Run, Kings Run, Lick Run and West Fork. Future source control opportunities are being considered in the four remaining watersheds - Clifton, Denham, Mitchell, and Ross Run.
The SWEP takes into account such factors as the volume of CSO overflows, the cost per gallon to remove CSOs and feasibility of source control in the watershed.
MSD is still in the early planning and technical evaluation stages in all the watersheds. Over the next two years, MSD - with input from the community - will develop Master Plans for the watersheds, which will be presented for consideration by elected officials and local authorities.
Funding for these projects is derived from the "Sustainable Infrastructure (Green)" allowance program under MSD's Project Groundwork (wet weather plan).
Learn more about source control opportunities in eight sub-watersheds of Lower Mill Creek.