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Project in 60 Seconds: Controlling the Flow

May 7, 2019

Chris Limke of POWER Engineers

By Chris Limke
Senior Project Manager, Midwest Environmental Services


Combined Sewer Overflow Source Control


Start: July 2013 Completion estimate: August 2019


Metropolitan Sewer District of Greater Cincinnati (MSDGC)

Total Project Cost

$35 million

POWER’s Role

In Layman’s Terms

For older cities like Cincinnati, Ohio, the sewer infrastructure was originally designed to convey both stormwater and sanitary sewage (wastewater from your drains and toilets) in the same pipe to a treatment plant. Known as combined sewers, they are often filled beyond their capacity during heavy rains. To relieve pressure on the sewer line and prevent widespread flooding and sewage backups into buildings, combined sewers were designed to overflow directly into local creeks and rivers through outfall structures known as combined sewer overflows or CSOs. At the time they were built, CSOs were an acceptable way of handling excess flows, but their environmental impacts are now regulated under the federal Clean Water Act.

UAV at work. POWER drone captured imagery and video of Phase B CSO storage tank site construction.

UAV at work. POWER drone captured imagery and video of Phase B CSO storage tank site construction.

POWER provided watershed planning and infrastructure design services for a portion of the Metropolitan Sewer District of Greater Cincinnati’s wastewater collection system to reduce or eliminate CSO discharges to local creeks and rivers as required by Federal Consent Decree. Each outfall location in the collection system where these discharges occur is assigned a number. This project involved two CSO locations: CSO 217 and CSO 483. The proposed alternatives included separating stormwater in separate stormwater pipes from the wastewater collection system or providing temporary stormwater or wastewater storage in the system. Both were designed to reduce peak flows during storm events from overwhelming the collection system and resulting in CSO discharges.

Ultimately, the preferred source control alternative for the 1,000-acre CSO 217/483 watershed included a combination of both: four stormwater detention basins, sewer separation along major roads, and a wastewater storage tank to reduce CSO volume at CSO 217; stream restoration; and sewer separation along major roads to reduce CSO volume at CSO 483. This alternative is anticipated to achieve 96 million gallons in CSO volume reduction in a typical year.

Accomplishments and Challenges:

REGULATORY REQUIREMENTS: Designs are required to meet regulatory limits on the amount of CSOs allowed during a typical rainfall year. In many areas, it was not practical to simply construct independent sewers to separate stormwater from the wastewater collection system. This meant POWER spent time studying numerous scenarios to get the stormwater and wastewater storage infrastructure down to the smallest size possible while still meeting the performance requirements of the Consent Decree.

Trenchless situation. Workers install jack and bore sewer pipe crossing below major road.

Trenchless situation. Workers install jack and bore sewer pipe crossing below major road. Photo Credits: Chris Limke

Photo Credits: Chris Limke

MINIMAL COMMUNITY IMPACT: Retrofitting large, complex infrastructure elements in often dense, ultra-urban settings can mean major disruption to the community during construction. Temporary road restrictions and closures cause traffic delays for the traveling public, and construction noise and dust can become a nuisance. The project required several property acquisitions in established communities. POWER’s efforts included significant involvement with the affected communities for both education and to promote acceptance of the proposed project.

TIGHT SCHEDULE: Completing designs on an accelerated schedule, POWER assisted MSDGC in constructing needed wastewater infrastructure in compliance with federal Consent Decree requirements. POWER-Cincinnati continues to provide planning and design services for MSDGC.

Project Team:

Additional Services

POWER completed hydrologic and hydraulic modeling of each alternative to estimate CSO reduction achieved and performed cost estimation and triple bottom line analyses to identify the most cost-effective solution.

We also prepared construction documents for multiple, phased bid packages, completed federal, state and local permitting, assisted with right-of-way acquisition, and provided bid phase and construction administration services.

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Chris Limke is a civil engineer with a broad range of consulting experience, working with a variety of clients in providing industrial, institutional, commercial and municipal facilities and infrastructure solutions. He is practiced in managing and training staff, project management, site analysis and design, overseeing preparation of construction documents and construction administration. His qualifications include architectural design and computer-aided engineering.

Chris has extensive experience in managing and designing complex, multi-disciplinary projects featuring roadways, utilities, earthworks, storm water management systems and buildings and facilities.