B&N is helping the City of Columbus, Ohio, take a new, greener approach to remedy sanitary sewer overflows (SSOs) caused by inflow and infiltration (I/I) from stormwater runoff from private sources, such as roof runoff and sewer laterals.
To lessen the impact of SSOs on the environment, the City is operating under directives from the Ohio EPA using a multi-step approach to address the SSOs. Blueprint Columbus is the City’s pilot program to reduce SSOs and is founded on four pillars: lateral lining, roof water redirection, sump pumps and Green Infrastructure (GI).
GI helps manage stormwater runoff so that it doesn’t flow into the sanitary sewer. SSOs can cause raw sewage to back up into a home or a water supply, threatening private property and causing public health concerns. B&N is leading a Blueprint Columbus project in a 115-acre Clintonville neighborhood to evaluate, develop, design and implement GI solutions to prevent SSOs.
Green Infrastructure to Improve Stormwater Management
Using a PCSWMM model for a hydrologic and hydraulic (H&H) model of the study area, B&N determined the total suspended solids (TSS), nutrient treatment performance and GI alternatives. Based on these findings, B&N designed bio-basins, also known as rain gardens, within the neighborhood right-of-way between the curb and property boundary or sidewalk.
Openings in the roadway curb route the stormwater runoff into the bio-basins, which filter the runoff through a top layer of permeable, engineered soil, plants and gravel. These features filter certain pollutants before the stormwater reaches the sewer, such as roadway grime, grit, metals or trash, improving the quality of stormwater being discharged into streams.
Bio-basins also provide additional storage for the stormwater runoff. An underdrain at the bottom routes the runoff to the storm sewer. This controls the quantity of water going into the storm sewer, reducing the likelihood of overflow.
Private Property Enhancements to Reduce I/I
A vital component of the plan to reduce SSOs included reducing rainfall-induced I/I to sanitary sewers from private sources, such as roof runoff and sewer laterals. I/I can be decreased through rehabilitating sanitary main lines and enhancing private property drainage systems and sanitary sewers.
B&N lead private property enhancements to reduce I/I, including lateral lining, sump pump program implementation and redirecting downspouts. This was the pilot process to determine the course for Blueprint Columbus moving forward. Lateral lining rehabilitation seals the pipe to prevent stormwater runoff from entering the sewer. Redirecting sump pumps and downspouts directs stormwater to the bio-basins, ensuring that the runoff is filtered through the GI.
Key features of the Blueprint Columbus project included:
- Cleaning and televising sanitary laterals and storm sewers
- Performing detailed field investigations and locating downspouts
- H&H modeling of the study area stormwater system to identify GI storage and treatment capabilities
- Identifying and recommending cost-effective improvements
- Leading the downspout redirection and lateral rehabilitation for private properties
Construction was completed in May 2021.