Managing localized flooding and combined sewer overflows: Omaha’s programs for Missouri River protection

Underground infrastructure often goes unnoticed until it fails, and in communities with combined sewer systems, that failure can result in localized flooding, public health risks, and costly cleanups. Omaha, Nebraska, faces these very challenges, with a system that must manage both stormwater and wastewater while protecting the Missouri River.

A recent article in Water Online by Carollo’s Caroline Burger, Ryan Rossell, and Weston Engel explores how Omaha is addressing these pressures through innovative combined sewer overflow (CSO) and sewer renovation programs, and how Carollo is partnering with the city to deliver infrastructure improvements that build resilience and community trust.

Addressing CSOs in Omaha

In the article, the authors talk about how Omaha is one of more than 800 U.S. communities with combined sewer systems, which carry both stormwater and wastewater through the same pipelines. During heavy rain, these systems can exceed their capacity, releasing CSOs into local waterways.

To address this, the authors explain how Omaha entered an Administrative Consent Order in 2007 requiring compliance with the Clean Water Act and the EPA’s CSO Control Policy. The city must capture, treat, or eliminate at least 85 percent of annual CSO volume by 2037. Alongside this effort, Omaha launched its Renovation of Combined Sewers (RNC) Program, which targets sewer backups and localized flooding in areas outside the CSO Program. While distinct, the programs share processes, standards, and guidance, creating coordinated and cost-effective solutions.

Stormwater Resilience: 18th and Fort Sewer Improvements

The article highlights how a recent RNC project, the 18th and Fort Sewer Improvements, illustrates how tailored strategies can resolve long-standing flooding issues. Flooding along Fort Street stemmed from reverse flows in the 72-inch North Interceptor, which overwhelmed a 36-inch combined sewer and caused manhole flooding. Additional flooding near two screening structures occurred when debris blocked flows, impacting roads and parks.

Carollo and project staff implemented a combination of hydraulic isolation, sewer separation, and new screening structures to address the problem. Hydraulic isolation protected the 36-inch sewer using an in-line check valve, while sewer separation diverted stormwater flows into a new dedicated system. Screening improvements included relocating and redesigning structures with input from operations staff, which provided easier access, safer maintenance, and more reliable performance.

Flood Prevention and Lasting Benefits for the Community

Since the project’s completion, residents in the 18th and Fort Street area have been spared from the basement backups and street flooding that once accompanied storm events. The improvements have eliminated local surcharging, enhanced system reliability, and strengthened community trust in Omaha’s sewer infrastructure.

As the authors explain, Omaha’s dual approach to CSO and RNC programs demonstrates how coordinated planning, innovative engineering, and collaboration with utility staff can protect both communities and waterways.

Read the full article on Omaha’s approach to managing flooding and CSOs.