18th and Fort Sewer Improvements Project

The City of Omaha’s ambitious Clean Solutions for Omaha program, established in 2006, is designed to address the challenges posed by the city’s aging combined sewer system. These challenges include localized flooding and combined stormwater and raw sewage overflow into local waterways during heavy rain events. This $2.1 billion plan to revamp the City’s sewer system, which includes nearly 60 projects and is slated for completion in 2037, will ultimately allow the city to capture or treat at least 85 percent of its average annual combined sewage volume, significantly improving local water quality and public health.

The City of Omaha selected Carollo Engineers to plan and design six sewer separation/rehabilitation projects under this program, as well as two sewer separation/rehabilitation projects under its sister program, the Renovation of Combined Sewers program, which focuses on separating sewers for basement backup relief or to minimize street flooding. In late 2021, Carollo completed the $3.8 million 18th and Fort Sewer Improvements Project under this latter program. The goal of the project was to address historical flooding near the intersection of 18th and Fort streets and two nearby stormwater screening structures.

Using strategies like hydraulic isolation, sewer separation, and redesigned screening structures, the project team was able to eliminate the chronic flooding near the 18th and Fort intersection. Previously, during storm events, reverse flow would overwhelm the 36-inch combined sewer beneath Fort Street and flood manholes in the area. The project team implemented hydraulic isolation through a new in-line check valve that now protects the sewer from downstream surcharging. Upstream of the new check valve, new sewer separation improvements converted the upstream system from a combined system to a sanitary system, minimizing peak flows conveyed to the sewer. The team also replaced the Carter Lake detention pond outlet structure and strategically moved an in-line screening structure closer to the lake to improve screening and reduce the potential for flooding. These improvements protect residents from the disruption, health risks, and costly cleanup that can result from basement backups and street flooding during storm events.

This project, along with Carollo’s other work under the Renovation of Combined Sewers program and Clean Solutions for Omaha program, has reduced negative impacts on communities, improved local water quality, and let Omaha achieve a greater return on its sewer improvement investments. The infrastructure improvements have also restored public confidence in the system’s reliability, and the underground infrastructure remains where intended: out of the public’s sight and mind.