Clark Fork River Sewer Crossing Improvements

Project Description

The City of Missoula Public Works & Mobility Utilities Division is planning improvements to a critical wastewater pipeline that crosses beneath the Clark Fork River near the Resource Recovery Facility.

Today, most wastewater generated south of the Clark Fork River travels through a single 36-inch gravity sewer main before reaching the Resource Recovery Facility for treatment. Crews installed this pipeline in 1963 using reinforced concrete pipe and a low-strength concrete cap.

A recent scour analysis and field investigation identified significant risks at the river crossing. Portions of the concrete cap have become exposed, and scour pits have formed downstream of the pipeline. During large flood events, river conditions could damage the existing infrastructure.

To protect public health, water quality, and wastewater service reliability, the City is evaluating options to replace the existing river crossing with a more resilient long-term solution.

Why This Project Matters

The existing sewer crossing serves a vital role in Missoula's wastewater system. If the pipeline were damaged, untreated wastewater could discharge into the Clark Fork River. River water could also enter the sewer system and overwhelm equipment at the Resource Recovery Facility, disrupting treatment operations.

Project Goals

Damage to the existing 36-inch gravity sewer main crossing the Clark Fork River could result in untreated wastewater discharging to the Clark Fork River and/or river water entering into the sewer system and inundating the Resource Recovery Facility resulting in disruptions to the treatment plant’s treatment capabilities. This project looks to replace the existing pipeline with a suitable alternative. This will mitigate the chances of raw wastewater discharge to the Clark Fork and will allow the Resource Recovery Facility to maintain normal operations.

Community Benefits

Replacing the aging crossing will help:

Protect the Clark Fork River and local water quality
Reduce the risk of wastewater system failures during high-flow events
Improve long-term reliability of wastewater service
Support continued operations at the Resource Recovery Facility
Strengthen critical infrastructure for future generations

Public Meeting

The City of Missoula Public Works & Mobility Utilities Division invites community members to learn more about the project and provide feedback on potential replacement options.

Tuesday, June 23, 2026
6:00 p.m. – 7:00 p.m.
Missoula City Council Chambers
140 W. Pine Street | Missoula, MT

Project staff will share information about the existing conditions, discuss replacement alternatives, answer questions, and gather public input.

We encourage residents, businesses, recreation users, and anyone interested in protecting the Clark Fork River to attend.