Stormwater Projects

Stormwater projects can vary from dry well installation, maintenance, and cleaning to levee maintenance. This page provides information on projects scheduled for 2022.

Caras Park – Stormwater Outlet Phase II Project

January 2022 Update—The infiltration gallery has been installed. The headwall and flap gate will be installed once weather permits in the spring. Final grading will also be completed once weather conditions will allow.

Description:  The project involves installing a stormwater infiltration gallery under Caras Park and a small concrete headwall at the outfall pipe into the Clark Fork River just downstream from Brennan’s Wave. The headwall allows for a flap gate to be installed, preventing backflow into the infiltration system when the river is at higher levels.

Benefits:  The major benefits of this project include:

  • improving the water quality of the Clark Fork River by treating the stormwater with the highest concentration of contaminants from the downtown area before it enters the river,
  • providing health benefits for river recreationists by improving water quality,
  • improving water quality by diverting warmer stormwater into the infiltration gallery, and
  • complying with state water quality requirements.

Details:  In 2017, a hydrodynamic separator (HDS) was installed under the park to pre-treat stormwater runoff collected from Missoula’s 60-acre downtown area by removing larger debris from the stormwater. The current project improves upon that treatment by diverting the first one-half inch of stormwater into an infiltration gallery to further prevent stormwater runoff from carrying contaminants into the river. This initial stormwater runoff during a weather event has the most concentration of contaminants gathered from streets, sidewalks, gutters, and other areas where water enters storm drains instead of filtering into the ground. These contaminants include oil, grease, and bacteria.

In addition, stormwater is usually warmed as it moves across asphalt and concrete pavements as it makes its way into storm drains. Warm water further degrades the river’s water quality because it has a negative effect on fisheries and can enhance growing conditions for algae blooms, which are also bad for fish.

After the new infiltration gallery is installed, the first one-half inch stormwater will be diverted into the infiltration gallery where it will be filtered through highly permeable soils and eventually enter the aquifer instead of emptying directly into the river. This is the same way most other stormwater in Missoula is handled once it enters a storm drain. For larger storms, after the first one-half inch has been infiltrated, the remaining storm water will still discharge to the Clark Fork River.

Coordination:  This project was planned and is being coordinated with the City of Missoula’s Parks and Recreation Department. In conjunction with this stormwater project, Parks & Recreation will be implementing Phase 1 of the Caras Park Improvements outlined in the North Riverside Parks & Trails Plan, which was adopted by City Council in November 2020.

  • To install the infiltration gallery, the berm in the park between the trail and the pavilion structure will be removed.
  • Following structure installation, the area will be leveled to be more even with the brick plaza area around the pavilion, which aligns with Parks & Recreation’s plans. Removing the berm allows for an improved view of the river as well as room for trail widening and making the area usable for more activities.
  • This stormwater project is being timed so that the park area will be disturbed only once instead of once for stormwater work and once for the first phase of the Caras Park project.
  • By combining the efforts of the two departments, the City will realize a savings of about $100,000 in construction costs.
  • Park “down time” will be minimized because we are completing the work at the same time as the Montana Department of Transportation constructs the Bear Tracks Bridge on Higgins Ave.

Project Funding:  With fundraising help from the Missoula Downtown Foundation, the Parks & Recreation Department is able to begin the first phase of its North Riverside Parks & Trail Plan at the same time as we begin this stormwater project. We were able to bid both projects together, resulting in a savings of about $100,000 to the City of Missoula.

Project Dates:  Work is expected to begin Oct. 4 with completion expected in Spring 2022. These dates are subject to change due to weather and other unforeseen circumstances.

Project Map

Project Contact:  Andy Schultz, City Engineer for Utilities, at SchultzA@ci.missoula.mt.us or call 406-552-6758

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South Hills Stormwater Improvement ProjectProject Extents Opens in new window

A public meeting was held Thursday, April 7 at 6:00 p.m. to discuss project goals, scope, schedule, and funding for all three project phases fully described below.

South Hills Project Slideshow Presentation (pdf)

Public Meeting Presentation Video

Questions? Contact Adam Marsh at MarshA@ci.missoula.mt.us or 406-552-6679.

The City of Missoula won a $2 million American Rescue Plan Act (ARPA) grant to improve stormwater infrastructure in the South Hills. This grant, along with a 10% local match, will fund design and construction of stormwater improvements in the South Hills. This stormwater infrastructure improvement project will take place in three phases:

Phase 1—Grandview Way Improvements

Description:  This first phase of the project will extend stormwater mains up Rita Court and Morning Side Court. 

Public Benefits:  This work will alleviate issues with spring water flowing from private property into the City right of way. Following 2015 and 2020 earthquakes in the South Hills, new springs emerged on private property near Grandview Springs. These springs flow year-round, depositing more water on private property than the homeowners can handle. The water then ends up flowing onto adjacent sidewalks and streets, causing public safety issues when the water freezes. In addition, the excess water on the streets and sidewalks–including freezing and thawing cycles–damages the infrastructure, requiring frequent repairs and shortening its lifespan.

Project Dates:  Phase 1 is expected to begin this summer. More details will be posted here once available.

Phase 1 Area Map

Phase 2—Gharrett Street Improvements

Description:  This phase of the project will address a variety of stormwater issues along the Gharrett Street corridor, including the following:

  • Gharrett St. (55th St. to Rufus Rd)
    • Re-grade a portion of the street to eliminate ponding.
    • Install ADA crossings and curb and gutter extensions.
  • Bonnie Ct., Anthony Ln, Highwood Dr., and Valley View Dr. Intersections – Improve gutter on west side of intersection.
  • Storm Drain Extension – Extend stormwater main about 590 linear feet from Cardinal Dr. to Arcadia Dr., and install new inlets at intersections.
  • Water Quality Unit – Install a new hydrodynamic separator (HDS) into the new storm drain system to serve the Gharrett St. drainage. The HDS will improve water quality by removing large debris from the stormwater before it makes its way to the Bitterroot River.

Public Benefits:  Improved removal of stormwater from City streets. This help prevent ice from forming on streets and adjacent sidewalks, which can be a safety hazard for pedestrians, motorized vehicles, and bicyclists. It also prevents accelerated damage to street and sidewalk infrastructure.

Project Dates:  To be determined. This post will be updated when information is available.

Phase 2 Area Map

Phase 3—Cattail Corner Improvements

Description:  This project phase will improve how Cattail Corner functions as a stormwater treatment wetland. Additional work will be done to offset increased flows to the storm drain system due to the Gharrett Street project (Phase 2). Primary goals for Cattail Corner include:

  • increase stormwater infiltration capacity by installing dry wells around pond,
  • restore stormwater retention capacity by removing accumulated sediment, 
  • improve natural biological treatment of urban stormwater (additional water volume in the pond allows the stormwater to remain in the pond longer, providing more time for plants to remove and process nutrients in the stormwater), 
  • increase wetland biological diversity and habitat values by planting additional native plant species and removing invasive species, and
  • construct a forebay to improve access to the pond for easier maintenance.

This phase also includes the design and construction of two water quality unit retrofits on existing storm main to remove debris from stormwater before it enters the rest of the stormwater system.

Public Benefits:  Makes Cattail Pond into a well-functioning stormwater treatment facility that uses "green infrastructure" to treat urban stormwater. For information about green infrastructure, visit http://www.ci.missoula.mt.us/2678/Green-Infrastructure

Project Dates:  To be determined. This post will be updated when information is available.

Phase 3 Area Map

Project Contact:   Adam Marsh, Utility Engineer, email marsha@ci.missoula.mt.us or call 406-552-6679

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Maintenance Follow-Up Work on Levee III and Levee V

Description:  This project involves further removal of tree stumps that were initially treated last spring after the invasive or large tree was removed from the levee. Stumps that have sprouted will be cut off and treated again. For more information on last year’s project and reasons for removal, please visit http://www.ci.missoula.mt.us/DocumentCenter/View/59583/2021-Stormwater-Projects

Project Dates:  Scheduled to begin Tuesday, April 5, 2022, with completion expected around April 15. These dates are subject to change due to weather and other unforeseen circumstances.

Project Maps (pdf)

Levee V Work Area Map Opens in new windowLevee III Work Area Map Opens in new window

Trail Closure Information:

  • The North Riverfront Trail adjacent to the active work area will be partially closed weekdays 9 a.m. to 4 p.m.
  • Work will start at the Madison Street Bridge and move to the west.
  • Only the trail adjacent to the work area will be closed. Trail users are asked to use parks, streets, and sidewalks as needed to travel around the partially closed trail areas.

Because the trail will not be fully closed, no detour is needed. Cyclists and pedestrians are advised to use parks, streets, and sidewalks as needed to travel around the trail closure areas. Closures will be timed to avoid peak commuter traffic times. Please plan for a few extra minutes of travel time during the project.

Project Contact:  Tracy Campbell, Superintendent for the Stormwater Utility, at CampbellTL@ci.missoula.mt.us or call 406-552-6364.