Stormwater projects can vary from dry well installation, maintenance, and cleaning to levee maintenance. This page provides information on projects scheduled for 2021.
We will provide regular updates here on our Projects page and on Facebook as schedules are finalized. For more information, or call (406) 552-6364.
Caras Park – Stormwater Outlet Phase II Project
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.
Stormwater Project Contact: Andy Schultz, City Engineer for Utilities, at SchultzA@ci.missoula.mt.us or call 406-552-6758