City looks to address chemicals in Pattee Creek watershed
Martin Kidston
(Missoula Current) Stormwater runoff in the Pattee Creek drainage has revealed a number of pollutants, which the City of Missoula hopes to address in a proposed bio-filtration project.
Tracey Campbell, superintendent of the city's stormwater utility, said previous monitoring in the watershed identified several emerging pesticide-related contaminants including carbaryl, diuron and prometon.
The city will apply for clean water funding through a state revolving loan managed by the Montana Department of Environmental Quality to carry out further site screening and develop a plan with estimated costs.
Phase 1 carries a cost of $70,000.
“Previous monitoring has identified pesticide-related emerging contaminants,” said Campbell. “The city explored several potential approaches including targeted treatment retrofits. The proposed first phase will include site and treatment-technology screening, development of a sampling plan, alternatives evaluation, and conceptual design and cost estimates.”
Several of the contaminants are found in over-the-counter products including carbaryl, which is sold as an insecticide but can cause reduced litter sizes and decreased fertility in tested mammals.
Diuron is also sold as both an algaecide and herbicide and works by reducing photosynthesis. Prometon is also an over-the-counter herbicide with long persistence but can impact both aquatic and terrestrial organism and can contaminate water supplies.
Campbell said several approaches were considered to addressing the pollutants in the Pattee Creek watershed.
“The distributed bio-filtration approach was advanced for further development because it provides flexibility to intercept and treat runoff closer to pollutant sources at multiple priority locations throughout the watershed,” she said.
The treatment retrofits are proposed for Takima Park, Cutthroat Corner and the Bitterroot outfall. If approved, the project would be fully reimbursable by state clean water funds.
“I think this is a good and interesting project, and it's all reimbursable from DEQ,” said City Council member Mirtha Becerra. “It's a great benefit for our community.”
In 2022, the city partnered with the Big Sky Watershed Corp to explore potential improvements to the Pattee Creek watershed, with a primary focus on reducing the urban impacts on the Bitterroot River.
That effort sought buy-in from various property owners, ensuring they'd help maintain their share of the restoration work once it was complete. The work also proposed a riparian assessment and mapping all footbridges that cross the creek.