Martin Kidston

(Missoula Current) Work to improve stormwater runoff in the South Hills and the retention of excessive water is set to begin this year, including work at “Cattail Corner” where wetland habitat will be improved.

The city began addressing water issues in the South Hills after a series of earthquakes opened new springs several years ago.

This week, the city extended that work and approved three stormwater projects for the South Hills – a large residential area of Missoula built on steep valley slopes. Cattail corner is part of the South Hills stormwater system and will receive roughly $1 million in improvements.

“It will remove a large amount of accumulated sediment to restore the original retention volume,” said Adam Marsh. “It will also provide some contouring in the bottom of the wetland to improve vegetation diversity and provide some open water to improve habitat quality for the wildlife that frequents the area.”

Cattail Corner sits off Russell and 39th Streets and catches stormwater in a shallow, vegetated basin that attracts a range of bird species. The basin also helps filtrate the water before it reaches the Bitterroot River.

The basin currently includes 10 dry wells.

“We'll install nine extra-depth dry wells in the infiltration basin to provide additional capacity during large stormwater events,” Marsh said.

Another $900,000 in stormwater work is planned along the 55th Street corridor in the South Hills. The road is long, straight and relatively steep and sends stormwater down the hill at rapid speeds.

That has caused issues for property owners.

“This will prevent water from shooting down 55th Street at pretty high speeds,” said Marsh. “We're going to be regrading the road so it stays in the east gutter lane.”

The work includes nearly 800 feet of new storm main along with gutters and contouring to keep water from running into side streets on its way down the hill.

“A portion of Garrett Street will be recontoured to prevent ponding,” said Marsh. “It's causing issues for private land owners.”

Marsh said much of the work is funded by a competitive grant from the American Rescue Plan Act.

The earthquakes that woke Missoula residents in the early-morning hours of 2016 and again in the evening of 2020 opened new springs in the South Hills, which began seeping water onto city streets and causing a range of problems.

The city in 2022 approved a nearly $400,000 service agreement with WGM Group to capture that water and divert it into the city's stormwater system.