Student-Designed Fish Passage Opens on the Millrace, Ending a Century-Old Barrier

The Millrace Fish Passage opened Monday afternoon with a ribbon cut by the civil engineering alumna who led the student team that designed it. The passage is a 120-foot roughened channel that runs beside the four-foot drop at the Millrace outlet. It climbs at a 3 percent slope through a series of engineered riffles and resting pools, so fish can make their way up in short steps.

Nothing has been able to swim up that drop since the mill dam came out in 1920. Brook trout have held on in the Porter River below the outlet, but the cold, shaded upper Millrace has been out of their reach for a hundred years.

The design began as a Civil Engineering capstone in fall 2022. A five-student team led by Abby Sorensen ’23 modeled the channel for two semesters, built a 1:10 scale version in the hydraulics lab and presented it to a joint city–county committee in April 2023. The state natural resources agency did the heavy earthwork. The university’s fabrication lab built the steel forms and monitoring brackets.

“For two years this was a spreadsheet and a model in a plastic tub. Today I watched water go down it. I am told the fish will be along in the spring, which is when fish do things, apparently.”

— Abby Sorensen ’23, now a water-resources engineer in Lake City

The $380,000 cost was shared three ways:

• State habitat grant: 60 percent
• UW–Porter Falls: 25 percent
• Porter River Riverkeepers: 15 percent, raised mostly through a pancake breakfast and a raffle the group says “got out of hand”

The passage will be monitored by students in the Riverwatch program run by the Freshwater & Watershed Laboratory. Since August, Riverwatch crews have implanted small transponder tags in brook trout below the outlet. Antennas at Station 3, below the passage, and Station 7, above it, will record any tagged fish that make the climb during spawning season next spring.

Dr. Henrik Moe, associate professor of environmental science, said the passage is only half the job. “Trout need cold water, and cold water needs shade,” he said. The Riparian Corridor Project has planted about 1,900 native trees and shrubs along the main stem since 2023 and plans another 1,300 by the end of next year.

Visitors can see the passage from the Millrace Loop of the Riverfront Trail, just past the historic footbridge. Advice on where to walk, and where not to wade, is on The Millrace and Porter River. Station data is posted on the river and Millrace ecology page.

Contact: Office of University Communications, news@uwporterfalls.edu