Up and down the St. Croix and across its broad watershed, projects that are often almost invisible are starting to reduce runoff into the river. The investments are intended to last long into the future, to protect the river for generations.

Organizations from nonprofits to watershed districts to local highway departments are making the many seemingly minor changes necessary to protect and improve the St. Croix’s clean water.

Scientists studying the river in the 1990s and 2000s determined that that there is too much phosphorus in the lower St. Croix River. Further studies showed that the excess essentially exists because of fertilizer applied to farm fields and lawns, as well as changes to the landscape that cause stormwater to run off more quickly, eroding more soil.

Ten years after the U.S. Environmental Protection Agency declared the Lower St. Croix River impaired for too much phosphorus — which creates bigger and more severe blooms of algae that can produce harmful toxins — seemed like a good time to check in on the effort to restore its health.

On a fall-like day in September, the St. Croix River Association led a tour of four recently-completed water quality projects along the Minnesota side of the river, from Lakeland in the south to Taylors Falls in the north.

All of the projects were funded from multiple sources — private, public, and nonprofit — to get the most benefits and keep costs down. At each project site, local watershed managers highlighted the unique ways they designed projects, sharing resources and combining ideas — all to increase the impact.

Complex work, tight spaces in Lakeland

Just south of the I-94 bridge, rain had been running off a large residential part of the city of Lakeland for years. It was all flowing down city streets and gutters to a site on the south side of Beanie’s Marina. That’s where the water was washing out a growing gully, creating a dangerous and unsightly situation, which was also dumping tons of sediment and nutrients into the river each year.

The local watershed district worked with the city of Lakeland — and at least one dedicated neighbor — to install a lengthy series of projects to capture the runoff and slow it down. By holding it back temporarily, some of the water can soak into the soil or evaporate, and less will rush down the banks all at once.

Starting in city right-of-ways along the residential streets, turf gass ditches at the edge of the 12-acre neighborhood that gently slopes toward the point were reformed and replanted with native species that can soak up a lot of water. Working like terraces, each part of the sloping trough is separated by a small berm that will let the basin fill with an inch of water before spilling over.

“We wanted to keep the budget low, but didn’t want to do a band-aid,” former administrator Mike Isensee said. “We wanted a long-term solution.”

From the plantings, the water flows down another gutter and into spots where the curb is cut, letting it flow into an iron enhanced sand filter, which captures phosphorus. Finally the water flows through a pipe down the bluff, which has also been restabilized and replanted, into a final catch basin before it goes into the river.

The project was combined with the city’s regular road resurfacing, which made it easier and cheaper to accomplish. Based on maintenance plans and research from the University of Minnesota, project managers say the costly parts of the project should last at least until the next time the adjoining road must be replaced.

The project should keep more than 3,000 lbs of sediment and 8.5 lbs of phosphorus from flowing into the St. Croix each year.

Brown’s Creek capture

Brown’s Creek in Stillwater is one of the jewels of the lower St. Croix Valley, a trout stream that flows largely through residential areas before joining the St. Croix. Trout require cold, clean water to live and reproduce, so reducing the amount of warm and dirty water flowing off the landscape is a top priority for the Brown’s Creek Watershed District.

In 2017, the agency worked with the Washington County highway department on a road construction project, adding technology to capture and treat stormwater from a 25-acre area that previously flowed straight into the creek. The problem was stark: the numbers of trout and the insects that live in cold, clean streams were both dwindling.

Tight on space because of McKusick Road and other factors, the water needed to be held underground, not in surface plantings. The district installed three underground water tanks with drains into them, which traps sediment and other detritus before it enters the creek. Seven existing basins were retrofitted with baffles and skimmers to remove more harmful material from the water.

All told, the project reduced the sediment flowing into the creek by more than 3,200 lbs per year, and reducing the amount of phosphorus flowing into the creek and ultimately the St. Croix by 7.7 lbs per year.

District administrator Karen Kill said the project also highlighted an emerging accomplishment — and need. After 10 years of installing water quality projects up and down the St. Croix Valley, maintenance needs are increasing. The tanks must be cleaned out regularly, and other work done to keep everything operating at top performance.

“We’re adding so many practices and small practices that maintenance is becoming an issue,” Kill said.

While it’s relatively easy to get funding to install projects, it’s harder to get grants that pay for the upkeep.

The agency contracts with the Washington Conservation District on the maintenance, but the costs are rising. Kill suggested perhaps multiple watershed districts could work together to buy equipment needed to clean and maintain all their projects.

Prairie sponge

After a bus ride up St. Croix Trail, the next stop was at a rural residential property where a huge area that was previously lawn is being converted into prairie.

Nearly two acres of sloping land with a culvert on the bottom, which went under the highway and into Arcola Creek and to the St. Croix a half mile downstream, is in the process of being planted with grasses that hold water.

Rather than other projects that were meant to capture runoff from rain as it flowed toward the river, this expansive prairie will let the water soak in right where it falls.

This project showed the power of clean water projects to also benefit things like pollinators and other wildlife. The prairie was home to a chorus of crickets this afternoon, and favored by bees, monarch butterflies, and many other insects.

All told, the work is expected to keep about .5 lbs of phosphorus out of the St. Croix each year. With the costs shared between the property-owner and government agencies, the whole thing was done for a minimal cost.

Taylors Falls gullies

Along much of the lower St. Croix, relatively flat uplands drop down to the river along a bluffline called an escarpment. These constantly-eroding bluffs are susceptible to increased runoff flows, which can create gullies that erode into the river.

The final stop of the tour was in Taylors Falls, where the Chisago County Soil & Water Conservation District has been working for several years to improve the condition of many of these gullies in its area.

In a residential neighborhood on the hillside, water resource specialist Casey Thiel showed how the agency worked with homeowners to restore a gully running right through town.

Because the organization has identified 36 severely-eroding gullies along this escarpment, they’ve been hard at work since 2012 stabilizing the highest priority sites. The gully in this neighborhood showed some of the techniques.

First, they have to reduce the runoff coming from above, and a basin is built at the edge of the bluff to capture stormwater before it plunges down the slope. Second, the gully walls are stabilized with native plantings with roots that hold the soil in place.

While tree roots can work well, some of the projects have required cutting trees. Too much shade can make it hard for grasses and other plants to grow, leaving soil exposed. And, when trees tip over on the steep hillsides, the root wads can leave behind huge soft areas that quickly wash out.

Four of many

These projects were presented as examples of what is being done to improve the St. Croix River’s health and long-term resiliency. Almost all of them received some funding from Minnesota’s Legacy Amendment, a sales tax which voters approved in 2008.

The St. Croix River Association has worked with the many partners on the ground to provide funding and coordinate projects all along the river.

Soon, the ground will freeze and work will come to a stop for the winter. But next year, these projects will be maintained, new ones will be put in the ground, and the river will hopefully continue to function naturally, without excess sediment and nutrients.

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