Big environmental improvements don’t always start with big projects. In Duluth, restoration on one small creek improved water quality well beyond its banks, reaching downstream in the St. Louis River estuary and ultimately supporting the health of Lake Superior. The effort began after the MPCA found unhealthy levels of chemicals in Snively Creek. Using the agency’s data, the U.S. Environmental Protection Agency (EPA) and an industry partner carried out targeted restoration work that created a ripple effect that strengthened the health of the entire connected ecosystem.
For decades, Snively Creek carried polychlorinated biphenyls, better known as PCBs, in stormwater flowing through this unassuming, wooded area. The stream flows into one of 23 remaining Great Lakes Areas of Concern, where decades of legacy pollution have damaged water quality and biological health.
After investigating the site, the MPCA determined that the source of the PCBs was a former electrical repair facility that operated near the creek from about 1954 to 2001. To the naked eye, the pollution wasn’t obvious.
“A lot of times when you’re going to a site, there will be a chemical odor or it will be stained,” said Brad Leick, an MPCA hydrologist. “But that doesn’t happen with PCBs. At this site, you wouldn't know it was there unless you sampled it.”
The MPCA oversaw the investigation, which found concentrations of up to 7,280 milligrams of PCBs per kilogram (mg/kg) of soil, far above the standard for residential soil, at 0.82 mg/kg. To protect both the environment and human health, the agency mapped out a cleanup area based on how much contamination was found in the soil where people might touch it. Then workers removed the soil to prevent it from spreading downstream, where Munger Landing, a popular boat launch, was recently restored.
LaRae Lehto is a project supervisor for the MPCA’s work in the Area of Concern. She has spent years balancing the need to look at the big picture and the need to zero in on small details.
“Snively Creek is part of that puzzle because it empties near Munger Landing, where the MPCA, EPA, and private parties spent more than $40 million to clean up contaminated sediment,” Lehto said. “It's really important that we get the last bit of contamination that is up in the watershed that would have the potential to recontaminate the area we just cleaned up.”
It’s an example of the MPCA’s careful attention to “source control,” identifying where pollution is coming from so it doesn’t spread. Crews removed PCBs 12 feet below the ground’s surface, working in heavy clay soils. About 5,000 cubic yards of contaminated soil and sediment were excavated, in consultation with the EPA’s Toxic Substances Control Act and funded by the Great Lakes Legacy Act, a federal program that is part of the Clean Water Act.
The work didn’t stop there. The MPCA identified several new sources of PCBs to add to the cleanup, including two manholes connected to downstream sewer lines. Contractors installed erosion control features to stabilize soil near the foundation of an adjacent apartment building. A temporary diversion channel was built for the creek, running outside the polluted area to make it easier to remove contaminated sediment within the creek bed. Clean fill was put in its place so the land would remain at the same level. To finish off the site, contractors planted native grasses, trees, and shrubs.
After all that work, sampling showed remaining levels of PCBs in the soil are below 1 mg/kg, and PCB levels in the groundwater are below detection limits.
“The most satisfying part of this project was knowing we got the source area addressed,” Leick said, “because there were people living right next to it. Kids live there. They go and play in the creek.”
Project leaders said they learned a lot about what can go well with this work. Rerouting the creek allowed workers to reinforce slopes and remove pollutants. Rapid laboratory testing helped scientists determine how far the contamination extended. Contingency plans addressed complicating factors such as having multiple sources of pollution and nearby construction. Close coordination with the onsite property manager kept the project on schedule and residents informed.
Munger Landing has been identified as the primary source of PCBs to the St. Louis River Area of Concern. The source-control work on Snively Creek could result in removing fish-consumption advisories for PCBs in the whole estuary.
“Things are looking really great at Munger Landing,” Lehto said. “Our post-construction sampling shows that the cleanup was successful. Because of the work that we did, we were able to remove the body-contact restriction at the site. It had been unsafe for wading, swimming, and fishing. Now it’s safe for all those activities. And because we did a full dredge and removal of the contaminated sediment, it no longer requires long-term monitoring or maintenance.”