Hasty Brook, located in the northeast corner of Carlton County and part of the Grand Rapids Watershed, was recently added to the impaired waters list for high levels of E. coli.
Other waters in the Carlton County portion of the Grand Rapids Watershed were already on the impaired list, including Eagle Lake, Upper North Island Lake, Lower South Island Lake and Tamarack Lake, due to high levels of phosphorus.
But what, exactly, causes high phosphorus and E. coli levels, and how does it hinder aquatic life?
Various environment-related agencies joined for a public meeting Thursday, Dec. 6, in Cromwell to help answer these questions and share the results of a study that looked at the water quality in the Grand Rapids Watershed, a project that began in 2015.
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Minnesota Pollution Control Agency (MPC), the Carlton County Soil and Water Conservation District, the Minnesota Department of Natural Resources and Emmons and Olivier Resources (EOR), a water resource-based engineering and environmental consulting firm, hosted the informational session.
When it comes to bacteria and E. coli pollution in water bodies, Meghan Funke, a consultant with EOR, said there are many culprits, but it all goes back to fecal matter.
"Anything that is a warm-blooded creature can have bacteria in their gut," Funke said, and this includes E. coli. "It can be from humans, or cows if you have a lot of cattle that go into a lake or stream. They poop and there's bacteria in the poop."
A deer path through a stream, geese flocking to a small lake, beaver dams and old septic systems can all lead to concentrations of fecal matter that cause E. coli levels to rise. It's not always the E. coli itself that's dangerous, but high levels of the bacteria can help indicate if more harmful bacterias are present.
"It doesn't always mean people are getting sick in the streams," Funke said of the streams in the watershed with higher E. coli levels. "MPC just monitored it and kind of flagged it and then we make sure there's no sources we need to address."
The source of phosphorus in the lakes is a little more complicated. A variety of natural cycles can increase nutrients like phosphorus in a lake, as well as fertilizer runoff.
"We often think, 'Well, what did we do?' Funke said when explaining what causes an increase in phosphorus levels. "Sometimes there are just parts of nature that have more nutrients than others."
A natural process that generates higher levels of phosphorus can happen in the summer when the top layer of a lake warms, but the bottom remains cold. This creates layers in the lake that are difficult to mix, leaving the bottom layer without a fresh supply of oxygen and sparking chemical process that causes phosphorus to release from the sediment.
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What's so bad about all this phosphorus? One pound of phosphorus can grow 500 pounds of algae, said Anna Bosch, watershed project manager with MPC. And too much algae shades out other native vegetation and then these plants can't grow.
EOR determined how the maximum amount of phosphorus each lake can take to maintain good health, as well as the percent of phosphorus that needs to be reduced. Fortunately, the four lakes in the Carlton County region of the watershed all need a 10 percent reduction rate, a number Funke said is manageable.
EOR also determined different implementation strategies to help decrease phosphorus levels in all four lakes. Shoreline buffers and vegetation as well as septic system inspections and maintenance education were listed among all four.
Storm water management in Cromwell was recommended to help improve South Island Lake. Forest protection programs were listed for Tamarack and Eagle lakes. Eagle Lake was also recommended for residential rain gardens. North Island Lake was recommended livestock and manure management.
These reductions can make the lakes fishable and swimmable again.
