Popular Twin Cities lakes that have long been considered "impaired" because of algae and contaminants are now facing another pollutant: road salt.
Lake Calhoun in Minneapolis, Como Lake in St. Paul and Medicine Lake in Plymouth were among a couple dozen lakes added to a draft of the state's "impaired waters" list on Monday for having too much chloride.
"That makes me sad to hear that that's the case," said Janna Caywood, who lives near Como Lake and has led a neighborhood effort to reduce the lake's high phosphorus levels, which have been traced to fallen leaves. "It makes me worried because salt can poison a water body at high levels."
Researchers are still trying to determine the impact different concentrations of salt can have on a lake or river, but people are concerned about it because most of the salt that runs off into the body of water tends to stay there and can build up over time. A 2009 University of Minnesota study showed 70 percent of salt applied to roads in the Twin Cities stayed in the area.
Cities, park officials and the Minnesota Department of Transportation have been working on ways to reduce the amount of salt being applied to roads, and many plow operators have received training to help meet that goal.
The Minnesota Pollution Control Agency maintains the list of impaired waters and makes plans to clean them up.
Rich Brasch, water resources manager for Three Rivers Park District, which oversees parkland on Medicine Lake, said chloride concentrations in Medicine Lake could be worse, but that the listing will prompt a new round of discussions on how to reduce salt runoff.
"This cuts across a great number of government units that are involved in winter road maintenance," he said.
The MPCA is proposing to add 473 lakes, rivers and streams to the impaired list for reasons ranging from E. coli bacteria to mercury in fish to excessive algae.
Legacy Amendment money has allowed the agency to test and monitor more bodies of water in recent years, which has led more of them to be labeled as polluted.
At the same time, MPCA officials said they propose removing 10 lakes and 20 stretches of rivers or streams from the list — the highest number ever. That includes three-quarters of a 32-mile stretch of the Mississippi River between the Ford Parkway Dam and Hastings in the Twin Cities metro area.
The water was labeled "impaired" in 2008 because of high levels of perfluorochemicals, or PFCs, in fish. Those levels have decreased enough for the stretch of river to be delisted, said Katrina Kessler, who manages water assessments and information for the MPCA.
"Recent fish and water surveys have shown that conditions have improved such that it is now safe to eat the fish," she said.
About 2,500 of the state's lakes, rivers and streams are listed as impaired. The MPCA keeps track of list and makes plans to clean them up. With help from Legacy funds, the agency expects to monitor and test waters in all of the state's 81 watersheds by 2018.
Being placed on the impaired waters list is the first step in a long process, Kessler said.
Besides road salt, sources of pollution include coal-fired power plants, bacteria from septic systems, nutrients and insecticides from farming and stormwater runoff.
"There's a complicated story that needs to be figured out before we can say for sure what sources need to be reduced," she said.
The additions to the list released Monday are in draft form. State officials will hold a series of meetings on the list in December, and a public comment period will take place in January. The MPCA plans to send a final list to the U.S. Environmental Protection Agency by April 1.
MPCA officials said more waters could be added to the list once the agency has determined whether waters used for the production of wild rice meet sulfate standards.
Some of the lakes that could be added to the state's impaired waters list for salt:
• Calhoun (Minneapolis)
• Medicine (Plymouth)
• Como (St. Paul)
• Wirth (Minneapolis)
• Powderhorn (Minneapolis)
• Hiawatha (Minneapolis)
• Brownie (Minneapolis)
• Johanna (Ramsey County)
• Long Lake (Ramsey County)