MINNEAPOLIS -- The runoff of de-icing fluid into the Minnesota River from Minneapolis-St. Paul International Airport through April exceeded permit limits for the entire year, airport officials said Friday.
Patrick Hogan, spokesman for the Metropolitan Airports Commission, said 1,024 tons of wastewater containing glycol flowed into the river from the airport in the first four months of the year, exceeding the annual limit of 900 tons.
The airport has a containment system that captures much of the glycol used to de-ice airplanes, but some of the fluid gets onto the ground and is washed into the nearby river with rainwater and snowmelt through the sewer system, Hogan said.
"We have been monitoring the river. As far as we can tell it isn't having any negative impact on water quality or on wildlife," Hogan said.
"The real danger with glycol is when you get concentrations that are too high. Because it is a biodegradable chemical, it breaks down into carbon dioxide and water. So when you don't have really high concentrations, it doesn't hurt anything in the environment," he said.
The MAC notified the Minnesota Pollution Control Agency last month that the glycol runoff was expected to exceed permit levels as a result of the harsh winter, Hogan said.
"The airlines applied almost twice the amount of glycol this year that they normally do," he said. "Last year, for example, only 300 tons of glycol actually ended up in the river. So normally we're well below the permissible amount."
The Pollution Control Agency discussed the situation during a meeting with representatives of the attorney general's office on Wednesday, but is waiting until the end of the year to determine whether penalties will be assessed.
Steps already are in the works to prevent the problem from recurring.
"We're in the process of building two new de-icing pads that will have containment centers for glycol, Hogan said.
"We're also working with the Pollution Control Agency and the Metropolitan Council to explore the possibility of diverting some storm water to the Metropolitan Wastewater Treatment Plant," Hogan said. "But that would require a special permit that right now we don't have."
Hogan said the airport has never before exceeded its glycol discharge limits.
The airport has spent $25 million over the past four years to reduce glycol runoff.
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