MPCA approves plans to curb sediment levels in Lake Pepin and Mississippi River

• Traveling down the river

A barge handles traffic on the Mississippi River.

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Efforts to clear up the waters of the Mississippi River and Lake Pepin passed a major milestone this week.

The Minnesota Pollution Control Agency Citizen's Advisory Board approved a new turbidity standard Tuesday to curb growing sediment levels in a 90-mile stretch of the river from Hastings down to upper Lake Pepin. The new standard, if approved by the Environmental Protection Agency, would be 32 parts per million, half the current standard of 64.

It's part of an effort to allow more light to shine in shallow areas of the lake and river. That would encourage plant life and, ultimately, improve water quality, said Michael McKay, director of the Lake Pepin Legacy Alliance, which lobbied in support of the effort.

"The basic thinking is that if you can get that sediment under control and the plant life settled back, the rest follows," he said.

The new standard also will help to decrease the buildup of sediment causing upper Lake Pepin to get steadily shallower, McKay said.

The standard came of out an MPCA study that found plant life could not grow at turbidity levels of over 64 ppm. By cutting the standard in half, the study concluded, plant life could thrive.

"It took a lot of different research efforts and looking at historical data, and we concluded that 32 was the right fit," said MPCA Southeast Regional Division manager Bob Finley.

Getting to that level, though, will require a whole new effort from state officials.

The MPCA will conduct an extensive study in the weeks ahead looking at the sources of river sediment and learning how to cut levels to new standards.

But Finley and other state officials already have an idea as to where the sediment muddying the waters of Lake Pepin is coming from.

The vast majority comes directly from the Minnesota River and its watershed, according to Finley. Much of this process is natural, he said, but changes in human activity have led to a near doubling of sediment loads over the past few decades.

"The landscape has changed with urban development and agricultural practices," he said.

Finley postulated that much of the sediment was coming from erosion and other processes acting directly on the channels of the Minnesota River and its tributaries, but that likely a third of it was coming from cropland runoff in the river's watershed.

Claims like this have prompted Minnesota farmers to cast a wary eye at the measure.

Riley Maanum, the Research and Project Manager of the Minnesota Corn Growers Association, said that he has no problem with the MPCA's attempt to clear up the water, but hopes the agency will use "hard science" to determine the source of sediment.

Because of southern Minnesota's unique geology, sediment has gone into the Minnesota River since even before agriculture, he said. While some erosion does occur on farms, he said, it is already in farmers' best interest to protect themselves from soil loss without the need for state enforcement.

"Agriculture is certainly not perfect. There are places where we can improve, but they need to start giving us credit where credit is due," Maanum said.

Tags: outdoors