Phosphorus, sedimentation make experts worry
Algae-producing phosphorus washing into Lake Pepin has dropped dramatically, but a water quality analyst says that too much of the chemical still makes its way into the lake.
Kris Sigford, water program director for the Minnesota Center for Environmental Advocacy, said she said she worries that phosphorus still can lead to algae that hampers boating and swimming and spur the growth of a toxic algae.
Despite improvements, the level has "gone up and up and up" and Pepin is still "severely impaired," she said. The lake is formally listed under federal Clean Water Act standards as impaired for both phosphorus and turbidity.
The chemical can come from many sources, including hundreds of municipal wastewater treatment plants, farm fields and private septic systems.
During the summer of 1988, with little flow coming into the river and lake, algae bloomed on Pepin. "It stank for days," said Norm Senjem, who is leading the Minnesota Pollution Control Agency's effort to control sedimentation and phosphorus in the lake.
At the time, the biggest contributor of phosphorus was the Twin Cities' major wastewater plant. Since then, Senjem said, upgrades have reduced the plant's levels from about 850 tons of phosphorus a year in 2001 to about 150 tons now.
It's hard to say what effect that has had, however. There have been no summers similar to 1988 with low flows that slow water in the lake, allowing more algae to form, he said.
A plan to control phosphorus coming into the lake began about two years ago but was put on the back burner to concentrate on sediment, which can also bring the chemical into the lake, Sigford said. Right now, "it's just sort of sitting there," she said.
She is calling for better standards. She said the standard should be 60 parts per billion; the MPCA and Wisconsin are looking at 100 ppb.
While waste water plants contribute to the problem, the biggest source of phosphorus is agriculture, Sigford said. The Minnesota River is the biggest player, she said, because it's so large and because land near it is intensively farmed.
The Minnesota Center for Environmental Advocacy wants strict standards and likely would challenge lower standards in court, Sigford said. When the limit is set, farmers will have to cooperate.
"We simply can't get there without ag stepping up to the plate and polluting less," she said.
She hopes Legacy Amendment money and state and federal conservation programs will make change possible.
Some people talk about mandatory standards.
"I've certainly heard a lot of that," Sigford said. "I think that it's very much time for us as a society to say, what do we expect for minimum standards for agriculture?"