What went wrong?
Phosphorus discharges polluted the Minnesota River and suppressed oxygen, affecting fish, plants and other aquatic life.
How was the river rescued?
Tighter rules and major investment cut pollution from sewage and runoff, largely from wastewater treatment plants.
Why does it matter?
Low oxygen levels caused fish kills where the Minnesota and Mississippi rivers widen into Lake Pepin. The "dead zone" in the Gulf of Mexico is blamed in part on pollution from the Minnesota River. The river's health is crucial to the entire food chain downstream.