Shannon Speir and Matt Trentman, graduate students in Jennifer Tank’s lab at Notre Dame, lower themselves into a steep, unmodified section of the Shatto ditch. Workers widened nearly five of the ditch’s eight miles, creating a floodplain that slows and filters the water. (Nathanael Johnson / Grist)
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This story also appeared in Grist and The World

MENTONE, Indiana — If you want to clean up the largest pollution spill in the country, one unaltered by decades of work and billions of dollars, you need to spend a lot of time making tiny measurements. Most of them will only confirm the depressing trend: More and more contaminants are winding their way from farms into rivers and streams.

But in one small watershed in northern Indiana, those measurements have revealed an undeniable improvement in one of the most stubborn environmental crises in the world.