The Minnesota Court of Appeals says Renville County must conduct an environmental review to determine whether a proposed drainage ditch improvement could harm one of the last free-flowing creeks in the heavily agricultural western county.

The court Monday reversed a decision by the county board, which concluded the study wasn’t necessary.

The dispute involves proposed improvements to a century-old drainage ditch that empties into the upper reaches of Limbo Creek. The Minnesota Center for Environmental Advocacy says the court ruling sets a precedent that means any drainage project across the state that affects a public water requires an environmental review.