On Monday, the Minnesota Court of Appeals said state regulators must conduct a further review of the Line 3 project by Calgary-based Enbridge because its environmental impact statement doesn’t address the possibility of an oil spill into the Lake Superior watershed.

The $9-billion replacement pipeline would carry Canadian crude from Alberta across northern Minnesota to Enbridge’s terminal in Superior, Wis., which lies just south of Lake Superior.

The current Line 3, which was built in the 1960s, is increasingly subject to corrosion and cracking, and runs at only about half its original capacity for safety reasons.

Indigenous and environmental groups in the U.S. argue that the project risks oil spills in pristine areas of the Mississippi River headwaters region where Native Americans gather wild rice, and that the Canadian oilsands oil that the line would carry accelerates climate change.