Snowfall has made its way to North Dakota, adding an element of concern to the ongoing battle over the Dakota Access Pipeline. On Monday, North Dakota Governor Jack Dalrymple ordered an emergency evacuation of protesters working to block the construction of the $3.8 billion pipeline, citing safety concerns with the oncoming winter weather.

This announcement comes just days after the U.S. Army Corps of Engineers issued a letter to the Standing Rock Sioux Tribe, stating that the land they manage north of the Cannonball River will be closed on December 5. Anyone found on the land after that date will be considered trespassers and subject to prosecution.

For several months, the local Native American community and other protesters have been arguing that the pipeline could threaten the reservation’s water supply. But this is actually an updated routing — after the original routing was rejected for similar reasons. The original pipeline was to be routed just north of Bismarck, North Dakota, according to Karen Van Fossan, minister of the Unitarian Universalist Congregation in Bismarck, North Dakota.

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