The North Dakota Department of Health says a light-colored discharge is leaking from a storm sewer outfall on 19th street north of Century Avenue in Bismarck.
The drainage leads into Hay Creek, although they aren't sure whether or not it's reached the creek yet.
They say it's coming from a construction site near the former Home Depot in North Bismarck where a Courtyard by Marriot is being built.
The Department of Health has collected samples and is testing the material.
They say they have also notified the owner of the hotel about the discharge and are taking steps to ensure it doesn't happen again.