The state Health Department is monitoring the cleanup of a produced water spill in Mercer County.

Produced water is a mixture of saltwater and oil that can contain drilling chemicals.

Officials say a valve failure led to the spill of about 6,300 gallons (23,848 liters) from a tank being used in a carbon storage study conducted by the University of North Dakota Energy and Environmental Research Center.

The spill was discovered Saturday about 2 ½ miles north of Golden Valley. Officials say less than 210 gallons left the tank pad.