A tanker truck rolled over in Billings County about 4 miles west of Fairfield, spilling an estimated 7,770 gallons of produced water, some of which went into Ash Coulee Creek.

Produced water is a byproduct of oil drilling and occurs when saltwater from the earth is mixed with oil upon extraction.

The truck, owned by Liquid Connections Inc., was transporting the produced water to a saltwater disposal facility when the rollover occured Saturday. The water-hauling company reported the accident the same day.

Spill investigation program manager for the North Dakota Department of Health Bill Suess said that although they do not know how much of the water spilled into the creek, the department does not anticipate any public health risk. The creek, a tributary of the Little Missouri River, is fast flowing, he said, and any spillage will likely be diluted.

He said the samples from the creek that officials collected on Sunday were found to be uncontaminated. Officials installed a sump system to prevent any additional water from entering the creek.

Most of the water, however, spilled into the ditch drainage system along the edge of the roadway, Suess said.

This is not the first spill in the Ash Coulee Creek. In December 2016, approximately 530,000 gallons of oil from the Belle Fourche Pipeline contaminated the creek.