BISMARCK, N.D. (AP) — State environmental officials say a spill of oilfield wastewater caused by a faulty valve has affected some pastureland in western North Dakota.

The North Dakota Department of Environmental Quality said the 12,180-gallon (46,000 liters) produced water spill happened on Saturday at a well pad about 14 miles (22.5 kilometers) east of Watford City. Minot-based Landtech Enterprises notified regulators of the spill on Monday.

State environmental scientist Bill Suess said only about 168 gallons (635 liters) of produced water escaped the well site. He said about 800 square feet (74 square meters) of pastureland was affected. He said no water sources were harmed.

Produced water is a mixture of saltwater and oil that can contain drilling chemicals. It's a byproduct of oil and gas development.

Suess said a berm around the well site contained most of the spill but some escaped through a gate at the facility.