A site run by Denbury Onshore LLC in southwestern North Dakota has spilled more than 120,000 gallons of oil and wastewater into pastureland after a mechanical failure. Some estimated 17,000 gallons of oil and 105,000 gallons of drilling wastewater containing saltwater and chemicals leaked into pastureland near the city of Marmarth when a tank sensor failed, news agencies quoted state regulators as saying. The tank overflowed on Wednesday, and by Friday, workers were excavating the affected pastureland, which is being equated to the size of a football field.