In 2019, DA Smith (formerly Agapito Associates, Inc. Field Services) was commissioned by the North Dakota Public Service Commission—Abandoned Mine Lands Division, Bismarck, to conduct exploratory drilling for the purpose of locating and characterizing historical underground room-and-pillar coal mine entries beneath active commercial properties near Williston. DA Smith completed a total of 54,722 feet of auger drilling with two rigs and two crews over a three-month campaign. Holes ranged from 50 to 110 feet deep and from vertical to 20 degrees off vertical. Over 12,000 feet of 3-inch-diameter casing was installed in holes that intersected voids in preparation for future grouting. Ten holes were core drilled to obtain continuous samples through previously grouted horizons. Ground water samples were collected in select holes. Sites were restored with grading and gravel after drilling.