The Weldon Spring Site is located in St. Charles County, Missouri, about 30 miles west of St. Louis. The site comprises two geographically distinct properties owned by the Department of Energy (DOE): the Weldon Spring Chemical Plant and Raffinate Pit Sites and the Weldon Spring Quarry Site. The Chemical Plant is located about 2 miles southwest of the junction of Missouri State Route 94 and U.S. Highway 40/61. The Quarry is about 4 miles southwest of the Chemical Plant.