Geotechnical study of an abandoned limestone mine for crude oil storage

The Ironton limestone mine in southern Ohio lies at a depth of approximately 150 m below the surface within the limestones of the Maxville (Mississippian) Formation. The mine was abandoned in 1970 after 60 years of operation. In 1976, the Federal Energy Administration awarded a contract to evaluate the potential of the mine for the storage of crude oil as a part of the U.S. Strategic Oil Storage Program. The paper reviews the geotechnical studies that were undertaken to assess the key questions of whether or not containment of the oil could be assured, and whether or not the mine would remain structurally stable over the life of the storage project.Piezometric data obtained from drilling investigations confirmed that the Maxville limestone, and the over- and underlying formations, were fully saturated. Although some lowering of piezometric levels had occurred over the mine workings, the measured hydrostatic pressures and calculated gradients were found to be sufficiently high to provide positive oil and vapor containment.Based upon in-mine mapping and simple computations, the stability of the mine was determined to be acceptable. It was concluded that bulk oil storage at Ironton mine is technically feasible with minimal costs for remedial geotechnical work.