SUBSIDENCE EVALUATION OF TAR CREEK SUPERFUND SITE

The Picher Mining Field of northeastern Oklahoma was the location of extensive lead-zinc mining from 1904 to 1970. Mine waste accumulations and acid mine drainage from the now-abandoned lead-zinc mines have become an environmental issue that has been the focus of environmental restoration activities since 1979. The area was designated by the Environmental Protection Agency (EPA) as the Tar Creek Superfund Site in 1983. Extensive underground openings left from the historic mining activity have also resulted in surface subsidence that presents a serious hazard to public safety, the environment and current and future land use. The subsidence problem has not been systematically addressed as part of the environmental restoration activities. In 2000 Oklahoma Governor Frank Keating established the Tar Creek Task Force to develop a holistic plan for addressing issues identified for the site. Mine subsidence was identified by the Tar Creek Task Force as a major concern, however no funding was provided to implement recommendations of the Tar Creek Task Force. In June 2004, Oklahoma Senator Jim Inhofe requested that an evaluation be conducted to assess the potential for future major subsidence in the area. The U.S. Army Corps of Engineers was designated to be the lead agency on the subsidence evaluation project. A technical team was assembled in August 2004 to begin the subsidence evaluation. The evaluation is nearing completion and will be the largest scale subsidence evaluation ever undertaken to date.

Public safety implications of mining related subsidence have been a concern of residents in the Tar Creek Superfund Site for many years. Shaft related and non-shaft related subsidence events have occurred in the Picher Mining Field since the beginning of mining operations and continue to occur. The Tulsa District Corps of Engineers is actively addressing public safety issues associated with extensive historical mining through an aggressive mine shaft plugging program as well as an unprecedented subsidence evaluation of the area.