The Tar Creek Story
Tar Creek, Oklahoma is a 40 square-mile site contaminated with remains from what was once one of the largest lead and zinc mining operations in the world. Large piles of mining waste, known as “chat” piles, some as high as 200 feet, cover the landscape totaling around 165 million tons over 2,900 acres. Over two-thirds of the original piles have been excavated and used as fill and road gravel, resulting in inhalable dust. Acid mine water now seeps from the former mines into streams that supply the nearby flood plain. See the photo gallery below to get a better idea of what the Tar Creek area looks like today.
The Tar Creek Superfund site is a former mining site located in Ottawa County in northeastern Oklahoma. A part of the larger Tri-State Mining District of Oklahoma, Kansas, and Missouri, this 40 square-mile hazardous zone at Tar Creek affects roughly 30,000 local residents. From the early 1900s until the 1970s, Tar Creek was mined for lead and zinc, which co-occurred with high levels of other toxic metals, such as cadmium, that independently and in combination can adversely affect both human and ecological health. After metal extraction, unusable mine tailings, locally called chat, were dumped into large piles, around which the towns of Picher and Cardin are presently built. The chat piles, while worked multiple times to extract commercially viable amounts of lead and zinc, still contain sufficiently high metal concentrations to be of environmental concern. In addition to the metals from chat piles, the abandoned mines have filled up with ground water and now discharge metal-rich mine seepage to the local streams.
As if that wasn't a big enough problem, rather than leaving about half of the underground area as un-mined "pillars" to support the mines, roughly 90% of the area was mined. As a consequence of this neglect, the mines are beginning to cave in beneath the towns, presenting an immediate physical hazard to community residents as well as worsening the toxic metal "seepage" into the rivers and the deposition of metals from chat in these communities. These toxic metal-laden chat piles, which can be up to 200 feet tall, pose further public health and social justice problems. The land and chat piles are either owned privately or have been federally designated as Native American tribal territory. As the chat renders the land unproductive, some owners have sold chat as a construction material, such as for incorporation into asphalt to pave roads.
Harvard Superfund researcher Dr. James Shine began working in Tar Creek in 2004, studying the environmental pathways that determine how toxic metal wastes from the chat piles and mine seepage move through the environment and ultimately end up in human bodies. In the early 2000s, Harvard was contacted by Rebecca Jim, co-director of the LEAD Agency (Local Environmental Action Demanded), who sought expertise on the impacts of metals associated with mine wastes on human exposures. A key issue was the bioaccessibility of metals, a measure of the potential for human uptake of toxic metals upon exposure. Previous evaluations expected that metals generally had low bioaccessibility because they were in the form of their parent pyrite mineral in the original metal deposits. However these evaluations did not account for the complex interactions that can affect bioaccessibility over the course of time. Dr. Shine's understanding of the biological, chemical, and geological processes that impact bioaccessibility can help establish a more comprehensive method of health risk assessment in Tar Creek.
Through this partnership with LEAD Agency, studies of the dynamics of metal risks at the sites such as Tar Creek were funded by the Superfund Research Program as part of the Harvard Superfund Research Program (Project 5), with a start date of April 1, 2010. Project 5 will address these new questions related to alterations in bioaccessibility over time, while connecting our program to a third site that can also contribute to other existing projects.