HYDROGEOLOGIC CHARACTERIZATION AND MODELING AT TAR CREEK SUPERFUND SITE TO INVESTIGATE THE POTENTIAL EFFECTS OF SUB-AQUEOUS DISPOSAL OF MINE WASTE

The Tar Creek Superfund Site is located along the Oklahoma-Kansas state line in Ottawa County, Oklahoma. The 40 square mile Site is contained within the jurisdictional boundaries of the Quapaw Tribe where significant mining of lead and zinc ores occurred from 1904 through the 1970s. Over the decades, at least 100 million tons of mine waste, or chat, accumulated in large piles on the ground surface. Today, hundreds of chat piles exist with several rising to heights of roughly 200 feet (ft) above the ground surface. In addition to the obvious aboveground remnants of mining, the mining activities left an extensive and predominately interconnected network of flooded underground mine workings.

On February 20, 2008, EPA signed the Record of Decision (ROD) for Operable Unit 4 (OU4) to address the remediation of chat and other mine waste at the Site. The ROD made provisions for the potential injection of chat back into the underground mine workings as a means of permanent subsurface disposal. Since 2008, the Quapaw Tribe has been working along side EPA and its contractors to carry out a hydrogeologlic characterization study of the underlying aquifers. This study is essential not only for assessing the effectiveness and feasibility of chat injection, but also for investigating the potential short term and long term affects of chat injection on the surrounding and underlying aquifers. One of the final products of this study will be the generation and calibration of a groundwater model which can be used to simulate the sub-aqueous injection of chat and to predict its effect on the aquifers in the area, both locally and perhaps regionally.