The Picher mining district was the site of lead and zinc mining from about 1900 to the mid-1970's. The primary sources of lead and zinc were the sulfide minerals, galena and sphalerite, disseminated in the cherty limestone of the Boone Formation. Water was pumped from the mines while still in operation; however, when mining ceased the mines began to fill with water. Elevated concentrations of metals with depth indicate there may be a substantial quantity of dissolved metals in the ground water. There is concern that the mine water may continue to seep to adjoining portions of the Boone aquifer and to creeks and streams in the area.
Water was sampled from abandoned mineshafts in 2002 in the Picher mining area to assess water quality in the mines and to determine how water quality has changed since the late 1970s when similar sampling was conducted. Specific conductance in 2002 increased with depth in the mineshafts. The increases in specific conductance were very slight until the bottom 20 to 40 feet of the shaft where substantial increases occurred. The pH values in 2002 were generally uniform at the top of the water column and were generally neutral. The lowest pH values were measured at the base of most mineshafts. Concentrations of metals and major ions from samples in 2002 varied with depth and between shafts.
Specific conductance in 2002 samples was less than in 1976-77 samples. The 1976-77 and 2002 data sets for pH had similar median values; however, the pH values from the 1976- 77 had a much greater range. Concentrations of metals, except copper, from water samples collected from the mineshafts in 2002 were significantly less than concentrations of metals from samples in 1976-77.
