Contaminants at the Jasper County and Newton County Mine Tailings Superfund Sites are consistent with waste produced through the mining, milling and smelter processes that took place at this location starting in the mid-19th century. Mine production for lead and zinc peaked in 1916 and continued until 1957. Sources of hazardous substances at the site include subsurface sources associated with underground mine workings, and surface sources associated with the placement and disposal of mine wastes. Flooded mine shafts and underground mine workings have exposed mineralized areas, leading to the contamination of groundwater as it has come into contact with ore and subsurface wastes. Injured groundwater estimates at the Jasper County Superfund Site range between 400,000 to 740,000 acre-feet, Newton County impacted groundwater is extensive but unquantified. Contaminated groundwater, in turn, serves as a surficial source as seeps. Other surficial sources of hazardous substances include chat piles, tailing sites, development and waste rock piles, subsidence ponds and contaminated soils. Unvegetated and partially vegetated mine wastes cover over 3,600 acres of the Jasper County Superfund Site. In addition, soils within 200 ft of mine waste piles also contain hazardous substances that are on average several times greater than background soils with maximum concentrations up to three orders of magnitude greater than background. These contaminated soils within 200 ft. of the waste piles cover approximately 4,000 additional acres at the site. Newton County mine wastes have largely been removed by remedial processes and through commercial or unofficial private uses of chat. Mine-impacted lands in Newton County cover approximately 300 acres. All of the PRPs in Newton County have either gone bankrupt or have settled. Therefore, assessment activities at the Newton County Mine Tailings site are complete. Trust natural resources potentially affected by contaminants at the site include federally-listed threatened and endangered species, and migratory birds and their habitat. The threatened Neosho madtom (Noturas placidus) and Ozark cavefish (Amblyopsis rosae) also may have been affected by degraded water quality at the site and loss/contamination of prey base. The reduction in biomass and diversity of aquatic biota in streams and wetlands at the site has also potentially affected migratory birds.