HISTORY AND ENVIRONMENTAL IMPACTS OF THE PIERSON CREEK SUB-DISTRICT, TRI-STATE MINING DISTRICT, SW MISSOURI

The Tri-State District in Missouri, Kansas, and Oklahoma was a global leader in zinc (Zn) and lead (Pb) production. A unique characteristic of the district was the large number of small companies and local sub-districts involved in mining and milling. The purpose of this paper is to review and evaluate the history and environmental legacy of mining activities associated with the Pierson Creek sub-district (14 km²) located on the southeast side of the City of Springfield in southwestern Missouri. Sphalerite and galena mineralization was typically hosted by a shale unit within Mississippian carbonate rocks along a northwest trending fault zone. In 1919, Schoolcraft observed the Delaware Indians mining and smelting float galena along lower Pierson Creek (58 km²). Mining by European settlers began in the sub-district around 1844 with deep shaft mining starting in 1885, peaking from 1912 to 1916, and ending in 1920. Approximately 40 mines and prospects were in the sub-district with 0.7 km² of tailings and several open shafts still remaining today. In 1915, mining activities along Pierson Creek were responsible for fish-kill and tailings sedimentation problems extending into the main channel of the James River. Floodplains along Pierson Creek below mine sites are presently contaminated to depths >2 m and contain up to 12,000 ppm Zn. Overall, about 141,000 Mg of contaminated sediment is stored in floodplains along lower Pierson Creek including 91 Mg Zn and 22 Mg Pb. Today, contaminated sediment released from Pierson Creek increases sediment Zn concentrations by 5x over background in the James River with effects extending almost 8 km downstream into Lake Springfield. As expected, James River floodplains below the confluence of Pierson Creek are also contaminated at depth and mining metal profiles have been used as stratigraphic tracers to date alluvial deposits and estimate historical overbank sedimentation rates due to historical land use changes.