Newton County includes portions of the former Tri-State Mining District which spanned approximately 2,500 square miles and included areas of northeastern Oklahoma, southeastern Kansas, and southwestern Missouri. Initial assessments of the site date to 1986 when an environmental investigation was conducted by the EPA. There have been two fund-lead removal actions addressing contaminated soils in residential areas to date for this site. The site has two operable units, or OUs, OU1 and OU2. OU1 is for response actions led by the PRPs centered in the Granby and Spring City/Spurgeon subdistricts. However, the PRPs are no longer conducting response actions at this site and there are no other remaining PRPs. Thus, OU1 is now a fund-lead response. OU2 is for the EPA fund-lead activities in the remainder of Newton County. On September 29, 2003, the EPA placed the Newton County portion of the Tri-State Mining District on the NPL.
In 2019, the EPA obtained new information that some residential properties have contaminated residential yard soil. The primary objective of this action is to eliminate or reduce potential human exposure due to the presence of lead and other heavy metals in residential properties throughout the site.