Rehabilitating a Former Mine Site

The Oronogo-Duenweg Mining Belt in Jasper County, MO, is part of the Tri-State Mining District that encompasses approximately 2,500 square miles of land in southwestern Missouri, southeastern Kansas and northeastern Oklahoma. The Oronogo-Duenweg site is a US Environmental Protection Agency (EPA) Superfund site estimated to contain 150 million tons of mining waste. Mining, milling and smelting of zinc-lead ores began in the area in the 1850s and continued through the 1970s, resulting in contaminated surface soil, tributary sediments and surface water.

GeoEngineers provided management and oversight services for remedial action on five parcels of land within the Oronogo-Duenweg site.  The EPA’s Record of Decision, the public document outlining the approved remedial action for cleaning up the site, required  excavating and disposing of all contaminated soil, sediment and former milling and mining source material under water in an open-pit mine. Required cleanup for the site also included backfilling and capping of approximately six mine shafts and small pit features on the five parcels GeoEngineers serviced.

Services provided include:

• Coordinating with the remedial action contractor for planning, scheduling and execution of the cleanup
• Collecting, reviewing and validating all samples in strict accordance with the EPA’s Quality Assurance Project Plan
• Overseeing  surveys before and after excavation to determine volumes moved
• Serving as the Engineer of Record for the project

Approach

Our environmental team worked with a remedial action contractor who moved almost a million yards of material during the project. In our quality-assurance, quality-control role, GeoEngineers performed sampling of excavated areas and fill materials onsite during excavation using a hand-held X-Ray Florescence (XRF) instrument to obtain contaminant levels of the soil, sediment and source materials. Based on our soil testing to determine what areas needed excavating, the remedial action contractor removed contaminated materials (those with readings of zinc, cadmium or lead above approved action levels) and took them to an open-pit mine where they were subaqueously disposed as per the Record of Decision. For materials with readings well below approved action levels, our team gathered formal samples following an EPA-approved sampling and analysis plan, and tested them at our laboratory in Springfield, MO.

Results

The five parcels of land GeoEngineers helped remediate now meet residential soil standards, making them available for future development. Much of the area is being restored to grasslands, with wetlands and ponds being created on the rest.  The project was completed on schedule and with no lost time due to injury.