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WATERSHED-SCALE REMEDIATION AND RESTORATION MONITORING IN THE TRI-STATE LEAD-ZINC MINING DISTRICT

Since late 2004, CREW research team members have evaluated the sources, transport and fate of mine waste contaminants at the Tar Creek Superfund Site, Ottawa County, OK, a site characterized by contaminated surface and ground waters, soils, mining wastes (both waste rock or chat and flotation tailings), and air. A mass-balance approach has been utilized, examining the mass flux of water and associated constituents from mine waste sources to various environmental media. The objectives of this environmental monitoring and remediation effort are to: 1) provide relevant and meaningful data on baseline environmental conditions, 2) allow an initial assessment of the potential effectiveness of various remediation technologies, 3) design, implement and evaluate pilot passive treatment systems at selected contaminated mine drainage discharges, and 4) direct future environmental data collection efforts as remediation and restoration efforts proceed over the foreseeable future. The work is being conducted with colleagues from the Oklahoma Climatological Survey, University of Oklahoma Health Sciences Center Department of Occupational and Environmental Health and U.S. Geological Survey (which provides funding). This project includes multiple tasks. Several CREW graduate students have completed or are working toward theses related to this project. Click here to see additional information. Overall project tasks include:

  • Artesian mine drainage discharges, waste pile and tailings pond runoff and in-stream contaminant mass loadings have been characterized through a regular and comprehensive water quality and quantity monitoring program in four mining-impacted watersheds (Tar, Lytle, Beaver and Elm Creeks) and four reference watersheds (Coal, Cow, Little Elm and Garrett Creeks).
  • Surface water impacts in streams and wetlands have been evaluated through biological, chemical and physical habitat characterizations.
  • A field assessment of chat (metal-contaminated waste rock) use in an asphalt test road has been completed, including road runoff, intact and milled asphalt and air quality. Road construction was funded by another source.
  • A comprehensive cavernous mine water flow study was conducted in the Beaver Creek watershed. Interactions between the mine pool, artesian discharge points, and surface waters were examined.
  • Land reclamation activities, conducted by other entities, were evaluated through pre- and post-reclamation sampling and analyses of surface soils
  • Meteorological monitoring, through development and deployment of five Portable Atmospheric Research Micrometeorological Stations (PARMS) was conducted to assist with water budget calculations. Work was conducted by OCS.
  • Targeted air quality evaluations were conducted in the laboratory by OUHSC.
 

DESIGN, CONSTRUCTION AND EVALUATION OF A LARGE MULTI-CELL PASSIVE TREATMENT SYSTEM FOR FERRUGINOUS LEAD-ZINC MINE WATERS

Artesian discharges of net alkaline, ferruginous waters from abandoned underground lead-zinc mines cause considerable surface water degradation at the Tar Creek Superfund Site, part of the historic Tri-State Mining District of Oklahoma, Kansas and Missouri. Two perennial borehole discharges, identified as the lowest elevation mine water discharge points in the district, have flowed unabated for almost 30 years and considerably degraded the physical, chemical and biological integrity of a first-order tributary to Tar Creek. Since 1998, OU personnel have periodically monitored these discharges and the receiving stream. Since 2004, CREW research team members have conducted a comprehensive water quality and quantity characterization study with a goal to design, construct and evaluate a passive treatment system under an agreement with the U.S. Environmental Protection Agency. The work is being conducted with colleagues from the OU Department of Zoology and Oklahoma Biological Survey. The objectives of this project include: i) remediation of polluted mine waters to acceptable quality for maintenance of the receiving water body aquatic community, ii) demonstration of the first installation of a mine water treatment facility of any kind at the Tri-State Mining District, and iii) technology transfer to speed application of this technology to other locations in the district.

A conceptual design was developed to effectively address approximately 1000 L/minute of mine water flowing from these abandoned boreholes (pH 5.95±0.06, total alkalinity 393±18 mg/L CaCO3, total acidity 364±19 mg/L CaCO3, Fe 192±10 mg/L, Zn 11±0.7 mg/L, Cd 17±4 ug/L, Pb 60±13 ug/L and As 64±6 ug/L). Via a competitive bidding process, an engineering design and construction award was made to CH2M-Hill in 2006. Construction began in July 2008 and was completed in December 2008. The passive treatment system (~ 2 ha total surface area) includes an initial oxidation pond followed by parallel treatment trains (to facilitate research and experimentation) consisting of aerobic wetlands, vertical flow bioreactors, oxidation ponds (with active re-aeration via wind and solar power) and horizontal-flow limestone beds. Waters from the parallel trains are recombined in a polishing wetland prior to final discharge. Total design surface water elevation change in the entire system is approximately 1.8 m. Prior to system implementation, the abandoned boreholes required rotosonic over-drilling to establish hydraulic control. In addition, diversion of storm water flows from an approximately 470-ha upgradient watershed was necessary. During construction, a third mine water discharge was discovered and incorporated into the design. This system represents a state of the art ecological engineering research site for passive treatment of mine waters. Evaluation is ongoing and includes the following tasks:

  • Water quality changes through both inflow/outflow analyses for each process unit, spatial analyses and specific in situ experiments dealing with iron oxidation and settling kinetics, sulfide formation and retention, and other biogeochemical processes.
  • Substrate pore waters analyses, especially for the vertical flow bioreactors and horizontal flow limestone beds.
  • Microbial activity evaluation in the wetlands and bioreactors.
  • Assessment of ecological structure and function in all process units with an emphasis on vegetation.
  • Continued analyses of receiving stream biogeochemistry, fish communities and macroinvertebrate communities.
  • Evaluation of potential for bioaccumulation through on-site analyses and in conjunction with a project-specific Wildlife Advisory Group that includes Oklahoma Department of Wildlife Conservation personnel.

 

 

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