Innovative Approaches to Assessment and Cleanup of Mining Sites

A Quick Look
The inclusion of MSLs in the Brownfields Program strengthens existing mine reclamation programs.
The addition of residuals to soils at abandoned mine sites can help to rebuild the soils in support of further revitalization.
The Triad approach has proven useful in addressing various types of contamination present on abandoned mine lands.
Other innovative approaches are being demonstrated to support remediation of abandoned mine lands.

Background

The enactment of the Small Business Liability Relief and Brownfields Revitalization Act expanded the definition of brownfields to include mine-scarred lands (MSL), making these properties eligible for the benefits of the Brownfields Program. MSLs are defined as lands, associated waters, and surrounding watersheds where extraction, beneficiation, or processing of ores and minerals (including coal) has occurred. It is estimated that there are more than 500,000 abandoned mining sites composed of hard rock and coal mines located on both public and private land across the United States that involve complex economic, social, and environmental issues. MSLs have become a persistent problem in many communities because of the economic and environmental challenges of cleaning up and reusing the lands.

The inclusion of MSLs in the Brownfields Program strengthens existing mine reclamation programs administered by the U.S. Department of Interior’s (DOI) Office of Surface Mining. The Surface Mining Control and Reclamation Act governs surface coal mining activities and established the abandoned mine land reclamation fund. The MSL Working Group, which is composed of six federal agencies, is co-chaired by EPA’s Office of Brownfields Cleanup and Redevelopment and DOI’s Office of Surface Mining. The MSL Working Group was established to collaboratively address the challenges of MSL cleanup and revitalization.

Hard Rock Mining – Remediation Through Addition of Residuals

Several EPA Superfund sites were contaminated by hard rock mining. At some of these sites, contaminated soils are being addressed through use of residuals. Examples of processes that generate potentially useful residuals include dairy, swine, and chicken farming; wastewater treatment; drinking water treatment; phosphorus production; pulp and paper production; sugar beet processing; and energy production from coal or wood. The residuals can readily contribute to rebuilding soil through their ability to re-establish structure and function by adding organic matter and nutrients to the disturbed soils. As a result of recreating a fertile soil horizon, the soil microbial community, invertebrates, and plants will be re-established and it will be possible to attain a self-sustaining system. More importantly, in the proper amendment ratios, residuals can be used to address problems of metal toxicity and acidity. In addition to residual use at upland sites, materials such as wood ash, log yard debris, and biosolids compost have been used to correct toxicity in a tailings pond in order to re-establish wetland functions.

Use of Triad Approach

Various types of contamination associated with coal mining may be addressed using the Triad approach, including contamination related to waste and ash disposal areas, on-site industrial facilities, chemical and solvent storage equipment, buildings and electrical transformers, petroleum storage and usage equipment, and acid mine drainage. Systematic planning, dynamic work strategies, and real-time measurement were applied to several aspects of the investigation.

BTSC provided technical assistance for a pilot project at the Dark Shade Brownfields Site in Somerset County, Pennsylvania. The project focused on applying the Triad approach to investigation activities. The planning was based on a reuse scenario that includes reclamation of the buildings located on site as office space or for other industrial applications. The objectives for the Phase II investigation are as follows:

• Identify whether contaminants are present at concentrations above Act 2 industrial reuse levels in soil and surface water inside and outside the existing structures
• Identify whether disposal or recycling restrictions must be considered prior to removal of existing equipment from the buildings
• Identify whether the configuration of the groundwater flow regime in the area suggests that basement flooding has resulted from groundwater infiltration or an influx of surface water
• Identify options for removal and disposal of the water currently present in the flooded basements of the existing structures
• Identify whether groundwater sampling and analysis activities need to be performed and, if so, for what constituents
• Determine what remediation, if any, should be considered

The following areas were identified for application of the Triad approach:

• Collecting wipe, surface water, soil, and groundwater samples to evaluate the potential presence of PCB-containing oil in or on the existing transformers and other machinery
• Evaluating whether the water in flooded basements is contaminated with PCBs, solvents, polynuclear aromatics, or petroleum hydrocarbons (concentrations contaminants of potential concern) at concentrations that would require special handling of water during its disposal or could indicate the presence of a source
• Establishing the lateral and vertical extent of contaminants of potential concern in unsaturated soil
• Estimating the direction of groundwater flow and depth to groundwater beneath the site

Other Innovative Approaches

EPA and other organizations continue to demonstrate and evaluate innovative technologies for the reclamation of mining sites. EPA is developing a primer on mining that will include an overview of innovative approaches that are suitable for consideration for mining sites.

Additional information is available at www.epa.gov/superfund/programs/aml.

Sunday, September 7, 2008