Environment, Federal Government, North America, United States, Sustainability
Maximizing Efficiency of Abandoned Mine Remediation Projects
Remediation of mine sites presents distinct challenges that can extend clean-up schedules and stretch the resources of federal agencies, state governments and responsible parties. However, excellent opportunities to maximize remediation efficiencies are available. These opportunities include focusing on time-proven remedies, balancing short- and long-term expenditures, and applying innovative approaches to improve efficiency and sustainability.
- Focus on Time-Proven Remedies. A common factor at many mine sites is the presence of large volumes of source materials (often in the range of 103 to 107 cubic yards). Mining-influenced water (MIW) is generated when rain or snowmelt percolates through the source materials and causes leaching of contaminants into the environment. Source materials are commonly addressed using a low permeability repository or cover system to mitigate MIW generation. Planning for this time-proven remedy should be expedited to prioritize remediation on actions that will provide the most benefit to the environment.
An initial step is identification, characterization and spatial delineation of source materials. A TRIAD approach using field geochemical characterization methods coupled with specialized laboratory analyses greatly increases the efficiency of this phase of the remediation process. Aerial surveying/LiDAR data and 3D computer modeling also provide an efficient means to evaluate excavation and consolidation approaches at large mine sites.
- Balance Short- and Long-Term Expenditures. Remediation of MIW often requires a combination of short-term expenditures to mitigate source materials and long-term expenditures for water treatment. A larger short-term expenditure for control of primary source materials may reduce, though not eliminate, long-term expenditures for water treatment.
Stochastic assessment of the quantity and quality of MIW produced at a mine site facilitates improved analysis of management and treatment approaches. Discounted cash flow analyses should then be conducted to optimize short- and long-term expenditures in a manner that most-efficiently protects human health and environment.
- Apply Innovative Approaches. Innovative approaches such as alternative covers, development of local sources of construction materials, passive interflow diversions (PIDs) and biochemical treatment present further opportunities to maximize efficiency and sustainability of mine remediation.
Alternative covers (also called store and release covers) have been researched by the U.S. Environmental Protection Agency and applied successfully at both landfills and mine sites across the United States. When assessed in relation to both short- and long-term costs, they provide excellent opportunities to improve mine remediation efficiencies. The also improve remedy sustainability, because they are constructed from natural onsite or local materials, and they support development of a diverse and productive vegetation community.
Local sources of construction materials should be developed when possible. Examples include onsite rock quarries to produce riprap and aggregate, and onsite borrow sources to produce growth media. Use of local materials reduces costs, and improves the sustainability of the remedy by reducing energy consumption and greenhouse gas emissions associated with haulage of construction materials to remote mine sites.
PIDs use gravity flow and passive operation to prevent water from interacting with source materials. PIDs improve both the efficiency and sustainability of mine remediation projects by reducing the volume of MIW that must be managed and treated.
Biochemical treatment of MIW, an emerging technology, also has great potential, particularly for treatment of the residual MIW that discharges from many mine waste repositories, a time-proven remedy for mitigation of source materials; and for in-situ treatment of MIW in flooded underground mines and pit lakes.
These approaches present excellent opportunities to reduce costs, expedite project schedules, and improve sustainability of mine remediation projects.