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Presentation Overview: |
This webinar features three presentations on mining-influenced water (MIW) treatment delivered at the 2014 National Conference on Mining Influenced Waters. The session focuses on approaches to MIW treatment, operations and maintenance (O&M) challenges, and characterization and remediation of MIW treatment issues at two Superfund sites.
- Iron Mountain Mine Superfund Site — Long Term O&M Challenges
Presented by James Sickles, EPA Region 9
Nearly 100 years of mining at the Iron Mountain Mine Superfund Site in Shasta County, California resulted in extensive workings and fractured rock, creating pathways for air and water to oxidize the massive sulfide ore. This resulted in the development of MIW with pH as low as -3.6 and the release of tens of thousands of pounds of heavy metals per day into the surrounding drainages and water bodies, before remediation reduced metals loading by more than 97%.
Unusual O&M issues at the site comprise: (a) the formation of mineral precipitates in MIW conveyance pipelines; (b) the accelerated deterioration of the urethane liner for the Upper Spring Creek Diversion, which diverts uncontaminated water to Flat Creek; (c) the significant loss of filtrate from the lined Brick Flat Pit that is used to store the high density sludge from the treatment plant, suggesting that the landfill is leaking into mine workings below; and (d) the ongoing deterioration of the concrete ore chute plugs in the Richmond Adit along with the location of the Lawson Adit in the Boulder Creek landslide, both of which are key parts of the MIW collection systems.
- Characterization and Remediation of Iron(III) Oxide-Rich Scale in a Pipeline Carrying Acid Mine Drainage at Iron Mountain Mine, California, U.S.A.
Presented by Kate M. Campbell, U.S. Geological Survey
A pipeline carrying acid mine drainage (AMD) to the treatment plant at the Iron Mountain Mine Superfund Site (California, U.S.A.) has developed substantial scaling over the past several years, resulting in spillage of AMD and requiring frequent and costly clean-out. The objectives of this work are to characterize the pipe scale composition, identify biogeochemical processes leading to its formation, and identify possible strategies to prevent or retard its formation in the pipeline.
Samples of the scale and AMD water samples from five points along the pipeline were collected prior to clean-out during a low-flow period in August 2012. Additional AMD samples will be collected at various times during high-flow conditions to evaluate seasonal variation in water chemistry and possible effects on scale formation. The mineralogy and microbial community of the scale samples were characterized. A biogeochemical model using PHREEQC was developed to simulate the rates and processes involved in scale formation. Potential remediation options to prevent scale formation are to lower the pH of the influent AMD by continuously mixing it with water from the Richmond portal (approximate pH 0.5-1.0) or to periodically flush the pipeline with Richmond portal water. The potential viability of these options will be evaluated in laboratory batch experiments with AMD from the pipeline and the Richmond portal, mixed with scale removed from the pipeline.
- Tackling AMD, Mining Impacted Groundwater, Private Mine Ownership in a Superfund Site that Spans the Panhandle
Presented by Bill Adams, Kim Prestbo, and Ed Moreen, EPA Region 10
The Bunker Hill Mining and Metallurgical Complex Superfund Site, listed on the NPL in 1983, is located within one of the largest and most productive historical mining districts in the world. Historic disposal practices led to the mining-related hazardous substances being dispersed in nearly every aspect of the environment. As a result of the cleanup actions undertaken by EPA and the Idaho Department of Environmental Quality to address exposure to lead and other heavy metals, excellent progress has been made from both aesthetic and risk reduction standpoints. However, significant loading of dissolved metals continues to occur and many more years of work are necessary to fully achieve the cleanup goals for human health and water quality standards.
This presentation will provide a brief history of this well-known site, including EPA ownership and management of the water treatment plant. It will also provide an in-depth look at the 2MGD+ Acid Mine Drainage water quality (the groundwater collection system being designed that will almost double the flows to be treated at the Central Treatment Plant), and discuss a recent optimization study and value engineering exercises that were pursued to ensure the most cost effective remedial action.
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