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Long-Term Monitoring of Permeable Treatment Wall Demonstration
Figure 9. Installation of the fishbone,
apatite treatment system at the Nevada
Stewart Mine site.
Primary Issue Addressed: Acid Drainage/Water Treatment
Secondary Issues Addressed: Characterization, Modeling, Neutral Drainage
Project Site: Nevada Stewart Mine is located in Shoshone County near the headwaters of the Highland Creek drainage approximately 5 miles south of Pinehurst, Idaho.
Collaborating Entities: MSE, U.S. Department of Energy (DOE), U.S. Environmental Protection Agency (EPA) Region 10, and Golder and Associates
Cost Share: None
Figure 10. Total amount of metals taken out of the Nevada Stewart
Mine water as it flowed through the fishbone apatite
system over 22 months.
Project Description
The objective of this project was to demonstrate a technology that uses fishbone apatite treatment media (Apatite II) to passively remove zinc from a mining-impacted water. This site consists of an adit and several surface waste piles. Approximately 5,200 cubic yards of mine waste were previously removed by the U.S. Bureau of Land Management (BLM) from the site and disposed in the Central Impoundment Area at the nearby Bunker Hill Site. BLM contoured the site to prevent erosion and further contaminant loading to the receiving stream, Highland Creek. Approximately 40 to 60 gallons per minute of water discharge continuously from the Nevada Stewart Mine adit into Highland Creek. Analytical results indicate high levels of dissolved zinc, manganese, and iron in the soils and adit discharge.
In the initial stages of the project, under DOE funding, a fully contained subsurface retention basin and treatment system were designed to capture and treat a specified volume of water discharging from the Nevada Stewart Mine (see Figure 9). By placing the treatment media into a contained subsurface retention system, several advantages over vault and barrier systems were gained, which include:
- significant odor control;
- protection from freezing;
- protection from vandalism and damage from animals;
- ability to change out treatment media;
- ability to accurately monitor inflow/outflow and water quality to determine metals loading; and
- decreased landscape impacts.
The work performed using Mine Waste Technology Program (MWTP) funding included monitoring the system and the nearby receiving stream. The MWTP was tasked with defining a baseline metals concentration and then determining the percent reduction of dissolved metals in the effluent from the apatite treatment system over a 2-year period.
Status
The Nevada Stewart Mine was selected for implementation of the technology in August 2002, and construction of the apatite treatment system was completed at the end of September 2002. Treatment of the Nevada Stewart adit discharge began on October 1, 2002, and the flow through the system was 18 gallons per minute.
After monitoring the apatite system over a 22-month period, approximately 334 pounds of zinc, 126 pounds of iron, and 34 pounds of manganese were removed from the effluent water entering Highland Creek, see Figure 10. The final project report is currently being developed.