Cleaning up Contamination in Hard Rock Mine Lands
The USGS Abandoned Mine Lands Initiative is developing and demonstrating
scientific knowledge and technologies that will assist Federal land management
agencies to clean up contamination in areas near abandoned hardrock mines
across the Nation. The Initiative is being conducted in two pilot watersheds,
the Upper Animas River watershed in Colorado and the Boulder River watershed
in Montana, where the USGS is partnering with the U.S. Forest Service,
Bureau of Land Management, U.S. Environmental Protection Agency, and State
agencies in Colorado and Montana. These agencies are using USGS scientific
information to prioritize and design cleanup activities in the watersheds.
The Initiative's contributions to the abandoned mine land problem include:
- Tracer
tests, in which a tracer such as a salt is put into a stream and
its downstream movement is measured. Tracking how the salt is diluted
in the stream gives information on how much water is being added to
the stream. These tests are successfully identifying the largest sources
of contamination from abandoned mine lands, and are enabling efficient
targeting of cleanup activities.
- Water quality and flow measurements that define seasonal and other
temporal variations in contaminant movement. Such studies show that
zinc levels in the upper Animas River exceeded, on approximately 354
days a year, the standards proposed by the Colorado Water Quality Control
Division.
- Methods to determine the environmental conditions that existed before
mining began in order to establish realistic cleanup goals. In some
mined areas, water quality was affected by the natural weathering of
mineral deposits before mining occurred.
- Documentation of the downstream movement of metal contamination associated
with ultra-fine particles that accumulate in the bottom sediment of
rivers and streams. This method of contaminant migration was found to
be a significant source of exposure of toxic metals to aquatic organisms.
- Findings that metal concentrations in fish and aquatic insects were
higher than in the surrounding water and bottom sediments, indicating
that metals (some of which are toxic) are accumulating in the local
food chain.
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