Earth System Science News

Researchers with the U.S. Geological Survey (USGS) have
evaluated what different geologic, hydrologic, and biologic studies are most
effective in cleaning up the watersheds affected by mining in southwest Colorado, and recently
published their findings on-line and in print. 
USGS Professional Paper 1651, “Integrated Investigations of
Environmental Effects of Historical Mining in the Animas River Watershed, San Juan County, Colorado.”

Acid drainage and toxic metals are a legacy of mining in
many mountain watersheds throughout the western United States.

Application of the watershed approach has shown that it
provides a cost-effective method for selecting abandoned mines for cleanup and
restoration that can be applied by Federal, State, and local stakeholders
groups and private entities.

This study demonstrates that a complete understanding of
the nature and extent of hydrothermal alteration associated with the mineral
deposits and the effect this alteration has, or had in the past, on water
quality and native habitat must be carefully evaluated prior to initiation of
remedial actions.  The presence of
extensive hydrothermal alteration exposed at the surface in the watershed
limits the amount of biological recovery that reasonably can be expected and
dictates the methods and costs of remediation projects.

The USGS report describes multidisciplinary studies of the
geology and geochemistry of rock and sediment, the hydrology and water
chemistry of streams and ground water, and the diversity and health of aquatic
and terrestrial organisms in the Animas
River watershed.  The studies inventoried historical mines;
defined geologic, structural, and geomorphological conditions that control
acidity and release of potentially toxic trace elements; assessed fish
distribution and habitat; collected and chemically analyzed hundreds of water,
sediment, and mine- and mill-waste samples; conducted toxicity tests; analyzed
macroinvertebrate and trout populations and biofilm to evaluate ecosystem
health; defined hydrological regimes; evaluated plausible sources of trace
elements to streams; and provided all data and maps in digital formats.

Studies in the 1,096-page report were conducted by USGS
researchers as part of the Abandoned Mine Lands (AML) Initiative over a course
of five fiscal years, 1997 to 2001. The AML was designed to provide technical
assistance in support of Federal Land Management Agency (FLMA) actions to
remediate contamination associated with abandoned hard rock mining activities
and was part of a larger strategy by the U.S. Department of the Interior and
the U.S. Department of Agriculture to coordinate activities for the cleanup of
federal lands affected by AML. The strategy employed a watershed approach, in
which contaminated sites were identified and remediated based on their effect
on the water and ecosystem quality of a targeted watershed.

“Watersheds can have
hundreds of active and abandoned sites that are potential sources of
contamination. In order to demonstrate environmental improvements in a timely
and cost-effective manner, the Federal agencies need to plan and implement
remediation that is scientifically based, efficient, and invests resources
where they would do the most good.  In
response to these needs, the USGS initiative developed a watershed approach, in
which contaminated sites were prioritized and remediated based on their effect
on the water and ecosystem quality in the affected watershed,” said Stan
Church, USGS scientist and lead scientific editor of the report.

Read a companion study on the Boulder
River basin in southwestern Montana, USGS
Professional Paper 1652.

View a complete list of all reports prepared during the AML
Initiative.