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Locally Led Restoration Efforts Decrease Abandoned Mine Impacts on
Mineral Creek
Waterbody Improved
Runoff from historic mining sites has loaded heavy metals to
Mineral Creek and many other waterbodies within the Upper
Animas River watershed. Because Mineral Creek failed to meet water quality standards for metals
and pH, the Colorado Department of Public Health and Environment (CDPHE) added the creek to the
state's impaired waters list in 1998. Following more than 20 years of characterization, assessment,
monitoring, planning and implementation of best management practices, the copper and zinc
concentrations in the lower segment of Mineral Creek have declined. Fish have also begun to appear
in upper Mineral Creek where they have been absent for as much as a century. The state's most
recent water quality assessments showed that lower Mineral Creek is attaining copper standards. As
a result, copper will be proposed for removal as a source of pollution in Mineral Creek.
Problem
Southwest Colorado's Mineral Creek empties into
the Animas River in the heavily mineralized Silverton
Caldera (Figure 1). This area, often referred to as the
Upper Animas Basin, is characterized by remote, high
elevations (9,200-13,800 feet above sea level), steep
mountains and heavy annual snowfall. The caldera
encompasses the Animas River from below the town
of Silverton to the headwaters, and includes two major
tributaries: Mineral Creek and Cement Creek. (Note: A
release from the Gold King Mine occurred on Cement
Creek, which empties into the Animas River. The
release did not affect Mineral Creek.)
Originally, the region was part of the Ute Indian terri-
tory. Beginning in the 1860s, prospecting and subse-
quent mining resulted in several hundred mines in the
watershed, most of which had ceased operation by the
late 1920s. The largest and last operating mine, the
Sunnyside, shut down in 1991.
One legacy of the past mining activity is the addition of
heavy metai pollution into the streams, beyond what
occurs naturally. Mining exposes ores to water and air,
accelerating the natural processes that create acidic
conditions and release metals such as copper and
zinc from mine waste piles or from abandoned mine
shafts. In the 1990s, participants in the Animas River
Stakeholders Group (ARSG) characterized approxi-
mately 170 mine waste piles and 160 draining mines.
Colorado
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Area Enlarged
Cement
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Animas

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I I Mineral Creek HUC12 Watershed 140801040103
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Attaintment
Not Attaining Cu Std
Attaining Cu Std
Figure 1. Mineral Creek is in southwest Colorado.
These sites were ranked in terms of metal loading. The
group found that 33 of the waste piles accounted for
90 percent of the metal load from all waste piles.
Since 1992, the volunteer-based Colorado River Watch
program and others have collected monthly water
quality monitoring data at a U.S. Geological Survey
(USGS) gaging station near the town of Silverton.
Because data showed that Mineral Creek failed to

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Dis. Zn Cone, at M34
n 300
-85th dZn 1991-mid 1996
-85th dZn 1998-2001
-85th dZn 2007-2011
-Zn Standard 2012-2014
-85th dZn 2012-2014
Jan. Feb Mar Apr May June July Aug Sept Oct Nov Dec
Figure 2. Dissolved zinc concentrations in Mineral Creek have
declined over time.
meet water quality standards for metals and pH,
CDPHE added it to the state's impaired waters list in
1998.
In 2001ARSG proposed water quality standards in
different segments of the Upper Animas Basin based
on at least some remediation of all the top sites noted
above. Those standards were adopted by the Colorado
Water Quality Control Commission. Approximately
27 total maximum daily loads were developed by the
Water Quality Control Division based upon ARSG's
work. Today's water quality standards for the Animas
Basin have changed little since 2001.
Project Highlights
Starting in the 1990s, participants in ARSG initiated
water quality improvement projects using different
financial avenues. Most of the 33 mine waste sites
have been reclaimed; of these, many used Clean
Water Act (CWA) section 319 program funds. Overall,
about 60 projects to control mining-related nonpoint
sources have been completed in the Upper Animas
Basin. In addition to numerous watershed planning
and outreach activities, ARSG partners implemented
nine water quality restoration projects in the Mineral
Creek watershed between 1997 and 2015. Three
separate projects in the Carbon Lakes area involved
removing mine waste from the stream channel,
developing water diversions, and restoring the creek
channel and wetlands to recreate natural hydrology
to help remove pollutants. Projects at the Congress,
San Antonio, Brooklyn, Upper Browns, and Silver Ledge
mines involved removing/consolidating mine waste,
capping mine waste piles, re-channeling drainage ways
and adding other hydraulic controls around waste pile
areas, neutralizing residual mine waste, and planting
vegetation on bare areas. The last project conducted
s "
fl 10
Copper Concentrations in Mineral Creek
as Compared to Standard
• v •
11/18/2010	4/1/2012	8/14/2013	12/27/2014	5/10/2016
Sample Date
Figure 3. Copper Levels in Mineral Creek are meeting
standards (orange line).
in the watershed was a project at the Bullion King
Mine that included consolidating mine waste, capping
the waste and installing drainage way controls.
Results
Both ARSG and the state have assessed the water
chemistry data collected at the USGS gaging station
near Silverton. According to ARSG, the decline in dis-
solved zinc concentrations between the 1991-1996
and 2012-2016 monitoring periods varies from month
to month but is generally 60-70 percent less (Figure
2). Reductions in dissolved copper concentrations
are very similar in magnitude to zinc and now the
waterbody meets copper standards according to the
state's assessment (2016) of the recent 5-year period
of record (Figure 3). As a result, copper is proposed for
removal as a source of pollution in Mineral Creek.
Partners and Funding
In cooperation with ARSG, approximately $1.15 mil-
lion in CWA section 319 funding was used for projects
in Mineral Creek. Cash and in-kind match, estimated
at up to $5 million for the entire Upper Animas River,
came from numerous state stakeholders, including the
Colorado Division of Reclamation, Mining and Safety;
Colorado Division of Parks and Wildlife; Colorado
Geological Survey, and the River Watch Program.
Local stakeholders include the San Juan Resource
Conservation and Development Council, Southwest
Water Conservation District, town of Silverton,
San Juan County Commissioners, San Juan Citizens
Alliance, and Sunnyside Gold Corporation. The U.S
Environmental Protection Agency, USGS, U.S. Forest
Service, and U.S. Bureau of Land Management have
also collaborated on the restoration efforts.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-18-00100
November 2018
For additional information contact:
Bonie Pate
Colorado Department of Public Health and Environment
303-692-3557 • bonie.pate@state.co.us

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