ECOLOGICAL REVITALIZATION OF CONTAMINATED SITES CASE STUDY
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ECOLOGICAL REVITALIZATION OF CONTAMINATED SITES CASE STUDY
cadmium, and zinc concentrations are now
greatly reduced. Stable stream banks with
minimally intrusive engineering materials that
support native plants were created to replace
the eroding tailings. Approximately 210 acres
of the contaminated soils were converted to
pasture and recreational lands. As a result of
this ecological revitalization, cattle grazing
has resumed on land that was barren for
more than 80 years and a public recreation
area with trails, river access, and fishing areas
now operates on remediated fluvial tailings
deposits. Fly fishing enthusiasts now enjoy a
scenic panorama of native grasslands in the
floodplain.
Background
The California Gulch Superfund site was
listed on the National Priorities List (NPL)
in 1983 and consists of about 16 square
miles in Lake County, Colorado. Operable
Unit 11 (OU11) includes the Arkansas River
from the confluence of California Gulch
downstream to the confluence with Box
Creek, approximately 9 miles downstream.
The site encompasses both private and
public lands.
Mining, mineral processing, and smelting
in and near Leadville produced gold, silver,
lead, copper, manganese, and zinc for more
than 130 years. Wastes generated during
the mining and ore processing contained
metals, such as cadmium, copper, lead, and
zinc.
Wastes were washed downstream and
deposited as discrete parcels along an 11-
mile stretch of the Upper Arkansas River.
The fluvial deposits are pyritic soils with no
natural soil structure and are characterized
by lack of vegetation, low pH, and high
metals.
Over the years, the wastes eroded, re-
deposited along the river, and accumulated
in deposits up to 4 feet deep. The rise and
fall of the water table resulted in alternating
reducing and oxidizing conditions, creating
an extremely acidic soil pH (1.5 to 4.5).
Eroding streambank prior to treatment
What are Pyritic Soils?
Pyritic soils contain pyrite, which is a
mineral also known as "fool's gold." Pyrite
is used to produce iron ore and sulfuric
acid, and when it is present in the soil, it
can cause the soil to be acidic.
The fluctuating water table and the acidic
conditions, in turn, caused zinc and lead
in the tailings to form soluble salts that
wick to the soil surface during dry portions
of the year. A metal salt crust with zinc
concentrations of greater than 90,000
milligrams per kilogram (mg/kg) formed
on the soil surface. The soil was toxic to
riparian vegetation and became highly
susceptible to continued erosion by the
river.
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Why Not Just Remove
the Waste Deposits?
Removal of the tailings was not feasible
because of (1) the potential to destabilize
streambanks and cause massive changes
in the river system, (2) the potential for
tailings to enter the river during field
activities, (3) the high cost of replacement
topsoil, and (4) the difficulty of locating
an acceptable repository for contaminated
soil.
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California Gulch, Lake County, Colorado Superfund Case Study
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ECOLOGICAL REVITALIZATION OF CONTAMINATED SITES CASE STUDY
Streambank after treatment
Irrigation with contaminated water
from the Arkansas River impaired the
productivity of adjacent ranch lands,
causing reduced forage and increased
exposure of livestock to toxic concentrations
of metals contaminants.
Ecological Revitalization
Initial Research and Field Studies
The Region 8 Removal Program, EPA's
Environmental Response Team (ERT),
and USDA researchers initiated ecological
revitalization at the site in 1998 by developing
a recipe of biosolids and lime to be applied
to the fluvial deposits. The intent of these
amendments was to reduce the mobility,
bioavailability, and toxicity of metals in
the soil and provide a more hospitable
growth environment for vegetation and soil
organisms. The amendments were applied
to four "demonstration areas" using a front-
end loader and mixed into the top 12 inches of
tailings using an industrial disc, a plow, or an
excavator. The plots were seeded and in some
cases irrigated because of the low precipitation.
The resulting vegetation in the demonstration
areas reduced the following: erosion, exposure
to contaminants, formation of metals salts on
the surface and subsequent leaching into the
river, and transport of metals to groundwater.
Subsequent demonstration areas were treated
with various combinations of biosolids pellets,
biosolids compost, cow manure compost,
limestone, and sugar beet lime. Test plots were
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Biosolids, or organic residuals, have been
used at a wide range of sites both alone
and in combination with other materials
to restore disturbed sites. Research
has consistently demonstrated that
biosolids are highly effective, in many
cases more so than topsoil replacement,
for restoration of disturbed ecosystems.
In addition, biosolids, applied at
restoration rates of more than 50 tons
per acre, provide sufficient organic
matter to improve the physical properties
and nutrient status of the soil, while
reducing the availability of metals. Some
additional examples of Superfund sites
where biosolids have successfully been
used include the following:
West Page Swamp (Bunker Hill),
Shoshone County, Idaho:
http://faculty.washington.edu/clh/wet.
html
Palmerton Zinc Pile, Carbon County,
Pennsylvania:
http://www.epa.gov/aml/tech/
palmerton.pdf
Sharon Steel, Mercer County,
Pennsylvania:
http://www.epa.gov/reg3hwmd/npl/
PAD001933175.htm
Oronogo-Duenweg Mining Site,
Jasper County, Missouri:
http://www. itrcweb. org/miningwaste-
gu i dance/cs34_or on ogo_du en weg. p df
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installed in these subsequent demonstration
areas to evaluate the relative merits of various
lime amendments and of adding wood chips to
the treated soil.
Extensive evaluation of the physical and
chemical properties, toxicity, and function
of soil, and of ecosystem function suggested
that the soil amendments have restored
function to the fluvial deposits. After 1 year,
the addition of lime and biosolids generally
improved soil quality, increased pH, decreased
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California Gulch, Lake County, Colorado Superfund Case Study
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ECOLOGICAL REVITALIZATION OF CONTAMINATED SITES CASE STUDY
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Consider the Potential for
Attractive Nuisance Issues
Assessments such as chemical extraction
tests, ecological evaluation, and modeling
can be used to ensure that a remedy is
protective of both humans and wildlife.
At the California Gulch OU11 site, for
example, a wide range of earthworm, fish,
and small mammal testing was conducted
to determine whether the revitalized
habitat was creating an attractive nuisance
to the wildlife at the site. Results showed
that the bioavailability of heavy metals
present on site was dramatically reduced
after treatment with soil amendments and
that wildlife exposure to metals is within
acceptable limits. For additional details on
attractive nuisance issues, please visit the
following website: http://www.epa.gov/
tio/download/remed/542f06003.pdf
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the mobility of metals, and reduced soil
toxicity; plant and soil microbial activity
also increased and a plant community was
established. Stakeholders were concerned that
leaving the waste in place would create an
attractive nuisance and be harmful to wildlife
attracted to the newly vegetated area, but the
treatment reduced the potential for ingestion
of contaminants by wildlife by decreasing the
extractable metals in the soil. Assessments
during 2005, 2009, and 2010 indicate that the
vegetation established on the demonstration
areas is robust, reproducing, and permanent
many years after it was first planted.
Revitalization Activities
As a result of the initial research and field
studies, stakeholders who previously
expressed concern about the viability and
protectiveness of in situ treatment and
revegetation of the fluvial deposits became
proponents and recommended approval of
EPA's plans for similar work on the remaining
fluvial deposits and in contaminated irrigated
meadows. In 2008, a remedial action was
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initiated to treat an additional 20 acres of
fluvial deposits plus 160 acres of irrigated
meadows located on private and public lands.
The remedy was based on lessons learned
during the initial field studies and on work at
a similar site, the Clark Fork River NPL site in
Montana.
Lime, organic material, and fertilizer
application rates were identified based on
a statistical evaluation of characteristics at
the site for the irrigated meadows. Typical
agronomic methods, including calibrated
spreaders and agricultural deep till or
industrial discs, were used to apply and mix
soil amendments. A drill seeder was used
to apply a seed mix tailored to landowner
preferences such as grazing and forage
production, and straw mulch was spread to
protect the seed until spring germination.
A hybrid approach was taken to establish the
lime application rate for each fluvial deposit.
In general, one of the following two "master"
application rates was assigned to each deposit,
depending on lime requirement data that
identified current acidity and potential acidity
created by the pyritic soils: (1) 3 percent lime
by weight, and (2) 6 percent lime by weight.
However, a custom lime rate was selected
for deposits with an extremely high lime
requirement. The lime and phosphate fertilizer
was applied to the full depth of tailings and
mixed, and then organic matter was added
and tilled to a depth of 12 inches. Initially, an
excavator was used to blend the amendments
into the fluvial deposits. However, the process
was slow, so the excavator was replaced by an
Allu mixer that is capable of precision work
along uneven boundaries and can manage
large (up to 12-inch) rock. The fluvial deposits
were hand-seeded with a riparian seed mix
approved by the land manager (either the
private landowner or Colorado State Parks),
raked, and mulched before winter arrived.
The streambanks adjacent to the fluvial
deposits were often compromised because of
the absence of vegetation caused by metals
toxicity or low pH. Tilling amendments
California Gulch, Lake County, Colorado Superfund Case Study
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ECOLOGICAL REVITALIZATION OF CONTAMINATED SITES CASE STUDY
into the tailings would
further destabilize the
streambanks and leave
entire treatment areas open
to erosion, so stream bank
stabilization measures
were needed. Stakeholders
expressed concern over
armoring banks with
riprap or gabion baskets
during the demonstration
projects; therefore, in a
few locations, bendway
weirs and root wads were
used protect the bank and
enhance fish habitat. The
remedial action used soft
engineering techniques to
create well-vegetated banks
that protect the remediated
areas in the near term, but
will also accommodate
natural stream migration in
the long term. Streambank
stabilization tools included
the following:
Excavation of
contaminated soil
within 10 feet of
the streambank and
replacement with clean
fill
Rock roll along the toe
of the stream bank
Coir roll (biolog) along
the toe of the stream
bank or behind the rock
roll
Sedge {Carex spp.)
plantings
Mature willow (Salix
spp.) transplants
Tipped willows that
extend into the river
The Carex plantings and
mature willow transplants
Stakeholders Involvement
EPA - EPA Region 8 provided the site characterization,
mapping, alternatives analysis, demonstration project
funding and implementation, feasibility study, risk
assessment, remedial action planning and implementation,
and coordinated with a large group of agency and local
stakeholders over the entire life of the project. EPA
participated in a multi-agency effort that successfully
coordinated Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) and Natural
Resource Damages activities. EPA's Environmental
Response Team (ERT) provided research and development
assistance for the initial field studies, including contracting
with the USDA for research assistance.
Landowners - Community members, especially
landowners in and around the California Gulch OU11
site, were actively engaged in selection, design, and
implementation of the remedy to ensure private and public
lands returned to beneficial use.
Local Government Authorities - Lake County had a
vested interest in the end use of the site and wanted ensure
it met the goals of its master plan. The demonstration
projects were coordinated with a Lake County Open Space
Initiative project that created a fishing lake, river access,
and informative trails.
State and Federal Natural Resource Trustees - EPA and
state and federal natural resource trustees, including the
U.S. Fish and Wildlife Service, the U.S. Bureau of Land
Management, the U.S. Department of Justice, the Colorado
Department of Public Health and Environment, the
Colorado Division of Natural Resources, and the Colorado
Attorney General's Office, coordinated site assessment,
remedy selection, and remedy design to ensure EPA
CERCLA efforts were consistent with long-term restoration
actions. Trustees also provided input to EPA during
remedial design and construction to ensure the remedy
protected, and in some cases enhanced, species habitat.
Colorado State Parks Colorado State Parks worked with
EPA to identify access road and borrow area locations that
fit with long-term land use priorities.
Potentially Responsible Parties (PRPs) - A Consent
Decree settlement with the PRPs provided funding for the
remedial action.
California Gulch, Lake County, Colorado Superfund Case Study
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ECOLOGICAL REVITALIZATION OF CONTAMINATED SITES CASE STUDY
were harvested from the adjacent floodplain.
These tools were used in various combinations
to address the diversity of streambank
conditions encountered.
Performance criteria were developed to
measure the success of the remediation:
Soil criteria include post-treatment
soil characteristics such as pH, lime
requirement, organic carbon, and electrical
conductivity.
Vegetation criteria include seedling
density (first-year measure only), cover,
species richness, biomass, and evidence of
reproduction.
Irrigated meadows criteria were
developed from the results of pre-
remediation sampling in contaminated and
uncontaminated meadows
Fluvial deposits criteria were based on the
characteristics of the demonstration areas
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Incorporating Recreation
into the Remedy
Land use changed during the lifetime of
the project. Historical ranch land was
purchased by a Colorado community for
the water rights and was designated for
recreational use, and another historically
ranched property was purchased by
natural resource trustees to provide critical
habitat. In addition, Lake County's the
High Lonesome Recreation area which
included a fishing lake, river access, and
a trail through demonstration plots with
paths, bridges, and signage describing the
remediation and site ecological features
was developed in the project area. A
portion of the site is also located in the
Arkansas River Headwaters State Park.
Construction roads required during
remediation were located to minimize
impacts to vital bird habitat, and some of
the roads will be used for long-term fishing
access and recreational use.
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Fishing along the revitalized streambank
5 to 7 years after treatment and of riparian
reference areas.
Streambank criteria were based on an
adaptation of the Riparian Evaluation
System (RipES) developed by Reclamation
Research Group for the Clark Fork River
site.
The remediation areas are also monitored for
erosion, bare areas, and weeds.
Lessons Learned
1. Consider all aspects of the remedy in
estimating costs: During the initial
demonstration project, biosolids were
provided at no cost by the Denver Metro
Wastewater Treatment Facility, but the cost
of transportation over steep mountain roads
was not covered. During the remedial
action, the compost supplier was selected
for a low cost and high organic content
product, but the quality of the compost
degraded over time and newer material was
not fully composted, leading to elevated
ammonia and salt content and reduced
vegetation production. A quick response
to changes in materials quality, identified
during a construction quality assurance
and quality control (QA/QC) monitoring
program, saved long-term maintenance
costs and headaches.
2. Equipment tailored to site requirements:
Incorporation of soil amendments into deep
and sometimes rocky fluvial deposits using
California Gulch, Lake County, Colorado Superfund Case Study
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ECOLOGICAL REVITALIZATION OF CONTAMINATED SITES CASE STUDY
traditional construction equipment was
labor-intensive and yielded inconsistent
results. The construction contractor
therefore identified and procured an Allu
mixer that was productive, reliable, and
cost-efficient; provided consistent mixing;
and dealt with rock and mud. The Allu
worked with precision near stream banks
and around existing vegetation and could
handle large (up to 12 inch) rock without
breaking down, leaving very few areas
unamended. Rock segregated during
the Allu mixing process was used for
streambank stabilization.
3. Integrated design: The project drew
from site-specific research performed by
ERT, USDA, Colorado State University
and others, plus technology transfer from
experience at the Clark Fork River site in
Montana, thus providing high confidence
in the outcome of the remedial action. The
early laboratory tests, test plots, and larger-
scale field demonstration projects paved
the way for acceptance of the larger-scale
remedial action, and experience on the
Clark Fork River site provided insight into
effective implementation of the design-
build project.
4. Availability of resources differs
depending on the region: The source of
biosolids in the area "dried up" when a
nearby mine reclamation project acquired
all of the biosolids from nearby mountain
communities, so the remedial action
relied on cow manure compost, a plentiful
resource in the Colorado Front Range. The
sugar beet lime used during remedicition
is a waste product from the sugar beet
industry in eastern Colorado and contained
approximately 20 percent moisture, making
it much easier to spread and less likely to
produce dust than dry lime.
5. Climate can affect the success of
revitalization: Leadville is the one of the
highest elevation incorporated towns in
North America, at 10,200 feet. The growing
season is approximately 60 to 70 days,
inhibiting the growth of new vegetation.
Rainfall is approximately 17 inches, further
limiting growth and allowing capillary
rise of metals salts during dry periods.
Vegetation stress was observed in the
demonstration areas during the early years
after treatment because of drought, so
performance standards for the subsequent
remedial action were developed to
accommodate unusual weather patterns or
other uncontrollable events.
6. Incorporate stakeholder priorities
when possible: Concerns about specific
streambank stabilization techniques were
overcome when stakeholders suggested
slight design modifications that would
improve fish habitat while providing
protection of remediation areas without
increasing costs. Access roads in the
recreation area were more acceptable when
EPA agreed to leave certain roads in place
for long-term recreational paths and river I
access.
7. Work with the entire system: A fluvial
geomorphologic assessment of the
Arkansas River provided valuable
information on the vulnerability of the
specific river reaches, assisting with the
remedial design. The geomorphologic
assessment was valuable to natural
resource trustees and other stakeholders
and will be used in future natural resource
improvement efforts by the State of
Colorado and federal agencies.
Smith Ranch vegetation assessment, 2010
California Gulch, Lake County, Colorado Superfund Case Study
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ECOLOGICAL REVITALIZATION OF CONTAMINATED SITES CASE STUDY
Additional Information
Websites to obtain additional information on the California Gulch site and ecological revitalization include the
following:
EPA Region 8 Superfund Program, California Gulch
http://www.epa.gov/region08/superfund/co/calgulch/
Wildlife Habitat Council Case Study 11, Upper Arkansas River Tailings Restoration
http://www.wildlifehc.org/ewebeditpro/items/O57F3067.pdf
University of Washington Upper Arkansas River Alluvium Remediation, Biosolids Demonstration, Leadville,
Colorado
http://faculty.washington.edu/clh/leadville.html
Cost and Performance Summary Report, In Situ Biosolids and Lime Addition at the California Gulch
Superfund Site, OU11
http://www.brownfieldstsc.org/pdfs/CaliforniaGulchCaseStudy_2-05.pdf
Leadville, Colorado: Moving Beyond the Scars of Mining, Integrating Remedial Design and Site Reuse
http://www.epa.gov/superfund/programs/recycle/pdf/cal_gulch.pdf
EPA's Eco Tools Website
http://www.clu-in.org/ecotools/
Ecological Revitalization: Turning Contaminated Properties into Community Assets
http://www.clu-in.org/download/issues/ecotools/Ecological_Revitalization_Turning_Contaminated_Properties_
into_Community_Assets.pdf
Frequently Asked Questions about Ecological Revitalization of Superfund Sites
http://www.clu-in.org/download/remed/542f06002.pdf
Revegetating Landfills and Waste Containment Areas Fact Sheet
http://www.clu-in.org/download/remed/revegetating_fact_sheet.pdf
Ecological Revitalization and Attractive Nuisance Issues
http://www.epa.gov/tio/download/remed/542f06003.pdf
For additional information on the California Gulch site,
you can also contact these project managers:
Michael Holmes, RPM
(303) 312-6607
holmes.michael@epa.gov
Harry Compton, Environmental Response Team
(732) 321-6751
compton.harry@epa.gov
Michael Zimmerman, On-Scene Coordinator
(303) 312-6828
zimmerman.mike@epa.gov
Jan Christner, PE
URS Operating Services, Inc.
(505) 797-1154
J an_Christner@URSCorp. com
If you have any questions or comments on this fact sheet, please contact:
Michele Mahoney, EPA
mahoney.michele@epa.gov
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California Gulch, Lake County, Colorado Superfund Case Study
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