EPA Abandoned Mine Lands Innovative Technology Case Study,
Copper Basin Mining District
Constructed Wetlands on McPherson Branch
ABSTRACT:
The Copper Basin Mining District is the former site of
extensive copper and sulfur mining operations dating
back for more than 150 years. In 1998, Glenn Springs
Holdings, Inc. (GSHi) began installing a two-acre
demonstration passive wetland system in conjunction
with limestone dissolution and bacteria sulfate
treatment. The anaerobic cell was completed in 1998,
with two additional aerobic cells completed in 2003.
The demonstration wetland system captured base flow
water from McPherson Branch (a first-order watershed)
with average influent flows of 291 gallons per minute
(gpm). The McPherson Branch flow concentrations of
iron, copper, zinc, and aluminum were reduced by an
order of magnitude and acidity was reduced by 100
percent a fter flowing through the demonstrative wetland.
The alkalinity was increased from 0 milligrams per liter
(mg/L) to an average of approximately 160 mg/L. The
pH of the treated water increased from 3.82 to 6.50.
Flow capacity is limited, with treatment of only the base
flow of the McPherson Branch through the wetland-
higher flows bypass the passive treatment system. While
diverting the base flow and improving water quality, GSHI
completed construction of a 65-meter "restored stream
segment" in 2003 to improve habitat and aquatic life of
McPherson Branch (Faulkner, Ben B., and Miller, Franklin
K.. 2003).
Site Background
Copper Basin Mining District Site
CERCLIS ID: TN0001890839
An area rich in mining history, the Copper Basin
Mining District is located in Polk County in
southeastern Tennessee and in Fannin County in
northern Georgia near the North Carolina border
(see Figures 1 and 2). Mining of copper and sulfur
began at the Copper Basin site soon after copper
was discovered in 1843 in Ducktown, Tennessee.
The only deep shaft mines east of the Mississippi
River, mining and processing of copper occurred at
the site until 1987, with sulfuric acid production
continuing until 2000. During the more than 150
years of mining and processing activities
conducted at Copper Basin, a total of more than
95 million tons of ore were mined from nine ore
bodies (U.S. EPA, 2005).
October 2006
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Copper Basin Mine Technology Case Study
Constructed Passive Wetlands System at McPherson Branch
As a result of mining activities, degradation of the site
and surrounding area was so catastrophic that the
Copper Basin was once considered the largest man-
made biological desert in the nation. The activities of
the site impacted an area of more than 35 square
miles, including the Davis Mill Creek Watershed, the
North Potato Creek Watershed, and sections of the
Ocoee River (U.S. EPA, 2006).
Under legal agreements dating from 1990, various
government agencies and private parties have taken
steps to stabilize and partially revegetate the area. The
site is currently being investigated and cleaned up
through a collaborative three-party effort that was
formalized on January 11, 2001 in a Memorandum of
Understanding (MOU) and several related legal agreements among EPA, the Tennessee Department
of Environment and Conservation (TDEC), and OXY USA (a subsidiary of Occidental Petroleum
Corporation). The MOU provides an overall framework and establishes roles and responsibilities
among the three parties for the investigation and cleanup work. Further, it provides assurance that
the part of the federal government will not to list or propose to list the site on the NPL, as long as terms
of the MOU are met. The enforceable agreements add details about the legally binding
commitments made between OXY USA and the government. Glenn Springs Holdings, Inc. (GSHI),
also a subsidiary of Occidental Petroleum Corporation, is conducting the remedial work at the site.
In 1998, GSHI completed an anaerobic cell
of the demonstration wetland on the
McPherson Branch. As of 2003, GSHI
completed two additional aerobic cells of
the wetland, and restored 65 meters of
habitat downstream of the wetland
treatment system. The aerobic cells were
added to aid in the reduction of
manganese and aluminum
concentrations. Today, the company
continues to monitor the site and is
proposing additional remedy activities to
EPA, including additional wetlands and the
use of compost as a sulfate-reducing
bioreactor. GSHI is also in the process of
refining the wetlands technology through
bench-scale testing. However, there are
additional sources of contamination at the
site that are being addressed through
separate remedies, such as removal of
contaminated sediments and capping of
upstream source materials (GSHI, 2003).
(Source: U.S. EPA, 2005.)
Lower
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Figure 2: Overview of Watersheds within Copper Basin
(Source: Faulkner, Ben B., and Miller, Franklin K., 2003.)
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Copper Basin Mine Technology Case Study
Constructed Passive Wetlands System at McPherson Branch
Waste Characteristics
Prior to the Civil War, open roasting was used to remove impurities from copper ore. This practice
resulted in a denuded landscape as timber was cut for fuel for the roasting process. The open
roasting process also produced sulfuric acid, which rained down on a 35-square-mile area. Soil
conservation and reclamation practices, dramatically diminished the Copper Basin sediment load,
but acid rock and mine drainage continue to pollute streams with acidity and high concentrations of
iron, copper, manganese, aluminum, and zinc. The McPherson Branch is a first order tributary to
North Potato Creek. It is typical of the tributaries of North Potato Creek and Davis Mill Creek of the
Ocoee River, which drains the Copper Basin (U.S. EPA, 2005). The 410-acre McPherson Branch
watershed contained mine wastes throughout the transportation corridors. Severe erosion and
sediment deposition in the stream presented a challenge to any remediation technology or recovery
of the stream. Prior to treatment, the McPherson Branch exhibited an average flow of 300 gallons per
minute (gpm) and a pH of 4.0. The total iron, manganese, copper, zinc, and aluminum
concentrations were 7.0, 1.2, 0.6, 1.7, and 4.2 milligrams per liter (mg/L), respectively (Faulkner, Ben B.,
and Miller, Franklin K., 2003).
Treatment Technology
Background
In 1998, GSHI started and completed the construction of the anaerobic cell of the demonstration
wetland on the McPherson Branch near its convergence with Burra Burra Creek within the North
Potato Creek Watershed (see Figures 3 and 4 for plan views of the wetland). The two-acre wetland
was built at a former ore roast yard that contained acid drainage forming material within a highly
eroded watershed. The high sediment load in McPherson Branch necessitated a unique design
feature upstream of the constructed anaerobic wetland, including:
1. A liner (Fabriform blanket, see Figure 5) installed on the west bank 70 meters (m) upstream of
the constructed dam. The liner minimizes infiltration into and drainage from mined waste rock
under the roadway parallel to McPherson Branch;
2. A concrete diversion dam on the McPherson Branch to divert controlled flow to the wetland,
and provide a settlement basin to remove silt from McPherson Branch before it entered the
wetland (see Figure 5);
3. A sluice gate at the concrete dam to release the collected silt; and
4. A flushable sediment trap encased within the dam in the inlet to the wetland.
This design is intended to limit storm water flow into the wetland, limiting sediment and solids that
would compromise the porous limestone bed and the wetland substrate. The wetland is lined with a
Geosynthetic Clay Liner (GCL) covered with a 0.7 m thick agricultural lime-enriched soil layer; 0.7 m
thick layer of crushed 2.5 cm limestone (minimum 75% CaC03 content); hay bales; and 0.15 m of
spent mushroom compost. The wetland design also includes cattails and soil transplanted from a
nearby borrow area with similar quality acidic drainage. Preferred flow is subsurface through the
anoxic limestone bed. Concrete jersey barriers direct surface flow in a serpentine path through the
cattails where it can drain into the limestone bed and be collected by a pipe manifold in the
downstream section of the wetland. (Faulkner, Ben B., and Miller, Franklin K., 2003).
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Copper Basin Mine Technology Case Study
Constructed Passive Wetlands System at McPherson Branch
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Figure 3. Wetland Basin Design
(Source: Marshall, Miller & Associates, 1998}
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Copper Basin Mine Technology Case Study
Constructed Passive Wetlands System at McPherson Branch
Other Technologies Used for Wastestream
Key Dates
The North Potato Creek Watershed was used
for many mining operations at Copper Basin,
such as roasting, smelting, and acid
production. Wastes containing strongly acidic
material adjacent to and potentially
impacting North Potato Creek, are currently
being removed. GSHI is proposing to isolate
this material from surface runoff and limit its
exposure through diversions and capping. To
prepare for construction of a new passive
treatment wetland systems, GSHI is
conducting phased bench-scale testing of
various organic mixtures with strongly acidic
mine drainage. Results of these bench-scale
tests will provide information to help build
effective compact passive systems for the
treatment of small-flow, high-acidity seeps
anticipated after effective land reclamation
is accomplished.
Cost
In 1998, the cost of the anaerobic wetland
and waste removal peaked at approximately
$1 million.
In 2003, the cost of the aerobic wetland, rock
filter, and restored stream segment was closer
to $300,000. However, much more was spent on related waste removal at the site. The purpose of
this wetland is to establish a better understanding of the longevity of passive systems. This passive
wetland treatment system was constructed with a theoretical 20-year design life.
1847
Mining operations begin at Copper Basin.
1987
Copper mining operations cease on July 31. Sulfur
replaces ore as raw material for acid production.
1995
Environmental study begins to identify problems
caused by mining and smelting operations.
1998
GSHI constructs the anaerobic cell for the
demonstration wetland on McPherson Branch
near its convergence with North Potato Creek.
2000
Sulfur processing and mining operations cease.
2001
GSHI enters into a Memorandum of Understanding
along with several enforceable agreements with
EPA and TDEC on January 11 to clean up the
North Potato Creek Watershed and Davis Mill
Creek Watershed.
2003
GSHI completes two aerobic cells for the wetland,
and restoration of habitat on McPherson Branch
downstream of the demonstration wetland. Long-
term monitoring of wetland and restored stream
segment habitat begins.
2006
Proposal from GSHI submitted to EPA and TDEC for
additional wetlands and compost bioreactor on
other Copper Basin wastestreams (GSHI, 2003).
Lessons Learned and Conclusions
GSHI anticipated that simply removing obvious waste materials from the site would not be sufficient
to allow timely restoration of aquatic life in the severely damaged receiving stream. GSHI successfully
demonstrated that passive systems are a beneficial component to land reclamation in this small,
isolated watershed under the right conditions. The constructed wetlands system at McPherson
Branch is a model for remedies being developed and used at the rest of the Copper Basin site. Lightly
buffered streams with natural acidity receiving drainage from highly erodable acid soils and
unusually high precipitation presented unique challenges for reclamation, revegetation, and
mitigation of water quality. Integrating the wetlands atop of the lined, acid-producing material
outside the flood plain, which treats mild acid drainage from sources further upstream, is an effective
method of acid prevention and treatment.
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Copper Basin Mine Technology Case Study
Constructed Passive Wetlands System at McPherson Branch
In anticipation of a high-sediment load from the poorly degraded and vegetated watershed, the
demonstration wetland was intentionally placed outside of the flood plain. The sediment trap and
pinch valve placed at the concrete diversion dam in McPherson Branch controls the amount of flow
into the system by allowing only the base flow and a moderate volume of storm water to enter.
The demonstration wetland at McPherson Branch typically treats high flows of moderate pH and low
metal concentrations. As remediation continues in the North Potato Creek Watershed, GSHI is
proposing to EPA and TDEC to hydraulically isolate contaminated material that cannot be removed,
using a passive treatment system that treats low flows of concentrated acid mine drainage.
EPA Contacts
Loften Carr
Remedial Project Manager
U.S. Environmental Protection Agency
Region IV
Phone: 404-562-8804
E-mail: Carr.Loften@epa.aov
Craig Zeller
Remedial Project Manager
U.S. Environmental Protection Agency
Region IV
Phone: 404-562-8867
E-mail: Zeller.Craia@epa.aov
References
Glenn Springs Holdings, Incorporated. 2003. "Copper Basin Project." URL: http://www.alennsprinas-
copperbasinproiect.com/.
Glenn Springs Holdings, Incorporated. 2003. "Copper Basin Project." History. URL:
http://www.alennsprinas-copperbasinproiect.com/historv.htm.
Glenn Springs Holdings, Incorporated. 2003. "Copper Basin Project." McPherson Branch Demonstration
Site. URL: http://www.alennsprinas-copperbasinproiect.com/mcPhersonSite.htm.
Faulkner, Ben B„ and Miller, Franklin K. 2003. "Improvement of Water Quality by Land Reclamation and
Passive Systems at an Eastern U.S. Copper Mine." Paper Presented at West Virginia surface Mine Drainage
Task Force Symposium, Morgantown, WV. April 16, 2003. URL:
http://www.wvmdtaskforce.com/proceedinas/03/Faulkner.pdf.
Marshall, Miller, and Associates. February 1998. "Details of Copperhill Wetland Project, Ducktown, TN."
U.S. Environmental Protection Agency. July 1, 2002. "Title 40—Protection of Environment, Chapter I, Part
143." Pg. 614. URL:
http://a257.q.akaimaitech.net/7/257/2422/14imar20010800/edocket.access.qpo.qov/cfr 2002/iulatr/pdf/4
0cfr143-3.pdf
U.S. Environmental Protection Agency. July 2005. "Copper Basin Mining District Case Study - Use of
Copperative Agreements." URL: http://www.epa.aov/superfund/proarams/aml/tech/copperbasin.pdf
U.S. Environmental Protection Agency. Region IV. Land Cleanup and Wastes. "Copper Basin Mining
District." http://www.epa.aov/reaion4/waste/copper/ (Accessed 17 April 2006).
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