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/A newsletter about soil, sediment, and groundwater characterization and remediation technologies
Issue 53
This issue o/Technology News and Trends highlights passive treatment systems (PTSs) used
to treat mining influenced water (MIW) at former or current hard rock mines. Each PTS uses a
biochemical reactor (BCR) supported by remediation polishing technologies such as aerobic
wetlands or limestone beds. As passive systems, these technologies rely on natural hydraulic
gradients (and in some cases renewable energy sources) to transfer impacted water from mine
adits and seeps to the ground-surface treatment cells.
Full-Scale PTS Uses Six-Step Process to Treat Polluted Mine Discharge
The U.S Environmental Protection Agency
(EPA), University of Oklahoma, and other
federal, state, local, and tribal partners
collaborated in 2004 to design a PTS on part
of the 40-square-mile Tar Creek Superfund
site in northeast Oklahoma. The PTS treats
artesian groundwater that has discharged
from abandoned underground lead and
zinc mines into a tributary of Tar Creek for
over 30 years. Periodic sampling since
completion of the PTS in December 2008
has shown that the passive treatment train
is effective in removing metals from MIW
and has significantly reduced concen-
trations of metals in the output to the Tar
Creek tributary. The PT Sis the first full-scale
MIW treatment system in the 100-square-
mile Tri-State Mining District, which extends
into Kansas and Missouri.
During active mining, about 50,000 mVday
of groundwater were pumped from under-
ground mines in the area. Mining ceased in
the early 1970s, and by 1979, MIW with
high levels of heavy metals was seeping to
the surface, contaminating surface water.
The PTS was installed at Mayer Ranch, a
private property where sampling of seeps
from two old mining boreholes showed
concentrations as high as 192,000 |lg/L iron,
11,000 jig/L zinc, 970 jig/L nickel, 60 jig/L
lead, and 17 Jlg/L cadmium from 2004 to
2008. The seeps discharged at a rate ranging
from 570 to 950 L/min and had a pH of 5.95.
The PTS was designed to treat a metal-rich
influx of 1,000 L/min and remove a target
20 g/m2/day of iron. The goal was to decrease
receiving stream concentration of iron, zinc,
lead, and cadmium to the Criterion
Continuous Concentrations suggested by
EPA's national recommended water quality
criteria for freshwater aquatic life.
Construction began with the capture and
hydraulic control of seeps through rotosonic
over-drilling and placement of casing over
the two known boreholes. This also allowed
for further quantification of flow rates and
variability. During subsequent construction
activities, a third artesian borehole was
discovered and incorporated into system
design. Stormwater was diverted using
existing channels and burrows excavated by
adjacent landowners for private use.
The completed PTS includes six distinct
process units that include parallel treatment
trains (Figure 1) to allow for maintenance and
estimation of variance in performance. The
system was consolidated into a compact
"footprint" area (about 2 ha) to comply with
construction requirements adjacent to an
existing utility corridor.
The first process unit is an oxidation pond
that receives the artesian MIW and oxidizes
and hydrolyzes the Fe2+. Oxidized iron then
settles out as iron oxyhydroxide solids.
[continued on page 2]
May 2011
Contents
Full-Scale PTS Uses
Six-Step Process to
Treat Polluted Mine
Discharge page 1
EPA Evaluates
Performance of a
Cold-Climate,
High-Elevation PTS page 3
BCR and Wetlands
Treat MIW at Remote
Site in White Mountain
National Forest page 4
Online Resources
EPA offers basic information
about addressing Abandoned
Mine Lands (AML) at
www.epa.gov/superfund/
programs/aml/index.htm.
Reports on research, assess-
ment, and remediation of
mining waste at Superfund
sites are available at
www.epa.gov/superfund/
programs/ami/tech/. More
information soon will be
available on the Clu-ln Web
pages for mining sites at
www.cluin.org/issues/
default.focus/sec/mininq sites/
cat/overview. In addition, the
Interstate Technology and
Regulatory Council (ITRC)
provides information to assist
in the selection of mining
waste treatment technologies
atwww.itrcweb.org/
mininqwaste-quidance/.
Recyc led/Recycl abl e
Printed wilh Soy/Carrola Ink on paper llral
contains at least 50% recycled fiber
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[continued from page 1]
Effluent water flows by gravity feed to the
two parallel surface water wetlands.
Emergent vegetation in the shallow zones
(<0.3 m) increases retention time of solids,
while the deeper pools facilitate settling
of oxidized and hydrolyzed iron solids from
solution. Water then flows to the third
process unit comprising parallel vertical-
flow BCRs designed to provide a reducing
environment to remove cadmium, lead, and
zinc. The BCRs were constructed with a
45-cm layer of organic substrate (a mixture
of 45% spent mushroom compost, 45%
hardwood chips, and 10% manufactured
limestone sand) overlying a 30-cm
limestone gravel drainage layer containing
perforated drainage pipes. A low-
permeability HOPE liner beneath the gravel
maintains design integrity.
In the fourth process unit, submerged
aeration systems in two parallel aeration
ponds re-oxygenate water from the BCRs.
Aeration reduces odors caused by the
emission of hydrogen sulfide gas during
bacterial sulfate reduction. Water in one
pond is aerated by a vertical displacement
pump powered by a 20-foot-tall windmill;
as a result, water is aerated only when the
wind is blowing. Water in the adjacent pond
is aerated bv a high-volume compressor
1 Oxidation Pond
2 Surface Flow Wetlands
3 Vertical Flow BCRs
4 Re-Aeration Ponds
5 Horizontal Flow Limestone Beds
6 Polishing Wetland/Pond
N North
S South
Figure 1. A six-step
passive treatment
system near Mayer
Ranch within the
Tar Creek
Superfund Site is
designed to receive
and treat up to
1,000 liters of flow
per minute from
three artesian mine
water discharges.
wildlife habitat and serve as a buffer
between the PTS and the tributary and its
associated riparian zone.
Water quality entering the tributary has
improved substantially since installing
the PTS. Output of iron has decreased to
440 |J,g/L, while outputs of zinc and nickel
were decreased to 450 |J,g/L and 160 |J,g/L,
respectively. Levels of cadmium, lead, and
arsenic are below detection limits, and pH
has increased from 5.95 to 7.11. The PTS
retains approximately 57,000 kg iron, 3,300
kg zinc, 300 kg nickel, 5 kg cadmium, 17kg
finalized a hydrogeological study that
concluded that reinjection of mining
waste into the mine workings complies
with Underground Injection Control
requirements. Cleanup began in 2010 and
is expected to take 30 years to complete.
Contributed by Robert Nairn, Ph.D.,
University of Oklahoma (nairn(a),ou.edu
or 405-325-3354), and Ursula Lennox,
(lennox.ursula(a)epa.gov or 214-665-
6743) and Gary Baumgarten, EPA
Region 6 (baumgarten.gary&.epa.gov
or 214-665-6749).
Ldd,diidl8k|
. Buiifiuidl
powered by a 120-watt photovoltaic (PV)
system that charges a deep-cycle battery.
The PV system operates the compressor
on a 20-hours-on, 4-hours-off cycle.
Horizontal-flow limestone beds in ponds
of the fifth process unit further improve
water quality by removing additional zinc
and manganese and increasing water
hardness to offset the bioavailability of
any remaining trace metals. The limestone
beds are greater than 1 meter thick to
provide a minimum 14-hour retention time.
The final polishing pond/wetland facilitates
settling of residual solids through
vegetative filtration and re-aerates water
through passive photosynthesis. Water
from the pond discharges via an exit pipe
into a small channel that feeds into the Tar
Creek tributary. The wetlands provide a
vii ai stint/ L»ti
reuse of accumulated solids and
substrates retained by the system is being
explored as researchers continue to study
receiving stream biogeochemistry, fish
and macroinvertebrate communities,
microbial community activity, and degree
of bioaccumulation potential.
Design and construction of the Mayer
RanchPTS cost $1,196,000. The system is
expected to last 25 years, with an estimated
$20,000 annual operation and maintenance
(O&M) cost. Total costs (including
research) are estimated at $4 million.
Other cleanup activities at the Tar Creek
Superfund site include the processing of
chat for resale, remediation of distal
properties, and the reinjection of mining
wastes into mine cavities. EPA recently
Errata
To clarify information in the March
2011 article, "3D-CSIAForensics at
the FAMU Law School Site Reveals
Multiple Contaminant Sources," the
Florida Department of Environmental
Protection's (FDEP) Site Investigation
Section (SIS) conducted the study to
assess groundwater quality and
identify potentially responsible parties.
The owner of one facility at which a
release occurred is responsible for
remediation and is working with the
FDEP District Office to coordinate
cleanup of their release. Upon
completion of the SIS report, FDEP
will determine if additional facilities/
properties will require further assess-
ment and/or remediation activities.
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EPA Evaluates Performance of a Cold-Climate, High-Elevation PIS
EPA Region 8 is monitoring performance
of a PTS consisting of a BCR and an aerobic
polishing cell (APC) at the 10-acre
Standard Mine Superfund site in Gunnison
County, CO. The Engineering Technical
Support Center of EPA's Office of Research
and Development (ORD) worked with
Region 8 to construct the pilot-scale PTS
to evaluate its efficacy during the harsh
winter conditions at the site's high
elevation (11,000 feet above mean sea
level). To date, this is the only known PTS
above 10,000 feet. Performance evaluation
in late 2009 indicated that the BCR was
removing, on average, more than 98% of
the contaminants of concern (COCs)
(cadmium, copper, lead, and zinc) influent
concentrations and 91% of the total iron
influent concentrations. More recent data
analyzed by ORD show that the APC is
increasing dissolved oxygen and reducing
effluent toxicity.
Lead, zinc, silver, and gold were mined at
Standard Mine from the 1870s until 1966
when the mine was abandoned, but remaining
wastes continue to affect the area's surface
water. Prior to PT S installation, outflow from
the mine adit drained into Elk Creek, which is
a tributary of Coal Creek. Together, these
creeks supply municipal drinking water for
the Town of Crested Butte. Highest
measured concentrations of the primary
COCs (for aquatic life) in the adit water are
0.201 mg/L dissolved cadmium, 0.454 mg/L
dissolved copper, 89.815 mg/L total iron,
0.381 mg/L dissolved lead, 13.24 mg/L
dissolved manganese, and 31.9 mg/L
dissolved zinc. The Colorado water quality
standards for discharge to Elk Creek (based
on chronic toxity for a metal hardness value
of 65 mg/L) are 0.31 |lg/L cadmium, 6.2 |lg/L
copper, 1.6 Jlg/L lead, 1,430 Jlg/L
manganese, and 86 |J,g/L zinc.
PTS construction began in 2007 with
installation of the BCR. The BCR consists
of a 5-foot-deep geomembrane-lined cell
filled with 30% (by weight) limestone along
with wood chips, manure, and hay totaling
approximately 5.5 tons of organic material
(Figure 2). This reactive substrate provides
an organic carbon source for microbial
population and promotes biological
reduction of sulfate and removal of metals
as metal sulfide precipitates.
Two PVC pipes carry MIW from the adit to a
5 00-gallon buried tank by way of gravity
feed. During periods of high flow, tank
overflow is diverted to the nearby Elk Creek.
From the storage tank, MIW is pumped
through a flume to the BCR at an average
rate of 1-1.5 gpm. Pump operation is
automated by an electric timer powered by a
90-W PV system equipped with a series of
12-volt, deep-cell, marine-grade batteries.
The BCR became operational in late 2007, and
construction of the APC was completed in
2008. Following an average three-day
residence within the BCR, the effluent
drains via gravity to the APC through use
of a stand-pipe flow splitter housed in a
nearby shed. The APC encompasses a
series of cascading cells with open water
and a limestone rock cell. The APC's
primary role is to reduce manganese,
increase dissolved oxygen, and return
parameters such as total suspended solids,
ammonia, nitrite/nitrate and E. coli to
concentrations below applicable water
quality standards. Treated effluent from the
APC is discharged to a wetlands area that
ultimately drains into Elk Creek.
Results from the first two years of annual
monitoring (2008 and 2009) indicated that
the BCR demonstrated an average metal
removal efficiency of approximately 98%,
for the primary COCs. Iron was removed
by the BCR at an average removal
efficiency of 92% in 2009 and 97% in
2010. Monitoring of the APC effluent
showed manganese concentrations
ranging from 4.78 mg/L to 10.01 mg/L in
2009, and limited sampling in 2010 showed
concentrations of 0.05-3.04 mg/L.
Due to harsh winter conditions, the site is
accessible for routine sampling and O&M
activities from only July to October of each
year. As a result, several sampling
procedures have been used. During the
winter and spring, samples from the BCR
influent and effluent were initially
collected by autosamplers, and grab
samples were collected during routine
monthly maintenance visits. Currently,
sonde units are used to remotely measure
water quality parameters such as pH,
temperature, and oxidation-reduction
potential on a continuous basis. The
sonde data are stored in an onsite data
logger and transmitted by satellite to end
users in Denver, allowing real-time access
to the field information. All power for the
monitoring system is provided by the
onsite PV system.
The constant presence of flowing water
prevents freezing and allows the system
to operate year-round. In early 2009, PTS
operations were suspended intermittently
[continued on page 4]
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[continued from page 3]
over about 15 weeks due to pump failure.
infiltration gallery clogging, and delivery
pipe clogging. Failure of the pump timer
was attributed to hydrogen sulfide
buildup that corroded wires. This problem
was rectified by replacing the pump wires
and enclosing all PTS wiring in metal
conduits to minimize exposure to sulfide
gas. Other maintenance included replacing
the original submersible pump, which
appeared to fail prior to its expected 400-
hour life due to metal precipitation and
corrosion. Trial use of an alternate,
diaphragm-style pump was unsuccessful
after one month as a result of freezing and
led to installation of a third, more robust
submersible pump in late 2009.
Upgrades to the piping system that carries
water between the mine adit and storage
tank also were implemented. High spring
flow conditions were found to cause a
backup that released adit discharge on the
ground surface across the site. The
original pair of 2-inch-diameter P VC pipes
was consequently replaced by a pair of 4-
inch lines buried in 2-4 feet of pea gravel,
but the piping remains vulnerable to
sediment clogging and iron hydroxide
precipitation.
Conditions such as pH in the mine adit
remain steady. Based on parameters such
as influent and effluent concentrations of
sulfate, sulfide, and calcium, as well as
biochemical oxygen demand, the BCR
continues to operate successfully. Overall
results suggest the PTS can effectively
reduce the COCs (except manganese) under
harsh winter conditions and high elevations.
The PTS is not meeting in-stream standards,
but the pilot-scale BCR is treating only a
fraction of the water coming from the mine.
Based on the estimated dissolution rate of
limestone and an assumed 90% operation
rate, a sufficient volume of limestone is
expected to remain in the BCR for four years.
Factors undergoing evaluation include
COC concentration reductions,
demonstrated life of the pump and remote
monitoring system, and effectiveness of
the corrosion corrective actions and
changes to the influent lines to reduce
plugging. Performance evaluation includes
collection of PTS influent and effluent flow
and water quality data during high-flow,
low-pH spring runoff conditions.
The cost of design, construction, and
materials for the pilot-scale PTS totaled
approximately $175,000, including $50,000
for excavation and earth-moving, $10,000
for sampling equipment, and $12,000 for
the PV and satellite equipment. EPA
Region 8 will use the pilot-scale results
to evaluate potential construction of a
full-scale PTS. The capital cost for a full-
scale PTS expected to operate over 30
years (at a flow rate of 20 gpm) is
estimated at $750,000, with an estimated
$25,000 annual O&M cost.
ORE) continues to work with EPAregions
to build PTSs at other mining sites.
Components of other PTSs may include
a chitin reactor, which was originally
constructed as an alternate remediation
polishing component of the Standard
Mine PTS but suspended after two
months of operation due to apparent
construction failure.
Contributed by Christina Progess, EPA
Region 8 (progess. christina(q),epa. gov
or 303-312-6009) and David Reisman,
NRMRL (reism an. david(a),epa. gov or
513-569-7588).
BCR and Wetlands Treat MIW at Remote Site in White Mountain National Forest
The U.S. Department of Agriculture
(USDA) Forest Service and the Plymouth
State University Center for the
Environment (PSU) are monitoring
performance of a full-scale PTS that began
operating in 2009 as part of removal actions
at the abandoned Ore Hill Mine site near
Warren, NH. The system encompasses a
BCR and adjoining wetlands constructed
after discovery of an MIW seep, which
continued to cause elevated metal
concentrations in surface water despite
earlier cleanup efforts. As of late 2010, the
PTS was reducing metal concentrations in
the MIW by more than 90%.
A one-mile undeveloped road provides
access to this remote 10-acre site. From
December through April each year, a quarter
of the stretch requires use of snowshoes. The
site was mined intermittently for lead, copper,
and zinc from the 1830s until approximately
1915 when the mine was abandoned. The
property eventually became part of U.S.
forestland, but mining left behind piles of
waste rock and tailings, and surface water
drainage from the site exhibited high levels
of dissolved metals and low pH.
The drainage impacted downstream water
quality and aquatic life in Ore Hill Brook;
approximately five miles of the stream
were added to the state's 303(d) list of
impaired waters in the Baker River
watershed. In addition, a portion of the
Appalachian National Scenic Trail that
passed through the site was re-routed in 1979
to a nearby corridor, due to the waste piles.
The highest measured concentrations
of COCs in onsite MIW prior to removal
actionswere 14.25 mg/L aluminum, 1.42mg/L
copper, 1.85 mg/L lead, and 46.25 mg/L
zinc, with a pH as low as 3.46. These
concentrations exceeded state water
quality criteria for protection of aquatic
life by 2.5 to 3.3 orders of magnitude.
In the 1980s, initial cleanup was conducted
through limestone capping of 4.5 acres of
consolidated waste piles, revegetating
soil-capped areas, and lining selected
surface water channels with limestone.
Continued downstream contamination
and MIW seeps through the soil caps led
to a 2006 removal action focused on
controlling the contaminant source and
[continued on page 5]
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[continued from page 4]
reducing offsite migration of hazardous
metals in surface water. The goal was to
meet state surface water quality criteria for
pH and metals.
The removal action involved excavating
approximately 35,000 yd3 of mine tailings
and waste rock with high hazardous metal
content, mixing it with a phosphate-based
amendment to reduce metal availability,
and transferring the treated material to an
onsite, unlined, soil-capped repository.
Phosphate was selected after a treatability
study found it was as effective as Portland
cement in reducing metals content in the
leachate from tailings, and the resulting
repository would not require the lining
and capping design typical of a Portland-
cement repository. Post-construction
monitoring of downstream surface water
found that metal concentrations were
80% lower, but did not reach the expected
90-95% metal reduction.
During the 2006 excavation, a previously
undiscovered adit was encountered. Seep
from the adit flowed at a rate of 1 gpm
across 200 feet of bedrock into a shallow
pond within a former quarry pit (covering
approximately 50 by 100 feet and extending
15 bgs) before continuing downgradient.
As an interim effort to slow surface water
movement and control erosion, 13
sediment check dams were installed
within the tailings excavation area.
In 2008, the Forest Service constructed and
monitored performance of a pilot-scale,
temporary BCR to evaluate its design and
efficacy in addressing the newly discovered
adit seep. The pilot-scale results and findings
from a PSU study on surface water within
the 2006 excavation area were used the
following year to construct a full-scale BCR
along with an aerobic wetlands area as part
of a second removal action. Full-scale BCR
construction involved excavating sediment
from the existing pit/pond and lining it with
900 yd2 of geosynthetic clay. The BCR base
was plumbed with a 720-foot network of 4-
inch-diameter piping and equipment to
control inflow of MIW diverted from the adit
and outflow to the constructed wetlands. A
shallow overflow channel was constructed
along the BCR perimeter to manage high
flow during stormwater events.
A total of approximately 130 tons of
reactive substrate containing (by weight)
2.5% manure, 47.5% wood chips, 10%
hay, and 40% limestone were placed in
the approximate 90- by 40-foot BCR
(Figure 3). The wood chips and hay were
obtained from local producers and mixed
at a nearby dairy farm providing the
manure. The reactive substrate was
hauled in batches three miles to the site.
Following final placement of the
substrate, the BCR remained closed at
its base for approximately 30 days to
provide an incubation period and
increase growth of microbial populations
in the substrate.
The wetland was constructed approx-
imately 100 feet downgradient of the
BCR. Due to the ground slope and the
need for shallow wetlands, the design
called for two constructed wetland cells
operating in series and covering a total
of about 5,600 ft2 (Figure 4). In July 2009,
two thousand plugs of various native
species were planted in the wetlands by
high school students participating in a
Forest Service training program.
MIW began flowing through the complete
PTS in September 2009. Upon exiting the
PTS, the treated water flows along an
existing surface water channel and enters
Ore Hill Brook approximately 300 feet
downgradient.
[continued on page 6]
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Solid Waste and
Emergency Response
(5203P)
EPA 542-N-11-002
May 2011
Issue No. 53
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242
Presorted Standard
Postage and Fees Paid
EPA "
Permit No. G-35
Official Business
Penalty for Private Use $300
[continued from page 5]
Since start-up, the rate of MIW flow
through the BCR has been estimated at
approximately 2-5 gpm. Five quarterly
sampling events have been conducted to
measure metal concentrations and water
quality parameters in the BCR influent and
effluent as well as the wetlands effluent.
Limited sampling results to date indicate
the PTS is performing as expected, with
cadmium, copper, and zinc concentrations
in the BCR effluent decreasing 93%, 90%,
and 93%, respectively. A lower (65%)
reduction for lead may be due to
significant variation in its influent
concentrations, which ranged from 0.0156
to 0.6956 mg/L over the five sampling
events. Additional removal of cadmium,
copper, lead, and zinc appears to be
occurring in the wetlands. Due to inflow
below the BCR, the PTS has not quite met
the overall long-term water quality criteria;
however, surface water quality is
significantly improved.
O&M has included quarterly site
inspections and water quality measurements.
The monitoring is conducted through a
Forest Service cooperative agreement
initiated in 2006 with the PSU Center for
the Environment. The Forest Service
anticipates continued PTS monitoring
and work with the New Hampshire
Department of Environmental Services to
evaluate performance of the BCR and
overall PTS in reaching state water
quality criteria.
Construction costs for the full-scale PTS
totaled approximately $ 175,000. The BCR
is expected to operate effectively for 18
years, at which time its substrate is
expected to require replacement.
Contributed by Tim Buxton, USDA
Forest Service (tbuxton(a)fs.fed. us or
603-466-2713) and Aaron Johnson,
PSU Center for the Environment
(ajohns 17(a)plymouth. edu or 603-535-
3269).
Contact Us
Technology News and Trends
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Suggestions for articles may
be submitted to:
JohnQuander
Office of Superfund Remediation
and Technology Innovation
U.S. Environmental Protection Agency
Phone:703-603-7198
quander.iohn@.epa.qov
Engineering Issue
More information about managing
and treating MIW at sites such as
these is detailed in the EPA
National Risk Management
Research Laboratory's Management
and Treatment of Water from
Hard Rock Mines engineering
issue (EPA/625/R-06/014) available
at: www.epa.gov/nrmrl/pubs/
625r06014/625r06014.pdf.
EPA is publishing this newsletter as a means of disseminating useful information regarding innovative and alternative characterization and treatment
techniques or technologies. The Agency does not endorse specific technology vendors.
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