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/A newsletter about soil, sediment, and groundwater characterization and remediation technologies
Issue 58
of Technology News and Trends highlights projects involving optimization
reviews undertaken by the U.S. Environmental Protection Agency (EPA) and partnering
state agencies or site owners. Each project involved an optimization review performed by an
independent organization and funded by EPA 's Office of Superfund Remediation and
Technology Innovation. The highlighted projects illustrate how optimization can be used to
modify specific components of a treatment process or monitoring program in order to
improve remedy effectiveness, reduce remedy implementation costs, and increase technical
efficiencies. The highlighted projects focus on sites with operating remedies; however, EPA is
now applying optimization to all phases of remediation, from remedial investigation to site
completion. For more information, including results of optimization reviews for nearly 100 sites,
visit the Remediation Optimization focus area of CL U-IN at:www. clu-in. org/'optimization/.
Process Modifications to Improve Treatment of Acid Mine Drainage
April 2012
The Colorado Department of Public Health
and Environment (CDPHE) and EPA's
Region 8 office are conducting remedial
actions at the 400-square-mile watershed
comprising the Central City/Clear Creek
Superfund site. The Argo Tunnel Water
Treatment Plant (Argo WTP), located in
Idaho Springs, CO, is one component of this
work. The Argo WTP treats acid mine drainage
(AMD) discharging from two former mining
tunnels as well as acidic, metals-laden
groundwater from a nearby canyon.
Engineering studies, field tests, and an
optimization review were conducted in recent
years to improve the plant's effectiveness
and efficiency in treating the AMD.
The watershed receives drainage from
areas of the Colorado Mineral Belt, which
crosses several mining districts in Clear
Creek and Gilpin Counties. Water entering
the Argo WTP averages a pH of 2.8 and
contains high concentrations of heavy
metals, including approximately 140,000
micrograms per liter (u.g/L) iron, 95,000
u,g/L manganese, 50,000 \igfL zinc, 20,000
u,g/L aluminum, and 5,000 u,g/L copper.
Water flows from the 4.16-mile Argo
Tunnel, which supplies the majority of
plant influent, at an average rate of 200-
450 gallons per minute (gpm).
The plant began operating in 1998 with a
treatment system that adjusts pH and
removes metals through chemical
precipitation. The fully treated water is
discharged directly to Clear Creek, a tributary
of the South Platte River. Design of the
treatment process anticipated production of
an underflow sludge containing 7% solids
and dewatered filtercake containing 45%
solids. Actual performance of the plant,
however, has produced sludge with 3-4%
solids and filtercake with 17-20% solids,
resulting in significantly more filtercake
needing disposal and increased labor costs.
Each month, a total of approximately 385
cubic yards of filter cake is shipped via 24
18-cubic-yard roll-off containers to a
municipal landfill for disposal. Filter cake
disposal averages $150,000 per year, or
about 15% of annual operating costs.
A 1999 engineering evaluation attributed the
difference in design versus actual sludge and
filtercake properties to the absence of a "true"
high-density sludge (HDS) process. The
Argo WTP process produces underflow
solids that are recycled from the bottom
of the clarifier back to the reactor
(flocculation) tank. In a true HDS process,
underflow solids are recycled from the
[continued on page 2]
Contents
Process Modifications
to Improve Treatment
of Acid Mine Drainage page 1
Combined Remedy
Optimization at
Superfund Site Saves
Over $400,000
Annually page 3
DNAPL Discovery
Affects Groundwater
Treatment and
Anticipated Site
Reuse page 4
TNT Going Paperless!
As part of the federal
government's efforts to "go
paperless," this publication has
graduated to an e-newsletter
available through e-mail
subscription or by accessing
CLU-IN's online archives.
Bimonthly issues will now
provide additional project tools,
supplemental electronic links,
and multimedia illustrations
while continuing to feature
detailed information about 3
or 4 site-specific projects.
This April issue is the final
printed issue; readers who
have not yet converted from
printed to e-mail subscriptions
can do so online by visiting
www.clu-in.org/newsletters,
scrolling down to the list of
"E-mail Newsletters" options,
clicking on "Technology News
and Trends," and entering their
e-mail address.
Recycled/Recyclable
Printed with Spy^anola Ink 01 paper ll
contains at least 50% recycled fiber
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[continued from page 1]
bottom of the clarifier back to a sludge-
conditioning tank (Figure 1) where the
recycled solids mix with lime slurry. The
mixture is then added to the influent to
adjust pH. Conversion of the plant to an
HDS process was estimated to cost
$800,000 in 1999.
In anticipation of transferring project
ownership and operation and maintenance
(O&M) costs from EPA to CDPHE, an
optimization review was conducted in
2007. Results of the review suggested
modifying the reactor tank to increase
solids recycling in a quasi-HDS manner,
at an estimated cost of $75,000. The
review also recommended adding
aeration to the process, at an estimated
cost of $60,000, in order to reduce the
treatment pH. Most significant in terms
of operating expenses, the review
recommended installing new filter
presses that would cost approximately
$560,000. Additional recommendations
involved improvements to the sand filter
and the lime delivery system.
CDPHE proposed implementing a "true"
HDS system rather than modifying the
existing reactor tank with the intent of
improving solids density and reducing
chemical usage. While not specifically
recommended by the optimization
review, this approach is consistent with
the intent of reducing ongoing costs related
to sludge disposal, chemical usage, labor,
and filter scaling. Of the funding provided
by EPA through the optimization
review process, $1,065,000 (including
$695,000 for capital improvements to
the solids handling system) directly apply
to the alternate approach that was
subsequently chosen.
Figure 1. The HDS process is a
modification of conventional lime
precipitation designed to densify the
sludge, reduce the volume of sludge
requiring management, and improve
sludge dewatering.
Design of the new treatment process is
nearly complete. Elements of the HDS
process are based on the results of onsite
pilot testing conducted over four weeks
in November-December 2009. The tests
focused on comparing two treatment
trains that used different sludge solids
recycle ratios. Because the plant influent
contains a high amount of dissolved ferric
iron, two small-scale reactors were used.
The target pH level for precipitating
ferric iron was 4.0, while the remaining
metals were expected to precipitate at a
pH of 9.0-9.5.
Test results indicated improved treatment
of the process influent, with dissolved metal
concentrations below target levels for iron
(<15,800 ng/L), zinc (<225 \igfL), and
copper (<17 |J,g/L). Dissolved cadmium
was non-detectable at a reporting limit of
5 |J,g/L and both dissolved and total
recoverable lead concentrations were non-
detectable at a reporting limit of 5 [ig/L.
Total recoverable metal concentrations of
cadmium, zinc, and copper remained above
target limits but are expected to reach
effluent goals under full-scale conditions
that include a properly sized clarifier for
settling andpost-clarificationfiltration Mixed
results were achieved for manganese, the
most challenging metal under this
treatment process. Dissolved and total
recoverable concentrations for
manganese also would be expected to
reach target levels through a full-scale
system with more efficient aeration that
results in better oxidation.
The process conversion will require new
sludge-conditioning tanks, aeration
blowers, sludge pumping systems and
piping, and electrical supply and controls.
The clarifier tanks currently in use will be
converted to HDS reactors. Most
significantly, a new 50-foot-diameter
clarifier/thickener will be constructed
outside of the primary treatment building.
Since the plant uses a dual treatment train,
one train can be converted while the other
continues to operate and plant shutdown
will be unnecessary.
Full-scale HDS application is expected to
result in an 89% reduction in wet sludge
volume per unit mass of dry solids. The
process also is expected to reduce the
volume of dewatered sludge by
approximately 75% and reduce the
dewatering time by approximately 95%.
These reductions will lead to lower costs
for labor, power, and transportation and
disposal associated with sludge wasting,
dewatering, and management.
CDPHE anticipates construction to begin in
summer2012. Thecosttopilottestanddesign
the process modification totals approximately
$550,000, and construction costs for the
modified system are estimated at $2,500,000.
Annual O&M costs are expected to
decrease by approximately $200,000.
Contributed by Mary Boardman,
CDPHE, (mary. boardman&state. co. us
or 303-692-3413) and Mike Holmes,
EPA Region 8 (holmes.michael(q)epa.gov
or 303-312-6607)
Lime lnfluent
(acid mine drainage)
Air
Flocculant
Effluent
Sludge Recycle
Waste
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Combined Remedy Optimization at Super!und Site Saves Over $400,000 Annually
EPA Region 9's Superfund Office is
optimizing the remediation technologies
used to clean up soil and groundwater at
the Pemaco Superfund site in Maywood.
CA. Due to significant contaminant
reductions since treatment began in 2007.
an optimization review was conducted in
January 2011 to identify opportunities for
modifying orpotentially downsizing certain
components of the remedy. The
recommended optimization approach has
led to a decrease in the pumping rate and
associated energy consumption of the
pump and treat (P&T) and soil vapor
extraction (SVE) systems, focused vapor
recovery, reduced sampling efforts across
the site, and significantly decreased annual
O&M costs.
A chemical blending and distributionfacility
operated at this 1.4-acre site from the late
1940s until June 1991. A wide variety of
chemicals, including aromatic and
chlorinated solvents, flammable liquids.
specialty chemicals, and oils, were stored in
a combination of aboveground storage
tanks, underground storage tanks, and
drums. During the initial site assessment in
1997, EPAfound 56 contaminants in surface
and near-surface soil (0 to 3 feet bgs), the
upper vadose zone soil and perched
groundwater (3 to 35 feet bgs), the lower
vadose zone soil (35 to 65 feet bgs), and the
saturated zone (65 to 175 feet bgs). ffigh
levels of volatile organic compounds (VOCs).
as well as metals and semivolatile organic
compounds were detected. The largest
contaminant plume in the saturated zone
consisted primarily of trichlorethene (TCE)
and its degradation products and was about
1,300 feet long by 750 feet wide.
The 2005 record of decision (ROD) selected
a combined remedy to treat each of the three
contaminated zones. Soil capping and limited
hot spot removal were chosen for surface
and near-surface soil, high-vacuum dual-
phase extraction (HVDPE) was chosen for
upper vadose zone soil and perched
groundwater, while electrical resistance
heating (ERR) with SVE, as well as vacuum-
enhanced groundwater extraction, P&T, and
monitored natural attenuation were chosen
for areas of highest contamination in lower
vadose zone soil and the saturated zone. An
onsite treatment plant was constructed to
treat extracted soil vapors and groundwater
with granular activated carbon (GAC). A
flameless thermal oxidizer (FTO) was also
used to treat vapors when the thermal
treatment system was operational. The
combined remedy began operating by 2007.
The ERH was activated in the source area
for 200 days. The FTO was turned off during
the summer of 2008, but the additional
components of the remedy still operate.
Significant decreases in VOCs, such as TCE.
have been observed since implementation of
the remedy. Plume migration resulted in
concentration increases of some
contaminants in the deeper zones of the
aquifer (Table 1) but are addressed in the
optimization strategy.
Significant decreases in target contaminant
concentrations in the perched and upper
saturated zones of groundwater across the
site offered an opportunity to modify
remedial processes. Between July and
November 2011, a series of steps were
taken to optimize remedy efficiency.
largely focusing on monitoring reduction
due to decreased contaminant
concentrations across the site. More than
half (226 of 432) of the annual samples
collected were eliminated from the
monitoring program by reducing the
number of monitoring wells and the
frequency of sampling. Sampling was
discontinued in wells where contaminant
concentrations remained below the site-
specific remediation levels (SSRLs) for
four consecutive quarters. Monthly
sampling was discontinued sitewide, and
quarterly sampling was implemented in
15 wells with semi-annual sampling in
73 other wells. The overall reduction in
monitoring frequency is estimated to
decrease annual labor, analytical, and
other direct costs by $230,000.
To help address contaminant migration in
the deeper portions of the saturated zone.
one monitoring well was converted to an
extraction well to increase pumping at 100 -
105 feet bgs. A new monitoring well
screened at 125 - 145 feet bgs is planned
for installation by April 2012 in response
to a newly discovered offsite upgradient
source that affects the western portion of
[continued on page 4]
rZone 2006 Maximum TCE 2011 Maximum TCE B
Concentration (ug/L) Concentration (ug/L) H
Perched
Saturated - 65-75 feet bgs
Saturated - 80-90 feet bgs
Saturated - 95-1 1 0 feet bgs
Saturated - 125-145 feet bgs
230
1 3,000
22,000
120
80*
26
650
430
400
150
* Estimated detection. Compound detected between the method detection limit and the method reporting limit.
1 Table 1. Maximum TCE concentrations decreased by 96 to 99% in the two years following remedy startup, although
contaminant migration has caused a slight increase in TCE concentrations in the deeper zones of the aquifer. 1
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[continued from page 3]
the site. Installation of the new well is
expected to cost $37,500, while annual
monitoring costs are estimated at $4,000.
The optimization review results also
recommended reductions in the monthly
sampling of water and vapor processed by
the onsite treatment plant. The project team
will reduce the number of process water
samples from eight (taken from multiple
lines) to one combined influent sample and
one effluent sample, eliminating process
sampling points from well headers and
intermediate locations that do not influence
system operation decisions. Optimization
of the sampling strategy will lead to a
reduction from 96 to 24 annual samples.
The project team also will reduce sampling
of vapor processed by the onsite treatment
plant to one influent and one effluent
sample per month, in contrast to the 12
vapor samples previously processed each
month. Cost savings from reduced
process water and vapor sampling are
estimated at $54,000 annually.
Eight additional effluent samples from the
onsite treatment plant are analyzed each
year for sewer discharge pretreatment
parameters as required by a Los Angeles
County Sanitation District permit. This
sampling program is not subject to
modification until the facility begins
discharging under the National Pollutant
Discharge Elimination System, tentatively
in April 2012.
Sitewide sampling of vapor and groundwater
extraction wells in October 2011 confirmed
that extraction is only needed from 16 of
about 55 vapor extraction wells and 29 of
about 57 groundwater extraction wells
(including HVDPE wells); extraction wells
exhibiting VOC concentrations below SSRLs
were turned off. The terminated wells will
be sampled for rebound during the next semi-
annual sampling event (in April 2012) to
confirm that vapor concentrations do not
return to levels above applicable standards.
The remaining active vapor extraction wells
pump at a lower rate of 200 cubic feet per
minute (cfm) rather than the previous rate
of 500 cfm, while remaining active
groundwater extraction wells pump at a lower
rate of about 20 to 25 gpm rather than the
previous rate of 31 gpm, due to optimization
review findings that a lower pumping rate
would result in the same amount of
contaminant removal. Reducing the number
and pumping rate of active extraction wells.
including HVDPE, allows the two blowers
to operate one at a time, which is expected
to reduce annual electricity costs by
approximately $40,000.
Due to reduced sampling, analysis.
reporting, and maintenance requirements
resulting from optimization of the treatment
system, the full-time workforce has
decreased from three to two plant personnel
and one "as-needed" staff member. This
reduction reduces annual labor costs by
approximately $113,000. The total annual
cost savings corresponding to monitoring
reduction, elimination of several dozen
vapor and groundwater extraction wells.
reduction in groundwater and vapor
pumping rate, conversion to an alternating
blower system, and reduction in personnel
costs is estimated at $437,000.
The site team will be conducting additional
work to identify the origin of the offsite
upgradient source that is impacting
cleanup at the site, as indicated by recent
sampling results.
Contributed by Rose Marie Caraway
(caraway.rosemarie&epa.gov or
415-972-3158) and Lynn Suer
(suer.lynn&epa.gov or 415-972-3148),
EPA Region 9
DNAPL Discovery Affects Groundwater Treatment and Anticipated Site Reuse
EPA's Region 10 office has conducted
soil and groundwater cleanup
activities at the Northwest Pipe and
Casing/Hall Processing (NWPC) site
in Clackamas, OR, since its addition
to the National Priorities List in 1992.
Efforts are underway to improve
efficacy of groundwater treatment while
accommodating ongoing and future
redevelopment of the site. The State of
Oregon is in the final phase of designing
a major six-lane highway and surface
street enhancements that will completely
transect the site. Additionally, Clackamas
County, the current owner of half the site,
has leased a large parcel to a steel
fabrication and manufacturing facility for
storage use and street car testing.
The NWPC site is located in an industrial
area approximately 20 miles southeast of
Portland. It encompasses approximately
53 acres divided into two parcels. One
32-acre parcel is the main area of
concern due to high concentrations of
VOCs in soil and groundwater that
corresponded with past use of cleaning
solvents in pipe-coating operations. A
remedial investigation completed in 2004
detected TCE in 53 out of 78 groundwater
samples, at concentrations ranging from
0.2 to 1,900 ng/L. Qs-l,2-dichloroethene
(DCE) was detected in 59 out of 78
samples at levels of 0.4 to 3,000 [ig/L.
Vinyl chloride detections in 44 out of 84
samples, at concentrations ranging from
0.6 to 340 |J,g/L, suggested that biological
reductive chlorination of TCE and
DCE was occurring gradually. Dense
non-aqueous phase liquid (DNAPL)
was not observed during the remedial
investigation.
Soil remediation primarily involved
excavation and capping in 2001-2003.
Construction of the groundwater
remedy, completed in 2004, involved use
of an in-well air stripping system
consisting of 15 groundwater circulation
wells connected to six extraction sheds,
each of which housed a blower, vapor
extraction equipment, and GAC treatment
canisters. Within a year of startup,
monitoring indicated that the system did
[continued on page 5]
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[continued from page 4]
not function as designed. Follow-up field
studies suggested that the groundwater
circulation system primarily recirculated
treated water and recovered very little
contaminated water from the aquifer. In
the following year, eight wells were shut
down and their down-hole equipment
was removed.
An optimization review was conducted
in 2007 to evaluate current performance
of the remedy, determine the need to shut
down remaining wells, and identify
potential remedy alternatives. The
optimization review report made three
primary recommendations: (1) better
define the upgradient boundary of the
plume to facilitate future remedy
decisions; (2) shut down the remainder
of the groundwater treatment system, and
(3) consider integrating alternate
approaches such as in situ bioremediation
or chemical oxidation to aggressively
treat areas with the highest VOC
concentrations. As a result, EPA
completed a focused field investigation
that involved collecting additional soil
and groundwater samples using
rotosonic drilling at 29 locations. The
samples were collected over six weeks
and analyzed at offsite laboratories for a
cost of approximately $160,000.
Analytical results showed that a
significant source of soil contamination
was upgradient and aligned with the
centerline of the main contaminant plume.
More specifically, soil data indicated three
coal tar body (DNAPL) sources. Results
from depth-discrete groundwater sampling
indicated high concentrations of chlorinated
VOCs (CVOCs) and naphthalene
encompassing or extending from those
DNAPL bodies along the direction of
groundwater flow. Concentrations of
chemicals of concern in the three water-
bearing zones (WBZs) also corresponded
to the discovery of DNAPL. PCE, TCE, cis-
1,2-DCE, and naphthalene concentrations
greater than 1,000 ug/L were observed
within or downgradient of the DNAPL bodies
in the shallow and intermediate WBZs. hi the
deep WBZ, groundwater samples showed
lower CVOCs, naphthalene, and BTEX
concentrations. A limited number of deep
WBZ samples indicated PCE and naphthalene
concentrations exceeding 1,000 u.g/L.
EPA terminated the groundwater treatment
system shortly after the optimization
review, approximately five years sooner
than originally anticipated. The shutdown
saved an estimated $166,300 each year in
O&M costs (Table 2). Well decommissioning
was postponed until 2015 to assure that
wells or ancillary equipment are not needed
for other remediation activities.
Decommissioning costs for the entire
groundwater treatment system are
estimated at $350,000.
EPA completed a time-critical removal
action in October 2009 through June 2010
to remove the coal tar bodies. The majority
of excavation occurred near groundwater
with the highest PCE concentrations, in an
area approximately 80 feet long, 24 feet
wide, and 25 feet deep. To address a
nearby but relatively isolated source area,
an interceptor trench was excavated
perpendicular to the direction of
groundwater flow and tied into the larger
excavation area at its downgradient edge.
The excavated soil was dewatered and
transported to an offsite Subtitle D
disposal facility; prior to disposal,
laboratory analysis of five-point
composite samples of the dewatered
material showed concentrations below
the disposal thresholds.
Excavated areas were backfilled with
sand, gravel, and existing overburden
and cap material, where appropriate. To
address residual soil contaminants
entering the groundwater from (or
downgradient of) the excavated areas, EPA
implemented in situ bioremediation that
would promote reducing groundwater
conditions and provide a source of organic
carbon for indigenous microorganisms.
In the majority of excavation bays, a
zerovalent, iron-organic carbon soil
amendment was dug into the base and
dosed into the backfill at either 0.6%
or 1% concentrations, depending on
the prevailing contaminant concentrations
in groundwater. The walls of remaining
sevenbay s were dosed with an amendment
made from the chitin of crab shells.
Monitoring over the past two years
indicates significantly decreased residual
VOC concentrations in the immediate
vicinity of the soil removal areas. For
[continued on page 6]
O&M Component
Estimated
Annual Cost
Labor: oversight and project management
Labor: system operation (including major repairs and equipment replacement)
Plan updates (O&M, health & safety): labor, other direct costs
Groundwater sampling and reporting: labor, equipment
Utilities: electricity
Other services: non-electric utilities, trailer rentals, etc.
Other (site visits, etc.)
Total
$12,600
$85,200
$3,900
$12,300
$20,100
$30,700
$1,500
$166,300
Table 2. Shutdown of
the remaining but
marginally effective
groundwater circulation
wells that supported air
stripping at the NWPC
site saved nearly
$98,000 in primary
labor costs and over
$50,000in utility costs
each year.
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Solid Waste and
Emergency Response
(5203P)
EPA 542-N-12-002
April 2012
Issue No. 58
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]
example, PCE concentrations in aqueous
fractions of one representative well
decreased from 2,570 u,g/L to a non-
detect level. Dechlorination and biological
indicators observed over a longer period
(since 2008) indicate that microbiological
activity and resultant dechlorination
increased significantly in the same areas
after introduction of the soil
amendments. The indicators included
increasing concentrations of dissolved
iron and methane and decreasing redox
potential and sulfate concentrations. Late
2011 monitoring results showed reversed
trends, which indicated that microbial
activity had begun declining.
Other optimization review recommend-
ations involved technical changes to the
sequencing of data collection on site-wide
water levels. Historically, this process was
performed over a two-day period in which
data were first collected for all shallow
wells, thenforintermediate wells, and lastly
for deeper wells. Since 2007, all wells in
the same vicinity have been sampled at the
same time (regardless of depth) on a single
day. This sequencing yields more accurate
information regarding vertical head
differences and horizontal water levels
using several wells with multiple screen
depths. Due to no change in the total
number of labor hours, this improvement
occurred without additional costs; site-wide
water level data is typically collected every
six months, at a cost of less than $5,000.
EPA's Region 10 office is currently
conducting a focused feasibility study
to augment the existing groundwater
remedy. Technology alternatives include
in situ bioremediation, as recommended
in the optimization review report,
combined with natural attenuation or an
ex situ pump-and-treat system to treat the
contaminant plume more aggressively.
Contributed by Mark Ader
(ader.mark&.epa.gov or
206-553-1849) and Bernie Zavala
(zavala.bernie&epa.gov or
206-553-1849), EPA Region 10
Contact Us
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Suggestions for articles may
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Phone:703-603-7198
quander.iohn@.epa.qov
FRTR Discussions on Optimization
At its November 2011 meeting, the
Federal Remediation Technologies
Roundtable (FRTR) discussed
aspects of federal efforts to optimize
site cleanup remedies. Topics
included performance-based
contracting, environmental footprint
reductions, and exit strategies. To
access the meeting presentations,
visit the FRTR online at:
www.frtr.gov/meetinqs1 .htm.
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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