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/A newsletter about soil, sediment, and ground-water characterization and remediation technologies
Issue 33
November 2007
Mulch Dual-Wall PRB Promotes Anaerobic Degradation
of Chlorinated Ethenes
The Seneca Army Depot hi Romulus, NY,
employs a double-walled configuration for
a full-scale permeable reactive barrier
(PRB) to treat contaminated ground water
at the Depot's operable unit (OU) known
as "Ash Landfill." Mulch was selected
tentatively as the reactive medium two
years ago, when rising costs for iron
hindered expansion of an existing pilot-
scale zero-valent iron (ZVI) PRB. The U.S.
Army and EPA assisted the Depot in
designing and installing the biowalls hi 2006
to reduce the cost of reactive media as
well as accelerate contaminant degradation
and enhance contaminant plume control.
Three rounds of post-installation
monitoring indicate that the biowalls
degrade virtually alltrichloroethene (TCE),
the primary ground-water contaminant of
concern (COC), and demonstrate
anaerobic degradation of TCE breakdown
products both within and downgradient of
the biowalls.
Over more than 60 years, the Depot was
used for military equipment and material
storage, supply, and maintenance, which
commonly involved use of cleaning agents
containing TCE. Cleanup of this National
Priorities List site was initiated in the early
1990s under a federal facilities agreement
among the Depot, EPA, and the New York
State Department of Environmental
Conservation. Site remediation accelerated
in 1995 when the facility was designated
for closure under the Base Realignment
and Closure program.
The Depot encompasses 10,687 acres
between Seneca Lake and Cayuga Lake in
Seneca County. The Ash Landfill OU
comprises five RCRA solid waste
management units covering 130 acres. Of
these, approximately 23 acres associated
with the OU's fonner multi-waste landfill
are contaminated with volatile organic
compounds (VOCs), semivolatile organic
compounds, polycyclic aromatic
hydrocarbons, and metals. The landfill is
located near six designated wetlands and
contains areas of potential historic and
cultural significance.
Approximately 26,000 yd3 of contaminated
soil serving as the source of ground-water
contamination were treated hi 1995 through
low-temperature thermal desorption.
Immediately prior to source removal,
maximum COC concentrations in ground
water were 960 u,g/L TCE, 2,600 u,g/L 1,2-
dichloroetliene (DCE), and 94 u,g/L vinyl
chloride (VC). Maximum concentrations in
ground water five years later were 980
Hg/L TCE, 760 u,g/L DCE, and 29 u,g/L VC.
The remaining ground-water plume is 1,100
ft long and 625 ft wide, and is vertically
restricted to the upper till/weathered shale
aquifer. Rates of ground-water flow in the
treatment area range from 100 to 400 ft/yr.
Chlorinated ethene concentrations above
State of New York ground-water standards
have not been detected in downgradient
off site monitoring wells.
In July 2005, two pilot-scale mulch biowalls
were installed in the area with historically
highest contaminant concentrations to
demonstrate whether biowalls could degrade
chlorinated etlienes and daughter products as
effectively as the ZVI PRB. In addition to cost
reductions, consideration of mulch as the
alternate reactive media was prompted by
longer-term demonstration of biowall
performance and increased regulatory
acceptance of biowalls at other chlorinated-
ethene sites. Successful pilot-scale results over
18 months led to full-scale installation of an
upgraded system last year.
[continued on page 2]
Contents
Mulch Dual-Wall
PRB Promotes Anaerobic
Degradation of
Chlorinated Ethenes page 1
Subsurface Injections
of Emulsified Soybean
Oil Accelerate PCE
Biodegradation page 3
SERDP Study Identifies
Subsurface Sampling
Methods for Enhanced
Decision-Making page 4
OSRTI Analyzes Trends in
Superfund Cleanup
Technologies page 5
State Coalition
Reviews Remedies for
Drycleaner Sites page 5
CLU-IN Resources
CLU-IN currently offers 18
regularly updated databases with
remediation profiles compiled
through past or ongoing
initiatives of EPA's Technology
Innovation and Field Services
Division. Database topics cover a
range of remediation issues such
as alternative landfill covers, in-
situ thermal treatment, in-situ
chemical oxidation, in-situ
flushing, phytotechnology, MtBE,
fractured bedrock, and pilot-
scale systems. Details and
search tools are available at
http://clu-in.org/databases/
#remed.
Recy cted/Recycl able
Printed with Soy/Canola Ink on paper that
contains at least 50% recycled fiber
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[continued from page 1]
Mulch selected for this PRB system
consists of coarsely shredded trees and
brush from seasonal landscaping work in
the Romulus area. A total of 2,800 yd3 of
mulch, coated with 9,700 gallons of food-
grade soybean oil, was mixed onsite with
2,000 yd3 of coarse sand. The mixture was
emplaced in six trenches approximately
3 ft thick and 7-18 ft deep, forming a PRB
consisting of three dual walls positioned
perpendicular to ground-water flow from
the source area (Figure 1). Parallel and
partially pivoted alignment of dual walls
with different lengths (370, 720, and
575 ft, sequentially downgradient) and
different spacing (40 and 320 ft apart)
allows the multiple treatment series to
conform to die direction and breadth of
ground-water flow. Design of the system
allowed for continued use of the two pilot-
scale walls, which were lengthened to
serve as the "middle" dual walls.
Each dual wall consists of two parallel,
filled trenches spaced 15 ft apart. This
configuration allows the upper biowall in
each pair to reduce concentrations of TCE
and native electron acceptors such as
sulfate, and the lower biowall to reduce
TCE-degradation products such as DCE
with less competition from alternate
electron acceptors. In addition, the dual-
wall construction method provides added
reinforcement in areas of higher, localized,
ground-water velocities. Driven by the
natural hydraulic gradient, contaminated
ground water passing through the biowall
contacts the slowly soluble organic matter.
This process provides a treatment zone
extending between each pair of biowalls
and as far as 200 ft downgradient from
the entire system. A 12-in soil cover above
the entire length of the biowalls impedes
surface water infiltration. Before exiting
the site, the plume is treated additionally
by the earlier-installed ZVI wall, which still
shows reactive capability.
Samples from 14 monitoring wells
analyzed this past June show that total molar
concentrations of chlorinated ethenes in
ground water passing through the
treatment zone decrease 86-99%. TCE
concentrations in ground water decrease
from 2,000 |J,g/L upgradient of the
Figure 1. After
ground water
passes through the
third biowall of the
Depot's PRB
system, vinyl
chloride accounts
for the majority of
its chlorinated-
ethene content.
biowalls to 6 \ig/L immediately downgradient
of the lower pair of biowalls, and to 1 |ag/L
in a monitoring well immediately outside the
site perimeter.
Concentrations of total organic compounds,
reflecting the amount of carbon available
for anaerobic degradation of contaminants,
have increased from approximately 10
mg/L upgradient of the biowalls to 309
mg/L in the middle pair of biowalls.
Concentrations of VC increase from an
average of 3.3 |j,g/L upgradient of the upper
biowalls to 81 [ig/L approximately 42 ft
downgradient of the middle biowalls.
Additional evidence of etliene biodegradation
in the treatment zone is provided by depleted
concentrations of dissolved oxygen and
sulfate, elevated concentrations of methane,
and reduced oxidation/reduction potential.
Review of the project's engineering methods
suggests that use of a continuous trencher
rather than a conventional backhoe would
have avoided sloughing of sidewalls during
PRB construction. To date, no detrimental
changes in hydrologic or geochemical
conditions of the aquifer as a result of
treatment have been observed.
Degradation of the aquifier's remaining VC
is expected to occur most readily in aerobic
zones located upgradient and downgradient
of the biowall system.
Project costs totaled approximately
$288,000. Recharging of the biowall
system through installation of injection
points and injection of soybean oil into the
mulch/sand mixture, at the relatively low-
cost of $75,000, is anticipated after 3-5
years of operation. Continued ground-
water monitoring is conducted to confirm
concentrations of TCE and VC meet state
water-quality standards.
Contributed by Julio Vazquez, U.S. EPA
Region 2 (vazquez.julio&epa.gov or
212-637-4323), Stephen Absalom,
Seneca Army Depot
(Stephen.m. absolom(q).us. army.mil or
607-869-1309), and Todd Heino,
Parsons (todd. heino(q)p arsons, com or
617-449-1405)
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Subsurface Injections of Emulsified Soybean Oil Accelerate PCE Biodegradation
The U.S. Air Force Centerfor Engineering
and the Environment (AFCEE) recently
completed a full-scale demonstration of
enhanced in-situ anaerobic bioremediation
at Former Newark Air Force Base (AFB)
near Columbus, OH. An emulsion of
vegetable oil and water was injected into
the subsurface in two phases to stimulate
anaerobic biodegradation of chlorinated
ethene and ethane contamination in ground
water. Within 24 months after the final
injections, contaminant concentrations
decreased to levels below cleanup goals
at all but one monitoring location.
The demonstration took place at the
"Former Facility 87" site (FF-87) located
in the southeast corner of the 70-acre
former AFB property surrounded by
industrial, farming, and residential
properties. FF-87 consisted of a semi-
enclosed building that was used to store
drums of used solvents and spent Freon
113 coolant. Chemical spills inside the
building were controlled by drainage
ditches and berms surrounding the
building. Later site investigations, however,
determined that spills on the building's
asphalt floor migrated vertically
downward to impact vadose-zone soils
and ultimately the underlying ground
water. The building was demolished and
the building floor as well as contaminated
subsurface soil were excavated and
disposed offsite. The base's main
production building, located cross-
gradient from FF-87, is now zoned for
industrial use and hosts the manufacture
of aircraft equipment.
Cleanup goals were set at site-specific,
risk-based standards of 5 |J,g/L
tetrachloroethene (PCE), 5 [ig/L TCE,
20 |lg/L c;s-l,2-DCE, 68 [ig/L 1,1,1-
trichloroethane (1,1,1-TCA), and 43 [ig/L
1,1-dichloroethane (1,1-DCA). Prior
to the demonstration, maximum
concentrations were 1,300 [ig/L PCE,
Figure 2. Spikes in PCE concentrations at
a single monitoring well suggest that PCE
mass from a residual contaminant source
in capillary-fringe or vadose-zone soil is
being added to FF-87 ground water.
13 |lg/L TCE, 46 \lg/L c/s-l,2-DCE,
150 [ig/L 1,1,1-TCA, and 31 |jg/L
1,1-DCA. Soil in the treatment area
comprises approximately 8 feet of silty clay
underlain by a silty to gravelly sand water-
bearing unit. The sand water-bearing unit
is in turn underlain by a second, lower
permeability silt unit and finally by a low
permeability clay aquitard. Ground water
is encountered at approximately 9-14 ft
below ground surface (bgs) and migrates
at approximately 1,000 ft/yr within the sand
unit. No evidence of dense non-aqueous
phase liquid (DNAPL) was observed during
pre-injection site investigations.
Food-grade vegetable oil was selected as
the injectant substrate due to its low cost
and ability to slowly release organic carbon
over a long period of time (typically 2-5
years). Use of the organic carbon by native
microoranisms depletes the aquifer's
dissolved oxygen (DO) and lowers its
oxidation-reduction potential, creating
conditions conducive for anaerobic
degradation of chlorinated VOCs. Once
DO is consumed and reducing
geochemical conditions are established, a
portion of the vegetable oil-derived organic
carbon is used for contaminant mass
destruction through biologically mediated
reductive dechlorination.
The initial injection in September 2001
employed a vegetable oil emulsion
consisting of 25% partially hydrogenated
lecithin-enhanced soybean oil and 75%
native ground water extracted from an
upgradient monitoring well showing
COC concentrations below maximum
contaminant levels. Pre-injection field
preparations involved installing a network
of six injection wells, nine ground-water
monitoring points, and two soil-vapor
monitoring points. Approximately 3,200
gallons of vegetable oil-in-water
emulsion containing 600 gallons (5,120
pounds) of oil were injected into each of
three shallow injection wells screened in
the sand at a depth of 17-20 ft, and 230
gallons of the emulsion were injected into
three deeper injection wells screened in
the lower silt at 21.5-25 ft. Following
emulsion injection, 50-150 gallons of
additional native ground water were
injected into each shallow/deep injection
point to improve substrate distribution. The
injections were completed over three days
at rates of 4 gallons per minute (gpm) in
deep wells and 7 gpm in shallow wells.
Cleanup goals were met within six
months for all but one monitoring location
directly downgrade of the asphalt-floored
building. Additional substrate was injected
in October 2003 to address the single
shallow monitoring well exhibiting no
changes in contaminant concentrations.
Approximately 55 gallons of the same
substrate were emulsified with 550
gallons of native ground water (a more
dilute 1:9 ratio) and injected into each of
four new shallow, direct-push injection
points. Emulsion injections were
conducted at a rate averaging 6 gpm with
pressures of 13-18 psi, reaching a depth
[continued on page 4]
2100
1800
~5 1500
-S 1200
§ 900
<§
LJJ
O
300
600
0
873
872
871
870
869
868
867
866
Date
• PCE —•— Water Table Elevation
Base of Upper Silt]
-------
[continued from page 3]
of 15-17 ft bgs. Each was followed by
injection of 25 gallons of additional
uncontaminated native ground water to
improve substrate distribution.
Within three months of the second round
of injections, concentrations of PCE at the
target well decreased approximately 80%
and concentrations of c/'s-l,2-DCE, VC,
and ethene increased substantially.
Subsequent ground-water monitoring has
shown temporal increases in PCE
concentration, followed by temporal
increases in TCE, c;'s-l,2-DCE, and VC.
Monitoring also shows that the increases
in contaminant concentrations are preceded
by increases in ground-water elevation
(Figure 2). These results indicate that more
PCE mass lias been degraded than originally
estimated to exist in the saturated treatment
zone, and mat an unrecognized source of
sorbed contaminant mass likely continues
to release PCE to the aqueous phase during
times of high water-table elevations.
Capital costs forthe initial injections totaled
$79,600, including $2,400 forvegetable oil
substrate, and operating costs for both
rounds of injections totaled $228,800. Due
to the significantly high cost of continued
ground-water monitoring in the area still
exhibiting PCE concentrations above the
state standard (5 ng/L), approximately
3,000 cubic yards of soil will be
excavated and disposed offsite in 2008.
Demonstration findings suggest that more
complete site characterization would have
resulted in more successful and rapid
remediation of the entire site.
Contributed by Javier SantiHan, AFCEE
(Ja\>ier/santillan(q)brooks.af.mil or 210-
536-4366), Donald Buelter, Former Ne\v ark
AFB (don.buelter&afrpa.pentagon.af.mil
or 210-925-3100), and Dan Griffiths
(daniel.r.griffiths&parsons.com or
303-764-1940)
SERDP Study Identifies Subsurface Sampling Methods for Enhanced Decision-Making
The Colorado School of Mines (CSM) is
conducting laboratory studies and
mathematical modeling to develop
improved methods for data collectionfrom
ground-water wells and soil cores used
in remediation. Current work under this
Strategic Environmental Research and
Development Program (SERDP) project
targets sites contaminated with chlorinated
solvents, including those with DNAPL
source zones. One element of this project
quantifies measurement errors associated
with methods for collecting soil-core
samples used in analyses of organic
contaminants. Early findings indicate
that different methods for obtaining
soil-core samples can lead to DNAPL
concentrations varying by several
orders of magnitude. Depending
on the type of DNAPL organics
and subsurface properties, these
method differences may carry
negative bias up to nearly 100%.
An informal survey of 18
remediation professionals provided
Figure 3. Consistently highest TCE
recovery from a spiked soil core was
measured through a sample
collection method involving direct
sample placement into ajar
containing methanol with minimal
atmospheric exposure.
insight into field practices, revealing that
the most common method for subsurface
soil sampling is to: scoop soil from a core
into an empty sample jar, pack the
contained sample to minimize headspace,
cap it, store it at low temperature, and
send it to an offsite laboratory for
analysis. Results of the survey were used
to design laboratory studies focused on
five soil-sampling methods with different
levels of media disaggregation and
atmospheric exposure (MDE) and
different susceptibilities to measurement
error and uncertainty (Figure 3 inset).
These sampling methods were tested
during collection of soil samples from
water-saturated sand cores at soil
temperatures ranging from those
typical of ambient conditions across the
U.S. to those following thermal
remediation. The cores were spiked
with TCE, PCE, or 1,1,1-TCA at varied
concentrations.
Measured TCE concentrations in cores
ranged from 20% to 112% of the known
(48 mg/kg) concentration (Figure 3).
Comparison of concentrations
measured in samples collected using
each of the five methods indicated
significant differences and distinct
trends based on soil temperatures as
well as (simulated) field methods. The
[continued on page 5)
Method 1: Place core sample ring in a jar
with methanol (low disaggregation [D] and
atmospheric exposure [E])
Method 2: Sub-sample core into a jar with
methanol (high D but low E)
Method 3: Store non-preserved sample on
ice overnight in a sampling/storage device
(such as EnCore®) before extruding into
methanol (moderate D and E)
Method 4: Sub-sample core into a jar, pack
and cap jar, place it on ice for 24 hours, then
open jar and sub-sample soil into methanol
(highest D and E)
Method 5: Use micro-coring device to obtain
a plug of soil and extrude it directly into
methanol (low D and E)
4
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[continued from page 4]
most accurate data were obtained at
soil temperatures at or below 40°C
using a sample collection method with
low MDE. Analysis of PCE and TCA
datasets revealed similar trends.
Preliminary study results indicate that use
of low-MDE methods employing an
extraction solvent in the field (Methods
1, 2, and 5) yields the most accurate and
unbiased estimates of subsurface
concentrations of chlorinated solvents.
Though easy and historically most
common, sample collection relying on
cooled storage and next-day placement
into methanol (Method 4) yields poor-
quality data with high negative bias.
Soil samples yielding negatively biased data
can result in underestimates of site-wide
concentrations before and during
remediation, potentially leading to errors
regarding treatment efficacy. This potential
can be amplified at sites where remediation
causes a change in subsurface properties
that in turn impact contaminant behavior
such as changes in organic content or
elevated temperatures. As shown in early
site-specific studies, negatively biased data
can lead to poor design of a remediation
system as well as increased duration and
cost of treatment.
Final results from these tests and follow-
up investigation of additional DNAPL
contaminants and concentrations, soil
types and temperatures, and sampling
methods, along with associated cost/
benefit analyses, will be available from
SERDP in 2008 (online at http://
www.serdp.org1.
Contributed by Robert L. Siegrist,
Ph.D., CSM (siegrist&mines.edu or
303-384-2158), Ryan Oesterreich,
CSM (roesterr(a)mines.edu), and
Andrea Leeson, Ph.D., SERDP
(andrea. leeson(q)osd.mil or
703-696-2118)
OSRTI Analyzes Trends in Superfund Cleanup Technologies
EPA's Office of Superfund Remediation and Technology Innovation (OSRTI) recently published the 12th edition of Treatment
Technologies for Site Cleanup: Annual Status Report (ASR), which summarizes information from approximately 3,000 records
of decision signed since 1982 for 1,536 National Priorities List (NPL) sites. This edition documents technology applications for
more than 1,900 soil and ground-water cleanups, including 192 projects initiated in 2002-2005. To address increased use of
containment remedies such as final cover systems (caps), the ASR now describes the state of this practice based on 112 cover
systems at 89 NPL sites and 57 vertically engineered barriers at 55 NPL sites. The online version (at http://clu-in.org/asr/) also
provides links to new downloadable spreadsheets containing key data used in the report.
State Coalition Reviews Remedies for Drycleaner Sites
The State Coalition for Remediation of
Drycleaners (SCRD) reviewed data from
drycleaning sites located across the U.S.
to identify trends in remedial technologies
used to treat soil and ground water. The
SCRD is made up of the 13 states having
programs devoted to remediation of
contaminated drycleaning sites. With
assistance from EPA's Technology
Innovation and Field Services Division,
SCRD compiled a database of 116
drycleaning remediation projects within
15 states, of which 12 are member
states. The database includes application-
specific information such as site settings
and history, geology and hydrogeology,
soil and ground-water contaminant
concentrations and distributions,
remediation technologies, cleanup
closures, and cleanup costs.
Of the 116 sites reviewed, 97 are
drycleaning facilities that exclusively used
PCE as a solvent, while 4 used petroleum-
based solvents and 15 used both. Forty-
four of the sites are located in Florida, and
55 were active facilities at the time of the
study. SCRD identified several trends in
the contamination found and the remedial
actions conducted at the study sites:
z'/ Contamination and Remediation:
Soil contaminants were detected at 106
sites, with PCE and its degradation
products (e.g., TCE and DCE) found
at 64 of these sites. Petroleum-related
contaminants were the most common
non-PCE -related compounds detected.
Although petroleum solvents were used
exclusively at 4 sites, spotting agents,
detergents, fuel oil, and gasoline were
potential sources of these contaminants
at these and other sites.
Remediation was conducted in un-
saturated soil at 100 sites using ex-
cavation/removal (44 sites); soil va-
por extraction/passive venting, in-
cluding multi-phase extraction (63);
biostimulation (6); in-situ chemical
oxidation (6); ZVI soil mixing (1); and
a mobile-injection treatment unit (1).
Ground-Water Contamination and
Remediation: Dry cleaning-related
contaminants were detected in ground
water at all of the study sites. PCE
was detected in ground water at 114
of the 116 study sites, including those
using only petroleum solvents-likely
the result of using PCE in spotting
agents. PCE degradation products
were detected at 107 sites. Presump-
tive evidence of PCE DNAPL, inferred
by a PCE concentration of 1.5 mg/L
or more in ground water, was found
at 70 of the sites.
Ground-water remediation was
conducted at 87 of the study sites.
Of these, conventional pump and
treat, air sparging, and multi-phase
[continued on page 6)
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Solid Waste and
Emergency Response
(5203P)
EPA542-N-06-012
November 2007
Issue No. 33
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]
extraction were used at less than
half, while innovative technologies
were used at 63 sites: chemical
oxidation (27 sites), bioremediation
(26), recirculating wells (in-well
sparging) (6), cosolvent/surfactant
flushing (2), co-oxidation (1), and a
ZVIPRB(l).
Together, chemical oxidation and
bioremediation account for over
60% of the ground-water treatment
systems and 73% (27 of 37) of the
closed ground-water sites in the study.
Only 1 of the 37 closed sites had em-
ployed pump and treat, and none em-
ployed multi-phase extraction, the sec-
ond most common conventional
ground-water system.
Of the 37 cleanup-closure sites, 23 were
closed solely through soil remediation,
and 13 required engineering and/or
institutional controls. Total costs for
cleanup, including assessment, remedial
design/installation, monitoring and
operation/maintenance, were available
for 28 of the 116 study sites. The total
project cost ranged from $46,200 to
$1,662,000, and averaged $216,900.
Study findings recognize that these
estimates represent low-end costs for
sites with limited contamination or low
difficulty in remediating. SCRD recently
published the results of the study in
Comparison of Remedial Systems
Employed at Drycleaners (http://
www.dry-cleancoalition.org/download/
site_profile_paper. pdf).
Contributed by Eric Cathcart, South
Carolina Department of Health &
Environmental Control
(cathcaef(q).dhec. sc. gov or
803-896-6847), Bob Jurgens, Kansas
Department of Health & Environment
(bjurgens&kdhe. state, ks. us or
785-291-3250), and Bill Linn,
Florida Department of Environmental
Protection fwi/liam./innCaldep.state, fl.us
or 850-245-8939)
Contact Us
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Office of Superfund Remediation
and Technology Innovation
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1200 Pennsylvania Ave, NW
Washington, DC 20460
Phone:703-603-7198
Fax:703-603-9135
EPA is publishing this newsletter as a means of disseminating useful information regarding innovative and alternative treatment techniques and
technologies. The Agency does not endorse specific technology vendors.
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