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                        /A newsletter about soil, sediment, and ground-water characterization and remediation technologies
                       Issue 27

This issue of Technology News and Trends highlights various techniques used to design,
construct, and operate permeable reactive barriers containing organic reactive media. Imple-
mentation of these "biobarriers" (PRBs) involves amending the aquifer with relatively inex-
pensive and readily available carbon-donor materials capable of enhancing biological degra-
dation of contaminants. Several federal agencies are evaluating this technology particularly
for treatment of ground water contaminated with perchlorate or volatile organic compounds.
                                                                                 November 2006
          Emulsified-Oil Biobarrier Provides Long-Term Treatment
                          of Perchlorate/VOC Plume
  The U.S. Department of Defense (DOD)
  has nearly completed an Environmental
  Security Technology Certification Program
  (ESTCP) evaluation of a PRB containing
  emulsified oil substrate (EOS®). The pilot
  study was initiated in 2003 at the Alliant
  Techsystems, Inc., facility inElkton, MD,
  to  evaluate  effectiveness  of EOS
  technology for enhancing biodegration of
  perchlorate and chlorinated solvents. A
  single dose of low solubility, low viscosity,
  and slowly biodegradable  edible-oil
  emulsion was injected directly into the
  contaminated  aquifer.  Post-treatment
  monitoring indicates that introduction of
  this reactive medium provided sufficient
  organic carbon  to support biological
  degradation of target contaminants and
  consistently   maintain  contaminant
  concentrations below target levels for
  nearly three years.

  Historical activities at  the site include
  manufacturing of solid propellant rocket
  motors. In the 1980s, routine ground-
  water monitoring revealed ground-water
  contamination resulting from a permitted
  hazardous waste surface impoundment.
  Site conditions amenable to an EOS PRB
  included a shallow aquifer located 5-15 feet
  below ground surface (bgs) consisting of
  silty  sand and gravel  with moderate
  permeability (-29 ft/day),  and a ground-
                         water flow velocity of approximately 100
                         ft/year. Demonstration ease was enhanced
                         by  well-defined  distribution   of
                         contaminants in a  commingled plume
                         emanating from a closed surface-water
                         impoundment. Average  concentrations of
                         target contaminants  in the treatment area
                         were 9,000 mg/L perchlorate,  11,000
                         mg/L 1,1,1-trichloroethane (TCA),  50
                         mg/L perchloroethene (PCE), and  90
                         mg/L trichloroethene (TCE).

                         The demonstration was  designed to
                         evaluate distribution of the emulsified oil
                         sufficiently to form  a PRB perpendicular
                         to ground-water flow, injection impacts on
                         aquifer permeability and ground-water
                         flow paths, and changes in contaminant
                         concentrations  and  biodegradation
                         indicators during  ground-water flow
                         through the biobarrier. The technology
                         employs  emulsified-oil  concentrate
                         consisting of food-grade  soybean oil,
                         surfactants, amino  acids, and vitamins
                         blended to form a stable emulsion with
                         small, uniformly sized oil droplets. Once
                         injected, the oil droplets adhere to sediment
                         surfaces and form a residual oil phase that
                         provides  a carbon  source  and electron
                         donor for long-term in-situ anaerobic
                         biodegradation of contaminants.

                                         [continued on page 2]
                                                                            Contents
Emulsified-Oil
Biobarrier Provides
Long-Term Treatment
of Perchlorate/VOC
Plume              page 1

DOD Compares
Benefits of Active
and Semi-Passive
Biobarriers           page 3

Alternate Strategies
Used to Implement
Mixed-Substrate
Biobarriers at
Defense Facilities    page 4
     CLU-IN Resources
The U.S. EPA Technology
Innovation Program (TIP)
continues to develop compre-
hensive information sources
on key issues related to the
use of innovative technologies
for site characterization and
cleanup. TIP's primary web
site, CLU-IN, includes infor-
mation currently bundled into
nine "Contaminant Focus"
categories of chemical
groups: arsenic, chromium VI,
1,4-dioxane, mercury, MTBE,
perchlorate, persistent organic
pollutants, PCBs, and TCE.
Related guidance, technical
reports, and training opportu-
nities for these focus areas
are available at: http://clu-
in.org/contaminantfocus/.
                                                                                                Recycled/Recyclable
                                                                                                Printed with Soy/Canola Ink on paper that
                                                                                                contains at least 50% recycled fiber

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[continued from page 1]
 In October 2003, the biobarrier was
 constructed approximately  150 feet
 downgradient from a former source
 area. A Geoprobe® was used to install
 ten injection wells 5 feet on center to a
 depth  of 15 feet bgs. Each well was
 constructed with 10 feet of 0.02-inch
 slotted screen and casing to the surface,
 and finished with a sand pack and
 bentonite  seal.  The injection setup
 included  minimal equipment:  a
 temporary solution mixing/holding tank,
 a gasoline-powered transfer pump,
 injection hoses, flow meters, pressure
 gauges, and valves. Over two days, a
 two-person crew injected a total of  55
 gallons of  diluted emulsion (1:4 EOS
 and water)  into each of the  10 wells,
 followed by 165 gallons of chase water
 to distribute and immobilize the
 emulsion. Soil sampling showed that the
 oil was distributed between the injection
 wells and up to 10 feet downgradient,
 forming a uniform PRB approximately
 50 feet wide and  10 feet thick along the
 direction of ground-water flow.

 Ground-water conditions upgradient of
 the barrier generally were oxidative with
 elevated dissolved oxygen (DO >2 mg/L),
 positive oxidation/reduction potential
 (ORP >100 mV), and measurable nitrate
 (9.5 mg/L) and sulfate (35 mg/L).
 Emulsion injection resulted in anaerobic
 conditions within  and  immediately
 downgradient of the barrier, with a rapid
 decline in ORP, DO, nitrate, and sulfate.
 Dissolved manganese and iron increased
 shortly after emulsion injection followed
 by slower production  of methane.
 Within five days  of the injection,
 perchlorate concentrations  in injection
   Figure 1. Perchlorate concentrations
   decreased to below the detection limit,
   and 1,1,1-TCA concentrations
   decreased more than 95% in ground
   water 20 feet downgradient of the
   Alliant Techsvstems biobarrier.
wells and  monitoring wells 12 feet
downgradient decreased more than 99%.
One monthafterthe injection, 1,1,1-TCA
concentrations in the injection  and
downgradient wells began to decrease
with   concurrent   production   of
1,1-dichloroethane (1,1-DCA)  and
chloroethane.

Though implemented on only a pilot scale,
this ground-water treatment approach
continues  to  promote  contaminant
degradation, and additional injections have
not been required. Two and a half years
after  the only  emulsion  injection,
monitoring  wells 20 feet downgradient
of  the  barrier  show  perchlorate
concentrations remaining  below the
analytical detection limit (<4 |J,g/L) and
1,1,1-TCA concentration reductions
exceeding 95% (Figure  1). Hydraulic
conductivity measurements indicate
emulsion injection has resulted in some
decline in hydraulic conductivity due to
biomass growth and/or gas production.
Tracer tests and detailed mapping of the
perchlorate distribution indicate, however,
that the change in hydraulic conductivity
has not adversely  impacted barrier
performance or caused significant flow
around the barrier.  Monitoring will
continue until late 2007 to obtain
additional information on barrier
longevity.

Installation of the pilot-scale PRB,
including   two  drums  of   EOS
concentrate,  cost  approximately
$23,000 ($46/ft2 of barrier). Significant
economies of scale are anticipated for
installation of larger barrier systems
involving wider well spacing. For
example, the total cost of a 200-foot PRB
at the same site with 10 injection wells
spaced 20 feet on center is estimated at
$38,000 ($19/ft2). A  final cost and
performance report  detailing  this
evaluation will be issued in late 2007.
Additional information on this project,
detailed procedures  for designing
emulsified-oil biobarriers, and  other
applications of this  technology for
source-area treatment can be  found at
www.estcp.org.

Contributed by Andrea Leeson,
Ph.D., SERDP/ESTCP
(andrea.leeson(a).osd.mil or 703-696-
2118), Robert C. Borden,  Ph.D., and
M. Tony Lieberman (Solutions-IES,
Inc. (rcborden&solutions-ies.com or
tlieberman(q).solutions-ies.com,
919-873-1060)
        15,000
    J!  10,000-
    o
                                         o
                                         O
          5,000
                                             Perchlorate
                                             1,1,1-TCA
                                             1,1-DCA
                                             Chloroethane

                       200     400     600     800
                       Days Since EOS Injection
                     1,000

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                     DOD Compares Benefits of Active and Semi-Passive Biobarriers
Current ESTCP demonstrations are
examining design, construction, and
performance elements of a semi-passive
barrier  at  the  Longhorn  Army
Ammunition Plant (AAP) in Karnack,
TX, and those of an active barrier at the
Navy Industrial Reserve Ordnance Plant
(NIROP) in West Valley  City, UT.
DOD's upcoming guidance manual for
characterizing   and   remediating
perchlorate-contaminated ground water
will  reflect site applicability, benefits,
and disadvantages identified through the
demonstrations.

The  evaluation focuses on developing
optimal strategies for  delivering and
distributing soluble  ground-water
amendments  serving as  organic
substrates (the electron donor), thereby
creating an in-situ biobarrier. The active
approach   relies   on  continuous
recirculation of ground water into which
amendments are injected, while the semi-
passive approach uses intermittent
recirculation of amendments (Figure 2).
Both approaches employ an electron
donor in soluble form that allows easy
        Plan View of Semi-Passive Barrier
    Ground-Water Recirculation with Intermittent Operation
                        During Active (pumping) Phase
           Plan View of Active Barrier
         Ground-Water Continuous Recirculation
                                distribution in the subsurface target zone.
                                This  strategy relies upon addition of
                                electron donor in quantities high enough
                                to achieve target perchlorate reductions,
                                but low enough to avoid negative
                                impacts on  secondary water-quality
                                characteristics. In contrast, a fully
                                passive system involves injection of large
                                quantities of electron donor during a single
                                injection event, which maintains reducing
                                conditions for several years but can more
                                adversely affect secondary water-quality
                                characteristics.

                                The  Longhorn AAP semi-passive
                                biobarrier was constructed  down-
                                gradient of a former landfill, where earlier
                                investigations identified a 250-foot-wide
                                perchlorate plume with concentrations
                                exceeding 3,000  |J,g/L. A shallow aquifer
                                extends to a depth of 35 feet bgs within
                                interbedded  sand,  silt, and clay,  and
                                ground-water velocity in the treatment
                                zone is approximately 37 ft/yr.

                                Five  recirculation  wells with 10-foot
                                screens were  installed in 35-foot
                                spacing along a line perpendicular to
                                              ground-water flow.  The
                                              wells were designed for
                                              use  as either injection
                                              or  extraction  wells,
                                              depending upon selected
                                              ground-water recirculation
                                              patterns. The top of each
                                              well screen  generally
                                              coincides with the area's
                                              water table, at 14-17 feet
                                              bgs.  Following pump
                                              tests and ground-water
                                                 Figure 2. Semi-passive
                                                 and active biobarriers
                                                 relv on the same
ffl injection well
H extraction well
                        electron donor in ground-water
                                                 but involve contrasting
                                                 engineering factors and
                                                 electron distributions in
                                                 the subsurface.
modeling, two intermediate injection
wells with 15-foot screens were installed
between  each  of  the  adjacent
recirculation wells to enhance substrate
distribution.   Incorporation   of
intermediate  wells resulted in an
estimated 33% reduction in time needed
for ground-water recirculation and
associated distribution of electron donor
across the full barrier. Ground-water
travel time between injection and
extraction points ultimately ranged from
one to several months, depending on
flow regimes across the treatment area.

Prior to amending the aquifer,  ground-
water extraction pumps in two of the
recirculation wells began  operating at
extraction rates of 1.7 and 1.0 gpm.
After five weeks of recirculation and a
tracer test, soluble (60%) sodium lactate
was added as an electron donor through
three  injection   wells  and eight
intermediate wells on a batch basis three
times  each week.   Over a three-week
period beginning in late March 2004, a
total of 273  gallons of sodium lactate
were  injected into the aquifer. The
recirculation system was turned off, and
the system was allowed to operate in a
passive mode for eight months, after
which a second amendment (using 443
gallons  of  sodium lactate)  was
conducted.

Ground-water sampling indicated
perchlorate concentrations within the
biobarrier had decreased from an
average of 450 |j,g/L to approximately
13 |J,g/L  within approximately three
months after the second injection cycle.
Only  minimal impacts on secondary
water-quality characteristics  such as
increased  sulfide  or  manganese
concentrations were noted. Ground-
water sampling   after the  second
amendment also indicated variability in
contaminant reductions within different

              [continued on  page 4]

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[continued from page 3]
areas of the biobarrier. Subsequent
tracer tests  suggested that one portion
of the barrier  received less electron
donor than the remainder. A third
injection cycle was conducted 11
months later, in November 2005, using
an alternate ground-water recirculation
pattern.  This  system modification
resulted in successful distribution of
electron donor across the biobarrier and
more  consistent   reductions   in
perchlorate  concentrations.

In contrast, an active rather than semi-
passive biobarrier was selected for use
at NIROP due  to greater concern
regarding  potential  impacts   on
secondary water-quality characteristics.
The active system also was anticipated
to more effectively degrade perchlorate
existing  in a deeper (120  feet bgs)
aquifer within sandy lithology. A dual-
well extraction system began operating
in late 2005, using ethanol as an electron
donor delivered into a central injection
well. After 2-3 months of operation, initial
field results suggested that the use of
ethanol may  accelerate fouling of the
injection well due to  site-specific
geochemical conditions.

System  operation was  temporarily
suspended  in  order to  complete
modifications that would allow use of
citric acid  as an electron donor, and
operations resumed last summer. Ground
water currently is extracted from the two
extraction wells at rates of 10 and 50 gpm,
amended with citric acid, and re-injected
into the central  injection well on a
continuous basis. Concentrations of citric
acid are controlled closely, with only small
increases being made to approach but not
exceed the stoichiometric demand of 7.3
mg/L.

Previous applications of active and semi-
passive approaches for electron delivery
suggest that the active approach more
effectively distributes and  controls
ground-water amendments and is less
likely   to  impact  ground  water.
Implementation of an active system
involves higher costs, however, due to
increased infrastructure and field
operations. Although an active system
may require fewer wells, continuous
operation of the wells and associated
fouling-prevention measures additionally
increase costs  for operations  and
maintenance (O&M).

A final cost and performance report on
the  two demonstrations  will  be
available in early 2007 on DOD's
ESTCPweb site (http://www.estcp.orgX
DOD anticipates publication and ESTCP
posting of  the guidance  manual,
including field and laboratory protocols,
later next year.

Contributed by Andrea Leeson, Ph.D.,
SERDP/ESTCP
(andrea.leeson&.osd.mil or 703-696-
2118), Evan Cox, and Tom Krug,
Geosyntec (tkrug&geosyntec. com or
519-822-2230)
       Alternate Strategies Used to Implement Mixed-Substrate Biobarriers at Defense Facilities
The U.S. Navy and U.S. Air Force are
testing various approaches to the design,
construction,   and  operation   of
biobarriers for enhancing anaerobic
bioremediation of chlorinated volatile
organic compounds (CVOCs) and
perchlorate found at many military
facilities. Comparison of systems at the
Naval Weapons Industrial Reserve Plant
(NWIRP)  in McGregor, TX, and
Whiteman Air Force  Base (AFB)
southeast of Kansas City, MO, indicate
that the technology may be implemented
for short-term use (as at Whiteman AFB)
or long-term use involving  engineering
elements incorporated during barrier
construction to  facilitate  carbon
rejuvenation (NWIRP McGregor).
Applications at these facilities and other
sites illustrate that factors such as media
availability, restoration objectives, and
budgetary factors play significant roles
in biobarrier design and construction, and
confirm earlier findings  that the
technology is best suited to shallow ground
water.

Nearly 2.5 miles  of a biobarrier were
installed in segments within shallow
weathered  limestone  at   NWIRP
McGregor in 2002 to reduce source-area
perchlorate plume mass, remediate
contaminated  ground  water before
discharge into surface  water, and
expedite offsite property cleanup. (For
background information, view the
February  2004 issue of  Technology
News and Trends  online at http://
www.cluin.org). Prior to construction,
extensive bench- and pilot-scale studies
were  conducted  to evaluate organic
media  and  potential  construction
methods. Full-scale construction involved
excavation of more than 13,000 linear feet
of trenches and backfilling with a
mixture of mushroom compost, 3/4-inch
pine wood chips, soybean oil, and 1-
inch crushed limestone. Horizontal
sections of perforated polyvinyl chloride
piping were installed  along the trench
bottoms  for   future  biobarrier
rejuvenation.  Construction costs
averaged $200/ft2 per linear foot or less
than $15 per vertical foot.

Periodic monitoring  of geochemical
indicators  such as ORP, total organic
content (TOC), and nitrate suggested
that carbon rejuvenation eventually
would be required to sustain long-term
effectiveness of the biobarrier. In August
2006,  nearly  22,000 pounds of an
emulsified oil substrate (EOS) solution
were injected into 15 onsite and offsite
biobarrier segments about four years
               [continued on page 5]

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[continued from page 4]
after installation. Follow-on analytical
sampling will be conducted this month
to assess carbon-substrate injection
effectiveness.

Sample analysis indicates that  the
biobarrier continues to effectively treat
perchlorate-contaminated ground water,
reducing  concentrations within  the
barrier from 1,000 ug/L to below the
laboratory detection limit of 2  u,g/L.
Effective use of the biobarrier and other
remedial measures resulted in gaining
"operating properly  and successfully"
approval for the entire remedial system
in June  2006. Accomplishing this
milestone facilitates upcoming transfer
of 3,700 acres of the NWIRP property
to  the   City  of  McGregor  for
redevelopment.

The alternate biobarrier strategy at
Whiteman AFB (in an area known as
"Site DP-32") employed lessons learned
at NWIRP McGregor,  many of which
involved a streamlined  design, more
conventional  construction equipment,
and a simpler reactive  media mix. The
Whiteman AFB biobarrier was installed
in the vicinity of a site disposal pit that
was part of a  former water treatment
plant and possibly also used as a hospital
burn pit. After the treatment plant was
relocated to the west side of the base in
the 1960s, military family housing
(including a playground) was placed in
the area.  The housing units and
playground were demolished in 2005,
and the area is expected to be used for
future training activities.

In 2002, field investigations identified
CVOCs (primarily TCE) in the area's
ground water at concentrations reaching
1,000 u,g/L. In addition, surface water in
a downgradient creek  contained TCE
concentrations approaching 200 u,g/L.
During remedy selection, a biobarrier was
selected over a ZVI PRB and a ground-
water recovery/treatment system  due to:
 >  Successful biobarriers at Offutt Air
   Force Base, NE, and Altus Air Force
   Base, OK, showing that organic-mulch
   biobarriers effectively remediate shal-
   low TCE-contaminated ground water;
 >  Ready availability of no-cost organic
   media;
 >  Significant savings  in construction
   costs compared to a ZVI PRB and in
   O&M costs compared to a ground-
   water recovery and treatment system;
 >  Absence of aboveground system ele-
   ments interfering with ongoing site
   operations; and
 >  Limitations  posed by   minimal
   hydrogeologic data (particularly related
   to ground-water residence time) that
   would not impact biobarrier design and
   implementation.
A full-scale 270-foot-long, 10- to 20-foot-
deep  biobarrier was  constructed  at
Whiteman AFB in March 2004 as part of
a treatability study.  The  system was
installed in a 5- to  10-foot-thick clayey
gravel (weathered bedrock) layer using
conventional excavators (Figure 3).
Keying into an underlying and competent
shale layer, the barrier trenches were
constructed in approximate  40-foot
sections to minimize side-wall sloughing
and facilitate ground-water management
during field activities. Trenches were
backfilled with a 1:1 mixture of organic
mulch and clean sand. To minimize
material and  transportation costs,
               [continued on page 6]
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                                             Solid Waste and
                                             Emergency Response
                                             (5203P)
                                EPA 542-N-06-006
                                November 2006
                                Issue No. 27
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242

Official Business
Penalty for Private Use $300
             Presorted Standard
             Postage and Fees Paid
             EPA
             Permit No. G-35
 [continued from page 5]
 recycled vegetation from the facility was
 selected as the organic mulch instead
 of ground corn (despite slightly higher
 organic   carbon   and    nutrient
 concentrations)  from a local  grain
 elevator.  Due  to  the  short-term
 use  anticipated  for this system, no
 injection piping  was installed during
 construction to  facilitate organic-
 substrate replenishment.

 Costs for installation of the Whiteman
 AFB biobarrier, which involved minimal
 collection of new hydrogeologic data
 and condensed design planning, totaled
 approximately $74,000 (about $275 per
 linear foot or less than $20 per vertical
foot). Despite these budgetary limitations,
nearly two years of monitoring show that
significant CVOC degradation is occurring
within  the  biobarrier  and  CVOC
concentrations in downgradient wells are
88% lower than in upgradient wells.
Sampling  results also show indirect
evidence  of enhanced   reductive
dechlorination in ground water passing
through the barrier, including increased
ferrous iron concentrations and decreased
ORP, dissolved oxygen, and nitrate levels.
Pre- and post-construction gradient
measurements suggest that the biobarrier
has not impacted ground-water flow.

Based on the results of a revised human-
health risk assessment conducted after
biobarrier installation, the Air Force and
Missouri Department  of Natural
Resources determined that potential site
risks were  within acceptable risk
thresholds.  As  a  result, additional
biobarrier monitoring to determine its
longer-term  effectiveness  is  not
anticipated.

Contributed by Mark Craig,  U.S.
Navy/NAVFAC Southeast
(mark, craig&navy. mil or 843-820-
5517), Marvin Eaves,  Whiteman AFB
(marvin.eaves&whiteman.af.mil or
660-687-6263), and Mike Perlmutter,
CH2M HILL (mperlmut&ch2m. com
or 770-604-9095)
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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