Ground Water Currents: Issue Number 26, December 1997

vs/EPA
United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-97-006
December 1997
www.epa.gov
Issue No. 26
Reotfive Barriers for
"Uranium Removal"
by EdFeltcorn,
U.S. EPA Office of Radiation
and Indoor Air, and
Randy Breeden,
US. EPA Region 8
The U.S. EPA, U.S. Geological Survey
(USGS), U.S. Bureau of Land Manage-
ment, U.S. Department of Energy, and
Utah Department of Environmental
Quality are conducting a joint demonstra-
tion of permeable reactive chemical
barriers at an abandoned uranium upgrader
site in Fry Canyon, UT. Many small active
and abandoned mine and mill sites
throughout the Western U.S. may be
suitable for using the methods demon-
strated at Fry Canyon. Based on success-
ful laboratory demonstration results
showing highly effective removal of
uranium in ground water, full-scale barriers
were installed late this summer. Initial
results collected three weeks after barrier
installation indicate that the barriers are
removing the majority of uranium from the
Trench (filled)
Contaminant
plume
Aquifer
Figure 1. Schematic diagram of a reactive barrier
(Modified from Morrison and Spangler, 1992)
contaminated ground water. These results
are preliminary and may change signifi-
cantly as the reactive barriers age and the
hydrologic system re-equilibrates.

Figure 1 illustrates the schematics of a
typical reactive barrier. Three reactive
chemical barriers were emplaced at Fry
Canyon using simple, inexpensive, and
well-established construction methods.
Installation of the barriers involved initial
excavation of a barrier trench, using a
metal trench box that protected workers
during barrier installation. Reactive
materials were dumped into the gate
structure of each barrier, and monitoring
Reactive Barriers for Uranium Removal !; |i
Diffusion Samplers for Investigating Vt's in Ground Haljfci
.Calendar" ' • . j|j
Enhanced In Situ Anaerobic Bioremediation of Fuel-Contarrjiirj
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Besources • ; \^m
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Neus on Technologies ^ '! ;;|

ports were constructed
prior to backfilling with
' native material. Each of
the three reactive barriers
contains 16 0.25-inch
diameter monitoring points.
and 4 2.0-inch monitoring
points. No-flow barriers
located on both ends of the
reactive gate are con-
structed of bentonite.

Each of the three barriers
consists of different
reactive materials:
Cercona Bone Char Phosphate (PO4),
Cercona Foamed Zero Valent Iron (ZVT)
pellets, and amorphous ferric oxide (AFO).
Four transducers, one water quality
mrnimonitor (measuring temperature, pH,
specific conductance, oxidation reduction
potential, and dissolved oxygen), and a
flow sensor are deployed in each barrier.
Data from the transducers and rninimonitor
are recorded hourly, and flow direction and
velocity are measured monthly. Four
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About this Issue
Recycled/Recyclable
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monitoring points are located downgradient of
Uie barriers in the colluvial aquifer.

Uranium concentrations are monitored hi all
three barriers. Prior to entering die PCM
banier, the contaminated ground water
contains 3,050-3,920 ug/1 dissolved uranium.
After traveling 2.0 feet along flowpath 1
into the reactive barrier, the uranium
concentration is reduced to 10 ug/1. Prior to
entering Uw ZVI barrier, contaminated ground
water contains 1,510-8,550 ug/1 dissolved
uranium. After traveling 0.5 feet into the
reactive barrier, the uranium concentration is
reduced to below the analytical reporting limit
of 0.06 ug/1. Prior to entering the AFO barrier,
contaminated ground water contains 14,900-
17,600 ug/1 dissolved uranium. After traveling
2,0 feet into the reactive banier, the uranium
concentration is reduced to less than 500 ug/1.
aj.oao
y
| 15.000
I 10.000
| 5,000
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AFO REACTIVE
BARRIER MATERIAL
i 1 i i
•-••• FLOW PATH 1 |-
-•- FLOW PATH 2 J.

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-
t 1

M -02 0.0 Oa 0.4 0.6 0.8 1.0 1.2 1.4
Figure 2. Cross section distance, In meters
Uranium concentration reductions hi
flowpalhs 1 and 2 of the AFO barrier, which
are of the same design but on opposite sides
of the barrier, are illustrated in Figure 2.

During the next 10 months, study team
members will monitor the permeable reactive
chemical barriers for numerous water-quality
constituents, including pH, specific conduc-
tance, dissolved oxygen, oxidation reduction
potential, uranium, iron, phosphate, and major
ions. For more information, contact Ed
Feltcorn (U.S. EPA, Office of Radiation and
Indoor Air) at 202-564-9422. Other EPA
staff members contributing to this project
include Ron Wilhelm (Office of Radiation
and Indoor Air) and Paula Estornell (Office
of Emergency and Remedial Response).

Diffusion Samplers for Investigating VOC's

in Ground Hoter

by Don A. Vroblesky,
U. S. Geological Survey
U.S. Geological Survey (USGS) studies at a
gas-turbine manufacturing facility in
Greenville, SC, have shown the effectiveness
of a simple, inexpensive
diffusion sampler for
delineating areas where
contaminated ground
water is discharging to
surface water, and for
obtaining water samples
from wells. This
technology provides an
advantage over
traditional methods for
obtaining well samples
because purging, which
increases project costs
and potentially
confounds analytical results, sometimes is not
required for collection of representative water
samples.

The diffusion sampler consists of water or air
inside a polyethylene membrane. A scalable
sandwich bag obtained at a local groceiy store
can serve as a simple sampler. Earlier studies
performed at the Aberdeen Proving Ground,
m f Mtimst'K, S-J.-. amtSpaitgfer, /?.«:. 1992, Cliemiail Barriers/or Controlling Gmundwater Contamination:
Mtmr l&pagft 175-ISI,
MD, showed that the sampler is based on the
ability of polyethylene to readily allow
diffusion of volatile organic compounds
(VOC's), such as aromatic petroleum
hydrocarbons and chlorinated solvents, while
preventing the movement of water across the
membrane. Accordingly, after sufficient
equilibration time, VOC concentrations of air
or water in the sampler achieve equilibrium
with VOC concentrations in the ambient water
outside of the sampler. Recovery of the
samplers and analysis of the contained air or
water are used to determine VOC concentra-
tions. Vapor-based sampler analysis, which
can be performed rapidly and inexpensively
~ ohTieldoflaBoratoly gas chromatographs,
yields relative VOC concentrations. Water-
based sampler analysis provides the advantage
of quantifying specific VOC concentrations
through standard laboratory methods.

One project study at the Greenville site
showed that samplers were capable of
determining the locations of bedrock fractures
that were discharging contaminated ground
water to surface water. The project involved
installation of diffusion samplers in the bottom
sediment of a stream to intercept discharging
ground water prior to entry into the stream.
Diffusion samplers consisted of air-filled, 40-ml
glass vials enclosed in scalable polyethylene
bags. Concentrations of total VOC's in the
samplers ranged from less than 5 ppm (as
vapor) in reaches of the stream outside of the
contamination plume to greater than 900 ppm
(as vapor) hi a suspected fracture zone.

Periodic analysis of diffusion samplers was
useful in analyzing increases in contaminant
discharge resulting from air-rotary drilling of a
nearby well in a fractured-rock aquifer. VOC
vapor concentrations increased from approxi-
mately 1,000 ppm prior to well installation to
greater than 10,000 ppm following well
installation. As the well began pumping and
Remediation by Natural Attenuation; January 26-28,1998; J.F. Friedrick Center, University of Wisconsin,
Madison, WI; 800-462-0876.

Subsurface Barrier Technologies; January 26-27,1998; Weston La Palma, Tucson, AZ; 508-481-6400 ext.
451, e-mail reg@ibcusa.com, or the World Wide Web site http://www.ibcusa.com/coniybarrier.

Eighth Annual West Coast Conference, Contaminated Soils and Ground Water; March 8-12,1998;
Embassy Suites Hotel, Oxnard, CA; 413-549-5170, e-mail bknowles @ aehs.com, or the World Wide Web
site http://www.aehs.com.
Lntng ol conference, seminars,or events in this section does not necessarily constiiute endorsement by the U.S. EPA.

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removing contaminated ground water,
diffusion samplers indicated that VOC vapor
concentrations beneath the stream decreased
from greater than 10,000 ppm to less than 1
ppm. This reduction in VOC concentrations
indicated that well pumpage had captured the
discharging contamination.

A second Greenville site study indicated that
diffusion samplers also can provide represen-
tative water samples for chlorinated VOC's
from observation wells. Samplers consisted of
polyethylene bags containing deionized water
placed adjacent to the water-bearing fracture
or screened interval in a well. In saprolite and
fractured-rock wells, VOC concentrations in-
water samples obtained using the samplers
without prior purging were similar to concen-
trations in water samples obtained from the
respective wells using traditional purging and
sampling approaches (such as a submersible
electric pump, a bladder pump, and a bailer).
For example, the trichloroethene (TCE)
concentration obtained after purging with a
submersible electric pump was 146 ug/1. TCE
concentrations in down-hole diffusion
samplers prior to purging ranged from 145 to
163 ug/1, indicating that the two sampling
methods produced comparable results.
Similar findings were obtained from other
wells over a range of concentrations from
undetectable to greater than 2,000 ug/1. The
low cost associated with this approach
(typically less than $10 per sampler) makes it
a viable option for monitoring large networks
of observation wells. For more information,
contact Don Vroblesky (U.S. Geological
Survey) at 803-750-6100.

Enhanced In Situ flnaerobic

BioremediotionofFuel-Contominoted

Ground Water

by Martin Reinhard, Ph.D.,
Stanford University
A team of investigators from Stanford
University and the Naval Facilities
Engineering Service Center is demonstrat-
ing the feasibility and cost effectiveness of
enhancing natural bioremediation of fuel-
contaminated sites. The test site is located at
the Naval Weapons Station, Seal Beach, CA,
under sponsorship by the U.S. Department
of Defense (DOD)  Environmental Security
Technology Certification Program.
Enhancing natural (or intrinsic) bioremedia-
tion utilizes naturally-occurring anaerobic
microorganisms that transform hydrocarbon
contaminants under nitrate- and sulfate-
reducing and methanogenic conditions. The
target compounds are benzene, toluene,
ethylbenzene, o-, m-, and p-xylene (the
BTEX compounds). These compounds are
regulated and have low maximum contami-
nant limits in drinking water. Enhancing
natural bioremediation involves amending
the ground water with nitrate and/or sulfate
as electron acceptors and removal of
inhibitory compounds. "Push-pull" tests
conducted at the Seal Beach test site have
indicated that BTEX (ransformation under
the naturally existing conditions is extremely
slow.  (Push-pull tests are in situ reactivity
tests whereby slugs of groundwater
(approximately 1,000 liters) containing a
tracer, nutrient, and BTEX compounds are
released into a test zone. Water from the
test zone subsequently is analyzed, and
contaminant transformation rates are
inferred from the concentration versus time
and tracer response. Modifications to the
composition of the injection water allow
for different geochemical conditions to be
evaluated). By amending electron acceptors
to the contaminated zone, BTEX transfor-
mation rates were significantly enhanced.

Enhancement of natural bioremediation
provides several benefits.  In situ processes
are preferred over pump-and-treat tech-
nologies that produce secondary waste
streams  and are limited by slow mass
     News on Technologies

Bi-weekly updates of the Technology
Innovation News Survey contain market/
commercialization information; reports on
demonstrations, feasibility studies, and
research; and other news of interest to the
hazardous waste community. Each update
summarizes articles of potential interest to
technology development stakeholders who
may not have enough time to read the
numerous news publications that are
available. Bi-weekly reports are available
on the U.S. EPA Technology Innovation
Office's CLU-IN World Wide Web site.

         http://clu-in.com
   Innovations in Ground
   Water and Soil Cleanup:
   From Concept to
   Commercialization
   This report published by
   the National Research
   Council provides an up-to-date
   review of the capabilities and
   limitations of existing ground
   water and soil cleanup technologies.
   The report also recommends solutions
   to institutional problems and other
   factors that have stifled innovation in
	Jhe ground water and soil cleanup ._,	
   industry [June 1997,265  pages].
   Prepublication hard copies are
   available from National Academy
   Press for $45 plus $4 shipping/
   handling. Contact 800-624-6242 or
   202-334-3313. When the report is
   published in October,
   it will be downloadable from
   http://www.nap.edu.
transfer. Cleanup is accelerated and process
costs for long-term monitoring and site
maintenance may be lowered significantly.
Complications associated with the addition
of poorly water-soluble oxygen or oxygen-
releasing compounds can be avoided by
using anaerobic bioremediation processes
instead of aerobic ones. Nitrate and sulfate
are much more water soluble than oxygen
and, therefore, can be added in high
concentrations. Anaerobic processes are
less likely to produce pore-clogging
biomass and, therefore, are easier to control.

In the ongoing demonstration, three test
zones that allow for the parallel evaluation of
three different treatment regimes have been
established. Each test zone is equipped with
five multi-level observation points (seven
levels) that provide samples for a three-
dimensional evaluation of the contaminant
plume. Contaminant behavior is monitored
using an on-site automated sampling  and
analysis platform that draws samples from
105 different observation points. Ground
water is extracted from a common extraction
well, treated and amended according  to
specifications, and then re-injected into the
ground. Injected ground water is amended
with BTEX compounds for verifying
contaminant removal. Treated ground water

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Address correspondence to:
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containing nitrate and sulfate combined, and
sulfate alone, is injected into two separate test
zones. The third test zone is amended with
treated ground water that contains bicarbon-
ate as the only electron acceptor.

Preliminary data indicate the establishment
of nitrate- and sulfate-reducing and
mcthanogcnic conditions in the three
different plumes and BTEX removal. Study
data are used to evaluate mass balances,
removal rates, rate-limiting factors, and
transformation intermediates. This informa-
tion will be useful for developing protocols
to optimize in situ bioremediation approaches
and monitor the progress of site cleanup.

U.S. EPA estimates that approximately
300,000 fuel-contaminated sites exist across
the nation. DOD alone has over 2,700 sites
with contaminated ground water from
underground storage tanks. Compared to
conventional pump-and-treat technology
with activated carbon treatment, enhanced
intrinsic bioremediation is estimated to cost
one-third as much, resulting in a $100 million
savings for cleanup of these DOD sites.
For more information, contact Martin
Reinhard, Ph.D. (Stanford University) at
650-723-0308 or e-mail
Reinhard@CE.Stanford.edu, or Carmen
Lebron (Naval Facilities Engineering
Service Center) at 805-982-1616 or e-mail
clebron@nfesc.navy.mil.
United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-97-006
December 1997
www.epa.gov
Issue No. 26
vvEPA Ground Water Currants
Developments in innovative ground water treatment

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