TECH TRENDS
Ground Water Currents
A newsletter about soil, sediment, and ground-water characterization and remediation technologies
Issue 3
November 2002
Kansas UST Program Recommends SUE and AS for
MtBE/BTEX Removal
Since the early 1990s, the Kansas
Department of Health & Environment
(KDHE) Storage Tank Program lias worked
aggressively to address dissolved phase
MtBE and BTEX ground-water plumes
associated with releases from underground
storage tanks (USTs). Most of the UST sites
where active remediation is ongoing or
planned utilize soil vapor extraction (SVE)
to enhance biodegradation of MtBE and
BTEX. The approved remediation plans at
many of these sites also include air sparging
(AS). The KDHE lias found mat SVE and
AS are more effective and less cumbersome
technologies than ex-situ ground-water
treatment processes.
More than 200 UST sites involving MtBE
and BTEX contamination currently are
undergoing active remediation using SVE
and AS technologies. Of these, 34% show
a reduction of MtBE concentrations to non-
detect levels, and 25% show a reduction of
benzene concentrations to non-detect levels.
MtBE concentrations have decreased more
than 90% at 65% of the sites, while benzene
concentrations have decreased more than
90% at 66% of the sites.
Enhancement of bioremediation, rather than
direct physical stripping or volatilization, is
the primary focus of the KDHE's remedial
strategy at MtBE/BTEX sites. A combination
of adequate vacuum extraction and relatively
low amounts of injected air (usually less than
5 scfm) has enhanced bioremedation
effectively. At sites where excavation of
MtBE/BTEX-impacted soils is feasible, the
KDHE recommends removal of source
Contents
material as an integral part of any remedial
option. Excavation and backfilling with a
coarse material efficiently enhances airflow
in the unsaturated zone and subsequent
bioremediation in the capillary fringe. The
KDHE also recommends dynamic
implementation of SVE/AS systems, with
design adjustments made as needed.
Successful results were achieved using this
approach at a fonner grain coop in western
Kansas. Following removal of 10 USTs
between 1990 and 1997, investigations
revealed MtBE concentrations of 92,000
ug/L and BTEX concentrations of 55,000
(ig/L in ground water. Operation of a
combined SVE/AS remediation system
began at the coop in September 1998. The
SVE system employs four wells, each with
an applied vacuum of 50-70 in of water
and a total extraction rate of 24-70 scfm.
The system's measured rate of influence
(at 0.1 in of water vacuum) is 55 ft. The
AS system employs nine wells through
which air is injected in pulsed intervals at a
rate of 0.0-2.0 scfm. Site soils consist of
silt at depths of 1-45 ft below ground
surface (bgs) underlain by sands to a depth
of 55 ft bgs. The depth to ground water in
this area fluctuates from 45 to 54 ft bgs.
Although the MtBE plume has expanded
under the natural hydraulic gradient total
concentrations have decreased significantly
(Figure 1). Following approximately four
years of treatment, MtBE concentrations
have decreased 97% and BTEX
[continued on page 2]
Kansas UST Program
Recommends SVE
and AS for MtBE/BTEX
Removal page 1
Biobarrier Treats
Mixed MtBE Plume at
Port Hueneme page 2
Accelerated
BTEX/MtBE Destruction
Achieved through
Chemical Oxidation page 4
Phytoremediation Field
Studies Underway for
MtBE Removal page 5
TIO Develops MtBE
Treatment Profiles page 6
This Issue Highlights.
...demonstrations of a range of
in-situ technologies used to
treat ground water and soil
contaminated with methyl tert-
butyl ether (MtBE). Featured
applications involve soil vapor
extraction, air sparging, a
biobarrier, phytoremediation,
and chemical oxidation at
diverse sites with a wide range
of concentrations of MtBE and
commingled petroleum
products.
Recycled/Recyclable
Printed with Soy/Canola Ink on paper thai
contains a! least 50% recycted fiber
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[continued from page 1]
concentrations have decreased 96% (to
2,100 and 1,942 ug/L, respectively). SVE
system effluent which is monitored on a
constant basis, lias ranged from 2,379 mg/
L at system startup to a current level of 61
mg/L. Nested monitoring wells continue
to track potential migration of the
contaminant plume toward two public
water supply wells (located within 0.25
mi and downgradient of the source area).
No evidence of contamination lias been
found in the supply wells.
The KDHE conducted a complete
engineering evaluation of the remediation
system in September 2002 to identify
potential methods for optimizing and/or
enhancing the existing design. Based on
these findings, no major system
modifications are anticipated until
shutdown in 2004. The total project
implementation cost to date is $74,000,
with a cost of $46,000 expected for
maintenance and monitoring over the next
two years.
Contributed by Greg Hattan, KDHE
(785-296-5931 or
ghattandiikdhe.state.ks. us) and Seth
Kostbar, KDHE (785-296-0642 or
skostbar(3>kdhe.state.ks.us)
Biobarrier Treats Mixed MtBE Plume at Port Hueneme
Figure 1. After nearly four years
of treatment, MtBE concentrations
in ground water have decreased
97% to a maximum level of 2,100
ftg/L
Naval Facilities Engineering Service
Center (NFESC) and Arizona State
University (ASU) researchers are
monitoring the performance of a 500-ft
biobarrier installed in 2000 at the Naval
Base Ventura County (NBVC) in Port
Hueneme, CA. The demonstration
indicates that MtBE, tertiary butyl alcohol
(TEA), and benzene concentrations in
ground water passed through the
biobarrier each decrease by 99%,
achieving less than 0.005 mg/L in
downgradient areas. In recognition, the
National Ground Water Association
granted its 2001 Outstanding Ground
Water Remediation Project Award to this
effort, which is sponsored through the
U.S. Department of Defense's
Environmental Security Technology
Certification Program.
Several pilot-scale technology
demonstrations were conducted recently
at the NBVC to address a large MtBE
plume resulting from past underground
pipeline releases of gasoline. At a depth of
10-20 ft below ground surface (bgs), the
5,000- by 500-ft dissolved MtBE plume
mixes with a smaller BTEX plume and
sands contaminated from residual non-
aqueous phase liquid. Concentrations of
MtBE and total BTEX exiting the source
zone each exceed 10,000 nig/L, while
concentrations of TEA exceed 1,000
mg/L. A lower clay aquitard located 20
ft bgs bounds the aquifer, through which
ground water flows at an average
velocity of 1 ft/day.
Design of the Port Hueneme biobarrier
is based on results from bioaugmentation
and biostimulation pilot-scale studies
conducted during 1998-2001 [described
in the October 2001 issue of Ground
Water Currents, available at www.clu-
in.org]. The system contains a passive
flow-through aerobic barrier through
which ground water containing MtBE
and TEA travels under natural gradient
conditions. Oxygen gas or air is injected
into the aquifer periodically to increase
dissolved oxygen levels, thereby creating
a zone conducive to aerobic
biodegradation (biostimulation). Tailored
bacterial cultures also were injected to
further enhance MtBE degradation
(bioaugmentation).
The biobarrier system includes 252 gas
injection wells, 174 monitoring wells, 25
satellite gas storage tanks, 154 solenoid
valves, a 240 ftVhr-capacity oxygen
generator, automated timer circuits, and
associated piping and electrical lines.
[continued on page 3]
MtBE Concentrations in Ground Water
at Former Grain Coop in Kansas
MtBE (ug/l)
110 to 100
D100 to 1.000
11.000 to 10.000
110,000 to 100,000
•So
.a °-
0 100 200 300 400 500 600 700
relative teet
Initial Concentrations
(October 1998)
MtBE (ug/l)
110 to 100
D100 to 1.000
11.000 to 10.000
I10,000to 100,000
0 100 200 300 400 500 600 700
relative feet
Mid-Treatment Concentrations
(October 2001)
2
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[continued from page 2]
Gas injection wells were installed at 2-ft
spacings with alternating screen depths
of 18-20 ft bgs or 14-15 ft bgs. A modular
barrier, incorporating 20-ft-wide oxygen
delivery modules replicated at 25
positions, spans 500 ft along the
downgradient edge of the source zone.
Since September 2000, oxygen gas lias
been injected four times a day through
each of the 252 injection wells. A central
area of the dissolved plume containing
the highest MtBE and BTEX
concentrations was inoculated with
microbial cultures 85 days after the
oxygeninjections began. Inoculation was
delivered to a depth of 9-20 ft bgs, within
two 70-ft-long sections of the aquifer.
Monthly and bi-monthly sampling events
have occurred since the injections began,
with more than 200 ground-water
samples collected during each event.
Field analyses of MtBE and BTEX
components are performed using gas
chromatography and flame- and photo-
ionization detectors. Due to the
interference of co-eluting peaks in field-
derived histograms, more complete TEA
characterization is achieved using gas
chromatography/mass spectroscopy
techniques at an offsite laboratory.
Figure 2 provides representative contour
plots illustrating pre-treatment and current
concentrations of MtBE in the
demonstration area. Contours of dissolved
BTEX and TEA concentrations show
similar trends. These results indicate that
die biobarrier has reduced migration of
the plume significantly, and lias helped
to degrade contaminants to non-detect
(O.005 mg/L) concentrations in ground
water exiting the system
Dissolved oxygen lias increased from a pre-
injectionconcentrationbelow 1 mg/L to 10-
35 mg/L throughout the target area, thereby
increasing the potential for aerobic
biodegradation to occur. In addition,
increased dissolved oxygen levels upgradient
of the treatment zone due to dispersion of
the injected gas appear to cause upgradient
reductions in MtBE and benzene
concentrations. Peripheral wells showing
no increase in MtBE concentrations
confirm the flow of ground water and
contaminants through, rather than around,
the biobarrier.
Researchers also are investigating the spatial
variability of MtBE-degrading activity
occurring in the demonstration area, and
have filmed two-dimensional visualization
experiments to betterunderstandbacterial
distributions resulting from microbial
inoculation. Performance monitoring of
the biobarrier system will conclude hi
December 2002.
A preliminary cost comparison conducted
with an existing pump and treat system
at this site suggests savings of more than
$34 million over the project life. The Los
Angeles Regional Water Quality Control
Board recently approved continued use
of this biobarrier and installation of a
second biobarrier (at the toe of the plume)
as the final remedy for the NB VC MtBE
plume.
[continued on page 4]
Figure 2. Analysis of ground-water
samples from shallow wells within the
Port Hueneme treatment area indicates
significant containment of the MtBE
plume after 472 days of treatment.
0)
c
Zi
0)
on
MtBE Concentrations Prior to Treatment
| Ground-Water Flow
(mg/L)
-600 -550 -500 -450 -400 -350 -300 -250 -200 -150 -100 -50 0
Feet (Relative to Northern-Most Monitoring Well)
£ 10
o
0)
OL
MtBE Concentrations After 472 Days
CD
-", I CD).
L_ -Q
i- + + O
in
Ground-Water Flow
(mg/L)
-600 -550 -500 -450 -400 -350 -300 -250 -200 -150 -100 -50 0
Feet (Relative to Northern-Most Monitoring Well)
+ Paired shallow/deep monitoring well and gas injection wells
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[continued from page 3]
Contributed by Karen Miller, NFESC
(805-982-1010 or
millerkd&nfesc. navy, mil). Paul
Johnson, ASU (480-965-9115 or
pan I. c.iohnson(a)asu. edu), and Cristin
Bruce, ASU (480-965-8130 or
cridd/ev(d>/iotmail.com)
Reports Indicate...
.. .states cleaned up 64% of the more than 400,000 identified MtBE releases
across the country by October 2001, and have begun cleanup actions at
another 26%. In addition, states need to begin cleanup actions for almost
40,000 more releases or determine that the risks posed by these releases do
not warrant cleanup.
Source: U.S. General Accounting Office, MtBE Contamination From Underground Storage
Tanks, May 21, 2002 (GAO-02-753T)
Accelerated BTEX/MtBE Destruction Achieved through Chemical Oxidation
The Town of Harrison, NY, and private
industry recently collaborated in efforts
to expedite ground-water cleanup at a
municipal site adjacent to property
scheduled for residential development.
Investigations at this West Chester, NY,
site, which formerly housed a public
works garage, discovered BTEX and
MtBE concentrations in ground water
reaching 4,869 ug/L and 451 ug/L,
respectively. Cleanup was challenged
further by the site's steep grades and
underlying bedrock.
Petroleum leaks from an underground
storage tank operating on the 100-acre
property created a 2,400-sq-ft BTEX
plume in the source area and a 17,600-
sq-ft downgradient MtBE plume. The
subsurface consists of very fine to coarse
sand and gravel with occasional cobbles
and an estimated ground-water flow rate
of 0.23 fWday/ft2. The sand and gravel is
underlain by highly weathered and
fractured bedrock at 11-17.5 ft below
ground surface (bgs). The depth to the
water table ranges from 3 to 10 ft bgs.
Following site-specific laboratory studies
that achieved non-detect concentrations
of BTEX and MtBE, the ISOTECSM
modified Fenton's reagent in-situ chemical
oxidation (ISCO) process was selected
as the remedial alternative fortlie site. The
process involves the injection of hydrogen
peroxide and chelated iron catalysts
directly into the subsurface. Together, the
chelated iron catalysts and stabilized
hydrogen peroxide promote generation of
reactive hydroxyl radicals under neutral pH
conditions. The aqueous radicals react with
organic materials to produce non-toxic by-
products such as carbon dioxide and water.
Unlike remediation technologies based on
the conventional Fenton's reaction, the
ISOTEC process does not employ acidic
additives, which hinder the natural
attenuation process. Once equilibrium is
achieved, contaminant concentrations
typically decrease further due to natural
attenuation and other physical processes
occurring within the aquifer. The ISOTEC
process also enhances subsurface mobility
of injected reagents, which is needed for
greater radial coverage of treated areas.
Injections at the West Chester site were
perfonned in two 10-day phases conducted
in June and November 2000. Reagents were
injected into both bedrock plumes, within a
20,000-sq-ft treatment area on hilly terrain.
The first phase involved injection of 1,700
gal of hydrogen peroxide and 760 gal of
catalyst into 23 injection wells, at a rate of
1.64 gal/min. In the second phase, 2,500
gal of hydrogen peroxide and 1,200 gal of
catalyst were injected into 21 wells. In
addition, 76 direct-push points positioned
in a 10-ft grid pattern were used to treat the
contaminated interval, located 11-20 ft bgs.
A total of 2,400 gal of hydrogen peroxide
and 1,300 gal of catalyst was injected at an
average rate of 0.89 gal/minat these points.
Field monitoring activities were
conducted at 12 sampling locations one
month after each of the two injection
events. Project results indicated a 66%
decrease in the total average BTEX
concentration and a 62% decrease in the
total average MtBE concentration (Figure
3). Treatment costs for this project totaled
$150,000, or approximately $20.24/yd3
of contaminated ground water. Costs
were significantly lower than the $1.5-2
million required for implementation of an
alternative (5- to 7-year) pump and treat
system.
Through the use of ISCO with modified
Fenton's reagent, ground-water
contaminants dropped within 13
months. The New York State
Department of Environmental
Conservation subsequently determined
that the site required no further remedial
action, and the adjacent property
development will proceed as planned.
This accelerated cleanup project received
the New York Association of Consulting
Engineers' Diamond Award and the
American Council of Engineering
Companies'NationalRecognitionAward.
Other applications have shown the
ISOTEC process effective in addressing
significantly higher concentrations of
MtBE. [For more information, view EPA/
[continued on page 5]
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[continued from page 4]
TIO's MtBE Treatment Profiles at
www.clu-in.org/products/mtbe].
Additional studies are underway to
evaluate this technology's effectiveness
in removing other recalcitrant volatile
and semivolatile organic compounds, as
well as organic pesticides.
Contributed by Prasad Kakarla, In-
Situ Oxidative Technologies, Inc.
(609-275-8500 or
prasad. kakarla(a).isotec-online. com).
Anthony Catalano, Malcolm Pimie
(914-641-2643 or
acatalano&pirnie. com), and Robert
Wasp, Town of Harrison (914-835-
2000 or dDwwasp&aol. com)
Pre- and Post-Treatment Total Average Results
4,869
5,000
|b 4,000
§ 3,000
-E 2,000
0)
0
o 1,000
o
0
BTEX
Phytoremediation Field Studies Underway for MtBE Removal
University of Iowa and Equilon
Enterprises, Inc. researchers are evalu-
ating the performance of
phytoremediation in treating MtBE-
contaminated ground water at a former
gas stationinHouston, TX. Approximately
1,000 hybrid poplar trees were planted at
the site in February 1998 across a 1.7-
acre treatment area. Current field results
demonstrate that significant MtBE uptake
in the poplar roots lias taken place and
that phytohydraulic containment of the
plume is possible.
Prior to treatment, MtBE concentrations
in the 60- by 300-ft plume at the study
site were approximately 46 mg/L. Using
1-ft-diameter holes to penetrate clay and
reach the sandy aquifer, 6-foot trees were
planted at 8-ft intervals in staggered rows.
Tree whips were placed immediately
above the capillary fringe of the watertable
(at 6-9 ft below ground surface) with 0.5-
1 ft exposed above ground. Backfill
consisted of a fertilizer-amended mixture
of 60% sand and 40% mulch.
By August 1999, the mean height of the
planted poplars was 11.7 ft and the roots
of upgradient trees had reached 14-15 ft
into shallow ground water. MtBE
transpiration was estimated in the field by
placing plexiglass chambers around the
tree branches. Less than 10% of the MtBE
mass proportionately taken up by the trees
was captured in the chambers during 4-
hour incubations, indicating that MtBE
primarily is stored in the plant tissues and/
or metabolized rather than transpired
through leaves. Additional field analysis
indicates non-detect levels of contaminant
potentially released to the air as a result
of transpiration.
Modeling indicates that MtBE
concentrations in the plume should
decrease more than 90% by the end of
next year. Monitoring of the project is
anticipated to extend through 2003. More
information can be found through EPAs
MtBE Treatment Profiles at www.clu-in.
org/products/mtbe.
Contributed by Jerry Schnoor,
University of Iowa/Department of Civil
Engineering (319-335-5649 or e-mail
ierald-schnoor&uiowa.edu)
i Pre-Treatment:
December 1999
i Post-Treatment:
December 2000
451
171
MtBE
Figure 3. A 62% reduction in
MtBE concentrations was
achieved at the West Chester
site following chemical
oxidation.
Contact Us
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f\ v. Technology
X?
News and Trends
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-Q2-005
November 2002
Issue No. 3
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 424-\9
Cincinnati, OH 45242
PRESORTED
FIRST CLASS
US POSTAGE PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
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.
TIO Develops MtBE Treatment Profiles
1 o enhance dissemination of infomiation
on technologies fortreating soil and ground
water contaminated with MtBE, the U.S.
EPA's Technology Innovation Office
(TIO) lias compiled profiles of technology
applications completed or underway at
sites across the country. These treatment
profiles are available on-line in the MtBE
database at www.clu-in.org/products/
mtbe.
The MtBE database currently contains
more than 300 site-specific treatment
profiles submittedfromSO states. Of these,
85 profiles address sites in the State of
Kansas. Other states for which significant
numbers of MtBE treatment profiles are
available include California (60) and South
Carolina (51). Each profile describes a
specific site, design and operation of the
selected technology, project imple-
mentation costs, performance of the
technology, and points of organizational
contact. Pump and treat technology and
in-situ bioremediation account for more
than half of the (non drinking-water
treatment) profiles (Figure 4).
TIO invites technology users to submit new
profiles or update existing profiles directly
online.
To obtain more information or provide
user feedback on the MtBE Treatment
Profiles, contact Linda Fiedler at TIO
(703-603-7194 or fiedler.linda&epa.gov)
Treatment Technologies Commonly Used for MtBE Remediation
Source: MtBE Database (September 2002)
Excavation
6%
In-Situ Chemical Oxidation
7%
Air Sparging
9%
Figure 4. TIO s database indicates
that pump and treat technology is used
most frequently to remediate MtBE-
contaminated ground water.
'Multi-Phase Extraction,
Phytoremediation,
Product Recovery, and
Ex-Situ Bioremediation
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