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A newsletter about soil, sediment, and ground-water characterization and remediation technologies
Issue 31
This issue of Technology News and Trends (TNT) looks back to find lessons
learned from site characterization and remediation projects described in ear-
lier issues of the newsletter. These site-specific updates encompass expanded
field operations, the results of longer-term monitoring, techniques for system
integration, and recent research on technical focus areas of the U.S. EPA's
Office of Superfund Remediation and Technology Innovation.
ART System Performance Enhanced by Effective Site Assessment
The U.S. EPA's Region 7 office has used
analytical data from small-diameter tree
cores over the past eight years to identify
shallow areas of soil and ground water with
volatile organic compounds (VOCs) at the
Riverfront Superfund site, located along the
Missouri River in New Haven, MO. As an
initial site assessment technique, tree-core
analysis continues to significantly reduce
the extent of analytical sampling (and
associated costs) needed to identify
contaminant source areas at the Riverfront
site and to facilitate cleanup design and
implementation. Success of this simple and
inexpensive tool was demonstrated in
2004 at the site's operable unit 1 (OU1),
where a tetrachloroethene (PCE) plume
and source area in soil were discovered
through tree coring and subsequently
confirmed by traditional soil and ground-
water sample analysis [November 2005
TNT\.
In early 2005, results from the OU1 tree-
coring analysis were used with portable gas-
chrornatograph (GC) analysis of soil
borings to guide placement of an advanced
remediation technology (ART) well for
treating a vadose-zone hotspot adjacent to
the river. An ART well provides the
opportunity for treatment-system
optimization by operating as a combined soil
vapor extraction (SVE)/in-well aeration well
using a single, continuous screen. System
optimization also was achieved by down-
sizing the 5-horsepower (hp) compressor to
a 3-hp unit, while retaining the 3-hp blower
and 0.5-hp well pump originally anticipated
for the ART system. This 2-hp reduction in
the total energy demand resulted in a 25%
reduction in energy costs for system
operation. Monitoring over the past two
years showed a rapid decrease in hotspot
PCE concentrations, suggesting that the
well-defined contaminant characterization
effectively optimized treatment-well
placement and, in turn, will minimize
treatment duration and cost.
The ART system consists of a single 6-in.
diameter, 30-ft.-deep well with a 25-gpm
recirculation pump at the leading edge of the
contaminant plume. A small building 70 feet
away houses a 10 ftVniin air sparging unit
and a 100 ftVmin vacuum blower. A trench
between the well and equipment shed
contains the compressed air and vacuum
return lines and the well pump's power cable.
The system removes contaminated vapor
from both contaminated soil and stripped
[continued on page 2]
July 2007
Contents
ART System
Performance
Enhanced by
Effective Site
Assessment
EPA Compares Three
Soil-Gas Sampling
Systems for Vapor
Intrusion
Investigations
pagel
pages
Activated Carbon
Applied to Sediment
Potentially Reduces
PCB Bioavailability page 4
Research Examines
Phytostabilization at
Mining Sites in Arid
and Semi-Arid
Environments
Multi-Process
Phytoremediation
System Field Tested
on POPs
pageS
page 6
GLU-IN Resources
The U.S. EPA Science Policy
Council formed a cross-
Agency workgroup in 2004 to
examine potential environmental
applications and implications of
nanotechnology. The
workgroup's findings were
published earlier this year in
the EPA Nanotechnology White
Paper (EPA 100/B-07/001),
now available on CLU-IN ditto://
www.clu-in.org/download/
remed/nanotechnoloav
white paper.pdfl.
Recycled/Recyclable
Printed with Soy/Carxsla Ink on paper that
contains at least 53% recycled fiber
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[continued from page 1]
ground water at a rate 100 ftVmin. Water-
table mounding and associated negative
gradients promote subsurface recirculation
of ground water through the soil
formation and the treatment well casing.
As an ongoing partner in large-scale
remediation of the site, the U.S.
Geological Survey (USGS) installed nine
monitoring wells prior to system startup.
An existing residential well at OU1 is
used to monitor the northwest edge of the
plume. Analytical results of ground-water
and vapor sampling in March 2007
indicate that the ART system has removed
more than 1,000 Ibs. of subsurface
contaminants, primarily PCE (Figure 1).
Ground water near the treatment well,
which treats a portion of the total source
area, shows a 98% reduction in PCE
concentrations and a 97% decrease in
concentrations of PCE breakdown
products such as c/s-dicholoroethene. A
monitoring well approximately 100 feet
downgradient of the treatment well (2-3
years travel-time distant) demonstrated
a 63% decrease in PCE concentrations.
Performance evaluation includes
monitoring the system's tolerance to
changes in ground-water and surface-
water levels and the effectiveness of the
selected screened intervals of the wells
(12-44 below ground surface [bgs]). Air
sparge turbulence in the treatment well
casing prevents direct measurement of
water levels in the treatment well. In
addition, ground-water levels below 27
feet stop the ART well pump from
operating, preventing collection of
samples directly from the treatment well.
Consequently, samples are collected
from a deep piezometer. No signs of well
screen clogging have been observed, and
results suggest that treatment rates are
relatively unaffected by changes in water
table elevation. The ART pump portion
of the remedy can operate with ground-
water levels at least as low as 26.8 ft bgs,
although with some reduction in capacity.
Comparison of results from multiple
sampling events suggests that SVE-induced
off-gassing and ground-water fluctuations
likely caused the upward and downward
variability in VOC concentrations displayed
in some deep ground-water samples. Also,
seasonal variations in the river's elevation
and oxygen levels caused variations in
analytical results from downgradient
monitoring wells. One drum of activated
carbon was used to treat system vapor until
analytical sampling confirmed that
emissions were below Missouri air
standards.
Installation costs for the ART well,
associated aboveground equipment, and
monitoring wells totaled approximately
$140,000. Project capital costs are
estimated to be one-tenth of that for
capping and sheet-pile containment of the
source area, the least expensive alternative
remedy.
Semi-annual sampling of the well network
and treatment vapor, as well as annual
sampling of selected locations of the river,
will continue over the next three years. The
remedy's five-year review in 2009 will
include detailed analysis of the impact of
water levels on the ART system's
performance and on monitoring well
results. Ground-water analyses indicate
that 60-95 % of the PCE plume naturally
degrades prior to entry into the Missouri
River; travel time for OU1 ground water
migrating to the river is estimated to be
12-17 years.
A time-critical removal involving in-situ
chemical oxidation recently was initiated
to treat contaminated soil and shallow
ground water at Riverfront's OU4, a
residential area where tree-coring
analysis unexpectedly identified PCE-
contaminated soil. Initial injections of
sodium permanganate were completed in
May, and a second round is scheduled to
occur by early fall. More information on
tree coring as a site characterization and
remediation planning tool is available in
EPA's new User s Guide: Tree Coring to
Examine Subsurface Volatile Organic
Compounds, available on CLU-IN
(www.cluin.org').
Contributed by Jeff Field EPA Region 7
(fieldjeffta)epa.gov or 913-551-7548),
John Schumacher, USGS
(ischu(q)usss.sovor 573-308-3678). and
Robert Blake, Black and Veatch SPC
(blakere(a)bv.com or 913-458-6681)
Ibs
1JDOO
BOO
BOO
400
Cu
Sampling Peiiod
Figure 1. To date, the Riverfront OU1 ART system has
removed approximately 83% of the source-area VOCs.
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EPA Compares Three Soil-Gas Sampling Systems for Vapor Intrusion Investigations
EPA's National Risk Management
Research Laboratory (NRMRL) recently
completed a soil-gas sampling study in a
VOC-contaminated residential area at the
Rayniark Superfund site in Stratford, CT.
The study evaluated equivalence of three
common sampling methods: traditional
dedicated vapor probes, a truck-mounted
direct-push Geoprobe® post-run-tubing
(PRT) system, and the hand-held rotary-
hammer AMS gas vapor probe (GVP) kit.
The Raymark site earlier served as a study
location for various techniques to assess
VOC vapor intrusion into buildings, such
as a combined sub-slab sampling and
indoor air sampling approach (November
2005 TNT).
NRMRL's recent study focused on
expanded use of quantitative data from
direct-push/hammer systems for
assessing potential exposure through
vapor intrusion. Soil-gas samples
traditionally are used for delineating
ground-water and vadose-zone
contamination rather than for evaluating
cleanup actions or establishing cleanup
goals.
Dedicated probes are considered the
most reliable method for soil-gas
sampling due to associated use of a
bentonite layer for isolating a sand-
packed screened interval. Recent
increased use of direct-push/hammer
soil-gas sampling techniques during vapor
intrusion investigations is attributed to a
greater convenience (ability to sample the
same day as probing) and lower cost when
compared to dedicated probe
installations. Direct-push/hammer
techniques also allow collection of soil-
gas samples close to a building,
minimizing concern about interpolation
and extrapolation of soil-gas
concentrations beneath the building. The
PRT system can be used to collect soil
gas samples to depths up to 20 m bgs,
while the hand-held rotary hammer GVP
kit is suitable for soil gas sampling up to
4m bgs.
NRMRL's study was conducted at five
Raymark locations with sand or sand/
gravel of high gas permeability (l.OE-06
cm2). EPA Region 1 provided onsite GC
analysis with VOC detection limits of 2-5
ppbv for each sample. As with all soil gas
sample collection systems, non-analytical
quality assurance/quality control factors
included sampling methods, flow rates,
applied vacuum, purge volume, total
extraction volume, equilibration time,
leakage, and gas permeability. Purging and
sampling of vapor probes were conducted
at a flow rate of 0.5 L/niin.
The study included tests for evaluating
factors potentially affecting sampling
results. To evaluate the impact of pre-
sarnple internal volume exchanges, 10 soil
gas samples were collected after various
internal volume exchanges (starting with
zero) at one PRT and one dedicated vapor
probe sampling location. Using the PRT
system, up to 9 L of air and 74 internal
volume exchanges were extracted with
little impact on vapor concentration. Using
the dedicated vapor probe, up to 103 L (103
internal volume exchanges) were extracted
with little impact on vapor concentration.
The internal volume of the GVP system was
significantly lower than the PRT and
dedicated probe systems.
To evaluate the potential for air extraction
at one location to impact sample results
at a nearby location and depth, three
samples were taken non-sequentially
using each sampling system. For example,
at one location samples were collected by
the PRT system, followed by the GVP
system, and lastly by the dedicated probe.
The sequence then was changed to
sampling first with the GVP system, next
with the dedicated vapor probe, and finally
with the PRT system. This order was
followed until three samples were
obtained from each system at each depth.
Comparison of first and third VOC
concentrations at locations and depths
where three samples were collected
indicated that sample collection at one
location did not impact sample results at
another location.
Another potentially complicating factor
in method comparison was spatial
variability. PRT and GVP sampling
locations were positioned relatively close
(usually within 1 m) to dedicated vapor
[continued on page 4]
1000
100
10 -
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IfTT
/
H-t-l-
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._,_ ,
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Figure 2. Vapor concentrations
measured by the dedicated vapor probe
and PRT systems at three depths show
relatively minor variations.
10 100
Probe Concentration (ppbv)
1000
Error bars represent 1 standard deviation from 3 samples
-------
[continued from page 3]
probes to minimize the effect of spatial
variability on soil-gas concentration. To
assess the presence and extent of spatial
variability at this scale, the PRT system
was used to collect samples at three
depths across five locations separated by
1.5 ft. in a cross pattern. Variation in VOC
concentration with location at each depth
was present but relatively minor.
Sampling systems were compared using
data from all locations and at depths of
approximately 3, 8, and 11 ft. bgs for the
dedicated probes, PRT, and GVP,
respectively. Comparison of VOC
concentrations obtained by each of the
three systems indicated that the methods
provided similar results (Figure 2). At one
location, however, carbon dioxide, oxygen,
and vapor concentrations were noticeably
different, indicating potential leakage in
the GVP system. Use of the PRT system
generally resulted in observation of slightly
higher VOC concentrations compared to
the GVP sampling system and dedicated
vapor probes.
This testing was conducted in highly
permeable soils where the potential for
leakage from direct-push/hammer soil-gas
sampling systems would be expected to be
low compared to less permeable soils such
as silt and clay. As a result, these findings
may not apply to other soil textures
without additional investigations.
Findings also may not apply to other
direct-push/hammer soil-gas sampling
techniques since only one direct-push
and one rotary-hammer method was
compared to dedicated vapor probes. The
full study report (EPA/600/R-06/111) is
available online at http://www.epa.gov/
ada. Region 1 also plans to test methods
for mitigating vapor intrusion at Raymark.
Contributed by Dominic DiGiulio,
NRMRL (digiulio. dommidalepa. gov or
580-436-8605)
Activated Carbon Applied to Sediment Potentially Reduces PGB Bioavailability
Alcoa, Inc., the U.S. EPA, Stanford
University, and the University of Maryland-
Baltimore County (UMBC) are conducting
a joint in-situ pilot study to evaluate use of
activated carbon (AC) for reducing
bioavailability of polychlorinated biphenyls
(PCBs) in river sediment. The study is taking
place along the Grasse River in Massena,
NY, 3.5 miles southeast of the Alcoa
Massena West Plant. Past aluminum-
manufacturing discharges from the facility
resulted in PCB contamination of sediment
and accumulation in the food chain,
including fish. Recent laboratory studies on
sediments from the Grasse River and other
surface waters confirmed that AC
incorporated into surface sediment
effectively reduces PCB bioaccumulation
in benthic organisms, which in turn is
expected to reduce PCB concentrations in
fish over time.
A non-time critical removal action involving
dredging was conducted in 1995. In 2001,
an extensive pilot-scale sediment cap was
installed [September2002 TNT]. As aresult
of partial ice-scouring of the cap and native
sediment and a need for additional data [May
2005 77V7], a remedial options pilot study
was initiated in 2005 to evaluate: dredging
followed by sediment capping in the river's
main channel and near-shore areas; thin-
layer capping of near-shore areas with no
prior dredging; and armored capping of the
main channel with no prior dredging. In
addition, source controls such as land-based
remediation and wastewater treatment
system upgrades at the Alcoa facility now are
reducing PCB levels in both surface
sediment and fish.
AC treatment involved adding black carbon
to the upper, biologically active layer of
sediment (typically the top 3-6 in.) where
PCBs adsorb onto the surface of the carbon
particles. To determine baseline conditions
prior to treatment, surveys of sediment,
aquatic vegetation, and benthic conununities
were performed. In-situ and ex-situ PCB
bioaccumulation tests on caged worms also
were conducted to support future post-
treatment assessment of AC effectiveness.
A 0.5-acre portion of the river was selected
for the AC study area based on its surface
sediment PCB concentrations (4-13 ppm)
and relatively extensive width and shallow
depth (620 and 15 ft, respectively). Selection
of this area allowed continued passage for
recreational users, supplied contiguous fine-
grained sediment deposits with minimal
rock/boulder hindrances, and provided a
relatively uniform river bottom to simplify
AC placement and mixing. Atemporary silt
curtain was installed around the study area
to minimize release of suspended sediment
and AC into the surrounding river channel.
In addition to assessing reductions in PCB
bioavailability, the pilot study is evaluating
methods for in-situ delivery of AC to river
sediment aid determining the extent of PCB
and sediment release to river water during
applications. Delivery/mixing equipment
includes a specially designed roto-tiller
with and without rotating tines (Figure 3)
and a tine sled, both enhanced with nozzles
to inject AC directly into the upper
sediment.
AC placement and mixing was conducted
over six weeks last September through
October. Applications occurred in four
areas: (1) a 50- by 100-ft. initial area where
all three application techniques were
implemented; (2) a 75- by 100-ft. area
where a roto-tiller with rotating tines was
deployed for placement and mixing; (3) a
5 0- by 60-ft. area for placement/mixing by
the tine sled; and (4) a 50- by 50-ft. area
for deploying a roto-tiller without rotating
tines (without mixing). Treatment areas
were separated by buffer zones in which no
AC was applied. In total, the study used a
mass of 18,000 Ibs of AC.
Based on the results of UMBC's site-
specific treatability studies, a derivative of
bituminous coal (Calgon Carbsorb 50 x
200) with a 75- to 300-uni particle size was
selected as the AC. When Carbsorb product
was not readily available, additional AC
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[continued from page 4]
derived from coconut shells (of identical
particle size and similar chemistry as
Carbsorb) was used to complete applications
in the tine sled and unmixed tiller treatment
areas.
Water-quality monitoring during
applications indicated no measurable
changes in water-column PCB
concentrations downstream of the study
area. Downstream turbidity was slightly
higher thai upstreaii but no negative impacts
on water quality were identified. Sediment
cores collected immediately after the
applications were analyzed for AC content
at an offsite laboratory. UMBC is monitoring
the treatment system's overall effectiveness
and refining analytical methods for
distinguishing the site's natural organic
matter from black carbon to measure
achievements in AC dosage.
Stanford University developed PCB mass
transfer and biodynaniic models for
evaluating the treatment system's long-term
effects on sediment. The models describe
PCB uptake by benthic organisms based on
feeding processes and PCB assimilation
efficiencies from water/sediment ingestion.
Analyses of species in the laboratory showed
a 93% reduction of PCB concentrations
when sediment was amended with 2.5%AC
(dry weight), confirming that AC mixing into
the surface sediment effectively reduces PCB
bioaccumulation in benthic organisms.
Physicochemical and biological assessments
over the next two years will evaluate
effectiveness of AC technology in reducing
PCB bioavailability in Grasse River sediment.
Pending the results, a third-year assessment
or large-scale AC application may be
implemented. UMBC and Stanford
University are evaluating this
technology further in a similar pilot
study to remediate PCBs at a tidal
rnudflat of San Francisco Bay.
Contributed by Young Chang, EPA
Region 2 (chane.. voung&epa. sov or
212-637-4253), Larry McShea, Alcoa
(larrv.mcshea(q).alcoa.com or 724-337-
5458), andLeah Evison, EPA OSRTI
(evison. leahuhepa. gov or 703-603-
8753)
Figure 3. Mixing devices for roto-tiller
delivery of AC into Grasse River
sediment were mounted inside an
enclosure to minimize re-suspension of
sediment.
Research Examines Phytostabiliiation at Mining Sites in Arid and Semi-Arid Environments
Technologies such as phytoremediation
continue to show success in immobilizing
metal contaminants and reducing acid rock
drainage at mining sites [March 2006 77V7].
Superfund Basic Research Program (SBRP)
researchers at the University of Arizona
recently conducted field and greenhouse
studies to evaluate phytostabilization at two
semi-arid sites in Arizona. This type of
phytoremediation aims to revegetate barren
sites by replanting native plants capable of
sequestering metals in the root zone without
metal uptake in shoot tissues. Studies
focused on identifying simple, low-cost
revegetation strategies with minimal site
preparation, compost application, or
vegetation maintenance.
One study involved an 18-month field trial
at the 100-acre Boston Mill mine tailings
site adj acent to the San Pedro River. Testing
evaluated growth of the salt- and drought-
tolerant fourwing saltbush (Atriplex
canescens) under the site's neutral pH
conditions, with and without compost
amendment. Study results showed more man
80% of the 40 A triplex transplants survived
regardless of compost treatment. With the
exception of lead, uptake did not exceed
regulatory guidelines for metals (aluminum,
arsenic, cadmium, copper, iron, mercury,
manganese, and zinc). A two-year study
initiated earlier this year on 1.5 nearby acres
uses a native seed mixture including quailbush
as another potentially effective Atriplex
species (lentiformis) for phytostabilization.
Quailbush also was tested under greenhouse
conditions using low- and medium-pH
samples— more typical of mining sites—
collected from lead/zinc tailings of the
Klondyke mine, a state-designated Superfund
site in Arizona's upper Aravaipa Valley. Lead
concentrations at this site exceed 20,000 mg/
kg, and no vegetation remains. Due to wind
and water erosion of tailings, downstream fish
in Aravaipa Creek exhibit elevated levels of
lead and cadmium. The greenhouse tests
evaluated germination, growth, and metal
uptake of plants in tailings amended with 0 -
25% compost (by weight). Results showed
that a tailings amendment of 15% compost
was required for normal plant growth.
Bacterial analysis of tailings afterplant growth
indicated a 4- to 6-fold decrease in the
autotrophic microbial populations
associated with the site's acidic and stressed
soil/plant conditions. Plant shoot tissue
analysis showed little accumulation of
metals.
Results from both sites demonstrate
significant potential for native Atriplex
species to stabilize mine tailings in arid and
semi-arid environments. Current SBRP tests
evaluate effectiveness of other native
species as well as plant-growth promoting
bacteria with potential to minimize the
compost amounts needed for plant
establishment. For details on these and other
SBRP studies, contact Monica Ramirez,
University of Arizona (ramirezfgipharmacv.
arizonaedu).
Editor 's Note: EPA recommends site
evaluation and restoration of soil when
necessary for optimal planting success.
EPA is a proponent of using amendments
such as biosolids to restore soil and
stabilize metal contaminants along with
planting.
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Solid Waste and
Emergency Response
(5203P)
EPA542-N-06-010
July 2007
Issue No. 31
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
Multi-Process Phytoremediation System Field Tested on POPs
Researchers continue to explore
innovative strategies for addressing
environmental contamination caused by
persistent organic pollutants (POPs)
[January 2007 TNT\. Recent studies by the
University of Waterloo demonstrate POP
degradation through a multi-process
phyto-rernediation system (MPPS) based
on accelerated remediation kinetics from
multiple physical and biological
processes. Greenhouse and pilot tests
indicate that the process removes
polycyclic aromatic hydrocarbons, total
petroleum hydrocarbons (TPHs), and
chlorinated hydrocarbons (CHCs) from
soils while stabilizing metals.
The process employs land farming for
aeration, physical volatilization, and
photochemical degradation; microbial
inoculation to begin the contaminant
degradation process; and rapid growth of
plants with plant-growth promoting
rhizobacteria (PGPR) to help partition
POPs and metals out of the soil. Testing
indicates that the PGPR reduces stress-
induced ethene production by microbial
populations and promotes microbial
synthesis of auxin, a significant promoter
of root growth.
MPPS field tests show successful
results: a 60-70% reduction of TPH was
achieved over a two-year treatment period
in soil containing 15% TPH (primarily
heavy fractions) at a site in Sarnia,
Ontario; and a 30% reduction of CHC in
soil was achieved over only three months
at a DDT-contarninated site near Simcoe,
Ontario. Work on this technology is
supported by a collaborative research and
development grant from the Natural
Sciences and Engineering Research
Council of Canada. For details, contact
Bruce Greenberg, University of Waterloo
f greenber@uwaterloo .ca^.
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