I
I
a
/A newsletter about soil, sediment, and groundwater characterization and remediation technologies
Issue 48
This issue of Technology News and Trends provides selected updates on innova-
tive technology applications described in past issues. Some applications moved
toward full-scale implementation at previous study sites while others drew sites
much nearer to cleanup closure.
June 2010
PRB Expanded to Full-Scale Operation for
Accelerating Treatment of Metals
A five-year evaluation of a pilot-scale,
sulfate-reducing permeable reactive
barrier (SR-PRB) installed at the
Stoller Chemical Site in Jericho, SC, in
2004 recently led to installation and
implementation of a full-scale SR-
PRB. [See the February 2006 issue
of TNT for details on the pilot-scale
project.} After completing an updated
feasibility study and record of decision,
the South Carolina Department of
Health and Environmental Control
(SCDHEC) installed the barrier within
a two-month period in early 2009 to
continue treating groundwater metals
of concern.
The SR-PRB was installed immediately
downgradient of an onsite contaminant
source area, in the vicinity of a
groundwater pump and treat (P&T)
system that had operated on an interim
basis since 2002. In 2009, when P&T
operations were terminated and the
system was dissembled to create space
for the barrier, concentrations for
contaminants of concern (COCs) in
source-area groundwater were 22 |ig/L
arsenic, 160 |lg/L chromium, 0.25 mg/L
cadmium, 3.7 mg/L copper, 0.66 mg/L
nickel, 19 mg/L manganese, 25 mg/L zinc,
250 mg/L aluminum, and 69 mg/L iron.
Project designs called for a continuous
V-shaped SR-PRB approximately 380
feet long, 12 feet wide, and 13 feet
deep. The barrier was keyed into an
underlying confining unit at a depth of
13-23 feet below ground surface (bgs).
The groundwater flow rate in this area
is estimated at 0.36 ft/day.
SR-PRB construction involved
sequential framing, excavation, and
filling of 12 individual cells approximately
32 feet long. Due to the occurrence of
flowing sands, each cell was
constructed by installing rigid sheet
piling along the sides of the trench and
attaching the piling to a rectangular
frame of 12-inch steel to prevent inward
collapse. A conventional backhoe was
used to remove approximately 185 yd3
of soil from each braced cell and fill
the trench with sulfate-reducing
amendments. The steel bracing was
then moved to the next cell, where the
process was repeated. Trench spoils
were placed in other areas of the site
for reuse.
Selection of amendment materials was
based on their capability to enhance
growth of sulfate-reducing bacteria that
convert soluble metallic sulfates to
insoluble metallic sulfides, thereby
removing the dissolved metals from
groundwater. The selected amendment
mixture for each cell contained 38%
wood chips, 32% hay and alfalfa, 17%
sawdust with trace amounts of cement
kiln dust, 7% limestone screenings, and
6% cow manure.
[continued on page 2]
Contents
PRB Expanded to
Full-Scale Operation
for Accelerating
Treatment of
Metals page 1
Four-Year
Monitoring Shows
Source-Area VOC
Reductions After
ERH/SVE at Naval
Station-Annapolis page 3
Nearly Five Years
of SER Approaches
Full Treatment of
Source Areas at
Port of Ridgefield page 4
Update on EPA
Remedial
Optimization
Studies page 6
CLU-IN Resources
The new Sediments
contaminant focus area of
CLU-IN provides policy and
guidance, describes con-
ceptual site models, and
discusses the unique
aspects of characterizing
and remediating contami-
nated sediment. Learn
more at: www.clu-in.org/
contaminantfocus.
Recycled/Recycl abl e
Printed with Soy/Canola Ink on paper that
contains at least 50% recycled fiber
-------
[continued from page 1]
The amendments were mixed directly
within each excavated cell in three
separate lifts (Figure 1). Any seepage
water and a few gallons of
groundwater were added to the
mixture to facilitate mixing of each
lift. After the third lift was emplaced,
approximately 100 gallons of
additional contaminated groundwater
from an adjacent well were pumped
into the cell.
The entrenched materials were
allowed to incubate until the oxidation-
reduction potential reached -100 mV
or lower, which typically required two
weeks. Following incubation, the sheet
piling was removed (Figure 2) to allow
flow of contaminated groundwater
through the filled cell and for reuse in
construction of the next cell. A final
cover comprising an impermeable
liner topped by a 24-inch layer of soil
was then installed in each cell and
graded to prevent excessive
infiltration by rainfall.
The completed SR-PRB contained a
total of 672.83 tons of amendments
consisting of 225.28 tons (900 yd3) of
wood chips, 67.27 tons of hay and
alfalfa (3,372 bales), 111.05 tons of
sawdust (397 yd3), 6.73 tons of
cement kiln dust (10 yd3), 195.17 tons
(174 yd3) of limestone, and 67.33 tons
(133 yd3) of manure. By sequencing
and overlapping construction
components for individual cells,
construction of all 12 cells was
completed over 60 days, one month
ahead of schedule.
Detailed water quality monitoring in
March 2010 (approximately one year
after groundwater began flowing
through the entire SR-PRB) indicated
that water in all three downgradient
performance monitoring wells
contained COC concentrations below
the maximum contaminant levels of
0.01 ppm arsenic, 0.005 ppm
cadmium, 0.1 ppm chromium, 0.1
ppm nickel, and 1.3 ppm copper.
Site-specific remedial goals for
aluminum (16.9 ppm), manganese (5
ppm), and zinc (5 ppm) set forth in
the revised record of decision were
met at all three downgradient
monitoring points. The site-specific
goal of 10 ppm for iron was met in
two of the three monitoring points;
at the third, iron concentrations
decreased to 27 ppm.
SCDHEC estimates that the cost of
installing the PRB was equivalent to
the cost of approximately three years
of the former P&T operations. The
system's lifespan is estimated at 15
years, without any need for
replenishment or replacement of the
reactive media.
Two additional SR-PRBs are planned
for the offsite residential area across
the street from the Stoller property
to intercept the downgradient toe of
the contaminated groundwater
plume and prevent discharge of
contamination to the area's
[continued on page 3]
-------
[continued from page 2]
wetlands. Modeling estimates that
the maximum concentration of
cadmium (the primary off site COC)
likely present as a residual solid within
the anticipated barrier would not
exceed the 70 mg/kg residential
screening level for soil.
Contributed by Judy Canova,
SCDHEC ('canovajl(a>,dhec. sc. gov
or 803-896-4046)
Four-Year Monitoring Shows Source-Area VOC Reductions After ERH/SVE at Naval Station-Annapolis
The U.S. Navy applied electrical
resistance heating (ERH) and soil
vapor extraction (SVE) in 2006 as
an interim action to remove 1,1,2,2-
tetrachloroethane (TeCA) and
trichloroethene (TCE) from source
areas at Site 1 of the Naval Support
Activity installation in Annapolis, MD
(former Naval Station-Annapolis)
[see September 2007 TNT]. Analysis
of soil samples collected upon
complete cooling of the subsurface
in January 2009 indicated an
average 99.6% reduction in TeCA
concentrations and 99.9% reduction
in TCE concentrations. Sampling
results since then show concentrations
in soil remain below the corresponding
U.S. EPA industrial standards of
2,900 |o.g/kg and 14,000 |lg/kg. In
groundwater of wells adjacent to the
treatment area, TeCA and TCE
concentrations have decreased an
average 98% and 74%, respectively,
as a result of ERH/SVE application
in the source areas.
Three-phase ERH technology was
implemented at Site 1 by way of steam
stripping and in situ hydrolysis to
convert TeCA to the more volatile
TCE and subsequently remove the
TCE. Integrated ERH/SVE system
components included 24 steel
electrodes, a steam condenser, one
blower, and a granular-activated carbon
filtration (GAC) system. The subsurface
soil was heated to temperatures
averaging 99°C (210°F) over 116 days,
from February to May 2006.
As anticipated, TCE concentrations in
the treatment-area groundwater
monitoring wells significantly increased
immediately after ERH/SVE treatment,
which indicated hydrolysis had
occurred. Concentrations then dropped
to below pre-treatment levels over
following months. For example, one
treatment-area monitoring well with a
TCE concentration of 2,800 |lg/L prior
to treatment exhibited a concentration
of 27,000 |j.g/L five months later,
followed by a concentration below 2,000
Sampling Period
|lg/L in subsequent monitoring events
(Figure 3). The most recent data
collected during biannual sampling of
wells adjacent to the treatment area
show that TeCA and TCE
concentrations have decreased to an
average of 35 |ig/L and 475 |ig/L,
respectively.
Monitoring downgradient of the source
areas indicates that a plume of TCE
was released to groundwater during
heating of the source areas. Four we 11s
located 250-800 feet downgradient
exhibited a peak average increase of
2,060% in volatile organic compound
(VOC) concentrations approximately
two years after system shutdown. All
four wells exhibited a decline of TeCA
and TCE concentrations after the
second-year sampling event, which
suggested that VOC mobilization was
temporary. One well approximately 250
feet downgradient, for example,
showed a 1,200% and 1,100% increase
in TeCA and TCE, respectively, followed
by notably lower concentrations seven
months later (Figure 4).
The Navy continues to monitor VOCs
at Site 1 to evaluate groundwater
concentration trends associated with
this interim action. Groundwater
TeCA monitoring costs since the 2006
TCE [continued on page 4]
Figure 3. TCE concentrations in one
monitoring well at the downgradient
perimeter of the Site 1 treatment area
decreased to 940 [lg/L within four
years of ERH/SVE implementation,
after an initial spike caused by rapid
breakdown of TeCA to TCE.
-------
[continued from page 3]
shutdown have averaged less than
$20,000/year.
Contributed by Ryan Mayer, U.S.
Navy (ryan. mayer(a>,navy. mil or
202-685-3282) and Steven
Kawchak, Shaw Group
(sgkawchak(a>,shawgrp. com or
609-588-6349)
Figure 4. With an an estimated
groundwater flow rate below 1 ft/day,
impacts from Site 1 source-area
ERH/SVE implementation were observed
at one well approximately 21 months later.
TeCA
TCE
^
Sampling Period
Nearly Five Years of SER Approaches Full Treatment of Source Areas at Port of Ridgefield
The Port of Ridgefield (FOR), WA,
recently began the last phase of
steam-enhanced remediation
(SER) at the POR's Lake River
Industrial Site (LRIS). Pilot-scale
SER was conducted in 2004 to treat
soil and groundwater contaminated
by wood-treating waste and to
prevent nonaqueous-phase liquid
(NAPL) from migrating into
environmentally sensitive areas.
The first phase of full-scale operation
was initiated on one acre in 2006 with
plans to sequentially remediate three
additional 1-acre subareas by 2013-
2015 [see September 2007 TNT].
As of December 2009, SER
implementation had removed
approximately 23,900 gallons of
NAPL and fully treated approximately
110 million gallons of groundwater for
surface water discharge.
Approximately 465 tons of sludge
had also been generated through the
liquid treatment system and disposed
at an offsite hazardous waste landfill.
Remediation of the LRIS is
environmentally sensitive due to its
proximity to the Ridgefield National
Wildlife Refuge (including Carty
Lake) and the City of Ridgefield as
well as its position on the banks of
Lake River, a tributary of the Columbia
River. The SER system has focused
on removing mobile contaminants in
shallow groundwater within the 4-acre
NAPL plume, above an aquitard
approximately 50 feet bgs.
Comparison of contaminant concentrations
in system influent collected during the
first three months of treatment with
influent data gathered in late 2009
indicates significant contaminant
reductions: greater than 99.4% for
benzene (originally 50 |lg/L), 97.7%
for pentachlorophenol (PCP)
(originally 7,500 |ig/L), 99.8% for
naphthalene (originally 18,000 |lg/L),
90.6% for tetrachloroethene
(originally 30 |ig/L), and 49% for
arsenic (originally 80 |lg/L). In
addition, dissolved concentrations of
PCP (Figure 5) and all other COCs that
were historically detected in the upper
water-bearing zone beneath Carty
Lake were no longer detected and
plume migration toward Carty Lake
and the Lake River had halted.
Groundwater monitoring shows that
the areal extent of light NAPL has
decreased 90% from the original
estimate of four acres, with no
onsite indication of dense NAPL.
Approximately 85% of this removal
rate is achieved through the onsite
vapor treatment system, which
includes a heat exchanger, air/liquid
separators, air dryers, and two
steam-regenerated GAC units. The
remaining 15% of NAPL is removed
through the liquid treatment system
consisting of another heat
exchanger, oil/water separators,
coagulation/flocculation units, an
inclined clarifier, mixed-media
filtration, and GAC filters.
POR personnel continue to monitor
subsurface temperatures and heat
expansion through use of real-time
data collection equipment such as
digital thermocouples. The rate of
steam injection at each active
injection well is modified as needed
to maintain consistent heating
across the entire treatment zone.
Temperatures of treatment system
influent have averaged 135°F.
During active treatment, which
averages 180 days for each 1-acre
SER phase, a minimum of two staff
[continued on page 5]
-------
--o
---50
---100
---150
PCP Concentrations Prior to Treatment
Fill
Carty Lake Sediments
Lake River
Clay-Silt
Sandy Silt
Sand
SandyGravel
Aquitard
Silt
Grave
Clay
Columbia Basalt
> 0.73 iig/L
>73 ug/L
>730 ug/L
PCP Concentrations After Five Years of Treatment
Figure 5. Three-dimensional kriging models illustrate PCP
concentration reductions of approximately two orders of magnitude
in groundwater at the Port ofRidge field treatment area, primarily
in the shallow water-bearing zone above the aquitard.
---50
---100
---150
Feet bgs
[continued from page 4]
members monitor the system 24
hours per day, seven days per week.
SER implementation difficulties over
the four years of operation have
stemmed primarily from the high
temperatures needed to operate the
system and the corrosive nature of
the heated chemicals. Electrical
meters, groundwater pumps, and
release valves have been subject to
frequent maintenance and
sometimes degraded in as little as
several hours. In particular,
frequent breakdown of mechanical
pumps led to their replacement by
field-modified airlift pumps with
few moving parts.
Operational costs have averaged
approximately $400,000 per month.
Of this, approximately 40% can be
attributed to natural gas that is
consumed at an average rate of 4,900
therms per day. To control the energy
costs, the FOR established a goal of
heat energy input of 500 kWh for
each cubic meter of soil across the
treatment area.
Concentrations of total contaminants
in groundwater influent have
averaged 7.5 mg/L since 2004
startup. Based on this effluent
concentration, the FOR estimates
that the amount of contaminant
removed through SER over four
years was equivalent to the amount
potentially removed by exclusive use
of a P&T system over 140 years.
The FOR plans to operate the SER
system through June 2011, when all
mobile NAPL is expected to be
removed from the source area.
Potential risk associated with
residual, non-mobile contamination
in the treatment zone is currently
under assessment.
Contributed by Brent Grening,
Port of Ridgefield
(bgrening(a>,portridgefield.org
or 360-887-3873) and Alan
Hughes, Maul Foster & Alongi,
Inc. (ahughes(a>,maulfoster. com or
360-433-0217)
-------
Solid Waste and
Emergency Response
(5203P)
EPA 542-N-10-003
June 2010
Issue No. 48
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
Update on EPA Remedial Uptimization Studies
The U.S. EPA's Office of Superfund Remediation and Technology Innovation
completed three additional remediation system evaluations (RSEs) this year
as part of an ongoing initiative to optimize P&T and other remedial systems
financed and managed by Superfund authorities and participating states. The
recent RSEs were conducted at the:
> 10th Street Superfund Site, Operable Unit 2, in Columbus, NE
> Alaric, Inc. Superfund Site in Tampa, FL, and
> Millcreek Dump Superfund Site in Erie County, PA.
Each RSE report provides recommendations on P&T protectiveness, cost-
effectiveness, and potential technical improvements, and outlines options for
gaining site closure and improving sustainability of long-term applications.
Recommendations often involve system modifications to accommodate site
conditions that have changed over time, such as:
> Removing or adding equipment or processes to a treatment train
> Reducing sampling frequency or the numbers of samples collected for long-
term monitoring, and
> Identifying the need for additional study of secondary issues such as vapor
intrusion into onsite or offsite buildings.
To view final reports on RSEs conducted at 45 Superfund sites to date, as well as
additional evaluations completed under regional pilot programs and at RCRA sites
(including those addressing underground storage tanks), visit: www.clu-in.org/RSE.
Contact Us
Technology News and Trends
is on the NET! View, download,
subscribe, and unsubscribe at:
www.epa.gov/superfund/remedvtech
www.cluin.org/products/newsltrsAnandt
Contributions may be submitted to:
JohnQuander
Office of Superfund Remediation
and Technology Innovation
U.S. Environmental Protection Agency
Phone:703-603-7198
guander.iohn@epa.gov
NGWA OffersNAPLTraining
The National Ground Water
Association will hold a three-day
course on Understanding Migration,
Assessment, and Remediation
of Non-Aqueous Phase Liquids, on
August 2-4, 2010, in Boston, MA.
For more information about this
short course, visit the NGWA at:
www.ngwa.org/development.
EPA is publishing this newsletter as a means of disseminating useful information regarding innovative and alternative characterization or treatment
techniques and technologies. The Agency does not endorse specific technology vendors.
------- |