A newsletter about soil, sediment, and groundwater characterization and remediation technologies
Technology
News & Trends
EPA 542-N-l2-005 | Issue No. 61, October 2012
This issue of Technology News & Trends highlights in situ thermal (1ST) technologies such as electrical
resistance heating, steam enhanced extraction, and thermal conduction heating. These technologies have
been used more often in recent years, primarily to remove non-aqueous phase liquid in contaminant
source areas. Since fiscal year (FY) 2005, 1ST technology has been selected for use at 18 Superfund sites
in addition to numerous RCRA corrective actions, brownfield sites, or military installations needing
accelerated cleanup of highly defined source areas.
Superfund Sites with Proposed, Designed, or
Implemented 1ST Technology
(FY 2005 through FY 2011)
Alaric Area Groundwater Plume, Tampa, Florida
Bridgeport Rental & Oil Services, Bridgeport, New Jersey
Chemical Leaman Tank Lines, Inc., Logan Township, New
Jersey
Cleburn Street Well, Grand Island, Nebraska
Commencement Bay-South Tacoma Channel, Tacoma,
Washington
Former Spellman Engineering, Orlando, Florida
Frontier Fertilizer, Davis, California
Grants Chlorinated Solvents Plume Site, Grants, New Mexico
Groveland Wells, Grove/and, Massachusetts
Memphis Defense Depot, Memphis, Tennessee
NASA Marshall Space Flight Center, Huntsville, Alabama
Omega Chemical Corporation, Whittier, California
Paducah Gaseous Diffusion Plant (U.S. Department of
Energy), Paducah, Kentucky
Pemaco, Maywood, California
Savannah River Site (U.S. Department of Energy), Aiken,
South Carolina
Silresim Chemical Corp., Lowell, Massachusetts
Solvents Recovery Service of New England, Southington,
Connecticut
South Municipal Water Supply Well, Peterborough, New
Hampshire
The increased 1ST applications have brought new lessons learned about effectively combining these
technplogies, handling issues such as water influx or tidal influence, treating the extracted vapors,
optimizing the use of energy needed to operate 1ST equipment, and operating the systems amid ongoing
site activities.
Technology News & Trends
October 2012 Issue
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Combined Technologies: Thermal Conduction Heating and Steam
Enhanced Extraction Removes 99% of Estimated Contaminant Mass
Contributed bv Penny Timmons and Grea Sandlin. Arnold Engineering and Development Complex; Susan
Trussell, U.S. Army Corps of Engineers/Tulsa District
¥$
Tuls
Recent treatment of a contaminant source zone at Arnold Air Force Base, Tennessee, involved thermal
conduction heating (TCH) in a shallow aquifer and steam enhanced extraction (SEE) in an intermediate
aquifer. As part ofa RCRA corrective action for the base's solid waste management unit (SWMU) 10, this
combined technology approach to in situ thermal (1ST) technology was designed to remove large
amounts of dense non-aqueous phase liquid (DNAPL) in multiple water-bearing zones at depths reaching
90 feet below ground surface (bgs) and with strong contrasts in lithology. The approach also was
required to accommodate critical base activities at an adjacent model snop used for ongoing machining
and fabrication of military equipment.
From 1950 to 1972, an estimated 31,000 gallons of chlorinated solvents were reportedly disposed by
infiltration in an unlined leach pit at SWMU 10. The highest identified concentrations of primary
contaminants of concern in groundwater were 135,000 micrograms per liter (ug/L) tetrachloroethene
(PCE) and 8,910 ug/L 1,1,1-trichloroethane (TCA). In the absence of competent confining layers in the
subsurface, contaminants migrated vertically through three aquifers. Permeability in the treatment zone
subsurface differs by at least three orders of magnitude between the shallow and intermediate aquifers.
DNAPL was observed 9ver a half-acre area through pbservations of free-phase DNAPL, hydrophobic dye
tests, and elevated soil and groundwater concentrations approaching the aqueous solubility limit of
150,000 ug/L for PCE. Dissolved-phase contamination extended more than two miles downgradient of
the source area and posed a potential risk to regional groundwater and surface water (Figure 1).
•A
Shallow '
Groumiwalfir
rvlrai^tii-in Wtitt
0.2
1 ^
1.0
1
tj
1
Nl
2.0 4.C
1
n!ermHlifl!fl Rou9h Scale '" Mites trom SWMU 10
Bradley
Leach DlldVCreek
The Barrens
Residential
Well Groundwaler
Discharges at
SpringsWilhin
\ Bradley Creek
0.12 ppb
Figure 1. Regional water potentially affected by PCE DNAPL at SWMU 10 prior to remediation activities.
Technology News & Trends
October 2012 Issue
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Initial corrective actions involved use in 1996 of ex situ low temperature thermal desorptiqn for over
6,000 cubic yards of soil to depths of 16 feet bgs. To treat the intermediate aquifer on an interim basis
and reduce contaminant migration, a groundwater pump and treat system operated from 1996 to 2009.
Steam Injection
Extraction Heater Heater Extraction
Shallow Aquifer
Low Water Yielding
Layered, Silt, Sand, and Clay j
;:;>x;«£AT iOS$
orav.1
BEDROCK
Figure 2. Configuration of each heating and extraction nest at
SWMU 10. '
The target 1ST treatment zone extends from 10 feet bgs to approximately 90 feet bgs, yielding an
estimated treatment volume 9f 66,700 cubic yards. The 85-foot depth of extraction wells was anticipated
to fully transect the deep aquifer and reach the top of underlying bedrock, which would minimize heat
loss laterally through gravel above the bedrock (Figure 2). Preconstruction studies including pump tests
indicated that layered silt, sand, and clay of the shallow aquifer could sufficiently convey heat from the
steam injection and heater wells to the extraction wells. The heat velocity was estimated at 0.05
feet/day within the TCH treatment zone and 7.1 feet/day within the underlying SEE treatment zone.
The combined TCH-SEE treatment approach was designed and optimized through numerical simulation.
The shallow aquifer was heated with 164 heaters installed to depths of 50 to 65 feet bgs. The
intermediate aquifer was heated using 11 steam injection wells completed in the basal gravel/upper
bedrock zone at 90 feet bgs. Forty-two vapor extraction wells and 23 multiphase extraction wells
completed to depths between 45 and 90 feet bgs were located within and surrounding the treatment
zone for hydraulic and pneumatic gradient control during treatment. Alth9ugh steam temperatures were
expected to vary, depending on the amount of pressure that could be delivered to the subsurface, target
temperatures for thermal conductance were set at 250-365°F.
Figure 3. Completed 1ST system covering
approximately 27,400 square feet of industrial
space at Arnold Air Force Base.
Technology News & Trends
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A 1- to 2-inch layer of shotcrete was installed over the entire treatment area to serve as a soil cap that
would minimize water infiltration and retain heat in the treatment systems (Figure 3). The extracted
vapor was treated by thermal oxidation, and extracted groundwater was treated by air stripping and
activated carbon. Resulting vapors were treated by a thermal oxidizer prior to exhaust through an acid
gas scrubber.
To maximize DNAPL removal, TCH was coupled with SEE in the site's western zone containing the
majority of DNAPL at greater depths, while only TCH was implemented in the eastern zone having DNAPL
at shallower depths. Treatment in the eastern zone was deemed complete in December 2010 after seven
months of TCH operation. PCE concentrations in soil and groundwater at that time had dropped to below
the target remediation goals of 150 ug/L for groundwater and 5,000 ug/kg for soil. TCA concentrations
were far below PCE concentrations.
Treatment in the western zone extended over another nine months, until September 2011 when
asymptotic mass removal was encountered. 1ST performance differences in this zone were attributed to
an uncontained influx of shallow water that served as a heat sink causing greater saturation and cooler
temperatures below the soil cap, which together inhibited vapor recovery and increased heat loss from
the treatment system. Thermal imaging confirmed existence of a large zone that was significantly cooler
(86-124°F) than surrounding areas (reaching 209°F). Possible sources of the cooler water included
precipitation, building roof drains, sumps, stormwater conveyance, or subsurface utilities.
In mid 2011, approximately 290 feet of boundary interceptor trenches equipped with extraction sumps or
stormwater bypasses were installed in the western zone to collect the cool, shallow water. Other efforts
to improve system performance involved modifications such as adding a water removal knockout vessel
to the vapor train and boosting discharge capacity of the treated water. Well field enhancements to
target DNAPL hotspots included adding four shallow steam injection wells, one multiphase extraction
weft, and 68 shallow vapor extraction wells; installing 12 additional heaters and replacing 25 heaters;
lifting 15 heaters to the target shallow soil; and covering the treatment zone surface with insulation.
Although target remediation goals (performance metrics) could not be achieved within all portions of the
western zone, the revised goals for groundwater and soil in these areas (1,500 ug/L and 100,000 ug/kg,
respectively) were achieved. Use of the combined TCH-SEE application resulted in removing
approximately 165,000 pounds of PCE (99% of the estimated mass) over 16 months. 1ST
implementation at SWMU 10 cost approximately $10 million. Additional costs for related infrastructure
improvements totaled approximately $350,000, including an estimated $250,000 to extend electricity
service, $50,000 to modify the water system, and $50,OC)0 to clear the area needed for 1ST operation.
Use of thermal remediation technology reduced the duration of groundwater hydraulic containment and
post-thermal polishing requirements at SWMU 10 from hundreds of years to less than a decade,
achieving the Air Force goal of accelerated project closure. Continued post-thermal monitoring and
modeling is underway to evaluate if additional downgradient groundwater remediation is required.
Combined Technologies: ERH and MPE Implementation Accommodates
Major Ground Surface and Subsurface Obstructions
Contributed by Sairam Appaii, U.S. EPA Region 6
In late 2011, an enhanced electrical resistance heating (ERH) system integrated with multiphase
extraction (MPE) began operating at the Grants Chlorinated Solvents Plume Superfund site in Grants,
New Mexico. The treatment area encompassed 30,400 square feet at an active dry cleaner facility
adjacent to residential properties and bisected by a three-lane state highway and a six-inch natural gas
distribution line. Preliminary project results show that 94% and 100% of the estimated total contaminant
mass was rempved from soil and groundwater, respectively, and suggest design or operation approaches
to address onsite infrastructures.
The site's primary contaminant of concern is tetrachloroethene (PCE) resulting from past releases of
chlorinated solvents at an abandoned dry cleaner as well as the existing facility. The site's soil consists
primarily of clay and silty sand with an estimated porosity of 0.28. The depth to groundwater in the
shallow zone is approximately 5-6 feet below ground surface (bgs). Hydraulic conductivity and velocity of
Technology News & Trends 4 of 11 EPA 542-N-12-005 | Issue No. 61
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groundwater in the shallow groundwater zone is estimated at 21-32 feet per day and 69 feet per year,
respectively. Vapor intrusion into buildings above the plume was addressed in 2008 by installing
mitigation systems such as synthetic barriers at 14 homes.
Prior to in ERH-MPE implementation, the highest PCE concentration detected was approximately 50
milligrams per liter (mg/L) in groundwater and 75 milligrams per kilogram (mg/kg) in soil.
Trichloroethene (TCE) andc/s-1,2- dichloroethene (DCE) concentrations in source area groundwater were
2 mg/L and 1 mg/L, respectively, and vinyl chloride was generally below detection limits. Based on soil
data collected during system installation, the original volatile organic compound (VOC) mass estimate of
3,000 pounds was revised to about 1,200 pounds.
The 33,000-cubic-yard target treatment zone was divided into four subareas with different target
treatment depths and positions relative to the natural gas line. The target depths ranged from 25 to 40
feet bgs, based on site investigations before and during remedial design. Prior to construction, removal of
the onsite roadway infrastructure (from ground surface to 10 feet bgs) was required in accordance with
U.S. Department of Transportation regulations. At the active dry cleaning facility, a false floor was
installed to provide a vapor barrier, maintain normal interior temperatures, and allow installation of
upgraded piping and wiring.
Vapors and liquid to extraction
and trealm&nt system
VaporC
High
permeability
sand pack
Inter-phase
SHKhonizaticn
Dialed
Subsurface
Monitoring
Current passes
between
eSeorcdes, heats
the soil and
volatilizes
contaminants
CQCsare
volatilized and
extracted in the
vapour phase
via the VES
system
Bottom baaing
pneumatic pump
Creatoncf
Steam Zone
Figure 1. Conceptual design of enhanced ERH system used at
the Grants Chlorinated Solvents Plume site.
The ERH system (Electro-Thermal Dynamic Stripping Process [ET-DSP™]) comprised 258
eight-inch-diameter and 6.5- to 10-foot-long electrodes installed in 109 vertical and 12 angled soil
borings drilled on 20-foot centers. Depending on the target depth of each subarea, one to three
electrodes were installed in each boring. Electrode spacing was based on the soil's electrical resistivity,
which ranges from 9.3 to 10.8 ohm-meter. To assure full vertical heating, the bottom of the lowest
electrode in each boring was installed near the base of the target treatment depth, and the top of the
uppermost electrode in each boring was completed at 3.5 to 4 feet bgs (Figure 1).
MPE system construction involved installing 64 four-inch-diameter stainless and carbon steel vertical and
angled wells to extract vapor and liquid mobilized by the heating process; the wells were installed to the
bottom of the treatment zone. Each well was equipped with a pneumatic pump or slurper tube,
depending on well depth, to support fluids recovery through screens extending from 4 feet bgs to the
well's bottom. The system also included 27 two-inch-diameter fiberglass wells to extract vapors from the
vadose zone only.
Field adjustments were required throughout construction of both systems to account for the utility
infrastructure; a more robust pre-construction utility survey would have minimized adjustments. Since
all vertical and horizontal components of the systems required burial, construction as well as treatment
operations also would have benefited from more extensive traffic controls to protect onsite workers and
allow more constant traffic flow.
To provide a continuous thermal and vapor cap over the constructed system, a layer of shotcrete was
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October 2012 Issue
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placed above treatment areas not already covered by concrete or asphalt. The power delivery system
(PDS) included two new electrical service units installed on an existing high-voltage distribution network
and two (1,500 kVA and 2,000 kVA) new three-phase transformers. Unit sizes were selected to meet
electricity needs of the extraction/treatment equipment as well as a ventilation system in the dry
cleaning building.
A 400 standard cubic foot per minute (scfm) blower conveyed extracted fluids from the treatment zone to
the treatment system. The air flow rate averaged 1-2 scfm from each shallow vapor recovery well and
8-10 scfm from each deep well. Water was treated through an oil-water separator, air stripper, and two
granular activated carbon (GAG) units operating in series while vapor was treated with GAG only.
Photpionization detector (PID) readings and laboratory analysis of effluent vapors were used throughout
heating to determine the need for replacing GAG in the vapor treatment system. PID data also were used
to determine when vapor or liquid extractipn adjustments were warrantee!, such as increased extraction
rates when higher contaminant concentrations were encountered. The water treatment system required
upgrades during operation to address influent with a solids content higher than anticipated, which caused
persistent scaling.
Active heating began in December 2011. The process was monitored through 295 temperature sensors at
various depths and positions: seven 25-foot strings with 14 sensors, seventeen 40-foot strings with nine
sensors; one 70-foot horizontal string with 24 sensors, and one 60-foot angled string with 20 sensors.
Continuous remote monitoring of temperatures allowed operators (working 24/7) to respond in real time
to subsurface conditions. Operator adjustment of the current between electrodes tp address the soil's
varying electrical and lithological properties was aided by inter-phase synchronization technology. Over
the course of treatment, data on temperatures and other operating parameters were available to the
project team on a dedicated project web page. Monitoring round that portions of the dry cleaning
building's interior experienced temperatures warmer than desired, which could have been minimized by
insulating the false floor.
*'
Date (dd/mm/yy)
Figure 2. Cumulative VOC mass removal over time via vapor phase.
The target temperature pf 92°C (the azeotropic boiling point of PCE) was reached about 90 days after
startup. Operations continued at this temperature for 96 additional days until PCE concentrations in soil
were below the cleanup objective (0.327 mg/kg) at 15 of 18 sampling locations. Similar trends were
found for TCE, while c/s-l,2-DCE concentrations were below the target concentration (180 ug/kg) at all
sampling locations. At system shutdown, VOC mass removed through the vapor stream totaled more
than 900 pounds (Figure 2).
Over 2,550,000 gallons of water were injected into the electrodes during active heating, at an average
rate of 9.73 gallons per minute. The total amount of electricity used to heat the subsurface was 4,821
Megawatt-hours, which was lower than estimated during design-phase soil resistivity testing; the lower
rate was partially attributed to site conditions such as variable conductivity. Costs for implementing the
integrated ERH-MPE system at this Superfund site totaled approximately $7,000,000 ($210 per cubic
yard), including $550,000 for electricity (at $0.11 per kilowatt-hour with fees).
Decommissioning of above-grade portions of the ERH-MPE system was completed over 10 days in July
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2012, and abandonment of wells and removal of below-street components are underway. Complete site
restoration is anticipated in December 2012. The EPA Region 6 office is now evaluating feasibility of using
enhanced reductive dechlorination to treat the residual PCE hotspots and determining the need for
additional vapor intrusion mitigation in any affected buildings.
Combined Technologies: Electro-Thermal Process with Steam Expected
to Reduce Pump and Treat Duration
Contributed by Derrick Golden, U.S. EPA Region 1 and Janet Waldron, Massachusetts Department of
Environmental Protection
From August 2010 to February 2011, the U.S. Environmental Protection Agency (EPA) conducted in situ
thermal (1ST) treatment using the Electro-Thermal Dynamic Stripping Process (ET-DSP™) at the
Groveland Wells Superfund site in Groveland, Massachusetts, to address a trichloroethene (TCE) source
area. The 1ST technology was expected to reduce treatment time of contaminated groundwater by the
existing pump and treat (P&T) system, particularly below the source zone where elevated concentrations
of TCE (up to 96,000 ug/L) had persisted after 11 years of P&T and 10 years of soil vapor extraction
(SVE). After six montns of operation, 1ST treatment removed over 1,300 pounds of volatile organic
compounds (VOCs) and 18 gallons of non-aqueous phase liquid (NAPL), and contributed to a 97%
reduction of TCE concentrations in groundwater.
A 1979 investigation by the Massachusetts Department of Environmental Protection (MassDEP), formerly
the Department of Environmental Quality Engineering, revealed TCE concentrations above drinking water
standards in two municipal water supply welfs. The wells were shut down, and in 1982, the 850-acre
contaminated area was placed on the National Priorities List. The main source of contamination was
determined to be the Valley Manufacturing Products Company where cutting oils, lubricants, and
hydrocarbon solvents were being used for machining and degreasing. Subsurface soil was contaminated
with TCE and other VOCs, including methylene chloride, 1,1,1-trichloroethane, tetrachloroethene, and
cM,2-dichloroethene (1,2-DCE). Analysis of soil gas samples collected from under the plant building
indicated total VOC concentrations as high as 1,300 parts per million. A 350- to 1,000-fopt-wide
groundwater plume consisting primarily of TCE and 1,2-DCE was found to extend approximately 3,900
feet northward from the source area (see Figure 1).
Groundwater
Treatment ,—
Plam *
Former Town
Well
(Permanently
Abandoned)
'~- Former Valley
>(// •' Manufacturing Bldg
bUAl
Figure 1. Location of municipal supply wells (one of the abandoned wells is shown) and extent of
groundwater plume (above 5pg/L) prior to treatment.
D SOD
SCALE IN FEET
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October 2012 Issue
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Groundwater contamination was initially addressed using a P&T system installed in 1987. Air stripping
was used to treat extracted groundwater from 1988-2000, while ultraviolet (UV) oxidation has been used
since 2000. As of April 2012, UV oxidation has treated over 510 million gallons of groundwater and
removed over 1,190 pounds of VOCs.
SVE was used to address source area soil contamination from 1992 until 2002. The system was
permanently shut down in 2002 when the Valley Manufacturing Products Company abandoned the
property. Site investigations conducted by EPA in 2004 indicated that SVE had been largely ineffective
and significant source area contamination remained. Aqueous concentrations of TCE suggestive of dense
non-aqueous phase liquid (DNAPL) were measured.
ET-DSP
Example Process
System
Power Supply
Power Distribution
System Electrodes and
Extraction System
-V
Stacked - -
Electrodes
Knockout
Heat Pof
Exchanger
Treated Vapor to
Atmosphere
Vapor i
Treatment 4-
Jr
' • Blower
Pump"
Mater Treatment
:
Discharge
- Extraction Well
DigiTAM"*" Temperature Sensor
Treatment Area Foot-Print
Figure 2. 1ST Treatment using ET-DSP system design.
The soil overburden consists of heavily stratified loam, sand, clay, sandy gravel, silty sand, and till. A
2006 chemical oxidation pilot test was unsuccessful due to the heterogeneous nature of the soil and
sorption 9f VOCs to the fine-grained component. 1ST treatment was then selected with the expectation
that heating subsurface soil to temperatures near the boiling point of water could mobilize and facilitate
the removal of NAPL. The ET-DSP process chosen involves heating saturated and unsaturated zone soil
by passing an electrical current between underground electrodes; groundwater and saline are
simultaneously circulated past the electrodes to transfer heat by convection. The heat volatilizes the
VOCs trapped in the subsurface, generating soil vapors and steam which are extracted and treated prior
to discharge to the environment. Figure 2 shows the basic design of 1ST treatment
using the ET-DSP
process.
1ST treatment was conducted from 2010 to 2011. The goal was to reduce TCE concentrations in soil and
overburden groundwater to the point of diminishing returns in order to eventually reach the site cleanup
goals of 77 ug/kg for soil and 5 ug/L for groundwater. Treatment depth ranged from the ground surface
to the bedrock, which is approximately 45 feet below ground surface (bgs). Figure 3 provides an
overview of the treatment area.
Technology News & Trends
October 2012 Issue
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Legend:
Pefnawntaid Temporary Ojah Lnk Fencrig
"realment and Eflupment Areas
Vapor Treatment Equipment
N 1. AllbcafansareappiKdmate..
/ 2. Aefial photo used *»i Demission from
; MASS GIS-USGS 2006 30 cm Color Onho.
Figure 3. Aerial view of the thermal treatment area.
The 1ST system was designed to raise the temperature of soil and groundwater to 90°C and 100°C,
respectively. Water and saline were injected to enhance the thermal process. Heat exchangers, a cooling
tower, and a chiller were used to cool extracted vapors. Moisture knockout tanks removedliquids from
the recovered vapors and steam; the vapors were then treated using granular activated carbon prior to
release into the environment. Liquids extracted from the subsurface via pumping were cooled in heat
exchangers, while bag filters were used to remove entrained sand and grit. NAPL was separated using an
oil-water separator, and the recovered water was sent to the onsite groundwater treatment facility. A
vapor cover was installed over the thermal treatment area to prevent rainwater and snowmelt infiltration
and to provide a surface seal for effective vacuum extraction of vaporized contaminants.
Six different types of wells were constructed within the treatment area: 40 standard electrode wells
(10-inch diameter soil boring), 24 mini-electrode wells (6 5/8-inch diameter soil boring) to supply
electrical current beneath the plant building, 29 SVE wells (2-inch steel casing) to recover vapors from
the unsaturated zone 2-12 feet bgs, 15 multi-phase extraction wells (4-inch diameter steel casing with
stainless steel screen to maintain pneumatic and hydraulic control and extract liquid and vapor from the
unsaturated and saturated zones), 16 temperature sensor wells placed in 3-foot depth intervals from the
ground surface to approximately 10-45 feet bgs, and 12 temperature, pressure, and vacuum sensor
wells to monitor subsurface temperatures as well as water pressure and vacuum for hydraulic and
pneumatic control. A total of 143 electrodes were installed within the treatment area, with 1 to 3
electrodes installed in each electrode well, depending on the depth of the treatment zone. After startup,
the system was modified by adding 12 shallow steam injection wells to obtain more heat and ensure the
cleanup goals would be reached.
About 17,450 cubic yards of soil in a 4,830 square-foot area were treated. Forty-two of the 44
confirmation soil samples collected in April 2011 indicated TCE concentrations below the soil cleanup goal.
TCE was detected at concentrations of 5,600 ug/kg (23 to 25 feet bgs) and 7,000 ug/kg (3 to 5 feet bgs)
in two areas of the vadose zone below a paved portion of the site. However, an overall reduction of TCE
concentrations by 65-72% was achieved in these areas.
Technology News & Trends
October 2012 Issue
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Moles
1. Aerial photo provided by ESRI.
2. TCE concentrations shown are
all greater than 5 parts per bil'on.
Extent of TCE Plume Before the 2001 Start
Up of Groundvuter Pump and Treat System
Eatenl of TCE Plume Afler 6 Years of Operating
Groundwater Pump and Treat System
***&
Curent (2011) Extent
of TCE Plume
MILL POND
Fourier Valley Manufacturing
Products Company (VWC) " *•
J .1
\ WASHINGTON! STJ
APPROXIMATE SCALE
0 100 2DO 400
Feet
Figure 4. A 95% reduction in the area of the VOC plume was observed between 2000 and 2011.
Groundwater sampling in April and December 2011 indicated a 97% overall reduction of TCE. TCE
concentrations were below the cleanup goal in 16 of the 19 wells sampled in April and in 19 of the 23
wells sampled in December. The majority of the samples had less than or equal to 1 ug/LTCE. In
addition, the size of the TCE plume has decreased by approximately 95%, from 36 acres in 2000 to 1.8
acres in 2011 (Figure 4). This trend is expected to continue due to significant contaminant reduction by
1ST treatment, continued operation of the P&T system (at 55 gallons per minute), and continued natural
attenuation of contaminated groundwater downgradient of the source area. Additional groundwater
monitoring by MassDEP is planned for fall 2012.
During its 192 days of operation, the 1ST treatment system removed over two million gallons of water
and condensate, 311 million cubic feet of non-condensable vapors, and 1,300 Ibs of VOCs (including over
18 gallons of NAPL). The system used approximately 2,422 kifowatt-hours per day. The overall cost of
1ST treatment is estimated at $6,264,000, with over half dedicated to design, construction, operation and
maintenance, and demobilization. Remaining costs included electricity, field assessments, laboratory
analyses, labor, oversight, and other administrative costs. Per unit treatment cost is estimated at $359
per cubic yard of soil.
CLU-IN Website:
» Thermal Treatment: In Situ: This remediation technology area of CLU-IN provides an overview and
compendium of guidance materials, application reports, and training or other tools for designing, installing, and
monitoring 1ST systems.
» In Situ Thermal Treatment Site Profile Database: The U.S. Environmental Protection Agency (EPA)
Technology Innovation and Field Services Division sponsors this database of site-specific profiles involving 1ST
technologies in past field demonstrations or full-scale applications. The database currently contains 152
profiles.
Green Remediation BMPs: Implementing In Situ Thermal Technologies
The latest in EPA's series of quick-reference fact sheets on best management practices (BMPs) for greener cleanups
focuses on implementing 1ST technologies (EPA 542-F-12-029).The BMPs involve use of processes, equipment, and
analytical tools that can be used to reduce the environmental footprint of applying these technologies, which typically
involves significant rates of energy consumption. Along with strategies to conserve energy, the BMPs address other
core elements of a greener cleanup: reducing air pollutants and greenhouse gas emissions, reducing water use and
negative impacts on water resources, improving materials management and waste reduction efforts, and protecting
ecosystem services.
Technology News & Trends
October 2012 Issue
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Technical Report: In Situ Thermal Treatment of Chlorinated Solvents:
Fundamentals and Field Applications
This report (EPA 542-R-04-010) from the U.S. EPA Office of Superfund Remediation and Technology Innovation
contains information about the use of 1ST technologies to treat chlorinated solvents in source zones containing
free-phase contamination or high concentrations of contaminants that are either sorbed to soil or dissolved in
groundwater in the saturated or unsaturated zone.
Cost & Performance Case Studies: Thermal Treatment (In Situ)
The Federal Remediation Technologies Roundtable maintains a searchable database currently containing 26 case
studies on remediation demonstration projects involving 1ST as the primary technology.
I ;s publishing this newsletter as a means of disseminating useful information regarding innovative and alternative treatment
technologies and techniques. The Agency does not endorse specific technology vendors.
Contact Us
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