1) Groundwater at an industrial site in Portland, Oregon was impacted by TCE and other chlorinated solvents used from 1980-1989. Additional impacts were from historical disposal of manufactured gas plant waste containing naphthalene and other compounds. 2) In situ chemical reduction was used to treat the TCE source area, demonstrating success in removing TCE by 2013. Samples found additional contaminants of interest (COIs) like 1,1,2-trichloroethane in the gas plant waste. 3) The study analyzed data on the COIs to understand their environmental fate and the effectiveness of treatment. Models were used to predict contaminant movement between gas plant waste and groundwater. Degradation

1. Occurrence and Attenuation of Lesser Chlorinated Compounds Associated
with Legacy DNAPL Impacts – Case Study
James Peale (jpeale@maulfoster.com) and Michael Murray
(Maul Foster & Alongi, Inc., Portland, Oregon, USA)
Jim Mueller and Josephine Molin (PeroxyChem, IL, USA)
Abstract: Groundwater at an active manufacturing facility on an 80-acre site in Portland, Oregon
was impacted by TCE and its degradation products. Operations at the facility began in 1980, and
included the use of primarily TCE, and other chlorinated solvents, from approximately 1980 to
1989. TCE and/or TCE-containing wastewater were released to the subsurface in the early 1980s,
roughly between 1980 and 1984. Based upon bench and field pilot studies, ISCR-enhanced
bioremediation was selected for primary source area treatment, implemented in early 2009, with
demonstrated success in 2013. The site is also characterized by extensive impacts related to the
historical (i.e., 1950s) disposal of manufactured gas plant (MGP) waste from an oil gasification
facility. Impacts include significant amounts of MGP DNAPL, primarily composed of
naphthalene, diesel range organics, and polycyclic aromatic hydrocarbons (PAHs). Samples of the
MGP DNAPL collected near the former TCE source area and the ISCR injection zones exhibited
elevated concentrations of not only TCE, but also 1,1,2-trichloroethane (112TCA), 1,1,2-trichloro-
1,2,2-trifluoroethane (Freon 113), dichloromethane (DCM), and 1,2,3-trichloropropane (123TCP)
as constituents of interest (COIs). The presence of these COIs was not expected, raising questions
about the former use and potential release history. More importantly, the presence of high
concentrations of these relatively soluble (aqueous solubility @ 25C of approximately 4,400 mg/L
[112TCA]; 170 mg/L (Freon 113]; 13,000 mg/L [DCM]; and 1,900 mg/L [123TCP]) COIs
adsorbed in NAPL represents a potential long-term source of aqueous phase and vapor phase
impacts.
The objective of this work was to integrate COI data for DNAPL and groundwater into
various transport models in order to help elucidate the site-specific environmental fate and effect
of these compounds and to gain further insight into overall remedial performance. In so doing,
myriad challenges and limitations are recognized, such as: i) uncertainties in COI source(s)
including type, amount and location, ii) compound specific variances in groundwater transport,
iii) differential degradation kinetics, and iv) convoluted and potentially overlapping degradation
pathways.
Analysis and Results. The existing data set from the site is extensive, and includes COI analysis
of groundwater, MGP DNAPL, and soil vapor. The physio/chemical properties of the COIs are
generally understood (Montgomery, 2007), allowing for comparison of groundwater and soil vapor
data. Data from co-located MGP DNAPL and groundwater samples allowed for use of the effective
solubility model (ESM) summarized in Pankow (1996) and described by others (Feenstra, 1992;
Rivett, 2005) to describe and predict desorption of these compounds from the non-aqueous to the
aqueous phase.
Portions of the study area are within the ISCR injection zones where active dechlorination
of TCE is occurring. Groundwater samples taken from upgradient, within, and downgradient of
the ISCR injection zone allowed for evaluation of this technology (intended for TCE and its
degradation products) for the chlorinated alkanes, and prediction of downgradient fate and
transport. Dechlorination or other reaction byproducts of 112TCA, Freon, TCP, and DCM were

2. also detected in samples collected in the study area, and the presentation will identify and rank
potential reaction pathways indicated by the data and site conditions.
Site Description: The site is an operating facility in Portland, Oregon, adjacent to the Willamette
River. Industrial operations at the facility began in 1980, after the site had been developed by
filling during the 1970s. Industrial operations at the facility included the use of TCE from
approximately 1980 to 1989. TCE and/or TCE-containing wastewater were released to the
subsurface, roughly between 1980 and 1984, but the exact date and volumes are unknown. The
releases likely occurred immediately upgradient of the primary manufacturing building, which
covers most of the groundwater plume between the source area and the riverbank (Figure 1).
Groundwater flows from the upland under the river, with a small portion of the impacted plume
intersecting transition zone water and surface water in the river.
Figure 1 Site map and approximate extent of TCE in Groundwater
During the initial technology
screening, a variety of remedial
technologies were evaluated and
eventually discarded due to
incompatibility with facility
operations, or the presence of legacy
MGP-related impacts. The
technology screening identified in
situ chemical reduction (ISCR) as the
most viable DNAPL source removal
technology. Subsequent comparative
bench testing (as described in Peale
et al. 2008) identified the
combination of EHC® and KB-1® as
the best approach for treatment; these
results were supported by subsequent
field pilot testing (Peale et al., 2009),
which in turn supported full scale
implementation.
Implementation: Implementation consisted of an approximately 150 foot long PRB containing
EHC and KB-1, installed at depths ranging from approximately 40 to 112 feet bgs using direct-
push technology. Supplemental injections were completed upgradient of the PRB to treat
additional source areas. EHC was injected first, followed later (usually 7 to 14 days) by KB-1
injections. The EHC was injected at four-foot vertical intervals, with two-foot offsets between
injection rows to enhance the vertical coverage.
Injections commenced in January 2009 and were completed in June 2009 (Cascade Drilling of
Portland, Oregon). Approximately 200 injection points were completed. A subsequent, smaller
injection program upgradient of the first was implemented in 2012 upon discovery of a pool of
MGP DNAPL containing elevated concentrations of TCE and the other source compound
identified above. Performance data were collected from 24 deep and four shallow wells in the
source area, and distant downgradient wells.

3. Data collection included an extensive suite of parameters to identify degradation rates and
pathways. Target analytes included TCE and its degradation products, including ethene, ethane,
and chloride. Secondary analytes that confirmed distribution and/or migration of the injected
materials included iron, total organic carbon, ketones, and Gene-Trac©
analysis for KB-1 bacteria
by SiREM.
Investigation completed to support the EIB implementation identified upgradient areas of TCE
contamination, with elevated concentrations in samples of MGP DNAPL in the shallow fill zone.
DNAPL and groundwater data from the entire monitoring well and reconnaissance database
(collected over 11 years) were used to evaluate the distribution of TCE and its degradation products
(prior to, and during remediation), as summarized below:
DNAPL Samples
Compound Analyses Detections
Detection
Frequency Max (ppb)
GeoMean
(ppb)
TCE 138 111 80% 97,200,000 476,473
cDCE 138 131 95% 16,900,000 618,073
tDCE 138 66 48% 29,400 6,829
11DCE 138 59 43% 29,500 9,702
VC 138 70 51% 847,000 38,158
Groundwater Samples
Compound Analyses Detections
Detection
Frequency Max (ppb)
GeoMean
(ppb)
TCE 2325 1454 63% 602,000 50.39
cDCE 2325 1870 80% 574,000 307.45
tDCE 2325 1212 52% 3,320 23.89
11DCE 2325 1059 46% 1,470 18.12
VC 2325 1792 77% 263,000 64.81
Samples of MGP DNAPL also contained elevated concentrations of 112TCA, Freon, TCP, and
DCM; average and maximum concentrations are summarized in subsequent sections.
For the purpose of this paper, the chlorinated compounds in the table are referred to as
source compounds, as they are all present in the MGP DNAPL samples at significantly elevated
concentrations which would be characteristic of a source zone. The MGP DNAPL is primarily
composed of naphthalene, diesel-range hydrocarbons, and BTEX compounds.
Use of the Effective Solubility Model Data from co-located MGP DNAPL and groundwater
samples allowed for use of the effective solubility model (ESM) summarized in Pankow (1996)
and described by others (Feenstra, 1992; Rivett, 2005) to describe and predict desorption of these
compounds from the non-aqueous to the aqueous phase. The ESM can be used to predict changes
in aqueous phase concentrations of NAPL constituents based on changes in the mole fraction (Xi)
of each compound (i). As both NAPL and aqueous phase data were collected, this evaluation
compared the measured aqueous phase concentrations with ESM-predicted aqueous phase
concentrations.
Csat,i = XiCsat
Where Csat,i is the effective or aqueous solubility of the component (i)
from the mixture; Xi is the mole fraction of component i measured in
NAPL, and Csat is the pure compound solubility in water.

4. Pankow (1996) summarized earlier work that demonstrated that this equation produced
effective solubility values that generally bracketed the range of observed values, but were sensitive
to the assumed molecular weight of the unknown component of the mixture. Pankow also cited
previous work that concluded that the ESM equation works well for predicting aqueous solubilities
of binary mixtures. That ESM approach was previously used (Peale, 2011) to predict changes in
the aqueous phase concentrations of TCE (relative to naphthalene) resulting from increased
concentration gradients due to enhanced degradation rates of dissolved constituents in response to
remediation activities. The effective solubilities (predicted aqueous values) for CVOCs potentially
changing in response to ISCR were similarly calculated in a binary mode compared to relatively
unchanged naphthalene concentrations. These calculations were repeated for Freon, TCP and
112TCA. Calculations were also performed for benzene as a compound not subject to ISCR-
enhanced bioremediation for comparison. Effective solubility values were calculated for the major
components of the DNAPL using the equation above.
Ratio of ESM Predicted Concentrations to Actual
Groundwater Data
TCE 112TCA TCP Freon Benzene
Minimum 2.1 9.9 50.9 1.4 3.0
Maximum 72.0 53.3 19.7 1.4 25.4
Average 15.4 26.6 35.4 -- 9.7
n (paired data) 18 8 2 1 18
Paired data not available for Freon; average concentrations were used.
The data suggest significant overprediction of groundwater concentrations using the ESM for the
chlorinated compounds (except Freon), and less overprediction of groundwater concentrations for
benzene.
Reaction byproducts of 112TCA, Freon, TCP, and DCM The conventional abiotic and biotic
dechlorination pathways for TCE resulting from enhanced ISCR remediation have been
documented at this site (Peale et al. 2009). Dechlorination pathways for two other source
compounds – 112TCA and DCM – have been documented at other sites, but data demonstrating
degradation of Freon 113 and TCP are relatively sparse. As summarize below, however, the data
from this site are in general agreement with the proposed degradation pathways for 112TCA,
DCM, Freon 113, and TCP.
112TCA This source COI was detected in about 10% of the DNAPL samples although no
records or other data are available documenting the use of this compound during site operations.
Reductive dechlorination of 112TCA results in step-wise formation of dichloroethane (DCA)
isomers, chloroethane (CA), and ultimately ethane; as shown in Figure 2, conversion to 1,1-DCE
may also occur via the elimination of chloride in response to abiotic degradation.

5. By looking for the presence of DCA, CA and ethane, evidence supporting the degradation of
112TCA pathway was evaluated using data from the source monitoring well (WS43-36) and
downgradient monitoring wells, as summarized below:
DNAPL Samples
Compound Analyses Detections Detection Frequency Max (ppb)
GeoMean
(ppb)
112TCA 138 14 10% 9,250 5,210
11DCA 138 0 -- -- --
12DCA 138 0 -- -- --
CA 138 0 -- -- --
Groundwater Samples
Compound Analyses Detections Detection Frequency Max (ppb)
GeoMean
(ppb)
112TCA 2325 190 8% 127 5.13
11DCA 2325 101 4% 6.02 0.51
12DCA 2325 105 5% 3.5 1.20
CA 2325 215 9% 82.9 4.92
Figure 2: Transformation
pathways of chlorinated
ethenes and ethanes in
anaerobic conditions.
Tobiszewski et al (2012)

6. 112TCA was detected in 10% of the NAPL samples, with no detection of its degradation products.
The parent compound was detected at approximately the same frequency, albeit at much lower
concentrations, in groundwater downgradient from the source well. Of note, 11DCA (which is not
shown as a pathway in Figure 1) was detected at generally the same frequency and concentrations
as 12DCA. The data show accumulation of CA (byproduct of both 11DCA and 12DCA
dechlorination) in downgradient groundwater samples.
DCM This compound and Freon 113 were the primary ingredients of a product called
Freon-TMC, which was used to dry (dewater) silicon wafers during operations. Stepwise reductive
dechlorination of dichloromethane can generate chloromethane and methane. This pathway was
evaluated using data from the source monitoring well (WS43-36) and downgradient monitoring
wells, as summarized in the following table:
DNAPL Samples
Compound Analyses Detections
Detection
Frequency Max (ppb)
GeoMean
(ppb)
DCM 138 8 6% 55,400 28,503
CM 138 1 1% 2,510
Groundwater Samples
Compound Analyses Detections
Detection
Frequency Max (ppb)
GeoMean
(ppb)
DCM 2325 1 0% 286
CM 2325 67 3% 144 2.55
As noted in the table, downgradient concentrations of DCM were not detected in groundwater,
although CM and methane concentrations were. This may be the result of enhanced dechlorination
of DCM in the aqueous phase, but may also reflect the very high solubility of DCM relative to the
other source compounds. There are also recognized differences in transport of these compounds
in aquifer systems, with significant difference in retardation factor potentially influencing and
complicating data interpretation Methane is also generated at this site by the methanogenic
reducing conditions enhanced by EHC injection, so methane concentrations and mass balances
were not attempted. DCM and CM were not detected in soil vapor samples.
Freon 113 Dechlorination or other degradation reactions have been described in studies
(Balsiger, 2005), but confirmation at hazardous waste sites is not well documented. Balsiger
(2005) describes the formation of degradation products TFE and CTFE, by the pathways shown
below (Figure 3).
None of these “intermediate” compounds
were regularly reported during the course of
performance monitoring. However, tentatively
identified compound (TIC) searches were
performed on groundwater samples and confirmed
their presence. These data indicate that the di-
chloroelimination (d) and hydrogenolysis (h)
pathways are facilitated at the site, likely as a result
of the EHC and/or KB-1 injections. This pathway
was further evaluated using data from the source
monitoring well (WS43-36) and downgradient
monitoring wells, as summarized in the following
table:
Figure 3: Transformation pathways of Freon113 from
Balsiger et al. (2005)

7. DNAPL Samples
Compound Analyses Detections Detection Frequency Max (ppb) GeoMean (ppb)
Freon 113 29 21 72% 207,625 124,476
DCDFM 138 -- -- -- --
CTFE -- -- -- -- --
TFC -- -- -- -- --
Groundwater Samples
Compound Analyses Detections Detection Frequency Max (ppb) GeoMean (ppb)
Freon 113 277 10 4% 177 20.18
DCDFM 2325 88 4% 216 7.78
CTFE 15 (TIC) 5 33% 18.3 3.20
TFE 15 (TIC) 5 33% 12.8 2.80
Along with the parent compound Freon 113, dichlorodifluoromethane and trichlorofluoromethane
were also detected in soil vapor samples and groundwater. These two latter compounds are often
interpreted to be manufacturing impurities, as opposed to degradation products, but they were not
detected in DNAPL analyzed. Hence, there may be multiple NAPL sources or they may indeed be
degradation products of the ISCR treatment.
123TCP No records are available documenting the use of this compound during facility
operations. Tratnyek et al. (2010) have developed extensive research into the degradation of 1,2,3-
TCP. A variety or products and pathways have been identified as shown in the following figure:
Figure 4: Transformation pathways of 123TCP from Tratnyek et al. (2010)
The figure shows that degradation products such as 1,2-dichloropropane (12DCP) are predicted as
a result of reduction reactions. Consistent with mechanics of the ISCR implemented at the site,
12DCP was detected in groundwater downgradient of the source area. However, other products

8. were also identified in groundwater – 2,2-dichloropropane (2,2DCP) and 1,1-dichloropropene
(1,1DCPe) – downgradient of the source area. It is likely that these compounds are manufacturing
contaminants, as opposed to reaction products. Alternatively, these could be byproducts of
coupling reactions.
DNAPL Samples
Compound Analyses Detections Detection Frequency Max (ppb) GeoMean (ppb)
123TCP 138 6 4% 6,210 3,784
12DCP 138 -- -- -- --
22DCP 138 -- -- -- --
11DCPe 138 -- -- -- --
Groundwater Samples
Compound Analyses Detections Detection Frequency Max (ppb) GeoMean (ppb)
123TCP 2325 26 1% 20.4 0.88
12DCP 2325 8 0% 0.97 0.52
22DCP 2325 5 0% 0.39 0.34
11DCPe 2325 7 0% 94.5 0.93
123TCP and the associated compounds were not detected in soil vapor samples.
Summary The data collected during monitoring of legacy DNAPL during ISCR-enhanced EIB of
TCE and its degradation products demonstrated that:
1) TCE released to the subsurface not only sorbed into legacy DNAPL at high
concentrations but was also distributed significantly downgradient. This distribution is
not unexpected, based on historical information regarding use and releases.
2) High concentrations of TCA, Freon 113, DCM, and 123TCP where unexpectedly
identified in the legacy MGP DNAPL, but – for various reasons - these source
compounds did not result in significant distribution downgradient in groundwater.
3) The ESM model overpredicted groundwater concentrations for some of the compounds.
4) Degradation pathways for Freon and 123TCP suggested by others were confirmed.
5) Combined with observation (2), the data support the effectiveness of ISCR enhanced
bioremediation of these chlorinated solvents.
Conclusion Discovery of unexpected chlorinated compounds upgradient of the presumed release
area prompted further evaluation of an extensive data set collected prior to and during monitoring
of groundwater undergoing successful ISCR-enhanced bioremediation. Anticipated degradation
pathways commonly observed at other sites (e.g., for TCE and112TCA) were evaluated based
upon anticipated degradation product concentrations. Degradation pathways for other compounds
(e.g., Freon and 123TCP) which are less commonly observed were also confirmed. The ESM
model was used to compare observed and actual groundwater concentrations downgradient of the
non-aqueous phase source material. ESM calculations generally overpredicted groundwater
concentrations, which along with the presence of degradation products suggests the effectiveness
of ISCR-enhanced bioremediation for unanticipated chlorinated compounds at this site.
Literature Cited

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