United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-00-008
December 2000
Issue No. 38
Ground Water Currants
^ter Treatment
CONTENTS
Biodegradation of TCE
Improved with Lactate
Inject on in Deep,
Fractured Rock Pg. 1
Enhanced In Situ
Bioremediation
Demonstrated in
Fractured Bedrock Pg. 2
Innovative Techniques
Used To Improve Mass
Flux Calculations
in Fractured Bedrock Pg. 3
About this Issue
This issue features proj ects that
address the treatment of ground
water in fractured bedrock.
Two articles involve field-scale
demonstrations of enhanced
bioremediation of ground water
contaminated with TCE. The
third involves the use of the
digital Borehole Image Pro-
cessing System (BIPS) to
enhance characterization of the
bedrock fractures atWatervliet
Arsenal.
BiodegradationofTCE
Improved with Lactate
Injection in Deep,
Fractured Rock
by Kent S. Sorenson, Jr., Idaho
National Engineering and
Environmental Laboratory
Background
After a recent one-year field evalua-
tion, in situ biodegradation enhanced
with the injection of lactate was
selected by U.S. Environmental
Protection Agency's (EPA) Region 10,
Idaho Department of Environmental
Quality, and U.S. Department of
Energy for use in a deep, fractured
rock aquifer at the Idaho National
Engineering and Environmental
Laboratory's (INEEL) Test Area North
(TAN). The enhanced biodegradation
will replace the default pump-and-treat
remedy for the residual source area of
a large trichloroethylene (TCE) plume.
The field evaluation was conducted as
part of an innovative technology
evaluation process specified in the site
Record of Decision. Five innovative
technologies-enhanced in situ biodeg-
radation, in situ chemical oxidation,
metal enhanced reductive dechlorina-
tion, monolithic confinement, and
natural attenuation-were evaluated in
this process. Based on initial evalua-
tion and bench-scale testing, bio-
degradation was selected for evaluation
in the residual source area, where
nonaqueous TCE is present in a sludge
mixture due to the historical injection
of waste into the basalt aquifer.
Field Evaluation
Every week for the first eight months
of the field evaluation, nearly 800 kg
of lactate were injected 200 to 300 feet
below ground surface (bgs) through
the former wastewater injection well to
stimulate biological activity that would
facilitate reductive dechlorination of
TCE. During reductive dechlorina-
tion, TCE is transformed to
1,2-dichloroethylene (DCE), then
vinyl chloride (VC), and finally
ethene, the desired end product. The
process was monitored biweekly at 11
locations within 500 feet of the
injection well.
Results and Conclusions
After eight months of lactate addition,
complete dechlorination was occurring
at all monitoring points from 200 to
400 feet bgs within 100 feet of the
injection well, and ethene was present
in higher concentrations than any of
the chlorinated ethene compounds.
Figure 1 illustrates the results for a
monitoring well located 50 feet cross-
gradient from the injection well. The
results were somewhat slower at this
location than some of the down-
gradient locations, but they illustrate
the strong dependence of the reactions
on electron donor concentrations and
oxidation-reduction conditions.
Transformation of TCE to DCE
occurred at relatively low electron
donor and chemical oxygen demand
(COD) concentrations coincident with
the disappearance of sulfate through
sulfate reduction. Further transforma-
tion of the DCE to VC and ethene
occurred when higher electron donor
[continued on page 2]
Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
contains at least 50% recycled fiber
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Figure 1. The Role
Complete
1600
1200
800
400
_J
0 100 200
Days
of Electron Donor Concentrations and Redox
Reductive Dechlorination of TCE at TAN
4-
T\ 3-
i
2
1-
V
\ /A
y\ //'
.*"••».»** V |^^\i «T-^'L r—
40
30 2~
-20 ,
-10
n A
Conditions in the
. iy >i
ta^ff
, i
0 100 200 0 100 200
Days
ors (mg/L)
Days
Mcis-DCE(umol/L)
f=]trans-DCE (|imol/L)
|VC(|j,mol/L)
^1] Ethene (nmol/L)
[continuedfrom page 1]
concentrations were observed, coinci-
dent with the onset of methanogenesis.
Of particular importance was the
appearance of ethene simultaneously
with VC, indicating that VC would not
accumulate in the system.
Another remarkable observation was
the impact of the operations on the
residual source. The lactate additions
greatly enhanced the bioavailability of
the TCE. This was indicated by the
formation of TCE degradation products
far in excess of the original aqueous
TCE concentrations, and by facilitated
transport of high aqueous TCE concen-
trations that were subsequently
transformed completely to ethene.
INEEL has a patent pending on the in
situ process used at TAN to enhance the
bioavailability of nonaqueous chlori-
nated solvents. The demonstration of
significant impact on the residual
source of TCE opens a wide range of
potential applications for enhanced in
situ biodegradation where its effective-
ness was previously thought to be quite
limited. The success of the project in
the complex fractured basalt aquifer at
TAN may be a milestone both for
fractured rock remediation and for in
situ bioremediation of chlorinated
solvent source areas.
For more information, contact Kent S.
Sorenson (INEEL) at 208-526-9597 or
E-mail SORENKS@inel.gov.
Enhanced In Situ
Bioremediation
Demonstrated in
Fractured Bedrock
Vince Gallardo, U.S.
Environmental Protection Agency,
National Risk Management
Research Laboratory
Introduction
The U.S. EPA's Superfund Innovative
Technology Evaluation (SITE)
Program conducted a demonstration of
the Enhanced In Situ Bioremediation
Process at the ITT Industries Night
Vision Facility in Roanoke, VA. The
biostimulation process, developed by
the U.S. Department of Energy and
licensed to Earth Tech, Inc., involves
injecting a mixture of air, gaseous
phase nutrients, and/or methane into
contaminated ground water to stimulate
and accelerate the growth of existing
microbial populations—especially
methanotrophs. The methanotrophs
produce enzymes that can degrade
chlorinated solvents and their break-
down products.
The ITT facility is an active plant that
produces night vision devices and
related products. Ground water was
contaminated with chlorinated and
non-chlorinated volatile organic com-
pounds (VOCs) due to solvent leaks from
storage tanks. The site is underlain by a
clay-rich overburden atop fractured shale
and limestone bedrock at 5 to 10 feet
below ground surface (bgs). Ground
water is generally encountered at the
overburden-bedrock interface and in the
bedrock fractures. Trichloroethylene
(TCE), 1,1,1-trichloroethane (TCA), and
their breakdown products exceed Federal
Maximum Contaminant Levels.
Design and Implementation
The primary components of the En-
hanced In-Situ Bioremediation Process
system are an injection well, air injection
equipment, monitoring wells, and soil
vapor monitoring points. At the ITT
facility, methane was injected on a pulsed
schedule from March 1998 to July 1999.
The other gases were injected continu-
ously. The radius of influence of the
injection well was 40 feet. Four monitor-
ing wells were within the radius of
influence. One was upgradient, and one
downgradient. In addition, there were
four soil vapor monitoring points. Some
monitoring wells were screened across
the upper and lower zones of the bed-
rock; other wells were screened in either
the upper or the lower zone (10.5 to 30.5
feet and 40 to 50 feet bgs, respectively).
The primary objective of the demonstra-
tion was to evaluate Earth Tech's claim
of a minimum 75 percent reduction in
the concentration of critical analytes in
the zone of influence after six months'
treatment. Four critical analytes were
selected because they exhibited accept-
able temporal and spatial variability:
chloroethane (CA), cis-1,2- dichloro-
ethylene (DCE), 1,1-dichloroethane
(DCA), and vinyl chloride (VC). TCE
did not exhibit acceptable variability.
Baseline concentrations were measured at
each of the four monitoring wells in the
zone of influence for seven consecutive
days; another seven-day sampling event
was conducted 16 months later. The
evaluation period was extended to 16
months due to process optimization and
modifications.
[continued on page 3]
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[continuedfrom page 2]
Results and Conclusions
The results (see Tables 1 and 2) show
that system performance varied with the
depth of contamination. For the lower
zone, treatment did not achieve the
minimum 75 percent reduction for any
of the critical analytes. This is believed
to be due to insufficient oxygen,
nutrient, and methane levels in the
lower zone.
Contaminant reduction in the upper
zone was markedly higher than the
lower zone for all four of the critical
analytes. Fewer samples were taken
from the upper zone and do not repre-
sent a statistically valid sample set but
still are useful in evaluating treatment of
VOCs in fractures in the zone. The
greater reduction in the upper zone
suggests that the air/nutrient/methane
mixture may have migrated towards the
upper zone and effected greater treat-
ment. This would also explain the lower
reduction in the lower zone.
For further information, contact Vince
Gallardo at 513-569-7176 or E-mail
gallardo.vincente@epa.gov.
Innovative Techniques
Used To improve Mass
Flux Calculations in
Fractured Bedrock
by Christopher Gaule, Malcolm
Pirnie, Inc.; Kenneth Goldstein,
Malcolm Pirnie, Inc.; and Grant
Anderson, U.S. Army Corps of
Engineers
Background
Watervliet Arsenal in Watervliet, New
York, is the United States' oldest,
continuously operating, cannon manu-
facturing facility. The 140-acre arsenal
is located on the west bank of the
Hudson River, about four miles south-
southwest of its confluence with the
Mohawk River. The property includes
manufacturing facilities, administrative
offices, a shipping yard, and a storage
area for raw and hazardous materials,
supplies, and finished goods. Ground
water discharges to the Hudson River,
along the eastern property boundary.
Contaminant Distribution
Early in the site investigation, bedrock
monitoring wells ranging from 20 to 80
feet deep were installed at the arsenal
in shallow and intermediate bedrock
flow zones. Ground-water samples were
analyzed for tetrachloroethene (PCE),
trichloroethene (TCE), dichlorethene
(DCE), and vinyl chloride (VC). The
results indicated that volatile organic
compounds (VOCs) had migrated
downward in the bedrock and that
reductive dehalogenation was occur-
ring, as evidenced in the concentrations
of TCE, DCE and VC. Dense non-
aqueous phase liquid (DNAPL) was
detected at a well located near the
Hudson River, which is the regional
ground-water discharge boundary. The
DNAPL was detected 55 to 70 feet
below ground surface (bgs).
Additional monitoring wells were
installed to better define the lateral and
vertical limits of VOC contamination in
bedrock. The locations and target
depths for the new wells were based on
results of conventional borehole
geophysical techniques and video
logging, and the relatively new tech-
nique of enhanced digital Borehole
Image Processing System (BIPS). BIPS
[continued on page 4]
Table 1. Ground-Water Results from Lover Zone
Target
Compound
CA
1,1-DCA
cis-l,2-DCE
VC
Contaminant
Concentration1 (ug/L)
Baseline
180
700
1,300
240
Final
280
500
540
160
Average
Percent
Reduction
-56
29
59
33
Notes:
CA = chloroethane
1,1-DCA = 1,1-dichloroethane
cis- 1 ,2- DCE = cis- 1 ,2- dichloroethylene
VC = vinyl chloride
1 Values are the average of 28 results from the four wells collected over
seven consecutive days and rounded to two significant digits.
Table 2.
Target
Compound
CA
1,1-DCA
cis-l,2-DCE
VC
Ground-Water Results from Upf
Contaminant
Concentration1 (ug/L)
Baseline
460
1,480
6,900
3,000
Final
260
340
360
85
ler Zone
Average
Percent
Reduction
44
77
95
97
Notes:
CA = chloroethane
1,1-DCA = 1,1-dichloroethane
cis- 1,2- DCE = cis- 1,2- dichloroethylene
VC = vinyl chloride
1 Values are the average of eight results from four wells collected over
two separate days and rounded to two significant digits.
3
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[continuedfrom page 3]
collects images of the face of a bore-
hole using a digital camera and
provides real-time, two-dimensional
displays. The use of BIPS allowed for
better characterization of the bedrock
fractures including orientation, aperture
width, and frequency.
Discrete zone sampling of the wells also
was conducted using a packer sampling
installation. This technique allowed
certain fractures to be sampled for
chemical analysis as well as hydraulic
head. A contaminant profile was then
constructed for each well.
Results of the geophysical logging
indicated a primary dip direction to the
east at an average of 100 to 110
degrees. This corresponds to the
primary direction of ground-water flow
in the bedrock. Results of the video log,
fluid resistivity data, and temperature
log of the well with DNAPL indicated
that a single significant fracture, 57 to
60 feet bgs, is the borehole's contami-
nant-bearing fracture. The estimated
fracture aperture is 0.70 mm. Packer
sampling results indicated that the
dissolved phase contamination extends
more than 160 feet below grade at the
eastern property boundary. Contamina-
tion to depths of about 160 feet bgs
may be attributable to smaller fractures.
Subsequent packer sampling and
geophysical logging of additional wells
indicated that there are single fractures
at discrete depth intervals contributing
the majority of flow and contaminants.
Calculation of Mass Flux
to the River
Contaminant mass flux from the
bedrock will be calculated to estimate
potential water quality impacts to the
Hudson River (the discharge point) and
to determine the need for mass flux
reduction. Calculations of mass flux
typically use the total cross-sectional
area of the contaminant zone—which
could be over 160 feet thick at this
site—and the average or highest
concentration detected. Geophysical and
ground-water sampling results revealed
that ground-water flow and the mass
flux are generally confined to single
fractures located at discrete vertical
intervals in the bedrock. As a result, the
contaminant flux from the bedrock
should be estimated from a series of
single fractures, rather than by using
the entire cross-sectional area. Addi-
tional wells will be drilled, sampled,
and logged in order to develop an
accurate estimate of mass flux to the
discharge boundary developed.
Mass flux calculations will be further
refined with pumping test data to
determine the degree of interconnection
and the hydraulic conductivity of the
fractures. For more information,
contact Grant Anderson (U.S. Army
Corps of Engineers) at 410-962-6645
or e-mail Grant.A.Anderson@
nab02.usace.army.mil or Kenneth
Goldstein (Malcom Pirnie) at
914-694-2100, or e-mail
KGoldstein@pirnie.com.
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June 2000
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