-------
area was abandoned in place. During tank removal, fuel remaining in the storage tank is believed
to have discharged to the subsurface through the buried pipe.
PHYSICAL SETTING
The regional hydrogeology of the Westover ARB area consists of three major hydrogeologic
units. An aquitard composed of lacustrine deposits and glacial till separates a shallow deltaic
outwash aquifer from an underlying Triassic bedrock aquifer. Both aquifers are used to a limited
extent for industrial, municipal, and domestic purposes. Base-wide hydraulic conductivities in the
shallow aquifer average 13 feet per day (ft/day) and range from 2.2 to 33 ft/day. Depth to ground
water is approximately 5 to 7 feet below ground surface (bgs) across the majority of the site.
Across the northern and western portions of the site, ground water flow is to the southeast with
an average gradient of 0.0018 foot per foot (ft/ft). An apparent convergent ground water divide,
shown on Figure 1, is present just south of the main burn pit.
The convergent ground water divide appears to result from two interacting hydrogeologic
conditions. The hydraulic conductivity data suggest that alluvial sand and gravel with a higher
permeability than surrounding sediments is present in the vicinity of the convergent divide. Of the
five hydraulic conductivities estimated for shallow ground water at the site, the two highest were
measured at wells within and at the head of the convergent divide. The convergent divide is also
thought to result from the interaction between regional and local ground water flow patterns. A
southeastern regional flow direction has been observed for the northern portion of the base. This
flow pattern is present over the northern and central portions of the site, in areas characterized by
a general lack of topographic relief. The land surface rises to the west and south of the site. The
ground water contour map (Figure 1) suggests that ground water from these topographically
higher areas is flowing north and east into the topographically lower area of the site. The
interaction of the southeastern and northeastern flows contribute to emphasize the preferential
ground water flow through the zone of elevated hydraulic conductivity that trends to the east
through the site.
Evidence suggests that vertical flow gradients within the shallow aquifer vary across the site.
Three monitoring well clusters included shallow wells screened across the water table and deep
wells screened at least 70 feet below the water table. Vertical gradients were computed at 0.024
ft/ft (downward) between wells CF-1 and CF-1A and 0.0043 ft/ft (upward) between CF-6 and
CF-6A. The estimated vertical gradient was negligible between CF-2 and CF-2A. Dissolved
contaminant concentrations suggest significant horizontal ground water movement through
aquifer intervals from 5 to 15 feet bgs and 30 to 50 feet bgs. Given the migration of BTEX
compounds to 30 to 50 feet bgs, a significant downward vertical gradient is believed to exist in
the upper half of the surficial aquifer in the vicinity of the source area.
DISTRIBUTION AND EXTENT OF GROUND WATER CONTAMINATION
Historically, BTEX compounds have been detected to a maximum depth of 15 feet bgs in soil
samples from the burn pit area, with the highest concentrations detected in soil from the vadose
zone. In 1995, the maximum detected soil BTEX concentration was 440 milligrams per kilogram
(ma/kg). With the exception of a soil sample at the outfall of the buried waste fuel pipe, soil
samples collected outside of the burn area have not contained quantifiable levels of BTEX. CAHs
have not been detected above detection limits in any soil samples.
-------
The areal distribution of total dissolved BTEX and CAHs in ground water for July 1996 is
presented on Figures 2 and 3. The main body of the plume is centered beneath the main burn pit
with a secondary source located at the outfall of the abandoned and buried waste-fuel pipeline.
The vertical extent of BTEX along the main axis of the plume parallel to the direction of ground
water flow in 1995 and 1996 is presented on Figure 4. Vertically, the BTEX plume is split into
two lobes separated by a silty sand unit with relatively low hydraulic conductivity.
The maximum observed total BTEX concentration in 1995 was 32,557 micrograms per liter
(ug/L), detected in a ground water sample from monitoring point MP-4S. In 1996, the maximum
BTEX concentration at the same location decreased to 26,125 jag/L. In 1995, the BTEX
concentrations from the three shallow monitoring locations directly downgradient of MP-4S (i.e.,
MP-12S, CF-3, and CF-2A) had BTEX concentrations of 25,012, 6,266, and 3,020 ug/L,
respectively. Samples collected from the same wells during July 1996 contained BTEX
concentrations of 21,210, 4,047, and 2,006 u,g/L, respectively.
The low horizontal ground water gradient at the site reduces the horizontal ground water
velocity, and therefore BTEX compounds migrate or disperse in ground water both horizontally
and vertically. The maximum detected 1995 BTEX concentration in the deeper saturated zone
was 1,652 u.g/L, in a sample from location MP-14D. In 1996, this concentration decreased to
1,254 ug/L. The intermediate-depth sample at the same location (MP-14M) contained dissolved
BTEX concentrations of 324 ug/L in 1995 and 173 ug/L in 1996. The hydraulic conductivity of
the silty sands in the intermediate zone is lower than that of the coarse sands of the deeper zone.
The fact that the total BTEX concentration is higher in the deeper zone of the aquifer suggests
that most of the contamination found in the deep zone migrates vertically through the silty sand
upgradient of the CF-2/MP-14 cluster. The contamination then resumes a more horizontal flow
path in the coarse sands of the deeper zone.
The May 1995 and July 1996 vertical distribution of CAHs along the axis of the plume parallel
to the direction of ground water flow is presented on Figure 5. Vertical migration dominates in
the chlorinated solvent plume. The maximum observed 1995 total chlorinated solvent
concentration of 13,541 jag/L was detected in shallow ground water near the suspected CAH
source area (well CF-3). The second-highest 1995 chlorinated solvent concentration (708.3 ug/L)
was observed in the sample from MP-14D, in the deep zone. In 1996, the total chlorinated
solvent concentration in ground water samples decreased to 2,098 ug/L at well CF-3 and 584
ug/L at monitoring point MP-14D. In ground water samples from well CF-3, TCE
concentrations decreased from 12,800 jig/L in 1995 to 1,660 ug/L in 1996. Above MP-14D in
the silty sand layer, the total chlorinated solvent concentration in 1995 was 112.5 u.g/L (MP-
14M), while in the upper zone of the aquifer at CF-2A, no chlorinated solvents were detected. In
1996, only 60.7 ug/L of total chlorinated solvents were detected in a sample from monitoring
point MP-14M. Furthermore, during both sampling events CAHs were not detected in the
samples from CF-2 (below MP-14D), suggesting that the solutes are not migrating into the fine
sand beneath the coarse sand unit. Chlorinated solvents were not detected above quantitation
limits at any of the furthest downgradient shallow and deep ground water monitoring locations.
On the basis of 1995 site data, TCE accounted for 93 percent of the total detected chlorinated
solvent mass; cis-l,2-DCE accounted for 6.8 percent; and PCE, 1,1-DCE, trans-1,2-DCE, and
vinyl chloride accounted for the remaining 0.2 percent. The fraction of TCE is slightly higher in
-------
the source area (CF-3) and lower downgradient from the source area. In the samples from MP-
14D and MP-14M, TCE accounted for 76 and 23 percent of the total detected chlorinated solvent
concentrations, respectively. The transformation of TCE to cis-l,2-DCE was more advanced in
the 1996 sampling event. In 1996, TCE accounted for approximately 72 percent of the total
dissolved CAH mass and the cis-l,2-DCE percentage increased to 28 percent. In the 1996
ground water sample from location MP-14D, TCE and cis-l,2-DCE each accounted for 49
percent of the total CAHs, while ground water from monitoring point MP-14M had only 17
percent TCE and 83 percent cis-l,2-DCE.
GEOCHEMICAL INDICATORS OF BIODEGRADATION
The degradation of BTEX and CAH compounds in ground water is usually accomplished
through biologically mediated oxidation/reduction reactions, where microorganisms obtain energy
for cell production and maintenance through the transfer of electrons from electron donors to
available electron acceptors (Wiedemeier et. al, 1995 and 1996) . Electron donors at the site
include natural organic carbon, fuel hydrocarbon compounds, and the less-chlorinated solvents
(e.g., cis-l,2-DCE and vinyl chloride). Naturally occurring electron acceptors at the site include
DO, nitrate, ferric iron, sulfate, and carbon dioxide. In reactions where BTEX is used as an
electron donor, the native electron acceptors are preferentially used in the listed order. Redox
potentials observed at the site suggest that the core of the plume is characterized by highly-
reducing conditions associated with sulfate reduction and methanogenesis. Moving outward from
the core of the plume the redox potentials steadily increase until potentials indicative of aerobic
respiration are observed along the margins of the plume. Intermediate regions of the plume are
characterized by denitrification and iron reduction. In the highly-reducing zone ai the core of the
plume, conditions are favorable for the use of CAH compounds as electron acceptors, whereas
the aerobic fringes favor the use of less-chlorinated solvents as electron donors in redox reactions.
CAHs also can be degraded through cometabolic processes in which the CAH is fortuitously
transformed by microbial enzymes produced by microorganisms for other purposes.
The 1995 and 1996 electron acceptor data indicate that biodegradation of fuel hydrocarbons in
the shallow aquifer is occurring via aerobic oxidation, ferric iron reduction, denitrification, sulfate
reduction, and methanogenesis. This is evidenced by strong correlation between areas with
elevated BTEX concentrations and areas with depleted dissolved oxygen, nitrate, and sulfate
concentrations, and increased ferrous iron and methane concentrations. Table 1 summarizes
ground water analytical and geochemical data gathered during the 1995 and 1996 site
investigations. The average background DO concentration in 1995 and 1996 ground water
samples was 9.4 mg/L. Within the area characterized by substantially elevated BTEX and CAH
concentrations, DO concentrations range from 1.8 mg/L to 0.12 mg/L. Nitrate/nitrite (as N) has
been detected in site ground water at concentrations ranging from <0.05 mg/L within the plume
to 5.6 mg/L at the plume boundaries. Ferrous iron concentrations are as low as <0.1 mg/L in
background ground water samples and in the core of the plume are as high as 280 mg/L in 1995
and 45.3 mg/L in 1996. Sulfate concentrations at the site range from <0.1 mg/L in the center of
the plume to a maximum concentration of 76.7 mg/L. Outside of the BTEX plume, the methane
concentrations are below the analytical quantitation limit. The highest methane concentrations,
detected in ground water samples from the center of the plume, were 4.3 mg/L in 1995 and 14.6
ms/L in 1996.
-------
The process where CAH compounds are used as electron acceptor in biologically-mediated
redox reactions is termed reductive dechlorination. During this process, a chlorine atom is
removed and replaced with a hydrogen atom. As a result it is possible for complete sequential
dechlorination from TCE to ethene to occur under optimal geochemical conditions. At this site,
TCE is reductively dechlorinated under anaerobic and reducing conditions to cis-l,2-DCE and
vinyl chloride. cis-l,2-DCE is a more common intermediate than trans-1,2-DCE, which is a more
common component of manufactured solvents. This is further substantiated through a
comparison of the concentrations of TCE to the daughter products cis-1,2-DCE and vinyl
chloride. Within the source area, the molecular mass ratio of TCE to DCE in 1995 was
approximately 13 to 1 and vinyl chloride was not detected. Approximately 150 feet further
downgradient the TCE to DCE ratio was less than 2.5 to 1, with vinyl chloride detected at a
concentration of 2.2 |ig/L. Although some of this decreasing ratio of TCE to DCE is due to the
different sorptive capacities of the two compounds and subsequent migration rates (i.e., the
retarded contaminant velocity of DCE is approximately 25 percent faster than for TCE), both the
substantial decrease in the molar ratio of TCE to DCE and the appearance of vinyl chloride
suggest that reductive dechlorination of TCE is occurring along the axis of the plume.
Furthermore, chloride concentrations range from a background concentration of <0.5 mg/L to an
average maximum concentration of 140 mg/L within the source area, implying that chloride is
being released during the degradation of CAH compounds. As expected, the zone of reductive
dechlorination overlies the source area, where low redox potential, high BTEX concentrations,
and methanogenic conditions encourage use of TCE and DCE as electron acceptors.
Downgradient from the reductive dechlorination zone, the higher dissolved oxygen
concentrations on the plume fringes appear to facilitate aerobic respiration of the TCE daughter
products, cis-1,2-DCE and vinyl chloride. Aerobic respiration appears to have the greatest impact
on the fringes of the plume, where cis-1,2-DCE and vinyl chloride apparently undergo electron
donor reactions with the more oxygenated ground water. From 1995 to 1996, the total dissolved
mass of cis-l,2-DCE decreased eighteen percent and the only detected concentration of vinyl
chloride at the site also decreased. This implies that downgradient from the source area (where
cis-1,2-DCE is being continually produced through reductive dechlorination), cis-1,2-DCE and
any available vinyl chloride are being reduced in electron donor reactions, cis-1,2-DCE and vinyl
chloride are less susceptible to reductive dechlorination because of their lower oxidation states. If
electron donor reactions were not occurring in the less oxidized downgradient ground water, the
cis-1,2-DCE and vinyl chloride plume mass and extent would be expected to increase. However,
the production of cis-1,2-DCE and vinyl chloride in the source area and the decrease in total
dissolved mass of each compound suggests that the less chlorinated CAHs and are serving as
electron donors in biologically mediated reactions downgradient of the source area.
BIODEGRADATION RATE CONSTANTS
Apparent BTEX biodegradation rates were estimated using the method of Buscheck and
Alcantar (1995). An easterly ground water flow path through wells MP-12S, CF-2A, and MP-
15S was used for estimating a biodegradation rate. This flow path represents a ground water
travel path from the anaerobic plume core to the more aerobic downgradient extents. An
exponential fit to the data estimates a decay constant of 0.0015 day"1 in 1995 and 1996. Using the
1995 and 1996 data (Tables 2 and 3), first order plume attenuation rates of 0.001 and
-------
0.0023 day"1 were estimated for BTEX and TCE, respectively, by averaging the rate at individual
points calculated using the Buscheck and Alcantar (1995) Shrinking Plume Method.
BIOPLUME H MODEL PREDICTIONS
The results of a site-specific Bioplume II model suggested that under current conditions,
approximately 60 years would be required for remediation by natural attenuation (RNA) to reduce
dissolved benzene concentrations to below the Massachusetts benzene maximum contaminant
level (MCL) of 5 ug/L. Because there is no accurate record on the volume and frequency of fuel
and solvent spills at the site, several conservative assumptions were made until the modeled plume
matched the observed 1995 BTEX plume. The model was calibrated using two pumping periods
that simulated an increasing source area and strength for a 20-year period (1966-1986) to
represent the start of fire training activities and the buildup of a residual source. A third pumping
period simulated the end of fire training activities using a 5 percent per year source weathering
term within the bum area. An injection source upgradient from the site at the waste fuel tank was
included in the third pumping period to simulate the release of waste fuel during the 1986
abandonment of the waste fuel tank and pipe. A final pumping period simulated 5 percent per
year source weathering at all injection sources until the 1995 sampling event. Following model
calibration, a 5 percent per year source decay (weathering) rate was used to simulate the fate and
transport of the dissolved BTEX plume until RNA was complete. A calibrated anaerobic
biodegradation rate constant of 0.001 day"1 was used in the Bioplume n model for this site.
This model predicts declining plume concentrations, with the plume reaching its maximum
downgradient extent in approximately 30 years. After 10 years, the extent of the 1,000-ug/L
contour remains stable; however, the maximum BTEX concentration decreases by 33 percent
from approximately 33,190 ug/L to 22,000 \igfL. After 30 years of weathering (year 2025), the
dissolved plume reaches the maximum extent, approximately 150 feet downgradient from the
calibrated position. At the modeled maximum downgradient extent, the BTEX plume does not
leave the site, nor does it impact any potential receptors. In addition, while the BTEX plume is at
its maximum downgradient extent, the 100-fag/L and 1,000-ug/L isocontours near the center of
the plume are both receding. After 30 simulation years, the maximum BTEX concentration has
decreased to approximately 4,550 u.g/L, or 14 percent of the calibrated maximum concentration.
After 62 years of natural weathering, the model suggests that the ground water plume will have
almost completely attenuated, with a maximum BTEX concentration of 35 ug/L in the source
area. Further model simulation suggests that after 62 years, the plume is completely degraded. A
second ground water model which simulated the effect of RNA combined with soil bioventing,
vertical ground water circulation, and excavation of contaminated soils at the waste fuel pipe
outfall suggested a total time for site remediation of 30 years.
DISCUSSION AND CONCLUSIONS
The 1995 and 1996 ground water analytical results imply that BTEX and CAHs are being
biodegraded. However, the 1996 ground water sampling results suggest that RNA at the site
appears to be proceeding more rapidly than predicted by the numerical model. Several
conservative assumptions were made during initial ground water modeling because insufficient
contaminant data were available prior to the 1995 investigation. Therefore, the ground water
model was calibrated only on the basis of the 1995 soil and ground water data. Consequently, the
existing ground water model may be overly conservative. The model however, does suggest a
-------
worst-case contaminant fate and transport scenario which could be recalibrated. If the present
geochemical data base were used to recalibrate the Bioplume n model, less conservative and
more realistic assumptions regarding contaminant fate and transport processes could be made.
On the basis of the 1995 ground water data and numerical modeling results, a remedial
alternative consisting of RNA with long term monitoring (LTM), soil bioventing in the bum area,
vertical ground water recirculation within selected monitoring wells, and excavation of the
contaminated soils near the waste fuel pipe outfall was recommended. The present-worth cost of
the proposed remedial alternative was approximately $400,000 with modeled remediation time of
30 years. The estimated present worth cost of only RNA with LTM was approximately 5300,000
for 60 years of estimated remediation. Both of the proposed remedial alternatives included
maintaining institutional controls on soil and ground water use at the site, and both are protective
of human health and the environment. The more expensive remedial alternative was
recommended because of the reduced time required for remediation.
Upon review of the 1996 monitoring results, these recommendations would likely change. At
this site and other similar sites where soil and ground water do not present an immediate risk to
potential receptors, a ground water monitoring program could be implemented for a 1 to 2-year
time period to conclusively demonstrate RNA to the public and regulatory community and better
establish degradation rates and model calibration points. Then, if required, the data from LTM
program could be used to develop a ground water model that will more accurately simulate future
site conditions for a remedial alternative analysis.
The cost of the 1996 ground water sampling event was approximately 15 percent of the total
cost of the initial 1995 soil and ground water investigation. At this site, the additional expense of
the second sampling event would substantially reduce the total cost of a recommended remedial
alternative because more accurate (and less overly conservative) fate and transport predictions
could be made using 2 years of geochemical data. If a monitoring program can effectively
demonstrate that RNA will remediate a site, a more favorable response to natural attenuation
would be expected from the regulatory and public community and ground water modeling may
not be necessary.
REFERENCES
Buscheck, T.E., and Alcantar, C.M., 1995, Regression Techniques and Analytical Solutions to
Demonstrate Intrinsic Bioremediation. In: Proceedings of the 1995 Battelle International
Symposium on In Situ and On-Site Bioreclamation, April 1995.
Wiedemeier, T.H., Wilson, J.T., Kampbell, D.H., Miller, R.N., and Hansen, I.E., 1995, Technical
Protocol for Implementing Intrinsic Remediation with Long-term Monitoring for Natural
Attenuation of Fuel Contamination Dissolved in Ground Water. Prepared by the Air Force
Center for Environmental Excellence.
Wiedemeier, T.H., Swanson, M.A., Moutoux, D.E., Gordon, E.K., Wilson, J.T., Wilson, B.H.,
Kampbell, D.H., Hansen, I.E., Hass, P., and Chapelle, F.H., 1996, Draft Technical
Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water,
Revision 1. Prepared by the Air Force Center for Environmental Excellence.
-------
Table 1 Summary of 1995 and 1996 Ground Water Analytical data
Sample
ED
MP-4S
MP-5M
MP-12 S
MP-14 M
MP-14D
MP-15 S
MP-15M
MP-15 D
CF-2
CF-2 A
CF-3
CF-5
Table 2
Table 3
Total
BTEX
Date (ng/L)
May 95 32557
July 96 26125
May 95 49.7
July 96 23.9
May 95 25012
July 96 21210
May 95 324
July 96 173
May 95 1652
July 96 1254
May 95 0.92
July 96 ND
May 95 ND
July 96 BLQ
May 95 46.8
July 96 20.8
May 9 5 ND
July 96 ND
May 95 3020
July 96 2006
May 95 6266
July 96 4047
May 95 3.71
July 96 10.90
Calculation
Well
MP-4S
MP-5M
MP-12S
MP-14M
MP-14D
MP-15D
CF-2A
CF-3
Calculation
Well
MP-5M
MP-14M
MP-14D
CF-3
TCE
(H5/L)
ND
ND
4.40
3.20
4
7
26
10
541.0
289.0
ND
ND
ND
ND
BLQ
ND
ND
ND
ND
ND
12800
1660
1.50
94.60
cis- 1,2- Vinyl
DCE Chloride Methane
(agO.) (ug'l.) (mg/L)
ND
ND
BLQ
BLQ
ND
ND
86.70
50.60
158.00
288.00
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
732.0
434.00
7.60
35.00
ND
ND
ND
ND
ND
ND
ND
ND
2.20
1.70
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
of BTEX Decay
C(t) [1996]
(.ug/L)
26,125
24
21,210
173
1,254
32
2,006
4,047
0.073
0.237
0.362
1.54
0.031
0.073
3.421
8.79
4.286
14.63
0.002
BLQ
0.001
0.021
0.046
0.129
BLQ
BLQ
0.305
0.557
0.008
0.028
0.004
0.008
Dissolved
Ethene Oxygen
(mg'L) (mg/L)
0.005 0.52
0.008 1.23
NA 0.17
ND 0.25
0.003 0.12
<0.003 0.17
BLQ 0.21
ND 0.2
NA 0.28
<0.003 0.24
BLQ 0.67
ND 6.21
NA 0.43
ND 0.15
ND 0.24
ND 0.43
NA 0.34
ND 0.42
ND 0.4
ND 1.8
NA 0.12
ND 0.17
ND 0.73
ND 2.68
Nitrite-^
Nitrate
(asN)
(mg'L)
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
0.09
<0.05
0.09
0.09
0.7
2.73
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
0.22
0.1
<0.05
<0.05
0.34
0.41
Ferrous
Iron
(mg/L)
100
37.3
9
5.3
20
7
280
40.5
280
45.3
9
<0.05
7.5
2.1
9
6.2
4.5
4.7
3
3.8
10
5.4
5.5
0.4
Sulfate Chloride
(mg/L) (mg'L)
2.41
<0.5
2.28
2.45
8.1
1.6
8.4
6.1
<0.5 1.1
<0.5
7.62
11.1
• • 0.86
<0.5
20
3.16
<0.5
<0.5
2.28
3.83
13.2
10.6
<0.5
<0.5
1.43
<0.5
24.6
16.6
1.5
146.0
84.6
150.0
131.0
3.2
1.6
2.9
33
9.8
9.8
1.1
<0.5
0.7
<0.5
1.9
<0.5
1.1
<0.5
Total
Organic
Carbon
(mg/L)
60.2
42.6
4.3
2.7
67.8
61.8
53.3
28.5
94.4
77.4
7.1
1.5
1.6
1.2
2.0
3.3
0.8
0.3
52.5
40.0
25.8
24.7
3.9
4.4
Rate Using Shrinking Plume Method
Q[1995]
(ug/L)
32,557
50
25,012
324
1,652
52.1
3020
6,266
Time Between
Samples (days)
425
• 425
425
425
425
426
425
425
Average
of TCE Decay Rate Using Shrinking
C(t) [1996]
(UgO.)
3
10
2S9
1,660
C
i[1995]
(ug/L)
4
26
541
12,800
Time Between
Samples (days)
425
425
425
425
Average
Decay Constant (k)
(day1)
0.0005
0.0017
0.0004
0.0015
0.0006
0.0011
0.0010
0.0010
0.0010
Plume Method
Decay Constant (k)
(day1)
0.0007
0.0022
0.0015
0.0048
0.0023
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CF-1
LEGEND
200
400
Feet
• Ground Water Monitoring Location
—- 237 Line of Equal Ground Water Elevation
(feet M.S.L)
A—A' Hydrogeologic Cross • Section
Location
Figure 1. Site Layout and Ground Water Flow Map
-------
CF-1
*CF.
,CF-7
•-1A
LEGEND
kMP-2S
Approximate
Bum Area \
.MP-1S.D _*-
• Ground Water Monitoring Location
—100— Line of Equal BTEX Concenteration
(pg/L)
•CF-4
kMP-3S
MP-16D
CF-;
MP-8S.8M
•6,6A
kMP-9S
.MP-6S
.MP-7S
200
400
Fest
Figure 2. BTEX Isopleth Map for Ground Water, July 1996
kCF-7
LEGEND
CF-1*
tMP-2S
• Ground Water Monitoring Location
—100— Line of Equal CAH Concenteration
(M9/L)
MP-1S.D
Approximate
Bum Area
•MP-4S
..MP-3S
MP-16D
CF-8«
MP-8S.8M
kMP-9S
MP-6S
200
..MP-7S
400
Peet
Figure 3. Total CAH Isopleth Map for Ground Water, July 1996
-------
100 200
Feet
Varved Silt, Clay, and Sand Lacustrine Deposits
Vertical Exaggeration = 5x
Figure 4. Vertical Extent of Dissolved BTEX, 1995-1996
I Med.-Coarse Sand,
Poorly Sorted
Varved Silt Clay, and Sand Lacustrine Deposits
140 '•
Vertical Exaggeration = 5x
Feet
Figure 5. Vertical Extent of Dissolved CAHs, 1995-1996
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BIOGRAPHICAL SKETCHES
Mr. Mark Vessely is a associate geological engineer with Parsons Engineering Science, Inc.
[1700 Broadway, Suite 900, Denver, CO 80290, phone: (303) 831-8100, fax: (303) 831-8208].
His responsibilities include site characterization, contaminant transport modeling in support of
remediation by natural attenuation, and design and installation of remediation systems to perform
bioventing and soil vapor extraction. He holds a B.S. in Geological Engineering from the
Colorado School of Mines.
Mr. David E. Moutoux is an environmental engineer and project manager with Parsons
Engineering Science, Inc. [1700 Broadway, Suite 900, Denver, CO 80290, phone: (303) 831-
8100, fax: (303) 831-8100]. His responsibilities include site characterization, geochemical
analysis, and contaminant transport modeling to investigate/document natural attenuation of
dissolved petroleum and chlorinated aliphatic hydrocarbons. He holds an A.B. in Earth Science
and Engineering, a BE. in Engineering Science, and an M.E. in Engineering Science, all from
Dartmouth College.
Dr. Donald Kampbell is a senior research chemist with the U.S. Environmental Protection
Agency's National Risk Management Research Laboratory, Subsurface Protection and
Remediation Division [P.O. Box 1198, Ada, Oklahoma 74820, phone: (405) 436-8564, fax: (405)
436-8703]. His current research involves studies on evaluation of cometabolic bioventing
systems, site characterization for natural attenuation, and development of chemical assay
techniques for field site use. Dr. Kampbell holds graduate degrees in civil engineering and soil
chemistry.
Mr. Jerry E. Hansen is a program manager with the Air Force Center for Environmental
Excellence at Brooks Air Force Base [2504 D Drive, Suite 3, Brooks AFB, TX 78235, (210)
536-4353]. Mr. Hansen is currently managing AFCEE's innovative remedial
approach/technology efforts at more than 40 Air Force facilities nationwide. He holds a B.S. in
Mechanical Engineering from the University of Nebraska, and an M.S. in Aeronautical
Engineering from the University of Texas-Austin.
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