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Field-Scale in situ Measurements of Vadose
Zone Transport Using Multiple Tracers at
INEEL Vadose Zone Research Park
Robert C. Roback
Los Alamos National Laboratory
Larry Hull
Idaho National Engineering and Environmental
Laboratory
Yemane Asmerom
University of New Mexico
EMSP Workshop, 2003
LA-UR-03-3439
Environmental Issues
• At INEEL, organic, inorganic, and
radioactive contaminants have entered the
environment and are present in the vadose
zone, for example:
– Idaho Nuclear Technology and Engineering
Center (INTEC) – 90Sr
– Radioactive Waste Management Complex
(RWMC) – U, Pu, solvents
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Project Goals
• Improve conceptual models of contaminant
migration through a thick, layered and fractured
vadose zone
• Provide site-specific field-scale parameters for
INEEL to better predict contaminant migration
through the vadose zone
Results will have important applications at INEEL in assessing remedial
actions and long-term stewardship and for understanding vadose
zone flow and transport in general
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Main Participants
• LANL: R. Roback – PI, P. Reimus and J. Sullivan,
(field and lab tests), C. Jones (Dissertation project
under R. Bowman NMT)
• INEEL: L. Hull – PI, T. McLing (field and lab
tests) and collaborations with: C. Baker
(hydrology), G. Heath (geophysics), L. Street
(EM), S. Magnuson (EM) and many others
• UNM: Y. Asmerom – PI, E. Nichols (MS thesis
under Asmerom)
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In-Kind Support and Collaborations
• Major investment by INEEL to install sampling
and monitoring equipment
• Support from INEEL EM program through
sampling and maintenance
• Collaborative studies:
– geophysics (ERT array) through INEEL LDRD
– monitoring and interpretation of hydraulic parameters
through INEEL
– cooperation with INTEC personnel who control
discharge
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Research Site:
INEEL – Vadose Zone Research Park
• Constructed to receive process water from
INTEC operations
• Provides instrumentation and facilities to
address vadose zone flow and transport
• Uncontaminated site with subsurface
geology and hydrology very similar to those
beneath INTEC and SDA
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THE VZRP
• Located near
major facilities
and sites with
most pressing
environmental
management
issues
• Similar
subsurface
geology and
hydrology
• Proximal to Big
Lost River
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Subsurface Geology
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VZRP Arial View
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Wells Along the Big Lost River
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The VZRP (cont.)
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VZRP Instrumentation
• Monitoring Wells at infiltration ponds and BLR
– 5 in aquifer (525’)
– 7 at alluvium/basalt contact (45’-50’)
– 9 at top of sedimentary interbed (125’-130’)
– 4 to depth of 250’
• Instrumented boreholes
– Lysimeters
– Gas sampling ports
– Water content sensors, thermocouples, tensiometers
• ERT arrays- down hole and along surface
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Instrumentation
Wells are completed with stainless steel Gas and water sampling
wellboxes. At instrumented boreholes, data ports are equipped with
are collected automatically and communicated quick connects to facilitate
with INEEL computer network over radio link. sampling.
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Project Objectives
Simultaneously inject multiple tracers to
investigate:
• Spatial and temporal transport of reactive and
conservative tracers through vadose zone
• Migration of colloids through the vadose zone
• Influence of degree of saturation, flow rate, flow
transients, and water chemistry on these processes
• Interactions between vadose zone and saturated
zone
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Methods
• Examine tracer recovery for conservative, reactive and
colloid tracers
– Use isotopically-tagged natural colloids?
• Examine natural U and Sr concentration and isotopics to
provide element-specific transport parameters to
contaminants of concern
• Evaluate spatial and temporal patterns in tracer recovery;
compare these to hydraulic data from tensiometers, water
levels, and geophysics
• Laboratory tests to provide transport parameters and
comparison to field results
• Modeling of data
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Some History
• Discharge to ponds was way ahead of schedule
with steady inflow by August
• Sampling of first waters though INEEL EM;
sampling at daily, then weekly, and now monthly
intervals. Over 200 samples collected and most
analyzed for anions, cation; subsets for dO18 and
dD. Geophysical and hydraulic data collected and
is being analyzed
• C. Jones joined project in August at NMT (Ph.D.);
E. Nichols to begin in June at LANL then UNM
(M.S.)
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Discharge from INTEC
2.5
S
Discharge (Mgal/day)
N S
2.0
1.5
1.0
Average 1.53 Mgal/day
0.5 Std. Dev. 0.25 Mgal/day
Max 2.30 Mgal/day
Min 0.55 Mgal/day
0.0
0 20 40 60 80 100
Time since test began (days)
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Continuous Logging of
Tensiometer Data
Well 204 Tensiometer Data - W of North Pond
5/24/2002 7/13/2002 9/1/2002 10/21/2002 12/10/2002 1/29/2003 3/20/2003 5/9/2003
1200
204-AT-045
204-AT-058
1000
204-AT-063
800 204-AT-090
204-AT-103
Presssure (cm H2O)
600 204-AT-127
204-AT-148
400
204-AT-152
204-AT-157
200
204-AT-168
N pond 8/21 -
0
8/25
N pond 9/21 -
10/4
-200 pulled pulled
S pond 8/27 -
9/20
PTs PTs
S pond 10/5 to
present
-400
Date
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MON-200-
Chloride 129.5'
MON-202-
125.2'
160
MON-210-62.2'
120 MON-211-
132.2'
Cl (ppm)
OUTFALL
80
pond switch
40
0
0 14 28 42 56 70 84 98 112 126
Days
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MON-200-129.5'
Sodium
MON-202-125.2'
MON-210-62.2'
200
MON-211-132.2'
175 OUTFALL
150 198-114'
198-126'
Na (ppm)
125
204-129'
100
N to S pond
75
50
25
0
-14 0 14 28 42 56 70 84 98 112 126
Days
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Preliminary Findings
• Discharge pulse defined
• Wells with differing response to conservative
tracer identified
• Refinement of conceptual model
– Lateral flow along lithologic contacts
– Perched saturated zones, unsaturated zones
– Flow velocities
Information critical to plan upcoming tracer tests
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Future Plans
• Summer and Fall 2003
– One to two tracer tests with conservative and reactive
tracers to better understand system
– Sample core from VZRP boreholes for laboratory
experiments
– Evaluate hydraulic and chemical data
• Future work
– Additional tracer tests with different tracers and
colloids, potentially under induced gradients, and
outside of ponds
– Tracer tests in BLR when (if) it flows
– Laboratory experiments as dictated by initial tracer tests
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