Robert C. Roback Los Alamos National Laboratory Larry Hull
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EMSP Workshop, 2003LA-UR-03-3439
Field-Scale in situ Measurements of Vadose Zone Transport Using Multiple Tracers at
INEEL Vadose Zone Research Park
Robert C. RobackLos Alamos National Laboratory
Larry HullIdaho National Engineering and Environmental
Laboratory
Yemane AsmeromUniversity of New Mexico
EMSP Workshop, 2003LA-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
EMSP Workshop, 2003LA-UR-03-3439
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
EMSP Workshop, 2003LA-UR-03-3439
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)
EMSP Workshop, 2003LA-UR-03-3439
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
EMSP Workshop, 2003LA-UR-03-3439
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
EMSP Workshop, 2003LA-UR-03-3439
THE VZRP• Located near
major facilities and sites with most pressing environmental management issues
• Similar subsurface geology and hydrology
• Proximal to Big Lost River
EMSP Workshop, 2003LA-UR-03-3439
Subsurface Geology
EMSP Workshop, 2003LA-UR-03-3439
VZRP Arial View
EMSP Workshop, 2003LA-UR-03-3439
Wells Along the Big Lost River
EMSP Workshop, 2003LA-UR-03-3439
The VZRP (cont.)
EMSP Workshop, 2003LA-UR-03-3439
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
EMSP Workshop, 2003LA-UR-03-3439
Instrumentation
Wells are completed with stainless steel wellboxes. At instrumented boreholes, data are collected automatically and communicated with INEEL computer network over radio link.
Gas and water sampling ports are equipped with quick connects to facilitate sampling.
EMSP Workshop, 2003LA-UR-03-3439
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
EMSP Workshop, 2003LA-UR-03-3439
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
EMSP Workshop, 2003LA-UR-03-3439
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 O18 and D. 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.)
EMSP Workshop, 2003LA-UR-03-3439
Discharge from INTEC
0.0
0.5
1.0
1.5
2.0
2.5
0 20 40 60 80 100
Time since test began (days)
Discharge (Mgal/day)
Average 1.53 Mgal/dayStd. Dev. 0.25 Mgal/dayMax 2.30 Mgal/dayMin 0.55 Mgal/day
S N S
EMSP Workshop, 2003LA-UR-03-3439
EMSP Workshop, 2003LA-UR-03-3439
Continuous Logging of Tensiometer Data
Well 204 Tensiometer Data - W of North Pond
-400
-200
0
200
400
600
800
1000
1200
5/24/2002 7/13/2002 9/1/2002 10/21/2002 12/10/2002 1/29/2003 3/20/2003 5/9/2003
Date
Presssure (cm H2O)
204-AT-045
204-AT-058
204-AT-063
204-AT-090
204-AT-103
204-AT-127
204-AT-148
204-AT-152
204-AT-157
204-AT-168
N pond 8/21 -8/25N pond 9/21 -10/4S pond 8/27 -9/20S pond 10/5 topresent
pulledPTs
pulledPTs
EMSP Workshop, 2003LA-UR-03-3439
Chloride
0
40
80
120
160
0 14 28 42 56 70 84 98 112 126
Days
Cl (ppm)
MON-200-129.5'MON-202-125.2'MON-210-62.2'
MON-211-132.2'OUTFALL
pond switch
EMSP Workshop, 2003LA-UR-03-3439
Sodium
0
25
50
75
100
125
150
175
200
-14 0 14 28 42 56 70 84 98 112 126
Days
Na (ppm)
MON-200-129.5'
MON-202-125.2'
MON-210-62.2'
MON-211-132.2'
OUTFALL
198-114'
198-126'
204-129'
N to S pond
EMSP Workshop, 2003LA-UR-03-3439
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
EMSP Workshop, 2003LA-UR-03-3439
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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