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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
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                  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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EMSP Workshop, 2003
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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

EMSP Workshop, 2003
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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
EMSP Workshop, 2003
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