DOE/ID-10871

A National Roadmap
for Vadose Zone
Science & Technology
Understanding, Monitoring,and Predicting Contaminant
Fate and Transport in theUnsaturated Zone

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August 2001

A National Roadmap for Vadose Zone Science and Technology

PREFACEThe project management and logistical aspects of initiating a first national roadmap forvadose zone science and technology are daunting. The initial challenge was to select andassemble a team of experts who could identify the research and development needed over the
next quarter century to adequately assess and predict the fate and transport of contaminants in thevadose zone. The second challenge was to ensure that the group was well-versed in U.S.
Department of Energy (DOE) needs, the vadose zone cleanup efforts of other federal agencies,
and the research underway in universities, the private sector, and government facilities (including
the DOE national laboratories). Third, the interests and requirements of federal, state and local
governments had to be considered.
After a lengthy search, 10 internationally recognized individuals were selected and accepted
positions on the Vadose Zone Roadmap Executive Committee. Four of these individuals also
accepted the challenge to serve as workgroup chairs and to assemble the remainder of theparticipants for the workgroups. The full team consisted of 62 individuals, many of whom areinternationally recognized vadose zone experts. These individuals (a complete list is provided inAppendix A) also provided representation from across DOE, other federal agencies, industry,
academia, and the international community.
In March 2000, the Executive Committee met to begin its task. Over the next year, thiscommittee and four (ultimately condensed to three) roadmap workgroups formed the multidisciplinary team that has outlined in these pages a set of vadose zone research and infrastructure
priorities for the next quarter-century.
As a starting point for this group, personnel from the DOE national laboratories who arefamiliar with end user needs and vadose zone issues (including several key collaboratorsdeveloping the compendium Vadose Zone Science and Technology Solutions) prepared asummary of current deficiencies and capability gaps, within the DOE complex, in vadose zone
characterization, monitoring and modeling. The results of this effort were provided to theroadmap team. During the second half of the year, the scope of the roadmap was broadened froma focus on DOE problems and needs to a national perspective on vadose zone contamination as athreat to our invaluable groundwater resources.
This roadmap is drawn in broad strokes. It no doubt leaves important research needs andopportunities uncharted. Nevertheless, it provides the first attempt at a national level to forge apath through what had been unmapped territory. If successful, the research described in thisdocument will dramatically improve characterization, monitoring and modeling capabilities.
These capabilities will provide a firmer scientific foundation upon which regulators and sitemanagers can make confident decisions and predictions when dealing with contamination in thevadose zone. Additional work to refine, extend, and update this roadmap will require continued
dialogue within the vadose zone research community, with other U.S. government and state andlocal agencies, and with affected stakeholders.

– Clayton R. Nichols, Assistant Manager, Research and Development;
U.S. Department of Energy, Idaho Operations Office

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CONTENTSFOREWORD ................................................................................................................................................ v
EXECUTIVE SUMMARY ........................................................................................................................ vii
1.0
1.1
1.2
1.3
1.4
1.5

INTRODUCTION.......................................................................................................................... 1
THE NEED FOR A BETTER UNDERSTANDING OF THE VADOSE ZONE............................................. 1A BROAD NATIONAL ISSUE; A DEPARTMENT OF ENERGY MISSION ............................................. 2
THE NEED FOR A VADOSE ZONE SCIENCE AND TECHNOLOGY ROADMAP .................................... 4
A VISION FOR 2025...................................................................................................................... 9
THE CONTEXT OF PREVIOUS VADOSE ZONE WORK ................................................................... 10

2.0

PHYSICAL, CHEMICAL, AND BIOLOGICAL ASPECTS OF VADOSE ZONE FLOW
AND TRANSPORT ..................................................................................................................... 14
THE IMPORTANCE OF A GHCB FRAMEWORK............................................................................. 15
PHYSICAL DESCRIPTION OF FLOW AND TRANSPORT PROCESSES................................................ 16
CHEMICAL PROPERTIES AND PROCESSES ................................................................................... 27
BIOLOGICAL PROPERTIES AND PROCESSES................................................................................. 32
COLLOIDAL FORMATION AND TRANSPORT ................................................................................ 38
MULTIPHASE FLOW AND TRANSPORT ........................................................................................ 40
UNSTABLE PROCESSES ............................................................................................................... 42

2.1
2.2
2.3
2.4
2.5
2.6
2.7
3.0
3.1
3.2
3.3
3.4
3.5

COMBINING THE BASICS TO UNDERSTAND, MEASURE, MONITOR AND MODELVADOSE ZONE SYSTEMS ....................................................................................................... 45
COUPLING BASIC PROPERTIES AND PROCESSES ......................................................................... 45
COMBINING PROCESSES AND DATA AT DIFFERENT SCALES IN INTEGRATED MODELS ............... 49
ESTIMATION AND REDUCTION OF UNCERTAINTY ....................................................................... 52
IMPROVING SITE MONITORING SYSTEMS ................................................................................... 56
MODEL INTEGRATION AND VALIDATION AT THE SYSTEM LEVEL. ............................................. 61

4.0
4.1
4.2
4.3

NECESSARY SUPPORTING CAPABILITIES AND INFRASTRUCTURE ....................... 66
GENERATING AND COMPILING THE DATA FOR A FOUR-DIMENSIONAL GHCB FRAMEWORK ..... 66
FIELD FACILITIES TO SUPPORT INTEGRATED TESTING AND VALIDATION OF RESEARCH ............ 73
COMPUTATIONAL RESOURCES TO DEVELOP ADEQUATE MODELS AND SIMULATIONCAPABILITIES ............................................................................................................................. 78

5.0
5.1
5.2
5.3

CONCLUSIONS AND RECOMMENDATIONS ..................................................................... 88
THE BOTTOM LINE: HIGHLIGHTS OF EXPECTED RESULTS FROM ROADMAP ACTIVITIES ............ 88
LINKAGES AMONG RESEARCH AND INFRASTRUCTURE ACTIVITIES............................................ 95
VADOSE ZONE RESEARCH IN THE CONTEXT OF ENVIRONMENTAL CLEANUP AND STEWARDSHIPIMPERATIVES ............................................................................................................................. 96
INTERAGENCY AND INTERGOVERNMENTAL COORDINATION IS CRITICAL .................................. 98
THE ULTIMATE DRIVER: PROTECTING THE NATION’S GROUNDWATER RESOURCE ................... 99

5.4
5.5

ACKNOWLEDGMENTS........................................................................................................................ 101
REFERENCES ......................................................................................................................................... 102
ACRONYM LIST..................................................................................................................................... 104
APPENDIX A. ROADMAP CONTRIBUTORS................................................................................... 105
APPENDIX B. TABLE OF ROADMAP ACTIVITIES WITH TASKS AND STATUS POINTS... 106
APPENDIX C. FULL TEXT OF RESEARCH GOALS AS GENERATED BY ROADMAPWORKGROUPS ...................................................................................................................................... 130

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FIGURES AND TABLES
Figure 1 Stewardship Activities Increase as Cleanup is Completed.............................................................. 6
Table 1 Highlights of Results for Physical Description of Flow & Transport Research Activities............. 27
Table 2 Highlights of Results for Chemical Properties & Processes Research Activities........................... 32
Table 3 Highlights of Results for Biological Properties & Processes Research Activities ......................... 38
Table 4 Highlights of Results for Colloidal Formation & Transport Research Activities........................... 40
Table 5 Highlights of Results for Multiphase Flow & Transport Research Activities ............................... 42
Table 6 Highlights of Results for Unstable Processes Research Activities ................................................. 44
Table 7 Highlights of Results for Understanding and Modeling Coupled Systems Research Activities ... 49
Table 8 Highlights of Results for Combining Processes & Data at Different Scales Research Activities .. 51
Table 9 Highlights of Results for Estimation & Reduction of Uncertainty Research Activities................. 55
Table 10 Progressive Steps for a Monitoring System and Program to Accompany Federal Facility
Cleanup and/or Stewardship Activities ........................................................................................ 57
Table 11 Highlights of Results for Improving Site Monitoring Systems Research Activities .................... 61
Table 12 Highlights of Results for Integrating and Validating Site-Wide Models Research Activities...... 65
Table 13 Highlights of Results for GHCB Data Library and Model Set Infrastructure Activities .............. 68
Table 14 Highlights of Results for Sensors, Instrumentation & Emplacement Infrastructure Activities ... 71
Table 15 Highlights of Results for Design & Optimization of Measurement Networks Infrastructure
Activities ...................................................................................................................................... 73
Table 16 Highlights of Results for Facilities for Integrated Field Experiments Infrastructure Activities ... 78
Table 17 Highlights of Results for The Problem Solving Environment Infrastructure Activities............... 82
Table 18 Highlights of Results for Advanced Numerical Algorithms Infrastructure Activities.................. 85
Table 19 Highlights of Results from High-Powered Computing Infrastructure Activities ......................... 87
Table 20 Highlights of Expected Results from Roadmap Activities ........................................................... 88
Table 20 Highlights of Expected Results from Roadmap Activities (cont.)................................................ 89
Table 20 Highlights of Expected Results from Roadmap Activities (cont.)................................................ 90
Table 20 Highlights of Expected Results from Roadmap Activities (cont.)................................................ 91

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FOREWORD
This roadmap is a means of achieving, to the best of our current knowledge, areasonable scientific understanding of how contaminants of all forms move in the vadosezone, in the principal geological environments. This understanding is needed to reduce
the present uncertainties in predicting contaminant movement, which in turn will reduce
the uncertainties in remediation decisions.
The roadmap does not assign a value to the information needed, nor does it express inquantitative terms how much would be saved, were the information in hand. It does notdiscuss tradeoffs in remediation techniques or the political and economic factors
involved. Nor does it explore the use of decision analyses to determine the "best" meansof remediating a site. Rather, the information obtained from the research proposed here
will help determine the best course of action at the most recalcitrant sites of subsurface
contamination in the United States and abroad. Achieving this ultimate objective willtake some time, as fundamental knowledge is needed. However, there will also be
significant value gained almost immediately from these undertakings.
For example, a number of the activities have, as their objective for the first four years,
the transfer of our state-of-the-art knowledge of hydrogeologic processes andmeasurement technologies into the state of practice at priority sites of subsurface
contamination. Accomplishing this transfer of knowledge into practice will improve
decisions taken on remediation techniques almost immediately. In addition, encouraging
bright young people entering the research community to take on the challenges presented
here will permeate new ideas and approaches into the decision process on remediation
techniques almost instantaneously.
For much of the twentieth century, subsurface hydrological scientists focused on
groundwater to develop dependable water supplies. Except for some scientists in the
agricultural sector, there was little interest in vadose zone hydrogeology until the past 20–
30 years. Consequently, our understanding of contaminant migration processes in thevadose zone is often insufficient to make accurate predictions about the future. Past
predictions of flow of contaminants through the vadose zone have been grossly in error,
leading to lack of trust and excessive conservatism in design of remediation techniques(National Research Council, 2000). The purpose of a roadmap like this is to lead tobetter understanding quicker. Better understanding of vadose zone contaminantmigration processes and improved tools for prediction will enable better (more effective
and less costly) cleanups. With present knowledge and technology, satisfactory cleanup
is not possible in all circumstances and confidence in future performance is often low.
Even so, research is not a substitute for cleanup, and where effective solutions are
currently possible, cleanup in progress must proceed.
At DOE and other federal facilities, remediation processes are already underway.
However, there are still mysteries of how flow through the vadose zone occurs in somegeological formations, such as karst and fractured rock, and difficulties remain in
predicting, for instance, the transport of colloids and movement of non-aqueous phase

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liquids. Because of these and other limits on our understanding, unacceptable quantitiesof pollutants will remain at some sites, even after currently planned remediation.
Therefore, while remediation should progress in accordance with agreements reachedunder the Federal Facilities Act, only incomplete remediation is possible with today's
knowledge of subsurface conditions and flow. The research activities mapped out here
are intended to reach a level of understanding that will enable satisfactory remediation at
all sites of subsurface contamination.
Although this initial roadmap effort focuses on the problems of sites managed by
DOE and other federal entities, these problems are a small subset of the water resource
problems, both of quantity and quality, in the world today. There are increasing water
demands and shortages. With just the present world population of 6 billion, the annual
depletion rate of groundwater aquifers is 160 billion cubic meters (Brown, 2001). As aresult of groundwater withdrawals for human uses, water tables in the High Plains
Aquifer (e.g. Ogallala) have dropped by more than 150 feet, decreasing the saturated
thicknesses more than 50 percent (Alley et al., 1999). This depletion of water resources
can only increase with future population growth.
Water suitable for human and agricultural uses has been a crucial historical factor.
Despite hurricanes and tornadoes, “more than any other weather or climate event, the1930s drought shaped American society. …. At its height in July 1934, nearly two-thirdsof the nation was considered to be in severe to extreme drought” (Henson et al., 1999).
The National Drought Policy Commission (2000) reported that “drought occurs somewhere every year in the United States. It can and does extend over long periods and large
areas, and it brings hardship.” For instance, the 1998 drought in Texas cost $11 billion.
When water supplies were plentiful, water management in the United States wasalmost solely supply management. Now, water management is evolving to include
optimal use, quality maintenance, and conservation. Protecting groundwater quality isparticularly important because 40 percent of U.S. public water supplies, plus anadditional 40 million people, derive their drinking water from groundwater (Solley et al.,1993). Thus, more than 50 percent of the U.S. population depends on groundwater for its
drinking water. Monitoring the vadose zone to detect contaminant migration early is
critical, as is preventing contaminated waters from passing through the vadose zone togroundwater aquifers.
In summary, the vadose zone is the key to the security of our groundwater resources.
Through this permeable cover atop the groundwater table, rain and snow replenish ourunderlying aquifers. Contaminants migrating through the vadose zone threaten thisresource. This roadmap for vadose zone science and technology is intended to give us
the tools needed to describe and forecast accurately the processes controlling this natural
recharge and the consequences of subsurface contaminants on our groundwater.

– Daniel B. Stephens, Chair Vadose Zone Executive Committee;

President, Daniel B. Stephens & Associates, Inc.

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EXECUTIVE SUMMARY
The Context
The vadose zone comprises the region between the land surface and underlying
groundwater aquifers. Until recently, disposing of waste solids and liquids in the vadosezone caused little concern because this seemed a safe way to contain the wastes and keepthem relatively immobile. Discoveries of hazardous and radioactive chemicals migrating
through the vadose zone and entering groundwater have changed many assumptions
about the vadose zone and heightened the importance of understanding this complex
region of the earth. We now know that the movement of water (or other fluids) throughthe vadose zone can transport many waste components to underlying aquifers. Oncegroundwater is contaminated, control of the contaminants becomes more difficult andcostly. Impacts on human health and the environment can result, as the contaminatedgroundwater discharges into surface waters or is pumped to the surface for irrigation,
drinking, or other uses.
The circumstances that the Department of Energy (DOE) faces in addressing
uncertainties about contaminant movement in the vadose zone at its cleanup sites apply invarying degrees to other owners of vadose zone contamination problems and toenvironmental regulators. Our current ability to predict and optimally manage fluid flow
and contaminant transport processes in the vadose zone is limited by inadequate
understanding of processes that typically incorporate geological, hydrological, chemical,
and biological processes and properties. There is a general lack of methodologies toadequately represent water flow and contaminant transport processes and properties inhighly heterogeneous media across multiple spatial and temporal scales. These
uncertainties and knowledge gaps are exacerbated by our general inability to simulateeven known processes realistically, given limited data, or to simulate assumed processes
with little data. The uncertainties in our understanding, our data, and our ability tomonitor and model contaminant movement in the vadose zone have eroded public trustand greatly increased public expense.
In the late 1990's, DOE undertook a major review of the state of the art associatedwith the vadose zone. The result was Vadose Zone Science and Technology Solutions, a
two-volume compendium of both the state of practice and the state of science in vadosezone characterization, monitoring, and modeling, as well as technologies for remediation
and waste isolation. It also contains a series of recommendations on filling gaps in our
knowledge of vadose zone properties and technologies. During this same period, scienceand technology (S&T) roadmaps for individual DOE sites were being prepared. These
predecessor activities contributed substantially to developing this first national S&T
roadmap for vadose zone characterization, monitoring, and modeling.

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The Roadmap Activities
The technical content of the roadmap is captured in 61 activities, most of which haveassociated tasks and status points with either a near-term, mid-term, or long-term timeframe for achievement. Near-term means roughly within 4 years of beginning roadmap
implementation. Mid-term means the results can be expected within a decade. Longterm applies to results over two to three decades (roughly, a 25-year horizon). Eachactivity represents an area for which critical research objectives and application
requirements can be clearly stated.
The narrative to describe and support the 61 activities is divided into five major
sections:•

Section 1 introduces the rationale for undertaking this effort, including the scopeof the problem at DOE sites and elsewhere, the background of previous work on
which this roadmap builds, and the Executive Committee’s vision of what could
be achieved, if the roadmap activities are implemented.

•

Section 2 describes research and application activities to improve theunderstanding of basic physical, chemical and biological processes and properties,
as well as improving the modeling, measuring, and monitoring of flow andtransport.

•

Section 3 identifies and discusses activities for cross-cutting issues, such as
coupled processes, scaling, measuring and reducing uncertainty, advances in site
monitoring systems, and the integration and validation of characterization,
monitoring, and assessment tools at the system (field scale) level.

•

Section 4 focuses on the infrastructure and capabilities required to accelerate
progress along the activity pathways identified in Sections 2 and 3.

•

Section 5 presents general conclusions and recommendations from the Executive
Committee, including a summary review of major near-term, mid-term, and longterm results that it anticipates will follow from pursuing the roadmap, key
linkages among the activities, and the importance of broad cooperation andcoordination if the goals of the roadmap are to be achieved.

In many instances, early results from the research activities described in the roadmap,
particularly application status points, are prerequisites for a supporting capability or
infrastructure element. These capabilities and supporting elements, in turn, enable andaccelerate the more advanced work along the research activities. Key elements ofinfrastructure and supporting capability include:•A national virtual library of geological, hydrologic, chemical, and biological datafrom major sites of vadose zone contamination, together with prototype numericalmodels designed to work with these multidisciplinary datasets.

•

Advances in sensor instrumentation, particularly in miniaturization (packaging)and emplacement technology.

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Advances in design and optimization of sensor networks for monitoring andcharacterization.

•

Facilities to support integrated testing and validation of vadose zone research.

•

A problem-solving software environment developed specifically for vadose zone
modeling and analysis tasks.

•

Advances in numerical algorithms directed at difficult vadose zone computational
problems.

•

A high-power computing capability dedicated to vadose zone applications andrelated environmental S&T issues.

Anticipated Results
Many of the near-term results expected for both the research and infrastructure
activities share a common theme: moving the state of the art to the state of practice. Thismeans getting the current knowledge and capabilities already existing in the researchcommunities into operational use at the nation’s priority sites of vadose zone
contamination. One benefit is that these tasks “pick the low-hanging fruit,” providing
quick returns because much of the research investment has already been made. A lessobvious benefit is that concerted effort to get new knowledge and technical capability
into practice will bring researchers and solution-oriented problem owners into continuing
and close interaction.
For the mid-term, the roadmap outcomes of greatest significance are likely to be thecumulative advances in monitoring systems for vadose zone sites. A sound and efficientmonitoring program is critical at major sites during environmental cleanup and afterward,
throughout any period of stewardship required by residual contamination on site. The
state of practice has been to monitor the groundwater at and around the site, rather thanmonitoring the vadose zone. However, for many sites where contaminants are at somedistance from the water table, waiting until contaminants appear in the groundwater isless desirable than monitoring the vadose zone. If remediation can remove or isolate
source terms and halt plumes while they are still in the vadose zone, groundwatercontamination can be prevented. In addition, the effectiveness of the remediation is often
greatly enhanced, and the cost significantly reduced, compared with groundwater
remediation alternatives.
Many of the long-term results anticipated from the roadmap activities will provide
better tools for supporting site-wide assessments and decisions on environmental cleanup
and stewardship. Models and data gathering will undoubtedly improve incrementally inthe near and mid-term. However, after a decade or so of pursuing the roadmap’s
activities, a qualitative leap forward is expected in the ability to visualize, quickly andaccurately, the current and projected future states of site-wide vadose zone systems.
These projections, which will carry levels of certainty and sensitivity unattainable atpresent, should suffice to win the confidence of regulators and the public.

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How the Roadmap Links to Environmental Cleanup and StewardshipThis roadmap covers only a part of the effort needed for environmental cleanup andstewardship of the nation’s vadose zone contamination problems. It does not cover the
S&T for remediation and isolation techniques or other modes of action for exercisingstewardship in the broadest sense. Nor does it include the S&T to support assessment of
impacts on human health, the environment, and the local, regional, or national economy.
Nevertheless, results of activities in this roadmap will affect S&T activities forcontaminant removal, immobilization, or other cleanup operations, as well as choices
among cleanup and attenuation options. Progress in the S&T for remediation activities
will in turn influence the work needed in site visualization and monitoring systems,
sensor and measurement techniques, and even the amount of understanding needed about
various vadose zone processes. More broadly, achieving near-term results will influence
the support from stakeholders and government budgeting authorities for further efforts tounderstand, monitor, and control contaminants in the vadose zone. In this light, it isimportant that this roadmap be integrated with the larger context of S&T planning forcleanup and stewardship.
Given the broad potential applicability of the S&T work identified here—and thesheer scale of the effort that implementation will require—a coordinated approach
involving many federal agencies is essential. From this perspective, the current versionof the roadmap is unquestionably a first step for consideration and revision in a context
where the other agencies are more fully involved as partners with the DOE.1 There
should also be some mechanism to represent State and local entities in the process
because of their growing importance in oversight of and decisions about environmental
cleanup and stewardship.
Whenever the resources needed for a range of potential activities are limited, there ispotential for competition among those activities. However, focusing on just the potential
for resource competition between vadose zone research and ongoing cleanup operations
ignores the considerable potential for constructive influences and synergies, which asystematic approach to resource allocation can tap. A well-planned program for researchand development to improve cleanup and stewardship options can, and should, be a
profitable return on investment for the nation. The ultimate driver for significant
investment in the research and infrastructure activities contained in this roadmap is toprotect an even more valuable national treasure, our groundwater resource.

1

However, this report was developed by a broadly representative group of researchers. The Executive
Committee included representatives of the agencies most likely to be involved in a coordinated national
effort.

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xi1.0 Introduction

1.0

INTRODUCTION

1.1

The Need for a Better Understanding of the Vadose Zone

The vadose zone comprises the region between the land surface and underlying
groundwater aquifers. Although technically water in the vadose zone is water in the
ground, we shall adhere to the classical definition of groundwater as “subsurface waterthat occurs beneath the water table in soils and geological formations that are fully
saturated” (Freeze and Cherry, 1979). Across the United States, activities by individuals,
companies, and state and local governments, as well as by federal government agencies,
have resulted in the release of contaminants at or near the land surface. Underground
waste burial, landfill dumping, and direct discharge of liquids to the soil surface weregenerally accepted practice for disposal of a wide range of wastes. These wastes were,until recently, believed to be relatively immobile and thus were viewed as not being a
potential source of aquifer contamination. The prevailing wisdom held that retention in
the vadose zone, decomposition (of chemical and organic wastes), or dilution to avanishingly low concentration would keep us safe. As a result, little attention was given
to understanding the nature of the vadose zone, the potential pathways for fluids orcontaminants to disperse throughout the zone, or the myriad possible interactions among
fluids; contaminants; and the chemical, biological, and physical components of thevadose zone.
We now know that the movement of water (or other fluids) through the vadose zone
can transport many waste components to underlying aquifers. From there, groundwater
movement can carry them to springs, streams, lakes, rivers, and coastal waters. Wells
can pump wastes in the aquifer back to the surface, where environmental and human
exposures can occur. Discoveries of hazardous and radioactive chemicals migrating
through the vadose zone and entering groundwater have changed many assumptions
about the vadose zone and heightened the importance of understanding this complex
region of the earth.
In the absence of adequate predictive capabilities, the ability to detect contaminantmigration and fate early is all the more critical. Extensive field experience andtheoretical considerations have demonstrated that remediation costs and risks increase
exponentially as contaminated volumes increase and concentrations decrease. From acontainment/remediation standpoint, detecting contaminant migration when it is still inthe vadose zone—before it reaches underlying and downgradient groundwater—provides
the best opportunity (short of preventing releases in the first place) for less-difficult
actions at lower cost and risk. Recent reports by the National Research Council address
this point. The authors of one study concluded that pump and treat technologies are
inefficient for remediating contamination in groundwater. This conclusion supports the

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argument that intervention while contaminants are still in the shallow vadose zone ispreferable to waiting until they have migrated into aquifers or to greater depths.2,3
Before intervention can be undertaken, even before one can decide which intervention
approach is best, subsurface contaminants must be identified. Their nature and extent
must be determined. The physical, chemical, and biological properties of that specificvadose zone environment must be characterized well enough to know whether, how, andhow fast the specific contaminants will be transported by fluid movement through thevadose zone. While remediation activities are being planned and implemented, thevadose zone within and around the contaminated volume must be monitored to determine
whether and where contaminants are moving. If the chosen remediation approach leaves
contamination in the vadose zone (which will be inevitable in many instances), continued
monitoring of the site is often essential. Given the complexity of the vadose zone
environment and of the interactions between this environment and contaminants,
computer-based modeling and simulation are essential aids in understanding vadosezone processes and contaminant transport, including visualizing existing and potentialconditions at a contaminated site.
1.2

A Broad National Issue; a Department of Energy Mission

Threats to valuable, often irreplaceable, groundwater resources from contaminants inthe vadose zone occur nationwide. They arise from a remarkably diverse range of humanactivities. Leachate from municipal or commercial landfills and leaks from abandoned or
aging underground fuel tanks and piping pose problems in every region, as do industrial
dump sites and process waste burial grounds. In agricultural areas, pesticides, fertilizers,
pathogenic organisms, and spilled or dumped fuels can be transported to groundwater,sometimes threatening the principal source of water for irrigation and other commercial
uses, as well as the drinking water for humans and livestock (see accompanying textbox
on agricultural herbicides). In some suburban areas, increasing household density andwater consumption, particularly where homes use septic tanks with leach fields, arestraining the biodegradation capacity of subsurface microbial and geochemical systems.
The same is true for pathogenic microorganisms and pharmaceuticals being released fromanimal wastes.
On military bases around the country, landfills, burial sites, and waste handling or
storage areas on the surface often contain hazardous materials in larger quantities and ofdifferent types than those in a municipal landfill or typical industrial waste site. Firing
ranges and old ammunition dumps may contain ordnance and related materials whose
chemical components pose a vadose zone contamination hazard, as well as a safety
hazard for cleanup crews.

2"Alternatives for Ground Water Cleanup" in Technologies for Environmental Management: Summaryof a Workshop, National Research Council, 1997, p. D-111
3
Groundwater and Soil Cleanup: Improving Management of Persistent Contaminants, National
Research Council, 1999, p. 3

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1.0 Introduction

Another major consequence of preparations for national defense during the past halfcentury are sites around the nation where large-scale production or processing of nuclear
materials were accompanied by planned and unplanned releases of process wastes to thesubsurface. The Department of Energy (DOE) and its predecessor agencies haveconducted energy research and weapons development and production at facilities in 31
states and Puerto Rico. Toxic chemicals generated at these sites have been introduced
into the underlying soils and aquifers as a result of a number of historical and current
practices. At present, more than six billion cubic meters of subsurface media at 134 sites
are contaminated.4 Of this, approximately 700 million cubic meters is groundwatercontaminated with organic wastes (e.g., solvents, fuels, polychlorinated biphenyls),
Herbicides Detected in the Nation’s Groundwater
The U.S. Geological Survey is conducting the National Water-Quality Assessment (NAWQA) program tomeasure the concentrations of a large number of pesticides, pesticide transformation products, and otherchemicals in groundwater, surface water, stream sediments, and aquatic plants and animals (biota).
Eventually the NAWQA program will cover 59 major hydrologic basins across the United States,
representing 60 to 70 percent of the nation’s water use. Results from the first three years (1993-1995) ofintensive sampling in 20 of the basins were summarized in the May-June issue of the Journal ofEnvironmental Quality (Barbash et al., 2001). This summary report focuses on the frequency of detectionof seven herbicides. Six of the herbicides (atrazine, cyanizine, simazine, alachlor, acetochlor, andmetolachlor) are high-use agricultural herbicides; the seventh, prometon, is a nonagricultural herbicide.
The samples, taken from both shallow and deep wells, rarely exceeded the quality criteria for drinking
water set by the EPA. In only two samples, both from shallow groundwater, did any of these sevenpesticides exceed the maximum concentration limit (MCL). In both instances, the herbicide was atrazine,
the herbicide most frequently applied in the United States prior to the sampling period. Atrazine was also
the herbicide most frequently detecteda in shallow groundwater in agricultural areas (detected in more than
30 percent of the samples) and in deep ground water (detected in about 7 percent of samples). Prometon
was the herbicide detected most frequently in shallow groundwater in urban areas (24 percent), withatrazine second (14 percent). The authors concluded that the frequency of use of an herbicide correlateswith its frequency of detection in shallow groundwater. Statistical analyses of the data (by multiple
regression) found that frequency of use of the pesticide and its half-life in the soil under aerobic conditions
were significantly correlated with frequency of detection. However, these two variables together
accounted for less than 40 percent of the variability in detection, which the authors interpreted to meanthat additional factors are involved.
The above data show that once pesticides are applied to the soil surface, or incorporated into the upper soil
horizons, they may not remain there but can travel through the vadose zone to underlying groundwater
resources. Their fate and transport in the vadose zone is determined by a plethora of physical, chemicaland biological processes such as those discussed in this roadmap. Downward transport actually can bevery rapid. For example, the U.S. Geological Survey also detected the pesticide acetochlor in several
samples. Acetochlor was first licensed for use in the United States in 1994 and first applied in agriculturalareas in June of that year. By the following year, the NAWQA program detected this pesticide at two of
its 991 shallow groundwater sampling sites. The timing of these observations supports earlier field-scalestudies suggesting that pesticides can move rapidly through the vadose zone and appear in shallow
groundwater within a year following first application.
a

All frequencies of detection cited here are for a detection limit of 0.01 microgram per liter.

4

Research Needs in Subsurface Science, National Research Council, 2000, pp. 15 & 21

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A National Roadmap for Vadose Zone Science and Technology

radioactive waste, or mixed (chemical and radioactive) waste. Today, some 60 million
cubic meters of soil and rock within the vadose zone are contaminated, mostly withradioactive waste or mixed low-level radioactive waste.5 Cleaning up these sites is a
DOE responsibility. Where the current plans for cleanup will leave subsurface
contaminants in place, long-term stewardship of the site will be needed.
There is substantial commonality among the basic processes at work across all thesediverse circumstances of vadose zone contamination. Understanding vadose zone
processes and being able to measure, monitor, and predict the subsurface movement ofcontaminants at one site, for example a DOE site, can aid in addressing problems wherecontaminants from other human activities have entered similar subsurface environments.
This commonality in vadose zone environments, coupled with the national interests atstake in protecting our groundwater resources, calls for a cooperative, coordinated effort
among the various federal and other entities engaged in vadose zone research.
While DOE is far from being alone in “owning problems” of vadose zone
contamination, it certainly has the responsibility for some of the nation’s mostcontaminated sites. The radiological hazards present at many of the contaminated DOE
sites, as well as the sheer volume of wastes still in storage or in the subsurface, create
special, and sometimes unique, requirements for characterization, monitoring, andmodeling. The central importance of environmental cleanup and stewardship to DOE’s
mission, the scale of the effort required at some sites, and the commitment to solve theproblems place it in a leadership role among problem owners.
1.3

The Need for a Vadose Zone Science and Technology Roadmap

1.3.1

Science and Technology Roadmapping

Science and technology roadmapping is a form of strategic technology planning usedby an increasing number of companies, industries, and U.S. government agencies. The
purpose of a science and technology roadmap is to develop a common perspective on
possible future science and technology needs, in an effort to help make better researchand development (R&D) investment decisions. Science and technology roadmaps areintended to serve as pathways to the future. They call attention to the underlying scienceand applied technology needed to solve currently intractable problems, provide a
structure for organizing technology forecasts and programs, and communicate scientificand technological needs and expectations among end-users and the R&D community.
This National Roadmap for Vadose Zone Science and Technology focuses on
research that will improve predictions of fate and transport of contaminants in the vadosezone, and thus reduce uncertainty in decisions made by both problem owners andregulators. In addition to the DOE, problem owners that could benefit include theDepartment of Defense (DOD), other federal agencies, state and local entities withresponsibility for cleanup of contaminated sites, and perhaps even corporate and5

Vadose Zone Science Integration and Technical Basis (DRAFT), INEEL, 2000, p. 4

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1.0 Introduction

individual owners of serious subsurface contamination problems. The regulators include
the U.S. Environmental Protection Agency (EPA) and the various state regulatory
agencies responsible for human health and the environment. Another major focus of thisresearch is to provide better tools for communicating the scientific basis of cleanup or
stewardship decisions to stakeholders, those who are or could be affected by theconsequences of vadose zone contamination and by the decisions made by problem
owners or regulators.
1.3.2

Why the DOE Needs a Roadmap for Vadose Zone Science andTechnology

Contaminants have been detected underground at unanticipated levels far fromthe point of release. The principal driver for the DOE in initiating a roadmapping
process for vadose zone science and technology was the detection of contaminants that
had been transported through the vadose zone much more quickly than the DOE had
anticipated. Clearly, the assumption of vadose zone immobilization of contaminants waswrong. A better basis is needed for DOE’s cleanup and stewardship programs.
Recent evidence indicates that hazardous and radioactive chemicals have migrated
unexpectedly through the deep vadose zone at multiple DOE facilities. For example, atthe Hanford 200 West Area Tank Farm, cesium-137 appears to have migrated roughly 80
feet vertically below the tank through highly sorptive material which should have
prevented such migration. At Los Alamos National Laboratory, plutonium andamericium were discovered 100 feet beneath a liquid waste impoundment where nuclidetransport was believed to be dominated by sorption and thus where radionuclide
migration should have been very limited. At Sandia National Laboratories,
trichloroethane from a landfill was discovered at depths of 500 feet in an area of very dry
soil and low recharge. Near the prospective site for a high-level radioactive waste
disposal repository, in the dry desert climate of Yucca Mountain, tracer substances suchas bomb pulse chlorine-36 and tritium, were found in fractured tuff at depths of as muchas 1200 feet. These data imply unexpectedly rapid recharge along preferential pathways.
Information of this type led the authors of a National Research Council review of
DOE’s long-term stewardship program to conclude that there are “…deficiencies in ourability to make accurate estimates of subsurface contaminant behavior, especially in theconceptual understanding of this behavior to enable accurate and robust modeling.”6This conclusion echoes a report by the Government Accounting Office (GAO) on
contamination at the Hanford site. The GAO report concluded that DOE could notpredict contaminant fate and transport in the subsurface with the certainty required tomake key environmental decisions.7
DOE’s Cleanup Timetable Is Driving the Need for Long-Term Stewardship
Capabilities. Over the next 50 years DOE expects to complete cleanup activities at all of
6
7

Research Needs in Subsurface Science, National Research Council, 2000, p. 53
Nuclear Waste: Understanding of Waste Migration at Hanford is Inadequate for Key Decisions,
Government Accounting Office, 1998

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5A National Roadmap for Vadose Zone Science and Technology

its sites and move from active remediation to ensuring long-term stewardship of thesesites. Recent DOE documents define long-term stewardship as “…all activities required
to protect human health and the environment from hazards remaining after cleanup iscomplete.” 8

144

75%

108

50%

72

25%

36

Percent of Sites

100%

0%

Number of Sites

Figure 1 illustrates the timeline by which DOE anticipates completing cleanup, andcommencing long-term stewardship across 144 sites.9 While DOE estimates that only
about 123 sites will have been cleaned up and put in active or passive stewardship by theyear 2006, all 144 sites will be so by 2050. Most of these sites, including the mostcomplex ones, are located in semi-arid western states with thick vadose zones. The
timeline driving DOE’s cleanup mission, coupled with the prevalence of thick vadosezones at important sites, further dictates the need for an aggressive, accelerated program
to understand vadose zone processes and properties, develop better tools and techniques
to characterize and monitor contaminant migration and fate, and develop predictivemodels to address and assess long-term stewardship needs.

0

1989

1998

2006

2050

Completed Sites - No StewardshipCompleted Sites - Active StewardshipCompleted Sites - Passive Stewardship

Sites in Active Cleanup

Figure 1 Stewardship Activities Increase as Cleanup is Completed

8

From Cleanup to Stewardship, DOE, 1999b, p. 9.

9Ibid. p. 40. A cleanup site may be an entire facility, such as the Hanford Site, or a portion of a
facility. The magnitude of contamination and extent of planned cleanup also varies greatly from site to site,
as do the relative risks. For both reasons, Figure 1 should not be interpreted as indicating the magnitude ofcleanup accomplished or remaining to be done at a given time, nor the decrease in risk over time.

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1.3.3

The Need for a National Roadmap

Predictive models for fate and transport of contaminants in the vadose zone
leave large uncertainties. The circumstances that the DOE faces in addressing
uncertainties about contaminant movement in the vadose zone at its cleanup sites apply invarying degrees to other owners of vadose zone contamination problems and toenvironmental regulators. Our current ability to predict and optimally manage fluid flow
and contaminant transport processes in the vadose zone is limited by inadequate
understanding of processes that typically incorporate geological, hydrological, chemical,
and biological processes and properties. There is a general lack of methodologies toadequately represent water flow and contaminant transport processes and properties inhighly heterogeneous media across multiple spatial and temporal scales. For example,
we are unable to measure state variables and parameters accurately, reliably, and in atimely fashion. We do not know how reliably the conceptual models for these processes,or the data used to define bounding conditions and parameters for a specific site,
represent the actual processes and properties in the vadose zone.
These uncertainties and knowledge gaps are exacerbated by our general inability tosimulate even known processes realistically, given limited data, or to simulate assumed
processes with little data. In part, these simulation difficulties stem from the nonlinear
parametric relationships that govern flow and transport through the vadose zone. In part,
they are due to computational intractability posed by limitations in available hardware
and software. Taken together, these various aspects compound the uncertainty within themodels themselves. Simulation-induced uncertainties potentially amplify the gaps in our
fundamental understanding of the processes being modeled and the uncertainties in our
measurements of key properties. The development of the necessary process level
understanding requires substantial advances in both instrumentation and in modelingcapabilities.
No acceptable technical basis exists for regulatory oversight of the vadose zone.
At many contaminated sites, contaminants have been released to the land surface, or haveescaped gradually from buried containment systems, over a period of decades. Even at
priority cleanup sites, leaking underground containers and long-buried wastes willcontinue releasing contaminants to the vadose zone for decades to come. For example, atthe DOE sites with the largest quantities of waste, releases to the vadose zone willcontinue as a result of historical activities, planned containment, storage of new wastes in
newly designed landfills, imperfect closure of contaminated buildings, abandoned
contaminated subsurface piping, abandoned dirty facilities, and unexpected (as opposed
to planned) future waste releases. This last category includes, for example, spills andleaks that will occur at facilities that will remain operational for the next several decades,
prior to final closure. Not all of the contaminants can be removed from the surface orsubsurface, and not only because the cost of removal is huge or because it is technicallyimpractical to remove wastes hundreds of feet deep in highly heterogeneous media. In
some circumstances, disposal of huge amounts of excavated materials containing low
levels of contamination would simply shift the problem elsewhere.

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A National Roadmap for Vadose Zone Science and Technology

The inability to explain basic subsurface processes fully and predict contaminant fate
and transport in the vadose zone accurately has led some regulators to fall back on themost conservative expectations: all contaminants will move rapidly through the vadosezone to the groundwater. For example, in the late 1960s the time for carbon-14 to travelfrom the surface to groundwater at a site near the Idaho National Engineering andEnvironmental Laboratory (INEEL) was estimated at 80,000 years. Based on more
recent measurements, the estimates are closer to 50 years.10 Similar foreshortening oftravel time predictions for other contaminants has also occurred. Despite these dramaticchanges in expectations, many science and technology providers assert that theuncertainties in current predictions are just as great as the uncertainties in predictions
made three decades ago.
To make regulatory and operational decisions regarding these long-term andcontinuing sources of contamination, the following questions must be addressed:
1.

What quantity of existing contaminants must be removed?

2.

How much residual waste can be placed in onsite landfills?

3.

What kind of biogeochemical barriers can be used to enhance long-term
entrainment (compared with hydraulic containment using a cover over thelandfill)?

4.

Will containment be necessary over the long-term, and if so, what kind?

5.

What long-term geochemical transformations are expected in the containment
facilities?

The research identified in this roadmap is necessary to provide the scientific foundation
for answering those questions.
Uncertainties in predictions and in the basis for effective action create publicdistrust and misallocate limited resources. The uncertainties in our understanding, ourdata, and our ability to model contaminant movement in the vadose zone have two
additional consequences: erosion of the public trust and greatly increased public expense.
For example, at some DOE sites with thick vadose zones having low permeability, awaiver of groundwater monitoring in favor of vadose zone monitoring is an option under
the Resource Conservation and Recovery Act (RCRA). However, regulators are
reluctant to grant this variance because of uncertainties in the reliability with which
vadose zone instrumentation can detect contaminants. Consequently, deep and oftenmuch more expensive groundwater monitoring is required.
Moreover, reliance on deep groundwater monitoring sidesteps the need to detect
contaminants in the upper vadose zone, where their presence might trigger shallow soil
remediation actions rather than expensive, difficult attempts to isolate and remediate10

For a further discussion of predicted contaminant travel times and how they have changed, see
Research Needs in Subsurface Science, National Research Council, 2000, p. 30

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1.0 Introduction

contaminated groundwater at great depth. Finally, because of the large uncertainty in ourability to predict migration through the vadose zone and potential risks to groundwater
users, engineered remedial measures are often designed with an excessive margin ofsafety applied to multiple design factors. These compounded safety margins in designs
result in costly facilities—although the adequacy of the design may still be uncertain.
1.4

A Vision for 2025

Over the next few decades, dramatic and fundamental advances in computing,communication, electronics, and micro-engineered systems will transform many of thescientific and technical challenges we face today. For example, analytical systems thatonce would have required rooms of complex and fragile equipment are now located on a
microchip. The computing power once reserved to put a man on the moon is now far
surpassed by the power in a personal home computer. The technology trajectory
expressed by Moore’s Law, which predicts that microchip density doubles every 18
months, suggests that computing power may undergo more than a thousand-fold increase
within the next 15 years.11 Extended to the year 2025, this hypothesis implies thatcomputing power may increase by more than a hundred-thousand-fold. With advances
like these becoming commonplace, one can envision the following by the year 2025.
Our fundamental understanding of vadose zone properties and processes will be
sufficiently developed, tested, and verified that issues of scientific uncertainty exert far
less influence on public debates over interventions or on regulatory procedures toimplement public policy.
In-situ and remote monitoring methods such as real-time detection andquantification of liquid and contaminant flow in fractures are widely used—and routinely
accepted by problem owners, cleanup managers, regulators, and stakeholders—as analternative to in situ sampling methods, such as groundwater monitoring. Using ultrasensitive monitoring capabilities, investigators know whether liquid and contaminantmigration is occurring within specific fractures or media.
A new generation of microscopic sensors, the size of grains of rice, can takesimultaneous multichannel measurements (e.g., chemical species detection or pressure,temperature, pH and/or electromagnetic measurements) inexpensively and in real time.
These sensors are small and inexpensive enough to inject into the material being
investigated.
Vadose zone simulation and visualization capabilities compare in their complexity,
speed, and accuracy to those used to model nuclear weapons systems and explosions,weather and climate, or molecular processes in biology. Access to these predictive and11“Moore’s Law” refers to the observation made in 1965 by Gordon Moore, co-founder of Intel, thatthe number of transistors per square inch on integrated circuits had doubled every year since theintegrated circuit was invented. Moore predicted that this trend would continue for the foreseeable
future. In the years since Moore made his prediction, this pace has slowed a bit, but component
density has doubled approximately every 18 months.

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9A National Roadmap for Vadose Zone Science and Technology

interpretive tools revolutionize the way researchers, cleanup managers, and regulators
think about the vadose zone and contaminant problems. These tools are routinely used toprepare site-wide assessments, with predictive scenarios for alternative courses ofintervention, before major decisions on cleanup and stewardship.
1.5

The Context of Previous Vadose Zone Work

This roadmap represents the next phase in the historical evolution of technical andphilosophical approaches to the vadose zone. The specific study of vadose zonehydrology is quite new, in fact the first graduate courses in this field were offered only inthe early 1980s—just 20 years ago. When O. E. Meinzer wrote about the vadose zone in
the first half of the twentieth century, he referred to it as “no man’s land” because of thelack of knowledge about its part in the hydrologic cycle (Looney and Falta, 2000, p. xix).
Before 1980, most of those interested in studying the subsurface followed one of twopaths, focusing either on groundwater hydrology or soil science. Groundwater hydrology
has traditionally been a discipline of specialists trained in aquifer mechanics, wellhydraulics, and groundwater basin management, mostly interested in groundwater supply
issues. Soil physicists, whose academic discipline does include the study of water
movement in the vadose zone, have focused on problems in irrigation and drainage of
agricultural land. These fields of study evolved independently for the most part, althoughgroundwater hydrologists often learned from the soil physicists and agricultural engineers
to solve similar problems, recognizing for example, that the mathematical solution forflow to a drainage canal was similar to that for flow to a stream.
Today, however, driven in large part by the explosion in regulations to protect
groundwater quality, hydrogeologists and soil scientists together are facing problems
involving the flow of chemicals through the vadose zone to aquifers. The surge inenvironmental applications of soil science has led to interdisciplinary research sponsoredby a wide range of state and federal agencies (Loaiciga et al., 1997; DOE, 1999a). Crosstraining and cooperative research across multiple disciplines including hydrogeology, soil
science, civil and environmental engineering, and petroleum engineering has been
increasing dramatically, and a new field of vadose zone hydrology is now coming into its
own. Major review articles and technical monographs on vadose zone hydrogeology andthe flow and transport of contaminants in the vadose zone are proliferating.
In the late 1990's, DOE undertook a major review of the state of the art associatedwith the vadose zone hydrogeology. This activity resulted in the publication of Vadose
Zone, Science and Technology Solutions (Looney and Falta, 2000). This two-volume
compendium, which built upon four national meetings on various aspects of the vadosezone, was organized and led by DOE’s Savannah River Office. Within its 1600 pages, it
identifies both the state of practice and the state of science in vadose zone
characterization, monitoring, and modeling. Further, the national meetings and thecollective efforts to assemble the compendium gave birth to a series of recommendations
on filling gaps in our knowledge of vadose zone hydrology. As Vadose Zone, Scienceand Technology Solutions was being assembled and readied for publication in 1999–

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1.0 Introduction

2000, science and technology (S&T) roadmaps for individual DOE sites were also being
prepared, for example at the Hanford Site and INEEL.
As a next step in DOE’s effort to provide a better basis for its decisions onenvironmental cleanup and stewardship, DOE directed INEEL in 1999 to lead thedevelopment of an S&T roadmap identifying vadose zone research needed over the next
25 years. The scope of this roadmap was specifically restricted to understanding basic
processes in the vadose zone and to techniques and technologies for characterizing,measuring, and modeling vadose zone processes and properties. Unlike the Vadose Zone,
Science and Technology Solutions review or the site-specific S&T roadmaps, thisroadmap effort would not address remediation approaches. In March 2000, an executive
committee was formed to address the science and technology required for characterizing,
monitoring, and modeling subsurface contaminant fate and transport. Over the next year,
this committee and four roadmapping workgroups comprising sixty-two representatives
from DOE, its national laboratories, other U.S. government agencies, universities, andindustry discussed and agreed upon S&T capabilities that would transform the scientificbasis for making decisions involving the vadose zone.12 The resulting roadmap,
presented in the following pages, delineates the critical research that must be conducted
over the next 25 years to realize the vision of a sound scientific basis for making public
policy and regulatory decisions. It also provides a structure for understanding the context
of decisions being made on cleanup and long-term stewardship by DOE and thecomponents that contribute to improved scientific input to these decisions with respect tothe vadose zone.
If successful, the research described in this document will advance the state of the art
in vadose zone characterization, monitoring, and modeling science and technology. To
support the complex-wide needs of DOE, described above, as well as the needs of otherowners of vadose zone contamination problems, and the regulators and stakeholders towhom they answer, these advances in the state of the art must make their way into
advances in the state of practice. The work groups that developed this roadmap haveemphasized pathways for this critical transformation of research results into practicalresults.
Creating a better scientific foundation for making both near-term remediation andwaste handling decisions and long-term stewardship decisions regarding the managementof contaminated vadose zone sites will require: 1) an enhanced understanding of basic
subsurface processes; 2) adequate data on the properties of fluids and media that affectflow and transport in the vadose zone, the extent and character of existing contamination,and the ability to monitor it effectively; and 3) the ability to translate this understanding
and data into new predictive models that can reduce the technical uncertainty inenvironmental management decisions. All three of these essential strands are woven
through the fabric of the roadmap pathways and the supporting narrative.

12

A complete list of participants is provided in Appendix A. The original sets of research goals
formulated by the work groups are listed in Appendix C, which also indicates the roadmap activity, task, or
status point corresponding to each research goal.

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11A National Roadmap for Vadose Zone Science and Technology

Activities, tasks, and status points are used to define roadmap paths. Section 2
describes the research and application activities to improve the understanding of basic
physical, chemical, and biological processes and properties, as well as improving themodeling, measuring, and monitoring of fluid flow and contaminant transport. Section 3
identifies and discusses activities, tasks, and status points for cross-cutting issues, such as
coupled processes, scaling, measuring and reducing uncertainty, and the integration andvalidation of characterization, monitoring, and assessment tools at the system (site-wide)level.
Each research activity outlined in Sections 2 and 3 represents an area for which
critical research objectives and application needs can be clearly stated. For mostactivities, specific tasks and status points along the path of the activity are identified, andtheir relevance to achieving the activity’s objectives is explained. A task represents work
contributing to an ongoing activity but having a definite endpoint. The task endpoint canbe considered the final status point for that task, indicating completion.
Supporting capabilities and infrastructure are needed to achieve research andapplication goals. Section 4 focuses on the infrastructure and capabilities required toaccelerate progress along the activity pathways identified in Sections 2 and 3. In many
instances, early results from these activities, particularly application status points, areprerequisites for phases in developing a supporting capability or infrastructure element.
These capabilities and supporting elements, in turn, enable and accelerate the moreadvanced research activities. Thus, there is an iterative synergism between the activities
in Sections 2 or 3 and those in Section 4. This synergism will be discussed further in
Section 5.
The roadmap is structured into near-term, mid-term, and long-term time
horizons. For this initial effort in defining roadmap paths, the work groups used threetime horizons for tasks and status points. For the near-term horizon, the work groups
aimed at efforts that could be completed in about 4 years (within a year or so of 2005).
For a mid-term horizon of about a decade, the arbitrary time point was 2010. A longterm horizon of two to three decades was denoted by a time point of 2025. These
arbitrary year dates should be understood as approximate markers for the three time
horizons, near, mid, and long term, rather than as precisely scheduled milestones. As theroadmap evolves and the tasks and projects within an activity become better defined,
more specific timing of results from the roadmap activities will become possible.
The activities and associated tasks and status points are listed in Sections 2 through 3
immediately following the narrative text that explains their value and the gaps they aremeant to address. A complete table of all the recommended roadmap activities is shownin Appendix B.
An integrated, cross-disciplinary approach is essential to rapid progress. As
work group members pondered and debated the gaps in understanding of processes andproperties; the shortcomings of existing measurement devices, techniques, and systems;
or the inadequacy of process models and integrated site models as predictive simulation
tools, a common theme emerged. To make progress and overcome identifiable

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1.0 Introduction

limitations, it would be necessary to integrate geological, hydrologic, chemical, andbiological perspectives, research and testing methods, tools, and data. Creating andworking within this geological-hydrologic-chemical-biological (GHCB) framework
emerged as a fundamental change from the discipline-specific approaches that haveprevailed in past vadose zone research.

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2.0

PHYSICAL, CHEMICAL, AND BIOLOGICAL ASPECTS OFVADOSE ZONE FLOW AND TRANSPORT

Advances in understanding fluid flow and contaminant transport and transformation
processes in the vadose zone are closely connected with advances in characterizing andmeasuring subsurface properties and processes. Advances in both understanding andcharacterizing/measuring the subsurface system often follow from advances in numericalmodeling and computational capability. In turn, the conceptual models on which
numerical modeling is based depend on understanding the subsurface properties andprocesses. And each simulation run depends on data, derived from measurement andcharacterization, which the numerical models require as input.
To this interdependence among theory (understanding), characterization andmeasurement (factual description), and prediction/integration (numerical modeling) as
aspects of one interlocking scientific process must be added the multidisciplinary
character of what is to be understood, described, monitored, and modeled. As noted in
the Introduction, the processes that occur in the vadose zone do not respect the traditional
disciplinary divisions between geology, hydrology, soil science, chemistry, and biology.
Scientists still tend to think in terms of a “coupling,” within a geologic setting, ofphysical (i.e., hydrogeologic) processes, a chemical transformation, and biologicalactivity. In fact, there is just one integrated GHCB system. Investigators trained in one or
another specific discipline initially focused on limited aspects of that system to begin
understanding it. However, to understand the entire system, and to simulate it
realistically enough to produce reliable predictions, an integrated GHCB perspective
must be used.
These interdependencies across research methods and disciplines mean that any
attempt to set priorities for work in one area soon runs into the work priorities in otherareas on which it depends. For the purpose of presentation, some initial separations must
be made, although the necessary interconnections must eventually be added. This section
covers research needs by basic disciplines. Section 3 outlines the research needed toaddress the combinations of geological, hydrologic, chemical, and biological aspects
found in real vadose zone processes.
This section begins with a context-setting discussion of flow and transport processes
in the vadose zone, followed by a brief look at the basic activities required to begin
assembling a GHCB framework. (The GHCB framework will be taken up again in
Section 4, where it is presented as an interdisciplinary infrastructure requirement.) The
next three subsections present research needed to understand, measure, and model thebasic physical, chemical, and biological processes and properties of vadose zone systems.
The section ends with research needed on three special topics crucial to understanding
flow and transport in the vadose zone. These are colloidal formation and transport,
multiphase flow and transport, and unstable processes. Within each subsection, activities
needed to understand and model the basic processes are presented first, followed by
activities required to possess adequate data and monitoring capabilities.

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142.0 Physical, Chemical, and Biological Properties

As noted above, these areas of research are interdependent. Mid-term and long-term
progress in understanding and modeling a process often depends on near-term advancesin characterization and monitoring techniques and technology, and vice-versa.
In the sections on measuring and monitoring basic processes, the intent is not to
produce a comprehensive review of existing methods. Rather, the intent is to map thescience and technology required to advance the existing methods and develop new ones.
For a review of existing methods to measure and monitor existing process, thecharacterization and monitoring work group selected several key review papers andhandbooks (Scanlon et al., 1997; Ward, 1990; Wilson, 1982, 1983; Wilson et al., 1995).
2.1

The Importance of a Geological, Hydrologic, Chemical, andBiological Framework

A significant number of subsurface environmental problems involve fluid flow andsolute transport in the vadose zone. A key component in assessing contamination hazards
and designing remedial actions is the development of flow and transport models. Thesemodels are developed to work within a specific physical framework that accounts forappropriate processes at the appropriate scale. The physical framework must include all
the relevant geological, hydrologic, chemical, and biological parameters and processes inthree-dimensional space, while taking into account changes in these processes andparameters over time and space. These relationships between the geologic, hydrologic,
chemical, and biological parameters and the processes linking them constitute the GHCB
framework, as that term is used in this report.
Geologic processes of deposition and diagenesis have resulted in highly variablesubsurface environments at the priority sites of subsurface contamination across thenation, including those in the DOE complex. The established view is that the hydrologic
parameters governing the magnitude and direction of water and vapor flow in theseenvironments are related to a combination of geological structure and post-depositional
processes, as is the spatial distribution of mineralogical features. The presence of waterand the distribution of dissolved contaminants and nutrients depend on this spatial
distribution, in combination with external driving forces (e.g., precipitation).
In vadose zone environments, geological, hydrologic, chemical, and biological properties
and processes depend on the system state. The energy of water in contact with the porous
medium depends on the moisture content. The geochemical and biologic environment isa function of the water distribution and the geologic character of the medium, and thehydraulic conductivity is a function of moisture content. It is also true that the system
state at any given time and place is a function of the physical, chemical, and biologicalprocesses that have occurred up to that time.
The properties and processes discussed in the remainder of Section 2 constitute apartial list of state variables and system parameters used to describe flow, transport, andtransformation processes in the vadose zone. In general, however, the state variables(e.g., moisture content, pressure head, temperature, and contaminant concentrations) or
fluid and medium properties (hydraulic conductivity and solid phase mineralogical or

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15A National Roadmap for Vadose Zone Science and Technology

exchange properties) needed to characterize the system state fully in space and timecannot be easily determined by either direct in situ or other means. Often, they must be
inferred from indirect measurements. Where these state variables or properties can beobtained directly, the measurements are representative of a wide range of support
volumes, and are typically collected at various network scales. Obtaining representativevalues for processes and properties poses an extreme challenge, as does developing
relationships for interpolating between measured and inferred properties or parameters.
The long term goal in building a GHCB framework is to develop a quantitative
relationship between the geologic nature of a specific site and the parameters andprocesses that affect contaminant fate and transport at that site. Developing quantitative
GHCB models is necessary for numerical simulations, which are used to understand therelationships between parameters and processes. These simulations of a specific vadosezone environment as a system will ultimately be used for predicting future evolution of
the system, as well as understanding its past and current states.
The critical element of infrastructure for developing and making available themultidisciplinary data to support a GHCB framework is referenced here as a GHCB
virtual library. The activities to develop and make accessible a GHCB virtual library aredescribed in Section 4.1.1. However, Sections 2 and 3 can be viewed as providing an indepth analysis of the work required to provide the understanding, the data, and theinterpretive and predictive tools to populate a GHCB framework for sites with vadosezone contamination.13
2.2

Physical Description of Flow and Transport Processes

2.2.1

Understanding Basic Physical Properties and Processes

Our current ability to understand contaminant transport in the vadose zone, predict
fluid flow and contaminant transport processes, and manage those processes optimally islimited. For example, we lack adequate understanding of many fundamental interactions
between the solid, liquid, and gaseous phases in contaminated subsurface media. Equallyor more important, methodologies are lacking to represent flow and transport processes
and parameters across different spatial and temporal scales. The necessity forunderstanding scale differences is a consequence of the overwhelming heterogeneity of
the hydraulic and transport properties of the subsurface. Macroscopic continuum
approaches that work well for representing flow and transport processes at relatively
large spatial scales in homogeneous media may critically misrepresent processes at
smaller scales in highly heterogeneous granular or fractured porous media.
Activity PH1. Assess the importance of fluid flow and chemical transport processes
and subsurface properties relevant to site characterization, remediation, andlong-term stewardship.
13

Appendix B contains a complete list of all the S&T roadmap activities presented in Sections 2
through 4.

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2.0 Physical, Chemical, and Biological Properties•

Near-Term Status Point. Subsurface properties (e.g., gravitational, pressure,temperature, and chemical gradients) of importance to fluid flow and chemicaltransport at contaminated vadose zone sites have been identified and assessed.

There are many obstacles to describing fluid flow and solute transport more
realistically and implementing these process descriptions in predictive models. Improved
descriptions are needed for many pore-scale processes and associated liquid-solid andliquid-gas interactions. Driving forces that affect flow and transport (especially chemical
gradients) need to be studied. Also needed are more general constitutive relationships
among fluid, geochemical, and solid phase parameters and variables. For example, moregeneral representations are needed of two-phase air-water hydraulic properties inunsaturated media under extremely dry conditions.
Activity PH2. Design and conduct laboratory and field experiments to resolve
critical gaps in understanding fluid flow and chemical transport processes in
granular media. The criticalness of gaps is to be assessed by relevance toenvironmental restoration and long-term stewardship missions of the DOE
and other agencies.
•

Near-Term Status Point. Critical gaps that can be answered within a decadethrough laboratory and controlled field experiments have been identified andprioritized.

•

Task Beginning Near-Term with Mid-Term Endpoint. Design,
implement, and analyze results of laboratory and field experiments for theprioritized critical gaps.

Improved process-based descriptions of flow and transport in macroporous soils andunsaturated fractured media represent an especially significant challenge. More realistic
representations are needed of the pore-space geometry of such structured media.
Emerging geological, pedologic, and topological characterization techniques could be
used to develop these representations. In parallel with this effort, improved descriptionsof matrix-fracture interactions of structured media must be developed.
Activity PH3. Improve process-based understanding and models for flow andtransport in macroporous soils and unsaturated fractured rocks.
•

Task with Mid-Term Endpoint. Develop realistic representations of porespace geometry of, and fluid flow in, structured media using geological,
pedologic, and topological characterization techniques.

•

Task with Mid-Term Endpoint. Develop and implement improved
descriptions of matrix-fracture interactions.

•Task with Mid-Term Endpoint. Develop general constitutive relationships
for both granular and structured media.

•

Task with Mid-Term Endpoint. Develop pore network and other models
based upon appropriate equations (e.g. Navier-Stokes), and devise methods
for upscaling processes and/or properties from sample to formation scales.

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Task with Long-Term Endpoint. Incorporate solid surface heterogeneity(pore and sample scale) with detailed hydrodynamics into solute transportmodels (to model opportunity times for reactions, streaming potentials, andother processes or variables).

The propagation of physical processes across scales and the associated prediction of
uncertainty affects all modeling activities in earth systems. Not only is it necessary tomatch the proper model to the scale of interest, useful simulation tools must be able tomove from one scale to another without losing key elements of the basic processes
involved. A related challenge is to both recognize and incorporate significant data at
different scales within a robust conceptual model of key flow and transport processes
operating at the different scales relevant to site remediation, containment, and long-term
stewardship decisions. Meeting this challenge will require methods for efficientassimilation of different types of data having different spatial and temporal resolutions,different geostatistical properties, and different measurement errors.
It is important to recognize the need for proper data at a range of scales. Applying
models to real-world situations will require hypotheses about the main processes
operative at individual sites and estimates of site-specific properties. These processes
and parameters include: (1) hydraulic and solute transport parameters such as capillarypressure saturation curves, conductivities of liquids and gases as a function of phasesaturation; and various diffusion coefficients, tortuosities, and dispersivities; (2) fluid
properties such as density, viscosity, enthalpy, vapor pressure, surface tension, andwetting angle; (3) thermal properties such as heat capacities and the saturation dependentbulk thermal conductivity; (4) biogeochemical parameters such as thermodynamic andkinetic data for homogeneous and heterogeneous reactions involving aqueous andgaseous species, minerals, and mineral surface areas; (5) initial and boundary conditions
for fluxes, temperature, pressures, fluid compositions, aqueous and gas phasecompositions, and mineral concentrations; and (6) fluid and chemical sources and sinks.
Activity PH4. Develop methods for modeling scale-dependent properties andprocesses and for assimilating data from different scales into these models.
•

Task with Near-Term Endpoint. Develop and implement improved models
for evapotranspiration and root water uptake as a function of water stress andother factors.

•

Task with Near-Term Endpoint. Develop process-hierarchical approaches
for describing and modeling controlling processes (e.g., models of increased
complexity for flow in structured media, or increasingly sophisticated processbased approximations for gaseous transport or the flow of non-aqueous phaseliquids).

•

Near-Term Status Point. Methods have been developed to quantify spatial
variability in flow and transport parameters, fluid properties, thermal
properties, and biological and chemical reactions.

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2.0 Physical, Chemical, and Biological Properties•

Task with Mid-Term Endpoint. Investigate potential of collecting/inverting
multi-scaled data to provide information about variability as a function ofscale.

•

Task with Mid-Term Endpoint. To understand how different measurement
methods scale from one level of support to another, experiment withmodifying the acquisition parameters for a certain type of method to sample
different scales of variability.

•

Mid-Term Status Point. Methods have been developed for measuringphysical processes and properties and their uncertainties across different
scales. The multi-scale data from these methods can be assimilated into
process models in which the properties and processes can be propagated (insimulations) as, for example, governing equations, driving forces, and/or
media properties.

•

Mid-Term Status Point. Linkages between relevant small-scale processes
and properties with larger-scale flow and transport behavior have been
identified for cases where no simple upscaling is possible.

•

Long-Term Status Point. Microbiology modules are incorporated into
physical models of solid-gas-liquid environments.

•

Long-Term Status Point. Solid surface evolution due to biogeochemical
reactions (precipitation-dissolution, reduction-oxidation, and other reactions
that can change solid-phase geometry and density of exchange sites) has been
incorporated into transport models necessary for long time-scale simulations.

•Long-Term Status Point (also a status point for Activity PH3). Models forunsaturated flow and transport in different types of porous media have beendeveloped that are both process-adaptive and scale-adaptive. These models
invoke the appropriate processes at the appropriate scale and employ thecorresponding transport and hydraulic properties.

Our knowledge of basic vadose zone flow and transport processes has advanced
considerably over the past several decades. This progress is reflected in the many
thousands of papers being published on vadose zone processes annually in dozens ofscientific journals. Unfortunately, much of this knowledge is not being used to advantage
in the management practices for remediation and stewardship currently being used bymany federal agencies, including DOE. In the near term, the nation’s capabilities tosolve problems involving contamination of the vadose zone and groundwater can besignificantly enhanced by narrowing this gap between the state of the art and the state ofpractice. For this reason, known models and solutions need to be assessed for adequacy
in representing flow, geochemical, and microbial transformation processes relevant to sitecharacterization and environmental remediation and stewardship. Critical gaps need tobe identified and resolved to further the understanding of these processes, focusing on
issues most relevant to the protection of irreplaceable soil and water resources.

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Activity PH5. Improve the state of practice in flow and transport models used bygovernment agencies for vadose zone contamination simulations, beginningwith DOE.
•

Near-Term Status Point. DOE flow and transport prediction models andsolutions have been updated by incorporating known models/modules with amore sound physical-chemical basis.

•

Task with Mid-Term Endpoint. Integrate critical elements of chemistry andmicrobial activity in models for liquid flow and solute transport.

2.2.2

Measuring Physical Properties and Processes

Characterization and monitoring of flow and transport properties and processes in thevadose zone includes measurement of state variables such as moisture content, soil water
potential, and temperature, and the description of flow and transportation in disturbed andundisturbed media. Flow and transport description includes measuring hydrologic
parameters such as permeability and porosity as a function of time and space, the flowarchitecture including fractures, and the suite of methods (e.g., tracers) used to map the
subsurface.
2.2.2.1

Moisture Content, Matric Potential, and Temperature

Methods for assessing hydrologic state variables are primarily invasive and have not
evolved much in several decades. Key areas for development include improving
robustness; easing emplacement costs and containment system concerns; and simplifying
data communication, fidelity, and manpower requirements.
Among the most important state variables requiring characterization in the vadose zone
are water content, matric (soil water) potential, and soil temperature.
Water content, the mass of water held in a porous medium, is often reported aspercent saturation. Water content measured on a volumetric basis (volume of water
per volume of voids) is needed to make predictions of contaminant transport throughthe vadose zone and for mass balance calculations.
Matric potential is the energy status of water in soil or other material resulting fromits presence in the gravitational force field, capillary and surface forces, and from thepresence of mineral salts. Soil water potentials are needed to determine gradients forwater flow.
Soil temperature affects many processes such as microbial activity, water and vapor
movement, and geochemical reactions.
Activity PH6. Develop, improve, and confirm methods for measuring basic
hydrologic properties.
•

Near-Term Status Point. Moisture content, matric potential, andtemperature measurements are no longer a major source of uncertainty for

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2.0 Physical, Chemical, and Biological Properties

site-wide monitoring and modeling. Monitoring approaches for theseproperties are robust enough to cover long-term stewardship responsibilities.

2.2.2.2

Distribution of Flow and Migration (Perturbed and Unperturbed)

Mapping water distribution and tracking water migration in the vadose zone areamong the most important tasks for noninvasive monitoring. Tracking water movement
may reveal fundamental formation parameters such as porosity and permeability.
At present, water saturation within the vadose zone is poorly determined fromgeophysical measurement; time-lapse studies of water movement have done better. Bothelectrical and seismic techniques typically have good sensitivity to water saturation in thevadose zone, but there are many other competing factors that make isolating the effects ofwater saturation difficult. This suggests that research should be focused on approaches
using several independent measurements. Other promising technologies include spectral
induced polarization, borehole radar or ground penetrating radar, spectral inductive
electromagnetic measurements, and microgravity measurement.
The ultimate research goal is to provide capability to map water distribution and track
flow within a volume of interest in an arbitrary geology, using cost-effective noninvasive
technology. The status points listed below for this research activity represent increments
of progress toward this goal. Achieving the long-term status point will require both an
improved imaging technology and better integration with hydrologic and geologicalinformation.
Activity PH7. Improve the capability to track subsurface fluid flows with increased
precision, over larger areas, and at greater depths underground.
•

Near-Term Status Point. Improved resolution and decreased uncertainty.
Example, fluid movement (such as in an infiltration event) in a 10 m X 10 m
area, at depths up to 100 m, can be tracked to a precision of 10 percent.

•

Mid-Term Status Point. Further improvements in resolution and uncertainty
reduction. Example: fluid movement in a 50 m X 50 m area, at depths up to
100 m, can be tracked to a precision of 5 percent.

•Long-Term Status Point. Greatly improved resolution and reduced
uncertainty. Example: a three-dimensional pulse of water (2 m X 2 m) can be
identified to a precision of 2 percent at depths up to 100 m.

2.2.2.3

Using Tracers (Natural and Introduced) to Determine Flow andTransport

Characterization and modeling of subsurface flow and transport is critical forevaluating the current distribution of subsurface contaminants and predicting future
migration. Natural and anthropogenic tracers can be used to determine directions andrates of transport, assess flow processes, and validate numerical models.

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The subsurface distribution of contaminants can be thought of as a large-scale applied
tracer experiment. However, it is often difficult to reconstruct the location and timing ofcontaminant releases. The research challenge is to provide a consistent system modelthat optimizes the use of tracers, extracting as much information about the subsurface aspossible while providing data to complement information from other approaches.
Activity PH8. Optimize the use of natural and anthropogenic tracers for determining
directions and rates of transport, assessing flow processes, and validating
numerical models.
•

Task with Long-Term Endpoint. Develop, test, and confirm the inverse
process of using tracers to estimate fluxes and ages of pore water. Include
methods to propagate uncertainties in tracer measurements to obtain
uncertainties in calculated fluxes and ages.

•

Long-Term Status Point. A variety of tracers are available for use inlocating contaminants, establishing the role of surface boundary conditions in
specific subsurface environments, and obtaining point estimates of fluxes andages.

2.2.2.4

Quantification of Flow in Fractures

Rock fractures and soil micropores often serve as preferred pathways for migration ofcontaminants. In unsaturated fractured rock, fractures almost always represent zones ofpermeability that are different from normal, unbroken rock (e.g., tuffs, basalts, andgranites) or undisturbed materials (e.g., alluvia and colluvia). Consequently, the physicalproperties of fractures must be known, to evaluate flow regimes, perform modelingcalculations, and plan remediation where fractured rock strata are present in the vadosezone.
The spatial distribution, trace length, and connectivity distribution of fractures areoften inferred using cores, outcrop data, hydraulic tests, seismic and electromagnetic
surveys, borehole logging tools including borehole cameras, temperature logs, and flow
meters (Long and Witherspoon, 1985; Paillet, 1997). Such efforts to characterizefractures are largely used to understand and model groundwater flow. Major exceptions
are the work to characterize fracture networks within the vadose zone at the Yucca
Mountain Project in Nevada and the Apache Leap site in Arizona.
Flow in Fractures. For both groundwater and vadose applications, a key challenge is
to capture the spatial variations of the fractures or fracture systems efficiently, regardlessof local borehole stress conditions. A crucial criterion for successful fracture
characterization is distinguishing between the presence of any or all fractures and thesubset of fractures that serve as conduits or barriers for fluid migration. Another key
challenge is to identify actual flow in fractures and in turn identify contaminants in thefluid flowing within the fractures. These goals for long term research represent asignificant challenge because little remote sensing research, either in-situ or in thesubsurface, has been done on flow detection and flow characterization within fractures.

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The ability to detect and determine the nature of fluid in fractures from surface orborehole measurements is important in many geological environments, but especially soin hard rock. In hard rock environments, fluid contaminants are stored and migrate
principally in the fracture network. Currently no surface methods can reliably detect
fluid in fractures in the vadose zone. There have been reported successes of crosshole
radar measurements detecting injected tracer fluid in fractures, but there are no cases
where in situ fluid in fractures has been detected or imaged. The best candidate
technologies appear to be seismic techniques and radar, which provide both the required
range and resolution. Other interesting possibilities include geochemical methods,
electrical and electromagnetic techniques, and logging techniques. The goal is to detect
the presence of fluid in fractures and to quantify the amount in real time from the surface.
Geophysics Focused on Fractures. Crosshole geophysical data are currently used todetermine whether fractures are present, as well as to identify water-conducting fracture
pathways. Crosshole geophysical techniques may also provide information about thepresence and nature of fractures away from the borehole wall. Surface geophysicaltechniques include the use of P-wave reflection to detect shallow faults with offsets as
small as two or three meters. A potentially useful seismic method is diffraction
enhancement; research on relatively high frequency (10–100 Hz) surface waves in multichannel analysis of surface waves suggest that faults and joints might be routinely
detectable with surface waves. Other general issues related to geophysical fracture
characterization include fracture imaging and sensor development, understanding
geophysical responses to fractures, and integrating interpretations to address scaling.
Activity PH9. Develop capability to detect the presence and movement of fluid in
fractures and fracture networks.
•

Near-Term Status Point. The presence of fluid in individual fractures can bedetected in some cases.

•

Task with Near-Term Endpoint. Quantify the relationships among the most
likely geophysical methods or combinations of methods that will provide
fracture diagnostics.

•

Mid-Term Status Point. Contaminant fluid in fractures can be detected inmost cases.

•

Task with Mid-Term Endpoint. Discover and quantify new relationships
between surface geophysical measurements and fractures, so that fractures a
few centimeters across at depths of 10 meters can be routinely mapped.

•

Long-Term Status Point. Contaminant fluid in fractures in real time can bedetected and quantified from the surface or in boreholes.

•

Long-Term Status Point. Low-cost, automated, and reliable geophysicaltechniques are available for mapping fractures immediately at the field site,
without delays for processing or analysis.

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2.2.3

Integration of Geophysical and Hydrologic Data

Many of the problems and initial costs of subsurface remediation come from field sitecharacterization. Three-dimensional information about the heterogeneous subsurface isneeded in order to identify the key controls on flow and contaminant transport processes.
It is widely recognized that natural heterogeneity and the large spatial variability ofpermeability predominantly control the flow field, and hence transport. Moreover,natural heterogeneity exhibits variability over a wide range of scales and is difficult tocharacterize using only one-dimensional borehole data.
Geophysical data can complement direct borehole characterization data by providing
multidimensional subsurface measurements in a minimally invasive manner. Crosshole
methods have the potential to provide high-resolution information about geophysicalattributes in the intra-wellbore area. A goal for environmental characterization should be
to use these high-resolution, multidimensional images of geophysical attributes to infer
key hydrologic properties of the subsurface.
However, several obstacles remain to be overcome before crosshole tomographic data
can be used routinely and reliably for estimating hydrologic properties. Some of theissues are briefly described below, under the topics of petrophysical relationships,
estimation methodologies, and inversion approaches. Roadmap activities to address thesethree topics are listed immediately afterward. The important issue of scaling, as it applies
to interpretation of geophysical data and integration with other GHCB data, is discussed
more fully in Section 3.2, which covers roadmap activities relevant to scaling.
2.2.3.1

Petrophysical Relationships

The relationships between measurable geophysical attributes of a body of rock and its
hydrologic parameters such as porosity and water content are called petrophysicalrelationships. Much work has been dedicated to investigating such relationships forconsolidated rocks at higher pressures (greater than 15 Mpa, conditions common for
petroleum reservoirs). However, research on petrophysical relationships for near-surface
sites is still in its infancy. Currently, most investigations obtain, at best, a site-specificrelationship between co-located geophysical attributes and hydrologic parameters. Few
attempts have been made to move beyond site-specific characterization of these
relationships to fully understand the interaction between field-scale geophysicalresponses and the physical properties of the medium.
Similarly, there has been little research on how to include data on multiple
geophysical attributes in the petrophysical relationship, in order to reduce uncertainties.
Nor has there been much research on resolving the non-uniqueness conditions that are
sometimes inherent in petrophysical relationships.
2.2.3.2

Estimation Methodologies

Routine procedures must be developed to integrate geophysical tomographic data
rigorously with existing direct measurements from wellbores and with other data

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2.0 Physical, Chemical, and Biological Properties(geological information, surface geophysical data, chemical data, and biological data).
These integration methods also must provide better estimates of uncertainty arising frommeasurement error, inversion error, and use of an estimated petrophysical relationship.
We must understand how to use multiple, co-located data sets to reduce the ambiguity
and uncertainty associated with parameter estimates. Stochastic methodologies havebeen developed to handle some of these issues, but the methodologies would benefit fromrefinement and further testing and extension with scale issues in mind. (These and otherissues in estimating and reducing uncertainty are discussed further in Section 3.3, alongwith roadmap activities specifically addressing uncertainty.)
2.2.3.3

Inversion Approaches

Inversion approaches, such as those involving crosshole tomography, must be further
developed and tested. Consensus must be reached on appropriate data correction
procedures prior to inversion. More advanced approaches such as constrained inversion,
stochastic inversion, and joint geophysical-geophysical or geophysical-hydrologic
inversions need further investigation, including testing and validation. We should
investigate how to weigh the information content of the different geophysical data prior
to joint inversion, how to invert data having different resolutions, and how to provide
uncertainty estimates that correspond correctly to the inverted tomographic attributes.
To translate geophysical attributes into hydrologic parameters, issues of scale must be
considered. The large spatial variability of hydraulic properties in natural geologicalsystems over a wide range of scales increases the difficulty of estimating hydraulicparameters and their spatial correlations from geophysical attributes and imagery.
Further, the obtained measurement value is a function of the subsurface volumeinterrogated by the instrument (sometimes called the instrument support scale), as well as
the network scale (acquisition parameters/instrument spacing), compounding the
problem. Both the instrument and network scales vary among and even within
geophysical methods. Thus, it is crucial to understand how these measurement-related
scales impact obtained values and how to incorporate different types of measurementswith each other. A general understanding is needed for how to scale measurements
collected in the laboratory for use in the field, how to use petrophysical relationships
developed in the laboratory with field data, and how to integrate different geophysicaldata that sample different volumes.
Activity PH10. Characterize the petrophysical relationships for translating
geophysical attributes in near-surface strata into estimates of hydrologic
parameters relevant to vadose zone contamination (e.g., porosity and watercontent).
•

Near-Term Status Point. Generalized petrophysical relationships between
geophysical attributes and hydrologic parameters have been developed fornear-surface environments.

•

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relationships and can aid in resolving issues of non-uniqueness inrelationships between geophysical and hydrologic parameters.
•

Mid-Term Status Point. The mechanisms of geophysical energy
propagation at the field tomographic scale within unconsolidated or loosely
consolidated, low pressure, granular porous material are understood.

•

Mid-Term Status Point. Joint and constrained inversions that honor all data
can be performed. How additional data improve the estimate and decrease theestimation error is understood. Data with different measurement scales can beincorporated in the inversion process correctly.

•

Task with Mid-Term Endpoint. Develop a quick and reliable way to assess
the extent of a vadose zone contamination problem relative to the scale of thehydrologic heterogeneity so that the most appropriate techniques andacquisition parameters can be selected for characterizing the key parametersthat control flow and transport at that site.

•Long-Term Status Point. Methods to scale between laboratory-scale andfield-scale measurements are known and in use. A variety of differently
scaled data can be reliably incorporated into geophysical inversions to provide
an integrated and hierarchical interpretation of hydrologic properties.

Activity PH11. Improve and apply geophysical methods for characterizing nearsurface environments typical of sites with vadose zone contamination.
•

Task with Near-Term Endpoint. Develop automatic data picking andquality control approaches for crosshole tomographic methods.

•

Task with Near-Term Endpoint. Investigate the utility of constrained andjoint inversion for improved estimation of hydrologic parameters. Develop
stochastic inversion procedures that yield distributions of possible geophysicalattributes at each location.

•

Near-Term Status Point. Stochastic estimation techniques that provide anestimate of the property of interest, as well as information about its
uncertainty, have been tested and applied to contaminated vadose zone sites.

•

Near-Term Status Point. Incorporate measurement support scale, and othermeans of recognizing the importance of scale, when applying geophysicalmethods to estimate hydrologic properties and correlation lengths.

•

Mid-Term Status Point. Hydrologic properties (e.g. water content,
permeability and porosity) and their associated uncertainties and spatial
correlation functions are being estimated from different types of geophysicaldata such as crosshole tomographic imagery. These estimates are conditioned
to direct measurements, with attention to scale, using hierarchical spatial scaleestimation procedures with multi-scaled data.

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2.0 Physical, Chemical, and Biological Properties

Long-Term Status Point (applies to Activities PH10 and PH11). Practicalguidelines for different environments allow quick field tests to determine thecharacterization regime into which the vadose zone at a contaminated site
falls. The governing petrophysical relationship for that regime is used tointerpret the geophysical data to obtain first-pass estimates of key flow andtransport parameters.
Long-Term Status Point (applies to Activities PH10 and PH11). Tomographic
methods can supply real-time, multidimensional (spatial and temporal),automatic interpretations of hydrologic properties or changes in properties due
to bacterial modification, environmental remediation, infiltration, and otherdynamic processes. The fully automated inversion process may also
incorporate varying scales, but must provide real-time estimates of hydrologic
properties at high resolution.
2.2.4

Highlights of Roadmap Results for Physical Description of
Flow and Transport

Table 1 highlights some of the major results that can be anticipated from these 11
research activities addressing physical processes and properties. The time horizons
indicated in the table are contingent on sufficient support and programmatic direction toaccomplish the detailed tasks and achieve the status points listed under the activities.
Table 1 Highlights of Results for Physical Description of Flow & Transport Research Activities
Near Term

Mid Term

Long Term

Computer models used by federal agencies and others incorporate the best state-ofthe-art conceptual models and implementations (software modules).
We can detect the presence of fluid in fractures in some cases.
We can distinguish, in most cases, the subset of fractures that are conduits for fluid
flow and contaminant transport.
We can map and predict water distribution and flow through structured soils or
fractured rock at multiple spatial scales.
Monitoring data on fluid flow and contaminant transport can be interpreted andrepresented visually at site-wide scales in real-time.

2.3

Chemical Properties and Processes

The roadmap pathways for chemical properties and processes divide into two broad
categories: 1) understanding reactive flow and transport, and 2) measuring and modelingchemical properties and processes in the vadose zone environment.
2.3.1

Understanding and Modeling Basic Chemical Properties andProcesses

Numerical continuum models of reactive flow and transport in heterogeneous,
variably saturated, nonisothermal porous media have advanced considerably in the past
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several years. It is now practical to carry out simulations in one or two spatial
dimensions, on small to medium sized grids (2,500-10,000 nodes), for coupled, transient,flow and transport that is both multiphase (aqueous, gaseous, CO2, and non-aqueous
phase liquid (NAPL)) and multicomponent (on the order of 10-20 degrees of freedom).
Processes that can now be incorporated in these simulations include:•

Homogeneous reactions involving aqueous complexing, ion pairing, and redox
reactions,•

Heterogeneous reactions consisting of mineral precipitation and dissolution, sorption,
and aqueous-gaseous reactions, and•Transport and reaction with colloids.

Reaction rates may be described either through kinetic rate laws or local equilibrium, as
appropriate. In addition, flow and transport may be sequentially coupled, thus accounting
for changes in porosity and permeability resulting from chemical reactions.
Few, if any, computer codes currently account for all of these different features.
Although limited work has begun on developing next-generation codes for threedimensional simulations with large numbers of unknowns, to be run on massively parallel
computing architectures, development of optimally efficient and powerful parallel
algorithms is still in its infancy.
Continuum models that incorporate various levels of geochemical complexity do
exist. However, key research challenges are to parameterize these codes, develop moreaccurate rate laws, and understand the relationships between chemical and physicalchanges occurring in porous media. Roadmap activities for these research areas are
discussed below.
2.3.1.1

Parameterization of Codes

Computer codes for geochemical reactive transport require representations of key
chemical parameters, such as the characteristics of contaminated solutions that determine
the rates at which they react with their local geochemical environment. Algorithms anddatabases exist for modeling aqueous solution chemistry at 25°C and ionic strengths lessthan approximately 1 molar, using extended Debye-Hückel coefficients to correct thechemical activities. For higher temperatures and high ionic strengths, however, thethermodynamic data are sparse. Although measuring these properties requires stringent
laboratory conditions, existing technologies are adequate to obtain the needed data.
Activity CH1. Extend solution chemistry models to higher temperatures and ionicstrengths (e.g., Pitzer equations) relevant to vadose zone contamination
problems.
•

Near-Term Status Point. Solution chemistry models have been extended totemperatures and ionic strengths needed for most vadose zone contamination
problems, including DOE contamination sites.

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2.3.1.2

Accurate Rate Laws

Rate laws used in existing computer codes are commonly based on transition state
theory or simple reaction kinetics. Rate constants for kinetic descriptions of mineralreactions have been obtained over a limited temperature range and for limited
compositional variables, primarily pH. Often, however, rate laws measured in thelaboratory are not suitable for direct use in a reactive transport model because they do notcover a suitable range of conditions. For example, the oxidation state of the system maychange from oxidizing to reducing along the flow path. Rate laws are needed which
encompass the variation in oxidation state and other conditions over the entire flow path.
Mineral rate laws apply to crystalline phases and not to glasses or phases with mixed
structural states, such as mixed-layer clays. Rate constants for relevant homogeneous
redox reactions are largely unknown. Subsurface low-temperature systems are often in
redox disequilibrium. The reaction kinetics for these systems is also strongly coupled tothe available reactive surface areas of potential reactant phases. Finally, nucleation
mechanisms are often poorly understood, thus preventing adequate description of
conditions leading to supersaturation, which results in inappropriate kinetic descriptionsof the processes involved.
While ion exchange and surface complexation models are commonly used in reactive
transport models, the data needed to support these models are generally not available.
Furthermore, the available data are limited primarily to 25°C for conditions of local
chemical equilibrium. These conditions are not typical of contaminated near-surface
vadose zone environments. Surface complexation models also often fail to conservecharge when combined with transport processes.
Activity CH2. Improve the understanding of kinetic rate mechanisms and effective
surface areas, in order to develop improved rate laws.
•

Near-Term Status Point. Reaction kinetics and rate laws have beenformulated that are appropriate for use in numerical continuum models ofreactive flow and transport for many vadose zone contamination problems,
including DOE sites.

•

Long-Term Status Point. Databases of appropriate reaction rate constants
applicable to refined reaction rate laws have been developed throughexperimental studies.

2.3.1.3

Linkages between Chemical and Physical Changes in Porous Media

Chemical reactions sometimes alter the physical properties of the medium. Reactionsof primary importance are mineral precipitation and dissolution and biomass formationand destruction. Such changes are difficult to quantify and usually require phenomenological formulations based on experiments. Typical coupled processes include changes inporosity and permeability, surface armoring, and changes in cation exchange capacity
and surface site density.

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Activity CH3. Investigate cation exchange capacity and surface site
density/complexation reactions on mineral surfaces and colloids for systems
typical of vadose zone environments and contamination problems. Resolve
the importance of lack of charge conservation in surface complexation models
when combined with transport, possibly by including streaming potentials in
the formulation.
•

Task with Near-Term Endpoint. Determine if significant differences exist
for measurement of cation exchange capacity and surface site density between
in situ field measurements of undisturbed samples and laboratory batchmeasurements involving disturbed media. Validate conditions under whichbatch Kd measurements can be used to estimate retardation in variably
saturated flowing systems.

•

Mid-Term Status Point. The kinetics (including reversibility) of ion
exchange and surface complexation reactions on mineral surfaces and colloids
has been determined for most solution-solid systems relevant to vadose zone
contamination problems.

Activity CH4. Investigate the effects of dissolution and precipitation on porosity,
pore structure, and permeability. Study nucleation controls that may bias
dissolution and/or precipitation to particular pore environments.
•

Task with Mid-Term Endpoint. Develop a functional description for
porosity/permeability evolution reflecting chemical effects.

•

Task with Mid-Term Endpoint. Develop rate laws for glass dissolution andsolid solutions that cover more extended conditions typical of natural andcontaminant-affected flow fields. Improve models of nucleation processes.

Long-Term Status Point (applies to Activities CH1 through CH4). Kinetics and rate
laws have been formulated for ion exchange and surface complexation
processes coupled with mineral precipitation and dissolution. This knowledge
has been validated in field experiments and incorporated in reactive flow andtransport models for vadose zone systems.
Porous media in the unsaturated zone typically contain gaseous, solid, and liquid
phases in which phase boundaries can significantly alter the geochemistry of bothindigenous minerals and contaminant species, as well as liquid phase properties. The
effects can be especially important in very dry situations involving low water contents
and thin liquid films covering the solid phase.
Activity CH5. Investigate phase boundary conditions occurring in vadose zone
environments that may significantly influence liquid flow and contaminanttransport.
•

Task with Mid-Term Endpoint. Develop accurate models for mineralreactions in contact with a thin liquid film that may have different properties

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compared to bulk fluid (e.g., for extreme evaporation conditions that may
favor formation of evaporite mineral phases).
•

2.3.2

Task with Mid-Term Endpoint. Develop accurate models for mineralreactions in unsaturated systems having variable gas phase chemistries (e.g.,
low and high CO2 or O2).

Measuring Chemical Properties and Processes

The role of chemical characterization and monitoring in the vadose zone is todescribe chemical fate and transport in space and time. From this description, theconcentration and extent of contaminants can be determined, and appropriate conceptualmodels of transport can be developed to aid in prediction and planning.
Assessing accurately the spatial distribution and concentration of contaminants is an
essential first step in addressing most problems of environmental contamination faced byproblem owners, such as DOE and DOD, or regulators such as EPA. At present, theconcentration and extent of contamination is usually determined using invasive sample
collection methods (typically boreholes) and laboratory analysis of samples. In situ
probes can monitor some contaminants with near-real-time analysis and transmit datausing datalogger technology. Some contaminants (e.g., radioactive constituents) can beobserved using borehole geophysical methods. In most cases, however, concentrations
are measured only at a discrete time interval (e.g., quarterly) and only for a limited
number of spatial points.
To improve our current methods, five tasks must be accomplished. The first task is toselect technologies that can identify the characteristics of individual contaminant species.
Candidate technologies include spectral induced polarization; nuclear magnetic
resonance; spectral electromagnetic techniques including radar, neutron logging
technology; and chemical sniffing methods. Second, researchers must establish therelationship of the measurements to the contaminant species. Through laboratory
analysis, chemical species can be isolated by their geophysical or geochemical responses.
A third task is to determine the sensitivity limits of the measurement to the contaminant
species and their concentrations. Fourth, prototype tools or combinations of tools
suitable for a restricted environment need to be deployed. Finally, consideration must be
paid to newly invented tools and approaches and other innovations that may be used to
improve current methods.
Activity CH6. Improve and develop methods of identifying chemical contaminantsin the vadose zone.
•

Near-Term Status Point. The presence of individual chemical contaminants
in soils or other vadose zone strata can be determined from surface orborehole measurements, although field results may require verification withlaboratory analyses.

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2.3.3

•

Mid-Term Status Point. Concentrations of the most abundant species(except those at very small concentrations) can be determined within an orderof magnitude.

•

Long-Term Status Point. Contaminated volumes can be isolated, and theconcentration of abundant chemical species can be determined to within 10 or
20 percent.

•Long-Term Status Point. The volumes and spatial distributions of resident
contaminants at or near source discharge points can be quantified for metals,
radionuclides, and organics.
Highlights of Roadmap Results for Chemical Properties andProcesses

Table 2 highlights some of the major results that can be anticipated from these nineresearch activities for chemical processes and properties. The time horizons indicated in
the table are contingent on sufficient support and programmatic direction to accomplish
the detailed tasks and achieve the status points listed under the activities.
Table 2 Highlights of Results for Chemical Properties & Processes Research Activities
Near Term

Mid Term

Long Term

Reaction kinetics and rate laws (in solution) have been formulated for priority vadosezone conditions.
Individual chemical contaminants in the vadose zone can be detected.
We understand the kinetics for important chemical reactions at solid and liquidinterfaces (e.g., ion exchange and colloids) in vadose zone conditions.
Flow and transport models map and predict important vadose zone chemicalinteractions, including those involving mixtures of solids, liquids, and air.

2.4

Biological Properties and Processes

Microorganisms are directly or indirectly responsible for numerous processes that
influence the mobility and persistence of contaminants in the vadose zone. They use
many organic pollutants as carbon sources or as electron donors or acceptors inbiochemical oxidation-reduction reactions. Many metals and radionuclides are
metabolically transformed into chemical species that may be either more or lesssusceptible to long distance migration than their pre-metabolite forms. In addition,
microorganisms can have a profound influence on their immediate environment byaltering porosity, surface characteristics, pH, or oxidation potentials. These
environmental changes in turn affect contaminant transport.
2.4.1

Understanding Biological Properties and Processes

In contrast to the saturated zone, for which a relatively large microbiologicalknowledge base exists, much less information is available on the distribution, rate, andcontrols of vadose zone microbial processes. The vadose environment poses a number ofchallenges to quantifying microbial processes. Concentrations and fluxes of carbon andRevision 0.0

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other nutrients are often very low, and their distributions are heterogeneous. Inputs ofnutrients, via rainfall or other means, to the vadose zone at many contaminated sites inarid climates are minimal and intermittent. Infiltration is often localized to fractures andregions of preferential flow. Thus, microorganisms may have to survive long periods ofdormancy, yet be prepared to take immediate advantage of transient and often brief
influxes of nutrients. As a consequence of these and other constraints, microbial activity
tends to be discontinuous and patchy in both time and space.
Transport and colonization of microorganisms is another important issue. Microbes
and contaminants are generally not co-located. A major challenge of engineered
bioremediation is the delivery of microorganisms to sites of contamination.
Many of the mechanisms for microbial interaction with a few specific contaminants
are known. But much remains to be learned about the parameters that control the rate oftransformations of radionuclides and mixtures of contaminants, as well as microbial
processes in general under extreme conditions. In addition, it is not well understood how
the unique hydrologic features of the vadose zone affect metabolism, growth, andmicrobial transport processes or the distribution of these processes. An understanding ofthese interactions and processes is required for reliable predictions of contaminanttransport (enhanced transport and natural attenuation) and the potential for successful
engineered bioremediation.
There are three major research goals to be accomplished:
1.

Understand the mechanisms of microbial-contaminant interactions, including
biodegradation and transformation, mobilization, complexation, and precipitation,for inorganics and contaminant mixtures in contact with vadose zone materials
and engineered biotreatment zones.

2.

Conduct field and laboratory experiments and characterization to develop
mathematical descriptions of key microbial processes and their linkage tospatially variable hydrogeological and geochemical processes.

3.

Apply emerging measurement and sampling technologies for understanding insitu rates and scaling of microbial populations/activities in heterogeneous systems
to scales relevant for field-scale modeling.

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The following four activities address these research goals.
Activity B1. Understanding the mechanisms of microbial-contaminant interactions.
•Task with Near-Term Endpoint. Quantify rates of microbial processes
affecting inorganics, chelate-inorganic complexes, inorganic complexes, andorganic contaminants; identify the factors controlling those rates.

•

Task with Near-Term Endpoint. Understand and predict how contaminantbioavailability affects, and is affected by, microbial processes.

•

Task with Near-Term Endpoint. Characterize microbial-mediated corrosion
and biodeterioration of materials used to contain contaminants at DOE sites
and other sites with contained buried wastes.

•

Task with Mid-Term Endpoint. Improve the conceptual and mathematicalcharacterization of interactions between microorganisms and contaminants(e.g., biodegradation, immobilization, transformation), microbial andphysical/chemical processes (coupled processes), and incorporate these
relationships into reactive transport models.

•

Task with Mid-Term Endpoint. Elucidate pore-scale interactions between
microorganisms and contaminants, under undisturbed conditions, including
studies: (1) at the microscopic level; (2) at interfaces (solid/liquid, liquid/gas,liquid/liquid, solid/gas, and along textural discontinuities); and (3) in biofilms.

•

Task with Mid-Term Endpoint. Determine the importance to contaminanttransport and preferential flow of microbial attachment/detachment, biofilms,
and microbial associations with colloids.

Activity B2. Understand how mixtures of contaminants affect microbial activity withrespect to flow and transport of specific contaminants.
•

Mid-Term Status Point. Conditions under which toxicity of radionuclides,
metals, or organics prevent removal of readily degradable organic
contaminants have been identified.

•

Mid-Term Status Point. The rates of biodegradation of particular
contaminants can be predicted as a function of the type and concentration ofother contaminants present.

Activity B3. Understanding microbial community composition and activity.
•

Near-Term Status Point. Rapid statistical and classification methods forhandling large data sets generated from the characterization of microbialcommunities have been developed and applied.

•

Mid-Term Status Point. Microbial diversity in representative vadose zone
systems has been characterized (measured), and the factors governing
diversity have been determined. Relationships between diversity andcommunity response to contaminants have been determined.

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Task with Mid-Term Endpoint. Understand the potential roles ofsiderophore, surfactant, and chelate production by microbial communities,
including the plant root–microbial community interface, on contaminanttransformations in engineered biotreatment zones and in contaminated sites
without engineered biotreatment.

•

Long-Term Status Point. The spatial distribution of microbial biomass,
activity, and community composition in the vadose zone can be predicted withrespect to contaminant distribution. Effects on the microbial distribution fromwater inputs, contaminant fluxes, and duration of exposure to contaminants
can also be predicted.

Activity B4. Characterization methods to understand in situ rates and community
activities at scales relevant for field-scale modeling.

2.4.2

•

Task with Mid-Term Endpoint. Characterize microbial transport indifferent natural porous media and through/from engineered biotreatment
zones relevant for vadose zone contamination sites (DOE and others). In
particular, characterize transport through unsaturated fine and coarse sands
and fractured rock, as a function of water saturation and solution chemistry.

•Long-Term Status Point. In situ rates of microbial biotransformation ofcontaminants at contaminated sites can be predicted as a function of site andenvironmental conditions.

•Long-Term Status Point. Information about the composition of vadose zone
microbial communities has been incorporated into pollutant fate and transportmodels.

•Long-Term Status Point. Transport of native and introduced
microorganisms at contaminated vadose zone sites can be predicted.
Measuring Biological Properties and Processes

Biological processes are important for methods of vadose zone characterization andmonitoring in two ways. First, microorganisms are involved in many processes affecting
contaminant transport and transformation, and their effects must be quantitatively
understood. Second, biological processes, biomolecules, and biomaterials can be used ascomponents in instruments and sensors for characterizing and monitoring the vadosezone.
Non-invasive techniques have been used only in an exploratory fashion to observe the
distribution and activity of microbes in the subsurface. Nearly all state-of-the-art
microbiological characterization methods currently require invasive sample collection.
Most also require subsequent laboratory analysis (rather than incorporating downhole
data collection). These requirements result in several problems: high cost, inability tomeasure rates in situ, general lack of joint measurements, and inadequate scale ofmeasurements.

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In addition, as noted in the previous section, microbial processes in the vadose zone
exhibit spatial heterogeneity and nonlinear temporal dynamics. Small and local
variations in physical and chemical properties can result in large differences in subsurface
microbial populations and activities. Because invasive sampling and laboratory analysis
are required to assess these activities, resolution of spatially heterogeneous andtemporally varying microbial distributions is a particularly difficult problem.
Three major types of microbial data are needed for site assessment and site
monitoring: bioavailability, in situ rates, and community composition and activity.
Forged by the intersection of biology, microfluidics, microelectronics, and micro-optics,
biotechnological advances pertinent to all three types of data are occurring rapidly in theprivate sector. However, investments in research are necessary to adapt and apply theseadvances to vadose zone science and stewardship.
Bioavailability. It is important to know what concentration or mass of a contaminant isimmediately available for microbial transformation or is capable of toxic effects onorganisms. Ways are also needed to measure the fraction that may eventually become
available. Among the potential means to acquire these data are improved in situ sensors
and development of other approaches.
Activity B5. Developing and improving measurement techniques for bioavailability.
•

Near-Term Status Point. Improved bioavailability sensors and/or assays
have been developed.

•

Mid-Term Status Point. In situ bioavailability sensors have been developed
and are in application.

In situ rates. We need approaches for measuring in situ rates at scales of intermediate(0.1 to 10 m3) and miniature (millimeters to centimeters) interrogation volumes. For field
applications, approaches using gases and/or solutes are needed, similar to the in situ
respiration test. (This test measures the rate of depletion of injected oxygen to estimate
degradation rates for petroleum hydrocarbons.) Challenges to using these approaches
successfully include: (1) development of instrument systems that minimize changes inmoisture status and reduce the creation of near-wellbore artifacts during the assay, and(2) sufficient analytical sensitivity for in situ processes, which are often very slow.
Activity B6. Developing and applying sensors and sensor systems for in situ ratemeasurements.
•

Near-Term Status Point. Sensors and systems for in situ rate measurements
have been developed.

•

Near-Term Status Point. Chemically reactive contact foils and films for insitu rates and/or potential activity have been developed.

Community composition and activity. Rapid advances are occurring in high-resolution
signature lipid biomarkers, DNA chips, and other nucleic acid methods for characterizing
microbial community structure, diversity, and activity. These measurements are

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important for improving our understanding of vadose zone microbiological processes andlinking communities to functions. However, the per-sample cost is high.
Activity B7. Developing and applying systems for measuring microbial community
composition and activity.
•

Near-Term Status Point. Sample-to-answer analytical systems forcommunity composition and activity have been developed.

•

Near-Term Status Point. Spectroscopy-based and synchrotron-based
inferences of microbial activity have been developed.

•

Task with Near-Term Endpoint. Perform laboratory studies and develop
models of the bio-electric level as a function of different soil types andmicrobes (aerobic versus anaerobic, a variety of metal-reducing and organicsreducing microbes).

•

Mid-Term Status Point. Inexpensive sample-to-answer analytical systems
for community composition and activity are being applied.

•

Task with Mid-Term Endpoint. Develop instrumentation to detect lower
levels of activity and validate this instrumentation in intermediate-scale andfield-scale tests.

Three important long-term status points apply to all three of these roadmap activities
for measurement of subsurface microbial communities and activities.
Long-Term Status Point (applies to Activities B5–B7). Economical analysis ofspatial distribution and temporal dynamics has been developed and applied.
Long-Term Status Point (applies to Activities B5-B7). Nondestructive joint
measurement of biological, geochemical, physical, and hydrologic properties
or processes has been extended to intact cores and possibly to the subsurface.
Long-Term Status Point (applies to Activities B5-B7). Proxy measurements for
microbiological properties and processes have been developed.
2.4.3

Highlights of Roadmap Results for Biological Properties andProcesses

Table 3 highlights some of the major results that can be anticipated from these sevenresearch activities for biological processes and properties. The time horizons indicated in
the table are contingent on sufficient support and programmatic direction to accomplish
the detailed tasks and achieve the status points listed under the activities.

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Table 3 Highlights of Results for Biological Properties & Processes Research Activities
Near Term

M id TermLong Term

We understand and can predict how microbial processes affect or are a ffected bybioavailability of important contaminants.
We can measure biochemical rates, in situ bioavailability, and the composition andactivity of microbiological communities.
Reactive transport models can predict how microorganisms will interact withcontaminants.
Inexpensive systems are available to measure community composition and activity.
We can accurately predict site-specific biodegradation rates for important
contaminants.
We can take biological measurements along with others without destroying thesamples.

2.5

Colloidal Formation and Transport

Many contaminants such as radionuclides and metals are often strongly sorbed by soil
and sediments, thus limiting their transport in the subsurface. In some instances,
however, strongly sorbing contaminants have been found at locations far beyond what
would have been anticipated from current knowledge and solute transport models. It ishypothesized that these contaminants attach to small particles, called colloids, which may
move relatively unhindered through the subsurface. Colloids with sizes between 1 nm
and 1 )m can, under certain conditions, move large distances through a porous medium.
Considerable advances have been made in understanding colloidal processes andtransport in well-defined systems such as water-saturated sand filters. However, key
processes including colloid formation, mobilization, and deposition in different types ofnatural porous media are still not well understood. Although colloidal particles arenaturally present in most soils, sediments, and rocks, they do not necessarily form stablesuspensions and are therefore not very mobile. However, when certain systemparameters are changed, such as the water flow rate or the solution chemistry, colloidal
particles may become mobile and act as carriers for contaminants.
Microorganisms are a special class of colloidal particles. While their own fate andtransport is strongly affected by their surface properties, microorganisms, like othercolloids, can also alter the subsurface transport of organic and inorganic contaminants.
For instance, microbial precipitation of soluble radionuclides and metals within cells or atcell surfaces can substantially alter the transport properties of these contaminants.
Knowledge of colloidal processes in the subsurface improves the accuracy andreliability of predictions of short- and long-term contaminant fate and transport. Also,
natural augmentation or artificial introduction of colloidal particles, such as
microorganisms, into the subsurface is a potentially promising new remediation
technology for many types of contaminants. Long-term stewardship of waste sites andthe development of appropriate remediation strategies require detailed mechanistic
understanding of colloidal processes in the subsurface.

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The specific mechanisms of colloid interactions with subsurface materials are notwell understood. Nor is the transport of colloids in natural soils, sediments, and rocks.
To describe quantitatively, and predict, the role and significance of colloids incontaminant transport, research must focus on three goals: (1) understanding mechanismsof colloid-contaminant and colloid-sediment interactions, including colloid formation,
mobilization, and deposition; (2) improving sampling and analysis techniques for colloids
and colloidal transport; and (3) modeling colloid transport and colloid-facilitatedtransport in unsaturated soils, sediments, and fractured rocks. The following threeroadmap activities are directed at these goals. Table 4 highlights some major results thatcan be anticipated from these activities, given sufficient support and programmatic
direction to accomplish the tasks listed under the activities.
Activity COL1. Improve sampling and analysis for colloids and colloidal transport.
•

Task with Near-Term Endpoint. Develop a scientifically based protocol forfield based sampling and analysis for colloids and colloidally transported
contaminants.

•

Task with Near-Term Endpoint. Develop new sampling techniques for insitu measurements of colloidal particles in pore water.

•

Near-Term Status Point. Mobile colloids are considered in sampling andanalyses protocols for field studies and monitoring systems.

Activity COL2. Studies of colloidal transport.
•

Task with Mid-Term Endpoint. Quantify effect of preferential flow on
colloid transport.

•

Task with Mid-Term Endpoint. Understand relevance of colloid-facilitatedtransport to contaminant movement under transient flow conditions, including
wetting, drying, and infiltration processes.

•

Task with Mid-Term Endpoint. Quantify the potential for in situ colloid
formation and mobilization under conditions relevant for major vadose zone
contamination sites, particularly in the presence of extreme chemical
conditions that can lead to dissolution and precipitation of soil minerals.

•

Task with Mid-Term Endpoint. Evaluate the effects on production andbehavior of microbial colloids of (1) changing contaminant flux, (2) nutrient
injection during engineered bioremediation, and (3) cell to cellcommunication (quorum sensing) in biofilms and other cell assemblages.

•

Task with Mid-Term Endpoint. Characterize colloid-contaminantinteractions as a function of solution chemistry and water saturation, at both
microscopic and macroscopic levels.

•

Task with Long-Term Endpoint. Characterize colloid transport in different
natural porous media relevant for sites with contaminated vadose zones. In
particular, characterize and quantify colloidal transport through unsaturated
fine and coarse sands and fractured rock, as a function of water saturation andRevision 0.0

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solution chemistry. Quantify colloid interactions with solid-liquid and liquidgas interfaces.
Activity COL3. Models of colloidal transport.
•

Task with Long-Term Endpoint. Model colloid transport and colloidfacilitated transport in unsaturated soils, sediments, and fractured rocks.

•

Long-Term Status Point. Improved conceptual and mathematicalcharacterizations of colloid-contaminant-soil interactions and colloidfacilitated transport have been incorporated into reactive transport models
used by DOE and other agencies for assessing vadose zone contamination.
Table 4 Highlights of Results for Colloidal Formation & Transport Research Activities
Near Term

M id TermLong Term

We know how to detect mobile colloids and how to sample and analyze them.
Important colloid-contaminant interactions understood at micro and macro levels.
Flow and transport models can map and predict important colloidal interactions andtransport.

2.6

Multiphase Flow and Transport

Multiphase flow and transport of organic and inorganic contaminants in the vadosezone poses serious scientific and technical challenges. The vadose zone always contains
multiple fluid phases through which contaminants may move, as well as associatedinterfaces for partitioning between phases. For example when air, water, NAPLs, and an
immobile solid phase are present, three mobile phases may occur, with as many as six
interfaces for contaminant interphase mass transfer. The remediation of contaminatedsites is ultimately controlled by the rates of these interphase mass transfers. Furthermore,migration and transport processes in the vadose zone control the rate of contaminantloading in the saturated zone.
Over the past several decades, research has focused on quantifying flow and transport
processes using idealized fluids and porous media. This research has greatly improved
overall knowledge and the ability to predict multiphase flow and transport. However,additional research is necessary to quantify the effects of subsurface physical andbiogeochemical heterogeneity on contaminant fate and persistence. Procedures to scalelaboratory-derived constitutive properties and parameters up to field scale are especially
important. These include mass transfer and biological parameters that are typicallymeasured at the soil column and microcosm scales. Unstable and preferential flow (e.g.,fingering) of aqueous and NAPL phases is another important issue because of its
potential to enhance contaminant mobility in the subsurface.
Additional difficulties arise when sites contain complex mixtures of inorganic andorganic compounds, such as heavy metals or radionuclides mixed with organic solventsand complexing agents. Interactions among aqueous phase contaminants are known to
influence their geochemical behavior and transport. Very little research has explored andRevision 0.0

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quantified the fate and persistence in the vadose zone of contaminant mixtures that may
involve complex interactions among phases, interfaces, and chemical components. These
interactions will likely influence multiphase flow and transport processes, as well as
bioavailability of contaminants. Related questions concern the effects of chelating agentsand NAPL phases on heavy metal and radionuclide transport, differences in the transportof complex NAPL mixtures versus pure NAPLs, the effect of aqueous chemistry on
NAPL migration and transport, and the potential adverse and synergistic interactions
among contaminants in mixtures during remediation operations. Understanding thenature of the contaminant association increases the probability of developing efficient
remediation strategies that treat multiple contaminants simultaneously.
As discussed in more detail in Sections 3.4 and 4.2, a combination of well-designed
laboratory, numerical, and field-scale studies is required to test specific hypotheses
related to multiphase fluids. Multidisciplinary teams are needed to address thesecomplex issues effectively. Collaboration among disciplines would improve descriptionsof multiphase flow and transport processes in complex vadose zone environments, thus
reducing uncertainty and ultimately providing specific tools for the design andimplementation of cost-effective remediation and containment operations.
The following three roadmap activities incorporate research needed to understand,measure, and model multiphase transport. Table 5 highlights major results that can be
anticipated from these activities, given sufficient support and programmatic direction toaccomplish the tasks listed under the activities.
Activity MP1. Extend knowledge and predictability of flow and transport processes
to multiphase systems.
•

Task with Near-Term Endpoint. Quantify effects of subsurface physicaland biogeochemical heterogeneity on multiphase flow and transport
processes.

•

Near-Term Status Point. Upscaling procedures to apply laboratory-derived
multiphase constitutive properties and parameters to the field scale have beendeveloped.

•

Near-Term Status Point. Process-based models can describe unstable andpreferential flow of aqueous and NAPL phases.

•

Task with Mid-Term Endpoint. Conduct multiphase flow and NAPL
transport experiments for representative soils and contaminants, to elucidate
real-world problems and data limitations.

Activity MP2. Studies of key contaminant mixtures (for DOE and othercontaminated vadose zone sites) as multiphase systems.
•

Task with Mid-Term Endpoint. Measure flow and transport properties ofkey contaminant mixtures. Refine theory and numerical models to describe
their flow and transport in relevant subsurface environments.

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Task with Mid-Term Endpoint. Design, implement and analyze controlled
tests of complex contaminant mixtures in highly heterogeneous systems.

Activity MP3. Incorporation of understanding and models for multiphase flow andtransport into site assessments and remediation strategies.
•

Long-Term Status Point. Remediation strategies routinely take into accountmultiphase flow and transport of site-specific contaminant mixtures.

•

Long-Term Status Point. Numerical models are being used to assess
uncertainty in flow and transport of complex contaminant mixtures at priority
sites (including DOE sites) and to support decisions with regard to
remediation and containment strategies.
Table 5 Highlights of Results for Multiphase Flow & Transport Research Activities
Near Term

M id TermLong Term

We can model processes with unstable or preferential flow of aqueous and nonaqueous phases.
We can detect and interpret multiphase flow and transport of complex contaminant
mixtures at contaminated sites.
Site assessment models incorporate multiphase flow and transport.

2.7

Unstable Processes

Field observations of fluid flow and chemical transport in both porous and fractured
unsaturated media often show unstable, spatially and temporally random fluctuations in
the moisture content, pressure, flow rate, temperature, and concentration of chemicals.
These fluctuations can result in rapid preferential flow and transport through the vadosezone to the groundwater table.
Despite numerous studies of preferential flow, many of the causes of flow instability
are still not completely known. What is known, however, is that flow in structured,
macroporous soils and fractured rocks is significantly influenced by abrupt changes inmedia physical properties (e.g., rough to smooth fractures, small to large pores) and by
the interplay between gravitational and capillary forces. These interactions generateliquid fragmentation (bridges, fingers, rivulets), intermittent flow, and extreme
sensitivity to small changes in boundary conditions and variations in media geometry.
None of these phenomena are typical of homogenous porous media.
Other examples of processes leading to unstable and chaotic-type flow are
discontinuities in the behavior of liquids in porous media. Examples include Haines
jumps, flow-induced nonlinear effects in thin liquid films, drainage by cavitation,
nucleation and mineral precipitation within pore spaces, density driven flow, dripping
water in fractures and caves, fracture–matrix interaction processes, and thermal effects.
Furthermore, combinations of several nonlinear physical processes involving both
deterministic-chaotic and random flow and transport processes may cause spatial andtemporal fluctuations of flow parameters. Continuum models have limited utility for
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representing inherently unstable and chaotic systems because of the need for different
governing equations to describe intermittent flows in different parts of the system and atdifferent times.
Chaotic dynamics is one of several new fields in modern science attempting tounderstand order and pattern in nature that cannot be explained with traditional linear
deterministic theories. Recognizing the presence of deterministic chaotic processes mayhelp to improve predictions of unstable flow and transport in the subsurface. In
particular, chaotic dynamics may improve our understanding of the physics of unstable
patterns of flow in variably saturated porous and fractured media, which can be describedwith either deterministic or stochastic models. For such a system, one can provide
precise short-term predictions using deterministic-chaotic models; only a range ofpossible long-term predictions can be made using stochastic models.
To understand more thoroughly the physics of processes leading to unstable flow,
special experimental and modeling investigations are needed. Models are needed todescribe coupled, highly nonlinear processes of flow and mass transport in variably
saturated media. It is also important to identify criteria (such as Bond and capillary
numbers) that can be used to determine the onset of chaos.
Two roadmap activities incorporate research needed to understand and model
unstable processes. Table 6 highlights major results that can be anticipated from these
activities, given sufficient support and programmatic direction to accomplish the tasks
listed under the activities. Other issues of nonlinear dynamics, involving coupled GHCB
processes, are discussed in Section 3.1.2.
Activity UP1. Studies of factors influencing unstable flow.
•

Task with Near-Term Endpoint. Identify directions for applying chaostheory in vadose zone hydrology by (1) reviewing the literature on physical,
chemical, and biological processes in which unstable flow occurs; and (2)comparing processes and conditions in other environments with thoseoccurring in the vadose zone.

•

Task with Near-Term Endpoint. Perform bench-scale and field-scale
investigations of factors leading to instability and chaotic-type flow andchemical transport in vadose zone conditions.

•

Near-Term Status Point. Criteria have been developed to identify the onset
of unstable and/or chaotic-type processes in vadose zone flow and transport.

•

Task with Mid-Term Endpoint. To identify conditions for which unstable
and/or chaotic-type processes are important, design and perform field-scale
infiltration tests with tracers at several sites with vadose zone contaminationin heterogeneous soils and fractured rocks.

•

Task with Mid-Term Endpoint. To determine the main diagnostic
parameters of chaotic-type flows, develop software that reconstructs thesystem phase-space from scalar data.

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Activity UP2. Modeling unstable and chaotic flow in the vadose zone.
•

Task with Near-Term Endpoint. Develop a series of models describing
unstable flow phenomena of deterministic chaos in unsaturated fractured
rocks.

•

Task with Mid-Term Endpoint. Develop a new generation of mathematicaland numerical models to describe unstable and chaotic-type flow processes insoils and fractured rocks.

•

Task with Long-Term Endpoint. Implement models of unstable and/or
chaotic-type flow into other deterministic and stochastic models used forpredicting flow and transport and designing remediation activities.
Table 6 Highlights of Results for Unstable Processes Research Activities
Near Term

We can identify the onset of chaotic and unstable processes.
We can determine whether and when chaotic conditions are important at a site.
Site assessment models incorporate models for chaotic and unstable flow.

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3.0 Combining the Basics

3.0

COMBINING THE BASICS TO UNDERSTAND, MEASURE,MONITOR AND MODEL VADOSE ZONE SYSTEMS

As noted in Section 2.1, development of site-wide quantitative GHCB models, which
can simulate the vadose zone of a contaminated site as an integrated system, is an
arduous and iterative process. It requires concerted collaborations between numericalsimulation of flow, transport, and transformational processes and the data collection
necessary to initialize, constrain, and validate the models for these processes. What isnecessary for more timely development is a toolkit for computations and interpolations
that can scale data collected at different instrument support scales, data collected overvarying time periods, and data collected at different spatial scales.
In this section, roadmap activities are discussed for important parts of that toolkit,
beyond understanding, measuring, and modeling basic processes and properties withincustomary disciplinary boundaries. Section 3.1 examines research needed acrossdisciplinary lines to characterize and model more realistically the coupled processes ofvadose zone systems. Section 3.2 addresses research needed to measure and represent
properties and processes at multiple spatial and temporal scales, a requirement forquantitative GHCB models. Section 3.3 describes work needed to estimate and reduce
uncertainties in GHCB models. Section 3.4 deals with other issues in integrating andvalidating these models as site-wide representations of vadose zone systems.
3.1

Coupling Basic Properties and Processes

The separation of topics in Section 2 followed traditional disciplinary lines. This
organization was arbitrary; it was used to simplify the presentation. In reality, variably
saturated liquid flow, contaminant transport, and biogeochemical processes occur not in
isolation but as tightly coupled systems often displaying nonlinear behavior. For
example, fluid flow is the primary mode of transport for many contaminants in thevadose zone. However, the chemical makeup (concentration and ionic composition) of
the fluid phase and various biogeochemical reactions can significantly affect fluid andsolid phase properties, which in turn affect fluid velocities and rates of contaminanttransport. Improved descriptions of the nonlinear transient interactions between thevarious processes and subsurface properties are needed, as are methods to deal with theoverwhelming complexity of these processes. Integration is also essential for identifying
which properties are the most relevant, and at what resolution, accuracy, and uncertainty
they must be estimated for effective input to predictive models.
3.1.1

Coupling Process and System Models across Traditional
Disciplinary Boundaries

Coupled models require an understanding of the complex interactions among mineral,
microbial, and colloidal surfaces and among fluid, solid, and gas phases. Some of theseprocesses include precipitation, surface complexation, sorption, attachment anddetachment, multi-domain diffusion, oxidation and reduction (both inorganic andRevision 0.0

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microbially mediated), porosity alteration, and heat flow occurring in a physically andchemically heterogeneous environment. Progress has been made in understanding
individual processes at a basic level, but research prioritization is needed because of themany components and interactions involved. Fundamental understanding at a molecularlevel may allow a few components to be studied intensively and the results expanded to awider class. In parallel, systematic study of coupled reaction systems in bulk phase
media can improve understanding of these mechanisms and their manifestation on
important coupled processes at the larger scales of observation.
It is important to realize that many problems in reactive transport modeling can bereasonably well addressed by understanding one dominant aspect of the problem.
Nonetheless, models need to be available that incorporate all of the relevant processes, inorder to select the appropriate interactions. Too often the model is selected first, andprocesses not included within that model are simply ignored.
Research needed for coupled models can be divided into database needs andconstitutive theory needs, as well as computational resources and numerical algorithms.
Roadmap activities for the first two are listed below. Computational resources, including
numerical algorithms, are discussed in Section 4.3.
Activity CP1. Improve existing or develop new databases for processes with coupled
GHCB properties•

Task with Near-Term Endpoint. Update and check reliability of available
databases used in coupled models. Make the reliable databases universallyavailable, with recommendations for usage.

Activity CP2. Develop cross-disciplinary modeling approaches and implement bettermodels (representations) for key vadose zone flow and transport processes
that cross traditional disciplinary boundaries.
•

Near-Term Status Point. Better estimation techniques are available tofacilitate routine incorporation into process models of different types of
GHCB data that have different sampling scales and different spatial
variability.

•

Near-Term Status Point. Coupled processes with the highest priority forunderstanding vadose zone fate and transport, and the gaps in understanding
them, have been identified.

•

Near-Term Status Point. Model studies have demonstrated capabilities andlimitations of existing coupled models. Procedures for their appropriate use
have been codified and are widely disseminated and accepted. Strongly
coupled nonlinear phenomena requiring development of new modelingapproaches have been identified.

•Task beginning in Near-Term, with Long-Term Endpoint. Use the resultsfrom the identification of priority coupled processes and knowledge gaps

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about them to guide research on sufficiently realistic representations of thehighest priority processes.
The following status point applies to both activities in this section. Additionalcrosscutting status points for these activities are listed at the end of Section 3.1.2.
Long-Term Status Point (applies to Activities CP1 and CP2). Realistic
representations of the priority coupled processes have been developed,
validated in field studies, and implemented in vadose zone fate and transportmodels.
3.1.2

Understanding and Modeling the GHCB Aspects of Strongly
Coupled Nonlinear Systems

For vadose zone modeling, strongly coupled systems are those where two or more
fundamental geological, hydrologic, chemical, or biological processes must be
understood and modeled together to accurately represent the flow and transport in thesubsurface. Modeling of these coupled, often nonlinear systems is one of the mostchallenging problems in reactive transport. Examples include bioremediation; in situ
redox manipulation for removal of chromium, uranium, and chlorinated hydrocarbons;coupled heat flow and transport for enhanced remediation or radioactively hot waste; andmodeling the leakage of highly basic, highly radioactive tank waste solutions at Hanfordor other DOE sites. Feedback between nonlinear processes can lead to instabilities.
Examples include coupled chemical reaction fronts that can become stable or unstable,
depending on the nature of the water chemistry and the mineralogy of the permeable
material.
Conventional modeling techniques cannot handle truly coupled nonlinear processes.
The current capability to model some of these processes is mostly limited to crude locally
lumped parameter models that hide much of the complexity. More advanced models areavailable to model specific processes, such as adsorption, precipitation, or microbial
transformation. Nonetheless, the basic scientific understanding of the processes, andespecially of their couplings, is currently too weak for these models to be much morethan useful tools for research. Developing a basic scientific understanding of the coupledprocesses themselves is a paramount goal when it comes to modeling this class ofproblems. Accurate and complete field and laboratory data are also needed to develop,
test, and apply the improved models.
The roadmap activity below includes major tasks and significant status points fordeveloping the understanding and modeling capability for strongly coupled nonlinear
GHCB phenomena. Some of the status points refer to issues such as scaling andmanaging modeling uncertainty, which are discussed in later subsections of Section 3.
Some status points refer to the vadose zone Problem Solving Environment (PSE), a
software system environment and application toolkit discussed in Section 4.3.1.

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Activity CP3. Develop realistic representations for strongly coupled nonlinear
GHCB phenomena. Incorporate adequate models for these phenomena intransport models for vadose zone contamination sites.
•

Near-Term Status Point. Models have been formulated for strongly coupled
nonlinear GHCB phenomena with high priority for vadose zone
contamination studies. The modeled phenomena may include mechanics ofbiofilms; multivariate reaction kinetics; saturation and colloid-facilitatedtransport; and scaling of coupled processes in space and time.

•

Mid-Term Status Point. Constitutive theories and parameter databases forstrongly coupled nonlinear GHCB systems have been improved andincorporated into vadose zone contaminant transport models.

•

Mid-Term Status Point. Models for strongly coupled nonlinear systems
have been linked with scaling techniques.

•

Mid-Term Status Point. Mechanical-hydraulic and biochemical-hydraulicprototypes are available for use.

•

Mid-Term Status Point. Models for strongly coupled nonlinear GHCB
systems are supported in the PSE.

•

Task with Mid-Term Endpoint. Test proposed models for strongly coupled
nonlinear phenomena on synthetic test problems, in small-scale and mesoscale laboratory experiments, and at field-scale research sites.

•

Long-Term Status Point. Improved computational algorithms are available
for strongly coupled nonlinear GHCB processes.

•

Long-Term Status Point. Models for strongly coupled nonlinear GHCB
systems have been tested in field applications.

The following two status points apply to Activities CP1 through CP3.
Long-Term Status Point. Realistic models are available for all coupled GHCB
phenomena, including strongly coupled nonlinear processes, that areimportant to vadose zone flow and transport. These models cover allimportant time and space scales, and most of them are available within the
PSE.
Long-Term Status Point. Three-dimensional fully coupled heat and multiphaseflow and transport models are the norm for decision support.

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3.1.2.1

Highlights of Roadmap Results for Coupled GHCB Processes

Table 7 highlights some of the major results that can be anticipated from these threeresearch activities for studying coupled processes. The time horizons indicated in thetable are contingent on sufficient support and programmatic direction to accomplish thedetailed tasks and achieve the status points listed under the activities.
Table 7 Highlights of Results for Understanding and Modeling Coupled Systems Research Activities
Near Term

Mid Term

Long Term

The highest priority coupled GHCB processes have been identified.
We understand the strengths and weaknesses of existing models.
Some of the important strongly coupled phenomena can be modeled.
Process models for important strongly coupled phenomena have been validated andfield-tested across spatial and temporal scales.
Site assessment models incorporate all important coupled GHCB phenomena
realistically.

3.2

Combining Processes and Data at Different Scales in Integrated
ModelsMathematical models of processes governing fate and transport in the vadose zone areconstructed from mass, momentum, and energy balance statements. These statements
depend on constitutive theories that define how flow and transport variables depend on
material properties. Flow properties, including unsaturated hydraulic conductivity, water
retention curves, and others, are defined for a specific spatial and temporal scale. A
given process description, or the constitutive model representing it, does not explicitly
incorporate processes at other spatial and temporal scales.
Conventional process descriptions/models such as the Richards equation for flow are
established as useful representations for idealized uniform porous media. However, nosuch medium occurs in the natural subsurface. Many relevant subsurface properties
exhibit multiple nested scales of variability in both space and time. As scale changes, theappropriate process description changes. The constitutive properties needed for modelingacross scales are not uniquely defined. Consequently, constitutive theories relying on
property measurements on one scale may be of little or no use to simulation on otherscales affected by different flow and reactive transport processes.
Scaling issues affect boundary conditions, as well as the conceptual model and its
parameters. Of special concern for vadose zone models is the temporal scaling of highlyvariable climatic forcing functions, especially given the wide range of time scales ofinterest for prediction, from a few years for remediation to millennia for stewardship.
The critical questions in scaling include: (1) identifying the fundamental scales fordifferent GHCB processes, (2) describing these processes at an observable scale, (3)identifying the relevant or pertinent spatial and temporal scales of concern for decision
making, and (4) rescaling the processes to fit these parameters. The modeling exercise
must also be concerned with how to capture the data needed to answer these questions.
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Conventional scaling is often based on either physicochemical similitude overdifferent scales or contrived assumptions about variability. Neither approach is adequate
for fate and transport in structured soils and fractured rocks—media that are affected bydiscontinuities and preferential flow phenomena. Research on scaling must address not
only the multi-scale nature of GHCB processes and the basic properties that control them.
It must also accommodate the disparate scales of observations for characterization and formonitoring fate and transport. (Monitoring scales may be determined by regulations
unrelated to the scale of the controlling phenomena.)
The major endpoints envisioned for general improvements in modeling capability are
multidisciplinary scaling of constitutive theories; massive enhancements in deterministic
and stochastic scaling tools; hierarchical frameworks for multiple scales ofobservation/measurement; and comprehensive error analysis and adaptive scaling
methods. Among the focus areas for research are non-isothermal fate and transport, theoccurrence and impact of preferential multiphase flow in the vadose zone, fate andtransport in fractured media, and scaling episodically transient reactive transport in multiscale heterogeneous media via generalized coordinate systems. Both general and focusedresearch efforts must incorporate experimentation and measurements on appropriate
scales to test and validate scaling strategies in realistic environments. Finally, the scaling
results must be linked to the PSE and to advances in numerical methods (see Section 4.3).
Activity SC1. Develop simulation tools for vadose zone systems that provide ahierarchy of constitutive theories and that can simultaneously accommodate
multiple processes on different scales.
•

Near-Term Status Point. A Monte Carlo prototype for massive
deterministic simulations of scaling issues has been designed and developed.

•

Task Beginning Near-Term with Mid-Term Endpoint. Develop
extensions of the massively deterministic Monte Carlo method to include
probabilistic specifications of properties and constitutive hypotheses.

•

Mid-Term Status Point. The extended Monte Carlo modeling capability isin use as a testbed for evaluating scaling approaches and for advanced
quantification of errors associated with information loss in scaling.

•

Near-Term Status Point. Scaling is being used to provide quantification of
relevant processes by identification of global system variants, such as
contaminant trajectories and travel times, non-aqueous mobile phasegeometries, cumulative reaction histories over multiple time scales, andsubsurface ecosystem dynamics.

•

Near-Term Status Point. New deterministic and probabilistic/stochastic
approaches have been developed to address cross-scale issues that commonlyarise in vadose zone reactive flow and transport.

•

Task Beginning Near-Term with Long-Term Endpoint. Undertake
research to understand the time scaling of reaction systems and to solve
problems of transients, episodic behavior, and boundary conditions.

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Task with Mid-Term Endpoint. Refine computational techniques forsolving hierarchically scaled flow and transport models; test these techniqueswith meso-scale laboratory experiments, small scale field experiments, orother types of measurements of coupled GHCB processes.

•

Task with Mid-Term Endpoint. Develop scaling methods for flow in
generalized (transient and spatially non-uniform) coordinate systems toaccommodate processes that vary on multiple spatial and temporal scales.

•

Mid-Term Status Point. Research has provided linkages from constitutive
theories and scale of measurement to the quantities of ultimate concern todecision-makers. These linkages are in use for planning and implementing
characterization and monitoring activities.

•

Mid-Term Status Point (also a status point for Activity PSE2, in Section
4.3.1). Models for strongly coupled nonlinear GHCB systems are supported
in the PSE.

•

Task Beginning Mid-Term with Long-Term Endpoint. Develop links
between the scaling methods described above and the methods for uncertainty
estimation and reduction in the PSE.

•

Long-Term Status Point. Research is being done on spatial and temporal
scaling in support of source-identification, as well as other inverse problems.

•Long-Term Status Point (also applies to Activities CP1 through CP3 forcoupled GHCB phenomena). Strongly transient coupled GHCB processes atapplied field sites can be modeled over multiple time horizons.

•Long-Term Status Point. Aspects of scaling theory have been unified andcompletely linked with methods for uncertainty estimation and reduction in
the PSE.

Table 8 highlights major results that can be anticipated from this research activity,
given sufficient support and programmatic direction to accomplish the detailed tasks andachieve the status points listed under it.
Table 8 Highlights of Results for Combining Processes & Data at Different Scales Research Activities
Near Term

We can simulate scaling problems of important GHCB phenomena using
probabilistic modeling.
We can measure and model coupled GHCB phenomena across spatial scales.
Site models incorporate strongly transient and coupled GHCB phenomena for
multiple time periods.
Site models incorporate scaling with estimates of uncertainty, and the models canpropagate uncertainty estimates across spatial and temporal scales.

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3.3

Estimation and Reduction of Uncertainty

Uncertainty will always remain an issue with vadose zone models of flow andtransport, if for no other reason than the vadose zone is heterogeneous and difficult tocharacterize and monitor. Uncertainty comes from the incomplete answers to two
fundamental questions with which models must deal. First, what is an appropriate
conceptual model for the intended purpose, one that is neither too complex nor too
simplistic? Second, what are appropriate model parameters (e.g., properties), initialconditions, and boundary conditions? The answers to these questions depend,
respectively, on fundamental research on processes and process coupling and on
characterization and monitoring techniques. In addition, it is possible that subsurface
systems also have an intrinsic or irreducible uncertainty, due to the spatially andtemporally stochastic aspects of GHCB processes and the difficulty of observing theseprocesses without completely dissecting the system. How then is uncertainty traced
through the model and converted into quantities that decision-makers can understand,trust, and use?
Uncertainty in initial conditions, boundary conditions, and other model parameters is
now treated primitively, if at all. Spatial variability of some flow parameters issometimes simulated by generating simplistic alternative geologic realizations using
stochastic methods or by running Monte Carlo realizations. Recently, these realizations
have been conditioned by invasive and non-invasive monitoring and characterization
data, which is an improvement. Temporal variability due to climate changes can betreated similarly, although historical records are often used instead of current data. Morecommonly the flow is considered to be steady (independent of climatic fluctuation).
Most uncertainty stemming from the choice of a conceptual model is dealt withinformally, by an ad hoc process of deciding whether or not the model is “good enough.”
While formal inverse approaches to estimate parameters are being developed, there has
been much less attention paid to estimating boundary conditions (e.g., climate,meteorology, contamination source), and almost none to estimating appropriate
conceptual models. Some conceptual models are useful for answering certain questions
but fail miserably in attempting to answer others. An appropriate conceptual model
depends not only on the system but also on the questions being asked—it must be
pertinent.
Although Monte Carlo simulation is a computationally expensive method, it
demonstrates that uncertainty estimation is possible. Further, the use of conditioned
Monte Carlo realizations demonstrates that adding data can reduce uncertainty. Monte
Carlo simulation will always be an appropriate tool for some vadose zone applications,but more computationally (and theoretically) efficient alternative analyses for sensitivity
or uncertainty are needed, possibly based on more sophisticated probabilistic approaches.
Heterogeneity is a major source of uncertainty in vadose zone models. New theories
for describing and understanding the spatial and temporal structures of naturally
occurring heterogeneities and fluctuations are needed. Existing theories have not yet
contributed much to solving basic science or engineering problems. New links are
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needed between probabilistic description of the media and probabilistic measures of flow
and transport.
Improving the capacity to estimate and reduce uncertainties will lead to substantial
increases in confidence in our ability to make good decisions regarding remediation,
waste handling, or long-term stewardship. Models and approaches are also needed that
can automatically alert the user to possible limitations caused by uncertainty, just as canbe done for numerical error. For example, a modeling system could recognize that theconceptualization and the data are inconsistent (well beyond reasonable limits), suggest
possible explanations for the inconsistency, and even adapt corrections itself. With
formal uncertainty analysis and reduction methods, it should be possible to predict thevalue of new data, optimize the design and operation of characterization and monitoring
activities, and update a model automatically when new data become available. Thesedevelopments in uncertainty estimation, reduction, and application should beincorporated into the PSE (see Section 4.3.1).
Activity UC1. Catalogue, assess, and prioritize R&D needs for addressing thedifferent sources of uncertainty in models of vadose zone flow and transport.
•

Near-Term Status Point. State-of-the-art methods of uncertainty estimation
and reduction, especially for risk analyses, have been catalogued and assessed.

•

Near-Term Status Point. Sources of uncertainty in vadose zone modeling,including choice of conceptual model, geological heterogeneity; parametervalues; and initial and dynamic boundary conditions, have been quantified andR&D needs to address them have been prioritizedUncertainties contributed by geological heterogeneity in porous media
have been quantified and R&D needs prioritized.
Uncertainties contributed by dynamic boundary conditions related toweather and climate variability and predictability have been quantified andR&D needs prioritized.
Uncertainties contributed by characterization and monitoring methods,
including sample size, sample frequency, etc., have been quantified andR&D needs prioritized.
Uncertainties contributed by conceptual models of processes, especiallyoverly simplistic or incorrectly scaled process models, and incorrectly
coupled processes have been quantified and R&D needs prioritized.

•

Task with Mid-Term Endpoint. Develop and test new theories andmethodological approaches for describing and understanding the spatial andtemporal structures of naturally occurring heterogeneities and fluctuations.
Use advanced geological modeling to capture both flow-sensitive andchemical spatial heterogeneity.

•

Mid-Term Status Point. Uncertainties for flow models of highly
heterogeneous porous and fractured media, affected by the fracture-matrix

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interactions and by film flow in dry formations, have been identified andevaluated.
Activity UC2. Research to decrease uncertainties in vadose zone modeling.
•

Task with Near-Term Endpoint. Analyze existing long-term geological,hydrologic, chemical, and biological records to improve conceptual models,
reduce their uncertainties, and reduce or quantify the uncertainties in estimatesof parameters and boundary conditions used in vadose zone models.

•

Task Beginning Near-Term with Mid-Term Endpoint. Test candidate
methods for uncertainty estimation and reduction, and applications of thesemethods, on synthetic test problems, small-scale and meso-scale laboratory
experiments, and field-scale research sites.

•

Task with Mid-Term Endpoint. Evaluate effects of uncertainties forinvasive and noninvasive field characterization and monitoring methods withdifferent scales and degrees of resolution.

•

Mid-Term Status Point. Uncertainty estimation and reduction methods
resulting from the Activity UC2 tasks with mid-term endpoints (see above)
are in use as standard practice at several typical sites with vadose zone
contamination.

•

Mid-Term Status Point. New, more sophisticated and efficient probabilistic
approaches to uncertainty estimation and reduction have been developed andtested.

•Mid-Term Status Point. Uncertainty estimation and reduction methods arein use to predict the value of new data, to optimize the design and operation ofcharacterization and monitoring activities, and to automatically update amodel when new data becomes available.

•

Task with Long-Term Endpoint. Develop uncertainty and inverse methods
that self-adaptively suggest modified conceptualizations or parameterizations.

•Long-Term Status Point. Forward and inverse models accounting for
uncertainty are fully integrated into the vadose zone PSE.

Activity UC3. Improve computational methods for representing and propagating
uncertainties in vadose zone models.
•

Near-Term Status Point. Numerical algorithms have been improved toincrease the efficiency of vadose zone Monte Carlo simulations.

•

Mid-Term Status Point. More realistic treatment of uncertainties caused bysurface boundary conditions have been incorporated in vadose zone models.

•

Mid-Term Status Point. Support for uncertainty analyses has been
incorporated in the vadose zone PSE.

•

Mid-Term Status Point. Methods to display the degree of uncertainty fromdifferent sources and in aggregate (processes, coupling, parameters andRevision 0.0

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properties, variability, etc.) have been developed and incorporated in vadosezone system models. These methods exploit advanced visualization
techniques and other sensory (e.g., sound and touch) interactions with models
and data.
•

Mid-Term Status Point. Users of vadose zone system models areautomatically alerted to possible limitations caused by uncertainty.

•

Task with Mid-Term Endpoint. Link the analysis of modeling uncertainty
with practical problems of a facility designer. Integrate uncertainty estimation
and reduction with estimation and reduction of numerical errors. Incorporate
these modeling improvements into the vadose zone PSE.

•

Mid-Term Status Point. Uncertainty analysis has been coupled to
management models and the vadose zone PSE to help make decisions
concerning characterization, monitoring, and remediation design andoperation.

The following two long-term status points apply to all three activities for uncertainty
estimation and reduction. The first also applies to roadmap activities for modelingcoupled GHCB processes (see Section 3.1).
Long-Term Status Point (applies to Activities UC1–UC3 and CP1). Uncertainty
estimation techniques are incorporated in commonly used biogeochemical
models and models of multiphase flow in fractures.
Long-Term Status Point (applies to Activities UC1–UC3). Uncertainty estimation
and reduction are standard practice and are in use for characterization,
monitoring, remediation, and stewardship decisions.
Table 9 highlights some of the major results that can be anticipated from these threeresearch activities for measuring and reducing uncertainty. The time horizons indicatedin the table are contingent on sufficient support and programmatic direction toaccomplish the detailed tasks and achieve the status points listed under the activities.
Table 9 Highlights of Results for Estimation & Reduction of Uncertainty Research Activities
Near Term

We have identified and understand the sources of uncertainty for monitoring andmodeling vadose zone sites.
We have assessed and catalogued the state-of-the-art methods for estimating andreducing uncertainty.
We have developed and tested new probabilistic approaches for estimating andreducing uncertainty.
We can optimize characterization and monitoring systems to reduce uncertainty, andwe can predict the value of additional data for reducing uncertainty.
Site assessment models incorporate techniques for estimating and reducing
uncertainty in making decisions on site cleanup and stewardship.

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3.4

Improving Site Monitoring Systems

To this point in the roadmap, characterization and monitoring have been generally
paired, since both share many of the same tools and methodologies used to determine
vadose zone processes and measure vadose zone properties. An effective monitoring
program and a site-wide assessment performed with an integrated system model for acontaminated site complement each other and are equally important. In this section, thetwo are separated, in order to focus on the technology needed to improve site-monitoring
systems.
The Executive Committee believes that monitoring capabilities for vadose zone sites
must be a significant focus of roadmap activities. The committee foresees the thoroughtesting and adoption of improved methods for monitoring contaminated sites as one of
the two overarching, high-value payoffs from implementing the research and infrastructure-building activities in the roadmap. In fact, monitoring systems will benefit frommany of the near-term and mid-term results of the roadmap activities, and thus provide animportant payoff even sooner than integrated system modeling may. New monitoring
tools and methodologies will be integral parts of site restoration and remediation in thenear term, as well as on longer time horizons. These new tools and methodologies will
provide a backbone for long term stewardship, in which monitoring will be an essential
element in verifying that vadose zone contaminants have been removed or stabilized andthat migration toward groundwater aquifers is not occurring.
This section begins by distinguishing monitoring from characterization. Then it
describes the fundamental goals of monitoring and the basic requirements for amonitoring system. From this background, the section ends by specifying the technology
needed for developing new monitoring methods and the roadmap activities to producethat technology.
3.4.1

Monitoring Distinguished from Characterization

Characterization is typically associated with the initial investigation of a site.
Characterization data are often collected to identify how much of which contaminants arelocated where, as well as to provide a three-dimensional visualization of the structuralgeology and hydrogeology of the site. Equally important is the characterization ofboundary conditions, such as precipitation and temperature, and how these conditions
change with time. This initial visualization of the site often interprets the measurements
collected by reference to conceptual models of the subsurface strata and the GHCB
processes likely to be present. Quantitative models of individual or combined processes
and conditions may be initialized or parameterized with the characterization data, to aid
in the visualization effort.
Monitoring typically begins after a site has been characterized, to detect changes in
the location and concentrations of contaminants or changes in other GHCB conditions
that could affect contaminant fate and transport. Site monitoring is usually closely linked
with environmental cleanup and/or stewardship activities at the site, and the monitoring

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program typically must be reviewed and approved by an environmental regulator andother stakeholders. As with the initial visualization during site characterization,
monitoring requires a systematic approach that incorporates measurement tools with
optimization approaches, scaling and uncertainty analyses, and modeling of contaminantfate and transport.
3.4.2

Progressive Steps for a Monitoring System at a ContaminatedVadose Zone Site

Monitoring is a significant and essential component of any approach to site
environmental cleanup or stewardship. Table 10 lists the progressive steps forestablishing, operating, and completing a monitoring program. These steps address fourbasic questions: Where, What, How and What-if?
•

Where? The locations at which measurements are to be made, including
locations to track the presence of contaminants and locations that are required to
be within a standard of compliance.

•

What? The vadose zone processes, contaminant species, and possibly surrogates(tracers or other indicators of contaminant transport) for which measurements are
made to verify that the objectives of the approved site cleanup/stewardship plan
are being met or to trigger a contingency plan.

•

How? The techniques to be used for monitoring, the time scales, and thefrequency of measurements in the monitoring program.

•What-if? The action levels, reporting requirements, and contingency plans if theapproved cleanup/stewardship activities for the site fail to keep contaminants
within standards at the points of compliance.

Table 10 Progressive Steps for a Monitoring System and Program to Accompany
Federal Facility Cleanup and/or Stewardship Activities
Step
Description
Parties Involved
1. Establish where
Specify points of compliance and other points at which
Regional Administrator
monitoring will bemonitoring measurements are made.
located2. Define what is to be
Demonstrate that approved cleanup/stewardship activities
Site Operator and Regional
monitored(e.g., contaminant removal, natural attenuation, barrier cover) Administrator
are achieving expected results by including steps to:
1. Identify any potentially hazardous contaminants,
including transformation products;
2. Determine if a plume is expanding (either downgradient, laterally or vertically);
3. Ensure no impact to down-gradient receptors; detect
new releases of contaminants to the environment that
could impact the effectiveness of the planned
remediation ;4. Demonstrate the efficacy of institutional controls toprotect potential receptors;
5. Detect changes in environmental conditions (e.g.,hydrogeologic, geochemical, or microbiological) that
may reduce the efficacy of any of the processes requiredfor cleanup/stewardship to succeed; andRevision 0.0

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Step

3. Establish the time
period for monitoring(part of how)

4. Define howmonitoring is to be done

5. Define action levels
or processes to beobserved for monitoring(part of how)

6. Define actions to beaccomplished when
action levels orprocesses are observed(what if)

Description
6. Verify that cleanup/stewardship objectives are being
achieved.
Monitoring period should continue as long as contamination
remains above required cleanup levels and continue for a
specified period (e.g., 1–3 years) after cleanup levels havebeen achieved to ensure that contaminant levels are stable
and remain below target levels.
Demonstrate monitoring approach is appropriate and can beaccomplished verifiably by including steps to:
1. Specify methods for statistical analysis of data, e.g.,
established tolerances, seasonal and spatial variability;
2. Establish performance standards, such as:•
Collection and evaluation of performancemonitoring data for remediation methods in use at
the site;•
Monitoring natural attenuation performance;•
Standard test methods.
Currently available standard methods include those from theAmerican Society for Testing and Materials (ASTM) and
EPA standard methods.a
3. Establish a time interval agreed upon by regional
administrator or agency.
Include reporting maps, tabulation of data and statisticalanalysis, identification of trends, recommendations forchanges in approach, evaluation of whether contaminants
have behaved as predicted or other remedies are required.
Establish metrics for the monitoring system by including
steps to:1. Establish background levels;
2. Define what criteria shows that a plume is expanding or
diminishing;
3. Define what criteria shows that the conceptual model isapplicable to a site; and4. State the metrics of cleanup objectives andeffectiveness.
Establish action plan by including steps to:
1. Observe requirement to report to responsible party oragency if statistically significant variance occurs,
compared to background;
2. Identify extent and nature of non-predicted behavior(e.g., release);
3. Reevaluate conceptual model; and4. Evaluate feasible corrective actions from previous andevolving contingency plan.

Parties Involved

Regional Administrator

Site Operator and Regional
Administrator

Site Operator and Regional
Administrator

Site Operator will provide
details of the monitoring
program to EPA or the State
implementing agency aspart of any proposedmonitored naturalattenuation remedy.

a Applicable ASTM standards include Soil Pore-Liquid Monitoring (D 4696-92); Time Domain
Reflectrometry (D 6565); and Horizontal Applications of Neutron Moderation (D 6031). For further
listings and details, see Table 3.3, page 169, in Looney and Falta, 2000, or the ASTM website,<www.astm.org>. Representative EPA documents include EPA 1994a, 1994b, 1997, and 1999 in the
Reference section of this report.

Accomplishing the steps needed to establish improved monitoring system will dependon the confluence of many diverse technology paths in this roadmap. For example, newmonitoring approaches will require constant and rapid upgrading of sensors, field
optimization, and modeling methods.

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The monitoring locations for a federal facility are chosen by the Regional
Administrator (EPA or the State implementing agency), preferably using sitecharacterization data and the conceptual model (understanding) for contaminant fate andtransport at the site. These locations typically include the points of compliance, which are
the locations at which observation of a process or attainment of a standard can verify theaction of the remediation approach. Monitoring locations are also selected to allow
contingency actions to protect human and environmental safety if an action level isexceeded (the what if question).
In the future, the importance of allowing a “monitoring margin” for contingency
actions to protect groundwater resources is likely to move monitoring systems and plans
toward selecting points of compliance located between the contaminant source and thegroundwater. This imperative to protect the groundwater resource will place moreemphasis on vadose zone monitoring. As noted in the Introduction, the alternative ofcontrolling the groundwater within a contaminated zone is proving to be both more
expensive and less effective than containing contaminants within the vadose zone.
The how question includes demonstrating that the monitoring approach is appropriate
and verifiable.
3.4.3

Foundations for New Monitoring Approaches: Portfolio ofConceptual Models, Monitoring and Characterization Data

Long-term monitoring of vadose zone contamination must verify contaminantisolation by reliably detecting unintended releases. Monitoring must also detect changes
in geological, hydrologic, chemical, and biological parameters and process rates. These
capabilities should be developed through an iterative process, continually updating site
conceptual models with new monitoring data and interpretation. New and continuingmonitoring data will be invaluable in defining and confirming conceptual models; thedata will also aid in determining the continued value of a particular model.
It is essential to link monitoring explicitly to contaminant fate and transport models
before monitoring starts, so that subsequent monitoring efforts achieve their purpose. To
facilitate this linkage, a portfolio of models, grouped by contaminant type, should be
developed. Grouping by contaminant type has proven to be a good way of organizing
this approach. Such portfolios and system knowledge gathered from them provide thefoundation to answer the basic questions of what, where, how, and what-if.
There should also be an effort to cull from the set of standard monitoring approaches
those that cannot conceivably update or refine the catalogue of chemical fate andtransport models of a specific contaminant. This culling is important for minimizing datacollection that is likely to be of decreasing value (orphaned data) as iterative
improvement of monitoring systems and site models progresses.

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Activity MON1. Build, catalogue, and update conceptual models for fate andtransport of vadose zone contaminants, using field data on specificcontaminant plumes to select and improve models for the catalogue.
•

Near-Term Status Point. At least 2 or 3 conceptual models for fate andtransport of particular contaminants, including contaminants of particularinterest to DOE, have been built, catalogued, and updated using field data on
specific contaminant plumes from DOE sites or other vadose zone
contamination sites.

•

Mid-Term Status Point. Field measurements from within and outside theDOE complex have been compiled to provide broad-based technical support
for the catalogue of fate and transport models. Characteristic transportdistances, chemical controls on attenuation, and hydrologic factors have been
determined on a site-specific basis, but these features have been usedcollectively to update the conceptual models in the catalogue.

•

Mid-Term Status Point (also applies to Activity MON3). Contaminantspecific monitoring needs have been catalogued. Current “standard”
monitoring approaches that cannot conceivably update or refine the catalogueof conceptual models for attenuation of a specific contaminant have been
identified.

Activity MON2. Coordinate effort to collect long-term monitoring lessons learned
from across DOE sites and from other agencies with monitoring experienceand expertise.

3.4.4

•

Task with Long-Term Endpoint. Use the gathered monitoring data andlessons learned to institutionalize a reflexive and iterative linkage between
monitoring and model refinement•

Task beginning Mid-Term with Long-Term Endpoint. Use the gathered
monitoring data and lessons learned to (1) condense the catalogue ofconceptual models for contaminant attenuation/fate and (2) standardize
monitoring approaches.
Contaminant Fate and Transport Monitoring

Many of the remediation alternatives for existing contaminated sites ordecommissioned facilities will leave residual wastes in place. Such residual or stabilized
contaminants require assessment of their potential to migrate through the vadose zone.
Methods for monitoring these potential sources are important because, once wastes are
released to the heterogeneous subsurface, containment is extremely problematic andremediation is very expensive. A huge gap exists between the state of the art in
implementing monitoring systems and the state of practice at most sites of significant
vadose zone contamination, including the DOE cleanup sites. This gap needs to be
narrowed. Also, new monitoring approaches are an integral part of verifying theeffectiveness of remediation, including triggering and defining appropriate contingency
actions (addressing the what-if question).
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To date, there have been limited studies of non-invasive and non-point methods ofidentifying and monitoring contaminants. There are currently no techniques formonitoring real-time changes in source contaminant configuration (e.g., migration ofcontaminants in the vadose zone below disposal cribs or tanks).
Activity MON3. Define monitoring requirements and improve/develop monitoring
approaches for chemical contaminants, including changes GHCB frameworks
and boundary conditions.

3.4.5

•

Near-Term Status Point. Integrated field-tests of integrated (multiple
sensors, system optimization, coupled to conceptual models) monitoring
systems at integrated field-test sites or actual site undergoing remediation or
in closure stage. Begin incorporation of new sensors into monitoring system•

Mid-Term Status Point. A cost-effective real-time monitoring and data
analysis system has been developed that provides early warning ofcontaminant discharges to the vadose zone.

•

Mid-Term Status Point. New sensors and emplacement methods can beincorporated cost-effectively into monitoring systems, to move state-of-the-art
technology into the state of practice at cleanup and stewardship sites.

•

Mid-Term Status Point. Contaminant-specific monitoring needs have beencatalogued. (See related status point for Activity MON1.)
Highlights of Roadmap Results for Improving Site Monitoring
Systems

Table 11 highlights some of the major results that can be anticipated from the threeresearch activities for improving site monitoring systems. The time horizons indicated in
the table are contingent on sufficient support and programmatic direction to accomplish
the detailed tasks and achieve the status points listed under the activities.
Table 11 Highlights of Results for Improving Site Monitoring Systems Research Activities
Near Term

M id TermLong Term

Several conceptual models for fate and transport (beginning a catalogue) have beenvalidated with field data representing an emerging set of standard monitoring
approaches.
Researchers, site operators, regulators and stakeholders can access a catalogue of
proven fate and transport models with data sets for priority vadose zone cleanup sites.
Real-time monitoring systems at sites with vadose zone contamination provide early
warning of contaminant discharge or movement.
The model catalogue has been condensed and updated, and monitoring approaches
have been standardized.

3.5

Model Integration and Validation at the System Level.

To address the national problems of vadose zone contamination, the processes andproperties that control flow, transport, and transformations must be understood,
measured, and ultimately incorporated in validated predictive tools whose results affectremediation and stewardship decisions. Data from myriad characterization techniques,both non-invasive and invasive, will likely be integrated over many iterative cycles to
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achieve site-specific multidisciplinary models whose predictions (summary results ofsimulation runs) consistently honor all data and their uncertainties.
Rigorous testing of model output, or predictions, is critical to building confidence inthe characterization methods and data, as well as validating the conceptual models andnumerics incorporated in the integrated models that produce the predictions. Quantities
simulated by mathematical models (e.g., pressure and concentrations) are more readilymeasured than are many model input parameters (e.g., boundary conditions like
infiltration, or properties like hydraulic conductivity and porosity). These simulated
quantities are therefore often easier to test in controlled experiments or in the field.
By contrast, estimates of model input parameters are often made using inverse
modeling, an approach plagued by problems of instabilities, non-sensitivities, and nonuniqueness. In addition, parameter estimation procedures are still frequently usedwithout probabilistic representations to account for the uncertainties in these procedures.
The resulting “point value” parameter estimates are rather meaningless, since not muchcan be said about the relationship between the estimated and true parameter values.
Consequently, the underlying uncertainty in the estimates cannot be propagated in areasoned way into estimates of the uncertainty, or the sensitivity, of predictions from theintegrated model. Data collection programs are still regularly designed without studying
beforehand the sensitivities of key model input parameters to measured variables.
These limitations constrain the capacity to test and validate a model thoroughly. The
constraints are particularly serious when the model is to be used for long-term
predictions. For such uses, even though model output may be measurable in principle, itcannot be tested, and therefore validated, until years after critical decisions have been
made and acted upon. To address these limitations, requirements for integration andvalidation must be designed into each step of the process and rigorously implemented.
The modeling process consists of the following four general steps: (1) develop a
conceptual model, (2) formulate a mathematical model, (3) implement solution
techniques, and (4) perform model verification and testing. Errors in the conceptualmodel can lead to errors in predicting and understanding vadose zone flow and transport.
Alternative conceptual models are proposed when lack of data or process understanding
precludes unique identification of a single model, site characterization defines a newfeature or process, or model testing rejects a candidate conceptual model. A major
barrier to identifying alternative conceptual models is the design and execution ofexperiments that discriminate among various models.
Definition models must be integrated with data from characterization and monitoring
activities. The resulting site-specific description of a vadose zone system must be
validated to ensure that a model is performing adequately for its intended uses. The dataneeded to test the models can come from a variety of sources.
•

Synthetic (computer-based) test problems provide the only data sets in which all
aspects of the system are known.

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Integrated meso-scale laboratory and field experiments provide a higher level ofrealism, but with gaps in even the most exhaustive database.

•

Finally, applying the model to site studies provides the ultimate reality test, but leaves
even larger data gaps.

Integrated system models should be tested and validated in each of these test
environments. Special attention should be paid during testing to comparative studies ofvarious approaches to inverse modeling and estimation.
To improve integrated system models and assist with integration, new inversion
techniques must be developed to estimate parameters and boundary conditions.
Traditionally parameters (e.g., properties) have received the most attention, usually understeady-flow assumptions. Transient data generally reduce the uncertainty in parameter
estimates and can overcome problems of identification. The new methods should couple
transient flow and transport processes, together with other characterization information,in large-scale joint inversions. As part of the PSE (see Section 4.3.1), it would be usefulto establish a computational test bed to validate models consistently against relevant data.
Using the synthetic problems, well-controlled meso-scale experiments, site data, andpossibly other means, integrated system models should be tested and validated withrespect to three major criteria:
1. Does the model consistently honor all available data and understanding of processes?
2. Are the model and data adequate to make the desired predictions?
3. Where would new or additional data most likely improve model performance?
New measures of model performance, based on these criteria, are needed.
To apply integrated system models to sites, the entire modeling approach should be
integrated with data through an appropriate geographical information system (GIS). The
GIS should provide tools and methods for managing data in space and time, including
special interrelationships and uncertainties. Such GIS tools could be an integral part of
the PSE or simply linked to it. Site considerations also suggest the design, building,testing, and updating of a shared vadose zone model that contains a subset of features of
the PSE sufficient for dealing with most vadose zone problems. It, rather than the parent
PSE, could become the main vehicle for model application and decision support at sites.
The following four roadmap activities address these needs for integration andvalidation throughout the stages of designing, implementing, and applying a site-wide
integrated system model for priority vadose zone sites, such as the long-term DOE
cleanup and stewardship sites. Table 12 highlights major results that can be anticipatedfrom these activities, given sufficient support and programmatic direction to accomplish
the detailed tasks and achieve the status points listed under them.
Activity IV1. Improve and test techniques: (1) for estimating model input
parameters, including boundary conditions and properties that control flow

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and transport and, (2) for model integration, through improved measurement
system design and/or improved inverse modeling of input parameters.
•

Task with Near-Term Endpoint. Develop models of sampling events andinstrument response, to be used to improve instrument design, for a variety ofinvasive and non-invasive methods for characterization and monitoring.

•

Task with Near-Term Endpoint. Develop new inversion techniques for
estimating the input parameters in models of transient flow and transport
processes.

•

Task with Long-Term Endpoint. Design and conduct controlled field
experiments that distinguish among conceptual models representing different
sides of issues in vadose zone flow and transport.

•

Mid-Term Status Point. Improved methods for inverse modeling andestimating probabilistic uncertainty have been tested through meso-scalelaboratory and field-scale experiments.

•

Long-Term Status Point. A highly integrated Shared Vadose Model has
been developed, validated, and is being applied. This model is a subset of the
PSE in which the value of new data is continually assessed as part of anobservation–prediction–decision support (cost analysis) process.

Activity IV2. Develop new tools to test and validate vadose zone models andtechniques, such as inversion methods, for integrating data and estimating key
parameters.
•

Task with Near-Term Endpoint. Define synthetic test problems and use
them to conduct comparative studies of existing techniques for inverse
modeling and model validation.

•

Mid-Term Status Point. Integrated meso-scale laboratory and field
experiments have been performed to build databases suitable for testing andvalidating specific models.

•

Mid-Term Status Point. A computational test bed to assist in testing andvalidating models has been incorporated into the vadose zone PSE.

•

Mid-Term Status Point. Support for inverse methods and for decision
support simulations has been added to the PSE.

•

Mid-Term Status Point. Geographical information systems have been linked
with, or otherwise functionally incorporated into, the PSE.

Activity IV3. Conduct vadose zone field experiments to test and refine models andmeasurement techniques, including advances in instrumentation, tracers,
biological properties, and emplacement technologies, as well as mathematicaland statistical bases for design.

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Long-Term Status Point. Models can be tested by comparing model
predictions to short-term (and eventually long term) field observations fromfield test sites and monitoring networks at contamination sites.

Activity IV4. Apply improved methods and tools for integration and validation toreal-world problems of managing vadose zone contamination.
•

Mid-Term Status Point. Model testing and validation methods are being
applied at major vadose zone contamination problems, including DOE sites.

•

Long-Term Status Point. Better inverse methods for estimating parameters,boundary conditions, and the uncertainties in these estimates, and bettermethods for conceptual model validation, have been developed and validated
using synthetic problems, experiments, and site data. They are being used to
guide characterization and monitoring activities at sites with major vadosezone contamination problems, including DOE sites.

The following status point applies to all four Integration and Validation activities.
Long-Term Status Point (applies to Activities IV1–IV4). Models are an effective
bridge to visualize and communicate findings from scientists to policy-makers
and stakeholders.
Table 12 Highlights of Results for Integrating and Validating Site-Wide Models Research Activities
Near Term

We can compare modeling techniques using a standard set of synthetic test problems.
We have models for sa mpling events and instrument response to improve
instrumentation and network design for characterization and modeling.
We can test and validate models and measurement methods in laboratory and field
experiments following standard protocols.
Site-wide assessment models are credible to both scientific and public policy
communities.

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4.0

NECESSARY SUPPORTING CAPABILITIES AND
INFRASTRUCTURE

The results of the research activities outlined in Sections 2 and 3 will be
improvements in our understanding and our capability to monitor and model the fate andtransport of subsurface contaminants. To pursue these activities effectively and achieve
the anticipated results within the time horizons indicated, researchers and developers
need capabilities and facilities that do not yet exist. Some of these are unlikely to
become available without concerted attention and directed resources. Others will become
available much sooner, and provide a more powerful boost toward achieving major
results, if they are developed systematically rather than emerging haphazardly. The
Executive Committee refers to these enabling capabilities and facilities as theinfrastructure for vadose zone S&T.
4.1

Generating and Compiling the Data for a Four-Dimensional GHCB
Framework

All scientific endeavors require data to validate hypotheses, create models, andconfirm or alter theories. For vadose zone science, data are also essential for developing
and verifying simulations of past events and forecasting future conditions.
Characterization and monitoring methods provide data that are crucial to understanding
vadose zone processes, testing predictive models, and confirming performance of the site
relative to regulatory and risk levels. Good data are essential for making good decisions
about site remediation and long-term stewardship. Characterization of vadose zone
processes and heterogeneities provides the data required to develop accurate simulations
with the appropriate spatial resolution. Monitoring contaminant migration confirms theaccuracy of simulations and can trigger remedial action.
In this section, the capabilities and infrastructure needed to generate these data andmake them widely accessible are discussed under four headings:•

Virtual Library of GHCB Data,•

Sensors, Instrumentation, and Emplacement Techniques,•

Design and Optimization of Measurement Networks, and•Field Facilities to Support Integrated Testing and Validation of Research.

4.1.1

Virtual Library of GHCB data

As explained in Section 2.1, the characterization and monitoring data for acontaminated vadose zone site must be adequate to provide a four-dimensionaldescription (three spatial dimensions plus time) of the relevant processes and parametersin the vadose zone. A description of this kind depends on integrating measurement data
and their interpretation across multiple traditional disciplines, including geology,hydrogeology, soil science, geochemistry, biology, geophysics, and geomechanics. In

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this roadmap study, an inclusive structure within which all these data types can be
integrated is called a geological, hydrologic, chemical, and biological (GHCB)
framework. Creating the four-dimensional descriptions for contaminated vadose zone
sites will require concerted efforts to improve and create the tools and techniques tocollect, qualify, correlate, and make accessible the data needed to implement a GHCB
framework.
The focus for these efforts should be a GHCB virtual library, a virtual database ofgeological, hydrologic, chemical, and biological parameters as a function of geologicalenvironment. The GHCB virtual library could be implemented in several different ways.
For example, it could be decentralized among a number of physical locations or more
centralized. However implemented, it must be widely accessible to the communities
engaged in research, site operations, regulatory oversight, and public involvement. It
must accommodate multiple uses in characterization and monitoring activities, as well as
provide a source of input data to numerical models for vadose zone system simulations.
The basics for a roadmap activity for creating a GHCB virtual library are highlighted
in the following activity.
Activity G1. Build and extend a virtual library of qualified GHCB data.
•

Task with Near-Term Endpoint. Tabulate known GHCB features forpriority sites with vadose zone contamination and representative GHCB
characteristics.

•

Near-Term Status Point. GHCB virtual library is operational and contains
qualified GHCB data for key sites with vadose zone contamination problems.

•

Near-Term Status Point. Scale parameters are being reported to the GHCB
virtual library, as well as measured values and distributions. Vadose zone
scientists are comfortable interpreting their measured data using a hierarchicalstructure of organization that can exist in natural geological environments.

Quantitative GHCB models are populated using site-specific information. However,they are difficult to develop for unsaturated systems and require a significant investment
in data collection, interpretation, and interpolation. Development is an iterative process
in concert with numerical simulation of flow, transport, transformational processes, anddata collection.
Activity G2. Develop prototypical numerical models that can be used to implementsite-specific four-dimensional GHCB framework models incorporating siterelevant GHCB parameters and processes.
•

Mid-Term Status Point. Prototype GHCB models are available that run with
GHCB virtual library data and/or other suitably structured datasets.

•Long-Term Status Point. GHCB models and virtual library datasets areadequate to simulate the critical features, parameters and processes for the
DOE vadose zone problem sites and other sites of national interest. The

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simulations of flow and transport are consistent with all existing qualified dataand observations.
Table 13 highlights major results that can be anticipated from the activities to develop
a GHCB virtual library and quantitative GHCB models. The time horizons indicated in
the table are contingent on sufficient support and programmatic direction to accomplish
the detailed tasks and achieve the status points listed under the activities.
Table 13 Highlights of Results for GHCB Data Library and Model Set Infrastructure Activities
Near Term

M id TermLong Term

A virtual library of qualified GHCB data for priority contaminated sites is available
to researchers, site operators, regulators, and the policy communities.
Virtual library data can be run on prototype models that incorporate a GHCB
framework.
We can si mulate critical features of priority contaminated vadose zone sites using
GHCB models and virtual library data.

4.1.2

Advances in Sensors, Instrumentation, and Emplacement

Limitations of Current Invasive Techniques. The nature of invasive vadose zone
characterization and monitoring requires access to the subsurface through boreholes,
trenches, or other excavations. While this direct access enables more direct
characterization at many scales, it also has drawbacks, including:•

Problems of Access. Some contaminated sites contain high concentrations ofchemical or radiological hazards that carry an exposure risk for workers involved indrilling or sampling at the site. Therefore the activities and movement of personnel
and equipment must be carefully controlled and monitored to limit exposure.

•

Effects on Flow and Contaminant Transport. Drilling, direct push, and other methods
create new pathways for flow and contaminant migration.

•

Effects of Sampling. The direct access methods directly perturb the soil and rock,therefore altering the processes and parameters of interest.

•

Maintenance of Characterization and Monitoring Systems. Reliability of existing
technology/instrumentation is an issue for monitoring over long time periods.

•

Data Communications. Longer-term characterization and monitoring requires new
approaches for communicating data from the subsurface and for minimizing or
automating the data recording to selected intervals.

•

Need for Improved Sensors. Over the next 25 years, there will be a revolution insensor devices. The market for environmental restoration may not drive this new
generation of sensor development. However, the environmental communities mustfind ways to influence the development of these sensors for new applications, so they
can leverage the anticipated growth of this technology.

Research and development of new sensors, improved emplacement of new andcurrent sensors, and novel emplacement approaches are key to enabling invasive

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characterization and monitoring. Also, research and development of new sampling
methods for fluids, rocks, or soils are needed to reduce the effects of sampling
disturbance and to reduce the impacts on the existing flow and transport system.
New Sensors. Over the next 25 years, there will a revolution in sensor devices. The
advent of devices on the scale of microns and nanometers (microdevices andnanodevices) will generate opportunities for characterization and monitoring in thesubsurface. These devices, along with advances in optical fiber sensors, will analyze
chemical, biological, and flow processes. Examples currently appearing include“chemical laboratory on a chip” sensors and new geophysical sensors such as
accelerometers. Microdevices will provide opportunities to gather data at more points
per subsurface volume but at lower cost. New technologies for in-situ analysis of
bioactivity will be continually developing over this period.
The market for environmental restoration may not drive the development of this new
generation of sensors. However, to exploit the opportunities for leveraging theseadvances in sensor technology, the environmental communities must develop ways todirect the application of these sensors to subsurface characterization and monitoring ofvadose zone (and groundwater) problem sites.
Improved Emplacement. In the near term, enhancements to instrumentation forexisting technology, such as cone penetrometers, are needed. Gradually, between 2004
and 2025, new technologies such as microdrilling (1-inch diameter heads with their own
coil tubing) are likely to find more application to vadose characterization and monitoring.
Some of these technologies are already being developed for defense applications andfossil energy characterization. Microdrilling brings new capabilities in terms of size,
cost, directional emplacement, and custom-composite tubing. Custom tubing can havebuilt-in or attached microsensors and conduits for communication and sampling. In thelonger term, autonomous drilling or miners, such as those developed for planetary probes(e.g., the Mars drilling program) and defense applications, will become available toaddress some emplacement needs in vadose zone characterization and monitoring. With
these improved emplacement methods, new technologies for isolating boreholes andintrusions will be required.
Novel Emplacement Approaches. Over the next several decades, the vadose zone
community must be prepared to adopt and adapt new and possibly revolutionary
technologies as they emerge. For example, as sensors are miniaturized to micro and thennano scales, it may be possible to inject simple binary sensors that are pore size or
smaller (similar in size to a colloidal particle) into soils or unconsolidated formations.
These simple sensors could remain dormant until a chemical or environmental condition
occurs, in response to which they emit a detectable signal. Other possibilities include
miniaturized penetrators that can be shot into formations from boreholes, after which theywould act as autonomous sensor packages.
Three roadmap activities to provide these capabilities are listed below. Table 14
highlights major results that can be anticipated from these activities, given sufficient

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support and programmatic direction to accomplish the detailed tasks and achieve thestatus points listed under them.
Activity SIE1. Understand the effects of sensor emplacement and apply thisunderstanding to improving sensor emplacement approaches.
•

Near-Term Status Point. Methods for minimization of emplacement effects,
such as microdrilling and coiled tubing, have been demonstrated successfully
at important sites of vadose zone contamination, including DOE sites withhigh levels of radiological and chemical hazards.

•

Near-Term Status Point. New drilling techniques for sampling and forsensor emplacement have been developed and tested.

•

Task with Mid-Term Endpoint. Develop minimally invasive methods andapproaches to correcting for emplacement effects.

•

Long-Term Status Point. Non-invasive methods or methods to fully correct
for emplacement effects are available for all characterization and monitoringneeds.

For both characterization and monitoring, smaller sensor packages are of value forseveral reasons. If small, injectable sensors can fill in the data gaps between boreholes,
they can increase the spatial density of data without the added cost and potential intrusionof adding more boreholes. For monitoring systems, even simple binary sensors can act assentinel clouds in the vadose zone, triggering a response when a contaminant reaches
them at a preset concentration or when a fluid pulse moves under a landfill cover. Smallis also good because it enables mass manufacture, decreasing cost per sensor, making
sensors disposable. Miniaturization also eases the implementation of multiple sensor
types in one package.
Activity SIE2. Improve cost-effectiveness of sampling and sensor emplacement
techniques.
•

Task with Near-Term Endpoint. To decrease cost and improve spatial
resolution, develop sensors that can fit in existing boreholes.

•

Near-Term Status Point. Deployable prototype sensors are small enoughthat 10 sensors can fit inside a 2-inch diameter hole.

•

Mid-Term Status Point. Cheaper, smaller, and more robust subsurface
location devices have been developed and are available for use.

•

Mid-Term Status Point. Prototype field sensors using alternatives toboreholes (cone penetrometers, new emplacements, microdrilling,
autonomous devices, penetrators, injectable microdevices) are being deployed.
These sensors are small enough to support 50 channels of output data in asensor that fits in a hole the size of a rice grain.

•Long-Term Status Point. Injectable sensors and smart sensors are available
as off-the-shelf technology. These low-cost sensor technologies provide

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continuous spectrum coverage, are the size of a soil pore, and require little
maintenance.
The following three status points apply to both Activities SIE1 and SIE2.
Near-Term Status Point (applies to Activities SIE1 and SIE2). The geology andhydrology of a contaminated site can be characterized at a 10-meter scale
throughout the top 50 meters of the subsurface, using methods that have abouta one-month turnaround time for processing and interpreting the fieldmeasurements.
Mid-Term Status Point (applies to Activities SIE1 and SIE2). The geology andhydrology of a contaminated site can be characterized at a 1-meter scale
throughout the top 50 meters of the subsurface, using methods that have abouta one-day turnaround time for processing and interpreting the fieldmeasurements.
Long-Term Status Point (applies to Activities SIE1 and SIE2). The geology andhydrology of a contaminated site can be characterized at a 1-meter scale
throughout the top 50 meters of the subsurface in real time for most sites.
Table 14 Highlights of Results for Sensors, Instrumentation & Emplacement Infrastructure Activities
Near Term

Mid Term

Long Term

Prototypes of miniaturized sensors are small enough to fit a package of 10 inside a
two-inch hole.
We can characterize the geology and hydrology of a site at a 10-meter scale with one
month turn-around.
Techniques to minimize emplacement effects have been developed and tested.
Minimally invasive emplacement methods and miniature sensors are available asalternatives to conventional boreholes and instrumentation techniques.
We can characterize the geology and hydrology of a site at 1-meter scale with a one
day turn-around.
Injectable, smart sensors are available off the shelf; non-invasive methods formeasuring key flow and transport properties are available.
We can characterize the geology and hydrology of a site at 1-meter scale in real-time
for most sites.

4.1.3

Design and Optimization of Measurement Networks

Network Design
Subsurface characterization and monitoring for contaminants is difficult andexpensive. Research in network design is needed to answer two significant questions:(1) How can we get the most information about subsurface contamination with the fewest
boreholes, monitoring devices, etc.? (2) For compliance monitoring, how can we be surethat the vadose zone monitoring system will indeed detect if there is a leak ofcontaminants from an engineered waste disposal site?

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Design approaches for monitoring networks, including krieging, pattern gridding, andothers, aim for optimal placement of sampling points for detection monitoring at disposalsites. However, many of the models used for designing a compliance monitoring systemhave been developed for groundwater monitoring. Because of this regulatory emphasis on
groundwater monitoring and the lack of requirements for vadose zone monitoring, vadosezone compliance monitoring has not had the sustained research focus needed to advance.
The state of practice needs to be reviewed in the area of subsurface monitoring
system design. An optimization methodology for subsurface characterization needs to be
developed that is based on flow and transport characteristics of the vadose zone at thedisposal site. Finally, compliance monitoring designed to detect contaminant transport
within the vadose zone should be encouraged. For sites where protection of valuable
groundwater resources is an issue, it should be required.
Assessing the Value of Data
Vadose zone characterization and monitoring technology is evolving rapidly,
presenting many options in developing and managing environmental sites for remediation
or long-term stewardship. Among these options are “high tech” parameter-measurement
approaches (e.g., three-dimensional and time-lapse three-dimensional geophysicalsurveys), novel emplacement methods, and advanced sensors. Today’s environmental
management team must be able to use new technologies and methods that have been
designed to provide better and more accurate information about the site in question. At
present, however, there are no objective means to evaluate environmental technologies.
Research should be focused on developing a system (e.g., a decision support system) withwhich environmental managers can readily and rapidly prioritize locations forcharacterization and monitoring activity and allocate discipline-specific expertise andother resources.
The following roadmap activity incorporates research needed to design optimal
monitoring networks for the vadose zone and assess the value of environmental
characterization and monitoring technologies relative to site-specific objectives. Table 15
highlights major results that can be anticipated from this activity, given sufficient support
and programmatic direction to accomplish the detailed tasks and achieve the status points
listed under it. The role of numerical laboratories, mentioned in Activity ND1, isdiscussed in the next section, on facilities for integrated field experiments.
Activity ND1. Develop, test, and apply methods for optimizing vadose zone sensor
networks to meet end users’ needs for characterization, site-wide assessment,
and monitoring information within user-specified constraints of uncertainty
and cost.
•

Task with Near-Term Endpoint. Create a numerical laboratory, combinedwith highly instrumented field sites, for assessing sensor networks and data
value. Define numerical experiments to assess the value of data.

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Task with Near-Term Endpoint. Develop methods to determine thesensitivity of key parameters to sensor network design (and indirectly, cost).

•

Task with Near-Term Endpoint. Determine how design and optimization of
sensor networks can reduce uncertainty, taking into account the factors of
sensor network cost, data density, and subsurface depth.

•

Mid-Term Status Point. The numerical laboratory has been upgraded andcan now be combined with field data to apply methods for network sensor
design to field-scale tests and experiments.

•

Task with Mid-Term Endpoint. Develop methods to identify controllingparameters.

•

Mid-Term Status Point. The geophysical method or combination of
methods that is most cost-effective for characterizing different geologicalenvironments or dynamic processes can be determined.

•

Long-Term Status Point. Sensitivity to network design can be quickly
determined for complex-wide sites.

•

Long-Term Status Point. Network design and optimization methods areused to convey to end users the cost, data density, and level of investment
needed to reduce uncertainty to specific levels.

Table 15 Highlights of Results for Design & Optimization of Measurement Networks Infrastructure Activities
Near Term

Mid Term

Long Term

We can access a numerical laboratory linked with instrumented field sites to conduct
experiments on characterization/monitoring network design and data value.
We can use field data in a numerical laboratory to optimize monitoring networks forfield-scale experiments.
We can use network optimization design methods to explain cost-benefit risks andother trade-offs to end users, as part of planning for long-term monitoring and site
assessment activities.
We can quickly determine the location sensitivity and data value for designs ofmonitoring and characterization networks.

4.2

Field Facilities to Support Integrated Testing and Validation of
Research

A number of the research activities presented in Sections 2 and 3 specify integrated
field experiments (IFEs) as the means to achieve important results.14 This section
describes the kinds of facilities required for these experiments. It also explains why thefacilities and the IFEs are crucial to achieving many of the mid-term and long-term
results of research described elsewhere in this roadmap.

14

See Activity PH2; Activity CH4, long-term status point; Activity SC1, mid-term task forhierarchically scaled flow and transport models; and Activities IV1 through IV4.

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4.2.1

The Role of Field Experiments in an Integrated Approach to
the Vadose Zone

A central theme of this roadmap is the importance of providing an integrated fourdimensional data framework and site-specific models for the vadose zone. This
integration must incorporate process knowledge and site-specific data from acrosstraditional disciplines. Important requirements for this integration include the capability
to determine the relevant parameters to be measured at site-specific locations and thecapability to select characterization and monitoring methods (including frequency ofmeasurement) optimized for those locations. As part of determining the value of data,capabilities are needed to compare the cost with the benefit of additional data, including
the precision required, for specific parameters and locations. When a lack of data orprocess understanding leaves doubts about the best process representation, well designed
and controlled field experiments can discriminate between alternative conceptual models
crucial to building a successful site-wide model.
Multidisciplinary field experiments, if focused on answering specific questions or
hypotheses regarding vadose zone processes, provide a means for testing and validating
both the components being integrated and the integration methodology. However, to test
the data framework and models, the experiments must be run in a reasonably wellcharacterized environment, so that test results can be compared against a validated“ground truth” for that site. Thus, to get the most value from IFEs, they should be
conducted at sites whose GHCB characteristics are reasonably well known and can bemonitored during the course of the experiment.
After the model representations, site-specific boundary conditions and parameters,
and the monitoring network have been validated through an IFE, the resulting integrated
model can be extrapolated forward in time to assess the risks associated with impacts on
groundwater and other routes for environmental and health exposures. Scenarios can be
run to examine remediation alternatives, such as the impact on contaminant transport if
an engineered barrier is placed over subsurface waste.
In these experiments, “everything comes together.” IFEs conducted at suitable sites
will allow a broad range of hypotheses to be tested and tentative results (from laboratory,small field-scale, or computer-based research) to be assessed (disconfirmed or validated).
An infrastructure of facilities for conducting IFEs would bring together and amplify
much of the research described in Sections 2 and 3. It would also complement otherelements of infrastructure, such as the GHCB virtual library and the vadose zone Problem
Solving Environment, described elsewhere in Section 4. Among the many kinds ofresearch questions and results amenable to exploration with well-designed IFEs are thefollowing:

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New sensing technologies, both invasive and non-invasive;•

Monitoring and characterization strategies and techniques, including sensor network
design and optimization for environments similar to the test site;•

Conceptual models that represent hypotheses about underlying processes andproperties, as well as coupling of processes in specific conditions and subsurface
environments; and•Site-wide integrated models incorporating multiple process models and running with
GHCB boundary data derived from characterization studies and monitoring networks
for that site.

For example, an IFE could be set up as a scenario that may occur during cleanup of acontaminated site, such as discovery of a previously unknown waste burial ground. The
experiment’s objectives would include characterizing what is leaking and how fast it ismoving horizontally and vertically in the vadose zone, predicting where it will go, andestablishing an appropriate monitoring network. The experiment would be set up withknown boundary conditions based on prior characterization of the site. In addition togathering data from both existing and newly installed monitoring networks, theexperimental design might include subsurface sampling to verify or calibrate sensor data.
IFE facilities and sites should be selected and established with the understanding that
long-term (continuing a decade and longer) experiments will be conducted, as well as
shorter-term experiments. Long-term IFEs are essential for testing and validating bothprocess understanding and integrated site-wide models at multiple spatial and temporalscales. The facilities should be established and operated to provide opportunities for
iterative work. Once these experiments are started, unexpected results will occur forwhich more data or different kinds of data will be needed to test, refine, and validate
hypotheses, models, and the understanding derived from interim results.
An important aspect of IFE design should be a multidisciplinary approach. Researchscientists and technology developers (including technology users) from different
disciplines and work interests should participate in designing, installing, conducting, andanalyzing the results from an IFE. Establishing a number of sites for such tests would
contribute to an integrating environment for researchers and practitioners who too often
have worked in isolation.
Sites where long-term, integrated experiments can be conducted are essential forbringing together researchers from different disciplines in a team approach. In theprocess of designing and conducting IFEs, expertise from multiple disciplines is needed.
During each experiment, much will undoubtedly be learned about the physical, chemical,
and biological processes occurring in the subsurface. Thus, IFEs can be a real integrator,
moving researchers and practitioners toward the goal of thinking and working within an
integrated GHCB framework.

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To ensure that these larger purposes are achieved, operations at the IFE facilities mustbring together researchers and practitioners from across disciplines for the design,
conduct, and interpretation of the IFEs. The objective should be to create a crossdisciplinary “think-tank” environment. The long-term IFEs, in particular, should be set
up to force interdisciplinary teaming.
4.2.2

Facility Requirements for IFEs

To test models for predicting the field-scale fate and transport of contaminants in thevadose zone, facilities will be needed to conduct appropriate experiments andinvestigations. These same facilities may also be used to test and evaluate tools andtechniques for characterizing and monitoring contaminant behavior. The type ofexperiments needed to yield a better fundamental understanding of vadose zone processes
will depend on the phenomena being investigated. In some cases, smaller experiments
will suffice; however, larger experiments will likely be necessary to investigate vadosezone system behavior relevant to major contaminated sites. The larger experiments may
start with laboratory modeling, using a numerical laboratory as described below. The
advantage of this preliminary step is that it allows rigorous evaluation in controlled
conditions of conceptual models, sensor network design, and other critical experimental
parameters before proceeding to the field experiment. Therefore, the type of facilities
needed to support research outlined in this roadmap range from small bench-top
equipment to specialized laboratory facilities to instrumented, well-characterized fieldsites.
Currently, most universities and national laboratories have facilities for conducting
small-scale experiments. Relevant subsurface phenomena may be studied using thesefacilities under highly controlled conditions. However, it is unlikely that the research
results can be used to verify consequences of field-scale contaminant behavior. The
research conducted with these small-scale facilities will generally need to be coupledwith research conducted at a larger-scale before being applied in the field.
4.2.3

Relationship between Laboratory Capabilities and IFE sites

As noted in Section 3.4, computer-based synthetic test problems are one element in
an integrated approach to testing and validating models. A computer-based “numericlaboratory” can also provide an initial assessment for testing and optimizing the design ofa sensor network for initial site characterization or continuing monitoring. One or more
numerical laboratories equipped for simulating proposed IFEs would therefore
complement development of sites and facilities for the subsequent experiments in thefield. Ideally the numerical laboratory would allow for modeling of the sensor networkand placement strategy for the IFE, as well as providing synthetic test cases for themodels to be used, covering several scenarios relevant to the experimental context andhypothesis.
Specialized facilities are also needed in which to conduct large experiments (up to
2,000 cubic meters in size) relevant to the needs of major contamination sites, such as

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4.0 Necessary Supporting Capabilities and Infrastructuresome DOE and other national priority sites. An advantage of conducting large
experiments in specialized facilities is that they can be more controlled than field
experiments while allowing field-scale phenomena to be studied. Boundary conditions
can be controlled to investigate specific phenomena and to observe responses toenvironmental changes more quickly than can be observed in field experiments.
Properties can be engineered to reflect heterogeneous field conditions, which will allow
better interpretation of the experimental results because the properties will be known ingreater detail than for field experiments. Physical, chemical, and biologicalmeasurements will be easier to conduct because there will be greater access to theexperimental domain than in field experiments.
The large experiments can be designed to help distinguish between alternative fieldbased conceptual models of subsurface contaminant behavior, evaluate the long-term
performance of subsurface-engineered solutions, and conduct prototype and proof-ofprinciple testing before field application. Other important aspects of large experiments inspecialized facilities are that ‘real’ contaminants (e.g., chemical and radioactive hazards
and biopathogens), which could never be released in the field, can be studied undercontrolled conditions. The large-experiment facilities will be a resource for conducting
field-relevant, multidisciplinary experiments that will bring together the best technicalminds with state-of-science research tools.
4.2.4

An Approach for Initiating Development of IFE Support
Facilities

To begin development of IFE support facilities, representative field sites designatedfor such experiments must be established. They will be most useful if located in the mostrepresentative subsurface conditions where serious contamination problems are being
addressed. To take just DOE’s vadose zone contamination problems as an illustration, an
initial set of sites might include: (1) macroporous strata such as are found at the Hanford
Site; (2) fractured rock like that at Los Alamos, the Yucca Mountain Project, or parts of
the Nevada Test Site; and (3) sandy strata in climates with higher annual recharge, suchas the Savannah River Site. This set should be expanded or adjusted to cover
representative vadose zone conditions that are priorities for agricultural contamination(e.g., sites typical of hyper-salinization and of subsurface transport of agriculturalchemicals or pathogens), burial sites and firing ranges on military reservations, and othersubsurface conditions represented by sites on national priority lists. Obviously, the key
federal (and state) agencies involved, including the Departments of Agriculture, Defense,and Energy, as well as the Environmental Protection Agency, the U.S. Geological
Survey, and state environmental and public health entities, should work together to draw
up a short list of the best sites to meet the most pressing needs.
A key requirement for all the selected sites is that they remain stable and accessible
for several decades after the IFE facility is established. After a site has been designatedfor an IFE facility, there would be a call for a research coordinator to organize,
coordinate, and conduct the experiments at the facility. The experiment and the process
should be structured to bring together geologists, geochemists, hydrologists, biologists,and others in both the design and interpretation of experiments.
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Activity IFE1. Select, develop, and use national facilities for integrated field
experiments aimed at testing vadose zone research and technology.
•

Near-Term Task. Design and construct IFE support facilities at one or(preferably) more sites representative of priority vadose zone contamination
conditions.

•

Mid-Term Status Point. A first series of shorter-term experiments have been
completed.

•Long-Term Task. Conduct major, long-term integrated field experiments(designed to continue for a decade and longer).

Table 16 highlights major results that can be anticipated from this activity, given
sufficient support and programmatic direction to accomplish the detailed tasks andachieve the status points listed under it.
Table 16 Highlights of Results for Facilities for Integrated Field Experiments Infrastructure Activities
Near Term

Mid Term

Long Term

Facilities to support IFEs have been constructed at representative sites.
Results from the first series of short-term IFEs are available.
Results from major, long-term IFEs are supporting and testing long-term research
efforts, improving monitoring systems, and validating integrated assessment models.

4.3

Computational Resources to Develop Adequate Models andSimulation Capabilities

Models are most often thought of as predictive tools for making useful and costeffective estimates of future conditions or, sometimes, reconstructions of past events.
Models can be used to explore alternative design and operational decisions forcharacterization, monitoring, and remediation, as well as to compare and contrast policy
options such as remediation and long term stewardship.
Modeling is essential to understanding subsurface environments because theseenvironments are inherently complex, difficult to access, and therefore incompletely
understood. They exhibit a diverse set of important phenomena on a wide range of
temporal and spatial scales. They are heterogeneous and difficult to characterize andmonitor. For these reasons, models of vadose zone systems serve a much more
fundamental purpose than being a tool for prediction or reconstruction. They are used tosynthesize and integrate our understanding of basic processes, particularly the coupling
among processes across spatial and temporal scales. Models built for application at a
specific site may have more value in this synthesizing role than they do in making
predictions. The synthesis can be informal and ad hoc, or it can be based on formal
inversion algorithms and married to both characterization and monitoring data.

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Predictive and inversion models of vadose zone systems are based on numericalmethods. The resulting computer simulation models only have value if they are pertinent
to questions being asked by decision makers, accurately reflect the vadose zone systembeing modeled, and are obtained in a timely manner. The research identified anddiscussed in this section is aimed specifically at these numerical models and has beenorganized to address two important criteria for successful modeling: productivity andpredictability.
The usefulness of model results is directly related to the time it takes to build amodel, produce a computer simulation, run an inversion, or even display thevisualization. To improve the usefulness of models, one can ask, “What new
simulation/visualization tools are needed to improve user productivity?” That is, what dothe site investigator, the decision-maker, or the researcher need to make better use of theirtime and resources? These productivity questions are answered by research in threeareas: modern software; hardware; and mathematical algorithms, all designed specificallyfor vadose zone applications. These three areas are discussed in the remainder of thissection.
The second criterion for models addresses the question “What features andcapabilities must vadose zone modeling tools possess to both maximize and measurepredictability?” The answer to this question involves all of the GHCB processes
discussed earlier. Particularly important, and difficult, are challenges in how modelingtools treat coupled GHCB systems, scaling, and uncertainty. Research needs in theseareas are described in Section 3.1, as well as in the discussion of model integration andvalidation in Section 3.4. Improvements in software; hardware; and mathematicalalgorithms, discussed below, will also improve predictability, in part by allowing the
research results developed through Section 2 and 3 activities to be applied in integrated
vadose zone simulations.
4.3.1

The Problem Solving Environment: Integration of Data,
Knowledge, and Models and Generalization to Other Sites

There are a large number of possible conceptual and mathematical models applicableto vadose zone GHCB systems. The number of numerical approximation methods andvisualization tools is also large, and growing. This sign of maturity aside, modeling of
any complex subsurface system is a difficult task, which often leads to compromises inadequacy of the model or numerics used for a particular application. Further,
implementing a new model for a complex subsurface system can take months to years ofeffort, yet new models are needed routinely for sites where wastes have been buried orreleased to the ground by other means.
User interfaces for many modeling applications are crude and inflexible. Often,
several different computer programs must be inefficiently linked together. The data are
typically available only in diverse and incompatible formats. The effort required tointerpret results from one application to the next strains human and budgetary resources.
It also consumes time before the model can be run to produce useful output.
Consequently, corners are often cut, especially at the research level where most computer
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software is developed. These constraints have led to a large number of limited-use
computer programs, each of which is used—and improved—by only a small number ofpeople. In many cases, only the developer understands the strengths and limitations of amodeling tool well enough to use it efficiently and appropriately.
These problems can be resolved through the development of a friendly and usablevadose zone problem solving environment (PSE). In formal terms, a PSE is an integrated
software framework that provides the functionality needed for a complex set of tasks,
accessible through an efficient, high-level interface. Mathematica© and MATLAB© areexamples of commercially available PSEs. However, for a variety of reasons these andother commercial products are not suited to the task of building integrated system models
for vadose zone environments. A vadose zone PSE should unify mathematical, scientific,
and engineering concepts and constructs in a single framework. It should allow for rapid
set-up of problem specifications and easy manipulation and visualization of data.
The development of a PSE for modeling and visualizing subsurface systems, while
quite challenging, would significantly enhance productivity for those developing,
improving, or applying models, as well as those relying on model output for decision
support. It would encourage a greater number of hypotheses to be tested and decisionvariables to be quantified than is currently possible, inspiring greater confidence in themodel outputs and the decisions based on them. It could and should be integrated withrelated characterization and monitoring tools. (A number of these potential tools for
integration are listed in other roadmap activities).
The following two roadmap activities outline the work and time frame required to
implement a first-generation vadose zone PSE, as well as the R&D needed to extend andimprove it incrementally through subsequent software generations. Table 17 highlights
major results that can be anticipated from these activities, given sufficient support andprogrammatic direction to accomplish the detailed tasks and achieve the status points
listed under them.
Activity PSE1 (near-term). Develop and implement a useful first-generation vadosezone PSE.
•

Task with Near-Term Endpoint (subtask of PSE1). Develop the basic PSE
structure, including a high-level interface, data structure storage and retrieval
approach, simulation engine, and graphical back-end, with a common data
structure for modeling and characterization/monitoring.

•

Task with Near-Term Endpoint (subtask of PSE1). Implement a limited setof state-of-the-art numerical methods for the first-generation PSE.

•

Near-Term Status Point. A first-generation PSE is implemented, functional,
and in use. This version is likely to have the following characteristics: (1)restricted to structured grids, (2) implemented on workstations, (3)implemented for forward simulations, and (4) applicable on a limited basis to
the real-world problems of sites with vadose zone contamination.

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Activity PSE2. Extend and update the vadose zone PSE to provide an increasingly
powerful and integrated software framework for studying and solving
problems in vadose zone contamination.
•

Mid-Term Status Point. Location-specific databases of parameters havebeen built and populated.

•

Mid-Term Status Point. The PSE has matured to provide users with a wide
range of models, including some multi-scale, coupled models.

•

Mid-Term Status Point (also a status point for Activity CP2, in Section
3.1.2). Models for strongly coupled nonlinear GHCB systems are supported
in the vadose zone PSE.

•

Mid-Term Status Point (also a status point for Activity IV2 in Section 3.4).
A computational test bed to assist in testing and validating models has been
incorporated into the vadose zone PSE.

•

Mid-Term Status Point (also a status point for Activity IV2 in Section 3.4).
Support for inverse methods and for decision support simulations has been
added to the vadose zone PSE.

•

Mid-Term Status Point (also a status point for Activity IV2 in Section 3.4).
Geographical information systems have been linked with, or otherwisefunctionally incorporated into, the vadose zone PSE.

•

Mid-Term Status Point (related to a task and several status points for
Activity UC3 in Section 3.3). Support for uncertainty analyses has been
incorporated into the vadose zone PSE.

•

Mid-Term Status Point (also a crosscutting status point for numerics R&D
activities in Section 4.3.2). Support for a wide range of numerical methods
has been incorporated into the PSE.

•

Mid-Term Status Point. The vadose zone PSE has been implemented onstate-of-the-art supercomputing environments.

•

Mid-Term Status Point. The vadose zone PSE is being used routinely by
DOE and other agencies for visualization, analysis, and simulations in supportof characterization, monitoring, site assessment, and remediation/stewardshipdecisions at major sites of vadose zone contamination.

•

Long-Term Status Point (also a crosscutting status point for Activities CP1–
CP3 in Section 3.1). Realistic models for all coupled GHCB phenomena,
including strongly coupled nonlinear processes, that are important to vadosezone flow and transport are available in the PSE. These models cover allimportant time and space scales.

•

Long-Term Status Point. The vadose zone PSE supports state-of-the-art
numerics, including full spatial and temporal error estimation with automatic
grid refinement.

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Long-Term Status Point. Support for assessing the value of information has
been added to the vadose zone PSE, including the Shared Vadose Model(described in section 3.4).

•

Long-Term Status Point. The vadose zone PSE is broadly accepted andused as a valuable tool to assist all aspects of the development and applicationof the science: processes, characterization and monitoring, simulation, andprediction.

Table 17 Highlights of Results for The Problem Solving Environment Infrastructure Activities
Near Term

Mid Term

Long Term

We can access a shared PSE (software), which includes a common data structure foruse in characterization, monitoring, and modeling, as well as a limited set ofnumerical modeling tools.
An extended PSE, linked to a geographical information system, incorporates a rangeof numerical methods and provides a computational test bed for validating models.
The vadose zone PSE incorporates realistic models for all coupled GHCB
phenomena and state-of-the-art numerics; it supports ‘value of information’assessment for monitoring and characterization systems.

4.3.2

Advanced Numerical Algorithms

Although advances in computer hardware will aid the modeling effort, they cannot
provide all of the necessary improvements in light of issues like scaling and extreme
gradients. Furthermore, the usefulness of model results is directly related not only to thetime required to produce a simulation but also to the confidence that a decision-makercan place on the results. The simulation should be accurate, and it should provide somequantified indicators (metrics) for the likely range and probability of numerical error.
4.3.2.1

Adapting Advances in Numerics to Vadose Zone Modeling

Ongoing basic research on linear and nonlinear solvers, optimization techniques, grid
generation, parallel computing techniques, visualization, and other areas can have a large
impact on vadose zone simulation. However, these general advances in numericalalgorithms (numerics) must first be adapted to the particular needs and resources ofvadose zone simulation. In particular, existing state-of-the-art linear and nonlinear
solution techniques need to be adapted to vadose zone simulation, including thedevelopment of appropriate preconditioners and multilevel techniques. To capture
meaningful space and time scales of important GHCB phenomena, especially noncontinuum and chaotic phenomena, new and sophisticated multi-scale numerics are
required.
Activity NM1. Development and application of better linear and nonlinear solvers tovadose zone modeling.
•

Near-Term Status Point. Existing state-of-the-art linear and nonlinear
solvers have been adapted, improved, and applied to vadose zone problems.

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Mid-Term Status Point. Linear and nonlinear solvers have been improved tomatch vadose zone problems and run in computing environments, such as thevadose zone PSE.

Activity NM2. Improve approaches to resolve extreme spatial gradients in GHCB
properties and processes, such as fingers, sharp fronts, boundaries, andinterfaces.
•

Near-Term Status Point. State-of-the-art numerical methods are being
applied to modeling spatial gradients of fingers, sharp fronts, boundaries,
interfaces, and other extreme-gradient GHCB phenomena.

•

Mid-Term Status Point. New and improved numerical methods have beendeveloped and applied for resolving extreme GHCB gradients in both space
and time.

Activity NM3. Develop multi-scale mathematical methods and numerics to capture
meaningful scales of important GHCB phenomena.
•

Mid-Term Status Point. Multi-scale mathematical methods and numerics
are in use for modeling important GHCB processes, including most linearly
coupled, continuous processes.

•

Long-Term Status Point. More sophisticated multi-scale mathematicalmodeling and numerics have been developed, targeted to non-continuum andchaotic phenomena.

4.3.2.2

Error Estimation Numerics

Sources of numerical error in computer simulations have many origins. Simulating
evolving processes in spatially and temporally discrete increments is one widely
recognized source of numerical modeling error. Refining spatial grids and time steps can
reduce these errors. However, in heterogeneous systems like those typical in the vadosezone, refinement is needed only in certain regions of space and/or time. To savecomputational effort, the computation should automatically and adaptively refine its grid
and/or time steps locally, as necessary to maintain accuracy. For the same reason, it
should, if possible, adjust the amount of source detail required.
Time truncation error is particularly difficult to estimate and control. It accumulates
from one time step to another, and is often self re-enforcing (i.e., it exhibits positive
feedback). However, there are limits to refinement, even aside from computational
resource issues. As refinement increases, so does rounding error and ill conditioning of
the system.
Certain types of algorithms contribute other numerical artifacts, such as numericalinstability, nonconservation of mass, violation of the maximum principle (i.e., creation ofnonphysical local maxima or minima in the solution), numerical dispersion, and initiation
or non-initiation of physically relevant frontal instabilities. Such errors are often notameliorated by refined grids and reduced time step intervals because the mathematical

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structure itself is improperly approximated. Of particular interest is the ability to resolvefeatures such as extreme spatial and temporal gradients without producing numericaloscillations. These issues must be investigated and resolved within the context of vadosezone applications.
Activity NM4. Develop and apply spatial numerical error estimators and adaptive
local (spatial) grid refinement algorithms.
•

Near-Term Status Point. Numerical errors are being estimated in terms ofquantities of interest to decision-makers, using spatial numerical error
estimators and adaptive, spatially local, algorithms for grid refinement.

Activity NM5. Develop and apply spatial and temporal error estimators and adaptive
local grid and time step refinement algorithms for nonreactive systems.
•

Mid-Term Status Point. Both spatial and temporal error estimators and gridrefinement algorithms (for spatial grid and time steps) are being incorporated
in nonreactive flow-and-transport models.

•Long-Term Status Point. Spatial and temporal error estimators and adaptive
local grid and time step refinement have been developed and are being applied
for reactive systems in the vadose zone.

4.3.2.3

Warning or Protecting Users from Modeling Errors and Constraints

Beyond improving numerics to reduce modeling error, algorithms are needed that
automatically alert the user to a model’s possible numerical limitations throughquantified error range estimates. An even more significant development would be
algorithms that self-adaptively select a more accurate alternative approach. Numericalerror estimates should also be expressed in measures of interest to decision makers.
For example, estimation of decision variables (mathematically referred to as
functionals of the solution) and their variance is more meaningful than merely trying toestimate the norm of the global error. A functional can be overly sensitive to small errors
in the solution or data at some point in time and/or space, even though the global error
appears to be quite small. Conversely, the functional may be insensitive to such errors,
therefore reducing computational effort. Useful algorithms must not only estimate themean and variance of quantities of interest to a decision maker, but also provide
information on the likely error in those quantities generated from a variety of sources,
including numerical resolution, inadequate or inappropriate numerics, scaling, and noisy
data. These numerical algorithms should be used together with algorithms tracing
uncertainty due to the conceptual model, uncertain and variable parameters, initialconditions, and boundary conditions.
The envisioned algorithms must be ported to the vadose zone PSE, discussed in
Section 4.3.1, or their enormous complexity would limit their utility to practitioners andregulators who are not well versed in numerical techniques and computational issues.

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Activity NM6. Determine criteria for acceptable computational errors based onmodel uncertainties and incorporate algorithms for these criteria in vadosezone simulation software.
•

Mid-Term Status Point. Probabilistic approaches to estimate likely
numerical error are available for use in vadose zone system modeling, insteadof maximum error. These probability approaches are being used to estimate
mean and variance, as well as other numerical error measures, in terms ofquantities of interest to decision makers.

•

Long-Term Status Point. Estimates of maximum, mean, variance, and othernumerical error measures in quantities of interest to decision makers are
standard practice in modeling vadose zone systems. Modelers use theseestimates adaptively to improve simulation results.

The following status points apply to all of Activities NM1 through NM6. Table 18
highlights major results that can be anticipated from these activities, given sufficient
support and programmatic direction to accomplish the detailed tasks and achieve thestatus points listed under them.
Mid-Term Status Point (applies to Activities NM1–NM6; also a status point for thevadose zone PSE in Section 4.3.1). Support for a wide range of numericalmethods has been incorporated in the vadose zone PSE.
Long-Term Status Point (applies to Activities NM1–NM6). In models of vadosezone systems, the numerical methods are selected automatically and on an
appropriate scale, during computation, to reduce numerical error in decisionvariables.
Table 18 Highlights of Results for Advanced Numerical Algorithms Infrastructure Activities
Near Term

Mid Term

Long Term

Existing state-of-the-art numerical methods have been adapted to address vadosezone problems.
A wide range of numerical methods relevant to vadose zone problems are available.
Site assessment models can automatically select the best numerical method at a
spatial and temporal scale to minimize numerical error in decision variables.

4.3.3

Computing Power: A Dedicated, High-Powered Capability

Sheer numerical speed addresses both productivity and predictability. Vadose zone
simulations must resolve extreme spatial and temporal gradients, capture multi-scale
coupled processes, and handle large data sets. Uncertainty analyses dramatically increase
the load on computational resources.
Today, almost everything is done on fast desktop machines or networked high-end
workstations. Nevertheless, the computing and storage memory capacities of these
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systems, as well as their processor, bus, and network speeds, limit their capacity torepresent vadose zone processes realistically, synthesize data, compute forward
predictions, or visualize information. Occasionally simulations are run on teraflop
machines (processors capable of performing a trillion basic arithmetic operations per
second), such as the Accelerated Strategic Computing Initiative’s (ASCI) Blue and White
Machines. But access is limited due to competing high-priority uses and tight security
precautions. In short, the present generation of hardware available to the vadose zone
R&D community is inadequate.
The vadose zone community needs priority access to state-of-the-art massively
parallel computers, like the ASCI’s teraflop machines. The vadose zone community
would use these machines for research into multi-scale processes and process coupling,
for characterization, for modeling and prediction, and for visualization. The machines
could be housed at one or more national laboratories. Priority use could be given to
researchers from universities and the national laboratories who are working on a range ofenvironmental science and technology issues, not just the vadose zone.
Such a facility would require a dedicated computer support staff to help
environmental scientists and engineers prepare their computer programs for parallel
processing and port them to the massively parallel computer. This staff could also unite
these new computation resources with the proposed vadose zone PSE. The support staff
could be patterned after the staff that runs the ASCI Blue and White machines, at theCenter for Applied Scientific Computing at Lawrence Livermore National Laboratory.
Activity HPC1. Design, implement, and continue to improve an Environmental
Science High-Power Computing capability.
•

Task with Near-Term Endpoint. Build a user community; form anorganizing committee.

•

Task with Near-Term Endpoint. Write the proposal for a multi-teraflop(1013 to 1014 Flops) computing capability, to be associated with the DOE
Environmental Management Program and/or the Office of Science.

•

Near-Term Status Point. Proposal for a multi-teraflop computing capability
has been submitted to DOE.

•

Near-Term Status Point. Design of the computing capability has been
completed, including its expected future growth in size and capability.

•

Task Beginning after Above Status Points, Completed in Mid-Term.
Purchase and install the computing capability at a national laboratory; hirestaff.

•

Mid-Term Status Point. A high-power computing capability is in use by alarge variety of vadose zone researchers on studies of processes,
characterization/monitoring, and modeling. It is used to study both laboratory
and field experiments. It is also being used in applied studies forenvironmental management sites by DOE and other “problem holders.”

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Task beginning in Mid-Term with Mid-Term Endpoint. Form acommittee and write a proposal for the next generation of computing
capability.

•

Mid-Term to Long-Term Status Points. The next-generation computing
capability is designed, purchased, and installed.

•

Long-Term Status Point. A next-generation high-power computing
capability is in common use for addressing vadose zone problems.

Activity HPC2. Build (or transfer from ASCI and others) infrastructure such as
desktop visualization, archival storage, and parallel input/output interfaces.
Activity HPC3. Train the user community for the environmental science high-power
computing capability.
Activity HPC4. Port the vadose zone PSE to run on the environmental science highpower computing capability.
Table 19 highlights major results that can be anticipated from these infrastructuredevelopment activities, given sufficient support and programmatic direction toaccomplish the detailed tasks and achieve the status points listed under them.
Table 19 Highlights of Results from High-Powered Computing Infrastructure Activities
Near Term

A proposal is submitted to DOE and acquisition of the EHPCC begins.
First generation EHPCC is in use.
Second generation EHPCC is in use.

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Long Term

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5.0

CONCLUSIONS AND RECOMMENDATIONS

The technical content of the Vadose Zone Science and Technology Roadmap consistsof the activities presented in Sections 2 through 4. (Appendix B shows all the roadmap
activities, with their associated tasks and status points.) This section provides concludingreflections on these activities when viewed as a whole. It also contains suggestions fromthe Roadmap Executive Committee on how best to understand, prepare for, and sustain
the activities as a roadmap for addressing issues of national importance. The Committee
has provided additional suggestions on a path forward for following, expanding, andupdating the roadmap in a separate document, Letter Report of the Vadose Zone S&T
Roadmap Executive Committee on Creation of a National Multi-agency Vadose Zone
Science and Technology Initiative.
5.1

The Bottom Line: Highlights of Expected Results from Roadmap
Activities

Table 20 presents the results that have been highlighted at the close of previous
sections as useful outcomes of the roadmap activities. These highlights have been
selected (and worded) to convey to a broader, nontechnical audience how the public andthe nation will benefit from investing in vadose zone research (i.e., the bottom line).
Readers with an interest in technical detail and context should consult the activities andthe accompanying narrative in Sections 2 through 4.
The highlighted results are keyed to the same time horizons used for the roadmap
activities. Near-term means roughly within 4 years of beginning roadmap
implementation. Mid-term means the results can be expected within a decade or so. Longterm applies to results over several decades (roughly, a 25-year horizon). These time
horizons, as noted earlier, depend on sufficient resources and programmatic direction
being applied, at the right time and place, to accomplish the tasks and reach the status
points detailed in the roadmap. Table 20 provides a convenient way to survey the resultsby time horizon, to consider what can be achieved quickly, what will take more than a
few years, and what will require sustained effort over several decades.

Table 20 Highlights of Expected Results from Roadmap Activities
Near Term M id Term Long Term

#1 Physical Description of Flow & Transport
Computer models used by federal agencies and others incorporate the best state-ofthe-art conceptual models and implementations (software modules).
We can detect the presence of fluid in fractures in some cases.
We can distinguish, in most cases, the subset of fractures that are conduits for fluid
flow and contaminant transport.
We can map and predict water distribution and flow through structured soils or
fractured rock at multiple spatial scales.
Monitoring data on fluid flow and contaminant transport can be interpreted andrepresented visually at site-wide scales in real-time.

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Table 20 Highlights of Expected Results from Roadmap Activities (cont.)
Near Term M id Term Long Term

#2 Che mical Properties & Processes
Reaction kinetics and rate laws (in solution) have been formulated for priority vadosezone conditions.
Individual chemical contaminants in the vadose zone can be detected.
We understand the kinetics for important chemical reactions at solid and liquidinterfaces (e.g., ion exchange and colloids) in vadose zone conditions.
Flow and transport models map and predict important vadose zone chemicalinteractions, including those involving mixtures of solids, liquids, and air.

#3 Biological Properties & Processes
We understand and can predict how microbial processes affect or are a ffected bybioavailability of important contaminants.
We can measure biochemical rates, in situ bioavailability, and the composition andactivity of microbiological communities.
Reactive transport models can predict how microorganisms will interact withcontaminants.
Inexpensive systems are available to measure community composition and activity.
We can accurately predict site-specific biodegradation rates for important
contaminants.
We can take biological measurements along with others without destroying thesamples.

#4 Colloidal Formation & Transport
We know how to detect mobile colloids and how to sample and analyze them.
Important colloid-contaminant interactions understood at micro and macro levels.
Flow and transport models can map and predict important colloidal interactions andtransport.

#5 Multiphase Flow & Transport
We can model processes with unstable or preferential flow of aqueous and nonaqueous phases.
We can detect and interpret multiphase flow and transport of complex contaminant
mixtures at contaminated sites.
Site assessment models incorporate multiphase flow and transport.

#6 Unstable Processes
We can identify the onset of chaotic and unstable processes.
We can determine whether and when chaotic conditions are important at a site.
Site assessment models incorporate models for chaotic and unstable flow.

#7 Understanding and Modeling Coupled Systems
The highest priority coupled GHCB processes have been identified.
We understand the strengths and weaknesses of existing models.
Some of the important strongly coupled phenomena can be modeled.
Process models for important strongly coupled phenomena have been validated andfield-tested across spatial and temporal scales.
Site assessment models incorporate all important coupled GHCB phenomena
realistically.

#8 Combining Processes & Data at Different Scales
We can si mulate scaling problems of important GHCB phenomena using
probabilistic modeling.
We can measure and model coupled GHCB phenomena across spatial scales.
Site models incorporate strongly transient and coupled GHCB phenomena for
multiple time periods.
Site models incorporate scaling with estimates of uncertainty, and the models canpropagate uncertainty estimates across spatial and temporal scales.

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Table 20 Highlights of Expected Results from Roadmap Activities (cont.)
Near Term M id Term Long Term

#9 Estimation & Reduction of Uncertainty
We have identified and understand the sources of uncertainty for monitoring andmodeling vadose zone sites.
We have assessed and catalogued the state-of-the-art methods for estimating andreducing uncertainty.
We have developed and tested new probabilistic approaches for estimating andreducing uncertainty.
We can optimize characterization and monitoring systems to reduce uncertainty, andwe can predict the value of additional data for reducing uncertainty.
Site assessment models incorporate techniques for estimating and reducing
uncertainty in making decisions on site cleanup and stewardship.

#10 Improving Monitoring Systems
Several conceptual models for fate and transport (beginning a catalogue) have beenvalidated with field data representing an emerging set of standard monitoring
approaches.
Researchers, site operators, regulators and stakeholders can access a catalogue of
proven fate and transport models with data sets for priority vadose zone cleanup sites.
Real-time monitoring systems at sites with vadose zone contamination provide early
warning of contaminant discharge or movement.
The model catalogue has been condensed and updated, and monitoring approaches
have been standardized.

#11 Integrating and Validating Site-Wide Models
We can compare modeling techniques using a standard set of synthetic test problems.
We have models for sa mpling events and instrument response to improve
instrumentation and network design for characterization and modeling.
We can test and validate models and measurement methods in laboratory and field
experiments following standard protocols.
Site-wide assessment models are credible to both scientific and public policy
communities.

#12 GHCB Data Library and Model Set
A virtual library of qualified GHCB data for priority contaminated sites is available
to researchers, site operators, regulators, and the policy communities.
Virtual library data can be run on prototype models that incorporate a GHCB
framework.
We can si mulate critical features of priority contaminated vadose zone sites using
GHCB models and virtual library data.

#13 Sensors, Instrumentation & Emplacement
Prototypes of miniaturized sensors are small enough to fit a package of 10 inside a
two-inch hole.
We can characterize the geology and hydrology of a site at a 10-meter scale with one
month turn-around.
Techniques to minimize emplacement effects have been developed and tested.
Minimally invasive emplacement methods and miniature sensors are available asalternatives to conventional boreholes and instrumentation techniques.
We can characterize the geology and hydrology of a site at 1-meter scale with a one
day turn-around.
Injectable, smart sensors are available off the shelf; non-invasive methods formeasuring key flow and transport properties are available.
We can characterize the geology and hydrology of a site at 1-meter scale in real-time
for most sites.

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Table 20 Highlights of Expected Results from Roadmap Activities (cont.)
Near Term Mid Term Long Term

#14 Design & Optimization of Measurement Networks
We can access a numerical laboratory linked with instrumented field sites to conduct
experiments on characterization/monitoring network design and data value.
We can use field data in a numerical laboratory to optimize monitoring networks forfield-scale experiments.
We can use network optimization design methods to explain cost-benefit risks andother trade-offs to end users, as part of planning for long-term monitoring and site
assessment activities.
We can quickly determine the location sensitivity and data value for designs ofmonitoring and characterization networks.

#15 Facilities for Integrated Field Experiments
Facilities to support IFEs have been constructed at representative sites.
Results from the first series of short-term IFEs are available.
Results from major, long-term IFEs are supporting and testing long-term research
efforts, improving monitoring systems, and validating integrated assessment models.

#16 The Problem Solving Environment
We can access a shared PSE (software), which includes a common data structure foruse in characterization, monitoring, and modeling, as well as a limited set ofnumerical modeling tools.
An extended PSE, linked to a geographical information system, incorporates a rangeof numerical methods and provides a computational test bed for validating models.
The vadose zone PSE incorporates realistic models for all coupled GHCB
phenomena and state-of-the-art numerics; it supports ‘value of information’assessment for monitoring and characterization systems.

#17 Advanced Numerical Algorithms
Existing state-of-the-art numerical methods have been adapted to address vadosezone problems.
A wide range of numerical methods relevant to vadose zone problems are available.
Site assessment models can automatically select the best numerical method at a
spatial and temporal scale to minimize numerical error in decision variables.

#18 High-Powered Computing
A proposal is submitted to DOE and acquisition of the EHPCC begins.
First generation EHPCC is in use.
Second generation EHPCC is in use.

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5.1.1

Near-Term Outcomes: Moving Knowledge into PracticeMany of the near-term results in Table 20 share a common theme: moving the state of
the art to the state of practice. This means getting the current knowledge and capabilities
already existing in the research communities into operational use—for example, indeveloping monitoring strategies—at the nation’s priority sites of vadose zone
contamination. Some of the near-term results highlighted in Table 20 make this point
explicitly, such as near-term results for Physical Description of Flow and Transport, the
GHCB virtual library, or Estimating and Reducing Uncertainty:•

Computer models used by federal agencies and others incorporate the best stateof-the-art conceptual models and implementations (software models). (For details,
see Activity PH5 in Section 2.2.1.)•

A virtual library of qualified GHCB data for priority contaminated sites isavailable to researchers, site operators, regulators, and the policy communities.
(See Activity G1 in Section 4.1.1.)•

We have assessed and catalogued the state-of-the-art methods for estimating andreducing uncertainty. (See Activities UC1 and UC2 in Section 3.3 for details.)

In addition, many other near-term results contribute implicitly to this major outcome. For
example, the near-term results for Chemical Properties and Processes include extending
existing models for reactions in solution to the higher temperatures and ionic strengths
often found in vadose zone environments (see Activity CH1 in Section 2.3.1.1). The
near-term task for the model integration and validation Activity IV2 (Section 3.5) is todefine synthetic test problems for comparing existing techniques of inverse modeling andmodel validation. In the activities to develop infrastructure and capabilities, the firstnear-term status point for Activity SIE1 is to demonstrate known techniques for sensor
emplacement that could minimize effects on the vadose zone system, such as
microdrilling and the use of coiled tubing (Section 4.1.2).
Moving state-of-the-art techniques and understanding into practice quickly has atleast two significant benefits, one obvious and another less so. The obvious benefit isthat these tasks “pick the low-hanging fruit,” providing quick returns because much of theresearch investment has already been made. The less obvious benefit is that concerted
effort to get new knowledge and technical capability into practice will bring researchersand solution-oriented problem owners into continuing and close interaction.
5.1.2

Mid-Term Outcomes: Improvements in Site Monitoring

For the mid-term, the roadmap outcomes of greatest significance are likely to be thecumulative advances in monitoring systems for vadose zone sites. The mid-term resultsin Table 20 that represent these advances explicitly include those for Improving
Monitoring Systems; Sensors, Instrumentation, and Emplacement; and Design and
Optimization of Measurement Networks:

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Real-time monitoring systems at sites with vadose zone contamination provide
early warning of contaminant discharge or movement. (See Activities MON1 andMON3 in Section 3.4.2.)•

Minimally invasive emplacement methods and miniature sensors are available asalternatives to conventional boreholes and instrumentation techniques. We cancharacterize the geology and hydrology of a site at 1-meter scale with a one day
turn-around. (See Section 4.1.2)•

We can use field data in a numerical laboratory to optimize monitoring networks
for field-scale experiments. (See Section 4.1.3.)

Many near-term results and other mid-term results will contribute implicitly to advances
in vadose zone monitoring capabilities. Improvements in both process understanding(quantified and tested through process modeling) and measurement capabilities willcontribute to better monitoring systems. For example, the near-term and mid-term results
highlighted in Table 20 for Biological Processes and Properties will improve monitoringof natural attenuation and in situ engineered bioremediation. The near-term and midterm results for Multiphase Flow and Transport and Unstable Processes will aid indesigning effective vadose zone monitoring systems and interpreting the data collectedfrom them. Advances in scaling and early results from integrated field experiments areother examples of important contributions to improved monitoring capabilities.
A sound and efficient monitoring program is critical at major sites during
environmental cleanup and afterward, throughout any period of stewardship required byresidual contamination on site. The state of practice, enshrined in federal and most state
environmental regulations, has been to monitor the groundwater at and around the site,rather than monitoring the vadose zone.15 Where contaminants lie very close to theannual high water table, or for contaminants that move rapidly through whatever vadosezone separates the source term from groundwater, there may be no alternative. However,for many sites of serious subsurface contamination across the nation, waiting untilcontaminants appear in the groundwater means that a major part of the battle has beenlost. If remediation can remove or isolate source terms and halt plumes while they arestill in the vadose zone, the effectiveness of the remediation is often greatly enhanced,
and the cost significantly reduced, compared with groundwater remediation alternatives.
(See accompanying box on Dynamic Underground Stripping versus pumping and treating
groundwater.)
5.1.3

Long-Term Outcomes: Accepted, Credible Support for
Decisions on Environmental Cleanup and Stewardship

Many of the long-term results highlighted in Table 20 provide better tools forsupporting site-wide assessments and decisions on environmental cleanup andstewardship. In truth, the Committee expects models and data gathering to improve year
15

The state of federal regulation and regulatory practice with respect to vadose zone monitoring is
discussed by Lorne Everett in the First Foreword in Vadose Zone Science and Technology Solutions(Looney and Falta, 2000, p. xix)

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Stopping Contaminants in the Vadose Zone Versus Groundwater Remediation
Beginning in the 1980s, DOE-sponsored research at Lawrence Livermore National Laboratory (LLNL) developed
and patented processes for removing or pyrolyzing subsurface petroleum and chlorinated hydrocarbons. This
technology, called Dynamic Underground Stripping (DUS) and Hydrous Pyrolysis Oxidation (HPO), uses a control
technology, cross-borehole electrical resistance tomography, to monitor the progress of the extraction and manage
the steam front in the subsurface. DUS/HPO was demonstrated in 1994 on a deep gasoline spill at LLNL. In 1997
it was implemented as an alternative to conventional pump-and-treat of groundwater at a utility pole creosoting
yard in Visalia, California (the Visalia Pole Yard). The table below compares this vadose zone remediation
alternative with pumping and treating groundwater. In addition, pump-and-treat remediates only the groundwater,whereas DUS/HPO remediates contamination in both the vadose zone and the groundwater.
Project Parameter
LLNL Gasoline Spill
Visalia Pole Yard
Total project cost ($ millions, through 2000)$11$21
Unit cost per cubic yard of soil treated
Actual cost
$65
$57
Predicted repeat cost (w/ lessons learned)
NA$38
Costs without research component$35
NA
Comparative cost per gallon of creosote removed
Pump and treat groundwaterNA$26,000
DUS/HPO vadose zone remediation
NA$130
Time to remove 7,600 gallons of gasoline (LLNL)
or 1.3 million pounds of creosote (Visalia)
Pump and treat groundwater
2,000 years
3,250 years
DUS/HPO vadose zone remediation
1 year (estim.)a
3 years
NA = data not available or not applicablea
The LLNL demonstration operated for only 15 weeks. The estimate is based on yields obtained during thedemonstration.
Source: Everett, 2001.

by year even in the near and mid-term. However, after a decade or so of pursuing theroadmap’s activities, the Committee anticipates a qualitative leap forward. We will thenbe able to visualize, quickly and accurately, the current state of site-wide (and larger)
vadose zone systems. We will be able to simulate their behavior under multiple
alternative future scenarios, reaching to the long time horizons required to support majorcleanup and stewardship decisions. These projections, which will carry levels ofcertainty and sensitivity unattainable at present, should suffice to win the confidence ofregulators and the public.
Results from many parts of the roadmap will contribute to this major pay-off. The
ultimate goal is captured in the long-term result for Integrating and Validating Site-WideModels:•Site-wide assessment models are credible to both scientific and public policy
communities.

Among the technical capabilities that site-wide assessment models will have toincorporate to attain this credibility are those noted in the long-term status points, as well
as mid-term tasks and status points. Additional relevant capabilities are expressed in thelong-term results highlighted in Table 20 for categories 1 through 9, 12, and 15 through18. Even a glance through these for Activities IV1 through IV4 (Section 3.5), theRevision 0.0

945.0 Conclusion and Recommendations

highlighted summary results, show that a great deal of work must be undertaken andcompleted successfully to reach the ultimate goal.
5.2

Linkages Among Research and Infrastructure Activities

The activity structure used in Sections 2 through 4 establishes connections among thetasks and status points under an activity. However, the connections across the activities,
particularly those between research areas and infrastructure development, are only
partially represented, for instance by cross-cutting status points for the most important
linkages. A great many more interdependencies among these efforts can be identified,even at this planning phase. More will arise unexpectedly as work is done, provided
there is ample communication across disciplines and specific applications.
Linkages that are important for roadmapping include prerequisites, influencers, andsynergies. An effort x has a prerequisite y if x cannot occur (or is not expected to occur)
unless y also occurs. An effort x influences y if progress in x affects progress in y, but ycould occur without x. Two efforts are synergistic if progress in either is likely to occur
more quickly, or advance further, if the other progresses. Prerequisites are important for
S&T planning because they shape the critical path to important outcomes. Synergies andinfluences are important as opportunities for communication and cooperation that can
produce desired outcomes more quickly and efficiently.
Many of the crosscutting status points for the roadmap activities represent
developments that have prerequisites in the activities they connect. For example, the twocross-cutting long-term status points for Activities PH10 and PH11 (see end of Section
2.2.3) will not occur unless there is progress in both defining the relationships by which
geophysical attributes can be translated into flow and transport parameters (Activity 10)
and applying improved geophysical measurement technologies at typical sites of vadosezone contamination (Activity 11).
In other instances, the cross-cutting status points reflect synergies rather than strict
prerequisites. The two cross-cutting long-term status points for coupling basic properties
and processes (Section 3.1) are more likely to be achieved with success in all three of the
CP activities (better databases for processes with GHCB properties, cross-disciplinarymodeling approaches, and realistic models for strongly coupled nonlinear phenomena).
In addition, progress in Activity CP3 (realistic models for strongly coupled nonlinear
phenomena) is almost certainly a prerequisite for both of these status points.
As the Executive Committee worked on refining the structure of this initial roadmap,
a particularly critical set of linkages emerged between the research activities in Sections 2
and 3 and the infrastructure activities in Section 4. As noted in the introduction to
Section 4, early progress on a number of the infrastructure activities depends on nearterm research efforts to move the state of the art into practice. If these dependencies are
not strict prerequisites, they are at least very strong influences on the rate and extent of
infrastructure development for a given level of resource investment. Examples include
assembling the GHCB virtual library, developing the first release of the vadose zone

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PSE, and setting up the site instrumentation, numerical laboratory support, and otherfacilities for one or more IFE sites.
Once these infrastructure capabilities are operational, even as “first generation”
implementations, they will exert strong accelerating influences on the mid-term and longterm progress in most of the research activities in Sections 2 and 3, including those on
which they initially depended. Looking at the research activities and the infrastructuredevelopment activities as program elements, there are strong synergies between them.
The opportunity this represents argues for programming investments in both areas withan eye to achieving the greatest boost from their synergies.
A wall chart of the highlighted results in Table 20, which captures important linkages
at the level of major results for the three time horizons, is available from INEEL. In
subsequent refinements and updates of this roadmap, it would be useful to trace anddocument these dependencies, particularly the prerequisites and strong synergies for key
outcomes, at a more detailed level. Specific tasks or status points that have prerequisites
or strong synergies need to be identified. The key outcomes should be those thatparticipants agree are most important to the goal of protecting groundwater resourcesfrom vadose zone contamination.
5.3

Vadose Zone Research in the Context of Environmental Cleanup and
Stewardship Imperatives

This roadmap covers only a part of the effort needed for environmental cleanup andstewardship of the nation’s vadose zone contamination problems. It does not cover the
S&T for remediation and isolation techniques or other modes of action for exercisingstewardship in the broadest sense. Nor does it include the S&T to support assessment of
impacts on human health, the environment, and the local, regional, or national
economy.16 Beyond even the S&T components, there are many other factors in the
conduct of cleanup and stewardship operations. Regulatory requirements, the concerns
and interests of affected communities and other stakeholders, legacy contracts andoperations, and competing uses of scarce resources are among the factors that form thisbroader context.
An analysis of linkages in terms of prerequisites, influences, and synergies can beapplied here, as well as to the roadmap activities. Results of activities outlined in thisroadmap will affect the S&T activities for contaminant removal, immobilization, or othercleanup operations, as well as choices among active cleanup and natural or engineered
attenuation. Progress in the S&T for those activities will in turn influence the workneeded in site visualization and monitoring systems, sensor and measurement techniques,
and even the required degree of understanding of various vadose zone processes. More
broadly, achieving near-term results such as those highlighted in Table 20 will influence
16

Although these other aspects of the total environmental cleanup and stewardship effort are notspecifically included in this roadmap, moving predictive tools described here from the state of the art tostate of practice and implementing the infrastructure and capabilities will support these wider activities.

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the support from stakeholders and government budgeting authorities for further efforts tounderstand, monitor, and control contaminants in the vadose zone. In this light, it isimportant for the roadmap presented here to be integrated with the larger context of S&T
planning for cleanup and stewardship. Efforts in planning for the larger context will
require refining and updating this roadmap.
One significant element of the larger context that affects this roadmap is the sense ofurgency, conveyed in regulations as well as in political and social drivers, to clean up
environmental contamination quickly before more damage is done. In meetings withregulators, other stakeholders, and site cleanup operators, a plan like this for “moreresearch,” particularly for long-term research, often raises concerns that doing more
research will divert resources and attention from cleanup. If cleanup plans are alreadyformulated, agreed upon, and prescribed by regulatory authorities, why is long-term
research needed? For DOE’s cleanup sites, this issue is sharpened by site-specifictimetables, often formalized as regulatory requirements, to “clean up and close” DOE
operations on most or all of a site by a specified date. “Closure” in this sense implies anend (or major downsizing) to expensive tax-supported operations and a return of all ormost of the site to other uses.
Whenever the resources needed for a range of potential activities are limited, there ispotential for competition among those activities. In that sense, any activity in thisroadmap may “compete” for resources with another roadmap activity. And a program topursue the roadmap systematically can be viewed as competing with any other national
program, from defense to health care to debt reduction, as well as programs forenvironmental remediation. However, to focus on just the potential for resourcecompetition is to ignore the considerable potential for constructive influences andsynergies, which a systematic approach to resource allocation can tap. A well-planned
program for research and development to improve cleanup and stewardship options can,and should, be a profitable return on investment for the nation. The reason for
performing this roadmapping activity was to improve and extend just such a planning
process, continuing forward from preceding and concurrent efforts at DOE andelsewhere.
Recent research on alternative landfill covers to meet requirements of the Resource
Recovery and Conservation Act (RCRA) illustrates the investment potential of research.
(See accompanying text box.) This example also points out some of the fallacies in a
simplistic view of “finishing” cleanup operations. At many national priority sites, theplanned cleanup operations will leave residual wastes in the subsurface, often in the formof waste burial grounds, landfills, or other relatively concentrated “waste inventories.” Inmany instances, a land cover similar to those tested in this research will be used tominimize the flow of contaminant-transporting water through the zone of buried waste.
In the land cover study, the installation cost of the successful alternative (theevapotranspiration cover) was half that of the prescribed approach with equivalent
performance (the RCRA Subtitle C cover). A simpler and less expensive prescribed
approach (approved for sanitary landfills) failed in the climatic and soil conditions of thetest. More important, though, the estimated operating and maintenance cost for the
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Alternative Land Cover Research as a Stewardship Investment
Sandia National Laboratories tested the performance of six alternative approaches to an engineered
landfill cover in an arid to semi-arid environment typical of the western U.S. The five-year project was
funded by the EPA, the DOE Subsurface Contaminants Focus Area, and the DOE Characterization,
Monitoring and Sensors Technology Crosscut Program. Two of the designs were those prescribed in
RCRA Subtitle C (RCRA C cover) and RCRA Subtitle D (RCRA D cover). Of the four experimental
designs tests, the anisotropic barrier cover and the evapotranspiration soil cover had flux rates and barrier
efficiencies similar to that of the RCRA C cover. The anisotropic barrier incorporates soil layers thatfacilitate the lateral movement of water through drainage layers within the barrier. The evapotranspiration
cover uses soil mixtures and compaction to hold moisture near the surface, where a mix of surface
vegetation recycles nearly all of it to the atmosphere by evaporation and transpiration. Based on the
results summarized below, the evapotranspiration design was selected for installation over a mixed waste
landfill at Sandia National Laboratories.
Cover Design
Flux rate (mm/year)
Barrier efficiency
Construction cost ($/m2)
Landfill Application ($million)
Total capital cost
Operation & maint., 30 yr.
Source: DOE, 2000

RCRA D
4.82
99.986%$51.40RCRA C
0.13
99.999%$157.54

anisotropic
0.16
99.999%$75.26

evapotranspiration
0.19
99.999%$73.89not reported
not reported$3.55$12.36

not reported
not reported

1.76
$2.07

alternative for 30 years “after closure” is one-sixth of the equivalent cost for the RCRA
Subtitle C cover. The primary cost for operation and maintenance is for long-termmonitoring to ensure the cover does not fail. Whereas the prescribed approaches require
groundwater monitoring wells and laboratory analysis of collected samples, thealternative employs embedded fiber-optic moisture sensors that do not require laboratory
analysis.
The alternative barrier designs in this research all are based on principles for limiting
percolation of infiltrating moisture through the layers of soil or sand. They thus depend
on understanding vadose zone flow and transport processes. The alternative monitoring
approach reflects advances in measurement methods, including sensor instrumentation,
applicable to monitoring in the vadose zone. If the cost savings for the alternative ,compared with the RCRA Subtitle C cover, are multiplied by just the number of DOE
and other hazardous waste landfills in similar environments, the “return on investment”
for this research is huge. These savings do not even reflect avoiding the additional costsof cleaning up or isolating contaminated groundwater if RCRA Subtitle D covers were to
be used on sanitary landfills in environments where they quickly fail.
5.4

Interagency and Intergovernmental Coordination is Critical

This roadmapping project began with an emphasis on vadose zone S&T needs forcleanup and stewardship at the DOE sites, particularly those where vadose zone
contamination would remain a stewardship issue for decades. The initial objective was tocreate a DOE complex-wide roadmap first, and then consider the extent of its
applicability to other situations, including vadose zone contamination issues being

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addressed by other federal agencies (e.g., Department of Agriculture, DOD, EPA, and the
U.S. Geological Survey). However, as the details of needed research were compiled by
the three work groups listed in Appendix A, the Executive Committee and DOE sponsors
realized that even this initial set of activities would have broad applicability beyond
DOE’s cleanup needs. This draft (Revision 0.0) has been extensively revised to express
this broader relevance, even though the participation by other agencies to this point has
been limited.
Given the broad potential applicability of the S&T work identified here—and thesheer scale of the effort that implementation will require—a coordinated approach
involving all of the agencies named above, and perhaps others,17 is essential. From thisperspective, the current version of the roadmap is unquestionably a first step for
consideration and revision in some subsequent context where the other agencies are more
fully involved as partners with the DOE. Precedents such as the interagency coordinationon the U.S. Global Climate Research Program provide the Executive Committee withhope that its attempt to reach beyond DOE sites will not fall on deaf ears.
This cooperation in further shaping a national roadmap for vadose zone S&T should
extend even beyond the federal sphere. States and local governments face significant
problems related to vadose zone contaminant transport. The contaminants typicallyderive from industrial sites, suburban septic tanks, old gasoline stations and petroleum
distribution centers, agricultural activities, and municipal refuse rather than nuclear fuels
production. Yet, much of the research results and infrastructure proposed here could help
with their problems as well.
In addition, State health and environmental authorities are playing an increasingly
active role in cleanup agreements with federal facilities. The communities near thosefacilities—or anywhere downgradient or downstream from them—are the people mostdirectly impacted by the possibility or reality of groundwater contamination. Thus many
linkages—prerequisites, influences, and synergies again—exist to tie the activities of
DOE, DOD, and EPA with State and local governments. If this initial roadmapping
exercise is sustained in some form, the Executive Committee believes there should besome mechanism to represent these broader constituencies in the process.
5.5

The Ultimate Driver: Protecting the Nation’s Groundwater Resource

Despite the arguments stated above for the investment value of research or thenecessity for cooperation across institutional boundaries, the Executive Committee knowsthat serious challenges and obstacles will confront any attempt to pursue and improve thisambitious roadmap. If the effort has not been futile, if in time a goodly share of the17

The vadose zone as a moisture and heat source and sink in models of atmospheric-terrestrial-oceanic
coupling is emerging as an issue for refining projections of climate change due to accumulation ofgreenhouse gases. In this respect, the National Aeronautics and Space Administration (NASA) could be
another entity to which this roadmap has relevance.

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results are realized because sufficient support has been mustered and directed well, it will
happen for one reason: the nation needs to protect its groundwater.
Throughout history, the fate of nations, and even of civilizations, has risen and fallenwith the adequacy of safe water supplies: water for man and beast to drink, water to growcrops, sustain fertile soils, and form aquatic ecosystems. Increasingly we depend on the
groundwater to meet our needs for potable water and irrigation. Even where we can tap
surface waters for these purposes, the purity of groundwater that invisibly flows into
surface drainages can become an issue. The United States has been blessed with
abundant groundwater; its benefits are everywhere around us.
Unfortunately, we have only recently realized that transport of contaminants throughthe vadose zone can threaten the groundwater resource in ways our predecessors neverconsidered. Once contaminants are in the subsurface, it is far better to stop them in thevadose zone than prevent their spread after they reach groundwater. The ultimate driverfor significant investment of national treasure in the research and infrastructure activities
contained in this roadmap is to protect an even more valuable national treasure, ourgroundwater resource.

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ACKNOWLEDGMENTS
The Executive Committee for the DOE Vadose Zone Science and Technology
Roadmap would like to acknowledge those who played a key role in the development of
this work. The DOE-Idaho Falls Field Office sponsored this effort under its
environmental management program. The Committee owes special thanks to Clay
Nichols, Chief Scientist, for his leadership, and to Brooks Weingartner for his day-to-day
guidance and support. We thank all of the workshop participants for their time andthoughtful contributions. We especially appreciate the efforts of the Workgroup Chairs
who carried the burden of developing the core of this roadmap. We are grateful for the
support of other federal agencies, notably, the U.S. Department of Agriculture, the U.S.
Geological Survey, the U.S. Department of Defense, and the U.S. Environmental
Protection Agency for allowing their personnel to participate. We thank the Washington
Advisory Group for its initial guidance and support of this project, and the staff ofMcNeil Technologies, especially Devon Streit, who facilitated the process and kept us on
the right path.

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REFERENCES
Alley, W.M., T.E. Reilly, and L. Franke. 1999. Sustainability of Ground-Water Resources.
U.S.G.S. Circular 1186. U.S. Geological Survey, Reston, Virginia.
Barbash, J.E., G.P. Thelin, D.W. Kolpin, and R.J. Gilliom. 2001. Major Herbicides in Ground
Water: Results from the National Water-Quality Assessment. Journal of Environmental
Quality 30(May-June): 831–845.
Brown, L. 2001. “Running on Empty,” Forum for Applied Research and Public Policy: Spring
2001.
DOE. 1999a. Catalog of Ongoing Vadose Zone Research as it Pertains to DOE Site Cleanup.
DOE/EM-506. Office of Science and Technology, Office of Environmental Management,
U.S. Department of Energy. December 1999.
DOE. 1999b. From Cleanup to Stewardship. DOE EM-0466. Washington, D.C.: Office ofEnvironmental Management.
DOE. 2000. Alternative Landfill Cover. Innovative Technology Summary Report. DOE/EM0558. Office of Environmental Management, U.S. Department of Energy.
EPA. 1994a. Symposium on Natural Attenuation of Ground Water. EPA/600/R-94/162. Officeof Research and Development, U.S. Environmental Protection Agency, Washington, D.C.
September 1994
EPA. 1994b. Methods for Monitoring Pump-and-Treat Performance. EPA/600/R-94/123.
Office of Research and Development, U.S. Environmental Protection Agency, Ada,
Oklahoma. June 1994
EPA. 1997. Proceedings of the Symposium on Natural Attenuation of Chlorinated Organics in
Ground Water. EPA/540/R-97/504. Office of Research and Development, U.S.
Environmental Protection Agency, Washington, D.C. May 1997.
EPA. 1999. Test Methods for Evaluating Solid Waste: Physical/Chemical Methods; Third
Update; Final Update 3a. SW-846.3-3a. Office of Solid Waste, U.S. Environmental
Protection Agency, Washington, D.C.
Everett, L.G. 2001. “Long-term institutional and regulatory/policy issues relating to the vadosezone.” Paper presented at the 27th annual Waste Management Symposium, February 25–
March 1, 2001, Tucson, Arizona.
Freeze, R.A., and J.A. Cherry. 1979. Groundwater. Prentice-Hall. Englewood Cliffs, New
Jersey.
Henson, R., S. Horstmeyer, B. Rippey, P. Kocin, and E. Pinder. 1999. “The 20th Century’s Top
Ten U.S. Weather and Climate Events.” Weatherwise. November/December 1999 issue.
Available on-line at <www.weatherwise.org/99.nd.20thcent.html>.
Idaho National Engineering and Environmental Laboratory. 2000. Vadose Zone Science
Integration and Technical Basis (DRAFT)

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Loaiciga, H., S. Renehan, S. Weeks, and P. Wang. Survey of Environmental Monitoring and Site
Characterization Technologies at DOE Sites. Prepared for DOE Special Technologies
Laboratory. University of California, Santa Barbara. September 1997.
Long, J. C. S., and P, A, Witherspoon. 1985. “The relationship of the degree of intersection topermeability in fracture networks.” Journal of Geophysical Research 90: 3087–3098.
Looney, B.B., and R.W. Falta. 2000. Vadose Zone: Science and Technology Solutions.
Columbus, Ohio: Battelle Press.
National Drought Policy Commission. 2000. Preparing for Drought in the 21st Century. May
2000. Available on-line at <www.fsa.usda.gov/drought/finalreport/fullreport/
reportdload.htm>.
National Research Council. 1997. Barrier Technologies for Environmental Management:
Summary of a Workshop. Washington, D.C.: National Academy Press.
National Research Council. 1999. Groundwater and Soil Cleanup: Improving Management of
Persistent Contaminants. Washington, D.C.: National Academy Press.
National Research Council. 2000. Research Needs in Subsurface Science. Washington, D.C.:
National Academy Press.
Paillet, FL. 1998. “Flow modeling and permeability estimation using borehole flow logs inheterogeneous fractured formations.” Water Resources Research 34(5): 997–1010.
Scanlon, B.R., S.W. Tyler, and P.J. Wierenga. 1997. “Hydrologic issues in arid, unsaturated
systems and implications for contaminant transport.” Reviews in Geophysics 35: 461–490.
Solley, W.B., R.R. Pierce, and H. A. Perlman. 1993. Estimated Use of Water in the UnitedStates in 1990. U.S.G.S. Circular 1081. U.S. Geological Survey, Reston, Virginia.
U.S. General Accounting Office. 1998. Nuclear Waste: Understanding of Waste Migration at
Hanford is Inadequate for Key Decisions. GAO/RCED-98-80. Washington, D.C.
Ward, S.H., ed. 1990. Geotechnical and Environmental Geophysics. Investigations inGeophysics. IG-5 Set. Tulsa, Oklahoma: Society of Exploration Geophysics,.
Wilson, L.G. 1982. “Monitoring in the vadose zone: Part II.” Ground Water Monitoring Review
1982: 31–42.
Wilson, L.G. 1983. “Monitoring in the vadose zone: Part III.” Ground Water Monitoring
Review 1983: 155-166.
Wilson, L.G., L.G. Everett, and S.J. Cullen, eds. 1995. Handbook of Vadose Zone
Characterization and Monitoring. Boca Raton, Florida: Lewis Publishers.

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ACRONYM LIST
ASCI

Accelerated Strategic Computing Initiative

DOD

U.S. Department of Defense

DOE

U.S. Department of Energy

DUS

Dynamic Underground Stripping

EPA

U.S. Environmental Protection Agency

GHCB

Geological, hydrologic, chemical, and biological

GIS

Geographical information system

HPO

Hydrous Pyrolysis Oxidation

IFE

Integrated field experiment

INEEL

Idaho National Engineering and Environmental Laboratory

LLNL

Lawrence Livermore National Laboratory

MCL

Maximum Concentration Limit

NAPL

Non-aqueous phase liquid

NAWQA

National Water-Quality Assessment

PSE[Vadose zone] problem solving environment

R&D

Research and development

RCRA

Resource Conservation and Recovery Act

S&T

Science and technology

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APPENDIX A. ROADMAP CONTRIBUTORSThe Executive
Committee

Physical Processes
Work Group

Characterization andMonitoring Work Group

Simulation and ModelingWork Group

Chair: Daniel Stephens

Chair: Rien van Genuchten

Co-Chair: David Borns

Chair: John Wilson

Daniel B. Stephens & Associates

United States Department ofAgriculture

Sandia National Laboratories

New Mexico Institute of Mining andTechnology

Idaho National Engineering andEnvironmental Laboratory

Vice Chair: Brian Looney

Schlumberger-Doll Research

David Borns

Fred Brockman

Pat Brady

Todd Arbogast

Sandia National Laboratories

Pacific Northwest National
Laboratory

Sandia National Laboratories

University of Texas, Austin

Alexander Dyhkne

Schlumberger-Doll ResearchMarkus FluryPat Berge

Russian Academy of Sciences

Carl Enfield

Washington State University

Lawrence Livermore National
Laboratory

Environmental Protection Agency

Bill Glassley

Alan Flint

Lorne Everett

Lawrence Livermore National
Laboratory

United States Geological Survey

Lawrence Berkeley National
Laboratory

Bob Lenhard

Glendon W. Gee

Andy Felmy

Pacific Northwest National
Laboratory

Pacific Northwest National
Laboratory

Bob Glass

Tim Ginn

Sandia National Laboratories

University of California, Davis

Susan Hubbard

Larry Hull
Idaho National Engineering andEnvironmental Laboratory

Vice Chair: Steve Kowall

Darwin Ellis

The IT Group

Michael Graham
Bechtel Hanford, Inc.

Frank Parker
Vanderbilt University

Co-Chair: Darwin Ellis

Savannah River Technology
CenterVice Chair: John Ullo
Schlumberger-Doll Research

Pacific Northwest National
Laboratory

Peter Lichtner

Boris Faybishenko

Rien van Genuchten

Los Alamos National Laboratory

United States Department ofAgriculture

Utah State University

Lawrence Berkeley National
Laboratory

Cathy Vogel

Kate Scow

Michael D. Knoll

Cass T. Miller

Department of Defense, Strategic
Environmental Research andDevelopment Program

University of California, Davis

Boise State University

University of North Carolina

David Stonestrom

Ernie Majer

Jirka Simunek

United States Geological Survey

Edwin Weeks

Leslie Smith

Lawrence Berkeley National
Laboratory

United States Department ofAgriculture

United States Geological Survey

University of British Columbia,
Vancouver

Earl Mattson

Wendy Soll
Los Alamos National Laboratory

Robert Smith

Idaho National Engineering andEnvironmental Laboratory

Idaho National Engineering andEnvironmental Laboratory

Mike Powers
United States Geological Survey

Ed Sudicky

Annette Schafer

University of Waterloo, Canada

Idaho National Engineering andEnvironmental Laboratory

John Wilson
New Mexico Institute of Mining
and Technology

Dani OrAndy Tompson

Bridget Scanlon

Lawrence Livermore National
Laboratory

Texas Bureau of Economic
Geology

Tim Scheibe
Pacific Northwest National
Laboratory

Buck Sisson
Idaho National Engineering andEnvironmental Laboratory

Everett Springer
Los Alamos National Laboratory

Don Steeples
University of Kansas

Scott Tyler
University of Nevada, RenoPeter Wierenga
University of Arizona

Mike WiltEMI

Jim Yeh
University of Arizona

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APPENDIX B. TABLE OF ROADMAP ACTIVITIES WITH TASKSAND STATUS POINTS#1 Physical Description of Flow & Transport
Near Term

Acti vi ty PH1: Assess the importance of flu id flow and chemical transport processes
and subsurface properties relevant to site characterization, remed iation and long-term
stewardship.
Status: Subsurface properties (e.g., gravitational, pressure, temperature andchemical gradients) of importance to flu id flow and chemical transport at
contaminated vadose zone sites have been identified and assessed.
Acti vi ty PH2: Design and conduct laboratory and field experiments to resolve
critical gaps in understanding fluid flow and chemical transport processes in granular
med ia. Criticality of gaps is to be assessed by relevance to environmental restorationand long-term stewardship missions of the DOE and other agencies.
Status: Crit ical gaps that can be answered within a decade through lab andcontrolled field experiments have been identified and prioritized.
Task: Design, imp lement, and analy ze results of laboratory and field
experiments for the prioritized crit ical gaps.
Acti vi ty PH3: Imp rove process-based understanding and models for flo w andtransport in macroporous soils and unsaturated fractured rocks.
Task: Develop realistic representations of pore-space geometry of, and flu id
flow in, fractured media using geological, pedologic, and topologicalcharacterization techniques.
Task: Develop and implement imp roved descriptions of matrix-fractureinteractions.
Task: Develop general constitutive relationships for both granular andstructured media.
Task: Develop pore network and other models based upon appropriate
equations (e.g. Nav ier-Stokes), and devise methods for upscaling processes
and/or properties from sample to format ion scales.
Task: Incorporate solid surface heterogeneity (pore and samp le scale) withdetailed hydrodynamics into solute transport models (to model opportunity
times for reactions, streaming potentials, and other processes or variables).
Acti vi ty PH4: Develop methods for modeling scale-dependent properties andprocesses and for assimilating data fro m different scales into these models.
Task: Develop and implement imp roved models for evapotranspiration androot water uptake as a function of water stress and other factors.
Task: Develop process-hierarchical approaches for describing and modeling
controlling processes (e.g., models of increased comp lexity for flow in
structured media, or increasingly sophisticated process-based approximations
for gaseous transport or the flow o f non-aqueous phase liquids).
Status: Methods have been developed to quantify spatial variability in flow
and transport parameters, fluid p roperties, thermal properties, and biologicaland chemical reactions

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Near Term

Task: Investigate potential of collecting/inverting multi-scaled data toprovide informat ion about variability as a function of scale.
Task: To understand how different measurement methods scale fro m one
level of support to another, experiment with modifying the acquisition
parameters for a certain type of method to sample d ifferent scales ofvariability.
Status: Methods have been developed for measuring physical processes andproperties and their uncertainties across different scales. The multi-scale data
fro m these methods can be assimilated into process models in which theproperties and processes can be propagated (in simu lations) as, for example,
governing equations, driving forces, and/or med ia properties.
Status: Linkages between relevant small-scale processes and properties withlarger-scale flow and transport behavior have been identified for cases where
no simple upscaling is possible.
Status: M icrobio logy modules are incorporated into physical models of solidgas-liquid environ ments.
Status: Solid surface evolution due to biogeochemical react ions(precip itation-dissolution, reduction-oxidation, and other react ions that canchange solid-phase geometry and density of exchange sites) has been
incorporated into transport models necessary for long time-scale simu lations.
Status: Models for unsaturated flow and transport in different types of porous
med ia have been developed that are both process-adaptive and scale-adaptive.
These models invoke the appropriate processes at the appropriate scale and
emp loy the corresponding transport and hydraulic properties.
Acti vi ty PH5: Imp rove the state of practice in flow and transport models used bygovernment agencies for VZ contamination simulations, beginning with DOE.
Status: DOE flo w and transport prediction models and solutions have been
updated by incorporating known models/modules with a mo re soundphysical-chemical basis.
Task: Integrate critical elements of chemistry and microbial activity inmodels for liquid flo w and solute transport.
Acti vi ty PH6: Develop, imp rove, and confirm of methods for measuring basic
hydrologic properties.
Status: Moisture content, matric potential, and temperature measurements are
no longer a majo r source of uncertainty for site-wide monitoring andmodeling. Monitoring approaches for these properties are robust enough tocover long-term stewardship responsibilit ies.
Acti vi ty PH7: Imp rove the capability to track subsurface fluid flows with increased
precision, over larger areas, and at greater depths underground.
Status: Improved resolution and decreased uncertainty. Examp le, fluid
movement (such as in an infiltrat ion event) in a 10 m X 10 m area, at depths
up to 100 m, can be tracked to a p recision of 10 percent.

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Near Term

Status: Further improvements in resolution and uncertainty reduction.
Example: fluid movement in a 50 m X 50 m area, at depths up to 100 m, canbe tracked to a precision of 5 percent.
Status: Great ly imp roved resolution and reduced uncertainty. Examp le: athree-dimensional pulse of water (2 m X 2 m) can be identified to a precisionof 2 percent at depths up to 100 m.
Acti vi ty PH8: Optimize the use of natural and anthropogenic tracers for determining
directions and rates of transport, assessing flow processes, and validating numericalmodels.
Task: Develop, test, and confirm the inverse process of using tracers toestimate flu xes and ages of pore water. Include methods to propagate
uncertainties in tracer measurements to obtain uncertainties in calculated
flu xes and ages.
Status: A variety of tracers are availab le fo r use in locating contaminants,
establishing the role of surface boundary conditions in specific subsurface
environments, and obtaining point estimates of flu xes and ages.
Acti vi ty PH9: Develop capability to detect the presence and movement of flu id in
fractures and fracture networks.
Status: The p resence of flu id in individual fractures can be detected in somecases.
Task: Quantify the relationships among the most likely geophysical methods
or comb inations of methods that will provide fracture d iagnostics.
Status: Contaminant fluid in fractures can be detected in most cases.
Task: Discover and quantify new relationships between surface geophysicalmeasurements and fractures, so that fractures a few centimeters across at
depths of 10 meters can be routinely mapped.
Status: Contaminant fluid in fractures in real time can be detected andquantified fro m the surface or in boreholes.
Status: Lo w-cost, automated, and reliab le geophysical techniques areavailable for mapping fractures immed iately at the field site, without delays
for processing or analysis.
Acti vi ty PH10: Characterize the petrophysical relationships for translating
geophysical attributes in near-surface strata into estimates of hydrologic parameters
relevant to vadose zone contamination (e.g., porosity and water content).
Status: Generalized petrophysical relationships between geophysicalattributes and hydrologic parameters have been developed for near-surface
environments.
Task: Investigate how multip le types of geophysical and other data reduce
uncertainty in applying petrophysical relationships and can aid in resolving
issues of non-uniqueness in relationships between geophysical and hydrologic
parameters.
Status: The mechanisms of geophysical energy propagation at the fieldtomographic scale within unconsolidated or loosely consolidated, lowpressure, granular porous material are understood.

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Near Term

Status: Jo int and constrained inversions that honor all data can be performed.
How addit ional data imp rove the estimate and decrease the estimation error isunderstood. Data with different measurement scales can be incorporated in
the inversion process correctly.
Task: Develop a quick and reliab le way to assess the scale of a vadose zone
contamination problem relative to the scale of the hydrologic heterogeneity sothat the most appropriate techniques and acquisition parameters can beselected for characterizing the key parameters that control flow and transport
at that site.
Status: Methods to scale between lab-scale and field-scale measurements are
known and in use. A variety of differently scaled data can be reliably
incorporated into geophysical inversions to provide an integrated andhierarch ical interpretation of hydrologic properties.
Acti vi ty PH11: Improve and apply geophysical methods for characterizing nearsurface environments typical of sites with vadose zone contamination.
Task: Develop automatic data picking and quality control approaches forcrosshole tomographic methods.
Task: Investigate the utility of constrained and joint inversion for imp roved
estimation of hydrologic parameters. Develop stochastic inversion
procedures that yield distributions of possible geophysical attributes at eachlocation.
Status: Stochastic estimat ion techniques that provide an estimate of theproperty of interest, as well as information about its uncertainty, have beentested and applied to contaminated vadose zone sites.
Status: Incorporate measurement support scale, and other means ofrecognizing the importance of scale, when applying geophysical methods toestimate hydrologic properties and correlation lengths.
Status: Hydrologic p roperties (e.g. water content, permeability and porosity)and their associated uncertainties and spatial correlation functions are being
estimated fro m different types of geophysical data such as crosshole
tomographic imagery. These estimates are conditioned to direct
measurements, with attention to scale, using hierarchical spatial scaleestimation procedures with mu lti-scaled data.
Acti vi ties PH10 and PH11:
Status: Practical guidelines for different environments allo w quick field tests
to determine the characterization regime into wh ich the vadose zone at acontaminated site falls. The governing petrophysical relat ionship for that
regime is used to interpret the geophysical data to obtain first-pass estimatesof key flo w and transport parameters.
Status: To mographic methods can supply real-time, mu ltidimensional(spatial and temporal), automat ic interpretations of hydrologic properties orchanges in properties due to bacterial modificat ion, environ mental
remediation, infiltration, and other dynamic processes. The fully automatedinversion process may also incorporate varying scales, but must provide realtime estimates of hydrologic properties at high resolution.
HIGHLIGHTS OF EXPECTED RESULTS
Computer models used by federal agencies and others incorporate the best state-ofthe-art conceptual models and implementations (software modules).
We can detect the presence of fluid in fractures in some cases.
We can distinguish, in most cases, the subset of fractures that are conduits for fluid
flow and contaminant transport.
We can map and predict water distribution and flow through structured soils or
fractured rock at multiple spatial scales.
Monitoring data on fluid flow and contaminant transport can be interpreted andrepresented visually at site-wide scales in real-time.

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Near Term

Acti vi ty CH1 : Extend solution chemistry models to higher temperatures and ionicstrengths (e.g., Pit zer equations) relevant to VZ contamination problems.
Status: Solution chemistry models have been extended to temperatures andionic strengths needed for most VZ contamination problems, including DOE
contamination sites.
Acti vi ty CH2 : Improve the understanding of kinetic rate mechanisms and effect ive
surface areas, in order to develop improved rate laws.
Status: React ion kinetics and rate laws have been formulated that areappropriate for use in nu merical continuum models of reactive flow andtransport for many VZ contamination problems, including DOE sites.
Status: Databases of appropriate reaction rate constants applicable to refined
reaction rate laws have been developed through experimental studies.
Acti vi ty CH3 : Investigate cation exchange capacity and surface site
density/complexation reactions on mineral surfaces and colloids for systems typicalof VZ environ ments and contamination problems. Resolve the importance of lack ofcharge conservation in surface co mplexation models when co mbined with transport,
possibly by including streaming potentials in the formu lation.
Task: Determine if significant differences exist for measurement of cationexchange capacity and surface site density between in situ fieldmeasurements of undisturbed samples and lab batch measurements involving
disturbed media. Validate conditions under which batch Kd measurements
can be used to estimate retardation in variably saturated flo wing systems.
Status: The kinetics (including reversib ility) of ion exchange and surface
complexation react ions on mineral surfaces and collo ids has been determined
for most solution-solid systems relevant to VZ contamination problems.
Acti vi ty CH4 : Investigate the effects of dissolution and precipitation on porosity,
pore structure, and permeability. Study nucleation controls that may bias dissolution
and/or precipitation to particular pore environ ments.
Task: Develop a functional description for porosity/permeability evolution
reflecting chemical effects.
Task: Develop rate laws for glass dissolution and solid solutions that cover
more extended conditions typical of natural and contaminant-affected flow
fields. Imp rove models of nucleation processes.
Acti vi ties CH1 through CH4:
Status: Kinetics and rate laws have been formulated for ion exchange andsurface complexation processes coupled with mineral precip itation anddissolution. This knowledge has been validated in field experiments andincorporated in reactive flow and transport models for VZ systems.

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Near Term

Acti vi ty CH5 : Investigate phase boundary conditions occurring in VZ environ mentsthat may significantly influence liquid flo w and contaminant transport.
Task: Develop accurate models for mineral react ions in contact with a thinliquid film that may have different properties compared to bulk flu id (e.g., for
extreme evaporation conditions that may favor formation of evaporite mineralphases).
Task: Develop accurate models for mineral reactions in unsaturated systems
having variable gas phase chemistries (e.g., lo w and high CO2 or O2 ).
Acti vi ty CH6 : Improve and develop methods of identifying chemical contaminantsin the VZ.
Status: The p resence of individual chemical contaminants in soils or other
VZ strata can be determined fro m surface o r borehole measurements,
although field results may require verification with lab analyses.
Status: Concentrations of the most abundant species (except those at verysmall concentrations) can be determined within an order o f magnitude.
Status: Contaminated volumes can be isolated, and the concentration ofabundant chemical species can be determined to within 10 or 20 percent.
Status: The volu mes and spatial distributions of resident contaminants at ornear source discharge points can be quantified for metals, radionuclides, andorganics.
HIGHLIGHTS OF EXPECTED RESULTS
Reaction kinetics and rate laws (in solution) have been formulated for priority vadosezone conditions.
Individual chemical contaminants in the vadose zone can be detected.
We understand the kinetics for important chemical reactions at solid and liquidinterfaces (e.g., ion exchange and colloids) in vadose zone conditions.
Flow and transport models map and predict important vadose zone chemicalinteractions, including those involving mixtures of solids, liquids, and air.

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A National Roadmap for Vadose Zone Science and Technology#3 Biological Properties & Processes
Near Term

Acti vi ty B1: Understanding the mechanisms of microbial-contaminant interact ions.
Task: Quantify rates of microbial processes affecting inorganics, chelateinorganic co mplexes, inorganic co mp lexes, and organic contaminants;
identify the factors controlling those rates.
Task: Understand and predict how contaminant bioavailability affects/is
affected by, microbial processes.
Task: Characterize microbial-med iated corrosion and biodeterioration ofmaterials used to contain contaminants at sites with contained buried wastes.
Task: Improve the conceptual and mathemat ical characterization ofinteractions between microorganisms and contaminants (e.g., biodegradation,
immobilization, transformation), microbial and physical/chemical processes(coupled processes), and incorporate these relationships into reactive
transport models.
Task: Elucidate pore-scale interactions between microorganis ms andcontaminants, under undisturbed conditions, including studies: (1) at the
microscopic level; (2) at interfaces (solid/liquid, liquid/gas, liquid/liquid,
solid/gas, and along textural discontinuities); and (3) in b iofilms.
Task: Determine the importance to contaminant transport and preferential
flow of microbial attachment/detachment, biofilms, and microbial
associations with colloids.
Acti vi ty B2: Understand how mixtures of contaminants in DOE wastes affectmicrobial act ivity with respect to flow and transport of specific contaminants.
Status: Conditions under which to xicity of radionuclides, metals, or organics
prevent removal of readily degradable organic contaminants have been
identified.
Status: The rates of biodegradation of particular contaminants can bepredicted as a function of the type and concentration of other contaminantspresent.
Acti vi ty B3: Understanding microbial co mmunity co mposition and activity
Status: Rapid statistical/classificat ion methods for handling large data sets
generated from the characterizat ion of microbial co mmun ities have beendeveloped and applied.
Status: M icrobial d iversity in rep resentative VZ systems has beencharacterized (measured), and the factors governing diversity have been
determined. Relationships between diversity and community response tocontaminants have been determined.
Task: Understand the potential ro les of siderophore, surfactant, and chelate
production by microbial co mmun ities, including the plant root–microbialcommunity interface, on contaminant transformations in engineered
biotreatment zones and in contaminated sites without engineered
biotreatment.
Status: The spatial distribution of microbial b io mass, activity, andcommunity co mposition in the VZ can be predicted with respect tocontaminant distribution. Effects on the microbial distribution fro m water
inputs, contaminant flu xes, and duration of exposure to contaminants can also
be predicted.

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Near Term

Acti vi ty B4: Characterization methods to understand in situ rates and community
activities at scales relevant for field-scale modeling.
Task: Characterize microbial t ransport in different natural porous media andthrough/from engineered biotreat ment zones relevant for VZ contaminationsites (DOE and others). In particular, characterize transport throughunsaturated fine and coarse sands and fractured rock, as a function of water
saturation and solution chemistry.
Status: In situ rates of microbial biotransformation of contaminants at
contaminated sites (DOE and other VZ sites) can be predicted as a function ofsite and environmental conditions.
Status: Informat ion about the composition of VZ microbial co mmun ities has
been incorporated into pollutant fate and transport models.
Status: Transport of native and introduced microorganisms at contaminated
VZ sites (DOE and others) can be predicted.
Acti vi ty B5: Developing and imp roving measurement techniques for bioavailability.
Status: Improved bioavailability sensors and/or assays have been developed.
Status: In situ bioavailab ility sensors have been developed and are inapplication.
Acti vi ty B6: Developing and applying sensors and sensor systems for in situ ratemeasurements.
Status: Sensors and systems for in situ rate measurements have beendeveloped.
Status: Chemically reactive contact foils and films for in situ rates and/or
potential activ ity have been developed.
Acti vi ty B7: Developing and applying systems for measuring microbial co mmun ity
composition and activity.
Status: Sample-to-answer analytical systems for co mmunity co mposition andactivity have been developed.
Status: Spectroscopy-based and synchrotron-based inferences of microbialactivity have been developed.
Task: Perform lab studies and develop models of the bio-elect ric level as afunction of different soil types and microbes (aerobic versus anaerobic, avariety of metal-reducing and organics-reducing microbes).
Status: Inexpensive sample-to-answer analytical systems for co mmunity
composition and activity are being applied.
Task: Develop instrumentation to detect lower levels of act ivity and validate
this instrumentation in intermediate-scale and field-scale tests.
Acti vi ties B5 through B7:
Status: Econo mical analysis of spatial distribution and temporal dynamics has
been developed and applied.
Status: Nondestructive joint measurement of bio logical, geochemical, physical,
and hydrologic properties or processes has been extended to intact cores andpossibly to the subsurface.
Status: Pro xy measurements for microbiological properties and processes havebeen developed.

HIGHLIGHTS OF EXPECTED RESULTS
We understand and can predict how microbial processes affect or are a ffected bybioavailability of important contaminants.
We can measure biochemical rates, in situ bioavailability, and the composition andactivity of microbiological communities.
Reactive transport models can predict how microorganisms will interact withcontaminants.
Inexpensive systems are available to measure community composition and activity.
We can accurately predict site-specific biodegradation rates for important
contaminants.
We can take biological measurements along with others without destroying thesamples.

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Near Term

Acti vi ty COL1 : Improve samp ling and analysis for colloids and collo idal transport.
Task: Develop a scientifically based protocol for field based sampling andanalysis for collo ids and colloidally transported contaminants.
Task: Develop new sampling techniques for in situ measurements ofcolloidal particles in pore water.
Status: Mobile co llo ids are considered in samp ling and analyses protocols
for field studies and monitoring systems.
Acti vi ty COL2 : Studies of colloidal transport.
Task: Quantify effect of p referential flow on colloid t ransport.
Task: Understand relevance of collo id-facilitated transport to contaminant
movement under transient flow conditions, including wetting, dry ing, andinfiltrat ion processes.
Task: Quantify the potential for in situ collo id formation and mobilization
under conditions relevant for major VZ contamination sites, particularly inthe presence of extreme chemical conditions that can lead to dissolution andprecipitation of soil minerals.
Task: Evaluate the effects on production and behavior of microbial co llo idsof (1) changing contaminant flu x, (2) nutrient injection during engineered
bioremediation, and (3) cell to cell co mmunicat ion (quorum sensing) in
biofilms and other cell assemblages.
Task: Characterize colloid-contaminant interact ions as a function of solution
chemistry and water saturation, at both microscopic and macroscopic levels.
Task: Characterize colloid transport in different natural porous media
relevant for sites with contaminated VZs, In particu lar, characterize andquantify colloidal transport through unsaturated fine and coarse sands andfractured rock, as a function of water saturation and solution chemistry.
Quantify colloid interactions with solid-liquid and liquid -gas interfaces.
Acti vi ty COL3 : Models of colloidal transport.
Task: Model colloid transport and colloid-facilitated transport in unsaturated
soils, sediments, and fractured rocks.
Status: Improved conceptual and mathematical characterizations of colloidcontaminant-soil interactions and colloid-facilitated transport have been
incorporated into reactive transport models used by DOE and other agencies
for assessing VZ contamination.
HIGHLIGHTS OF EXPECTED RESULTS
We know how to detect mobile colloids and how to sample and analyze them.
Important colloid-contaminant interactions understood at micro and macro levels.
Flow and transport models can map and predict important colloidal interactions andtransport.

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A National Roadmap for Vadose Zone Science and Technology#5 Multiphase Flow & Transport
Near Term

Acti vi ty MP1 : Extend knowledge and predictability of flo w and transport processes
to mult iphase systems.
Task: Quantify effects of subsurface physical and biogeochemical
heterogeneity on mult iphase flow and transport processes.
Status: Upscaling procedures to apply lab-derived mu ltiphase constitutive
properties and parameters to the field scale have been developed.
Status: Process-based models can describe unstable and preferential flow of
aqueous and NAPL phases.
Task: Conduct mult iphase flow and NAPL transport experiments forrepresentative soils and contaminants, to elucidate real-world problems anddata limitations.
Acti vi ty MP2 : Studies of key contaminant mixtures (for DOE and othercontaminated VZ sites) as multiphase systems.
Task: Measure flow and transport properties of key contaminant mixtures.
Refine theory and numerical models to describe their flo w and transport in
relevant subsurface environments.
Task: Design, imp lement and analy ze controlled tests of complex
contaminant mixtures in highly heterogeneous systems.
Acti vi ty MP3 : Incorporation of understanding and models for mu ltiphase flo w andtransport into site assessments and remediat ion strategies.
Status: Remed iation strategies routinely take into account multiphase flow andtransport of site-specific contaminant mixtures.
Status: Nu merical models are being used to assess uncertainty in flow andtransport of comp lex contaminant mixtures at priority sites (including DOE
sites) and to support decisions with regard to remed iation and containment
strategies.
HIGHLIGHTS OF EXPECTED RESULTS
We can model processes with unstable or preferential flow of aqueous and nonaqueous phases.
We can detect and interpret multiphase flow and transport of complex contaminant
mixtures at contaminated sites.
Site assessment models incorporate multiphase flow and transport.

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Near Term

Acti vi ty UP1 : Studies of factors influencing unstable flo w.
Task: Identify directions for applying chaos theory in VZ hydrology by (1)reviewing the literature on physical, chemical, and biological processes inwhich unstable flow occurs; and (2) co mparing these processes andconditions with those occurring in the VZ.
Task: Perfo rm bench-scale and field -scale investigations of factors leading
to instability and chaotic-type flo w and chemical t ransport in VZ conditions.
Status: Criteria have been developed to identify the onset of unstable and/or
chaotic-type processes in VZ flow and transport
Task: To identify conditions for which unstable and/or chaotic-type
processes are important, design and perform field-scale infiltration tests withtracers at several sites with VZ contamination in heterogeneous soils andfractured rocks.
Task: To determine the main d iagnostic parameters of chaotic-type flows,develop software that reconstructs the system phase-space fro m scalar data.
Acti vi ty UP2 : Modeling unstable and chaotic flow in the VZ.
Task: Develop a series of models describing unstable flo w phenomena ofdeterministic chaos in unsaturated fractured rocks.
Task: Develop a new generation of mathematical and nu merical models to
describe unstable and chaotic-type flow processes in soils and fractured
rocks.
Task: Imp lement models of unstable and/or chaotic-type flow into other
deterministic and stochastic models used for predicting flow and transportand designing remediation activ ities.
HIGHLIGHTS OF EXPECTED RESULTS
We can identify the onset of chaotic and unstable processes.
We can determine whether and when chaotic conditions are important at a site.
Site assessment models incorporate models for chaotic and unstable flow.

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A National Roadmap for Vadose Zone Science and Technology#7 Understanding and Modeling Coupled Systems
Near Term

Acti vi ty CP1 : Imp rove existing or develop new databases for processes withcoupled GHCB properties.
Task: Update and check reliability of availab le databases used in coupledmodels. Make the reliable databases universally available, withrecommendations for usage.
Acti vi ty CP2 : Develop cross-disciplinary modeling approaches and imp lement
better models (representations) for key VZ flow and transport processes that crosstraditional discip linary boundaries.
Status: Better estimat ion techniques are available to facilitate routine
incorporation into process models of different types of GHCB data that havedifferent sampling scales and different spatial variability.
Status: Coupled processes with the highest priority for understanding VZ
fate and transport, and the gaps in understanding them, have been identified.
Status: Model studies have demonstrated capabilit ies and limitations of existing
coupled models. Procedures for their appropriate use have been codified and arewidely disseminated and accepted. Strongly coupled nonlinear phenomenarequiring development of new modeling approaches have been identified.
Task: Use the results from the identification of priority coupled processes andknowledge gaps about them to guide research on sufficiently realistic
representations of the highest priority processes.
Acti vi ties CP1 and CP2:
Status: Realistic representations of the priority coupled processes have beendeveloped, validated in field studies, and implemented in VZ fate and transportmodels.
Acti vi ty CP3 : Develop realistic representations for strongly coupled nonlinear
GHCB phenomena. Incorporate adequate models fo r these phenomena in t ransportmodels for VZ contamination sites.
Status: Models have been formulated fo r strongly coupled nonlinear GHCB
phenomena with high priority for VZ contamination studies. The modeled
phenomena may include mechanics of b iofilms; mult ivariate reaction kinetics;
saturation and colloid-facilitated transport; and scaling of coupled processes inspace and time.
Status: Constitutive theories and parameter databases for strongly coupled
nonlinear GHCB systems have been improved and incorporated into VZ
contaminant transport models.
Status: Models for strongly coupled nonlinear systems have been linked withscaling techniques.
Status: Mechanical-hydraulic and biochemical-hydraulic p rototypes areavailable for use.
Status: Models for strongly coupled nonlinear GHCB systems are supported
in the PSE

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Task: Test proposed models for strongly coupled nonlinear phenomena on
synthetic test problems, in s mall-scale and meso-scale lab experiments, and at
field-scale research sites.
Status: Improved co mputational algorith ms are availab le for strongly
coupled nonlinear GHCB processes.
Status: Models for strongly coupled nonlinear GHCB systems have beentested in field applications.
Acti vi ties CP1 through CP3:
Status: Realistic models are available for all coupled GHCB phenomena,
including strongly coupled nonlinear processes, that are important to VZ flo w
and transport. These models cover all important time and space scales, andmost of them are availab le within the PSE.
Status: Th ree-dimensional fully coupled heat and mu ltiphase flow andtransport models are the norm for decision support.
HIGHLIGHTS OF EXPECTED RESULTS
The highest priority coupled GHCB processes have been identified.
We understand the strengths and weaknesses of existing models.
Some of the important strongly coupled phenomena can be modeled.
Process models for important strongly coupled phenomena have been validated andfield-tested across spatial and temporal scales.
Site assessment models incorporate all important coupled GHCB phenomena
realistically.

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Near Term

Acti vi ty SC1: Develop simu lation tools for VZ systems that provide a hierarchy of
constitutive theories and that can simu ltaneously accommodate mult iple p rocesses on
different scales.
Status: A Monte Carlo p rototype for massive deterministic simu lations of scaling
issues has been designed and developed.
Task: Develop extensions of the massively deterministic Monte Carlo method toinclude probabilistic specificat ions of properties and constitutive hypotheses.
Status: The extended Monte Carlo modeling capability is in use as a testbed forevaluating scaling approaches and for advanced quantification of erro rs
associated with information loss in scaling.
Status: Scaling is being used to provide quantificat ion of relevant processes byidentificat ion of global system variants, such as contaminant trajectories andtravel times, non-aqueous mobile phase geometries, cumu lative reaction histories
over mu ltiple time scales, and subsurface ecosystem dynamics.
Status: New deterministic and probabilistic/stochastic approaches have beendeveloped to address cross-scale issues that commonly arise in VZ react ive flow
and transport.
Task: Undertake research to understand the time scaling of reaction systems andto solve problems of transients, episodic behavior, and boundary conditions.
Task: Refine co mputational techniques for solving hierarchically scaled flo w andtransport models; test these techniques with meso-scale lab experiments, small
scale field experiments, or other types of measurements of coupled GHCB
processes.
Task: Develop scaling methods for flo w in generalized (transient and spatially
non-uniform) coordinate systems to accommodate processes that vary on mult iple
spatial and temporal scales.
Status: Research has provided lin kages fro m constitutive theories and scale ofmeasurement to the quantities of ultimate concern to decision-makers. Theselin kages are in use for p lanning and implementing characterizat ion andmonitoring activities.
Status: Models for strongly coupled nonlinear GHCB systems are supported in
the PSE.
Task: Develop links between the scaling methods described above and themethods for uncertainty estimation and reduction in the PSE.
Status: Research is being done on spatial and temporal scaling in support ofsource-identification, as well as other inverse problems.
Status: Strongly transient coupled GHCB processes at applied field sites canbe modeled over mu ltip le time horizons.
Status: Aspects of scaling theory have been unified and co mpletely linked withmethods for uncertainty estimation and reduction in the PSE.

HIGHLIGHTS OF EXPECTED RESULTS
We can si mulate scaling problems of important GHCB phenomena using
probabilistic modeling.
We can measure and model coupled GHCB phenomena across spatial scales.
Site models incorporate strongly transient and coupled GHCB phenomena for
multiple time periods.
Site models incorporate scaling with estimates of uncertainty, and the models canpropagate uncertainty estimates across spatial and temporal scales.

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Near Term

Acti vi ty UC1: Catalogue, assess, and priorit ize R&D needs for addressing thedifferent sources of uncertainty in models of VZ flo w and transport.
Status: State-of-the-art methods of uncertainty estimation and reduction,
especially for risk analyses, have been catalogued and assessed.
Status: Sources of uncertainty in VZ modeling, including choice of conceptualmodel, geological heterogeneity; parameter values; and initial and dynamic
boundary conditions, have been quantified and R&D needs to address them havebeen priorit ized
Task: Develop and test new theories and methodological approaches fordescribing and understanding the spatial and temporal structures of naturally
occurring heterogeneities and fluctuations. Use advanced geological modeling tocapture both flow-sensitive and chemical spatial heterogeneity.
Status: Uncertainties fo r flow models of highly heterogeneous porous andfractured media, affected by the fracture-matrix interactions and by film flo w indry formations, have been identified and evaluated.
Acti vi ty UC2: Research to decrease uncertainties in VZ modeling.
Task: Analyze existing long-term geological, hydrologic, chemical, andbiological records to improve conceptual models, reduce their uncertainties, andreduce or quantify the uncertainties in estimates of parameters and boundary
conditions used in VZ models.
Task: Test candidate methods for uncertainty estimation and reduction, andapplications of these methods, on synthetic test problems, s mall-scale and mesoscale lab experiments, and field-scale research sites.
Task: Evaluate effects of uncertainties for invasive and noninvasive fieldcharacterization and monitoring methods with different scales and degrees ofresolution.
Status: Uncertainty estimation and reduction methods resulting fro m the Activity
UC2 tasks with mid -term endpoints (see above) are in use as standard practice atseveral typical sites with VZ contamination.
Status: New, mo re sophisticated and efficient probabilistic approaches to
uncertainty estimat ion and reduction have been developed and tested.
Status: Uncertainty estimation and reduction methods are in use to predict thevalue of new data, to optimize the design and operation of characterization andmonitoring activities, and to automatically update a model when new data
becomes available.
Task: Develop uncertainty and inverse methods that self-adaptively suggest
modified conceptualizations or parameterizations.
Status: Forward and inverse models accounting for uncertainty are fu lly
integrated into the VZ PSE.

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Near Term

Acti vi ty UC3: Imp rove computational methods for representing and propagating
uncertainties in VZ models.
Status: Nu merical algorith ms have been improved to increase the efficiency of
VZ Monte Carlo simu lations.
Status: More realistic treat ment of uncertainties caused by surface boundary
conditions have been incorporated in VZ models.
Status: Support for uncertainty analyses has been incorporated in VZ PSE.
Status: Methods to display the degree of uncertainty fro m different sources andin aggregate (processes, coupling, parameters and properties, variability, etc.)
have been developed and incorporated in VZ system models. These methods
exploit advanced visualization techniques and other sensory (e.g., sound andtouch) interactions with models and data.
Status: Users of VZ system models are automatically alerted to possible
limitations caused by uncertainty.
Task: Link the analysis of modeling uncertainty with practical problems of a
facility designer. Integrate uncertainty estimation and reduction with estimation
and reduction of numerical errors. Incorporate these modeling imp rovements into
the VZ PSE.
Status: Uncertainty analysis has been coupled to management models and the
VZ PSE to help make decisions concerning characterizat ion, monitoring, andremediation design and operation.
Acti vi ties UC1 through UC3 :Status: Uncertainty estimation techniques are incorporated in co mmonlyused biogeochemical models and models of mult iphase flow in fractures.
Status: Uncertainty estimation and reduction are standard practice and are in
use for characterization, mon itoring, remediat ion, and stewardship decisions.
HIGHLIGHTS OF EXPECTED RESULTS
We have identified and understand the sources of uncertainty for monitoring andmodeling vadose zone sites.
We have assessed and catalogued the state-of-the-art methods for estimating andreducing uncertainty.
We have developed and tested new probabilistic approaches for estimating andreducing uncertainty.
We can optimize characterization and monitoring systems to reduce uncertainty, andwe can predict the value of additional data for reducing uncertainty.
Site assessment models incorporate techniques for estimating and reducing
uncertainty in making decisions on site cleanup and stewardship.

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Near Term

Acti vi ty MON1: Build, catalogue, and update conceptual models for fate andtransport of VZ contaminants, using field data on specific contaminant plumes toselect and imp rove models for the catalogue.
Status: At least 2 or 3 conceptual models for fate and transport of particular
contaminants, including contaminants of particular interest to DOE, havebeen built, catalogued, and updated using field data on specific contaminant
plumes fro m DOE sites or other VZ contamination sites.
Status: Field measurements fro m within and outside the DOE co mp lex havebeen compiled to provide broad-based technical support for the catalogue offate and transport models. Characteristic transport distances, chemical
controls on attenuation, and hydrologic factors have been determined on asite-specific basis, but these features have been used collectively to update
the conceptual models in the catalogue.
Status: Contaminant-specific monitoring needs have been catalogued.
Current “standard” monitoring approaches that cannot conceivably update orrefine the catalogue of conceptual models for attenuation of a specificcontaminant have been identified.
Acti vi ty MON2: Coordinate effort to collect long-term monitoring lessons learned
fro m across DOE sites and fro m other agencies with monitoring experience andexpertise.
Task: Use the gathered monitoring data and lessons learned to institutionalizea reflexive and iterative lin kage between monitoring and model refinement
Task: Use the gathered monitoring data and lessons learned to (1) condense
the catalogue of conceptual models fo r contaminant attenuation/fate and (2)standardize mon itoring approaches.
Acti vi ty MON3: Define monitoring requirements and improve/develop monitoring
approaches for chemical contaminants.
Status: In situ burial or d isposal configurations (barrels, dru ms, boxes, andsubsurface structures) can be delineated and distinguished fro m cultural featuresand soils.
Status: A cost-effect ive real-t ime mon itoring and data analysis system has beendeveloped that provides early warn ing of contaminant discharges to the VZ.
Status: Contaminant-specific monitoring needs have been catalogued.
HIGHLIGHTS OF EXPECTED RESULTS
Several conceptual models for fate and transport (beginning a catalogue) have beenvalidated with field data representing an emerging set of standard monitoring
approaches.
Researchers, site operators, regulators and stakeholders can access a catalogue of
proven fate and transport models with data sets for priority vadose zone cleanup sites.
Real-time monitoring systems at sites with vadose zone contamination provide early
warning of contaminant discharge or movement.
The model catalogue has been condensed and updated, and monitoring approaches
have been standardized.

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Near Term

Acti vi ty IV1 : Improve and test techniques: (1) for estimat ing model input
parameters, including boundary conditions and properties that control flow andtransport and, (2) for model integration, through improved measurement systemdesign and/or improved inverse modeling of input parameters.
Task: Develop models of samp ling events and instrument response, to be
used to imp rove instrument design, for a variety of invasive and non-invasive
methods for characterizat ion and monitoring.
Task: Develop new inversion techniques for estimat ing the input parameters
in models of transient flo w and transport processes.
Task: Design and conduct controlled field experiments that distinguishamong conceptual models representing different sides of issues in VZ flo w
and transport.
Status: Improved methods for inverse modeling and estimat ing probabilistic
uncertainty have been tested through meso-scale lab and field-scale
experiments.
Status: A h ighly integrated Shared Vadose Model has been developed,
validated, and is being applied. This model is a subset of the PSE in wh ich
the value of new data is continually assessed as part of an observation–
prediction–decision support (cost analysis) process.
Acti vi ty IV2 : Develop new tools to test and validate VZ models and techniques,
such as inversion methods, for integrating data and estimat ing key parameters.
Task: Define synthetic test problems and use them to conduct comparative
studies of existing techniques for inverse modeling and model validation.
Status: Integrated meso-scale lab and field experiments have been performed
to build databases suitable for testing and validating specific models.
Status: A co mputational test bed to assist in testing and validating models has
been incorporated into the VZ PSE.
Status: Support for inverse methods and for decision support simu lations has
been added to the PSE.
Status: GIS have been linked with, o r otherwise functionally incorporated
into, the PSE.
Acti vi ty IV3 : Conduct VZ field experiments to test and refine models andmeasurement techniques, including advances in instrumentation, tracers, bio logicalproperties, and emplacement technologies, as well as mathematical and statisticalbases for design.
Status: Models can be tested by comparing model predict ions to short-term(and eventually long term) field observations from field test sites andmonitoring networks at contamination sites.

Acti vi ty IV4 : Apply improved methods and tools for integration and validation toreal-world problems of managing VZ contamination.
Status: Model testing and validation methods are being applied at major VZ
contamination problems, including DOE sites.
Status: Better inverse methods for estimating parameters, boundary conditions,and the uncertainties in these estimates, and better methods for conceptual model
validation, have been developed and validated using synthetic problems,
experiments, and site data. They are being used to guide characterization andmonitoring activities at sites with major VZ contamination problems, including
DOE sites.
Acti vi ties IV1 through IV4:
Status: Models are an effective bridge to visualize and co mmunicate
findings fro m scientists to policy-makers and stakeholders
HIGHLIGHTS OF EXPECTED RESULTS
We can compare modeling techniques using a standard set of synthetic test problems.
We have models for sa mpling events and instrument response to improve
instrumentation and network design for characterization and modeling.
We can test and validate models and measurement methods in laboratory and field
experiments following standard protocols.
Site-wide assessment models are credible to both scientific and public policy
communities.

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Near Term

Acti vi ty G1: Build and extend a virtual library of qualified GHCB data.
Task: Tabulate known GHCB features for priority sites with VZ
contamination and representative GHCB characteristics.
Status: GHCB virtual library is operational and contains qualified GHCB
data for key sites with VZ contamination problems.
Status: Scale parameters are being reported to the GHCB v irtual library, as
well as measured values and distributions. VZ scientists are comfortableinterpreting their measured data using a hierarchical structure of organizationthat can exist in natural geological environ ments.
Acti vi ty G2: Develop prototypical numerical models that can be used to implementsite-specific four-dimensional GHCB framework models incorporating site-relevant
GHCB parameters and processes.
Status: Prototype GHBC models are availab le that run with GHBC virtual
library data and/or other suitably structured datasets.
Status: GHBC models and virtual library datasets are adequate to simulate
the critical features, parameters and processes for the DOE VZ p roblem sites
and other sites of national interest. The simulat ions of flow and transport areconsistent with all existing qualified data and observations.
HIGHLIGHTS OF EXPECTED RESULTS
A virtual library of qualified GHCB data for priority contaminated sites is available
to researchers, site operators, regulators, and the policy communities.
Virtual library data can be run on prototype models that incorporate a GHCB
framework.
We can si mulate critical features of priority contaminated vadose zone sites using
GHCB models and virtual library data.

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A National Roadmap for Vadose Zone Science and Technology#13 Sensors, Instrumentation & Emplacement
Near Term

Acti vi ty SIE1: Understand the effects of sensor emplacement and apply thisunderstanding to improving sensor emp lacement approaches.
Status: Methods for min imization of emp lacement effects, such as
microdrilling and coiled tubing, have been demonstrated successfully atimportant sites of VZ contamination, including DOE sites with high levels ofradiological and chemical hazards.
Status: New drilling techniques for sampling and for sensor emplacement
have been developed and tested.
Task: Develop min imally invasive methods and approaches to correcting for
emp lacement effects.
Status: Non-invasive methods or methods to fully correct fo r emp lacement
effects are available for all characterizat ion and monitoring needs.
Acti vi ty SIE2: Imp rove cost-effectiveness of sampling and sensor emplacement
techniques.
Task: To decrease cost and improve spatial resolution, develop sensors that can
fit in existing boreholes.
Status: Deployable prototype sensors are small enough that 10 sensors can fit
inside a 2-inch diameter hole.
Status: Cheaper, smaller, and more robust subsurface location devices havebeen developed and are availab le for use.
Status: Prototype field sensors using alternatives to boreholes are being
deployed. These sensors are small enough to support 50 channels of output data
in a sensor that fits in a hole the size of a rice grain.
Status: Injectable sensors and smart sensors are availab le as off-the-shelftechnology. These low-cost sensor technologies provide continuous spectrum
coverage, are the size of a soil pore, and require little maintenance.
Acti vi ties SIE1 and SIE2:
Status: The geology and hydrology of a contaminated site can be characterized
at a 10-meter scale throughout the top 50 meters of the subsurface, using
methods that have about a one-month turnaround time fo r processing andinterpreting the field measurements.
Status: The geology and hydrology of a contaminated site can becharacterized at a 1-meter scale throughout the top 50 meters of thesubsurface, using methods that have about a one-day turnaround time forprocessing and interpreting the field measurements.
Status: The geology and hydrology of a contaminated site can becharacterized at a 1-meter scale throughout the top 50 meters of thesubsurface in real time for most sites.
HIGHLIGHTS OF EXPECTED RESULTS
Prototypes of miniaturized sensors are small enough to fit a package of 10 inside a
two-inch hole.
We can characterize the geology and hydrology of a site at a 10-meter scale with one
month turn-around.
Techniques to minimize emplacement effects have been developed and tested.
Minimally invasive emplacement methods and miniature sensors are available asalternatives to conventional boreholes and instrumentation techniques.
We can characterize the geology and hydrology of a site at 1-meter scale with a one
day turn-around.
Injectable, smart sensors are available off the shelf; non-invasive methods formeasuring key flow and transport properties are available.
We can characterize the geology and hydrology of a site at 1-meter scale in real-time
for most sites.

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A National Roadmap for Vadose Zone Science and Technology#14 Design & Optimization of Measurement Networks
Near Term

M id TermLong Term

M id TermLong Term

Acti vi ty ND1: Develop, test, and apply methods for optimizing VZ sensor networks
to meet end users’ needs for characterization, sitewide assessment, and monitoring
informat ion within user-specified constraints of uncertainty and cost.
Task: Create a nu merical lab, co mb ined with highly instrumented field sites,
for assessing sensor networks and data value. Define nu merical experiments
to assess the value of data
Task: Develop methods to determine the sensitivity of key parameters tosensor network design (and indirectly, cost).
Task: Determine how design and optimization of sensor networks can
reduce uncertainty, taking into account the factors of sensor network cost,
data density, and subsurface depth.
Status: The nu merical lab has been upgraded and can now be combined withfield data to apply methods for network sensor design to field-scale tests andexperiments.
Task: Develop methods to identify controlling parameters.
Status: The geophysical method or comb ination of methods that is most costeffective for characterizing different geological environments or dynamic
processes can be determined.
Status: Sensitivity to network design can be quickly determined for co mp lexwide sites.
Status: Network design and optimization methods are used to convey to end
users the cost, data density, and level of investment needed to reduce
uncertainty to specific levels.
HIGHLIGHTS OF EXPECTED RESULTS
We can access a numerical laboratory linked with instrumented field sites to conduct
experiments on characterization/monitoring network design and data value.
We can use field data in a numerical laboratory to optimize monitoring networks forfield-scale experiments.
We can use network optimization design methods to explain cost-benefit risks andother trade-offs to end users, as part of planning for long-term monitoring and site
assessment activities.
We can quickly determine the location sensitivity and data value for designs ofmonitoring and characterization networks.

#15 Facilities for Integrated Field Experiments
Near Term

Acti vi ty IFE1 : Select, develop, and use national facilities for integrated field
experiments aimed at testing VZ research and technology.
Task: Design and construct IFE support facilities at one or (preferably) moresites representative of priority VZ contamination conditions.
Status: A first series of shorter-term experiments have been completed.
Task: Conduct major, long-term integrated field experiments (designed tocontinue for a decade and longer).
HIGHLIGHTS OF EXPECTED RESULTS
Facilities to support IFEs have been constructed at representative sites.
Results from the first series of short-term IFEs are available.
Results from major, long-term IFEs are supporting and testing long-term research
efforts, improving monitoring systems, and validating integrated assessment models.

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Near Term

Acti vi ty PS E1: Develop and implement a useful first-generation VZ PSE.
Task: Develop the basic PSE structure, including a high-level interface, data
structure storage and retrieval approach, simulation engine, and graphicalback-end, with a co mmon data structure for modeling andcharacterization/ monitoring.
Task: Imp lement a limited set of state-of-the-art nu merical methods for the
first-generation PSE.
Status: A first-generation PSE is imp lemented, functional, and in use.
Acti vi ty PS E2: Extend and update the VZ PSE to provide an increasingly powerful
and integrated software framework for studying and solving problems in VZ
contamination.
Status: Location-specific databases of parameters have been built and populated.
Status: The PSE has matured to provide users with a wide range of models,
including some mu lti-scale, coupled models.
Status: Models for strongly coupled nonlinear GHCB systems are supported
in the VZ PSE.
Status: A co mputational test bed to assist in testing and validating models has
been incorporated into the VZ PSE.
Status: Support for inverse methods and for decision support simu lations has
been added to the VZ PSE.
Status: Geographical in formation systems have been linked with, orotherwise functionally incorporated into, the VZ PSE.
Status: Support for uncertainty analyses has been incorporated into the VZ
PSE.
Status: Support for a wide range of nu merical methods has been incorporated
into the PSE.
Status: The VZ PSE has been implemented on state-of-the-art
supercomputing environments
Status: The VZ PSE is being used routinely by DOE and other agencies forvisualizat ion, analysis, and simu lations in support of characterizat ion,monitoring, site assessment, and remediat ion/stewardship decisions at major
sites of VZ contamination.
Status: Realistic models for all coupled GHCB phenomena, including strongly
coupled nonlinear processes, that are important to VZ flow and transport areavailable in the PSE. These models cover all impo rtant time and space scales.

Status: The VZ PSE supports state-of-the-art numerics, including full spatial
and temporal erro r estimation with automatic grid refinement.
Status: Support for assessing the value of information has been added to the VZ
PSE, including the Shared Vadose Mode
Status: The VZ PSE is broadly accepted and used as a valuable tool to assist all
aspects of the development and application of the science: p rocesses,
characterization and monitoring, simu lation, and predict ion.
HIGHLIGHTS OF EXPECTED RESULTS
We can access a shared PSE (software), which includes a common data structure foruse in characterization, monitoring, and modeling, as well as a limited set ofnumerical modeling tools.
An extended PSE, linked to a geographical information system, incorporates a rangeof numerical methods and provides a computational test bed for validating models.
The vadose zone PSE incorporates realistic models for all coupled GHCB
phenomena and state-of-the-art numerics; it supports ‘value of information’assessment for monitoring and characterization systems.

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A National Roadmap for Vadose Zone Science and Technology#17 Advanced Numerical Algorithms
Near Term

Acti vi ty NM1: Development and applicat ion of better linear and nonlinear solvers to
VZ modeling.
Status: Existing state-of-the-art linear and nonlinear solvers have been
adapted, improved, and applied to VZ problems.
Status: Linear and nonlinear solvers have been improved to match VZ
problems and run in co mputing environ ments, such as the VZ PSE.
Acti vi ty NM2: Imp rove approaches to resolve ext reme spatial g radients in GHCB
properties and processes, such as fingers, sharp fronts, boundaries, and interfaces.
Status: State-of-the-art nu merical methods are being applied to modelingspatial grad ients of fingers, sharp fronts, boundaries, interfaces, and otherextreme-gradient GHCB phenomena.
Status: New and imp roved numerical methods have been developed andapplied for resolving extreme GHCB g radients in both space and time.
Acti vi ty NM3: Develop multi-scale mathematical methods and numerics to capturemean ingful scales of important GHCB phenomena
Status: Mult i-scale mathemat ical methods and numerics are in use formodeling important GHCB processes, including most linearly coupled,
continuous processes.
Status: More sophisticated mult i-scale mathemat ical modeling and numerics
have been developed, targeted to non-continuum and chaotic phenomena.
Acti vi ty NM4: Develop and apply spatial numerical error estimators and adaptive
local (spatial) g rid refinement algorithms.
Status: Nu merical erro rs are being estimated in terms of quantities ofinterest to decision-makers, using spatial nu merical error estimators andadaptive, spatially local, algorith ms for g rid refinement.
Acti vi ty NM5: Develop and apply spatial and temporal error estimators and adaptive
local grid and time step refinement algorith ms for nonreactive systems.
Status: Both spatial and temporal error estimators and grid refinement
algorith ms (for spatial grid and time steps) are being incorporated innonreactive flow-and-transport models.
Status: Spatial and temporal error estimators and adaptive local g rid and time
step refinement have been developed and are being applied fo r react ive
systems in the VZ.
Acti vi ty NM6: Determine criteria fo r acceptable co mputational errors based onmodel uncertainties and incorporate algorith ms for these criteria in VZ simulation
software.
Status: Probabilistic approaches to estimate likely numerical error are available
for use in VZ system modeling, instead of maximu m error. These probability
approaches are being used to estimate mean and variance, as well as othernumerical error measures, in terms of quantities of interest to decision makers.
Status: Estimates of maximu m, mean, variance, and other nu merical error
measures in quantities of interest to decision makers are standard practice inmodeling VZ systems. Modelers use these estimates adaptively to imp rove
simulat ion results.
Acti vi ties NM1 through NM6 :Status: Support for a wide range of nu merical methods has been incorporated
in the VZ PSE.
Status: In models of VZ systems, the numerical methods are selected
automatically and on an appropriate scale, during computation, to reduce
numerical error in decision variables.
HIGHLIGHTS OF EXPECTED RESULTS
Existing state-of-the-art numerical methods have been adapted to address vadosezone problems.
A wide range of numerical methods relevant to vadose zone problems are available.
Site assessment models can automatically select the best numerical method at a
spatial and temporal scale to minimize numerical error in decision variables.

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A National Roadmap for Vadose Zone Science and Technology#18 High-Powered Computing
Near Term

Acti vi ty HPC1: Design, implement, and continue to imp rove an Environ mental
Science High-Po wer Co mputing capability.
Task: Build a user co mmunity; form an organizing co mmittee.
Task: Write the proposal for a mu lti-teraflop (1013 to 1014 Flops) computing
capability, to be associated with the DOE EM Program and/or the Office of
Science.
Status: Proposal for a mult i-teraflop co mputing capability has been submitted
to DOE.
Status: Design of the co mputing capability has been completed, including
its expected future gro wth in size and capability
Task: Purchase and install the co mputing capability at a national laboratory;
hire staff.
Status: HPC capability is in use by VZ researchers on studies of processes,
characterization/ monitoring, and modeling. It is used to study both lab and field
experiments. It is also being used in applied studies for environmental
management sites by DOE and other “problem holders.”
Task: Form a co mmittee and write a proposal for the next generation ofcomputing capability.
Status: The next -generation co mputing capability is designed, purchased, andinstalled.
Status: A next -generation high-power co mputing capability is in co mmonuse for addressing VZ problems.
Acti vi ty HPC2: Bu ild (or t ransfer fro m ASCI and others) infrastructure such as
desktop visualizat ion, archival storage, and parallel input/output interfaces.
Acti vi ty HPC3: Train the user commun ity for the environ mental science h igh-power
computing capability.
Acti vi ty HPC4: Port the VZ PSE to run on the environmental science high-power
computing capability.
HIGHLIGHTS OF EXPECTED RESULTS
A proposal is submitted to DOE and acquisition of the EHPCC begins.
First generation EHPCC is in use.
Second generation EHPCC is in use.

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A National Roadmap for Vadose Zone Science and Technology

APPENDIX C. FULL TEXT OF RESEARCH GOALS AS
GENERATED BY ROADMAP WORKGROUPS
This appendix lists the research goals as formulated by the three work groups shownin Appendix A. After each research goal, in square brackets is listed the Roadmap
Activity in Revision 0.0 to which that goal can be mapped.
Physical Description of Flow and Transport
Near-Term•

Review the state-of-the-practice in DOE for site characterization and remediation,and integrate known models/modules with a sounder physical-chemical basis (stateof-the-science) into DOE flow and transport prediction models and solutions.
[Activity PH5 and near-term status point]•

Identify and assess the importance of fluid flow and chemical transport processes andsubsurface properties relevant to site characterization, remediation and long-term
stewardship (e.g. gravitational, pressure, temperature and chemical gradients).
[Activity PH1 and near-term status point]•

Develop methods to quantify spatial variability in flow and transport parameters, fluid
properties, thermal properties, biological and chemical reactions. [Activity PH4 nearterm status point]•

Develop and implement improved models for evapotranspiration and root water
uptake as a function of water stress and other factors. [Activity PH4 near-term task]•

Develop process-hierarchical approaches for describing and modeling controlling
processes (e.g., models of increased complexity for flow in structured media, orincreasingly sophisticated process-based approximations for gaseous transport or theflow of non-aqueous phase liquids). [Activity PH4 near-term task]

Mid-Term•

Design, implement and analyze controlled laboratory and field experiments todevelop the key databases and understanding needed to resolve knowledge gaps inflow and transport processes operative in granular media. [Activity PH2 and mid-term
task]

•

Develop realistic representations of pore-space geometry of fractured media using
geologic, pedologic, and topologic characterization techniques. In parallel, develop
and implement improved descriptions of matrix-fracture interactions. [Activity PH3
mid-term task]•

Develop general constitutive relationships for both granular and structured media.
[Activity PH3 mid-term task]

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Develop methods for characterizing and propagating physical processes andproperties, and their uncertainties, across different scales (governing equations,driving forces, and/or media properties). [Activity PH4 mid-term status point]•

Develop methods for assimilating data from different scales; identify linkages
between relevant small-scale processes and properties with larger-scale flow andtransport behavior for cases where no simple upscaling is possible. [Activity PH4
mid-term status point]•

Integrate critical elements of chemistry and microbial activity in models for liquidflow and solute transport. [Activity PH5 mid-term task]•

Develop pore network models based upon appropriate equations (e.g. NavierStokes), and devise methods for upscaling processes and/or properties from sample toformation scales. [Activity PH3 mid-term task]

Long-Term•

Develop process- and scale-adaptive models for modeling unsaturated flow andtransport in different types of porous media. Models should invoke processes at theappropriate scale and employ the corresponding transport and hydraulic properties.
[Activity PH4 long-term status point]•

Incorporate solid surface heterogeneity (pore and sample scale), with detailedhydrodynamics into solute transport models (to model opportunity times forreactions, streaming potentials, and other processes or variables). [Activity PH3 longterm status point]•

Incorporate microbiology modules into physical models of solid-gas-liquid
environments. [Activity PH4 long-term status point]•

Incorporate solid surface evolution due to biogeochemical reactions (precipitationdissolution, reduction-oxidation, and other reactions that can change solid-phasegeometry and density of exchange sites) into transport models necessary for longtime-scale simulations. [Activity PH4 long-term status point]

Measuring Physical Processes and Properties
Near-Term•

Improve methods for measuring moisture content, matric potential, and temperature.
[Activity PH6 near-term status point]•

Provide the ability to track a broad waterfront in a 10m X 10m area, at depths up to
100m, to a precision of 10%. [Activity PH7 near-term status point]•

Develop Inverse process of using tracers to estimate fluxes and ages of pore water;
propagation of uncertainties to obtain uncertainties in calculated fluxes and ages
(2004 - 2025). [Activity PH8 long-term task]

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Use of a variety of tracers for locating contaminants; importance of surface boundary
conditions; and point estimates of fluxes and ages (2004 - 2025). [Activity PH8 longterm status point]•

Quantify the relationships among the most likely geophysical methods or
combinations of methods that will provide fracture diagnostics. [Activity PH9 nearterm task]•

Develop automatic data picking and quality control approaches for crosshole
tomographic methods. Also investigate the utility of constrained and joint inversion
for improved estimation, and develop stochastic inversion procedures that yield
distributions of possible geophysical attributes at each location. Develop newparameter estimation inversion techniques for transient flow and transport processes.
[Activity PH11 near-term task]•

Design controlled field experiments distinguishing amongst conceptual models forbetter assessment of vadose zone flow and transport issues by providing amethodology for model testing, a more formal approach to model formulation, and alarger experience base of observing and measuring vadose zone flow and transport
under controlled conditions (2004 - 2025). [Activity IV1 long-term task]•

Develop models of sampling events and instrument response, to be used in improve
instrument design, for a wide variety of invasive and non-invasive characterizationand monitoring methods. [Activity IV1 near-term task]•

Conduct vadose zone field experiments to test and refine models and measurement
techniques. This will include advances in instrumentation, tracers, biologicalproperties, and emplacement technologies as well as mathematical and statisticalbases for design. Scale issues, as relative importance of processes to be included in aconceptual model and parameter identification, are critical for field experiment design(2004 - 2025). Develop new model testing and validation tools. [Activities IV3 andIV2]•Begin to test models by comparing model predictions to short (and eventually longterm) observations (2004 - 2025). [Activity IV3 long-term status point]•

Recognize the importance of scale on characterization measurement and incorporate
measurement support scale in estimates of hydrological properties and correlation
lengths. [Activity PH11 near-term status point]•

Define synthetic test problems and conduct comparative studies of inverse modelingand model validation for these problems. [Activity IV2 near-term task]

Mid-Term•

Resolve a broad waterfront to 5% over a 50m X 50m area. [Activity PH7 mid-term
status point]•

Understand at the mechanism of geophysical energy propagation within un- or
loosely-consolidated, low pressure, granular porous material at the field tomographic
scale, and what are the key influencing factors on the resulting geophysical signature.

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We will understand the sensitivity of different geophysical tomographic methods tovaried geological conditions, and know if multiple geophysical methods are costeffective for certain investigations. [Activity PH10 mid-term status point; Activity
ND1 mid-term status point]•

Provide estimates of hydrologic properties (e.g. water content, permeability andporosity) and their associated uncertainties and spatial correlation functions using
different types of data such as crosshole tomographic. Estimates should be
conditioned to direct measurements, and estimation will be made with attention toscale, using hierarchical spatial scale estimation procedures with multi-scaled data.
[Activity PH11 mid-term status point]•

Understand which geophysical method or combination of methods is most costeffective for characterizing different geological environments or dynamic processes.
[Activity ND1 mid-term status point]•

Learn how to perform joint and constrained inversions that honor all data, understandhow the additional data improves the estimate and decreases the error, and how toincorporate data with different measurement scales in the inversion process correctly.
[Activity PH10 mid-term status point]•

Investigate potential of collecting/inverting multi-scaled data to provide information
about variabilities as a function of scale. [Activity PH4 mid-term task]•

Develop a quick and reliable way to assess the scale of the contamination problem
relative to the scale of the hydrological heterogeneity understanding which techniqueor acquisition parameters are most appropriate for characterization of the key
parameters that control flow and transport. [Activity PH10 mid-term status point]•

Establish methods to incorporate different types of data to assess parameters overdifferent spatial scales. [Activity PH4]•

Attempt to modify the acquisition parameters within a certain type of method tosample different scales of variability and understand how the measurements scalefrom one level of support to another. [Activity PH4 mid-term task]•

Complete integrated meso-scale laboratory and field experiments to provide
databases for specific model testing and validation. [Activity IV2 mid-term status
point]•

Establish a computational test bed as part of the Problem Solving Environment (PSE)
to assist model testing and validation. [Activity IV2 mid-term status point]•

Improve and apply inverse modeling and probabilistic uncertainty estimation methods
to the field and meso-scale laboratory experiments. [Activity IV1 mid-term status
point]•

Link GIS (geographical information systems) to the PSE. [Activity IV2 mid-term
status point]

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Couple uncertainty analysis to management models and PSE to help make decisions
concerning characterization, monitoring, and remediation design and operation.
[Activity UC3 mid-term status point]•

Begin applying model testing and validation methods approaches to DOE sites.
[Activity IV4 mid-term status point]

Long-Term•

Identify a 3D pulse of water (2m X 2m) to an accuracy of about 2% at depths of up to
100m. [Activity PH7 long-term status point]•

Establish rules of thumb for different environments so quick field tests can determine
the category the system under investigation falls into. Utilize the governing
petrophysical relationship for that regime with the geophysical data in the estimation
routine for first-pass estimations. [Cross-cutting long-term status point for Activities
PH10 and PH11]•

Tomographic methods should be able to supply real-time, multi-dimensional(spatially and temporally), automatic interpretations of hydrologic properties orchanges in properties due to bacterial modification, environmental remediation,
infiltration, and other dynamic processes. (The inversion process should be automatic
to provide multi-dimensional, possibly multi-scale, and real-time estimates ofhydrologic properties at high resolution). [Cross-cutting long-term status point for
Activities PH10 and PH11]•

Establish better inverse methods for parameters, and boundary conditions and models,
and their uncertainties. Use as a guide for characterization and monitoring. Test
using synthetic problems, experiments, and site data. [Activity IV4 long-term status
point]•

Understand how to scale between laboratory- and field-based measurements, andincorporate a variety of differently scaled data to provide an integrated andhierarchical interpretation of hydrological properties. [Activity PH10 long-term status
point]•Develop and apply a highly integrated Shared Vadose Model, a subset of the PSE,
where the value of new data is continually assessed as part of an observation–
prediction–decision support (cost analysis) process. [Activity IV1 long-term status
point]•

Models are finally a "bridge" to communicate findings between scientists and policymakers. [Cross-cutting long-term status point for Activities IV1 through IV4]

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Chemical Properties and Processes
Near-Term•

Be able to determine if various contaminants are present in soils from surface orborehole measurements. May need to couple field results with lab analysis to verify
the association. [Activity CH6 near-term status point]•

Be able to delineate in situ burial/disposal configurations (barrels, drums, boxes, andsubsurface structures) to distinguish target contaminants from cultural features andsoils. [Activity MON3, near-term status point]•

Initiate investigations into the effects of dissolution and precipitation on porosity,
pore structure and permeability; initiate studies into nucleation controls that may bias
dissolution and/or precipitation to particular pore environments. [Activity CH4]•

Extend solution chemistry models to higher temperatures and ionic strengths (e.g.,
Pitzer equations) relevant to DOE contamination. [Activity CH1]•

Build conceptual models for attenuation of DOE contaminants on field data of
specific contaminant plumes. At least 2 to 3 conceptual models are expected todescribe the attenuation of particular contaminants. These should becatalogued/updated in the light of ongoing research (2000 - 2005) [Activity MON1
and near-term status point]•

Improve understanding of kinetic rate mechanisms and effective surface areas; use
this understanding to develop improved rate laws. [Activity CH2]•

Determine if significant differences exist for measurement of cation exchange
capacity and surface site density between in-situ field measurements of undisturbed
samples and laboratory batch measurements involving disturbed media. Determine
the validity of using batch Kd measurements to estimate retardation in variably
saturated flowing systems. [Activity CH3 and its near-term task]

Mid-Term•

Field measurements from within and outside the DOE complex should be examined
and compiled to provide broad-based technical support for the portfolio of “fate”
modes. Characteristic transport distances, chemical controls on attenuation, andhydrologic factors will be determined on a site-specific basis but will be usedcollectively to update the conceptual model portfolio. Two parallel efforts: 1.
Cataloguing of contaminant-specific monitoring needs; and 2. Specific identificationof "standard" monitoring approaches that cannot conceivably update or refine the castof conceptual models for the specific contaminant (2005 - 2015). [Activity MON1
and mid-term status point]•

Determine the concentration of the most abundant species within an order ofmagnitude. [Activity CH6 near-term status point]•

Develop a cost-effective real-time monitoring and data analysis system to provide
early warning of contaminant discharges to the vadose zone. [Activity MON3 midterm status point]

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Investigate mineral reactions in contact with a thin liquid film which may havedifferent properties compared to the bulk fluid and mineral reactions in unsaturated
systems having variable gas phase chemistries (e.g., low and high CO2 or O2).
[Activity CH5]•

Develop rate laws for glass dissolution and solid solutions that cover more extended
conditions typical of natural and contaminant-affected flow fields. Improve models
of nucleation processes. [Activity CH4 mid-term endpoint]•

Determine the kinetics (and reversibility) of ion exchange and surface complexation
reactions on mineral surfaces and colloids. Resolve the importance of lack of charge
conservation in surface complexation models when combined with transport, possibly
including streaming potentials in the formulation. [Activity CH3]•

Develop a functional description for porosity/permeability evolution reflecting
chemical effects. [Activity CH4 mid-term endpoint]

Long-Term•

Coordinate a DOE-wide effort to collect long-term monitoring lessons learned. There
should be enough long-term monitoring data gathered to condense the conceptualmodel catalogue and to standardize monitoring approaches and to institutionalize areflexive and iterative linking between monitoring and model refinement (2015 2025). [Activity MON2]•

Isolate contaminated volumes and determine the concentration of abundant chemical
species within 10 or 20 percent. [Activity CH6 long-term status point]•

Quantify the volume and spatial distribution of resident contaminants at or nearsource discharge points, for metals, radionuclides, and organics. [Activity CH6 longterm status point]•

Conduct experimental studies to develop appropriate databases of reaction rate
constants applicable to refined reaction rate laws. [Activity CH2 long-term status
point]•

Couple ion exchange and surface complexation processes to mineral precipitation anddissolution. [Cross-cutting status point for Activities CH1–CH4]

Biological Properties and Processes
Near-Term•

Develop sensors/systems for in situ rate measurements, including improved
bioavailability sensors/assays, sample-to-answer analytical systems for community
composition and activity; spectroscopy- and synchrotron-based inferences of
microbial activity. [Activity B6 and near-term status point]•

Quantify rates of microbial processes affecting inorganics, chelate-inorganic
complexes, inorganic complexes, and organic contaminants, and identify factors
controlling those rates. [Activity B1 near-term task]
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Understand and predict how contaminant bioavailability affects, and is affected by,microbial processes. [Activity B1 near-term task]•

Develop chemically reactive contact foils and films for in situ rates and/or potential
activity. [Activity B6 near-term status point]•

Characterize microbial-mediated corrosion and biodeterioration of materials used tocontain DOE contaminants. [Activity B1 near-term task]•

Develop/apply rapid statistical and classification methods for handling large data sets
generated from the characterization of microbial communities. [Activity B3 near-term
status point]•

Laboratory and modeling of the bio-electric level as a function of different soil types
and microbes. [Activity B7 near-term task]

Mid-Term•

Application of in situ bioavailability sensors; sensors/systems for in situ ratemeasurements and; inexpensive sample-to-answer analytical systems for community
composition and activity. [Activity B7 mid-term task and B5 mid-term task]•

Instrumentation developments to detect lower levels of activity and implement theseat intermediate and field scale validation tests. [Activity B7 mid-term task]•

Characterize and determine factors governing microbial diversity in the vadose zone.
Determine relationships between diversity and community response to contaminants.
[Activity B3 mid-term status point]•

Characterize microbial transport in different natural porous media relevant for DOE
sites, particularly transport through unsaturated fine and coarse sands and fractured
rock, as a function of water saturation and solution chemistry. [Activity B4 mid-term
task]

•

Improve the conceptual and mathematical characterization of interactions between
microorganisms and contaminants (e.g., biodegradation, immobilization,transformation), microbial and physical/chemical processes (coupled processes), andincorporate these equations into reactive transport models. [Activity B1 mid-term
task]

•

Understand how mixtures of contaminants in DOE wastes affect microbial activity
with respect to flow and transport of specific contaminants. Identify conditions when
toxicity of radionuclides, metals, or organics prevents removal of readily degradableorganic contaminants. Predict the rate of biodegradation of particular contaminants
as a function of the type and concentration of other contaminants present. [Activity
B2 all]•Understand the potential roles of siderophore, surfactant, and chelate production by
microbial communities in the vadose zone, including the plant root-microbialcommunity interface, on contaminant transformations. [Activity B3 mid-term task]•

Elucidate pore-scale interactions between microorganisms and contaminants,
including studies at the microscopic level, and at interfaces (solid/liquid, liquid/gas,
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A National Roadmap for Vadose Zone Science and Technology

liquid/liquid, solid/gas, and along textural discontinuities) and in biofilms, under
undisturbed conditions. [Activity B1 mid-term task]•

Determine the importance of microbial attachment/detachment, biofilms andmicrobial associations with colloids with respect to contaminant transport andpreferential flow. [Activity B1 mid-term task]

Long-Term•

Economical analysis of spatial distribution and temporal dynamics. [Cross-cutting
long-term status point for Activities B5-B7]•

Extension of nondestructive joint measurement of biologic, geochemical, physical,
and hydrologic properties or processes to intact cores, and possibly the subsurface.
[Cross-cutting long-term status point for Activities B5-B7]•

Potential development of proxy measurements for microbiological properties andprocesses. [Cross-cutting long-term status point for Activities B5-B7]•

Predict in situ rates of microbial biotransformation of contaminants at DOE sites as afunction of site and environmental conditions. [Activity B4 long-term status point]•

Incorporate information about the composition of vadose zone microbial communities
into pollutant fate and transport models. [Activity B4 long-term status point]•

Predict transport of native and introduced microorganisms at DOE waste sites.
[Activity B4 long-term status point]•

Describe and predict the spatial distribution of microbial biomass, activity, andcommunity composition in the vadose zone with respect to contaminant distribution
and predict how this distribution is affected by water inputs, contaminant fluxes, andduration of exposure to contaminants. [Activity B3 long-term status point]

Colloidal Properties and Processes
Near-Term•

Consider mobile colloids in sampling and analyses protocols in field and monitoringstudies. [Activity COL1]•

Develop new sampling techniques for in-situ measurements of colloidal particles inpore water. [Activity COL1 near-term task]

Mid-Term•

Quantify effect of preferential flow on colloid transport. [Activity COL2 mid-term
task]

•

Understand relevance of colloid-facilitated transport under transient flow conditions,
including wetting-drying and infiltration processes. [Activity COL2 mid-term task]•

Quantify potential for in situ colloid formation and mobilization under conditions
relevant for DOE contamination sites, particularly in presence of extreme chemical
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conditions that can lead to dissolution and precipitation of soil minerals. [Activity
COL2 mid-term task]•

Evaluate specific issues regarding microbial colloids. Research is needed on theeffects of changing contaminant flux, nutrient injection during engineered
bioremediation, and cell to cell communication (quorem sensing) in biofilms andother cell assemblages, on the production and behavior of microbial colloids.
[Activity COL2 mid-term task]•

Characterize colloid-contaminant interactions as a function of solution chemistry andwater saturation (micro- and macroscopic level). [Activity COL2 mid-term task]

Long-Term•

Model colloid transport and colloid-facilitated transport in unsaturated soils,
sediments, and fractured rocks. [Activity COL3 long-term task]•

Characterize colloid transport in different natural porous media relevant for DOE
sites, especially colloidal transport through unsaturated fine and coarse sands andfractured rock, as a function of water saturation and solution chemistry. Colloid
interactions with the solid-liquid as well as the liquid-gas interfaces need to bequantified. [Activity COL2 long-term task]•

Improve conceptual and mathematical characterization of colloid-contaminant-soil
interactions and colloid-facilitated transport and incorporation into reactive transportmodels. [Activity COL3 long-term status point]

Multiphase Flow
Near-Term•

Explore the effects of subsurface heterogeneity (physical, chemical, and biological)
on multiphase flow and transport processes. [Activity MP1 near-term task]•

Develop upscaling procedures for laboratory-derived multiphase constitutive
properties and parameters. [Activity MP1 near-term status point]•

Devise process-based models to describe unstable and preferential flow of aqueousand NAPL phases. [Activity MP1 near-term status point]

Mid-Term•

Measure flow and transport properties of key contaminant mixtures; refine theory andnumerical models describing flow and transport of contaminant mixtures; and design,
implement and analyze controlled tests of complex contaminant mixtures in highly
heterogeneous systems. [Activity MP2]•

Conduct multiphase flow and NAPL transport experiments for representative soils
and contaminants to elucidate real-world problems and data limitations. [Activity
MP1 mid-term task]

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Long-Term•

Refine remediation strategies for site specific contaminant mixtures using numericalmodels to assess uncertainty in flow and transport of complex contaminant mixturesat DOE sites, and to support decisions with regard to remediation and containment
strategies. [Activity MP3]

Chaotic and Unstable Flow
• Review literature related to physical, chemical, and biological processes for which thepresence of chaos was established providing comparative analyses of these processes
and those occurring in the vadose zone; analyze factors leading to flow and chemicaltransport instability and chaos based on a series of bench-scale and field
investigations. Develop criteria to identify the onset of chaos. [Activity UP1 nearterm task]•

Develop a series of models describing phenomena of deterministic chaos in
unsaturated fractured rocks. [Activity UP2 near-term task]•

Identify directions of using chaos theory in vadose zone hydrology. [Activity UP1
near-term task]•

Design and perform field-scale infiltration tests with tracers at several DOE sites withheterogeneous soils and fractured rocks to identify conditions for which chaotic
processes are important. [Activity UP1 mid-term task]•

Develop a new generation of mathematical and numerical models based on theory of
chaotic dynamics to describe unstable, chaotic flow processes in soils and fractured
rocks. [Activity UP2 mid-term task]•

Develop software for the determination of main diagnostic parameters of chaos using
the reconstruction of the system phase-space from scalar data. [Activity UP1 midterm task]•

Implement models of unstable, chaotic flow into other deterministic and stochastic
models used for predicting flow and transport and designing remediation activities.
[Activity UP2 long-term task]

Uncertainty
Near-Term•

Routinely develop petrophysical relationships for different environments, and start tounderstand how multiple data reduces estimation uncertainly and aids with issues of
non-uniqueness between geophysical and hydrological parameters. Become
comfortable using stochastic estimation techniques that provide an estimate of theproperty of interest as well as information about its uncertainty. Develop better
estimation techniques to facilitate routine incorporation of different types of data(geological, hydrological, chemical, and biological) that have different sampling

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scales and different spatial variability. [Activity PH10 near-term task; Activity PH11
near-term status point]•

Assess the state-of-the-art for methods of uncertainty estimation and reduction,
especially for risk analyses. [Activity UC1 near-term status point]•

Prioritize and quantify sources of uncertainty, including choice of conceptual model,
geologic heterogeneity; parameter values; and initial and dynamic boundary
conditions. [Activity UC1 near-term status point]•

Assess uncertainties contributed by geologic heterogeneity in porous media. [Activity
UC1 near-term status point]•

Assess uncertainty contributed by dynamic boundary conditions related to weather
and climate variability and predictability. [Activity UC1 near-term status point]•

Assess uncertainties contributed by characterization and monitoring methods,
including a sample size, sample frequency, etc. [Activity UC1 near-term status point]•

Assess uncertainty contributed by conceptual models of processes, especially overly
simplistic or incorrectly scaled process models, and incorrectly coupled processes.
[Activity UC1 near-term status point]•

Analyze existing long-term geological, hydrological, chemical, and biological records
improving conceptual models and reduce their uncertainties and the uncertainties ofparameter and boundary condition estimates. [Activity UC2 near-term task]•

Improve numerical algorithms to increase efficiency of vadose zone Monte Carlosimulations. [Activity UC3 near-term status point]•

Begin testing uncertainty estimation and reduction methods, and their applications, on
synthetic test problems, small-scale and meso-scale laboratory experiments, and field
scale research sites. [Activity UC2 mid-term task]

Mid-Term•

Establish new theories for describing and understanding the spatial and temporal
structures of naturally occurring heterogeneities and fluctuations. Use advanced
geologic modeling to capture both flow-sensitive and chemical spatial heterogeneity.
[Activity UC1 mid-term task]•

Evaluate uncertainties for flow models of highly heterogeneous porous and fractured
media, affected by the fracture-matrix interactions, dry formations, and film flow; add
more realistic treatment of uncertainties caused by surface boundary conditions.
[Activity UC1 mid-term status point]•

Evaluate effects of uncertainties for invasive and noninvasive field characterizationand monitoring methods with different scales and degrees of resolution. [Activity
UC2 mid-term task]•

Develop new, more sophisticated and efficient probabilistic approaches to uncertainty
estimation and reduction. [Activity UC2 mid-term status point]

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Develop methods to display the degree of uncertainty from different sources and inaggregate (processes, coupling, parameters and properties, variability, etc.). Exploit
advanced visualization techniques and other sensual (e.g., sound and touch)interactions with models and data automatically alerting the user to possible
limitations caused by uncertainty. [Activity UC3 mid-term status point]•

Use uncertainty estimation and reduction methods to predict the value of new data, tooptimize the design and operation of characterization and monitory activities, and toautomatically update a model when new data becomes available. [Activity UC2 midterm status point]•

Implement uncertainty methods at DOE sites to achieve goal of using uncertainty
estimation and reduction methods as standard practice. [Activity UC2 mid-term status
point]•

Link the modeling uncertainty analysis with practical problems of a facility designer;
integrate uncertainty estimation and reduction, with estimation and reduction ofnumerical errors and; link to Problem Solving Environment. [Activity UC3 mid-termtask]Long-Term•

Incorporate uncertainty in biogeochemical models and models of multiphase flow in
fractures (models are in common use). [Cross-cutting long-term status point for
Activities UC1 through UC3 and CP1]•

Develop uncertainty and inverse methods that self-adaptively suggest modified
conceptualizations or parameterizations. [Activity UC2 long-term task]•

Forward and inverse models accounting for uncertainty are fully integrated. [Activity
UC2 long-term status point]•

Uncertainty estimation and reduction is standard practice for characterization,
monitoring, remediation and stewardship decisions. [Cross-cutting long-term status
point for Activities UC1 through UC3]

Scaling
Near-Term•

Scale parameters should be reported as well as measured values and distributions to acomplex-wide database on geological, hydrological, chemical, and biologicalparameters as a function of geological environment. Vadose zone scientists should
also by this time be comfortable interpreting their measured data using a hierarchicalstructure of organization that can exist in natural geological environments. [Activity
PH4 near-term task; Activity G1 near-term status point]•

Begin developing simulation tools that provide a hierarchy of constitutive theories,
simultaneously accommodating multiple processes on different scales. [Activity SC1]

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Complete initial design and development of a Monte Carlo prototype for massive
deterministic simulations of scaling issues. [Activity SC1 near-term status point]•

Use scaling to provide quantification of relevant processes by identification of global
system variants, such as contaminant trajectories and travel-times, non-aqueous
mobile phase geometry’s, cumulative reaction histories over multiple time scales, andsubsurface ecosystem dynamics. [Activity SC1 near-term status point]•

Develop new deterministic and probabilistic/stochastic approaches to address crossscale issues that commonly arise in vadose zone reactive flow and transport. [Activity
SC1 near-term status point]•

Begin research into time scaling of reaction systems and of transient, episodic,
boundary value problems. [Activity SC1 task beginning near-term with long-term
endpoint]

Mid-Term•

Refine computational techniques for solving hierarchically-scaled flow and transportmodels; including testing of these techniques to meso-scale laboratory experiments,
small scale field experiments, or other types of measurements of geological,hydrological, chemical, and biological processes. [Activity SC1 mid-term task]•

Develop scaling methods for flow in generalized (transient and spatially nonuniform)
coordinate systems to accommodate processes that vary on multiple spatiotemporalscales. [Activity SC1 mid-term task]•

Develop extensions of the massively deterministic Monte Carlo method to include
probabilistic specifications of properties and constitutive hypotheses. Use it as atestbed for evaluation of scaling approaches and for advanced quantification of errors
associated with information loss in scaling. [Activity SC1 mid-term task]•

Conduct research to provide a link between constitutive theories and scale ofmeasurement to the quantities of ultimate concern of decision-makers. Link tocharacterization and monitoring. [Activity SC1 mid-term status point]•

Improve scaling algorithms and methods. [Activity SC1]•Begin to develop links to Problem Solving Environment and uncertainty estimation
and reduction methods. [Activity SC1 long-term task]

Long-Term•

Broaden research focus to consider spatiotemporal scaling in support of sourceidentification, (as well as other inverse problems). [Activity SC1 long-term status
point]•

Unify aspects of scaling theory, completely linking to Problem Solving Environment,
uncertainty estimation and reduction methods. [Activity SC1 long-term status point]•

Have capability to model strongly transient geological, hydrological, chemical, andbiological processes over multiple time horizons at applied field sites. [Activity SC1long-term status point]
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Strongly Coupled Systems
Near-Term•

Identify priority coupled process science needs in vadose-zone fate and transport,
review the state of the science in constitutive theory for modeling realisticallycoupled processes, and initiate research on improved representations of coupledprocesses of immediate importance. [Activity CP2 near-term status point]•

Update and check reliability of available databases used in coupled models. Make
databases universally available with recommendations for usage. [Activity CP1 nearterm status point]•

Advance models for coupled systems such as: mechanics of biofilms; multivariate
reaction kinetics; saturation and colloid-facilitated transport; and scaling of coupledprocesses in space and time. [Activities CP2 and CP3]•

Develop model studies to demonstrate ability of existing coupled models andrecommend procedures for usage. [Activity CP2 near-term status point]

Mid-Term•

Develop and incorporate improved constitutive theories and parameter databases into
coupled models; link coupled process models with scaling techniques. [Activity CP3
mid-term status point]•

Mechanical-hydraulic and biochemical-hydraulic prototypes available for use.
[Activity CP3 mid-term status point]•

Test coupled models on synthetic test problems, small-scale and meso-scalelaboratory experiments, and field scale research sites. [Activity CP3 mid-term task]•

Implement support for strongly coupled models within the Problem Solving
Environment. [Activity CP3 mid-term status point]

Long-Term•

Improve computational algorithms for coupled processes. [Activity CP3 long-term
status point]•

Test strongly coupled models in field applications. [Activity CP3 long-term status
point]•

Realistic models are available for all coupled processes important to vadose zone
flow and transport, at all important time and space scales. Most models are available
as part of the Problem Solving Environment. [Cross-cutting long-term status point for
Activities CP1 through CP3]•

Three-dimensional fully coupled heat and multiphase flow and transport models are
the norm for decision support. [Cross-cutting long-term status point for Activities
CP1 through CP3]

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Understanding the Geological, Hydrologic, Chemical, and Biological
Framework•

Tabulate known features for individual sites and start using the geologic/geomorphic
understanding to develop 3-dimensional framework models. [Activity G1 mid-term
task]

•

Develop prototypical numerical models that incorporate the 3-dimensional framework
model with the relevant parameters and processes in place. [Activity G2]•

Use models and all existing data and observations to determine the critical features,parameters and process for the sites. In addition, simulations of flow and transportshould be consistent with all existing data and observations. [Activity G2 long-term
status point]

Sensors and Instrumentation
Near-Term•

Understand the effects of emplacement. [Activity SIE1]•

Demonstrate microdrilling and coiled tubing applied to minimize effects at DOE EM
sites. [Activity SIE1 near-term status point]•

Develop new drilling techniques. [Activity SIE1 near-term status point]•

Deploy prototypes in existing boreholes, decreasing cost and improving spatial
resolution (goal: 10 sensors, fit in < 2” diameter hole). [Activity SIE2 near-term
status point]•

Characterize the geology and hydrology of a contaminated site at the 10m scale
throughout the top 50m of the subsurface using methods that have about a one-monthturnaround time for processing and interpretation of field measurements. [Near-term
status point for both Activities SIE1 and SIE2]

Mid-Term•

Develop minimally invasive methods and begin to correct emplacement effects.
[Activity SIE1 mid-term task]•

Develop cheaper smaller robust subsurface location devices. [Activity SIE2 midterm status point]•

Deploy field prototype using alternatives to boreholes (CPT, new emplacements,
microdrilling, autonomous devices, penetrators, injectable microdevices) (goal: 50
channels, rice grain size hole). [Activity SIE2 mid-term status point]•

Characterize the geology and hydrology of a contaminated site to a resolution of 1mand to improve the turnaround time to 1 day, for many field sites. [Mid-term status
point for both Activities SIE1 and SIE2]•

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Long-Term•

Develop non-invasive methods, or fully correct for emplacement effects; develop
injectable sensors and smart sensors that are off the shelf (goal: continuous spectrum,
size of a pore in soil hole, low maintenance, and low cost). [Activity SIE2 long-term
status point]•

Characterize top 50m of the subsurface to 1m resolution in real time for most sites.
[Long-term status point for both Activities SIE1 and SIE2]

Network Design• Create a numerical laboratory combined with highly instrumented field sites. Define
numerical experiments to assess the value of data. [Activity ND1 near-term task]•

Develop methods to determine sensitivity of parameters. [Activity ND1 near-term
task]

•

Reduction of uncertainty (affected by cost, data density, level). [Activity ND1 nearterm task]•

Upgrade numerical laboratory and combine with field data; apply methods to field
scale tests and experiments; develop methods to identify controlling parameters.
[Activity ND1 mid-term status point]•

Determine sensitivity for complex-wide sites. [Activity ND1 long-term status point]•

Convey to end-users at what cost, data density and level can you reduce uncertainty.
[Activity ND1 long-term status point]

Software: Vadose Zone Problem Solving Environment
Near-Term•

Develop the basic PSE structure, including a high-level interface; data structurestorage and retrieval approach; simulation engine; and graphical back-end; with acommon data structure for modeling and characterization/monitoring. [Activity PSE1
near-term task]•

Implement a limited set of state-of-the-art numerical methods. [Activity PSE1 nearterm task]•

Restrict to structured grids. [Activity PSE1 near-term status point]•

Implement on workstations; for forward simulations; and apply on a limited basis.
[Activity PSE1 near-term status point]

Mid-Term•

Build/populate the parameter and location-specific databases. [Activity PSE2 midterm status point]

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Mature to a wide range of models, including some multi-scale, coupled models.
[Activity PSE2 mid-term status point]•

Add support for inverse methods, for decision support simulations, for uncertainty
analyses, and a wide range of numerical methods. [Activity PSE2 mid-term status
point]•

Port to state of the art super computing environments. [Activity PSE2 mid-term status
point]•

Apply on a routine basis. [Activity PSE2 mid-term status point]

Long-Term•

Add support for the full range of multi-scale, coupled models, for state-of-the-art
numerics, including full spatial and temporal error estimation with automatic gridrefinement, and to assess value of information. [Activity PSE2 mid-term and longterm status points]•

Accept and use as a valuable tool to assist all aspects of the development andapplication of the science: processes, characterization & monitoring, simulation andprediction. [Activity PSE2 long-term status point]

Modern Numerics
Near-Term•

Develop and apply spatial numerical error estimators and adaptive local (spatial) gridrefinement algorithms. [Activity NM4]•

Begin estimating numerical error in terms of quantities of interest to decision-makers.
[Activity NM4 near-term status point]•

Apply state-of-the art approaches to resolve extreme spatial geological, hydrological,
chemical, and biological gradients, such as fingers and sharp fronts, boundaries, andinterfaces. [Activity NM2 near-term status point]•

Adapt, improve and apply state-of-the-art linear and nonlinear solvers. [Activity NM1
near-term status point]

Mid-Term•

Develop and apply spatial and temporal error estimators and adaptive local grid andtime step refinement algorithms for nonreactive systems. [Activity NM5]•

Complete probabilistic analysis of likely numerical error instead of maximum error
and begin estimating mean and variance and other numerical error measures, in termsof quantities of interest to decision-makers. [Activity NM6 mid-term status point]•

Determine criteria for acceptable computational errors based on model uncertainties.
[Activity NM6]

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Improve approaches to resolve extreme spatial and temporal gradients, such as fingers
and moving sharp fronts, boundaries, and interfaces. [Activity NM2 mid-term status
point]•Develop multi-scale mathematical methods and numerics to capture meaningful
scales of important geological, hydrological, chemical, and biological phenomena.
[Activity NM3]•

Improve linear and nonlinear solvers to match vadose zone problems and computing
environments. [Activity NM1 mid-term status point]

Long-Term•

Develop and apply spatial and temporal error estimators and adaptive local grid andtime step refinement for reactive systems. [Activity NM5 mid-term status point]•

Estimating maximum, mean, variance, and other numerical error measures inquantities of interest to decision makers becomes standard practice, and is usedadaptively to improve simulation results. [Activity NM6 long-term status point]•

Continue to improve approaches to resolve extreme spatial and temporal gradients,
such as fingers, and sharp fronts, boundaries, and interfaces. [NM2]•

Develop more sophisticated multi-scale mathematical modeling and numerics,
targeted to non-continuum and chaotic phenomena. [Activity NM3 long-term status
point]•

Numerical methods are selected automatically, on an appropriate scale, to obtain
reduced numerical error in decision variables. [Cross-cutting long-term status point
for NM1 through NM6]•

Continue to develop improved linear and nonlinear solvers. [Activity NM1]

HardwareNear-Term•

Build a user community; form an organizing committee; write the proposal for a
multi-teraflop (1013 to 1014 Flops) computing capability, to be associated with theEnvironmental Management Program and/or with the Office of Science. [Activity
HPC1 near-term task]•

Complete the design of the computing capability, including its expected future growthin size and capability. [Activity HPC1 near-term status point]•

Purchase and install the computing capability at a national laboratory; hire staff;
begin building (or transferring from ASCI and others) infrastructure like desktop
visualization, archival storage, parallel I/O, etc. Begin training the user community.
[Activity HPC1 mid-term task, Activities HPC2 and HPC3]

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Mid-Term•

High power computing capability is used by large variety of vadose zone researchers
on studies of processes, characterization/monitoring, and modeling; is used to study
both laboratory and field experiments; is used in applied studies at DOE
environmental management sites. [Activity HPC1 mid-term status point]•

Extend Problem Solving Environment onto the computing capability hardware.
[Activity HPC4]•

Form a committee and write a proposal for the next generation of computing
capability. Design the machine, purchase and install. [Activity HPC1 mid-term task]

Long-Term•

The next generation computing capability is in common use for vadose zone
problems. [Activity HPC1 long-term status point]

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