Hazardous Materials in the Hydrologic Environment: The Role of Research by the U.S. Geological Survey docx

Thescience and technology carried out in the WRD, though modest in terms ofinvestment, contributes significantly to the national effort by continuallyimparting new understanding about th

Hazardous Materials in

the Hydrologic Environment: The Role

of Research by the U.S Geological Survey

Committee on U.S Geological Survey Water Resources Research

Water Science and Technology Board Commission on Geosciences, Environment, and Resources

NOTICE: The project that is the subject of this report was approved by the Governing Board of the

National Research Council, whose members are drawn from the councils of the National Academy

of Sciences, the National Academy of Engineering, and the Institute of Medicine The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance.

This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sci- ences, the National Academy of Engineering, and the Institute of Medicine.

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of guished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the fed- eral government on scientific and technical matters Dr Bruce Alberts is president of the National Academy of Sciences.

distin-The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers It is autonomous

in its administration and in the selection of its members, sharing with the National Academy of ences the responsibility for advising the federal government The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers Dr Harold Liebowitz is president

Sci-of the National Academy Sci-of Engineering.

The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy mat- ters pertaining to the health of the public The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal govern- ment and, upon its own initiative, to identify issues of medical care, research, and education Dr Kenneth I Shine is president of the Institute of Medicine.

The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of further- ing knowledge and advising the federal government Functioning in accordance with general poli- cies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities The Council is adminis- tered jointly by both Academies and the Institute of Medicine Dr Bruce Alberts and Dr Harold Liebowitz are chairman and vice chairman, respectively, of the National Research Council Support for this project was provided by the U.S Geological Survey under Grant No 1434-93- A-0982.

Copyright 1996 by the National Academy of Sciences All rights reserved.

Copies available from the Water Science and Technology Board, 2101 Constitution Avenue, N.W., Washington, D.C 20418.

Printed in the United States of America

COMMITTEE ON U.S GEOLOGICAL SURVEY WATER

RESOURCES RESEARCH

GEORGE M HORNBERGER, Chairman, University of Virginia, Charlottesville

LISA ALVAREZ-COHEN, University of California, Berkeley

KENNETH R BRADBURY, Wisconsin Geological and Natural HistorySurvey, Madison

CONSTANCE HUNT, World Wildlife Fund, Washington, D.C

DAWN S KABACK, Colorado Center for Environmental Management, DenverDAVID H MOREAU, North Carolina State University, Raleigh

FREDERICK G POHLAND, University of Pittsburgh, Pittsburgh, PennsylvaniaFRANK W SCHWARTZ, The Ohio State University, Columbus

LEONARD SHABMAN, Virginia Polytechnic Institute and State University,Blacksburg

MITCHELL J SMALL, Carnegie Mellon University, Pittsburgh, PennsylvaniaALAN T STONE, The Johns Hopkins University, Baltimore, Maryland

DAVID A WOOLHISER, Colorado State University, Fort Collins

National Research Council Staff

STEPHEN D PARKER, Project Director

ANITA A HALL, Project Assistant

WATER SCIENCE AND TECHNOLOGY BOARD

DAVID L FREYBERG, Chair, Stanford University, Stanford, California BRUCE E RITTMANN, Vice Chair, Northwestern University, Evanston, Illinois

LINDA M ABRIOLA, University of Michigan, Ann Arbor

PATRICK L BREZONIK, Water Resources Research Center, St Paul,Minnesota

JOHN BRISCOE, The World Bank, Washington, D.C

WILLIAM M EICHBAUM, The World Wildlife Fund, Washington, D.C.WILFORD R GARDNER, University of California, Berkeley

THOMAS M HELLMAN, Bristol-Myers Squibb Company, New York, NewYork

CAROL A JOHNSTON, University of Minnesota, Duluth

WILLIAM M LEWIS, JR., University of Colorado, Boulder

JOHN W MORRIS, J.W Morris Ltd., Arlington, Virginia

CAROLYN H OLSEN, Brown and Caldwell, Pleasant Hill, California

CHARLES R O'MELIA, The Johns Hopkins University, Baltimore, MarylandREBECCA T PARKIN, American Public Health Association, Washington, D.C.IGNACIO RODRIGUEZ-ITURBE, Texas A&M University, College StationFRANK W SCHWARTZ, Ohio State University, Columbus

HENRY J VAUX, JR., University of California, Riverside

Staff

STEPHEN D PARKER, Director

SHEILA D DAVID, Senior Staff Officer

CHRIS ELFRING, Senior Staff Officer

GARY D KRAUSS Staff Officer

JACQUELINE MACDONALD Senior Staff Officer

JEANNE AQUILINO Administrative Associate

ETAN GUMERMAN Research Associate

ANGELA F BRUBAKER Research Assistant

ANITA A HALL Administrative Assistant

MARY BETH MORRIS Senior Project Assistant

ELLEN DEGUZMAN Senior Project Assistant

COMMISSION ON GEOSCIENCES, ENVIRONMENT,

JAMES P BRUCE, Canadian Climate Program Board, Ottawa, Canada

WILLIAM L FISHER, University of Texas, Austin

JERRY F FRANKLIN, University of Washington, Seattle

GEORGE M HORNBERGER, University of Virginia, Charlottesville

DEBRA S KNOPMAN, Progressive Foundation, Washington, D.C

PERRY L MCCARTY, Stanford University, Stanford, California

JUDITH E MCDOWELL, Woods Hole Oceanographic Institution,Massachusetts

S GEORGE PHILANDER, Princeton University, Princeton, New JerseyRAYMOND A PRICE, Queen's University at Kingston, Ontario

THOMAS C SCHELLING, University of Maryland, College Park

ELLEN K SILBERGELD, University of Maryland Medical School, BaltimoreSTEVEN M STANLEY, The Johns Hopkins University, Baltimore, MarylandVICTORIA J TSCHINKEL, Landers and Parsons, Tallahassee, Florida

Staff

STEPHEN RATTIEN, Executive Director

STEPHEN D PARKER, Associate Executive Director

MORGAN GOPNIK, Assistant Executive Director

GREGORY SYMMES, Reports Officer

JAMES E MALLORY, Administrative Officer

SANDI FITZPATRICK, Administrative Associate

SUSAN SHERWIN, Project Assistant

This report is a product of the Committee on USGS Water ResourcesResearch, which provides consensus advice to the Water Resources Division(WRD) of the U.S Geological Survey (USGS) on scientific, research, andprogrammatic issues The committee is one of the groups that works under theauspices of the Water Science and Technology Board (WSTB) of the NationalResearch Council The committee considers a variety of topics that areimportant scientifically and programmatically to the USGS and the nation andissues reports when appropriate

This report concerns the WRD science and technology that is relevant tohazardous materials in the soil and water environment, including the subsurface,stream and lake sediments, and surface waters Within the USGS, this work isdispersed in a number of WRD program areas, including basic research,regional and site assessments, and data collection activities

In the United States, a massive effort is in progress to remediate sites atwhich hazardous materials threaten the environment For perspective, it hasbeen estimated that there may be as many as 300,000 sites where soil and/orground water may require remediation to reverse the negative impacts of pastindustrial, military, agricultural, and commercial activity Estimates of the costs

of this effort over the next several decades approach a trillion dollars Thescience and technology carried out in the WRD, though modest in terms ofinvestment, contributes significantly to the national effort by continuallyimparting new understanding about the natural processes relevant to thetransport, fate, and remediation of hazardous substances in the soil and waterenvironments

This report attempts to help shape the overall framework for the agency'sresearch in hazardous materials science and technology, while pointing upgeneral areas of scientific opportunity, including communications andeducation As such, the report does not represent an in-depth review of allgermane WRD programs and projects, but instead is a more general documentintended to provide strategic advice to WRD management.

The committee began its review in late 1993, when most membersparticipated in the regular meeting of the USGS Toxic Substances HydrologyProgram in Colorado Springs, Colorado Subsequently, the committee met fivemore times before completing this report At meetings, members were briefed

by USGS personnel on a variety of programs and toured field sites—such as thecontaminated ground water sites at Otis Air Force Base on Cape Cod, and a site

of mining-related metals transport into the Arkansas River in Leadville,Colorado—to acquire information for review The members wrote individualcontributions and deliberated as a group to achieve consensus on the content ofthis report It is hoped that by maintaining a broad, forward-looking perspective,this assessment will prove useful

As the committee deliberated and became more cognizant of USGSactivities, productive discussions occurred between the members and USGSpersonnel This interaction was critical to success of this project The committee

is particularly grateful to Dr Robert M Hirsch, Chief Hydrologist, Dr Gail E.Mallard, Acting Assistant Chief Hydrologist for Research and ExternalCoordination, and their colleagues for all the information and cooperation theyprovided

It is hoped that this report will help promote the understanding of naturalprocesses relevant to hazardous materials science and technology, and that inturn, this improved understanding will lead to advances in public policy andenvironmental management The work of the USGS in this area is key tomaking progress on one of the most crucial natural resources science policyissues of our time

George M Hornberger

Chair, Committee on USGS

Water Resources Research

2 OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS

MATERIAL REGULATION AND REMEDIATION

8

Comparison of USGS Hydrologic Research to That of Other

Organizations

17

From Process Discovery to Application: The Role of the USGS 20

3 CHARACTERIZATION: PROCESSES AND METHODS FOR

IMPROVING UNDERSTANDING

23

State-of-the-Art in the Field 38

Decision Support in the USGS Hazardous Materials Science

Pro-gram

67

A U.S Geological Survey Water Resources Division Plan for

Haz-ardous Materials Science

Executive Summary

This report focuses on the programs in science and technology of the U.S.Geological Survey's Water Resources Division (WRD) that are relevant tohazardous materials in soil and water In the United States, a massive effort is inprogress to remediate sites at which hazardous materials threaten theenvironment The science and technology programs of the WRD, with aheritage of over 100 years, contribute significantly to the national remediationeffort by continually imparting new and credible understanding about soil andwater contamination This report attempts to help shape the overall framework

of the agency's research in hazardous materials science and technology, andidentifies general areas of scientific opportunity It is not a detailed critique butinstead contains strategic advice to WRD management

The report was developed over a two-year period, during which timeinformation was acquired and assessed and conclusions and recommendationswere formulated with respect to: an overall research framework for the agency'spertinent programs, critical areas of research, educational opportunities,methods to evaluate research success, and approaches to improve coordinationwith others This report reinforces the widely-held viewpoint that addressing thenation's hazardous materials problems is a large and challenging undertakinginvolving many entities in a cooperative fashion Among these entities, theUSGS has important roles to play

From a strategic perspective, the agency must affect a shift in emphasisfrom addressing basic questions in hydrogeological sciences toward solvinggeneric applied problems as congressional attention becomes more orientedtoward practical results and as additional methods

for solving problems become available This will require application of a based approach for setting research priorities to assure that resources aredirected to activities with the greatest potential benefits to public health and theenvironment As part of this risk-based approach, priorities for research and theevaluation of research results must involve input from cooperating agencies andpeer review of planning strategies and research results.

risk-Although relevant activities in the hazardous materials science andtechnology program are dispersed throughout the WRD, this study revealed nocause for significant reorganization Nevertheless, the importance of bothinternal and external coordination and cooperation will likely increase in thefuture in response to strong pressure from Congress to increase productivitythrough interagency cooperation In many cases this cooperation and proactiveoutreach will mean maintaining a keen sensitivity to the needs of those entitieswho are effectively consumers of research and information generated by USGSscientists

The characterization of processes relevant to the transport and fate ofhazardous materials in soils and waters is a significant strength of the USGS.Long-term, field-based studies, for example, have been one of the agency'sgreatest strengths This type of research should continue and be expanded tointegrate methods to evaluate the effectiveness of remediation efforts Such anapproach will require continued dedication to research, together with thedevelopment and implementation of new modeling capabilities and decision-support tools The USGS should lead the effort to perform the long-termassessments that are essential to both technology refinement and informedpolicy decisions

1 Introduction

The U.S Geological Survey (USGS) has addressed problems related to thecontamination of surface waters and ground waters since shortly after itsestablishment by Congress in 1879 As former USGS hydrologist WalterLangbein recounts (1981), the first USGS paper on the quality of waterconcerned the use of sewage for irrigation (Rafter, 1897) Studies on the effects

of waterborne contaminants have continued to be a focus of the USGS,especially its Water Resources Division (WRD), which was formed in 1949.(The 1949 date is deceptively late Forerunners of the WRD, the “IrrigationSurvey”, the “Hydrologic Branch”, and the “Water Resources Branch” datefrom before 1900.)

During the early part of this century, the majority of the related work by the USGS was done under the auspices of the Federal-StateCooperative Program (Langbein, 1981) This program, in which the federalinvestment is matched by a cooperator (typically a state), but in which the work

contaminant-is performed by USGS personnel, addresses a variety of problems of localurgency (e.g., sewage discharges, waste storage, urban runoff, etc.) From themid-1950's to the early 1970's, the research program of the USGS WRDburgeoned (Langbein, 1981) In that era, federal programs within the USGSgrew as did the work done for other federal agencies Subsequent to the 1970s,WRD programs in hazardous materials science and technology have diversifiedand come into their own as the “bread and butter” of the USGS The ToxicSubstances Hydrology Program was established in 1983, the Nuclear WasteHydrology Program was established as a separate program in 1985 (althoughthe WRD has had a significant effort in this area since the early

1960s), and the National Water Quality Assessment (NAWQA) Program wasestablished as a pilot program in 1986 and as a full-scale program in 1991.Langbein (1981) pointed out the increasingly important niche that wasbeing occupied by studies related to water quality within research programs ofthe WRD:

Over the years there has been a considerable change in the subject matter of research due mainly to corresponding changes in the nation's water problems, especially water quality Fortunately, the division began to broaden its research

in the 1960's with research into water chemistry as such, and soon expanded the scope to include geochemical relations During the 1950's nuclear bomb testing and the resulting radioactive fallout, and the environmental movement set in motion in the late 1960's both created a vast explosion of interest in water quality, so that it is now the dominant feature of the division's research and includes not only the physical and chemical properties of water, but the biological and ecological as well.

The USGS focus on developing the geoscience knowledge base that isrequired to address the difficult problems facing the nation regarding the need

to maintain good quality waters can be seen as part of a broad effort by manyfederal, state, and local agencies to come to grips with issues related to thedisposal and inadvertent releases of hazardous materials in the naturalenvironment (In this report, the term “hazardous material” refers to anysubstance that poses a substantial risk to human health or the environment as aresult of contamination of water, air, or soil.) In this sense, several programs ofthe USGS are related to the science and technology of dealing with hazardousmaterials in our society

The role of the USGS in the hazardous materials arena lies squarely in thegeosciences, the traditional strength of the USGS The remediation of sites thathave already been contaminated is a daunting task In addition, the development

of new sites for disposal of wastes, the determination of allowable dischargesinto waterways, and the assessment of the efficacy of remediation efforts mustproceed with the very best

scientific and technical base if the mistakes of the past are to be avoided in thefuture The potential roles for the USGS in addressing these serious nationalproblems draw on the experience that the USGS has developed over manydecades (Figure 1-1).

Recognizing that problems related to hazardous materials research andtechnology are both national and international in scope, and that the USGS is anagency charged with providing information to resolve important water-relatedproblems of the nation, the Committee on USGS Water Resources Researchundertook a review of the research efforts and an assessment of the directionsthe WRD should take in this area In support of the USGS's general objective toexpand the body of scientific knowledge relevant to hazardous materials andtheir behavior in the environment, this project sought to:

(1) help establish an overall framework for the USGS's research plan;(2) identify critical research areas for the coming decade;

(3) advise on educational opportunities in the context of research;(4) provide guidance on processes and measures for evaluating thesuccess of research in this area; and

(5) advise on improved approaches for involving “consumers” of thescience and technology in program planning and theimplementation of results

The committee focused much of its attention on the first two items listedabove With regard to educational opportunities, the general advice to the WRD

in Preparing for the Twenty-First Century: A Report to the USGS Water

Resource Division (National Research Council, 1991) holds in particular for the

hazardous materials programs With regard to measures for evaluating research,the use of peer review is highly recommended By involving “consumers” ofresearch in the peer review, the process would also serve to address item 5.Some of these items will be discussed more fully in the final chapter of thisreport, although the bulk of the technical material in this report will concentrate

on a discussion of a framework for research and the identification of somecritical areas of research

FIGURE 1.1 Potential roles for the USGS in Hazardous Materials Science andTechnology.

The research conducted by the WRD on topics related to hazardousmaterials is spread over many complex WRD programs (as described inAppendix A) This report is not a detailed review of work within these diverseprograms Rather, the report is a general review that seeks to provide overallstrategic perspective It concentrates on four main themes: the understanding ofnatural processes that affect the fate and transport of hazardous substances, theunderstanding of processes that are useful for remediation of contaminatedsites, the use of research results in the decision-making process, and methods toassess the success of the various programs in reaching some of the goals withinthe critical research areas.

2 Overview of the Federal Effort in Hazardous Material Regulation and

Remediation

LEGISLATIVE BACKGROUND

Efforts of the federal government to regulate toxic and hazardous materialsduring the past 40 years have revealed the lack of available knowledgeregarding the extent and severity of hazardous material impacts on humanhealth and the environment It is difficult, for example, to state precisely howmany potentially toxic materials are in use, how many enterprises are involved

in hazardous waste management, the total volume of chemical wastes generated

in the United States each year, and the total number of sites used for hazardouswaste management In addition, very little is known about the toxic effects orenvironmental fate of many chemicals Thus, there are abundant researchchallenges in the area of hazardous materials

The primary role of the USGS in reducing public risks associated withhazardous materials is to provide scientific support, primarily to other agencies

As the nation's leading geoscience agency, the USGS provides analyses of thefate and transport of hazardous substances through natural environments thatare crucial to assessing risks and devising remediation strategies Because theUSGS is a public agency, its main responsibility is to perform research that willassist in addressing issues that are most relevant to the public interest: in thecase of hazardous materials, those issues that pose the greatest risk to humanhealth and the environment

The federal government first became involved in the regulation of toxicand hazardous substances with the 1958 Food Additives Amendment to theFood, Drug, and Cosmetic Act This amendment contained the

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

“Delaney Clause”, which prohibited the addition of a known carcinogen intohuman food.

In 1972, the federal government began to regulate hazardous materials thatare released into the environment with the passage of the Federal Insecticide,Fungicide and Rodenticide Act (FIFRA) This law authorizes the U.S.Environmental Protection Agency (EPA) to register and regulate the sale anddistribution of pesticides in the United States And although FIFRA has limitedsomewhat the use of pesticides, and thus has produced environmental benefits,

it has also resulted in disposal problems, for example, on farms where disposaloptions are limited

The Toxic Substances Control Act (TSCA), enacted in 1976, was alsodesigned to manage releases of hazardous substances into the environment.TSCA gives EPA the authority to restrict the use of substances that are likely topresent an unreasonable risk of injury to human health or to the environment Inthe same year, Congress also authorized the first law regulating hazardouswastes—the Resources Conservation and Recovery Act (RCRA) Although thisact was passed largely in response to the growing public awareness of seriousproblems related to disposal, the RCRA actually regulates the generation andtransport of hazardous wastes

The Clean Water Act of 1977 as a general pollution statute containsmultiple provisions, the most relevant of which pertains to defining EPA'smission in the restoration of the physical, chemical, and biological integrity ofthe nation's waters The act prescribes a list of toxic water pollutants andprovides that they are subject to effluent limitations based on a “best availabletechnology” standard, with EPA having discretion to impose more stringentlimitations based on an “ample margin of safety” standard This act, of course,has its roots in the 1948 Federal Water Pollution Control Act, the initial federallegislation regarding water quality control, which defined the federal roleconcerning water quality monitoring and research

Public concern over hazardous substances increased throughout the late1970s and early 1980s as the Love Canal incident became national news andpolicymakers began to confront the technical complexities of regulating thesesubstances (Barke, 1988) EPA has estimated that U.S industries producedapproximately 290 million tons of hazardous wastes

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

in 1981, and that prior to RCRA, up to 90 percent of hazardous wastes wasdisposed of improperly (Finley and Farber, 1992).

The substantial public concern over hazardous waste disposal sitesclimaxed with the 1980 enactment of the Comprehensive EnvironmentalResponse, Compensation, and Liability Act (CERCLA), commonly known asSuperfund, and the 1986 Superfund Reauthorization and Amendment Act(SARA) CERCLA established an information gathering and analysis system tohelp government agencies characterize and prioritize remediation of hazardouswaste sites; it also provided the federal authority to respond to emergencies andremediate sites The law also created a trust fund to pay for site remediation,and made parties responsible for releases of hazardous substances on lands forwhich they are liable SARA requires that priority be given to remediationmethods that reduce the toxicity, mobility, and volume of waste rather thantrying to contain waste by transferring it to another land disposal facility As aresult of amendments to RCRA and CERCLA, there has been a move awayfrom land disposal of hazardous wastes

In the mid to late 1980s, following the end of the cold war, the nationbegan to recognize the extent of radioactive and other hazardous wastesstockpiled at Department of Defense (DOD) and Department of Energy (DOE)facilities Potential threats to human health and the environment near these sitescome not only from the millions of gallons of wastes that are currently awaitingproper disposal, but also from seriously contaminated soil, ground water andsurface water, and from releases to the air Estimated costs for remediation ofthese sites exceed $100 billion (World Resources Institute, 1993)

The U.S Environmental Protection Agency began to question the highpriority placed on remediation of hazardous waste sites in the late 1980s, as theagency broadened its use of scientific risk assessment In February 1987, theEPA released a report on the relative risk of environmental problems in anattempt to set priorities for its own activities (U.S Environmental ProtectionAgency, 1987) The report concluded that areas related to ground waterconsistently ranked medium or low in terms of the relative risk they pose tohuman health and the environment The report found that active hazardouswaste sites ranked relatively high in cancer risks but relatively low in non-cancer human health risks and ecological effects These sites can also depressproperty

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

values Overall, they were ranked medium in terms of risks to welfare Thereport further concluded that RCRA sites, Superfund sites, underground storagetanks, and municipal non-hazardous waste sites were among areas of high EPAeffort but relatively medium or low risk (Environmental Protection Agency,1990).

Methods for evaluating risks posed by environmental contamination alsobegan to change significantly in the late 1980s Conclusions about the relativerisks to human health and the environment historically have been derived from

in vitro tests of toxic pollutants for acute problems such as skin rashes, eye

sensitivity, and immediate mortality to test species such as fish or algae Cancerrisk also has been evaluated for many chemicals based on laboratory tests.Within the last decade, however, scientists have been accumulating moreinformation regarding chronic effects of toxic pollutants largely from fieldstudies of wildlife and accidental exposures of humans to organohalogens such

as polychlorinated biphenyls, or PCBs (see for example, Colburn et al., 1990).These studies indicate a correlation between toxic pollutants, particularlypersistent, bioaccumulative, organohalogen compounds, and teratogenic effects

in humans and wildlife More recent research has discovered that a number ofsynthetic chemicals, including pesticides, components in plastics anddetergents, and other industrial products and by-products, are capable ofdisrupting the endocrine system Humans and other organisms are exposed tothese substances primarily through air, water, and ingestion

These findings, like much of scientific research, tend to raise morequestions than they answer A substantial amount of public funds is expended

on hazardous material research, regulation, and remediation In an area ofenvironmental management where so much uncertainty continues to exist, it isdifficult, but vitally important, to set priorities for research that will be of mostbenefit to the public interest over the long term by assuring that remedialactions are based on sound science and that regulations are formulated andenforced in an informed manner

THE EVOLUTION OF RESEARCH IN HYDROLOGY

The National Research Council recently described a conceptual model ofthe evolutionary stages of research in hydrogeology (National ResearchCouncil, 1992) Taking a process-oriented viewpoint, the report illus

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

trates how research follows a well-defined pathway that leads from processdiscovery to process description and finally to process application Processdiscovery is concerned with the original characterization of a process and oftenits mathematical formulation Such a discovery may derive from experiments,field studies, or theoretical analyses In most instances, contributions arerequired from all areas.

A case in point is the study of dispersion in porous media The originalstudies on the process of dispersion occurred in the early 1950's with simplecolumn experiments and the development of the theoretical-mathematicaldescription of the component processes The role of dispersion at field scalesremained poorly understood until the late 1970's when appropriate theoreticalstudies combined with subsequent large-scale field experiments were advanced.Thus, process discovery depends upon a complementary collection of researchtechniques involving laboratory, field, and theoretical approaches

After a process is discovered, the thrust of research shifts to processdescription This research expands the knowledge base about processes,detailing how the process works, determining its relative importance to otherprocesses, and establishing values for characteristic parameters of the process.The main investigative approaches involve carefully controlled field andlaboratory experiments, and sensitivity analyses with mathematical models.Returning again to the study of dispersion, examples of research on processdiscovery include the many laboratory experi-experiments designed to establish

“characteristic” values of dispersion lengths for different types of media, andfield studies to quantify correlation structures that give rise to macro-scaledispersion

After a process and its controlling parameters are well understood, it ispossible to utilize this knowledge to solve practical problems through processapplication For example, after discovering the ability of indigenous populations

of microbes to biodegrade some organic contaminants, and describing theconditions under which these processes occur, it is possible to focus on thedevelopment of related remedial methodologies

The conceptual model described above portrays how research in oriented hydrology should proceed, and serves as a basis for this report Theremainder of this report examines the state-of-the-art of research in areas related

process-to hazardous materials science and technology, explains how the USGS ispresently positioned for this research, and

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

explains how the USGS is presently positioned for this research, and describesopportunities for the USGS in addressing critical needs in these areas.

The character of scientific research has changed with time For instance,from relatively humble beginnings in the 1920's, 1930's, and 1940's, hydrologyhas developed into a complex science embodying elements of physics,chemistry, mathematics, and biology The research categorization methodologydeveloped in the previous section can be used as a measure of research progress

in the study of flow and mass transport processes In general, as fundamentalproblems are solved and experience is gained, the research emphasis logicallyshifts to applications For example, such is the case with ground water flowthrough saturated media After over 100 years of research, the continuing focus

in the area of saturated flow is mainly to develop flow codes (e.g., MODFLOW;McDonald and Harbaugh, 1988), or computational enhancements to codes (e.g.,Hill, 1990) The study of coupled flow processes (complex problems where, forexample, mass transport depends upon fluid flow and fluid flow depends uponmass transport), however, remains at the process discovery stage and willrequire extensive research to sort out a large array of complex effects

The emphasis on research related to problems of hazardous waste willalmost certainly shift toward applications What remains to be discussed is whatultimately brings about this shift to applications, and when it is likely to occur

in the various process areas Analysis of these questions should be useful inplanning future USGS research efforts on hazardous materials science andtechnology

OVERVIEW OF RELEVANT USGS PROGRAMS

The WRD of the USGS has a number of programs in which studies areconducted to aid in resolving problems related to the contamination of surfaceand ground waters by hazardous materials (see Appendix A) Funding forprojects related to hazardous materials in various programs within the USGShas reflected priorities established both by the USGS and by Congress(Figure 2.1)

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

FIGURE 2.1 Expenditures on USGS programs related to hazardous materials:Federal-State Cooperative Program, Toxic Substances Hydrology Program,Low-Level Nuclear Waste Hydrology Program, Department of Defense

Environmental Contamination Program

Note: The values for the Federal-State Cooperative Program are estimated by assuming that approximately 14 percent of the total Federal-State budget, the future reported by Gilbert et al (1987) for FY 1986, is devoted to contaminant-related work.

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

Funding for the Federal-State Cooperative Program for projects onhazardous materials has increased fairly substantially, although in terms ofconstant dollars, the funding for the program has been essentially flat Fundingfor the Toxic Substances Program, by the same reasoning, has decreasedslightly in constant dollars Funding for the Nuclear Waste Hydrology Programdeclined to zero in 1994 In addition to programs funded internally by theUSGS, other federal agencies also fund work related to hazardous materials that

is performed by USGS personnel In recent years, work in support ofenvironmental restoration and waste management at Department of Defense(DOD) sites has increased drammatically Over the past eight years, the relativecontribution of the various major programs has shifted somewhat, with anincrease in the percent of the work funded other federal agencies being related

to growth in work related to hazardous materials (Figure 2.2)

Within and across USGS programs related to hazardous materials scienceand technology, there is a spectrum of activities that ranges from pure research

to what may be called service—the problem-solving function of the WaterResources Division within government Separating research from service is not

an easy task Langbein (1981) addressed this question by starting withWebster's definition of research “(1) careful or diligent search (2) studiousinquiry or examination esp having for its aim the discovery of new facts andtheir correct interpretation, the revision of accepted conclusions, theories orlaws, or the practical application of such new or revised conclusions, theories,

or laws.” He pointed out that with a definition as broad as (1), virtually everyprogram of the USGS, including data collection, would constitute “research”

He preferred instead the more narrow definition implied in (2), which heinterpreted to mean new techniques, instruments, and exploration (Langbein,1981)

By this latter definition, research constitutes a relatively small proportion

of the activities of the Water Resources Division Activities related to hazardousmaterials science and technology that concentrate almost exclusively onresearch are found mainly in the Toxic Substances Hydrology Program, whichinvolves researchers in USGS district offices and the national centers Inaddition, core funding for the National Research Program (NRP) contributessignificantly to the overall research effort in hazardous materials science andtechnology There are also

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

FIGURE 2.2 Breakdown of funding by major source of funds: Federal appropriations, state and local government contributions to lthe Federal-State Cooperative Program, and reimbursements from Other Federal Agencies.

Source: Data for FY 1986 from Gilbert et al (1987) Data for FY 1994 from material provided by G Mallard, USGS, Reston, VA.

many projects under the Federal-State Cooperative Program that have asubstantial research component NAWQA, which has a small researchcomponent, also provides opportunities for integration of research from otherUSGS programs within the framework of issues of national concern

In this study, the research and service activities of the USGS have beendifferentiated in order to concentrate primarily on research It is recognized thatthe service functions can and do contribute to research, but a more intensive

focus on the issue of research per se was chosen.

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

COMPARISON OF USGS HYDROLOGIC RESEARCH TO

THAT OF OTHER ORGANIZATIONS

Hazardous material and toxic waste research in the United States isconducted by a variety of organizations including universities, federal and stategovernment agencies, and large and small corporations Historically, the type ofresearch each has conducted has been framed by a variety of factors, such as themission of the organization, history, and circumstance Federal agencies withmissions related to regulating hazardous materials (e.g., EPA) or with extensiveremediation problems at agency sites (e.g., DOD, DOE) have a perspectivetoward research strongly oriented toward short-term results The USGS is one

of the few federal agencies with a more long-term view, having a broadprogram in field-oriented, multidisciplinary research in hazardous materialsscience as related to problems in the natural environment The USGS is knownthroughout the world for its experience in monitoring the natural environmentand for the collection of high-quality, consistent data sets The USGS isparticularly well versed in taking an integrated approach to the study of systemsand for including the important details regarding temporal and spatial variability

in characterizing natural constituents

Universities, by virtue of the discontinuous funding they receive forresearch and the relatively more limited infrastructure, typically restrict theirresearch to aspects of process discovery Much of the work involves computersimulation or laboratory experimentation Field-related hazardous materialremediation studies, when they are undertaken, often require strong supportfrom organizations like the USGS, ARS, or the DOE that have ongoing fieldoperations Some programs have been able to fund field research at high levelsfrom a variety of funding sources, but this is the exception rather than the rule.Programs of the USGS related to hazardous materials science andtechnology are dominated by field studies that have as their goal the discoveryand description of surface and ground water flow and mass transport processes.This focus is understandable, given the historical roots of research within theWater Resources Division, and the distributed character of the organizationwhere many researchers work in district offices The USGS is one of a very feworganizations among all of the

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

groups (universities, other federal agencies, and states) that has the ability toconduct long-term research in field settings.

EPA, DOD, and DOE focus much of their research efforts on applicationsowing to their cleanup responsibilities These agencies have large and activeprograms concerned with developing new remedial strategies for the cleanup ofhazardous and mixed wastes Much of this research has a strong engineering

orientation directly related to waste (ex situ and in situ waste treatment) All

three agencies support fundamental process studies through their largeextramural grant programs and their own laboratories Research anddevelopment work in industry is mainly concerned with the commercialization

of new remedial processes and the development of new measurement processes.The research and development work being performed is tied closely to practice.Interestingly, the focus of research also can be influenced by the nature ofthe reward system For example, excellence in research at the discovery end ofthe spectrum often is “measured” by papers published in high quality scientificjournals that stress innovation in research Relatively little attention is paid towhether the research is “industrially relevant” At the applications end of thespectrum, success is measured by patents, licenses, and commercialization Inmany cases, research is presented in the scientific literature for reasons otherthan to advance science

This discussion raises important questions concerning the future direction

of research related to hazardous materials For example, are there reasons whythe USGS or any of the other organizations should reallocate their activitiesdifferently across the research sub-divisions—discovery, description andapplication? Are there factors that would favor one given research topic overanother?

Clearly, the assessment of what research will be most important in the nextdecade depends upon the selection of rational criteria that might serve toidentify critical research To a large extent, the “consumer” of the researchdetermines the prioritization of research foci or areas Some organizations, likethe National Science Foundation, are responsive to national and internationalneeds and initiate research in critical areas such as “Global Change andContinental Hydrology” and “Math and Science Education” Another largebody of research consumers is represented by industrial hydrogeologists Tothis group, critical research is that with the

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

potential to affect the practice of hydrogeology It is more difficult to supportresearch programs in the area of process discovery and term them as critical.However, programs such as the “solvents in ground water program” at theUniversity of Waterloo, and the “microbial processes program” and the

“passive bioremediation program” developed within the USGS under theleadership of Derek Lovely and Mary Jo Baedecker, respectively, are examples

To date, individual researchers within the hazardous waste programs bearthe major responsibility for determining the direction and focus of futurestudies In many respects, such an approach provides the academic freedom of auniversity researcher with the added benefit of at least some assured funding.This emphasis on curiosity-driven research has served both the USGS andindividuals well in the past It could be argued that political and economicrealities have eclipsed this research model, however The major corporationscited above all have restructured their research programs in fundamental waysthat emphasize corporate needs for research and development For example,although some may lament the passing of the “old” Bell Laboratories as thepremier basic research organization of its kind in the world, AT&T has adapted

to the realities of the market place

The Toxic Substances Hydrology Program has developed and flourished as

a curiosity-driven research program that has capitalized on the particularabilities of the USGS to conduct large-scale interdisciplinary field studies.Nevertheless, there are important ways in which the Toxic Substances Programmust evolve to ensure that the work of the USGS is focused on work of highestimportance to the nation First, more of the work must be made immediatelyrelevant to the major cleanup issues that the country is presently facing atindustrial and defense facilities The report's recommendations in the areas ofremedial technologies provide

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

an overview of how to address this problem Second, complementary laboratoryand modeling studies must be used to support and to generalize fieldinvestigations, which have been the focus of much of the work to date.

FROM PROCESS DISCOVERY TO APPLICATION: THE

ROLE OF THE USGS

As pointed out above, the research programs of the USGS related tohazardous materials are focused on studies of surface and ground water flowand mass transport processes The endpoints for this research—the applications

—are: 1) the analysis of water resources and of sites as to their suitability forwaste disposal; 2) the analysis of contaminated resources and sites to evaluatethe need for cleanup and to determine effective strategies for cleanup; and 3)the provision of unbiased information to guide legislation and governmentalpolicy decisions These are topics of critical concern to the nation Conservativeestimates of the cost of cleaning up contaminated sites in the United States arevery large Considering only ground water and soil remediation, andconsidering only DOE sites, estimated costs over the next three decades areseveral hundreds of billions of dollars (National Research Council, 1994c).When surface waters, wetlands, and sediments are included and attention is notfocused solely on DOE, it is clear that solutions to the problems associated withhazardous materials in the environment are both costly and daunting

Potentially toxic chemicals are now present, at least in trace quantities,essentially everywhere For example, polychlorinated biphenyls (PCBs), DDT,dioxins, hexachlorocyclohexane (HCH), dibenzofurans, chlordane, andtoxaphene have been found in arctic air, surface water, snow, suspendedsediments, fish, marine mammals, seabirds, terrestrial animals and humans(Barrie et al., 1992; Lockhart et al., 1992; Muir et al., 1992; O'Connor et al.,1992; Thomas et al., 1992) The nearly ubiquitous nature of hazardous materialspresents two key challenges to those involved in research on hazardousmaterials in the environment: defining the major problems (with regard to risk

to human health and

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

ecosystem functioning) and determining practical alternatives for alleviating theproblems.

A broad range of problems involving the contamination of water resourcesaffect the United States Surface waters, including streams, rivers, wetlands,lakes, reservoirs, and estuaries, are contaminated with organics, metals,nutrients, and sediments Sources of the contamination range from industrialdischarges to agricultural runoff to direct deposition from the atmosphere.Because many of the contaminants that are released into surface waters partitiononto sediments, there are also significant problems associated with hazardousmaterials in deposits of sediments in waterways and wetland areas A recentNRC report (National Research Council, 1990a) summarizes some of theproblems related to contamination of surface waters and sediments, andprovides recommendations for restoration of these aquatic systems

Ironically, laws passed between 1952 and 1977 to control air and waterpollution caused many industries and municipalities to turn to land disposal forwastes, an action that has contributed to some of the most difficult problems ofground water and soil contamination now faced Estimates of the number ofcontaminated sites in the United States range in the hundreds of thousands, with

a variety of contaminants present in the soils and ground waters Some of theissues related to hazardous substances in ground water are addressed in a recentNRC report (National Research Council, 1994a)

The long-term outlook for environmental cleanup at contaminated sites isnot clear Nor are all of the requisite tools available to determine in a cost-effective manner when natural processes will suffice, i.e., when “passive” or

“intrinsic” remediation will be adequate to protect humans and ecosystems inthe final analysis Moreover, the scientific understanding and methods needed

to assess the appropriateness of a given site as a waste-disposal facility are notall yet available

The strength of the USGS has been in areas of geoscience: in collectingdata that allow assessment of the quality of water, in gaining a fundamentalunderstanding of what natural processes are important in the transport ofcontaminants (including biogeochemical reactions), and in developing modelsthat are useful in analyzing contaminant transport in natural systems Building

on these strengths, the USGS should pursue a strategy in the area of hazardousmaterials science and technology that

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

stresses: 1) improvements in the ability to characterize natural environments interms of the transport of contaminants and of the biogeochemical reactions thataffect these contaminants (i.e., gaining an understanding of the nature ofdifferent environments, including processes that affect contaminants); 2)improvements in methods for remediating contaminated sites (i.e., gaining anunderstanding of the processes and techniques that are useful for containing andfor cleaning up contaminated sites); and 3) improvements in the wayinformation gained from scientific studies can be used to reach decisions aboutappropriate actions in cases where cleanup is likely to be difficult and costly It

is in these areas that the USGS can make important contributions towardsolving the problems associated with remediation of contaminated sites andwith protection of the environment, especially with regard to proposed newwaste-disposal sites Some of these issues are explored in the remainder of thisreport

OVERVIEW OF THE FEDERAL EFFORT IN HAZARDOUS MATERIAL REGULATION AND REMEDIATION

3 Characterization: Processes and Methods

for Improving Understanding

THE NEED

Contamination of the environment (surface and subsurface; waters, soils,sediments, and biota) with hazardous materials has occurred through a variety

of mechanisms induced by humans Sources of contamination are classified as

either point (a single, concentrated, identifiable source) or nonpoint (a diffuse

source) For example, a chemical spill is a point source of contamination,whereas runoff from fertilized farmland is a nonpoint source of contamination.Since the industrial revolution, human activities have served to introduce bothanthropogenic and natural materials to the environment in unnatural ways Forexample, certain mining operations have produced widespread contamination ofsurface waters and stream sediments with elevated levels of metals

A broad spectrum of contaminants have been introduced to theenvironment in a variety of ways, including surface spills, underground pipelineleaks, surface seepage basins, direct releases to streams or lakes, andunderground injection wells Many industrial operations have resulted insubsurface contamination by solvents Many facilities that handled petroleumhydrocarbons (tank farms, refineries, pipelines, and gasoline stations) havecontaminated the subsurface Organic contaminants such as solvents andpetroleum hydrocarbons have migrated rapidly in the subsurface at these sites,often creating large ground water plumes Naturally-occurring toxic substancesthat present human health concerns also have been identified in ground waterand surface water In a number of cases, radioactive materials and trace metalsfrom natural sources have

CHARACTERIZATION: PROCESSES AND METHODS FOR IMPROVING

been found in ground water at levels that exceed public health drinking waterstandards For example, LeGrand (1988) reported elevated activities of radiumand radon in ground waters of the Piedmont Plateau and the Blue RidgeMountains Other toxic substances known to occur naturally at levels exceedingdrinking water standards include arsenic, fluoride, lead, strontium, and selenium(Hem, 1992) The USGS maintains and distributes a data base containingchemical analyses of ground water and surface water for many areas of theUnited States (Hoffman and Buttleman, 1994).

STATE-OF-THE-ART OF CHARACTERIZATION

The characterization of sites containing hazardous materials must involve

an interdisciplinary approach with personnel with expertise in the fields ofhydrology, geology, geochemistry (contaminant distribution), analyticalchemistry, microbiology, ecology, statistics, and image processing Improvedunderstanding of the processes involved in, or affecting, contaminant transport

is critical to developing innovative approaches to characterizing both thesurface and the subsurface, and ultimately preventing future contamination orremediating sites already contaminated According to a previous NRC report

“the greatest progress will be made if site cleanups are accompanied byinvestigations aimed at identifying the critical conditions and processescontrolling contaminant behavior ” (National Research Council, 1994b).Improvements in process understanding and the development of innovativetools for characterization are needed to advance the state of knowledge ofcontaminated sites

In situ remediation represents an attempt to change the physical, chemical,

and biological attributes of natural systems to mitigate the adverse effects of

hazardous materials in the environment In order for in situ remediation to be

successful, the link between particular attributes of natural systems and theprocesses affecting the hazardous constituents must be established clearly

CHARACTERIZATION: PROCESSES AND METHODS FOR IMPROVING

The physical, chemical, and biological attributes of natural systems varyfrom site to site Characterizing these properties is important because theydetermine the response of natural systems to contamination by hazardousmaterials The geology and hydrology define the transport characteristics of thesystem Dissolved anions and cations, mineral surfaces, and natural organicmatter all represent chemical “reagents” that react in distinctive ways withhazardous waste chemicals In addition, distribution of bacteria, plants, andother organisms and their level of metabolic activity are affected by the amount

of organic carbon sources and the nature and amounts of electron acceptorsavailable

In recent years significant advances have been made in the characterization

of the chemical and biological constituents of natural systems and in theunderstanding of how they react with hazardous materials The composition,physical structure, and chemical properties of oxides, clays, and other products

of rock weathering have been extensively characterized (Banfield et al., 1991),and have been examined within the context of prevailing hydrologic andbiogeochemical conditions (Hem and Lind, 1994; Webster and Jones, 1994).Information of this kind is important for establishing the types of mineralsurfaces present in soils and aquifer sediments capable of sorbing pollutant ions(Balistrieri and Chao, 1990; Fuller et al., 1993) For example, iron (II) as acomponent of silicate and other minerals commonly found in most aquifermaterials, has been demonstrated as a strong reducing agent with the capacity toremove many contaminants from the ground water (White, 1990) The efficacy

of the iron (II) reduction process has been demonstrated on chromium (VI) inthe laboratory (Anderson et al., 1994), and several field-based researchers areexamining the efficacy of solids containing both elemental iron and iron (II) as

a reactive barrier to remove organic solvents from ground water (Wilson, 1995).Natural organic matter is an exceedingly complex material thatsignificantly affects fate and transport of pollutants in the environment.Methods have been developed to divide organic matter samples into distinctmolecular size and chemical property fractions (Aiken et al., 1992) Chemicalderivatization and spectroscopic methods have been used to substantiallyimprove understanding of functional groups and

CHARACTERIZATION: PROCESSES AND METHODS FOR IMPROVING

other structures within natural organic matter (Leenheer et al., 1995) Furtherresearch is needed to evaluate sorption of organic pollutants onto soils (Chiou etal., 1983) and to evaluate the role of organic matter in oxidation/reductionreactions, precipitation/dissolution reactions, and complex formation reactionswith naturally-occurring and contaminant-derived metals (McKnight andBencala, 1990).

Bacteria, plants, fungi, and other biological species play an important role

in the transformation of both naturally-occurring and contaminant chemicalswithin the environment Documenting the distribution and metabolic activity ofmicroorganisms, particularly in subsurface environments, is important forevaluating the potential for biodegradation of contaminants (Vroblesky andChapelle, 1994; Chapelle et al., 1995) Much has been learned in recent yearsabout the types and abilities of microbial populations indigenous to thesubsurface (Thiem et al., 1994) The reduction of selenium (Oremland et al.,1994) and uranium (Lovley and Phillips, 1992) by bacteria has been establishedrecently, providing good evidence that microorganisms play a greater role in theredox transformations of inorganic contaminants than was previously suspected

As additional synthetic organic compounds are shown to biodegrade (Visscher

et al., 1994), and as biodegradation in field settings is better understood(Cozzarelli et al., 1994), the need to properly assess the potential forbiodegradation becomes more readily apparent Indeed, a remediation strategyinvolving no additional active measures is being considered for somecontaminated sites where the processes of natural attenuation andbiodegradation are acting to remediate the site This new approach to cleanup ofhazardous waste sites is highly dependent on a good characterization of theenvironment and a sufficient understanding of these processes

Processes

It is important to understand the processes governing natural systems onseveral temporal and spatial scales Pertinent temporal scales are linked to anumber of factors: the rates of chemical and biological process, the transport ofsolutes and sediments in the hydrologic cycle, the ecosystem response, andpossible human disturbance Pertinent

CHARACTERIZATION: PROCESSES AND METHODS FOR IMPROVING

spatial scales range from the molecular (where fundamental chemical andbiological processes take place) through intermediate scales that govern flowthrough porous media and the distribution of microorganisms and invertebrates,

to scales applicable to human activities and whole ecosystems, to the globalscale

Processes such as precipitation/dissolution, adsorption, complexation, anddispersion, and factors such as oxidation/reduction and pH, control themigration of many constituents in the environment A better understanding ofthese processes and controls with a focus on hazardous constituents, willenhance the ability to characterize sites with known contamination and todesign effective remediation systems

Prior environmental research has focused primarily on processes occurring

in a single medium: air, soil, or water Natural environments are open systems,however, and processes acting across media are of fundamental importance Inorder to understand the dynamic behavior of natural systems, aninterdisciplinary approach is required

Significant progress has been made in the last 20 years in understandingthe ecology of subsurface microorganisms and the role they play in the fate andmobility of contaminants Microorganisms have been shown to transformhazardous materials to products that are either harmless or less hazardous, toconvert them to forms with differing solubility, or to sorb them onto cellsurfaces In addition, notable advances have been

CHARACTERIZATION: PROCESSES AND METHODS FOR IMPROVING

made in knowledge of the degradability of numerous hazardous compounds,including the identification of specific degradation pathways Many questionswith respect to biological processes in the subsurface, such as microbialtransport (Hurst, 1991), and the fate and degradability of contaminants, stillremain unanswered, however.

Because contaminants such as gasoline and solvents have entered thesubsurface as separate phases (i.e., not as a dissolved phase in water) it is alsonecessary to understand multiphase flow in the subsurface Most research in thisarea has concentrated on model studies and well-controlled laboratoryinvestigations This theoretical work, originally developed within the petroleumindustry, provides an important theoretical and methodological framework forsubsequent work that has occurred in the field of hydrogeology The problemsare even more complex in the field of contaminant transport because theyinvolve interphase mass transfers Compositional models that incorporateinterphase transfer (Abriola and Pinder, 1985a,b; Baehr and Corapciouglu,1987) have been used as the principal approach to modeling nonaqueous phaseliquid (NAPL) flow True multiphase capabilities incorporating complexpatterns of gas flow and mass removal have been developed to supporttheoretical investigation of remedial approaches such as gas sparging or soilventing Mass transfer between NAPLs and water and between aqueous and gasphases is being studied to improve the knowledge of contaminant migrationthrough the subsurface (Anderson et al, 1992; Miller et al., 1990; Whelan et al.,1994)

There is a deficiency of fundamental field and laboratory data concerningmultiphase flow parameters relevant to contaminant systems Physical modelshave been utilized to improve the state of understanding Mass transferreactions typically encompass families of nuclear, chemical, and biologicalprocesses Although some of these processes like radioactive decay are wellunderstood, those processes involving multiple chemical species and biologicalreactions are much less understood and provide a major focal point ofcontemporary research in contaminant hydrogeology Valid conceptual andmathematical representations exist for many of these processes, but they havenot yet been applied to solving real world problems For example, the use ofoverly simplistic models such as distribution coefficients to describe sorption isnow being re-evaluated in terms of better conceptual and mathematical models(Barber,

CHARACTERIZATION: PROCESSES AND METHODS FOR IMPROVING

1994; Harvey et al., 1989; Harvey and Garabedian, 1991; Stollenwerk, 1991).Other important areas of research include the modeling of complex species insolution (MINTEQ: Felmy et al, 1983; EQ3/EQ6: Wolery, 1979) and theincorporation of inorganic reactions into flow and mass transport models(Cederberg, 1985; Liu and Narasimhan, 1989; Narasimhan et al., 1986).

The diversity and complexity of subsurface systems require anunderstanding of coupled flow processes Coupling of thermal, hydrologic,mechanical, biological, and chemical processes is required to obtain a completeunderstanding of the subsurface Tsang (1987) provided a general overview ofthe commonly studied coupled problems in hydrology The most advancedstudies to date involve codes such as V-TOUGH, developed for the YuccaMountain nuclear waste repository program to predict the response of thehydrologic system to significant repository heating (Buscheck and Nitao, 1992).Other studies have examined density-driven transport of dense hydrocarbonvapors in partially saturated media (Mendoza and Frind, 1990a,b) and thedevelopment of instabilities in variable density flow (Schincariol and Schwartz,1993)

The study of fractured media has been a major focus of a group ofresearchers over the last 30 years New knowledge about how fluids move inthe subsurface through fractured media has been obtained throughadvancements in fracture flow modeling and field experiments For example,the USGS has recently conducted in-depth, multidisciplinary studies of sitecharacterization and ground water movement in fractured rocks at the MirrorLake site in New Hampshire (Hsieh et al., 1993) These studies have broughttogether hydrogeologists, geophysicists, geochemists, structural geologists, andnumerical modelers to address fundamental questions of fluid flow in suchenvironments Theoretical work in this field has continued to progress throughthe development of more realistic fracture flow codes The state-of-the-art indiscrete fracture models is represented by codes such as NAPSAC (UKHarwell) and FracMan/MAFIC (Golder Associates, 1988) Recent work(Sudicky and McLaren, 1992) has extended the discrete modeling approach toaccommodate complex fracture matrix coupling in both flow and contaminanttransport Most field and laboratory studies related to fractured rock problemscontinue to be motivated by the need to assess the implication of fracturing inrelation to waste storage and contaminant transport

CHARACTERIZATION: PROCESSES AND METHODS FOR IMPROVING