United States Office of Emergency and EPA/540/1-89/001 Environmental Protection Remedial Responce March 1989 Agency Washington, DC 20460

Superfund

Risk AssessmentGuidance for SuperfundVolume IIEnvironmentalEvaluation ManualInterim Final

EPA

EPA/540/1-89/001March 1989

Risk AssessmentGuidance for Superfund

Volume IIEnvironmental Evaluation Manual

Interim Final

Office of Emergency and Remedial ResponseU.S. Environmental Protection Agency

Washington, DC 20460

Disclaimer

The policies and procedures set forth here are intended as guidance to Agency and other governmentemployees. They do not constitute rulemaking by the Agency, and may not be relied on to create asubstantive or procedural right enforceable by any other person. The Government may take actionthat is at variance with the policies and procedures in this manual.

ii

Preface

This document is part of a two-manual set entitledRisk Assessment Guidance for Super fund. Onemanual, the Environmental Evaluation Manual,provides guidance for ecological assessment atSuperfund sites; the other, the Human HealthEvaluation Manual, provides guidance for health riskassessment at these sites. Guidance in both areas isneeded so that EPA can meet the requirements ofsections 121 (b) (l) and (d) of the ComprehensiveEnvironmental Response, Compensation, andLiability Act (CERCLA), namely, that selected remedial actions be protective of human health andthe environment. This risk assessment guidance alsocan assist EPA in complying with other CERCLAdirectives. For example, Section 121(c) requiresfuture reviews to ensure that human health and theenvironment continue to be protected at sites wherecontaminants remain after remedial actions werecompleted.

The Risk Assessment Guidance for Superfundmanuals were developed to be used during theRemoval and Remedial Investigation/FeasibilityStudy (RI/FS) processes at Superfund sites. Theanalytical framework and specific methods describedin the manuals, however, may also be applicable toevaluations of hazardous wastes and hazardousmaterials for other purposes. For the RI/FS process,these manuals are companion documents to EPA’sGuidance for Conducting Remedial Investigationsand Feasibility Studies Under CERCLA (October1988), and users should be familiar with thatguidance. The two Superfund risk assessmentmanuals were developed with extensive input fromEPA workgroups composed of both Regional andHeadquarters staff. These manuals are interim finalguidance; final guidance will be issued after therevisions to the National Oil and HazardousSubstances Pollution Contingency Plan (NCP),proposed in December 1988, become final.

Although environmental evaluation and humanhealth evaluation are different processes, they sharecertain information needs and generally will usesome of the same chemical and other data for a site.Planning for both evaluations should begin duringthe scoping stage of the RI/FS, and site sampling and

other data collection activities to support the twoevaluations should be coordinated. An example ofthis type of coordination is the sampling and analysisof fish or other aquatic organisms; if such sampling isdone properly, data can be used in assessing humanhealth risks from ingestion of fish and shellfish andin assessing impacts to, and potential effects on, theaquatic ecosystem.

The two manuals in this set have somewhat differenttarget audiences. The Environmental EvaluationManual primarily addresses Remedial ProjectManagers (RPMs) and On-Scene Coordinators(OSCs), who are responsible for ensuring a thoroughevaluation of potential environmental effects at sites.The Environmental Evaluation Manual is not adetailed “how-to” type of guidance, and it does notprovide “cookbook” approaches for evaluation.Instead, it identifies the kinds of help that RPMs orOSCs are likely to need and where to find that help.Then it describes an overall framework forconsidering environmental effects. A detailed discussion of environmental evaluation methods maybe found in Ecological Assessments of HazardousWaste Sites: A Field and Laboratory ReferenceDocumnet (EPA/600/3-89/013), published by EPA’sOffice of Research and Development. The HumanHealth Evaluation Manual, available in 1989,provides a basic framework for health riskassessment at Superfund sites. The health evaluationmanual is addressed primarily to the individualsactually conducting health risk assessments for sitesand who are frequently contractors to EPA, States, orpotentially responsible parties. It is also targeted toEPA staff, including those responsible for ensuring athorough evaluation of human health risks (i.e.,RPMs). The Human Health Evaluation Manualreplaces a previous EPA guidance document, TheSuperfund Public Health Evaluation Manual, orSPHEM (October 1986), which should be used untilthe Interim Final Human Health Evaluation Manualis available. The new manual incorporates lessonslearned from application of the earlier manual andaddresses a number of issues raised since publicationof the SPHEM.

.iii

Environmental Evaluation ManualEPA Work Group

EPA Headquarters

Office of Emergency and Remedial Response:

Office of Waste Programs Enforcement:

Office of Solid Waste:

Office of Solid Waste and Emergency Response:Office of Air and Radiation:Office of Federal Activities

Office of General Counsel:Office of Information Resource ManagementOffice of Marine and Estuarine Protection:Office of Policy, Planning and Evaluation:

Office of Research and Development:

Office of Toxic Substances:Office of Underground Storage Tanks:Office of Water Enforcement and Permits:Office of Water Regulations and Standards:Office of Wetlands Protection:

David BennettKaren BurganDavid ChartersSteve GolianSandra LeeArthur WeissmanJack SchadSherry SterlingAlec McBrideOssi MeynTom PheifferGary SnodgrassPhillip RossJudy TroastJoseph FreedmanBarbara LamborneBob ZellerDexter HinckleyDiane NiedzialkowskiCraig ZamudaThomas BaughWill LeVeilleSusan NortonJim GilfordIris GoodmanMartha SegallSuzanne MarcyJohn Maxstead

EPA Regional Offices

Region 1:

Region 2:

Region 3:

Region 4:

Region 5:

Dorothy AllenMichael BilgerSusan SvirskyPeter GrevattMark SprengerJeff PikeRon PrestonElmer AkinRUSS ToddPamela BlakelyWayne DavisAllison HiltnerPranas Pranckevicius

Region 6:

Region 7:

Region 8:

Region 9:

Region 10:

EPA Laboratories

Athens, GA: Robert AmbroseCincinnati, OH: Cornelius WeberCorvallis, OR: Hal KibbyDuluth, MN: Nelson ThomasGulf Breeze, FL Hap PritchardLas Vegas, NV: Chuck NaumanNarragansett, RI: Gerald Pesch

Other Agencies

Pat HammackJon RauscherFred ReitmanRobert FenemoreRobert MorbyJay Silvernale

Greg BakerGreg EckertPat CironeWayne GrotheerEvan Hornig

National Oceanic and Atmospheric Administration: Sharon ChristopherisonThor CutlerKen FinkelsteinAlyce Fritz

John McCarthy

Lee Barclay

Peter Escherich

Hart Welsh

Oak Ridge National Laboratory:

U.S. Fish and Wildlife Service:

U.S. Forest Service (Arcata, CA):

vi

Contents

Page

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iiiEnvironmental Evaluation Manual-EPA Work Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vFigures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . i xTables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ixAcknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x

1.

2.

3.

4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 What is Ecological Assessment?

. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 Ecological Assessment in the Superfund Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2l.3 Who Should Read this Manual? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31.4 0rganization of the Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Statutory and Regulatory Basis of Ecological Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.1 CERCLA/SARA Authorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.2 The National Contingency Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.3 RemovalActionGuidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.4 Remedial Investigation and Feasibility Study (RI/FS) Guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.5 CERCLA Compliance with other Environmental Statutes (ARARs) . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Basic Concepts for Ecological Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153.1 0bjects of Study in Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.2 Types of Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.3 Effects of Contaminants on Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

3.3.1 Reduction in Population Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.3.2 Changes in Community Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .213.3.3 Changes in Ecosystem Structme and Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.4 Factors Influencing the Ecological Effects of Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223.4.1 Nature of Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.4.2 Physical/Chemical Characteristics of the Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243.4.3 Biological Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

The Role of Technical Specialists in Ecological Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

1

4.14.24.34.44.54.6

Site Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Site Screening and Identiflcation of Information Gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31Advice on Work Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .31Data Review and Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Advice on Remedial Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Enforcement Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Contents (continued)

Page

5. P1anning an Ecological Assessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355.1

5.2

5.3

5.45.5

5.6

Determination of Need, Objectives, and Level of Effortfor Ecological Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Evaluation of Site Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.2.1 Nature and Extent of Contaminated Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.2.2 Sensitive Environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Contaminant Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375.3.1 Identification and Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 375.3.2 Biological and Environmental Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385.3.3 Toxicity of Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385.3.4 Potential ARARs and Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Potential for Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 40Selection of Assessment and Measurement Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415.5.1 Ecological Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425.5.2 Evaluation of Potentially Affected Habitats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . 435.5.3 Evaluation of Potentially Affected Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . 44Sampling and Analysis Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455.6.1 Field Sampling Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . 455.6.2 Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

6. Organization and Presentation of an Ecological Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496.1 Specify the Objectives of the Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496.2 Define the Scope of the Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 96.3 Describe the Site and Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 96.4 Describe Contaminants of Concern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .506.5 Characterize Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506.6 Characterize Risk or Threat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526.7 Describe the Derivation of Remediation Criteria

or Other Uses of Quantitative Risk Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566.8 Describe Conclusions and Limitations of Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

. .viii

Page

1.2

6.1

1.1

3.13.2a3.2b3.3

6.26.36.4a6.4b6.56.6

Relationship between health and environmental evaluations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Logical organization of this manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Levels of organization of matter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Examples of typical food chains, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17A greatly simplified terrestrial food web . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Thermal stratification of a north temperate lake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Example of study area map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51Graphic display of contaminant concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Map display of contaminant concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Map display of toxicity test results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Map display of toxicity test results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 55Graphic Display of Species Diversity Indices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Graphic Display of Trophic Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 57

5

1.1 Additional EPA Documents to be Consulted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.1 Forest Food Chain for DDT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276.1 Example of Presentation of Criteria Exceedences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

ix

Acknowledgments

This manual was prepared by The Cadmus Group, Inc., for the U.S. Environmental ProtectionAgency, Office of Solid Waste and Emergency Response through Contract No. 68-03-3348. ProjectDirectors and principal authors were Michael J. Dover (Cadmus), Patricia Mundy (EPA) and JohnBascietto (EPA).

Many individuals contributed to this document. We especially wish to acknowledge the assistanceprovided by Dr. James Gillett of Cornell University, who served as a review consultant to Cadmusand offered many valuable comments that were incorporated into this version of the manual.Other Cadmus contributors include Dr. David Burmaster (consultant to Cadmus), Beverly BrownCadorette, Scott T. Campbell, Gene E. Fax, Joseph P. Foran, Kenneth W. Mayo, and Theodore R.Schwartz.

This manual is the product of an extensive planning and review process within EPA. The EPAWork Group, which also included representatives from the National Oceanic and AtmosphericAdministration (NOAA) and the U.S. Fish and Wildlife Service (USFWS), conferred several timesto discuss the organization, content, and policy implications of the document. The Work Groupmembers reviewed and provided extensive comments on each of several drafts of the manual. Inthe early stages of the project, members of the Region 111 Bioassessment Work Group - Dr. DavidCharters (EPA Environmental Response Team), Dr. Alyce Fritz (NOAA, Region III), and RonaldPreston (Environmental Services Division, EPA Region III) - provided invaluable planningassistance.

The authors were privileged to have as a reference a draft version of a manual prepared by theEcological Risk Assessment Subcommittee of the EPA Region I Risk Assessment Work Group. Thedocument, entitled Guidance for Ecological Risk Assessments, was issued as a Draft Final inFebruary 1989. Concepts and some wording of the Region I document were adapted for use inseveral parts of this manual. We gratefully acknowledge the Subcommittee’s cooperation (inparticular, Susan Norton of the Office of Health and Environmental Assessment) in making theirdraft available to us.

Chapter 1Introduction

This manual is intended to help Remedial ProjectManagers (RPMs) and On Scene Coordinators (OSCs)manage environmental evaluation of Superfundsites. Environmental evaluation is an important partof the Remedial and Removal processes. Since RPMsand OSCs have primary responsibility for managingthese processes, it is important for them to under-stand basic ecological concepts and how they relate tohazardous waste remediation.

Environmental evaluation at Superfund sites shouldprovide decision makers with information on threatsto the natural environment associated withcontaminants or with actions designed to remediatethe site. Decisions such as those made on Superfundsites are necessarily made with varying degrees ofuncertainty. The environmental evaluation isintended to reduce the inevitable uncertaintyassociated with understanding the environmental ef-fects of a site and its remediation, and to give specficboundaries to that uncertainty. However, it is important to recognize that environmentalevaluations are not research projects they arenot intended to provide absolute proof of dam-age, nor are they designed to answer long-termresearch needs. Not all sites will requireenvironmental evaluations. Indeed, many are in in-dustrial areas with little if any wildlife. For thosesites that do need to be evaluated, the RPM or OSC isresponsible for determining the level of effortappropriate to the decisions required for each site.

The purpose of this document is to provide a scientificframework for designing studies, at the appropriatelevel of effort, that will evaluate pertinent ecologicalaspects of a site for the Remedial and Removalprocesses. These ecological aspects include:

- Living resources at or near the site requiringprotection,

- Effects of the site’s contaminants on thoseresources, and

- Effects of remedial actions.

This manual does not offer detailed descriptions ofspecific field or laboratory methods; these are

discussed in a companion publication prepared byEPA’s Office of Research and Development,Ecological Assessments of Hazardous Waste Sites: AField and Laboratory Reference Document. TheSuperfund Exposure Assessment Manual describesmethods for estimating and modeling the fate andtransport of contaminants in the environment. Otherinformation that should be used to supplement thismanual may be found in these and the other publica-tions listed in Table 1.1.

The manual is based on the assumption that RPMsand OSCs will obtain assistance from technicalspecialists as early as possible in the assessmentprocess, and is designed to facilitate communicationbetween the RPM or OSC and these specialists.Support for designing and evaluating ecologicalassessments is available from technical assistancegroups in those EPA Regions that have formed them.In other Regions, ecologists may be found on the staffs of other EPA offices and contractors, or on thestaffs of other Federal agencies. The role of thesespecialists is discussed in greater detail in Chapter 4.

1.1 What is Ecological Assessment?Although “environmental evaluation” has been acommonly used term for this process, ecologicalassessment is a more precise description of theactivity, and will be used throughout this manual.

Ecological assessment, as discussed in this manual, isa qualitative and/or quantitative appraisal of theactual or potential effects of a hazardous wastesite on plants and animals other than people anddomesticated species. It is important to emphasize,however, that the health of people and domesticatedspecies is inextricably linked to the quality of theenvironment shared with other species. Informationfrom ecological studies may point to new or unexpected exposure pathways for human popula-tions, and health assessments may help to identifyenvironmental threats.

1

Table 1.1 Additional EPA Documents to be Consulted

Title Source Reference No.

Superfund Exposure Assessment Manual (1988) Office of Solid Waste and Emergency Response

Ecological Assessments of Hazardous Waste Sites A Field Office of Research and Development -and Laboratory Reference Document (1989) Corvallis Environmental Research Laboratory

Ecological Information Resources Directory (1989) Office of Information Resource Management

User’s Guide to the Contract Laboratory Program (1989) Office of Emergency and Remedial Response

Estimating Toxicity of Industrial Chemicals to Aquatic Office of Toxic SubstancesOrganisms Using Structure Activity Relationships (1988)

CERCLA Compliance with Other Laws Manual (1988) Office of Solid Waste and Emergency Response

Guidance for Conducting Remedial Investigations and Office of Solid Waste and Emergency ResponseFeasibility Studies under CERCLA (Interim Final, 1988)

EPA/540/1-88/001

EPA/600/3-89/013

In Preparation

OSWER Dir. 9240.0-1

EPA/560/6-88/001

EPA/540/6-89/006

EPA/540/6-89/004

1.2 Ecological Assessment in theSuperfund Process

The Comprehensive Environmental Response,Compensation and Liability Act (CERCLA), asamended by the Superfund Amendments andReauthorization Act of 1986 (SARA), calls upon EPAto protect human health and the environment withrespect to releases or potential releases of con-taminants from abandoned hazardous waste sites.The proposed revision of the National ContingencyPlan (NCP) calls for identification and mitigation ofthe environmental impacts of these sites and theselection of remedial actions that are “protective ofenvironmental organisms and ecosystems.” In addi-tion, numerous Federal and State laws and regulations concerning environmental protection arepotentially "applicable or relevant and appropriaterequirements" (ARARs). Compliance with these lawsand regulations may require evaluation of a site’secological effects and the measures needed to miti-gate those effects. The specific legislative and othermandates for ecological assessment are discussed inChapter 2 of this manual.

Ecological assessment may take place before, duringand after removal and remedial actions. Removalactions, directed by the OSC, are generally taken inresponse to an immediate hazard. When anemergency response is under consideration, theecological assessment associated with removalactions must be performed quickly. Existinginformation, augmented by any field data that can becollected in a short period of time, will be used to:

- Decide if removal is necessary based on ecologicalconsiderations,

- Predict the ecological effects of removal actions,and

- Provide preliminary information to support aRemedial Investigation if one is needed.

Ecological data should also be gathered before andduring remedial action, under the direction of theRPM. These data will be used to:

Determine the appropriate level of detail for theecological assessment,

Decide if remedial action is necessary based onecological considerations,

Evaluate the potential ecological effects of theremedial action itself,

Provide information necessary for mitigation ofthe threat, and

Design monitoring strategies for assessing theprogress and effectiveness of remediation.

A detailed assessment may be required to determinewhether or not the potential ecological effects of thecontaminants at a site warrant remedial action.Although human health is frequently the majorconcern, the ecological assessment may serve to ex-pand the scope of the investigation, enlarging thearea under consideration, or redefining remediationcriteria, or both. Therefore, when appropriate, theScope of Work for the Remedial Inves-tigation /Feasibility Study (RI/FS) should be writtento incorporate ecological investigations as early aspossible in the process.

The RPM also evaluates the alternatives outlined inthe RI/FS to determine whether the proposedremedial action itself will have any deleteriousenvironmental effects. For example, if dredging isincluded as part of a remedial alternative, the effectsof the dredging on aquatic organisms living on or inthe sediments will very likely need to be considered.If a remediation plan proposes channeling a streaminto a new drainage area, the downstream effects onwetlands may require investigation.

Finally, ecological assessment may suggeststrategies for monitoring the progress andeffectiveness of remediation at or near a site. Forexample, toxicity tests of soils, sediments, and waterhave been used to supplement chemical residue datain establishing cleanup criteria. On-site toxicity testsmay be more sensitive to low levels of contaminantsthan other monitoring methods, and may indicatetoxicity of mixtures of contaminants more readilythan single-chemical criteria.

Environmental evaluation and human healthevaluation are parallel activities in the evaluation ofhazardous waste sites. As Figure 1.1 illustrates,much of the data and analyses relating to the nature,fate, and transport of a site’s contaminants will beused for both evaluations. At each point of thesecommon stages, however, analysts should besensitive to the possibility that certain contaminantsand exposure pathways may be more important forthe environmental evaluation than for the healthevaluation, or vice versa. It is also important torecognize that each of the two evaluations cansometimes make use of the other’s information. Forexample, the potential of a contaminant tobioaccumulate may be estimated for a healthevaluation but be useful for the environmentalevaluation. Similarly, measurement of contaminantlevels in sport and commercial species for an environ-mental evaluation may yield useful information forthe health evaluation.

1.3 Who Should Read this Manual?This manual is designed for use by Remedial ProjectManagers and On Scene Coordinators. The followingmay also find the manual useful for understandingthe ecological assessment process as it relates toSuperfund sites:

EPA Regional Office managers of RPMs orO S C s ,

State hazardous waste officials who wish toundertake ecological assessments of theiro w n ,

EPA contractors and others who may performecological assessments,

Ecologists who have no past experience withSuperfund ecological assessments, and

Potentially responsible parties (if they areperforming the work at the site).

1.4 Organization of the ManualThis manual is intended to address thequestions:

following

How does ecological assessment help EPAmeet its statutory responsibilities?

What is the underlying scientific basis for ecological assessment?

How should the RPM or OSC use technical specialists in managing ecologicalassessments?

What kinds of data are necessary for ecological assessments?

The chapters following this introduction are

- Chapter 2:

- Chapter 3:

- Chapter 4:

- Chapter 5:

- Chapter 6:

Statutory and Regulatorv Basisof Ecological Assessment,

Basic Concepts for EcologicalAssessment,

The Role of Technical Specialistsin Ecological Assessment,

Planning an Ecological Assess-ment, and

Organization and Presentation ofan Ecological Assessment

As Figure 1.2 illustrates, Chapters 2 through 4provide introductions to different aspects of theecological assessment process. Chapters 5 and 6 thenprovide more specific guidance on the informationneeded in an ecological assessment.

Chapter 2 describes the authority provided byCERCLA (as amended by SARA), requirementscontained in the National Contingency Plan, andreferences to ecological assessment in the RI/FS andRemoval Guidances. The chapter also discussesFederal standards, requirements, criteria, orlimitations that are potential ARARs.

Chapter 3 describes the basic scientific conceptsunderlying ecological assessment. It is intended toassist the RPM or OSC in working with the ecologistswho will provide technical advice or perform thestudies, by describing the conceptual frameworkwithin which these specialists make their judgments.This chapter defines numerous terms that are usedlater in the manual. Readers who are familiar withthe concepts and terminology of ecology andenvironmental chemistry may choose to skim thischapter or skip it entirely.

Chapter 4 details the role of technical specialists inecological assessment. Their primary function is toassist the RPM and the OSC in directing thecollection and evaluation of information on ecologicaleffects. They may serve as advisers or may actually

3

perform the ecological assessment under the direc-tion of the RPM or the OSC.

Chapter 5 discusses the process of developing anappropriate study design for assessment of a site,including evaluation of contaminants of concern, sitecharacteristics, and ecological assessment endpoints.In addition to specifying study objectives, this phasemust also address quality assurance and quality con-trol (QA/QC) issues associated with the assessment.

Chapter 6 describes a basic outline for an as-sessment. Although each site’s assessment will differ

according to the details of the contaminants,exposure routes, potentially affected habitats, andspecies, this chapter provides a checklist of items forthe RPM or OSC to expect when overseeing thepreparation of an assessment. For any individualsite, expansion of the topics here maybe needed, withappropriate explanations.

This manual is an introduction to a complex subject.Assessment of an actual site requires a detailedknowledge of the habitats and species that arepotentially exposed, the activity and movement ofcontaminants in the environment, and the sampling

4

and analytical methods needed to make scientificallydefensible judgments. Use of this manual willprovide a basis for the successful management ofsuch assessments.

Figure 1.2 Logical Organization of this manual.

5

Chapter 2

Statutory and Regulatory Basis of Ecological Assessment

Ecological assessment of hazardous waste sites is anessential element in determining overall risk andprotecting public health, welfare, and theenvironment. The Agency considers ecological factorsin assessing hazards and in reviewing alternativeremedial actions because:

Through the authority found in CERCLA (asamended by SARA) and other statutes, theAgency seeks to protect wildlife, fisheries,endangered and threatened species, and valuedhabitats.

From a scientific viewpoint, the Agency needs toexamine ecological effects and routes of exposureso that (a) important impacts and transportpathways are not overlooked, and (b) reasonableestimates are made of health and environmentaleffects.

This chapter describes the statutory and regulatoryframework underlying ecological assessment.Certain provisions of CERCLA and SARA areespecially important in this regard:

The statutes require that remedial actionsselected for a site be sufficient to protect humanhealth and the environment.

Compliance with applicable or relevant andappropriate requirements (ARARs) entailsconsideration of numerous Federal and Statelaws and regulations concerning natural resourcepreservation and protection when evaluatingpossible response actions.

SARA calls upon EPA to notify Federal naturalresource trustees of negotiations with potentiallyresponsible parties and to encourage trustees’participation in the negotiations if a release orthreatened release may result in damages toprotected natural resources.

The chapter begins with a discussion of the authorityprovided in the amended CERCLA for conductingecological assessments. Section 2.2 describes theimplementation of CERCLA as outlined in theproposed revisions to the National Contingency Plan.

Guidance documents for removal actions and theRI/FS process are discussed in Sections 2.3 and 2.4,respectively. A wide array of potential ARARs is thesubject of Section 2.5. It is important to note,however, that this section is not intended to be anexhaustive survey of potential ARARs; the RPM orOSC will need to ascertain the specific Federal andState requirements that apply to each site, dependingon the contaminants of concern and thecharacteristics of the site.

2.1 CERCLA/SARA AuthoritiesThe Comprehensive Environmental Response,Compensation and Liability Act, as amended by theSuperfund Amendments and Reauthorization Act of1986, requires EPA to ensure the protection of theenvironment in (1) selection of remedial alternativesand (2) assessment of the degree of cleanupnecessary. Several sections of CERCLA makereference to protection of health and the environmentas parts of a whole. Section 105(a)(2) calls formethods to evaluate and remedy “any releases orthreats of releases. . . which pose substantial dangerto the public health or the environment.” Section121(b)(l) requires selection of remedial actions thatare “protective of human health and theenvironment. ” Section 121(c) calls for “assurancethat human health and the environment continue tobe protected.” And Section 121(d) directs EPA toattain a degree of cleanup “which assures protectionof human health and the environment.”

CERCLA Section 104(b)(2) calls upon EPA to notifythe appropriate Federal and State natural resourcetrustees promptly about potential dangers toprotected resources. The Federal natural resourcetrustees include:

The U.S. Fish and Wildlife Service (USFWS), theNational Park Service (NPS), and the Bureau ofLand Management (BLM) of the Department ofthe Interior;

The National Oceanic and AtmosphericAdministration (NOAA) of the U.S. Departmentof Commerce; and

7

- The U.S. Department of Agriculture ForestService.

State agencies and Indian tribes are also designatedtrustees for natural resources under theirjurisdiction. Section 122(j) of the amended CERCLArequires the Agency to notify the Federal naturalresource trustees of any negotiations regarding therelease of hazardous substances that may haveresulted in natural resource damage. Section122 (j)(l) also calls upon EPA to encourage Federalna tu ra l r e source t rus t ees to pa r t i c ipa te innegotiations with potentially responsible parties(PRPs). If EPA seeks to settle with a PRP by signinga covenant not to sue, the Federal natural resourcetrustee must agree to this covenant in writing.Section 122(j) (2) states that:

The Federal natural resource trustee may agreeto such a covenant if the potentially responsibleparty agrees to undertake appropriate actionsnecessary to protect and restore the naturalresources damaged by such release or threatenedrelease of hazardous substances.

The ecological assessment directed by the OSC orRPM should not be confused with the PreliminaryNatural Resource Survey (PNRS) or the NaturalResource Damage Assessment (NRDA), whichare performed by natural resource trustees. PNRSsare simple screening studies, based on readilyavailable information, that may be conducted bytrustees to determine whether or not (a) trusteeresources may have been affected, and (b) furtherattention to trustee resources is warranted at aparticular site. The NRDA may be conducted by oneor more trustees if a response action will notsufficiently restore or protect natural resourcesdamaged by a release. The purpose of the NRDA is todetermine the appropriate level of compensation froma responsible party. Data collected in an ecologicalassessment may prove helpful to the trustees incarrying out their responsibilities. It is important toencourage the natural resource trustee to participatein the Superfund process at the earliest possiblestage. In this way, the trustee can be assured thatany potential environmental concerns are addressed,and conclusion of actions may be expedited.

2.2 The National Contingency PlanAs required by SARA Section 105, EPA has revisedthe National Contingency Plan (NCP) l, whichprovides for effective response to discharges of oil and

1 USEPA, National Oil and Hazardous Substances PollutionContingency Plan 40 CFR Part 300. EPA Proposed Revisions tothe NCP at 53 Fed. Reg. 51395 (Proposed Rule, December 21,1988). All references to the “proposed NCP” in this manual are tothis proposed rule. Quotations from the NCP used in this sectionare from the Preamble.

releases of hazardous substances. Section 300.120 ofthe proposed NCP charges the site-specific OSC orRPM with (1) identifying potential impacts on publichealth, welfare, and the environment, and (2) settingpriorities for this protection.

Like CERCLA, the proposed NCP refers throughoutto health and environment as aspects of theevaluation and remediation processes. For example,in discussing the baseline risk assessment in aRemedial Investigation, the purpose is defined asdetermining "whether the site poses a current orpotential risk to human health and the environmentin the absence of any remedial action." The exposureassessment in the RI "is conducted to identify themagnitude of actual or potential human orenvironmental exposures . . ." The toxici tyassessment "considers. . . the types of adverse healthor environmental effects associated with chemicalexposures." In addition, the proposed NCP states that“Superfund remedies will . . . be protective ofenvironmental organisms and ecosystems.”

Sections 300.175 and 300.180 of the proposed NCPdirect the RPM or OSC to coordinate with otherFederal and State agencies. USFWS and NOAA arespecifically cited with respect to endangered orthreatened species. Under Section 300.430, the RPMor OSC is to notify affected land managementagencies and natural resource trustees regarding anyrelease or discharge that affects natural resourcesunder their jurisdiction. According to the proposedNCP, “when trustees are notified of or discoverpossible damage to natural resources, they mayconduct a preliminary survey of the area todetermine if natural resources under their trust areaffected.” The document adds an important proviso:

Although a trustee may be responsible for certainnatural resources affected or potentially affectedby a release, it is important that only one person(i.e., the lead agency OSC or RPM) manageactivities at the site of a release or potentialrelease. The OSC or RPM shall coordinateresponsibilities for CERCLA section 104assessments, investigations, and planning,including Federal trustees’ participation innegotiations with PRPs as provided in CERCLAsection 122(j)(l). Close communication andcoordination between OSCs/RPMs and trustees isessential.

If, after the remedial action is completed, anyhazardous substances remain on a site “above levelsthat allow for unlimited use and unrestrictedexposure for human and environmental receptors,”the proposed NCP would require the lead Agency toreview the remedial action every five years to ensurethat the environment continues to be protected.

8

2.3 Removal Action GuidanceThe Guidance covering removal actions calls uponthe OSC to consider threats to the environment inaddition to public health when preparing the ActionMemorandum required for al l removals.2 F o rexample, in discussing the role of the NationalResponse Team (NRT), the Guidance states that theNRT "should be activated as an emergency responseteam if [al release . . . [i]nvolves significantpopulation threat or national policy issues . . . orsubstantial threats to natural resources. "3 In thesection on determining the need for and urgency of aremoval, the manual specifies:

At any release, regardless of whether the site ison the NPL, where the OSC determines thatthere is a threat to public health, welfare or theenvironment, . . . the OSC may take anyappropriate action to abate, minimize, stabilize,mitigate or eliminate the actual or potentialrelease and the resulting threat.4

For those incidents not categorized as “classicemergencies,” the Guidance indicates that “the OSCshould conduct more extensive data collection andanalysis to document more completely the actual orpotential health and environmental threat.” As anexample, the manual calls on the OSC to “make aconcerted effort to use existing environmental andhealth standards as triggers for initiating responseand as guidelines in determining response actions.”5

In describing the contents of the preliminaryassessment, the Guidance points out that “the OSCmust incorporate any special procedures or technicalcriteria EPA has established for a variety of special,complex cases,” which include floodplains andwetlands. 6 Among the determinations that need to bemade at the conclusion of the prel iminaryassessment, the Guidance includes the following

If the OSC determines that natural resourceshave been or are likely to be damaged, the OSCshould ensure that the trustees of the affectednatural resources are notified in order that theymay initiate appropriate actions7. . . .

The Guidance devotes a section to removal actions infloodplains and wetlands, pointing out that suchactions “should be consistent to the extent practicablewith Federal policy and procedures for the protection

2Superfund Removal Process (OSWER Directive 9360.O-03B).EPA Office of Emergency and Remedial Response, February 1988.3 Ibid., p. III-10.4 Ibid., p. 111-14.5 Ibid., p. Ill-15.6 Ibid., p. Ill-11.7 Ibid., p. 111-12.

of floodplains and wetlands.” Descriptions andreferences for the specific regulations are given inSection 2.5, below. Under the policy established bythe Office of Emergency and Remedial Response,specific actions are required of the OSC:

“[As] part of the preliminary assessment, . . .determine whether the release is in, near oraffecting a floodplain or wetland.”

If “the release is in proximity to or has thepotential to affect a floodplain or wetland,”evaluate

“Poss ib le impac t o f p roposed re sponseactions on the floodplain/wetland,”

“Alternate response actions. ..,” and

“Measures to minimize potential adverseimpacts.”

"[D]ocument the results of this evaluation in theAction Memorandum."

“[E]nsure that the implementation of approvedresponse actions minimizes adverse impacts onthe floodplain/wetland.”8

The Guidance also makes specific reference to envi-ronmental threats in the Appendices describing theAction Memorandum. For example, demonstration ofactual or potential “catastrophic environmentaldamage” may be cited as the reason for activating anOSC’s $50,000 authority in a time-critical removal.In describing the characteristics of an incident, theOSC is asked to demonstrate “that the incidentalready has posed or imminently will pose animminent and significant danger to the public or tothe environment.” One way of demonstrating this isto show “proximity to . . . significant naturalresources.” The Guidance goes on to ask several keyquestions whose answers will help determine if theincident is time-critical:

Are there confirmed reports of injuries to naturalresources or injuries to or deaths of flora andfauna? Are more anticipated? How sensitivecritical are these resources (e.g., protectedwildlife refuge)? Is there catastrophic environ-mental damage?

Even if the incident does not appear to be time-critical, the Guidance cautions the OSC that “[s]omeenv i ronmenta l th rea t s a re no t u rgen t , bu tnever the less a re s ign i f i can t . ” To a id indemonstrating that failure to respond “will create an

8 Ibid., pp. IV-12 and IV-13

unacceptable impact on natural resources and theenvironment,” the Guidance poses these questions:

“What additional information (beyond thatrequested in the time-critical screen) documentsthe threat to the environment (e.g., monitoring orother data verifying injury to or destruction ofnatural resources, critical habitats)?”

“What are the known short- and long-term effectsthat are likely if there is no response or responseis delayed? When is that threat likely to manifestitself?” 9

For removals that will take less than 12 months andcost less than $2 million, Appendix 6 of the Guidanceprovides a model Action Memorandum to assist theOSC in meeting the requirements of CERCLA andthe proposed NCP. Under the heading “SiteDescription,” the model reminds the OSC to describe“areas adjacent to the incident or site in terms ofvulnerable or sensitive populations, habitats andnatural resources. ” The section goes on to citesensitive areas such as wetlands, floodplains,“sensitive ecosystems,” or wild and scenic rivers.Under the heading “Threats to the Environment,”the model calls upon the OSC to:

List all the current and potential threats. . . thatadversely affect the environment (e.g., damage toecosystem, animals, ground water). Identify anynatural resource or environmental damage thatalready has occurred and the extent of exposure(e.g., acute or chronic). Indicate whether therehave been reports of deaths of flora or fauna (e.g.,fish kills). . . . Discuss potential damage to theenvironment and indicate a time frame withinwhich damage will occur if response actions arenot taken.

Discuss all actual or potential impacts on theaffected area. Describe any anticipated exposureand whether it is imminent. Indicate whether therelease threatens endangered species, criticalwetlands, or other resources protected under law.State whether natural resources trustees havebeen notified. 10

2.4 Remedial Investigation andFeasibility Study (RI/FS) Guidance

Remedial Project Managers are responsible for allphases of the remedial process, including but notlimited to the RI/FS. Ecological assessment ofappropriate detail may be conducted at any of thesephases. The nature, extent, and level of detail of theecological assessment will be determined according

9 Ibid., Appendix 5, pp. 3-5.10Ibid., Appendix 6, pp. 6-7.

to the phase of the remedial process, the specificstudy objectives, and the characteristics of the siteand its contaminants. These decisions should bemade in close consultation with technical advisers, asdiscussed in Chapter 4.

This Section focuses on ecological components of theRI/FS process as outlined in EPA’s RI/FS Guidance.11In the scoping phase, the RPM develops a project planto define the problem and identify solutions. Amongthe activities at this stage are

collecting and analyzing existing data to developa conceptual model that can be used to assessboth the nature and the extent of contaminationand to identify potential exposure pathways andpotential human health and/or environmentalrecep to r s .1 2

As part of the collection and analysis of existing data,the Guidance specifically mentions "evidence of . . .biotic contamination, " identification of "bioticmigration pathways," information on ecology of thearea, and data on “environmental receptors.” TheGuidance further states:

Existing information describing the commonflora and fauna of the site and surrounding areasshould be collected. The location of anythreatened, endangered, or rare species, sensitiveenvironmental areas, or critical habitats on ornear the site should be identified.13

A limited field investigation may be undertaken inthis phase of the RI/FS process. The Guidanceincludes a preliminary “ecological reconnaissance” inthe list of possible components of this fieldinvestigation.

The project planning stage is also the time for theRPM to begin preliminary identification of ARARsand To Be Considered (TBC) information. TheGuidance points out that some requirements “mayset restrictions on activities within specific locationssuch as floodplains or wetlands.”14

Characterized as the most important part of thescoping process, the identification of data needsincludes determining the information required to“define source areas of contamination, the potentialpathways of migration, and the potential receptorsand associated exposure pathways.” The objective is

11 Guidance for Conducting Remedial Investigations andFeasibility Studies under CERCLA (Interim Final}. OSWER

12

13

14

Directive 9355.3-01. EPA Office of Emergency and RemedialResponse. October 1988.

Ibid., p. 2-2.

Ibid., p. 2-7.

Ibid., p. 2-13.

10

to determine “whether, or to what extent, a threat tohuman health or the environment exists.”15

The culmination of the project planning stage is thepreparation of the Work Plan and the Sampling andAnalysis Plan (SAP). The Work Plan includes apreliminary evaluation of (a) potential pathways ofcontaminant migration and (b) public health andenvironmental impacts. The SAP is a key step in theassessment process, because it defines what data areto be sought, why the data are needed, where and howthe data will be collected, and how the data will beanalyzed and interpreted. Equally important, theSAP specifies the data quality objectives and qualityassurance plan for the study, indicating the levels ofprecision and accuracy that are expected in datacollection and analysis, and describing how theexpected precision and accuracy will be maintained.

It is at this stage that data collection for ecologicalassessment should be planned, including fieldsurveys, toxicity testing, bioaccumulation studies,a n d s a m p l i n g t o d e t e r m i n e t h e e x t e n t o fcontamination. 16 As with other aspects of the SAP,the planning process for ecological assessment maybe iterative: that is, analysis of early data mayindicate that the sampling and analysis needrevision. This may entail expanding the area to besampled or planning new toxicity tests. It may alsopoint to a reduction in effort if anticipated results failto materialize.

In describing the baseline risk assessment for the RI,the RI/FS Guidance makes frequent reference to theecological side of the assessment. The baseline riskassessment is intended to “provide an evaluation ofthe potential threat to human health and the

environment in the absence of any remedial action. ”The p rocess inc ludes among i t s t a sks theidentification and characterization of (a) levels ofcontamination in relevant media, including biota,and (b) “potential human and environmentalreceptors.” The toxicity assessment component“considers . . . the types of adverse health orenvironmental effects associated with individual andm u l t i p l e c h e m i c a l e x p o s u r e s . ” T h e r i s kcharacterization component entails estimating“carcinogenic risks, noncarcinogenic risks, andenvironmental risks.” 17 The Guidance specifiesfurther:

Characterization of the environmental risksinvolves identifying the potential exposures tothe surrounding ecological receptors and

15 Ibid., p. 2-14. 16 See EPA/ORD, Ecological Assessments of Hazardous Waste

Sites: A Field and Laboratory Reference Document(EPA/600/3-89/013) for specific information on field andlaboratory methods.

17 Ibid., pp. 3-35 through 3-43.

evaluating the potential effects associated withsuch exposure(s). Important factors to considerinclude disruptive effects to populations (bothp l a n t a n d a n i m a l ) a n d t h e e x t e n t o fperturbations to the ecological community.18

The Feasibi l i ty Study involves screening ofremediation alternatives for their effectiveness,including their “potential impacts to human healthand the environment during the construction andimplementation phase.”19 Alternatives are expectedto be evaluated during the screening process “toensure that they protect human health and theenvironment from each potential pathway ofconcern .” 2 0

2.5 CERCLA Compliance with otherEnvironmental Statutes (ARARs)

Section 121(d)(2)(A) of CERCLA requires that theSuperfund remedial action meet Federal and Statestandards, requirements, criteria, or limitations thatare “applicable or relevant and appropriaterequirements” (ARARs). The OSC or RPM isresponsible for identifying potential ARARs for eachsite.

The RPM or OSC should use the EPA ARARsManual21 to assist in identifying potential ARARs ona case-by-case basis . Some of the Federa lenvironmental statutes and regulations that may beARARs for a particular site include:

The Resource Conservation and Recovery Act of1976, as Amended. RCRA requirements forground-water protection, surface impoundments,waste piles, underground storage tanks, andsurface treatment are all considered to bepotentially applicable for both human health andprotection of the environment at sites thatcontain RCRA-listed or characteristic wastes andwhere waste management activities took placeafter the effective date of the relevant RCRASubtitle. The RPM or OSC should consult withthe appropriate Regional RCRA staff to makethis determination.

The Federal Water Pollution Control Act, asAmended. This law, also known as the CleanWater Act, includes numerous sections that maypertain to remediation of Superfund sites. TheOSC or RPM should consult the ARARs Manualfor a detailed discussion of relevant sections.

18 Ibid., p. 3-43.1 9

2 0

2 1

Ibid., p. 4-24.

Ibid., p. 4-30.

CERCLA Compliance With Other Laws Manual, (OSWERDirective 9234.1-01) EPA Office of Emergency and RemedialResponse. Draft , August 8, 1988.

11

Section 404, which requires protection ofwe t l ands , i s o f spec ia l impor tance fo renvironmental evaluation of Superfund sites.

The Clean Air Act of 1970, as Amended. Underthe CAA, EPA has established National AmbientAir Quality Standards for key pollutants. In thedevelopment of these standards, the Agencyprepares Air Quality Criteria documents thatinvestigate various effects of exposure to thesubject pollutants, including those that occur onvegetation. These criteria documents and thestandards developed from them may helpestablish remediation criteria where airborneexposure is possible. In addition, EPA hasestablished limitations for numerous chemicalsin i t s Na t iona l Emiss ion S tandards fo rHazardous Air Pollutants and the New SourcePerformance Standards. The OSC or RPM maywish to determine the utility of these standardsfor the protection of natural resources fromairborne exposure to contaminants.

The Toxic Substances Control Act of 1976. Section2601 (b) of the Toxic Substances Control Actstates the policy of the United States that “. . .adequate data should be developed with respectto the effect of chemical substances and mixtureson health and the environment . . . .” Datacollected under TSCA concerning ecologicaleffects may prove useful in determiningprotective levels of contaminants. The OSC orRPM should refer to the ARARs Manual for otherinformation on applicability of TSCA.

The Federal Insecticide, Fungicide andRodenticide Act of 1947, as Amended. FIFRArequires that all pesticides be registered withEPA. To obtain registration, manufacturers mustsupply EPA with certain data concerningenvironmental fate and transport, health effects,and ecological effects. EPA’s Office of PesticidePrograms (OPP) has issued Registrat ionStandards, which summarize the Agency’sassessment of many pesticide active ingredients,some of which are found at Superfund sites. Theanalyses contained in these documents mayassist in the evaluation of hazards and indetermining protective levels of contaminants.OPP’s regulatory positions on the continuedregistration of individual pesticides may alsoprovide guidance on controlling environmentalhazards.

Endangered Species Act of 1973, as Reauthorizedin 1988. Section 7 of the Act requires Federalagencies to ensure that their actions will notjeopardize the continued existence of any endangered or threatened species. The U.S. Fishand Wildlife Service and the National Marine

Fisheries Service have primary responsibility forthis Act.

Fish and Wildlife Conservation Act of 1980.Section 2903 requires States to identifysignificant habitats and develop conservationplans for these areas. Although it is unlikely thata Superfund site would be located in one of thesesignificant habitats, the RPM should cofirm thiswith the responsible State agency.

Marine Protection, Research and Sanctuaries Actof 1972. Section 1401 declares the U.S. policy ofregulating dumping to “. . . prevent or strictlylimit the dumping into ocean waters of anymaterial which would adversely affect humanhealth, welfare, or amenities or the marineenvironment, ecological systems, or economicpotentialities.” This legislation may be relevantfor cleanup and removal actions at or near theocean.

Coastal Zone Management Act of 1972. Thislegislation is designed to (a) encourage States todevelop management plans to protect andpreserve the coastal zone, and (b) ensure thatFederal actions are consistent with thesemanagement plans. The RPM or OSC would needto obtain these management plans if remedial orremoval actions will take place in the coastalzone.

Wild and Scenic Rivers Act of 1972. Section 2171declares that certain rivers “. . . possessoutstanding remarkable scenic, recreational,geologic, fish and wildlife, historic, cultural, orother similar value” and should be preserved. [fremedial or removal action is taking place at ornear a river, the RPM or OSC should determinewhether it has been designated as “wild andscenic,” and whether there are any action-specificARARs regarding the site or its contaminants.The National Park Service has primaryresponsibility for this Act.

Fish and Wildlife Coordination Act, as Amendedin 1965. Section 662(a) states that the Fish andWildlife Service must be consulted when bodies ofwater are diverted or modified by anotherFederal Agency. The facility is to be constructed“with a view to the conservation of wildliferesources by prevention of loss, or damage to suchresources a s we l l a s p rov id ing fo r thedevelopment and improvement thereof. . . ." TheRPM should consult with USFWS or NOAA ifremedial action entails altering streams orwetlands.

The Migratory Bird Treaty Act of 1972implements many treaties involving migratorybirds. This statute protects almost all species of

12

native birds in the U.S. from unregulated “take,”which can include poisoning at hazardous wastesites. The Act is a primary tool of the U.S. Fishand Wildlife Service and other Federal agenciesin managing migratory birds.

- The Marine Mammal Protection Act of 1972. Thislaw protects all marine mammals, some but notall of which are endangered species. The NationalOceanic and Atmospheric Administration hasprimary responsibility for this Act. The Fish andWildlife Service also has responsibility for somespecies.

Under the authority of the Clean Water Act, EPAdevelops Federal Water Quality Criteria (FWQCs),including criteria for protection of aquatic life. In1987, EPA’s Office of Water Regulations andStandards revised and published its Quality Criteriafor Water, 1986. For each of more than 120 inorganicand organic compounds, this publication containsnumerical Ambient Water Quality Criteria for theprotection of fresh and salt water plants and animalsand their habitats, covering both acute and chronicexposure. The proposed NCP describes the FWQCsa s :

. . . nonenforceable guidelines used by the Statesto set Water Quality Standards (WQS) for surfacewater. . . . States designate the use of a givenwater body based on its current and potential useand apply the FWQC to set pollutant levels thatare protective of that use. . . . If a State haspromulgated a numerical WQS that applies tothe contaminant and the designated use of thesurface water at a site, the WQS will generally beapplicable or relevant and appropriate fordetermining cleanup levels, rather than aFWQC.

The proposed NCP discusses the difference betweenuse of a FWQC when the water will be used fordrinking and when the principal human exposure isexpected through consumption of fish. SeparateFWQC exist for protection of aquatic life. Accordingto the proposed NCP:

A FWQC for protection of aquatic life may berelevant and appropriate for a remedy involvingsurface waters (or ground-water discharges tosurface water) when the designated use requiresprotection of aquatic life or when environmentalconcerns exist at the site. If protection of humanhealth and aquatic life are both a concern, themore stringent standard should generally beapplied.

The proposed NCP sets several cri teria fordetermining the relevance and appropriateness of aFWQC. The FWQC should be “intended to protect theuses designated for the water body at the site, or . . .the exposures for which the FWQC are protective arelikely to occur.” The FWQC “must also reflect currentscientific information.” Finally, the relevance andappropriateness “depends on the availability ofstandards, such as an MCL [Maximum ContaminantLevel] or WQS, specific for the constituent and use.”

It is important to stress that the above list of statutesis not intended to be exhaustive. In particular, thepreceding discussion focused only on potentiallyapplicable Federal laws and regulations. State, local,and other Federal requirements may also beapplicable or relevant and appropriate. For a specificsite, specific requirements will apply, depending onthe contaminants of concern, the location of the site,and the potentially exposed receptors. Some, all, ornone of the potential ARARs discussed in this Sectionmay apply. The RPM or OSC should confer withappropriate State regulatory authorities, officials inother EPA programs, and representatives of other Federal agencies in the event of uncertainty onpossible ARARs.

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Chapter 3

Basic Concepts for Ecological Assessment

This chapter has three purposes. First, the chapterintroduces and defines ideas and terms commonlyused in ecology. Our intent is to make the RPM orOSC aware of the general meaning of these concepts,so as to facilitate discussion with the technicalspecialists providing consultation on ecologicalassessment. Second, the chapter discusses the natureof contaminants’ ecological effects. Although acontaminant may cause illness or death to individualorganisms, its effects on the structure and function ofecological assemblages may be measured in termsquite different from those used to describe individualeffects. Third, the chapter describes some of thebiological, chemical, and environmental factors thatinfluence the ecological effects of contaminants.

Readers who are familiar with these topics may wishto skim this chapter. Those who are well versed inecology and environmental chemistry may want toskip it entirely.

3.1 Objects of Study in EcologyEcolog i s t s gene ra l ly s tudy th ree l eve l s o forganizat ion: populat ions, communit ies , andecosystems. (See Figure 3.1.) Each level has itscharacteristic measures of extent, structure, andchange.

A population is a group of organisms of the samespecies, generally occupying a contiguous area, andcapable of interbreeding. The size and extent ofpopulations are most often described in terms ofdensity, the number of organisms per unit area. Suchterms as standing crop or standing stock may be usedto indicate population size at a particular timeinterval, with the unit area specified or implied. Thestructure of populations is often expressed in terms ofthe numbers of organisms in different age classes,such as eggs, juveniles, and adults. Populationgrowth and decline are determined by characteristicrates of birth, death, immigration, and emigration,all of which are subject to change with environmentalconditions, including interaction with populations ofother organisms.

No species in nature exists in isolation from allothers. Populations of different species live together

Ecosphere

Ecosystems

Communities

Populations

Organisms

Realm

of

Ecology

Figure 3.1. Levels of organization of matter.Source: Living in the Environment, 3/E, by G .

Tyler Miller, Jr. Copyright (C) 1982 byWadsworth, Inc. Reprinted by permissionof the publisher.

in complex associations called communities. Theinteractions among populations and the chemical andphysical constraints of the environment togetherdetermine a community’s structure and geographicalextent. The structure of a community is defined bywhat species are present, in what numbers, and inwhat proportion to each other. It is also described bythe food web, or trophic structure: that is, whichspecies eat which other species, or who produces andconsumes how much.

15

Most communities change seasonally or over longercycles as some species increase or decrease inabundance in response to environmental changessuch as temperature or rainfall cycles. Communitiesalso can evolve over longer periods of time in aprocess known as succession. In successionalchange, some species are displaced by others and newenvironmental conditions are created that supportmore species. For example, when a meadow “grows”into a forest, annual plants are gradually replaced byperennials, shrubs, and trees. Each plant typemodifies the environment in ways that tend to favorthe succeeding type. Eventually, tree canopies shademuch of the area that was once exposed to sunlight,and a leaf-litter layer covers soil that was once bare.Species diversity - expressed as the number ofspecies or the relative abundance of the variousspecies in a given area - is often used to characterizeand compare the structure and evolut ionary“maturity” of communities. Communities are inconstant” flux as organisms are born, eat and geteaten, immigrate and emigrate, die and decompose.These fluxes are described as energy and nutrientflows through food webs, and are determined by ratesof primary production (photosynthesis) by plants andrates of consumption by herbivores, carnivores, anddecomposers.

Just as populations exist only in association withothers in communities, so too do communitiesinteract continuously with the nonliving componentsof the environment in an ecosystem: “A functionalsystem of complementary relationships, and transferand circulation of energy and matter. ” 1 T h eecosystem comprises all the living organisms, theirremains, and the minerals, chemicals, water, andatmosphere on which they depend for sustenance andshelter. Living and nonliving components are closelylinked, each affecting the other. For example:

- Soil composition and structure are oftenhighly influenced by the organisms thatinhabit it, and by the decomposition productsof organisms after they die.

- Orological formations such as coral reefs andchalk cl iffs are the result of calciumdeposition by plants and animals over eons;they in turn affect the flow of wind and water,and provide habitat for countless otherorganisms.

Ecosystems are characterized by many of the samemeasures as communities: species composition anddiversity, nutrient and energy flows, and rates ofproduction, consumption, and decomposition. Unlikecommunity measures, however, ecosystem structureand function includes nonliving stores of materials

1 Eugene P. Odum, Fundamentals of Ecology, Third Edition(Philadelphia W.B. Saunders Company, 1971).

and energy along with the animals, plants, andmicrobes that make up the biotic portion of theenvironment. Because it encompasses all of therelevant physical and biological relationshipsgoverning organisms, populations, and communities,the ecosys tem i s gene ra l ly cons ide red thefundamental unit of ecology.

Energy and matter flow through ecosystems bymeans of complex systems known as food chainsand food webs. (See Figures 3.2a and 3.2b.) A foodchain describes the transfer of material and energyfrom one organism to another organism as one eats ord e c o m p o s e s t h e o t h e r . F o o d c h a i n s a r ehierarchically arranged into trophic levels:

P r i m a r y p r o d u c e r s - g r e e n p l a n t s(including algae and microscopic aquaticplants called phytoplankton) - capture solar.energy through photosynthesis whichconverts carbon dioxide and water intocarbohydrates, a form of energy storagesuitable for use by other organisms;

Primary consumers (herbivores) e a tplants;

Secondary consumers (carnivores) ea therbivores;

Tertiary consumers (top carnivores) feedon other carnivores; and

Decomposers - including certain fungi, andbac te r i a - feed on dead and decayingorganisms, l ibe ra t ing s imple o rgan icchemicals and mineral nutrients for recyclingin the ecosystem.

Food webs are interconnecting food chains. Thesemore realistically describe the complex system ofpathways by which the flow of matter and energytakes place in nature. Such pathways do not alwaysfollow a strict progression of producer to herbivore tocarnivore. Some plants die and are decomposedwithout first being eaten by herbivores. Many specieshave mixed diets of plant and animal material;others change their feeding habits seasonally or havedifferent food requirements at different life stages.For example, many bird species that feed primarilyon seeds during most of the year switch to insects andother invertebrates when raising young, because thehigher protein content of the animal prey increasesthe likelihood that the young birds will survive.

3.2 Types of EcosystemsThe types of ecosystems vary with climatic,topographical, geological, chemical, and bioticfactors. On land, they range from Arctic tundras totropical rain forests, sand dunes to mountain tops,

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Type of Food Chain

Terrestrial

Grazing

Terrestrial

Decomposer

Terrestrial

Grazing

Decomposer

Aquatic

Grazing

Terrestrial-aquatic

Grazing

Primary Secondary T e r t i a r y QuaternaryProducer Consumer Consumer Consumer Consumer

Rice Humans

Leaves Bacteria

Leaves Fungi Squirrel Hawk

Phytoplankton Zooplankton Perch Bass Humans

Grain Grasshopper Frog Trout Humans

Figure 3.2a. Example of Typical Food ChainsSource: Living in the Environmental, 3/E, by G. Tyler Miller, Jr. Copyright (C) 1982 by Wadsworth, Inc. Reprinted bypermission of the publisher.

deserts to forests, pure stands of evergreens to mixedstands of hardwoods. Freshwater ecosystems includeponds, lakes, streams and rivers. In the transitionzones between land and water, wetlands includefresh-water and salt marshes, wet meadows, bogs,and swamps. Marine ecosystems range fromestuaries and intertidal zones to the open sea anddeep ocean trenches. Each ecosystem type has uniquecombinations of physical, chemical, and biologicalcha rac te r i s t i c s , and thus may respond tocontamination in its own unique way. Not only doesthe environment influence the act ivi t ies oforganisms, but organisms also influence theenvironment.

The physical and chemical structure of an ecosystemmay determine how contaminants affect its resident

species, and the biological interactions maydetermine where and how the contaminants move inthe environment and which species are exposed topart icular concentrations. F o r e x a m p l e ,contaminants in a forested area may be subject to lessdegradation due to sunlight than the same chemicalsin grassland soils. Chemicals adhering to soilparticles are less likely to be washed into streams ifthe soi l is well covered with vegetat ion ordecomposing leaf litter than if the area is sparselyvegetated or bare.

Terrestrial ecosystems are generally categorizedaccording to the vegetation types that dominate theplant community. These are the species upon whichthe rest of the community’s structure is based - theherbivores which feed on the vegetation, the

17

Mountain Lions

Figure 3.2b. A greatly simplified terrestrial food web.Source: Living in the Environment, 3/E, by G. Tyler Miller, Jr. Copyright (C) 1982 by Wadsworth, Inc. Reprinted bypermission of the publisher.

carnivores which feed on the herbivores and on eachother, and the decomposers which feed on the deadplant and animal material and return mineralnutrients to the soil for recycling through the foodweb. The vegetation found at a particular site isdetermined by a wide variety of factors, includingclimate, soil type, altitude and slope of the land, andcurrent and former uses of the land by people. Twovery common ecosystem types in the temperate zoneare deciduous forests and grasslands.

Temperate deciduous (leaf-shedding) forests arefound in eastern North America. They have plentiful,evenly dispersed rainfall, moderate temperatures,and contrasting seasons. The annual leaf fallprovides habitat for large numbers of insects andfungi that feed on the leaf litter, eventually breakingit down into organic materials and minerals thatbuild up the soil.

Temperate grasslands cover the interior of NorthAmerica and Eurasia, southern South America, andAustralia. They receive moderate amounts ofrainfall. Tall grasses tend to grow in soil having a

high moisture content, while shorter grasses occur inmore arid areas. Numerous grass species havedeveloped adaptations to take advantage of seasonalvariations in climate. One group grows in the coolertemperatures of the spring and fall, while anothergroup thrives in the warmer temperatures ofsummer. These seasonal shifts in species’ growthresults in a high annual productivity in grasslands,as the growing season for the community as a wholeis effectively extended to three seasons. Thisproductivity has allowed grasslands to support largeherds of grazing animals, such as bison, but thecomparatively simple vegetation structure tends tosupport fewer animal species than a forest of similarsize. The high volume of plant material available fordecomposition in grasslands creates very differentsoil compositions from those created by forest leaflitter. Occasional fires contribute to the stability ofgrasslands, as they hinder the growth of competitivewoody plants.

Wetlands are areas in which topography andhydrology create a zone of transition betweenterrestrial and aquatic environments. The combined

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characteristics of each create conditions of greatproductivity and biological diversity. Because ofthese unique conditions, both fresh-water and marinewetlands perform several important ecologicalfunctions and provide benefits that can be adverselyaffected by contamination. These include:

Hydrologic benefits such as flood attenuationand ground-water recharge;

- Water-quality benefits such as (a) removaland cycling of sediments, organic materials,and nutrients, and (b) stabilization of banksand shorelines and control of erosion; and

- Wildlife benefits such as providing habitatand food sources for fish, shellfish, waterfowland other birds, mammals and otherwildlife. 2

Contamination may adversely affect wetlandfunctions in many ways, depending on the wetlandtype, geographic location, location within awatershed, and other factors. For example, acontaminated wetland may occur close to a Nationalor State park or wildlife management area, or may beof a type and in an area that contains endangeredspecies. (According to the U.S. Fish and WildlifeService, most endangered species in the UnitedStates are dependent on wetlands.) Ecologicalimpacts to wetlands may be either direct, where acontaminant has been deposited into a wetland, orindirect, where a wetland is in close proximity to acontaminant source.

The type of wetland may by itself be important indetermining the ecological effects of contamination.For example, heavy-metal contaminants are morelikely to impair ecological functions when releasedinto an acidic bog than a similar release into therelatively well buffered waters of a salt marsh.Hence, the classification of wetlands can be used as astarting point for the evaluation of ecologicalimpacts. 3 General wetland types include freshwaterdeciduous wetlands (dominated by red maple in theNortheastern U.S.), wet meadows (transitional stageto terrestrial systems), bogs (acidic peat rich soilsprevalent in the Northeastern U.S.), bottomlandhardwood wetlands (dominant in the SoutheasternU.S.), and coastal salt marshes.

2 For more information, see U.S. Fish and Wildlife Service, AnOverview of Major Wetfand Functions and Values (FWS/OBS-84/18), September 1984.

3 For a more complete reference on classification of wetland types,see Cowardin, Carter, Golet and LaRoe, Classification ofWetlands and Deepwater Habitats of the United States,(FWS/OBS-79/31) U.S. Fish and Wildlife Service, December1979.

Fresh-water ecosystems, though comparativelysmaller in area than marine and terrestrial habitats,are of great significance because they are:

- A major component in the hydrological cycle(rivers and streams drain a large percentageof the earth’s land surface),

- A breeding and rearing habit for wildlifespecies of value to people,

- A readily accessible and low-cost source ofwater for domestic and industrial use, and

- A valued recreational and aesthetic resource.

In fresh-water environments, the dynamics of watertemperature and movement can significantly affectthe availability and toxicity of contaminants.

The waters in lakes and ponds have relatively longresidence times. For example, consider the NiagaraRiver as it flows into Lake Ontario. The Niagara’sstrong currents move a given molecule of water alongthe 37-mile length of the river in about one day.However, the same molecule will remain in the lakefor several years before it flows into the St. LawrenceRiver. A similar molecule will remain in LakeMichigan for nearly a century, while another onewould remain in Lake Superior for 191 years.

In addition, temperate lake ecosystems exhibit strongseasonal cycles. In summer, surface waters warm upand become thermally stratified - that is, they donot mix with the colder bottom waters. (See Figure3.3.) As a result, nutrients released throughdecomposition of animal and plant material tend toaccumulate in the bottom waters. In the fall andspring, when these temperature differentialsdisappear, the waters in the lake are able to mix,allowing circulation of accumulated nutrients. Asnutrients are brought up into water that receivessunlight, they become available to aquatic plants,w h i c h c a n u s e t h e n u t r i e n t s t o s u p p o r tphotosynthesis. These plants provide energy thatsustains growth of most other organisms in the lakesystem. At each of these seasonal shifts, the bioticcommunities in the upper waters exhibit clears u c c e s s i o n a l c h a n g e s i n t h e i r p l a n k t o n i ccommunit ies. (Plankton are small plants andanimals that float passively, or can swim weakly, inthe water column.) These annual cycles can alsogreatly influence the availability of contaminantsthat may reside in the lake sediments for part of theyear and be dissolved or suspended in the watercolumn at other times. Such contaminants maybecome available to upper-water organisms duringperiods of mixing.

Rivers and streams are substantially different fromlakes and ponds not only in their obvious physical

19

Figure 3.3 Thermel stratification of a north temperate lake.Summer conditions are shown on the right, winter conditions on the left. Note that in summer a warm oxygen-richcirculating layer of water, the epilimnion, is separated from the cold oxygen-poor hypolimnion waters by a broadzone, called the thermocline, which is characterized by a rapid change in temperature and oxygen with increasingdepth.

Source Figure 11-9 from Fundamentals of Eco/ogy, Third Edition, by E.P. Odum. Copyright (C) 1971 W.B. Saunders Company, A Divisionof Harcourt, Brace, Jovanovich, Inc. Reprinted by permission of the publishers.

conditions (e.g., moving vs. standing water, low vs.high degree of thermal stratification) but also in thetypes of organisms that they can support, especiallyin the numbers of smaller organisms and in the typesof larger plants and animals. For example, a racingbrook will have low numbers of plankton (regardlessof the concentrations of nutrients present) becausethe current rapidly moves them down-stream. In thesame brook, large plants must be firmly attached torocks or rooted in the sediment, and fish must bestrong swimmers. In contrast, a lake or pond canaccumulate high densities of plankton, and lily padsand slow-swimming fish can thrive. As a broadgenerality, food chains and food webs in flowingwaters will have fewer links or trophic levels thanthose in still waters.

Marine ecosystems are of primary importancebecause of their vast size and critical ecologicalfunctions, which maintain much of the globalenvironment’s capacity to sustain life. The seaaccounts for some 70 percent of the earth’s surfaceand supports a wide variety of life forms at all depths,especially in the areas bordering continents andislands. Oceans are constantly in motion and alwayscirculating, which is critical for replenishingnutrients and dissolved oxygen vital for marine life.The world’s oceans have pH values around 8 andaverage salinity of about 35 parts per 1,000. (Freshwater averages less than 0.005 parts per 1,000.)

The continental shelf comprises the submergedmargins of the land mass. The high concentrationand diversity of marine life found here is due to ahigh level of nutrients deriving from both land andsea bottom. Most of the world’s marine fishinggrounds a re on the con t inen ta l she l f . The

characteristics of different types of ecosystems in thisarea can affect the nature and magnitude of theecological risk associated with contaminants.Intertidal environments, with their continuouscycles of exposure and re-immersion, provide uniquephysical conditions for resident organisms and forflow and availability of contaminants. For instance, avolatile compound introduced into a rocky intertidalzone with considerable wave and tidal action willvolatilize into the air much more rapidly than thesame chemical released into a marsh with few wavesand little tidal action. As another example, crude oilspilled onto the rocky, wave-swept coast of France inthe early 1970s is now difficult if not impossible todetect; similar oil spilled about the same time along amarsh in Buzzards Bay, Massachusetts, is stilldetectable. Hence, tidal and subtidal ecosystems mayrange from relatively sheltered estuaries, wheresediment deposition is the major physical condition,to open coasts, where wind and wave exposure are thedominant forces governing the fate of chemicals.

Estuaries are partly open bodies of water closelyassociated with the sea in coastal zones, includingriver mouths, bays, tidal marshes, or waters behindbarrier beaches. The mechanics of estuarine systemsare unique since they are strongly influenced by thesalt water of tides and the drainage of fresh waterfrom land. Tides play an important role in removingwastes and providing food. With a continual flow ofnutrients from upstream and from nearby marineenvironments, estuaries support a multitude ofdiverse communities, and are more productive thantheir marine or freshwater sources. They are alsoespecially important as breeding grounds fornumerous fish, shellfish, and species of birds.

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3.3 Effects of Contaminants onEcosystems

The introduction of contaminants into an ecosystemcan cause direct harm to organisms, or mayindirectly affect their ability to survive andreproduce. The results of contamination may beimmediately apparent or may become noticeable onlyafter considerable delay. The effects of contaminantson ecosystems are due in part to the physical andchemical properties of the chemicals themselves, butare also mediated by the unique combination ofphysical, chemical, and biological processes occurringin each ecosystem. In addition, populations of exposedorgan i sms can d i f f e r in the i r r e sponse tocontaminants depending on their natural toleranceto the chemical, their behavioral and life-historycharacteristics, the dose to which they are exposed,and the exposure time. Furthermore, responses maybe transient (and therefore reversible) or permanent(irreversible).

Ecological assessment seeks to determine the nature,magnitude, and transience or permanence ofobserved or expected effects . This must beaccomplished in an environment that is itselfchanging and causing change in the organisms andsystems under study. Hence, one critical goal ofecological assessment is to reduce the uncertaintyassociated with predicting and measuring adverseeffects of a site’s contaminants.

3.3.1 Reduction in Population Size

Populations change in size through births, deaths,immigration, and emigration. Contaminants cancause reductions in populations of organisms throughnumerous mechanisms affecting one or more of thesefour processes. Most obvious are increases inmortality due to the exposure of some organisms tolethal doses, or decreases in birth rates caused bysublethal doses. Mortality may also increase becausea food source (e. g., a key prey species) has beendepleted, perhaps by exposure to the contaminant, orbecause the contaminant allows tolerant organismsto outcompete other species for scarce resources.Birth rates can decline not only due to toxic effectsbut also through reduction of suitable breedinghabitat or changes in the availability of high-qualityfood for breeding females. Populations may also bereduced through increased emigration or decreasedimmigration if organisms can sense and avoidcontaminants in the environment, or i f thecontaminants’ sublethal effects cause a change inmigratory behavior.

3.3.2 Changes in Community Structure

Many communities are constantly changing.Populations may increase and decrease with theseasons or over longer periods. Predation and

competition among species may bring about changesin the relative abundance of various species. Chanceevents, such as severe storms, may cause suddenincreases in mortality of some species and open uphabitat for others to colonize. Underlying all of thischange, however, is a certain range of possibilitiesthat help to define a given community. In the absenceof a major disruption, species composition andrelative abundance in a community can be expectedto vary within definable boundaries, perhapscyclically or perhaps randomly.

Contaminants introduced into such systems createnew boundaries, changing the range of possibilitiesin ways that are not always predictable. Becausemost contaminants of concern exhibit toxic effects,they often reduce the number and kinds of speciesthat can survive in the habitat. This may result in acommunity dominated by large numbers of a fewspecies that are tolerant of the contaminant, or acommunity in which no species predominate but mostof the component populations contain fewerorganisms. A contaminant need not be directly toxicto affect community structure. If, for example, achange occurs in the salinity or dissolved oxygencontent of an aquatic system, the new environmentalconditions may eliminate some species and favorothers, creating an entirely new species mix and foodweb. For example, salinity changes in Lake Michiganare changing the species composition of the primaryproducer component of the lake community from onedominated by green algae and diatoms to onecomposed principally of blue-green algae. Becausemany fish species currently in the lake are unable tofeed on the blue-green algae, this species changeportends significant shifts in other segments of thelake community.

Contaminants may cause or induce changes in thecomposition and structure of a biotic community as asecondary effect of the changes in the size ofparticular populations. These species may be a majorsource of food or shelter for the rest of the community,such as the large marine plants that give their nameto California’s kelp forests. Others may be crucial inmaintaining a balance of species in a habitat. If, forexample, a key predatory species is reduced oreliminated, the relative abundance of prey speciesmay change significantly. In studies where predatorystarfish were removed from an intertidal community,the number of species of prey animals (barnacles andshellfish) dropped from fifteen to eight. The starfishwas preventing some species from outcompetingothers because it preyed on whatever species wasmost abundant. In agricultural insect pest control,the phenomena of pest resurgence and secondary pestoutbreaks are well known. When an insecticide killsoff predatory insects along with the target pest, thepest population sometimes rebounds to much highernumbers than before because few predators remain tokeep it in check. Destruction of the predators may

21

also allow populations of other plant-feeding insectsto increase beyond the limits imposed by thepredators, thus creating new pest problems.

3.3.3 Changes In Ecosystem Structure andFunction

As contaminants modify the species composition andrelative abundance of populations in a community,the often complex patterns of matter and energy flowwithin the ecosystem may also change. If certain keyspecies are reduced or eliminated, this may interruptthe flow of energy and nutrients to other species notdirectly experiencing a toxic effect. If plant life isadversely affected by a contaminant, the ecosystemas a whole may capture less solar energy and thussupport less animal life. If microbial or invertebratepopulations are disrupted, decomposition of deadplants and animals may not occur rapidly enough tosupply sufficient mineral nutrients to sustain theplant community.

3.4 Factors Influencing the EcologicalEffects of Contaminants

A contaminant entering the environment will causeadverse effects if:

- I t exists in a form and concentrat ionsufficient to cause harm,

- I t comes in contact with organisms orenvironmental media with which it caninteract, and

- T h e i n t e r a c t i o n t h a t t a k e s p l a c e i sdetrimental to life functions.

Adverse effects may also occur if a contaminantinteracts with other chemicals already present suchas to raise the overall toxicity of the contaminatedenvironment. The likelihood of harm is thus acombined function of chemical, physical, andbiological factors, depending both on the nature of thecontaminant and the nature of the environment intowhich it is released.

3.4.1 Nature of Contamination

Classification of Chemicals

Chemical contaminants typically found at hazardouswaste sites are classified into groups based on theanalytical methods used to analyze for the chemicalsin question. The CLP User’s Guide4 divides thecontaminants commonly found at Superfund sitesinto two major classifications: inorganic and organic

4 User’s Guide to the Contract Laboratory Program, EPA Office of[ADD] (1988).

compounds (substances containing the elementcarbon).

The CLP routine inorganic analytical group issubdivided into two categories: heavy metals (lead,mercury, etc.) and cyanide. For the metal analysis,the OSC or RPM will need to determine whether theyneed “total” metal analysis (sample as collected inthe field) or “dissolved” metal analysis (samplefiltered to remove particulate matter).5 A largeamount of particulates in the sample matrix canproduce large differences in the analytical resultsbetween the two analyses. The choice of analyticalmethod also may depend on the expected route ofexposure and the biotic species of concern at aparticular site.

The routine organic analyses are subdivided intothree categories: volatiles (benzene, vinyl chloride,etc.), semivolatiles (phenol, naphthalene, etc.), andpesticides (DDT, arochlors, etc.). For compounds notroutinely analyzed for, or for unusual matrices,special analytical methods may be requested from theCLP. The OSC or RPM should consult the CLP User’sGuide regarding the availability of special services.New procedures are also being developed in responseto special requirements at some sites.

When requesting analytical services, the OSC orRPM should take note of any special conditions on thesite that may make results of routine analysesinsufficient for assessment needs. For example, itmay not be possible to detect very low concentrationsof certain contaminants in a sample matrix thatcon ta ins ( a ) h igh concen t ra t ions o f o the rcontaminants or (b) chemicals (interferents) thatcoextract with the contaminants of concern.

Physical and Chemical PropertiesMeasurement of key physical/chemical properties ofcontaminants is useful in ecological assessment fortwo main reasons. First, these properties generallygovern the transport and fate of chemicals in aparticular environment. Second, for chemicals aboutwhich little is known, these characteristics can helpthe analyst identify chemical analogues among othercommonly observed compounds that may serve asinitial predictors of the novel compound’s transportand fate.

The Superfund Exposure Assessment Manual (EPA,1988), or SEAM, provides a comprehensivediscussion of the environmental fate of contaminantsby medium. Chapter 3 of the SEAM, “ContaminantFate Analysis,“ includes both screening criteria andquantitative methods. Intermedia transfers andtransformation are included in sections covering

5 “Filtered” is operationally defined as that which passes through a0.45 µm filter.

22

atmospheric, surface-water, and ground-water fate,as well as biotic exposure pathways. In addition, theEcological Information Resources Directory (EPA,1989) will contain updated references for someparameters, such as bioconcentration factors.

Frequency of Release

The ecological effects of a single or occasional releaseare likely to be considerably different from thoseassociated with a continuous release. Frequentrelease of a nonpersistent compound may have along-term effect equivalent to a single release of avery persistent chemical. Occasional release maytemporarily depress an invertebrate population, butcontinuous release may trigger drastic shifts in thespecies composition of an ecosystem. These effectsshould be carefully considered when performingquantitative exposure analyses as described in theSEAM.

Toxic chemicals may enter the environment, or moveamong compartments of the environment, on severalpossible time scales. For example, toxic dischargesfrom a Superfund site to a waterway may occur:

- Only once (e.g., from an accidental spill),

- Intermittently (e.g., from storms causingnonpoint-source runoff of contaminatedsoils),

- Seasonally (e.g., from snowmelt in thespring),

- Regularly (e.g., from daily activities at thesite), or

Continuously (e. g., from ground-waterdischarge to the waterway).

Some or all of these types of release may happen at aparticular site, and each type of release may cause adifferent concentration and mass to enter thewaterway.

Different species of plants and animals may havedifferent abilities to withstand or resist intermittentor continuous releases of toxic chemicals, so it isimportant to characterize the sources in terms of thekind of release that is occurring. For example, adultsof a species may withstand a short-term dischargethat kills all the juveniles, but be severely affected bya regular or continuous release. If such a differentialeffect were suspected, knowing the nature of thedischarge might lead to monitoring strategies thatemphasize one life stage or the other. Similarly,chronic discharges that allow bioaccumulation ofcertain toxicants may cause more lasting damage to

certain species than to others. Such releases might beespecially harmful to relatively immobile species.

Toxicity

Exogenous chemicals in an ecosystem can greatlyincrease the mortality rate of component populations,or can change the organisms’ ability to survive andreproduce in less direct ways, such as:

- Altering developmental rates, metabolicprocesses, physiologic function, or behaviorpatterns;

- Inc reas ing suscep t ib i l i t y to d i sease ,parasitism, or predation;

Disrupting reproductive functions; and

- Causing mutations or otherwise reducing theviability of offspring.

In assessing toxicity, the analyst is concerned abouttwo aspects. The hazard posed by a contaminant isthe effect (or endpoint), such as those mentionedabove, that the chemical (or mixture of chemicals)can cause in the organism. The dose-responserelationship describes the amount of chemicalnecessary to produce the observed effect. A broadarray of toxicity tests are available for evaluating theeffects of contaminants and their dose-responserelat ionships. These are summarized in thecompanion volume to this manual and relatedreferences. 6

The toxicity of a substance is generally described bythe duration of exposure or the reactions it elicits.

Acute

Acute toxicity causes death or extremephysiological disorders to organismsimmediately or shortly following exposure tothe contaminant.

Chronic toxicity involves long-term effects ofsmall doses of a contaminant and theircumulative effects over time. These effectsmay lead to death of the organism ordisruption of such vi tal functions asreproduction.

or chronic exposure can have lethal orsub le tha l e f fec t s .

- Lethal doses cause death directly throughdisruption of key physiological function.Populat ion levels are affected by the

6 Ecological Assessments of Hazardous Waste Sites: AReference Document (EPA/600/3-89/013). EPA Office ofResearch and Development 1969.

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contaminant if the overall mortality rate isincreased.

Sublethal toxicity entails symptoms otherthan death or severe disorder, but may havelong-term effects on a population. Forexample, some toxicants at low concen-trations cause a change in the behavior ofmigratory fish, interrupting their naturalhabit of returning to freshwater streams tospawn.

Evaluating the toxicity of a particular substancerequires careful specification of the endpoints ofconcern, which entails describing

- The organism tested or observed,

- The nature of the effect,

- The concentration or dose needed to producethe effect,

- The duration of exposure needed to producethe effect, and

- The environmental conditions under whichthe effects were observed.

Ecologists will often use professional judgment toselect a particular organism as an “indicator species,”that is, a species thought to be representative of thewell-being and reproductive success of other speciesin a particular habitat. The indicator species mayalso be chosen because it is known to be particularlysensitive to pollutants or other environmentalchanges. In addition, ecologists will often study somelife stage of interest in the indicator species, such as:

- Reproductive success as measured by thesurvival of gametes, larvae, or embryos;

- Survival of juveniles or molts;

- Longevity of adults; or

- Incidence of disease, including physiologicaland behavioral abnormalities.

In studies of toxicity, certain measures are commonlyused:

- L D5 0 o r L C5 0 - the administered dose orenvironmental concentration at which 50percent of the experimental organisms die ina spectified period of exposure time (often 96hours).

- E D5 0 or E C5 0 - the dose or concentration atwhich 50 percent of the experimentalorganisms exhibit a certain nonlethal

physiological or behavioral response in aspecified time period (often 96 hours).

No Observed Effects Level (NOEL) or NoO b s e r v e d A d v e r s e E f f e c t s L e v e l(NOAEL) - these measures, which are nottime-dependent, describe the threshold belowwhich predefined effects are not observed.W h e n t h i s t h r e s h o l d h a s n o t b e e ndetermined, the Lowest Observed EffectsLeve l (LOEL) or Lowest ObservedAdverse Effects Level (LOAEL) describethe lowest recorded dosage at which effectswere observed.

3.4.2 Physical/Chemical Characteristics of theEnvironment

A wide variety of environmental variables caninfluence both the nature and extent of effects of acontaminant on living systems. These factors -interacting with each other, with contaminants, andwith organisms - can affect the outcome of acontamination by:

- Chemically changing the contaminant tomake it more or less toxic,

- Making the contaminant more or lessavailable in the environment, or

- Making the organisms more or less tolerantof the chemical.

Among the many factors that can affect the outcomeo f c o n t a m i n a t i o n i n t h e e n v i r o n m e n t a r etemperature, pH, salinity, water hardness, and soilcomposition.

Temperature affects the chemical activity ofcontaminants and biological activities of organismsin the environment. Low temperatures may beadvantageous in certain contamination episodes,since both chemical and biological activity may below. For example, low winter temperatures canreduce the tox ic i ty o f min ing e f f luen t tomacroinvertebrates found in streams. But the samelow temperatures can be detrimental in othercircumstances. In a study of susceptibility of seabirdsto oil contamination, researchers found that anamount of oil on the feathers too low to cause deathunder normal environmental conditions was muchmore stressful at colder temperatures.

The pH of the environmental medium may affect acontaminant’s chemical form, solubility, and toxicity.This is especially true in the case of toxic metals. Aone-unit decrease in pH can cause a more thantwofold increase in lead concentrations in the blood ofexposed rainbow trout. Studies have also shown that,

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in general, as environmental pH decreases, thetoxicity of contaminants tends to increase.

Salinity, the amount of dissolved salts in a volume ofwater, is an environmental variable to which manymarine and estuarine species are very sensitive.Some contaminants reduce these organisms’tolerance of normal changes in salinity, decreasingtheir ability to adjust to salinity fluctuations. Forins t ance , one spec ies o f yea r l ing sa lmondemonstrated reduced tolerance of increases insalinity after long-term exposure to copper.

Hardness, the amount of calcium, magnesium, andferric carbonate in fresh water, can affect the toxicityof inorganic contaminants. Several Federal and Statewater quality criteria and standards are dependenton specific hardness ranges.

Soil composition can greatly affect the nature andextent of movement and toxicity of contaminants.Soils with a high clay-humus colloid content canabsorb high levels of certain ions and neutralorganics. The organic content of some wetland soilscan bind large amounts of heavy metals, renderingthem unavailable to the biota. Some water-insolublepesticides are known to adsorb to soil particles thatcan then transport the chemical to surface waterwhen erosion occurs. Light, sandy soils readilypermit percolation of chemicals to ground water,which may in turn contaminate surface waters.

3.4.3 Biological Factors

Susceptibility of Species

Species differ in the ways that they take in,accumulate, metabolize, distribute, and expelcontaminants. Taken together, these traits result inmarked differences among species in their sensitivityto contamination. For example, over 400 species ofinsects and mites have developed resistance topesticides used to control them, while hundreds ofother species exposed to the same chemicals remainsusceptible.

Usually, the major consideration as to how specieswill react to a potential toxicant is the dose.Generally speaking, the higher the dose, the greateris the likelihood that biological effects will occur.However, response to a particular dose may alsodepend on the duration of exposure. Some organismscan take in higher doses of a toxic material ifexposure is spread out over time in smaller doses. Forexample, in one experiment, hens were fed leptophos(an organophosphate insecticide) in a single highdose or a series of lower doses. At the lower butmultiple doses, the hens developed ataxia (paralysisof the legs) later than with the single high dose, butthe total dosage over time was greater in the multiple

feeding than the s ingle amount that causedimmediate ataxia.

Susceptibility of an organism varies with themechanism through which contaminants are takenup from the environment. A given environmentalconcentration may result in different actual dosagesfor different species. For instance, some fish not onlytake in certain chemicals through their gills as theybreathe, but can also absorb the chemicals throughtheir skin. Species also differ in the way in whichtheir bodies metabolize, accumulate, and/or storecontaminants. For example, an organism thatcommonly holds energy in reserve in the form of bodyfa t may exper ience l i t t l e e f fec t f rom theaccumulation of fat-soluble chlorinated hydrocarbonssuch as DDT. However, in a time of scarce foodsupplies, the animal might then metabolize largeamounts of fat, receiving a high dose of chemical as itdoes so.

In general, the susceptibility of a species to aparticular contaminant will depend primarily on:

The rapidity with which the contaminant isabsorbed from the environment,

The resultant dosage actually incurred at thephysiological site where toxic effects occurwithin the organism (the “site of action”),

The sensitivity of the site of action to thedosage incurred,

The relationship between the site of actionand the expression of symptoms of toxicinjury, and

The rapidity of repair or accommodation tothe toxic injury.

Characteristics Governing Population Abundanceand DistributionFor a given set of environmental conditions, specieshave characteristic attributes such as birth rates, ageand sex distributions, migration patterns, andmortality rates. The species’ habitat preferences, foodpreferences, and other behavioral characteristics(e.g., nesting, foraging, rearing young) also maydetermine population size and distribution in anarea, and may also significantly affect the potentialfor exposure.

Differences in responses to contamination due to suchcharacteristics may be manifest immediately. Forinstance, a species with a high proportion of juvenilesin its age distribution might suffer a more precipitousdecline after a release than another species that has ahigher proportion of adults, simply because adults of

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a species can often sustain higher doses of a toxicantbefore succumbing than can juveniles.

Alternatively, the effects of species attributesgoverning population abundance and distributionmay become apparent only when the stress isremoved from the environment. Some species arevery successful at colonizing new habitats. Theytypically have high rates of reproduction and shortgeneration times, and are able to disperse widely insearch of suitable habitat. For example, annualweeds, often the first plants to occupy disturbedenvironments, usually produce large numbers ofseeds that are easily dispersed by wind or othermeans. In well established, more stable habitats,such “pioneer” species are often poor competitorsagainst other species for limited resources. Thespecies thriving in stable environments use theresources efficiently in the areas where they becomeestablished, and typically have low reproductiverates, long generation times, and often, longer lifespans. They also tend to be better competitors in theterritories they occupy. These are the species that aremore likely to recolonize a disturbed habitat onlyafter some considerable delay.

Species often combine characteristics of both of theseidealized types. They may exhibit high reproductiverates and dispersal capability, along with other traitsthat allow them - under the right conditions - tooutcompete later invaders. For example, in thesouthern United States, the imported fire ant hasbecome a serious nuisance due in part to its ability torecolonize areas where insecticides were applied tocontrol it. If the chemicals kill off other ant species,the fire ant is better able than its competitors toimmigrate quickly and become entrenched in thenewly opened habitat.

Temporal Variability in Communities

The effects of a contaminant discharge into aparticular habitat may vary with seasonal or longercycles governing community structure and function.Effects may be apparent immediately at one point ofthe cycle (e.g., in spring), whereas at another pointthe effects would be delayed. Contaminants may alsoelicit different effects at different stages of acommunity’s development.

Seasonal changes entail relatively predictable,ordered changes associated with organisms’ lifehistories, and are driven principally by cyclicalchanges in weather and other physical influences.Examples include:

The spring blooms of plankton in estuariesand lakes,

The change throughout the summer in therelative abundance of species of streaminsects,

The appearance of successive species ofannual plants from spring to fall, and

The concentration and dispersal of variousanimal species for breeding, nesting, andforaging.

When conducting an ecological assessment at aSuperfund site, the analyst must consider these kindsof temporal variations when determining theprobability of exposure. Depending on the time ofyear or the point in some longer cycle, a potentiallyexposed species may or may not be present or in avulnerable life stage at the time of a chemicalrelease.

Successional time scales are less regular and henceless predictable. Biological interactions or physicalchanges mediated by biological activity are usuallyimportant in the evolution of communities. Theclassic example of succession is the gradual change ofa meadow to a forest. This series of events ismeasured in scores of years in undisturbedenvironments, and is not likely to be important inassessment of Superfund sites. Other successionalchange may be brought about by natural disturbanceor human intervention and occur more rapidly. Forexample, intensive herbicide use in agriculturalproduction sometimes results in preferential survivalof weed species that are naturally tolerant to thechemicals used on the site. As the herbicides continueto kill off sensitive species, the herbicide-tolerantweeds come to dominate the non-crop plantcommunity, and may in turn determine whichspecies of insects, small mammals, and birds inhabitthe area.

Movement of Chemicals in Food Chains

Food-chain transfer of contaminants represents apotential exposure route that should be addressed inassessing the ecological effects of a site. The processesinvolved in accumulation and transfer of chemicalsvia food webs are complex. Nonetheless, anunderstanding of a few basic aspects may be helpfulin evaluating the importance of this phenomenon at agiven site:

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Elevated concentrations of contaminants inorganisms compared to environmentalconcentrations may not always signal food-c h a i n t r a n s f e r . A n i m a l s a n d p l a n t scanaccumulate chemicals directly from themedium in which they l ive. Bioac -cumulation 7 of chemicals in this manner isespecially important for aquatic organismsand for terrestrial plants and animals (e.g.,earthworms) in direct contact with soils.Elevated levels of a chemical found in mostfresh-water f ish and aquatic and soilinvertebrates occur by direct concentration ofthe contaminant from the water, soil, orsediment rather than through the food chain.

Certain species are more likely to be exposeddue to food-chain transfer of bioaccumulatingchemicals than others. Predators and otherspecies near the tops of food chains are amongthe most vulnerable. Long-lived, fattier, andlarger species have a greater opportunity toaccumulate compounds in their tissues.Species that are more sensitive to thechemicals than the animals on which theyare preying may be at particular risk ofexposure (e.g., osprey feeding on contam-inated fish).

Certain chemicals are more likely to betransferred via food webs than others.Organochlorines and other persistent organiccompounds (either parent materials ormetabolizes resistant to further degradation)are more likely to be transferred than arenon-chlorinated hydrocarbons and metals.Organic compounds with higher molecularweights are more likely to be transferredthan those with lower molecular weights.Compounds with high Log P8 values aremost likely to be accumulated.

Plants may take up chemicals with low Log Pvalues by way of their roots, but cannottransport significant amounts of compoundswith high molecular weights and high Log Pvalues in the same manner. However, foliagecan become contaminated from soil or waterby sorption of volatilized chemical on theleaves or by deposits of dust, aerosols, andvapors.

7 The process that results in increased concentrations ofcontaminants in organisms with increasing trophic levels in the foodchain.

8 The logarithm of the octanol-water coefficient (KOW). Predictor ofbioaccumulation in the oils of fish end the fat of animals.

Longer food chains increase the time neededto reach equilibrium levels of contaminantsin the predators at the top of the chain. Themaximum value of bioaccumulation in thetop species is also lower in longer food chains,but there is a greater certainty that a toxicchemical will have time to exert its effects onthe population. Table 3.1 illustrates this forDDT applied to forest foliage. The table alsoshows the shift from DDT at the low end ofthe food chain to the more stable and toxicmetabolite, DDE, at the high end.

Bioaccumulation may be less than predictedfor a variety of reasons. For example,organisms may avoid the chemical or preythat have consumed it, or exposure time maybe insufficient to achieve equilibrium inliving tissues. Furthermore, not all foodchain transfers lead to biomagnification 9.Field monitoring should be used whereverposs ib le to de te rmine ac tua l t i s sueconcentrations.

For terrestrial species, bioconcentrationfactors (BCFs)1O of as little as 0.03 can besignficant if the residue is toxic. For aquaticspecies, BCFs greater than 300 are generallyconsidered significant.

Tabla 3.1. Forest Food Chain for DDT

Years toReceptor Chemical Maximum Cone

Foliage DDT o

Forest litter DDT/DDE 1

Litter invertebrates DDT/DDE 2

Ground-feeding birds DDE 4-5

Canopy-feeding birds DDE 5-7

Bird-eating hawks DDE 7-10and owls

Source: James W. Gillett, Cornell University

9 Higher concentration in the consumer than in the contaminatedsource.

10 The BCF is the ratio of the concentration of a contaminant in theorganism to the concentration in the immediate environment (soil,water, and sediments).

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Chapter 4

The Role of Technical Specialists in Ecological Assessment

“Every site is unique.”

This is probably the most common generalization onwhich ecologists who have worked on hazardouswaste sites will agree. It is also only partly true.

What makes every site unique is its particularcombination of characteristics - the contaminants ofconcern, the topography of the site, the presence orabsence of surface water, the vegetation, otherspecies present, soil types, proximity to other import-ant habitats, etc. Taken together, these factorspresent an almost infinite array of potentialecological risk scenarios - the populations at risk, thenature of the contaminants, their toxicity to differentspecies, routes and probabilities of exposure, en-vironmental factors contributing to or inhibitingtoxicity, short- and long-term shifts in the structureof biotic communities, and the effects of remediationon the habitats at or near the site.

Nonetheless, ecologists are able to find commonelements in their study of populations, communities,and ecosystems, some of which were discussed inChapter 3. These common elements form the basis fordesigning a strategy for characterizing any indi-vidual site and defining its specific properties. Thus,although every site is unique, the methods forassessing each site are not. Deciding which factorsare important, and which methods to use to assessthose factors, is a complex task requiring the ex-pertise of ecologists who are familiar with theorganisms, ecological processes, and environmentalparameters that characterize a site. This chapteroutlines how such specialists can help the RPM orOSC specify, obtain, and evaluate informationneeded to assess ecological effects at Superfund sites.

This guidance manual presumes that the RPM orOSC will obtain the assistance of ecologists and otherenvironmental specialists. In some Regions, informalor formally constituted technical assistance groupsalready exist. In other Regions, advice may beobtained from various sources, including:

EPA Regional Environmental ServicesDivisions;

The EPA Environmental Response Team;

EPA Regional NEPA coordinators;

Ecosystem-specific EPA programs, such asthe Great Lakes National Program Office inChicago, or the Chesapeake Bay ProgramOffice in Annapolis, Maryland;

Laboratories of EPA’s Office of Research andDevelopment; and

Regional and field offices of the U.S. Fish andWildlife Service, the National Oceanic andAtmospheric Administration (especiallyNOAA’s Coastal Resource Coordinators), andother Federal and State environmental andresource-management agencies.

Generally, technical specialists serve an advisoryrole. Their function is to assist the RPM or OSC withinformation collection and evaluation, and to helpensure that ecological effects are properly consideredin investigations and decisions. In specific cases, itmay be possible to make arrangements (such asinteragency agreements in the case of non-EPA staff)for them to be involved directly in conducting thework.

In the following sections, we describe how ecologicalspecialists can contribute to the RI/FS and Removalprocesses. We have divided the discussion into fivemajor aspects:

Site characterization,

S i t e sc reen ing and iden t i f i ca t ion o finformation gaps,

Work plan development,

Data review and interpretation, and

Enforcement.

These divisions are made for convenience ofdiscussion only. Not all sites will require all five

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types of activity, and some activities may proceed inparallel rather than sequentially.

4.1 Site Characterization

RPMs and OSCs are encouraged to consult withecologists as early as possible to obtain their help inconducting an effective ecological assessment. Thisassessment should begin with an ecologicalcharacterization of the site. In the RI/FS process, thisstage corresponds with the early phases of developinga site management strategy.

An initial site description will be necessary to orientthe technical specialists. This description should beassembled by the RPM or OSC from existing sourcesof information, without conducting formal fieldstudies. Its primary purpose is to allow the specialiststo:

Identify issues that should be addressed inthe ecological assessment to follow, and

Develop data-collection strategies.

The description should include information on thelocation of the site, its history, likely contaminants ofconcern, and the environmental setting of theproposed actions. Although primary responsibilityfor preparing the site description lies with the RPMor OSC, the technical specialists should provideguidance, when requested, on what information theyneed in the initial site description to allow them tounderstand the scope of the problem. Much of theinformation needed at this stage is commonly usedmaterial, available from published sources or fromprevious assessments of the site. For example, studiesin support of a removal action may be useful inplanning for a Remedial Investigation.

Site location. The technical specialists should beprovided with maps and descriptions of the site,indicating, where possible:

The geographical area ( town, county,quadrant, or other appropriate unit) aroundthe site;

The locations of streams or other surfacewaters on or near the site;

Locations of other ecological habitats such asforested areas, grasslands, floodplains, andwetlands on or near the site;

Locations of soil types and current orprojected uses; and

Locations of contaminant sources at or nearthe site.

Topographical maps published by the U.S. GeologicalSurvey should be provided. For areas that arepredominantly privately owned, floodplains aredelineated on the Flood Insurance Rate Maps and theFlood Hazard Boundary Maps published by theFederal Emergency Management Agency. For areasthat are predominantly owned by States or theFederal government, the controlling agency canusually provide floodplain information.

Documentation of the fact that a site exists in or nearwetlands is an important first step in the ecologicalassessment. Several sources of information areavailable to RPMs and OSCs to determine if acontaminated area is in or near a wetland. Maps ofwetlands are available from a variety of sources,including the U.S. Fish and Wildlife Service, localand State planning agencies, and the Section 404staffs in the EPA Regions. The National WetlandsInventory maps (NWI) developed by the Fish andWildlife Service, or other more specific informationat the State level should be consulted as early aspossible. If more exact locations and/or boundariesare required, the Federal Manual for Identifying andDelineating Jurisdictional Wetlands (March 1989)should be consulted. This manual was developed toidentify jurisdictional wetlands subject to Section 404of the Clean Water Act and the “Swampbusters”provision in the Food Securities Act, as well as toidentify vegetated wetlands for the NWI.

The OSC or RPM should contact the StateGeographical Information System, InformationManagement Office, and Land Management Officesfor additional maps of environmental resources.Aerial and satellite photographs that include the siteand its surroundings should also be sought out andprovided to the specialists if appropriate.

Site history and contaminants of concern. Theinitial site description should include a history of thesite drawn from existing sources. Topics that shouldbe addressed include available information onchemical-handling activities, storage locations, andknown or potential contaminants. If a health effectsassessment has already been performed on the site,standard information on contaminants - chemicalcomposition, amounts, and locations - will also beuseful for ecological assessment. Where available,the descriptions of chemicals should also include in-formation on:

Decomposition rates and products,

Bioaccumulation potential,

Known toxic effects, and

Fate and transport.

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Environmental setting. The initial site descriptionshould include any available information on geology,hydrogeology, and ecological habitats at or adjacentto the site. Geological information may be obtainablefrom existing publications of the U.S. GeologicalSurvey or similar sources. Precipitation records fornearby weather stations (often located at the nearestairport) can be obtained from the National WeatherService. Previous environmental analyses may beavailable for some sites, which could help identifyimportant habitats or species for the assessment toconsider. These might include, for example, anEnvironmental Impact Statement for a nearbyfacility (e.g., highway, power plant), a StateRemedial Action Plan for a designated Area ofConcern, or a National Pollutant DischargeElimination System permit for wastewater dischargeinto a nearby waterway.

Obtaining information about local ecologicalresources may require consultations with localexperts on the subject, including State pollution-control officials, State or Federal fisheries andwildlife-management specialists, State or Federalforesters, agricultural extension agents or SoilConservation Service officials, and others familiarwith the terrain and biology of the region. Theseindividuals may also provide important details re-garding past, present, and likely future uses of landand water resources in the area. The RPM or OSCmay want to consult the technical assistance group orindividual specialists for help in identifying people tocontact for this information. These contacts may alsoprovide assistance in identifying potential ARARs forthe site.

Using this information, the technical specialistsshould be able to begin identifying the habitatspotentially affected by contaminants at the site. Keyto this activity will be a preliminary definition of thelikely pathways for exposure to the contaminants.Once these habitats are identified, the relevant Fed-eral and State natural resource trustees should benotified and invited to participate in planning theecological assessment, if they are not already servingas technical specialists.

If possible, one or more technical specialists shouldaccompany the RPM or OSC to the site for an initialfield reconnaissance. This visit can help clarify forthe assistance group the kinds and amounts of datathat may be needed to characterize the site and itscontaminants, keeping in mind that seasonalchanges may alter the nature and quantity ofreleases or affected organisms.

4.2 Site Screening and Identification ofInformation Gaps

Following collection of existing data, the technicalassistance group should be in a position to determine

the nature and extent of ecological assessment thatwill be necessary for the site. If no ecological exposurepathways have been revealed in this initial review,little or no additional work may be needed. Alter-natively, certain exposure pathways might beeliminated from further study while others mightrequire more data. For instance, if there is no surfacewa te r on the s i t e and no oppor tun i ty fo rcontaminants to reach surface waters off the site,further data on aquatic effects would very likely bepointless, even though concern about exposure toterrestrial organisms might warrant extensivesampling and testing.

Examination of preliminary data could point upimportant gaps in the information concerningcharacterization of the site. Site visits, aerial orsatellite photographs, or information from localexperts may reveal habitats subject to exposure thatwere not part of the original data-gathering effort.For instance, careful examination of the site mightresult in the discovery of a previously unreportedstream running through the property that could raisequestions about contaminants reaching an off-sitewetland.

Review of the data from initial studies may alsoindicate that potential exposure pathways orreceptors were either overlooked or previouslyunknown to the site investigators. For example,evidence might be found that small mammals areburrowing and foraging near storage facilities. Thisinformation would probably raise concern aboutdirect exposure of these animals to contamination.Depending on the persistence and bioaccumulationpotential of the contaminants, the observation ofthese mammals might also suggest additional risk topredatory birds and mammals both on and off the sitethrough the food chain. These concerns might thenlead to a new study plan to trap some of the mammalsand test their tissues for contaminants.

The technical specialists might also conclude frominformation developed during the early stages thatthe contaminants identified at the site are causingunexpected toxic effects. For instance, biotic surveysmight show an absence of certain fish species thatoccur in otherwise similar, but uncontaminated,streams. If there is reason to suspect that the absenceof these fish may be caused by toxic effects, field orlaboratory toxicity tests might be appropriate todetermine the toxicological potent ial of thecontaminants.

4.3 Advice on Work Plans

Where applicable, ecological assessment is anintegral part of the RI/FS Work Plan. Technicalspecialists should be consulted as early as possible inthe development of the Work Plan and the Samplingand Analysis Plan, to ensure that the plans for eco-

31

logical assessment are well designed and capable ofanswering the necessary questions about theecological effects of the contaminants at a site.

Effective ecological assessment will require a designthat is tailored to each site’s specific characteristicsand the specific concerns to be addressed. Choosingwhich of the many possible variables to investigate inthe study will depend on the nature of the site, thetypes of habitats present, and the objectives of thestudy. The technical specialists should thereforeassist the RPM in specifying technical objectives forthe investigation. Such objectives might include:

- Determination of the extent or likelihood ofimpact,

- Interim mitigation strategies and tactics,

- Development of remedies, or

- Remediation criteria.

The technical specialists can thendevelop data quality objectives totechnical objectives.

help the RPMsupport these

Although each assessment is in some way unique, itis possible to outline the general types of data thatmay be required. For terrestrial habitats, thetechnical specialists may specify such data needs as:

- Survey information on soil types, vegetationcover, and resident and migratory wildlife;

- Chemical analyses to be conducted inaddition to any previous work done as part ofa Preliminary Assessment or Site Investiga-tion; and

- Site-specific toxicity assessments to beconducted.

For fresh-water and marine habitats, the informationneeded will most likely include:

Survey data on kinds, distribution, andabundance o f popu la t ions o f p l an t s(phytoplankton, algae, and higher plantforms) and animals (fish, macro- and micro-invertebrates) living in the water column andin or on the bottom;

Chemical analyses of samples of water,sediments, leachates, and biological tissue;

Sediment composition and quality, grainsizes, and total organic carbon; and

Toxicity tests designed to detect and measurethe effects of contaminated environmental

media on indicator species, or on arepresentative sample of species, such aswater fleas (Daphnia or Ceriodaphnia),amphipods, chironomid midge larvae, tubifi-ciid worms, mysid shrimp, and fatheadminnows.

Where specialists have reason to believe thatcontaminants may move from one type of habitat toanother, such as chemicals washing into a stream inrunoff water, data from each potentially exposedhabitat will be needed. The Superfund ExposureAssessment Manual contains much valuableinformation on predicting movement of contaminantsfrom one medium to another.

The technical specialists should also provideguidance on such quality assurance and qualitycontrol (QA/QC) issues as:

The area to be covered in biotic and chemicalsampling programs,

The number and distribution of samples andreplicates to be drawn from each habitat,

The preferred biological analysis techniquesto be used,

Adherence to the assumptions of predictivemodels used in the analysis,

The physical and chemical measurements(e.g., dissolved oxygen in a water sample, pHof water or soil, ambient temperature) to betaken at the time of the survey, and

Any special handling, preservation methods,or other precautions to be applied to thesamples.

T e c h n i c a l s p e c i a l i s t s m a y m a k e s p e c i f i crecommendations on sampling and analyticalmethods, or they may review plans and offercomments or suggestions for improvement of theassessment methodology. Ideally, the sampling andassessment process should be a phased approach,where preliminary results are reviewed by technicalspecialists, who may find reason to suggest changesin the scope of the project or in the methods usedduring subsequent stages of the study.

4.4 Data Review and Interpretation

The technical assistance group should also be calledupon to review data and provide comments on theinterpretation of data. In most situations, extensiveand long-term ecological studies are unlikely to beundertaken, and informed professional judgment willbe required to determine if the weight of evidencesupports a particular decision regarding the site.

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Specialists should be closely involved in reviewinginterim and draft assessments as these documentsare completed. The appropriate specialists should beconsulted to ensure that the assessments:

- A d d r e s s a l l i m p o r t a n t h a b i t a t s a n dcontaminants of concern,

- Identify all significant receptor populations,

- Portray all relevant routes of exposure,

- Characterize al l s ignificant ecologicalthreats, and

- Describe uncertainties in the assessmentprocess.

The specialists may also provide advice on how topresent the results to decision makers who are nottrained in environmental science.

4.5 Advice on Remedial Alternatives

Remediation measures can also pose environmentalthreats.

For instance, channeling a stream may deprive awetland of its primary water source; earthmovingand construction operations may increase siltation ofnearby streams due to increased soil runoff. In suchsituations, compliance with appropriate laws andregulations may require that the remediation planinclude provisions for minimizing environmentaldamage. Ecologists should therefore be involved asearly as possible in the selection and review ofremedial alternatives so that ecological as well aspublic heal th concerns are addressed in theFeasibility Study.

Technical specialists should also be involved indesigning monitoring programs to evaluate thesuccess of a removal or remedial project. Biologicalmonitoring plans should be developed to evaluate theeffects of remedial actions on local populations ofvarious forms of wildlife. In addition, toxicity testscan be used as sensitive indicators of the presence orabsence of contaminants following remediation. Suchtests may be useful in defining cleanup levels.

4.6 Enforcement Considerations

If ecological effects of contaminants area factor in en-forcement actions, technical specialists may be avaluable resource both in crafting the decisiondocuments and in providing support for the decision.Proposed decisions that incorporate ecologicalcriteria for cleanup or remedial action should be re-viewed by appropriate ecological experts to ensurethat the criteria (1) are accurately described and (2)can be effectively implemented. Technical specialistsmay serve as expert witnesses in court oradministrative hearings in support of enforcementactions. Finally, as discussed above, ecologists maybe consulted on the design and implementation ofmonitoring programs to help ensure that remedialactions achieve their objectives.

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Chapter 5

Planning an Ecological Assessment

Because ecological assessments will vary widely fromsite to site, no standard design is appropriate. Thescope, level of detail, and design of the assessmentshould be determined in close consultation withecologists who understand both the technical issuesinvolved and the requirements of the Superfundprogram. Some of the factors that should enter intothe planning stage are:

The objectives of the assessment, asdetermined by the management decisionsrequired at the site;

T h e p r o g r a m m a t i c g o a l s , m a n d a t e dschedules, and budgetary restr ict ionsassociated with the site’s remediation;

The k inds , fo rms , and quan t i t i e s o fcontaminants at the site;

The means of potential or actual release ofcontaminants into the environment;

The topography, hydrology, and otherphysical and spatial features of the site;

The habitats potentially affected by the site;

The populations potentially exposed tocontaminants;

The exposure pathways to potential lysensitive populations; and

The possible or actual ecological effects of thecontaminants or of remediaractions.

This phase of the assessment process is concernedwith determining what information should be collect-ed for an ecological assessment. It consists primarilyof identifying characteristics of the contaminants andthe potentially affected environments, to:

- Determine if enough evidence exists towarrant further investigation of ecologicaleffects at the site;

Establish the scope of the ecologicalassessment (if one is judged necessary) interms of spatial and temporal extent, tests tobe conducted, time and resources needed, andlevel of detail required; and

Define study goals and data quali tyobjectives if collection of new data is deemednecessary.

If new data are collected, it is essential that dataquality objectives reflect specific programmaticgoals and management objectives, to ensure thattime and funds spent to gather and analyze dataare used efficiently and effectively.

This chapter discusses the principal components ofdefining the scope and design:

- Determination of the objectives and level ofeffort appropriate to the si te and i tscontaminants,

- Evaluation of site characteristics,

- Evaluation of the contaminants of concern,

Identification of exposure pathways, and

- Selection of assessment endpoints.

These are logically distinct activities, but they arenot necessarily undertaken sequentially. All may beunderway simultaneously, or one activity may awaitthe outcome of data from other activities. Theoutcome of this process is the Sampling and AnalysisPlan (SAP), which specifies the methods for datacollection and analysis, and the procedures forquality assurance and control (QA/QC).

5.1 Determination of Need, Objectives,and Level of Effort for EcologicalAssessment

Defining the scope and design of an assessment isinitially - based on available information and datafrom previous studies. Using this material, the RPM

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or OSC should consult with technical specialists, whocan be expected to use good professional judgment toprovide advice on how to evaluate a specific site. Theoutcome of this phase should be an assessment designthat will ensure scientific defensibility of data anddecisions based on those data, while remainingcognizant of the CERCLA-mandated schedules andbudget constraints faced by decision makers.

An ecological assessment may be conducted to:

Document actual or potential threat ofdamage to the environment, in support of aproposed removal action;

Define the extent of contamination;

Determine the actual or potential effects ofcontaminants on protected wildlife species,habitats, or special environments;

- Document ac tua l o r po ten t i a l adverseecological effects of contaminants, as part of aRemedial Investigation;

- Develop remediation criteria; and

- Evaluate the ecological effects of remedialalternatives, as part of a Feasibility Study.

A given assessment may entail one or more of theseobjectives as the primary reason(s) for the study.Specification of assessment objectives should in turnallow clear definition of the ecological endpoints ofconcern, the study methods to be employed, and thedata quality objectives for the study.

The RPM or OSC should confer with technicalspecialists to determine appropriate levels of detailfor ecological assessment of a site based on availableinformation. This should be undertaken as aniterative process. Data from the field may warrantfurther investigation and greater detail. Conversely,such data may indicate that little or no additionalwork is necessary to characterize ecological effects.The definition phase should be used to identify thecriteria needed to make these judgments.

Each assessment will vary in the extent to whichresources, exposure concentrations, effects, and othervariables are identified and quantified. The moreserious effects found may not relate absolutely to theamount of detail required in the assessment. Theneed for detailed, quantitative information will bedriven by the difficulty in adequately characterizingthe parameters that comprise the assessment. Forinstance, a fish kill might be readily traced to a highconcentration of a contaminant from a point source.On the other hand, considerable effort might beneeded to evaluate the causes of unusually low

populations of fish in a stream that contains lowlevels of diverse and dispersed contaminants.

5.2 Evaluation of Site Characteristics

5.2.1 Nature and Extent of Contaminated AreaIn defining the scope and design for an ecologicalassessment, it is important to determine the fullspat ial extent of the contaminat ion throughsampling and measurement. The sampling planshould be designed with a broad enough radius tofind the “edge of the plume,” the farthest extent of thecontamination in soils or other environmental media.

Maps and aerial photographs should be usedwhenever possible to define the general habitats at oradjacent to the site. Small wetlands, intermittentstreams, and other potentially important areas thatmight have been missed during a preliminary sitevisit may be seen from aerial photographs or maps.Significant off-site information may also be derivedfrom good maps and photographs (e.g., dischargesfrom surrounding areas that may affect the site).This type of information may provide significantinsight into the conduct of the site investigation.Ground verification of all habitat locations should beconducted before developing any sampling plans.

At this stage, it is also important to determine whichtransport processes are likely to be at work withrespect to each contaminant. From this information,analysts should be able to discern likely off-siteexposure routes and the habitats threatened orpotentially threatened by that exposure. The RPM orOSC should consult the Superfund ExposureAssessment Manual (SEAM) for detailed informationon predicting chemical fate and transport in theenvironment.

In characterizing a site and determining howcontaminants may move through the environmentassociated with the site, the RPM or OSC shouldexamine trend data such as variations in climaticconditions that may affect population levels ofresident species. These data may indicate conditions,such as periods of high rainfall or drought, that placeadditional stress on local ecosystems and may affectthe fate and effects of contaminants.

Based on all of this information, and in closeconsultation with technical specialists, the RPM orOSC should set s i te-specif ic object ives forinvestigation of each potentially contaminatedhabitat, including

Environmental media to be sampled andanalyzed for contaminant levels,

Detection limits for contaminants,

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Toxicity tests to be performed and species tobe tested, and

Ecological (population, community, orecosystem) effects to be measured orpredicted.

Data quality objectives arising from these studyobjectives should then be developed to determinewhat level of effort will be necessary to obtainscientifically defensible answers. It is important toemphasize that the extent of delineation of exposedhabitats should be determined by the potential forexposure, not by arbitrary distances or boundariesthat lack a biological justification.

5.2.2 Sensitive Environments

For a particular site, the project team should preparea list of habitats requiring special attention in theassessment. Although ecological judgment isnecessary to define some priorities, State and Federallaws and regulations designate certain types ofenvironments, such as wetlands, as requiring specialconsideration or protection. Critical habitats forspecies listed as threatened or endangered also mayrequire protection. Consultation with naturalresource trustees and other technical specialists willbe invaluable in ensuring identification of these keyareas.

In addition to identifying habitats that meet specificState or Federal criteria, the project team should alsoconsider if any other habitats on the site are:

– Unique or unusual, or

Necessary for continued propagation of keyspecies (e. g., rare or endangered species,essential food sources or nesting sites forother species, spawning and rearing habitats,etc.).

The importance of habitats on or near a hazardouswaste site will vary from area to area, depending onsuch factors as:

The species native to the area and theirsignificance (e.g., regionally important sportfish),

The availability and quality of substitutehabitats,

The land use and management patterns inthe area, and

The value (economic, recreational, aesthetic,etc. ) placed on such habitats by localresidents and others.

The project team should define and identify sensitiveenvironments based on a site- and area-specificanalysis, keeping in mind the ecological connectionsbetween the site and nearby habitats.

5.3 Contaminant Evaluation

5.3.1 Identification and CharacterizationAlong with site characterization, a parallel prime ob-jective in defining the scope and design of an assess-ment is to characterize the contaminants of concern(and their transformation products) in terms of theirknown or suspected potential to cause ecologicalharm. Besides identifying and classifying the con-taminants of concern, the RPM or OSC should makesure that characteristics of the chemicals are mea-sured that will help to determine the site’s likely eco-logical effects. Based on measured or calculated phys-ical/chemical properties and other published data,the contaminants’ likely persistence in the environ-ment should be estimated. The RPM or OSC shouldalso obtain information to describe the frequency, in-tensity, and route(s) of chemical release to the envi-ronment.

Preliminary information on the physical/chemicalproperties, bioaccumulation potential, and othercharacteristics of contaminants can be used to definethe parameters of studies to be conducted for anecological assessment. For example:

If chemicals are known or suspected to bewater-soluble, analysts should be prepared toinvestigate potential exposure routes toaquatic habitats. Water-soluble compoundsmay also be expected to move readily withinthe aqueous phase of some soils, increasingthe likelihood of exposure for soil-inhabitingorganisms.

For chemicals with low volubility in water,the RPM or OSC should investigate thepotential for the compound to adsorb to soilparticles. Should this occur, the chemicalcould be transported through erosive soilrunoff to surface waters or other terrestrialenvironments near the site. Contaminatedsoil particles may also be ingested byorganisms living on or in the ground.

If a contaminant is judged to be persistent, orif environmental release is frequent orcontinuous, the ecological assessment may(where time permits) include chronic as wellas acute toxicity tests on potentially exposedorganisms. The RPM or OSC may also need toconsider studies and/or use of appropriatepredictive models to assess long-termpopulation effects.

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If compounds are known or suspected tobioaccumulate, studies may be needed todetermine the extent of bioaccumulation inpotentially exposed organisms. This willprobably entail a close look at transport andexposure pathways and collecting data oncontaminant concentrations in tissues oflikely bioaccumulators such as fish.

5.3.2 Biological and EnvironmentalConcentrations

Based on the preliminary information about thenature the contaminants, a sampling and analysisplan can be devised to determine contaminantconcentrations in all relevant media. As in all otherassessments, the best measures are those that areaccurate, precise, and representative of the situationin space and time. The best way to achieve this is toplan sampling programs with ecological assessmentas a clearly specified objective. As a generalprinciple, sampling, monitoring, and measurementshould be designed by taking account of exposurepathways to habitats and organisms on or near thesite.

A brief field reconnaissance of the site, combinedwith accurate maps or aerial photographs, should besufficient to identify important habitats that mayrequire sampling. Consultation with ecologistsfamiliar with the area will probably indicate thekinds of organisms to be expected on the site and theprobable exposure pathways that should beinvestigated. This in turn should lead to studydesigns for measuring contaminants in mediaappropriate to those exposure pathways. Forinstance, if a compound is known or suspected to bevolatile, air sampling in potentially exposed habitatsmay be appropriate. If the chemicals are believed tohave reached surface waters, stream sediments andbiota may need to be analyzed to determine the fullextent of contamination. If biological transport of thecontaminants is considered possible, the samplingplan may need to include testing for the presence oreffects of low levels of chemical at some distance fromthe source.

If contaminants are suspected of bioaccumulation orare considered fairly persistent, the RPM or OSC mayneed to require studies to determine if the chemicalsare being transferred from organism to organismthrough the food web. Food-chain linkages can beevaluated using information on the t rophicrelationships of the species at a site. Directmeasurements of chemical residues in animal tissuesprovide the most direct approach for assessing theextent to which food chain transfer of chemicals maybe occurring. If such biological t ransfer ofcontaminants is suspected, the RPM or OSC shouldconsult with technical specialists on the proper

design of studies to evaluate the extent and effects ofthe phenomenon.

Estimating chemical fate and transport is a key firststep in quantifying exposure. Having identified theexposure pathways, the analyst should plan onsampling pert inent media to determine theconcentrations of the contaminants of concern. Asdiscussed in detail in the SEAM, predictive modelscan help in estimating fate and transport ofcontaminants. For Superfund sites, the analystshould consult the SEAM and specialists todetermine the applicability of any particular modelto the specific site. Among the considerations will bethe assumptions underlying the model, the quantityand quality of input data needed, and the degree ofconfidence in the model’s results. The decision onwhat model(s) to use may determine sampling andanalytical design, including analyses required,sample sizes, sampling method, and samplingfrequency.

5.3.3 Toxicity of ContaminantsA key objective of the definition phase of theassessment process is to develop a sampling andanalysis plan to assess the toxici ty of s i tecontaminants to potentially exposed populations ofplants and animals. Evaluating the toxicity of asubstance at a particular site requires carefulspecification of the effects of concern, such asmortality or reproductive failure, and the duration ofexposure (i.e., acute or chronic). At the planningstage, literature reviews are the most likely sourcesof information on the toxicity of contaminants.Literature searches can help guide an investigation,especially in identifying the likely mechanisms oftoxicity. However, the user of a literature reviewmust fully understand the restricted character of theinformation. Its value in characterizing actual orprobable hazards at a specific site is extremelylimited, for several reasons:

Toxicologists generally study a population ofone species because the effects on acommunity or ecosystem are too difficult forstandard practice. If the species chosen forthe study is not a good indicator species forhabitats found at the site, the study’s findingsmay be a poor predictor of the site’s actualhazards.

Toxicologists generally study the effects of asingle toxicant at a time. This practice israrely representative of field conditionsw h e r e o r g a n i s m s m a y b e s t r e s s e dsimultaneously by several toxic ants ,fluctuations in the availability and quality ofnutrients, and variations in weather andclimate. When organisms are exposed to twotoxicants at the same time, the effects may be

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directly additive, more than add i t ive(synergist ic) , o r l e s s t h a n a d d i t i v e(antagonistic), depending on the toxicants inquestion, the organisms exposed, and theenvironmental conditions.

Published research may use death or asubacute effect, such as behavioral change, asthe endpoint. Incorporating statistics intotheir analyses, scientists may select themedian (50 percent) response of a population,or they may choose some other percentile ofresponse as appropriate, perhaps the 10percent or the 90 percent response. Unlessthe measures used in the research correspondwell to the objectives of the ecologicalassessment, the results may be difficult toapply to the specific site or contaminants atissue.

Researchers usually report a fixed time for anexperiment. For example, for aquatic tests,toxicologists often study the response over 48or 96 hours, depending on the species and thetoxicant. Occasionally, researchers will studya complete generation of organisms or acomple te cyc le o f r ep roduc t ion andrecruitment, but rarely do they have ther e s o u r c e s o r t i m e t o s t u d y s e v e r a lgenerations.

A wide array of experimental protocols and resultsexists in the literature, in which every variation fromstudy to study can be found different organisms,toxicants , laboratory condit ions, endpoints ,concentrations, statistical summaries, and durations.Although all of these studies may be informative forsome purposes, they are difficult to compare andcontrast, and judging the validity of extrapolation toa specific site and its contaminants should be left toqualified specialists.

Despite the wide diversity of experimental designs,ecologists have settled on a few widely recognizedorganisms and protocols for study. For example:

To study effects on terrestrial invertebrates,researchers commonly use one or morespecies of earthworms to represent soilorganisms, generally using two- or four-weektest protocols.

Toxicology studies of birds often use bobwhitequail, ring-necked pheasants, or mallardducks.

Because of their widespread use for humanhealth assessment, there exists a large database of toxicity studies on laboratory rats,mice, and rabbits. Therefore, these are also

commonly used as surrogate species forestimation of toxicity to other mammals.

For equivalent studies of aquatic organisms,scientists have long used species of Daphniaor Ceriodaphnia (water fleas) to representfreshwater invertebrates in 48- or 96-hourtest protocols, while freshwater fish havebeen represented by the fathead minnow,rainbow trout, and bluegill.

The Micro toxR test , dissolved oxygendepletion test, or reazurin reduction test aresometimes used to indicate toxic effects onmicrobial populations.

Commonly studied marine and estuarinespecies include mysid shrimp, Dungeness andblue crabs, oysters, mussels, and sheepsheadminnows.

For studies of effects on plants, domesticatedspecies are often used, such as lettuce seeds ingermination tests.

It is often possible to select one or more of thesecommonly tested species as surrogates for speciesfound at a site if toxicity testing is warranted. Todevelop a proper understanding of conditions at thesite, data on surrogate species need to be interpretedby wildlife/fishery toxicologists and ecologistsexperienced in evaluating contaminants. Differencesin physiology between closely related species orapparently minor differences in physical or biologicalconditions at the site can often complicate suchinterpretations.

Literature surveys can help identify possible targetsfor investigation if toxic effects are reported, but theyare unlikely to eliminate chemicals from furtherconsideration if negative results are reported.Positive findings in a laboratory research study oftoxic effects may indicate the mode of action of thechemical. They may also help the investigatordetermine the endpoint for toxicity tests conductedwith materials from the site. Laboratory testsindicating low toxicity may or may not mean lowtoxicity in the field, since even the best laboratorysimulation cannot mirror field conditions.

General ly speaking, f ield data, monitoringinformation, and toxicity testing of contaminatedmedia are more useful and reliable than literatureestimates. Wherever possible, the assessment shouldbe based on data collected from the field.

In those circumstances where exposure appearslikely, toxicity testing will be needed to determinethe effects of contaminants in the concentrationsfound or expected at the site on potentially exposedplant and animal populat ions. Results from

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published studies can serve as a useful guide fordeciding:

- What toxicity tests (e.g., acute, chronic)should be conducted with field-collectedsamples,

- What kinds of organisms should be tested,

What effects should be anticipated, and

- How the tests should be interpreted.

From these decisions, a specific set of data qualityobjectives should be formulated, including:

- The number and type of tests to be run,

- T h e e n v i r o n m e n t a l c o n d i t i o n s t o b emonitored,

- The detection limits for contaminants,

The number of samples to be taken, and

- The acceptable margin of error in analyzingresults.

S i t e - spec i f i c in fo rma t ion on sens i t iv i ty tocon taminan t s shou ld be ga the red wherevernecessary and feasible. Studies to collect such datashould be designed carefully, in close consultationwith technical specialists. The general categories ofstudies that might be conducted include thefollowing:

In-situ (in-field) toxicity tests. Methods forin-situ studies are available for aquatictoxicology and, to a more limited extent,terrestrial toxicology. Such methods usuallyinvolve exposing animals in the field toexisting aquatic or soil conditions. Generally,these methods involve the use of enclosures tohold the animals at a specific location for thedesignated exposure period (e.g., caged fishstudies).

Field observations. Correlation of theabundance and distribution of animals andplants with measurements of chemicalconcentrations may not prove the existence oftoxic effects, but may offer some insights as tolikely sensitivities and add to the “weight ofevidence” concerning the site.

Toxicity tests of contaminated water, soil,sediments, or elutriates in the laboratory.These can be used to evaluate the lethal orsublethal effects of chemicals as they occur inenvironmental media. They can also be usedto test for toxicity of mixtures as they

actually occur in the environment. Somemethods for these tests have been publishedby EPA.1

5.3.4 Potential ARARs and Criteria

Once the contaminants at a site have been identified,the RPM or OSC should identify those for whichcriteria have been established, and determinewhether any such criteria apply as potential ARARsat the site in question. (See Chapter 2.) If usable andapplicable criteria exist, the assessment shouldinclude sampling and monitoring plans to determinethe extent to which those criteria are exceeded byenvironmental concentrations at the site. If criteriado not exist for the contaminants in question,analysis of known toxic effects and possible thresholdlevels may be used to develop site-specific criteriaagainst which to compare field data. The RPM orOSC may also wish to consult with technicalspecialists to determine if any chemicals for whichcriteria have been established might be appropriateanalogues for the contaminants of concern at the site.EPA’s Office of Toxic Substances has published avolume describing the use of analogues forestimating toxicity to aquatic organisms.2

5.4 Potential for Exposure

Before the effects of a contaminant on an organismcan be evaluated, it is necessary to know how much ofthe chemical is actually or potentially reaching thepoint of exposure (the location where effects canoccur). This depends on characteristics of thecontaminant, the organism, and the environment.Exposure assessment seeks to answer the followingquestions:

What organisms are actually or potentiallyexposed to contaminants from the site?

What are the significant routes of exposure?

To what amounts of each contaminant areorganisms actually or potentially exposed?

How long is each exposure?

How often does or will exposure take place?

1 Ecological Assessments of Hazardous Waste Sites: A Field andLaboratory Reference Document (EPA/600/389/013), EPA Officeof Research and Development, 1989; J.C. Greene, S.A. Peterson,C.L. Bartels, and W.E. Miller, Bioassay Protocols for AssessingAcute and Chronic Toxicity at Hazardous Waste Sites, E P AOffice of Research and Development, January 1988.

2 Estimating Toxicity of industrial Chemicals to AquaticOrganisms Using Structure Activity Relationships, Office of ToxicSubstances (EPA/560/688/001 ), July 1988.

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- What seasonal and climatic variations inconditions are likely to affect exposure?

- What are the si te-specif ic geophysical ,physical, and chemical conditions affectingexposure?

Analysis of contaminant concentrations in tissues ofexposed organisms can help provide a link betweenenvironmental concentrations and the amount ofcontaminant likely to reach the site of action. Formany contaminants and organisms, time delays mayneed to be considered when attempting to correlateenvironmental and biotic concentrations. This willallow for the time that may elapse before a chemicalis taken up into living tissue. Some of the factors thatmay influence uptake include:

The environmental concentration of thecontaminant in the media to which theorganism is most often exposed;

The metabolic rate of the organism, whichin tu rn may be a func t ion o f suchenvironmental parameters as temperature,availability of sunlight, water, nutrients,oxygen, etc.;

Species-specific metabolic processes, suchas food absorption rates and the ability todegrade, accumulate, store, and/or excretethe contaminant;

Behavioral characteristics such as foodpreferences and feeding rates (both of whichmay vary with the time of year and the age ofthe organism), and the ability to detect andavoid contaminated media or food;

Other characteristics of the organism,such as gill surface area, lipid content, andmetabolic ability to liberate a “bound”residue; and

The bioavailability of the contaminant, i.e.,i ts tendency to part i t ion into a formconducive to uptake; this will vary amongchemicals and organisms. Bioavailabilitywill be influenced by such environmentalfactors as temperature, salinity, pH, redoxpotential, particle size distribution, andorganic carbon concentrations.

Because individuals and species accumulatecontaminants different ial ly in their t issues,environmental concentrations and uptake rates willnot necessarily predict biotic concentrations.Pharmacokinetic distribution following bioaccum-ulation determines the concentration of contaminantthat actually reaches the physiological site of actionwithin an organism, and thus the likelihood of

adverse effects. Whether or not bioaccumulation issuspected, analysts should try to determinecontaminant concentrations in environmental mediaand biotic tissues simultaneously. Based on thesedata, site-specific bioconcentration factors (BCFs)can be estimated. One must make sure, however, thatthe measured environmental concentrations arerelatively stable and not short-term aberrations. Ifsite-specific BCFs cannot be derived from monitoringdata, the analyst may need to use published BCFvalues or predicted BCFs.

To be meaningful, chemical analyses of biota shoulduse sample sizes large enough to obtain variancees t ima tes . E x t r a p o l a t i n g c o n t a m i n a n tconcentrations from a sample of organisms to anaverage for the population may be a complex process.Such factors as the time of year of the sample, the lifestage or age of the organisms, and the spatialdistribution of the population may need to beconsidered. For highly mobile animals, estimates ofexposure may need to be adjusted to account for thelikelihood that not all of the animal’s food will beobtained from the affected area. In one study, forexample, the analysts calculated exposures for minkand mallard ducks based on the assumption that thecontaminated area represented ten percent of theirhome ranges. When such adjustments are made, theanalyst should clearly state the justification for theassumptions and estimates used.

The SEAM provides detailed guidance on estimatingor predicting environmental concentrations in mediaand intermedia transfers of contaminants. Inaddition, it offers a brief discussion on evaluatingbiotic exposure pathways to human populations.However, the SEAM is specifically intended forestimation of human exposure. Since human andenvironmental receptors do not share all exposureroutes, the analyst will need to go beyond the decisionmodels provided in the SEAM to consider exposure ofenvironmental receptors. For example, in theexposure assessment for contaminated soil, theanalyst will need to determine if the soil is sterile orif it is inhabited by plants and animals. If the soil isinhabited, the analyst will need to determine iforganisms are contaminated and, if so, what thepotential is for off-site movement of animals or foodchain transfer of contaminants.

5.5 Selection of Assessment andMeasurement Endpoints

Based on the available information concerning thesite, the contaminants, and the likely exposurepathways, the analyst should identify and selectappropriate endpoints for the assessment. Thecompanion volume to this manual discusses in detailt h e d i s t i n c t i o n b e t w e e n a s s e s s m e n t a n d

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measurement endpoints.3 Assessment endpointsare those describing the effects that drive decisionmaking, such as reduction of key populations ordisruption of community structure. Measurementendpoints are those used in the field to approximate,represent, or lead to the assessment endpoint. If newdata are to be collected to evaluate these endpoints,EPA’s guidance on data quality objectives should befollowed (see Section 5.6).

5.5.1 Ecological EndpointsToxicity of contaminants to individual organisms canhave consequences for populations, communities, andecosystems. As discussed in Chapter 3, changes inrates of mortal i ty, bir th, immigrat ion, andemigration can cause population sizes in an affectedarea to increase or decrease. These changes can alsolead to shif ts in the spat ial dis tr ibut ion ofpopulations in the environment. Such population-level effects may in turn determine the nature ofchanges in community structure and function, suchas reduction in species diversity, simplification offood webs, and shifts in competitive advantagesamong species sharing a limited resource. Finally,e c o s y s t e m f u n c t i o n s m a y b e a f f e c t e d b ycon taminan t s , wh ich can cause changes inproductivity or disruption of key processes. Forexample, at a Superfund site contaminated withcreosote and related compounds, the analysts noted:

The presence of beds of detritus in the stream andlayers of contaminated undecomposed leaves inthe soil indicates that litter degradation is notoccurring, at least not at a natural rate.

Contaminants can disturb ecosystems in ways otherthan direct toxicity. For example, a chemical thatdecreases available oxygen in aquatic systems canhave catastrophic effects, whether or not it is toxic tothe organisms there. Contamination leading todestruction of terrestrial vegetation can result inincreased sedimentation of streams, which canadversely affect benthic populations that never comein contact with the chemical, Remedial actions thatreduce water flow to a wetland or that replaceindigenous vegetation with introduced plant speciescan remove an essential resource for one or morespecies in the community. In assessing the ecologicaleffects of a site or its remediation, the analyst shouldconsider use of appropriate measures of communityand ecosystem function to determine if the weight ofevidence indicates that effects other than toxicity aresignificant.

To characterize the effects of contaminants onpopulations, communities, and ecosystems, the

3 Ecological Assessments of Hazardous Waste Sites: AReference Document. EPA Office of Research and Development,1989.

analyst may choose one or more measures dependingon the objectives of the study.

Use of these measures wil l usually requirecomparison of the site to a carefully selectedreference area. To allow proper comparison, it isimportant that reference areas be chosen that:

- Are in close proximity to the contaminatedarea(s);

- Closely resemble the area(s) of concern interms of topography, soil composition, waterchemistry, etc.; and

- Have no apparent exposure pathways fromthe site in question or from other sources ofcontamination.

The RPM or OSC should consult closely withtechnical specialists on specific criteria for selectingan appropriate reference area.

The following are examples of measures that mightbe used to compare contaminated and referenceareas:

Population abundance - the number ofindividuals of a species in a given area,usually measured over a period of time or at aspecified time;

Age structure - the number of individuals inthe population in each of several age classesor life history stages, which can be anindicator as to whether the population isincreasing, decreasing, or stable;

Reproductive potential and fecundity -expressed as the proportion of females ofreproductive age, the number of gravidfemales, the number of eggs or viableoffspring per female, or the percentage offemales surviving to reproductive age;

Species diversity - the number of species inan area (species richness), the distribution ofabundance among species (evenness), or anindex combining the two;

Food web or trophic diversity - calculatedin the same way as species diversity, butclassifying organisms according to their placein the food web;

Nutrient retention or loss - the amount ofundecomposed litter or, conversely, theamounts of nutrients lost to ground or surfacewaters;

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Standing crop or standing stock - totalbiomass in an area; and

Productivity - sometimes determined in-directly by measuring oxygen production bythe plant community per unit time; ecologistsalso sometimes gauge respiration rates bymeasuring carbon dioxide output per unittime, and calculate the ratio of production torespiration (P/R ratio) as a measure of theefficiency of the ecosystem.

From measures such as these, specific assessmentendpoints can be established, such as “reduction inpopulation abundance” or “reduced fecundity.” Thesewould then be quantified to develop site-specificmeasurement endpoints, such as “significantdifference between contaminated and reference areaswith respect to numbers of organisms or numbers ofyoung per female.”

The analyst should use these measures with a greatdeal of caution. If differences appear in the abovemeasures be tween c o n t a m i n a t e d a n duncontaminated areas, it is a complex task todemonstrate that the effect observed is the result ofcontamination rather than some other factor.

In planning an ecological assessment, the OSC orRPM will be concerned with potentially affectedhabitats and, through them, potentially affectedpopulations. Within each of these categories, a set ofcharacteristic endpoints will need to be considered,and special types will elicit particular attention.

5.5.2 Evaluation of Potentially Affected HabitatsHabitats in the vicinity of a Superfund site can beaffected by:

Direct or indirect exposure to the site’scontaminants due to transport from thesource;

Physical disruption of the habitat due to thesite’s design or operation;

Chemical disruption of ecosystem processesdue to the contaminants’ interference withnatural biochemical, physiological, andbehavioral processes;

Phys ica l o r chemica l d i s tu rbance o rdestruction due to cleanup or remedialactivities; and/or

Other stresses not related to the site or itscontaminants, such as extreme weatherconditions or air pollution.

Each of these types of effects will be manifesteddifferently in different ecosystems, depending on themagnitude of the disturbance and the nature of thehabitat receiving the disturbance. The various typesof terrestrial, aquatic, and marine ecosystems eachhave their own particular structures, dynamics,energy flows, and transport mechanisms thatdetermine how they are affected by chemical orphysical insult such as might occur at a Superfunds i t e .

Structure and DynamicsPlanning an ecological assessment should considercollection of qualitative and (where feasible)quantitative information about the structure anddynamics of biotic communities that are potentiallythreatened, with sufficient detail to:

Decide whether a detailed ecologicalassessment is necessary,

Develop a defensible professional judgmentas to the likelihood of contamination andadverse effects, and

Define study goals and data quali tyobjectives for an ecological assessment if it isjustified by the preliminary evidence.

When considering study objectives for an ecologicalassessment, the RPM or OSC may wish to specifythat data be collected to support calculation of certainmeasures of community structure and function.These include determining species diversity andcommunity productivity. It is important to recognizethat such measures were not designed for the purposeof estimating or demonstrating environmental harm,and they may be inappropriate for many sites. Whenthese measures are used, they should not be reliedupon to the exclusion of other information; rather,they may add to the weight of evidence supporting apa r t i cu la r conc lus ion abou t a s i t e and i t scontaminants. Used properly, in close consultationwith technical specialists, these measures may helpto:

Delineate the extent of contamination at asite, and/or

Document the eco log ica l e f fec t s o fcontamination.

Measures of biotic diversity have often been used toaid in characterizing community structure. The useof these measures in the context of hazardous wastesites rests on the premise that a disturbed or stressedarea will exhibit changes in the composition andrelative abundance of species as compared to areference area that appears not to be contaminated.When using diversity indices or measures of

43

community structure, the analyst should choose forstudy those segments of the ecosystem that are likelyto:

Be exposed to the contaminants of concern,and/or

Contain organisms suspected of beingvulnerable or sensitive to those contaminantsor the effects of remediation.

Thus, for example, if the chemicals are present insurface soils, it would probably be useful to applydiversity comparisons to the soil or leaf litterorganisms at a potentially affected site and areference area.

The Office of Research and Development volume,Ecological Assessments of Hazardous Waste Sites: AReference Document, contains detailed discussions ofassessment and measurement endpoints forevaluating community and ecosystem level effects.

Significance and UniquenessThe significance or uniqueness of an environment isoften a subjective judgment, that may be determinedby social, aesthetic, or economic considerations. Someenvironments, such as cr i t ical habitats forendangered species, are defined by law. To the extentthat these concerns can be spelled out in thedefinition phase, they should be articulated withregard to any such habitats. Generally speaking,environments may be considered significant because,in the professional opinion of technical specialists,they:

Are unusually large or small,

Contain an unusually large number ofspecies,

Are extremely productive (such as animportant fishery),

Contain species considered rare in the area,or

Are especially sensitive to disturbance.

In defining the scope of an ecological assessment,consideration of such environments should be similarto that given to rare and endangered species (seebelow). These areas may have unusual underlyingphysical and chemical characteristics that may affectremoval and remediation decisions. The existence,location, and sensitivity of such environments shouldbe noted, and study objectivesdeveloped to reflect the potentialspecial areas to contamination.

may need to beexposure of these

5.5.3 Evaluation of Potentially AffectedPopulations

Productivity and Abundance

Ecologists use the word “productivity” to mean therate at which new biomass is produced per unit time.Plant stress may be a useful indicator of reducedproductivity in an affected area. Visual inspection ofthe site during an initial visit may be sufficient toidentify probable stress on terrestrial vegetation(such as yellowing, leaf drop, or other symptoms), butit is important to bear in mind that the cause could besometh ing o the r than tox ic e f fec t s o f thecontaminants. Reduction in the growth of plants interrestrial or aquatic habitats will not be as easilyobserved and may require a detailed botanical surveyin comparison to a reference area to be verified.Bioassays may need to be conducted to determine ifthe productivity of the plant community is beingaffected, and whether or not contaminants from thesite are implicated. Toxic effects may be determinedin tests using algae or easily grown terrestrial plantsas test species. Seed germination, root elongation andmorphology, and plant growth assays can be used toevaluate contaminated soils’ effects on plantdevelopment.

Toxic chemicals may exhibit a wide range of effectsthat can ultimately influence productivity andabundance of animals. Effects of contaminants onanimal productivity can be assessed through the useof field ecological studies, on-site toxicity tests, andlaboratory tests. Study designs and data qualityobjectives for field and laboratory studies should bedeveloped to determine exposure concentrations andtheir likely relation to observed or suspected effects.

The RPM or OSC should seek out trend data such aspopulation fluctuations of key species over time. Suchinformation may be available from State and Federalfish and game personnel, or from previousenvironmental analyses (such as an Environmental Impact Statement) conducted in the vicinity of thesite. These data can assist analysts in distinguishingbetween normal fluctuations and changes that maybe attributable to the effects of contamination.

Rare, Threatened, and Endangered SpeciesBy definition, endangered and threatened species arealready at risk of extinction: the loss of only a fewindividuals from the population may have significantconsequences for the continued existence of thespecies. In the definition phase of the assessmentprocess, the presence of threatened or endangeredspecies, and/or habitats critical to their survival,should be documented. If information is available onthese or related species’ sensitivity to contaminantsof concern, this should also be indicated. The RPM orOSC should consult with Federal and State natural

44

resource trustees or other specialists to determine thelocation of such species and their potential forexposure to the contaminants.

Rare species may present a more difficult problem forecological assessment. A species may be rare in agiven locale because:

The area is at the edge of the species’principal geographical range,

The natural habitats available in the areaare only marginally able to support thespecies,

The species may be prevented from attaininghigh numbers by competition from otherspecies or by predation, or

The species depends upon rare habitats orfood sources for its continued existence.

If a species is rare, but not legally designated aseither threatened or endangered, the RPM or OSCwill have to depend on consultation with localecologists and other experts to determine theimportance of the species in the context of the site.

The major sources of information on rare, threatened,and endangered species are field offices of the Fishand Wildlife Service (U.S. Department of Interior)and the National Oceanic and AtmosphericAdministration (U.S. Department of Commerce),officials of State fish and game departments andnatural heritage programs, and local conservationofficials and private organizations.

Potentially Affected Sport or Commercial SpeciesIn planning an ecological assessment, the analystshould note potential effects on species that are ofrecreational and commercial importance. In addition,species such as food sources that directly supportthese important species, and habitats essential fortheir reproduction and survival, should be consideredin the planning and assessment process.

Information on which species are of recreational orcommercial importance in an area can be gatheredfrom State environmental or fish and wildlifeagencies, Federal agencies such as NOAA and theU.S . F i sh and Wi ld l i fe Serv ice , and loca lconservat ion and f ish and game personnel .Commercial fishermen’s and trappers’ associationsmay also be valuable sources of data.

Most States maintain fish stocking programs forsport or commercial fisheries. The agencies runningthese programs can provide information on wherefish are stocked and released, and the areas to whichthey migrate. Many States also gather creel survey

data for stream reaches or other bodies of water, andcollect harvest data for management of deer, gamebirds, and other animals.

5.6 Sampling and Analysis Plan

The planning stage of the ecological assessmentprocess culminates in the Sampling and AnalysisPlan (SAP), which consists of a Field Sampling Planand a Quality Assurance Project Plan (QAPP). Indirecting the preparation of the SAP, the OSC orRPM should be satisfied that the following questionsare answered:

What are the specific objectives of the sampling

How will the proposed data collection meet thoseobjectives?

Will the sampling plan ( types, number,distribution, and timing of samples) providesufficient information to meet the objectives?

Does the sampling plan address all importantexposure pathways and environmental receptors?

Does the sampling plan make the best use ofpreexisting data and sampling locations?

Is the sampling of the various media associatedwith the site coordinated to allow maximumintegration of the data (e.g., to measure or predictintermedia transfer of contaminants)?

5.6.1 Field Sampling PlanTo address all of these issues effectively, a Samplingand Analysis Plan should be developed that takesaccount of:

Actual or potential sources of contaminantrelease,

The media to which contaminants can be or arebeing released,

The organisms that can come into contact withthe contaminants, and

The environmental conditions under whichtransport and/or exposure may be taking place.

Identification of exposure routes and media shouldlead in turn to a selection of the most appropriateplant and animal species to be sampled for analysis ofcontaminant concentration, toxicity testing, or othermeasures of potential effects. If food-chain transfer ofcontaminants is suspected, information on thetrophic structures of affected ecosystems will be

45

needed to determine which species should beexamined for chemical residues.

Biological data to be collected in conjunction withthese analyses may include such parameters as dryweight of tissues or organisms, percent moisture,lipid content, and the size and age or life stage of theorganism. Contaminant concentrations may need tobe expressed relative to the whole-body weight(sometimes minus the intestines) or weight of theedible portion (for input to human health studies).

Depending on the media to be sampled, thecontaminants of concern, and the organisms understudy, the sampling plan will also require collectionof data on environmental conditions at the time of thestudy. For aquatic systems, these include:

- Water quality parameters such as hardness,pH, dissolved oxygen, salinity (for marineecosystems), temperature, presence or absence ofthermocline, color, dissolved organic carbon,conductivity, and total suspended solids;

- Hydrologic characteristics such as flow rate,ground-water discharge/recharge rates, aquiferthickness and hydraulic conductivity, depth,velocity and direction of current, tidal cycle andheights, and surface water inputs and outflows;and

- S e d i m e n t p a r a m e t e r s such as grain s izedistribution, permeability and porosity, bulkdensity, organic carbon content, pH, color,general mineral composition, benthic oxygenconditions, and water content.

For studies of potentially contaminated soil,information will be needed on such parameters asparticle size, permeability and porosity, fraction andtotal organic carbon, pH, redox potential, watercontent, color, and soil type.

The OSC or RPM should consult the SEAM andtechnical specialists to determine the specific set ofenvironmental parameters that should be measuredto permit effective analysis of contaminant fate,transport, exposure, and effects.

5.6.2 Quality AssuranceEPA policy requires that all Regional Offices,program offices, laboratories, and States participatein a centrally managed quality assurance (QA)program. T h i s r e q u i r e m e n t a p p l i e s t o a l le n v i r o n m e n t a l s a m p l i n g , m o n i t o r i n g , a n dmeasurement efforts mandated or supported by EPAthrough regulations, grants, contracts, or otherformal means. Each program office or laboratory thatg e n e r a t e s d a t a m u s t i m p l e m e n t m i n i m u mprocedures to ensure that the precision, accuracy,

completeness, and representativeness of the data areknown and documented.

To ensure that these responsibilities are metuniformly across the Agency, each EPA programoffice or laboratory must have a written QualityAssurance Project Plan (QAPP) covering eachmonitoring or measurement activity within itspurview. These Quality Assurance and QualityControl (QA/QC) requirements apply for allmonitoring at all Superfund sites or at any locationwhere toxic substances have been released to theenvironment.

QAPPs are written documents for all plannedsampling or monitoring at a named location,including ecological assessments of Superfund sites.The program office, Regional Office, contractor,grantee, State, or other organization must prepareand receive written approval for the QAPP for thespecific sampling and measurement program beforethe field or laboratory work can begin.

The QAPP presents, in specific terms, the policies,organization, objectives, functional activities, andspecific QA/QC activities designed to achieve thedata quality goals for single or continuing activities.The QAPP must cover all environmentally relatedmeasurements, including but not limited to:

The measurement of physical, chemical, orbiological variables in air, water, soil, or otherenvironmental media;

The determination of the presence or absence ofpollutants or contaminants in waste streams orsite media;

The assessment of ecological effects studies;

The s tudy o f l abora to ry s imula t ion o fenvironmental events; and

The study or measurement of pollutant transportand fate, including diffusion (i.e., dispersion andtransport) models.

The QAPP serves two important functions. First, itseeks to ensure that as much as possible is done at thebeginning of a study to achieve the QA objectives forthe data. Second, it allows for analysis of the study todetermine what improvements can be made if QAobjectives are not met. The plan cannot guaranteeresults, but it requires the analyst to justify aparticular approach before proceeding.

For each major measurement variable, the QAPPmust state specific data quality objectives. This isusually accomplished by preparing a table listing thevariable, the sampling method, the measurementmethod, the experimental conditions, the target

46

precision (measured in relative standard deviation),the target accuracy (measured in acceptable relativedeviation from the true value), and the completeness(measured in terms of percent coverage). The RPM orOSC should also require project analysts to specifyclearly:

What tests are to be performed,

What measurements are to be taken, and

How the results will be used (e.g., estimateexposure, correlate diversity or abundance with a

chemical gradient, predict population response toambient contaminant levels).

Consultation with a technical assistance group todefine data needs and study goals is essential for thesuccessful specification of data quality objectives.The ecological assessment is not a research projectand thus should not be expected to entail long-termfield studies. With the guidance of technicalspecialists who understand both the scientificquestions at issue and the exigencies of theSuperfund program, it is possible to define carefullydelineated studies to collect the data needed formaking reasoned judgments on Superfund sites.

47

Chapter 6

Organization and Presentation of an Ecological Assessment

This chapter provides a checklist of the basic ques-tions that should be asked in an ecologicalassessment. It is intended to ensure completeness andconsistency in the reporting of assessment results.The amount of detail required in a given report willdepend upon the scope of the study, as determined inthe iterative planning process discussed in Chapter 5,and the amount of data collected in the investigation.Regardless of the level of detail, the assessmentreport should be clear and concise, to ensure that theresults are readily understood and properlyinterpreted.

To aid Agency review of assessments, metric unitsshou ld be used th roughou t . These inc ludespecification of appropriate units in chemicalquantification such as µg/1, µg/g, etc., instead ofmixing ratios such as ppb or ppm.

Some information, such as characterization of thesite or the contaminants of concern, may have beengiven in other sections of a report such as an RI orAction Memorandum. If so, the information can bereferenced; however, the analyst may wish tosummarize such information in the ecologicalassessment section.

6.1 Specify the Objectives of theAssessment

As discussed in Section 5.1, an ecological assessmentmay be undertaken for a variety of reasons, fromevaluating the threat posed by a site to examiningthe effects of remedial alternatives. For example, fortwo sites evaluated by EPA’s EnvironmentalResponse Team, the assessment objectives werestated as follows:

The main objective of this. . . investigation was togenerate data that could be utilized for thedetermination of site cleanup criteria for thecreosote contaminated soils and sediments in thefloodplain of the Creek.

The objective of this study was to determine if thearsenic compounds. present in the water andsediments of the River watershed

are resulting in an adverse ecological impact. Thedata collected [were] utilized in conjunction withexisting data to determine the bioavailabilityand toxicity of arsenic contamination to theresident aquatic biological communities, and [to]quantitatively assess impacts.

6.2 Define the Scope of the Investigation

This section of the report should describe the kindand amount of information that was collected in thestudy. The analyst should describe the data in termsof the physical, biological, and chemical parametersmeasured , e s t ima ted , o r ca lcu la ted in theassessment. It is also important to specify the timeframe of the study:

- Over what time period(s) and in what season(s)were the data collected?

- At what time intervals were samples taken?

- Were the data used to assess current effects orpast damage, or to predict future scenarios?

The discussion gives the reader a clear indication oft h e n a t u r e , d e p t h , a n d b o u n d a r i e s o f t h einvestigation. Was the assessment, or the data usedin the assessment, based on long-term studies of thesite and its surroundings or do the data provide a“snapshot” of the site in a restricted time period? Wasthe sampling extensive or limited to specific areas?Are the analyses reasonably straightforward or areconsiderable inferences and professional judgmentsinvolved?

6.3 Describe the Site and Study Area

In this section, the analyst should provide a physicaldescription of the site at a level of detail appropriateto the scope of the assessment. The study area for anecological assessment may extend well beyond theboundaries of the area in which hazardous wasteshave been stored or released. For example, dependingon the available pathways for exposure and thehabitats potentially exposed to contamination, thearea under investigation might include portions ofseveral tributaries of a potentially affected river, a

49

wetland downhill or downstream from a releasesource, or a wildlife refuge within the same drainagebasin as a waste site.

The description should include the size of the area (inmetric units) within the physical boundaries definedfor the assessment and the size of physical featuressuch as stream reaches, roads, wetlands, or forestedareas. The report should provide a map of the area,showing all physical features at a minimum resolu-tion equivalent to a 7.5' USGS quadrangle map,marked to show any changes to the topography up tothe present time. This map should include allpotentially affected areas linked to the contaminatedzone by pathways of concern through any media,sampling locations, and any reference areas selectedfor the investigation. An example of such a map isgiven in Figure 6.1.

A brief description of the contamination that led tolisting of the site, or a reference to such a descriptionshould be included, giving dates where possible.

The description of the site and study area shouldprovide a full accounting of the ecosystems andpopulations potentially exposed to contamination.This may be accomplished with a narrat ivedescription of each habitat (e.g., oak-hickory forest,Spartina salt marsh, etc.), accompanied by lists ortables of species collected or observed there. Theresident and transient flora and fauna should bedescribed, or if catalogued, the table can bereferenced. Where relevant, it should be noted if acited species is:

- Resident, breeding, or a rare or frequenttransient (e.g., migratory waterfowl),

- Endangered or threatened, or

- A natural resource trustee concern.

The significance, uniqueness, or protected status ofpotentially exposed ecosystems (as discussed inChapter 5) should also be noted and documented.

Other information with possible bearing upon theecological characteristics of the site should beprovided, such as current or projected land uses;p rox imi ty to popu la t ion cen te r s , i ndus t ry ,agriculture, or hunting areas; and special climaticconditions affecting movement, availability, oreffects of contaminants.

Finally, the site description should include narrativecharacterizations of:

- Likely or presumed exposure pathways, such assurface water, air, soils, sediments, or vegetation;and

- Any read i ly obse rved e f fec t s po ten t i a l lyattributable to the site, such as stressed or deadvegetation, fish kills, or unusual changes inspecies composition or distribution in a habitat.

6.4 Describe Contaminants of Concern

The ecological assessment should specify whichcontaminants at a site are of particular concern froman ecological perspective. This list may differsomewhat from those contaminants that raise ques-tions about human health risks. For example, a givenchemical may exhibit low toxicity toward mammalsbut be highly toxic to fish, invertebrates, or plants.The fate of a contaminant in the environment maymake it unavailable for human exposure while in-creasing exposure for other organisms. For instance,a chemical that is found to be adsorbing to soil andsediment particles may pose little risk to humans,but may cause considerable disruption of terrestrialvegetation or benthic invertebrates.

Results of chemical analyses should be presented intabular form, identifying compounds and the mediain which they were found. If tables of data from thehuman health evaluation are used by reference, it isimportant to report measurements of parametersaffecting the toxicity to biota, such as alkalinity ortotal organic carbon. It is important to note thesource of all analytical data, including laboratory,CLP certification, sampling and analytical method,and date of analysis. Data may be summarized, butboth the mean and range should be included, alongwith an explanation of how and why calculationswere made. The report should explain how non-detects, replicates, duplicates, etc. were treated in thestatistical analysis. All sample data should beaccounted for: infrequency of detection (rarity) is anunacceptable explanation for culling a particulardata item from the sample. The report shoulddescribe both laboratory and field analysis ofcontaminants, along with variances from detectionlimits that affect the applicability of the data to thestudy.

6.5 Characterize Exposure

This section should identify actual and potentiale x p o s u r e p a t h w a y s , t a k i n g i n t o a c c o u n tenvironmental fate and transport through bothphysical and biological means. The analyst shouldconsult the Superfund Exposure Assessment Manualand technical specialists to make sure that all likelyexposure pathways have been considered. Indiscussing the investigation of exposure pathways,the report should describe each pathway bychemical(s) and media involved, and identify thepathway in space and time with respect to the siteand the period of investigation. If contaminantconcentrations and effects data (such as toxicity testsor population studies) correspond to identified

50

Figure 6.1 Example of study area map.

pathways by spatial or temporal gradient, theirpresentation should demonstrate the correlation.

If sampling stations have been selected to measureconcentrations of contaminants along likely exposurepathways, the sampling data should be presented insuch a way as to allow the reader to see quickly therelationship between a sample’s location and itscontaminant levels. For instance, stations can benumbered in a sequence that indicates their relativedistance from the source of contamination, as shownon a map of the study area. Another method is to

present the data on a scatter diagram, in whichsampling locations are shown as points on a graphwith distance from the source given on the X-axis andconcentrations on the Y-axis. Ideally, concentrationsof key contaminants should be displayed in graphform with geographic locations indicated (see Figure6.2) or on a map (see Figure 6.3).

Results of toxicity tests may also be effectivelydisplayed using maps. For example, in a study of theeffects of PCBs and other contaminants at aNortheastern site, the researchers showed the results

51

Figure 6.2 Graphic display of contaminant concentration.

of toxicity testing on a map of the affected area(Figure 6.4). This type of presentation makes readilyapparent the relative hazard associated withdifferent locations.

If such gradients are not apparent , or arecontradicted by other data, the analyst should discussthe possible reasons for the discrepancy in the report.If exposure pathways are modeled, the report shouldclearly state the limiting assumptions of the model(s)used. A full reference for every model used in the as-sessment should be included. The analyst shouldcharacterize the uncertainty associated with allparameters that are measured or modeled, andspecify statistical significance levels for quantitativeresults.

If the analysis uses data from toxicity tests,populat ion s tudies , o r o the r e f fec t s - re la tedinvestigations, to demonstrate that exposure hasoccurred, the report should carefully explain thelimitations of the data. For instance, the site andreference area might differ in terms of the degree ofphysical disturbance, which may account for some ofthe observed effects. If toxicity test results arepresented in the form of LD50S or ED50S, they shouldbe shown graphically on a log probit scale.

6.6 Characterize Risk or Threat

In characterizing risks or threats to environmentalreceptors associated with Superfund sites, theanalyst should try to answer the following questions:

- What is the probability that an adverse effect willoccur?

- What is the magnitude of each effect?

- What is the temporal character of each effect(transient, reversible, or permanent)?

- What receptor populations or habitats will beaffected?

Depending on the assessment objectives and thequality of the data collected, the answers to thesequest ions wil l be expressed quanti tat ively,qualitatively, or a combination of the two.

If water quality or other criteria have been exceededat a site, this may be sufficient in some cases tojustify remediation. In presenting the data, theanalyst should document the number and location ofsampling results that exceed the acute and/or chronic

52

Figure 6.3 Map display of contaminant concentrations.

criteria for the protection of the species and habitat of - Field surveys of receptor populations, andconcern at a site. The number of exceedences can becompared to the number of total measurements foreach contaminant in a table. In addition, thelocations of all exceedences and the locations of allmeasurements can be shown with different symbolson a map. Use of a map can be especially helpful ifcontaminant concentrations form a reasonably cleargradient leading away from the source.

Beyond cri teria exceedences, however, r iskcharacterization is most likely to be a weight-of-evidence judgment. The analyst should present asummary of the risk-related data concerning the site,including

- Environmental contaminant concentrations,

- Contaminant concentrations in biota,

- Toxicity test results,

- Literature values of toxicity,

- Measures of community structure and ecosystemfunction.

If the contaminants at the site are exerting a cleareffect, the data from all of these studies will, onbalance, support the conclusion that an effect isoccurring. If the data are ambiguous, the analystshould try to discern the reasons for conflicting re-sults and present those reasons along with therationale for the conclusion reached.

Ecological r isk characterizat ion entai ls bothtemporal and spatial components. In describing thenature and probability of adverse effects, the analystshould also consider such questions as:

- How long will the effects last if the contaminantsare removed? How long will it take for receptorpopulations to recover from the effects of the

53

Figure 6.4a Map display of toxicity test results.

54

Figure 6.4b Map display of toxicity test results.

contaminants? Will there be intergenerationaleffects?

Will the contaminants move beyond the currentarea of study through biotic transport? Whateffect will remediation have on this movement?

If there are community and ecosystem effects oft h e o n t a m i n a t i o n , i s r e m o v a l o f t h econtaminants sufficient to restore communitystructure and ecosystem function? If not, whatelse will be needed?

How do the data on exposure and observed orpredicted effects relate to the rapidity of responserequired? Which responses are requiredimmediately? Which can or should be undertakenlater?

What limits will proposed remediation ormitigation actions place on future options forfurther remediation, follow-up assessment, andresource use?

*

Questions like these will most likely be answerableonly in narrative form, as an expression of bestprofessional judgment by a qualified ecologist.Nonetheless, they lie at the heart of ecologicalassessment. Many populations and ecosystemsexhibit considerable resilience in the face ofdisturbance; in fact, change is more common inecosys tems than s t ab i l i t y . Popu la t ions a recontinually increasing and decreasing due to naturalcycles and chance occurrences. In many situations,when a source of contamination is removed, naturalsystems will rapidly recover their former appearance.Hence, for the same amount of chemical released, therisk associated with an acutely toxic but short-livedchemical may be considered important but less sothan a moderately toxic chemical that is highlypersistent.

6.7 Describe the Derivation ofRemediation Criteria or Other Usesof Quantitative Risk Information

If water quality or other criteria are available forcomparison to observed concentrations of con-taminants, the analyst should try to show the dataalong with applicable criteria so that exceedences areeasily apparent. Table 6.1 is an example of this kindof presentation. If criteria exceedences occur along aclearly identified gradient, the data may best bepresented in a map.

Remediation criteria may also be derived from riskinformation developed for use under otherenvironmental statutes, such as the Toxic SubstancesControl Act or the Federal Insecticide, Fungicide andRodenticide Act. If the report recommends remedi-ation criteria based on such information, the analyst

Table 6.1. Example of Presentation of Criteria Exceedences

Mean and Maximum Surface Water Concentrations (µg/I) in On-Site Lakes at a Landfill

Observed Water QualityConcentrations Criteria a

Chemical Mean Maximum Acute Chronic

Ammonia 160* 6,800* 20 20

Copper 16 50* 48 29

Cyanide NE 0.04* ND ND

Iron 125 1,300* 300 300

Zinc 20 150* 30 30

Phenol NE 2.1* 1 1

a Federal, state, or county criteria used as availableKey NE = Not evaluated

ND = No detectable amount permitted= Criteria exceeded

should give a full reference citation for the source ofreference doses, standards, or risk assessments use incalculating the criteria. In addition, the analystshould provide an explanation of, or reference for, thecalculation method used to develop the criteria.Equations and parameters (such as exposure factors)used in the calculations should be provided in the textor referenced.

6.8 Describe Conclusions and Limitationsof Analysis

Assessment of Superfund sites will depend primarilyon the weight of evidence supporting particularconclusions, since ecological effects seldom occur inisolation from other stresses. To accomplish this, itmay be necessary to use a variety of measurements inan effort to establish that a trend is likely in the data.

For example, in a study of an arsenic-contaminatedsite and a nearby river system, the analystscompared several different indices of speciesdiversity for benthic invertebrates (Figure 6.5) andexamined differences in the trophic structure at thevarious sampling locations (Figure 6.6). Analystsnext combined these data with information oncontaminant concentrations and toxicity tests. Theyconcluded that arsenic concentrations in the streamsediments were significantly affecting benthic inver-tebrates downstream from the contamination source.

In presenting conclusions from an ecologicalassessment, the analyst should address the degree ofsuccess in meeting the objectives of the evaluation.The report should present each conclusion, alongwith the items of evidence that support and fail tosupport the conclusion, and the uncertainty

56

accompanying the conclusion. Analysts should alsodesc r ibe f ac to r s tha t l imi ted o r p reven teddevelopment of definitive conclusions.The process of assessing ecological effects is one ofestimation under conditions of uncertainty. Toaddress this necessary reality, the analyst shouldprovide information that indicates the degree ofconfidence in the data used to assess the site and itscontaminants. In summarizing assessment data, theRPM or OSC should specify sources of uncertainty,including:

- Variance estimates for all statistics;

- Assumptions underlying use of statistics, indices,and models;

- The range of conditions under which models orindices are applicable; and

- Narrative explanations of other sources ofpotential error in the data (e. g., unexpectedweather conditions, unexpected sources ofcontamination).

Ecological assessment is, and will continue to be, aprocess combining careful observation, datacollection, testing, and professional judgment. Bycarefully describing the sources of uncertainty, theanalyst will strengthen the confidence in the con-clusions that are drawn from the analysis.

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