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ASCE Manuals and Reports on Engineering Practice No. 99

Environmental SiteCharacterization andRemediation Design

Guidance

Prepared by theRemedial Investigation/Feasibility Study/Remediation Design

Manual Task Committee of theEnvironmental Engineering Division of the

American Society of Civil Engineers

Published by

f^ ̂ S^̂ JET Am0ncan Society^•vvE of Civil Engineers

1801 Alexander Bell DriveReston, Virginia 20191 -4400



Abstract: Soils and groundwater contaminated by hazardous compounds are common resultsof industrial activity. They have become costly burdens for site owners and contentious politicaland regulatory issues for surrounding communities. Environmental Site Characterization andRemediation Design Guidance provides information for consultants, engineers, site owners,insurers, realtors, and facilities managers who must evaluate and remediate these chemicalhazards. It describes procedures for site characterization, linking it to a related ASCE manual,Environmental Site Investigation. It reviews methods for evaluating the array of available remedi-ation techniques and selecting the one that will provide the best combination of reliability andlow cost for the site of interest. It outlines an organized and rational approach to remediationdesign. Regulatory compliance and responsibility to the community are emphasized, but withattention to approaches that allow remediation to be completed at minimum cost.

Library of Congress Cataloging-in-Publication Data

Environmental site characterization and remediation design guidance/ prepared by the Rl/FS/RDManual Task Committee of the Environmental Engineering Division of the American Society ofCivil Engineers.

p. cm.—(ASCE manuals and reports on engineering practice ; no. 99)Includes bibliographical references and index.ISBN 0-7844-0439-91. Hazardous waste site remediation. 2. Hazardous waste sites—Evaluation. 3. Hazardous

wastes—Risk assessment. I. American Society of Civil Engineers. Environmental EngineeringDivision. RI/FS/RD Manual Task Committee. II. Series.TD1052.E579 1999628.5—dc21 99-32028

CIP

The material presented in this publication has been prepared in accordance with generallyrecognized engineering principles and practices, and is for general information only. This infor-mation should not be used without first securing competent advice with respect to its suitabilityfor any general or specific application.

The contents of this publication are not intended to be and should not be construed to be astandard of the American Society of Civil Engineers (ASCE) and are not intended for use as a ref-erence in purchase of specifications, contracts, regulations, statutes, or any other legal document.

No reference made in this publication to any specific method, product, process, or serviceconstitutes or implies an endorsement, recommendation, or warranty thereof by ASCE.

ASCE makes no representation or warranty of any kind, whether express or implied, con-cerning the accuracy, completeness, suitability, or utility of any information, apparatus, prod-uct, or process discussed in this publication, and assumes no liability therefore.

Anyone utilizing this information assumes all liability arising from such use, including butnot limited to infringement of any patent or patents.

Photocopies: Authorization to photocopy material for internal or personal use under circum-stances not falling within the fair use provisions of the Copyright Act is granted by ASCE tolibraries and other users registered with the Copyright Clearance Center (CCC) TransactionalReporting Service, provided that the base fee of $8.00 per chapter plus $.50 per page is paiddirectly to CCC, 222 Rosewood Drive, Danvers, MA 01923. The identification for ASCE Books is0-7844-0439-9/99/$8.00 + $.50 per page. Requests for special permission or bulk copying shouldbe addressed to Permissions & Copyright Department, ASCE.

Copyright © 1999 by the American Society of Civil Engineers.All Rights Reserved.Library of Congress Catalog Card No: 99-32028ISBN 0-7844-0439-9Manufactured in the United States of America



MANUALS AND REPORTSON ENGINEERING PRACTICE

(As developed by the ASCE Technical Procedures Committee, July 1930, andrevised March 1935, February 1962, and April 1982)

A manual or report in this series consists of an orderly presentation offacts on a particular subject, supplemented by an analysis of limitations andapplications of these facts. It contains information useful to the averageengineer in his everyday work, rather than the findings that may be usefulonly occasionally or rarely. It is not in any sense a "standard/' however; noris it so elementary or so conclusive as to provide a "rule of thumb" for non-engineers.

Furthermore, material in this series, in distinction from a paper (whichexpressed only one person's observations or opinions), is the work of a com-mittee or group selected to assemble and express informaton on a specifictopic. As often as practicable the committee is under the direction of one ormore of the Technical Divisions and Councils, and the product evolved hasbeen subjected to review by the Executive Committee of the Division orCouncil. As a step in the process of this review, proposed manuscripts areoften brought before the members of the Technical Divisions and Councilsfor comment, which may serve as the basis for improvement. When pub-lished, each work shows the names of the committees by which it was com-piled and indicates clearly the several processes through which it has passedin review, in order that its merit may be definitely understood.

In February 1962 (and revised in April 1982) the Board of Direction votedto establish:

A series entitled "Manuals and Reports on Engineering Practice,"to include the Manuals published and authorized to date, futureManuals of Professional Practice, and Reports on EngineeringPractice. All such Manual or Report material of the Society wouldhave been refereed in a manner approved by the Board Commit-tee on Publications and would be bound, with applicable discus-sion, in books similar to past Manuals. Numbering would be con-secutive and would be a continuation of present Manualnumbers. In some cases of reports of joint committees, bypassingof Journal publications may be authorized.



MANUALS AND REPORTSOF ENGINEERING PRACTICE

No. Title No. Title

13 Filtering Materials for SewageTreatment Plants

14 Accommodation of Utility PlantWithin the Rights-of-Way of UrbanStreets and Highways

34 Definitions of Surveying andAssociated Terms

35 A List of Translations of ForeignLiterature on Hydraulics

37 Design and Construction of Sanitaryand Storm Sewers

40 Ground Water Management41 Plastic Design in Steel: A Guide and

Commentary45 Consulting Engineering: A Guide for

the Engagement of EngineeringServices

46 Pipeline Route Selection for Rural andCross-Country Pipelines

47 Selected Abstracts on StructuralApplications of Plastics

49 Urban Planning Guide50 Planning and Design Guidelines for

Small Craft Harbors51 Survey of Current Structural Research52 Guide for the Design of Steel

Transmission Towers53 Criteria for Maintenance of Multilane

Highways54 Sedimentation Engineering55 Guide to Employment Conditions for

Civil Engineers57 Management, Operation and

Maintenance of Irrigation andDrainage Systems

59 Computer Pricing Practices60 Gravity Sanitary Sewer Design and

Construction62 Existing Sewer Evaluation and

Rehabilitation63 Structural Plastics Design Manual64 Manual on Engineering Surveying65 Construction Cost Control66 Structural Plastics Selection Manual67 Wind Tunnel Studies of Buildings and

Structures68 Aeration: A Waste water Treatment

Process69 Sulfide in Wastewater Collection and

Treatment Systems

70 Evapotranspiration and IrrigationWater Requirements

71 Agricultural Salinity Assessment andManagement

72 Design of Steel Transmission PoleStructures

73 Quality in the Constructed Project: AGuide for Owners, Designers, andConstructors

74 Guidelines for Electrical TransmissionLine Structural Loading

75 Right-of-Way Surveying76 Design of Municipal Wastewater

Treatment Plants77 Design and Construction of Urban

Stormwater Management Systems78 Structural Fire Protection79 Steel Penstocks80 Ship Channel Design81 Guidelines for Cloud Seeding to

Augment Precipitation82 Odor Control in Wastewater

Treatment Plants83 Environmental Site Investigation84 Mechanical Connections in Wood

Structures85 Quality of Ground Water86 Operation and Maintenance of

Ground Water Facilities87 Urban Runoff Quality Manual88 Management of Water Treatment Plant

Residuals89 Pipeline Crossings90 Guide to Structural Optimization91 Design of Guyed Electrical

Transmission Structures92 Manhole Inspection and

Rehabilitation93 Crane Safety on Construction Sites94 Inland Navigation: Locks, Dams, and

Channels95 Urban Subsurface Drainage96 Guide to Improved Earthquake

Performance of Electric PowerSystems

97 Hydraulic Modeling: Concepts andPractice

99 Environmental Site Characterizationand Remediation Design Guidance



COMMITTEE'S PURPOSE AND OFFICERS

Environmental Engineering Division, Remedial Investigation/FeasibilityStudy/Remediation Design Manual Task Committee

This manual was written by the Remedial Investigation/Feasibility Study/Remediation Design (Rl/FS/RD) Manual Task Committee of the Environ-mental Engineering Division of the American Society of Civil Engineers.The Task Committee's purpose was to prepare a manual describing theappropriate procedures to design the remediation of sites contaminatedwith hazardous materials.

Title Member Affiliation

Chair Joseph S. Devinny, Environmental Engineering ProgramPh.D. Civil Engineering Department

University of Southern CaliforniaLos Angeles, California

Vice Chair Khalique Khan Sverdrup CorporationCosta Mesa, California

Secretary Daniel E Buss Camp Dresser & McKee, Inc.Milwaukee, Wisconsin

Planner Victor E Medina Washington State University-Tri-CitiesRichland, Washington

Major Contributors

The following individuals were major contributors to the preparationand final production of this manual. The lead authors prepared the prelimi-nary drafts of their assigned chapters as recognized experts in their disci-plines. These chapters were given an initial internal review, revised, given a

v



VI ENVIRONMENTAL SITE CHARACTERIZATION AND REMEDIATION DESIGN

second internal review, and revised again. The draft was then reviewed byall the members of the committee, and comments were incorporated intothe draft. The appointed ASCE Blue Ribbon Committee, with membershipfrom throughout the country, critiqued the draft, and those comments wereincorporated to produce the final manuscript. Wendy Cohen, from the Cali-fornia Regional Water Quality Control Board, edited the final draft of themanuscript.

Lead Authors

Chapter 1 Joseph S. Devinny

Sidney B. Garland II

Chapter 2 Julio NunoPatrick S.Sullivan

Daniel F. Buss

Raymond D'Hollander

Chapter 3 Kenneth H. Lister

M'balia Tagoe

Chapter 4 John April

Charlie Johnson

Khalique Khan

Chapter 5 David P. Williams

Blue Ribbon Committee

Carol Whitlock

Robert Williams

University of Southern CaliforniaLos Angeles, California

Lockheed Martin Energy Systems, Inc.Oak Ridge, Tennessee

SCS EngineersLong Beach, California

Camp Dresser & McKee, Inc.Milwaukee, Wisconsin

Blasland, Bouck & Lee, Inc.Syracuse, New York

SCS EngineersLong Beach, California

Bechtel Jacobs CompanyOak Ridge, Tennessee

Bechtel Hanford, Inc.Richland, Washington

Bechtel Jacobs CompanyOak Ridge, Tennessee

Sverdrup CorporationCosta Mesa, California

U.S. Army Corps of EngineersAlaska DistrictAnchorage, Alaska

Merriam, Kansas

ATSDRNorcross, Georgia



ENVIRONMENTAL SITE CHARACTERIZATION AND REMEDIATION DESIGN vu

Richard Reis, EE. EmconBothell, Washington

Yee Cho, EE. CDW ConsultantsFramingham, Massachusetts

F. Edward Reynolds, Jr., The Reynolds GroupEE. Tustin, California

Tom Card Environmental Management ConsultingFall City, Washington

Fred Boecher U.S. Army Environmental CenterAberdeen Froving Ground, Maryland

Bijay Eanigrahi Remedial Engineering and ScienceOrlando, Florida

Technical Editors

Joseph S. Devinny, Fh.D. University of Southern CaliforniaLos Angeles, California

Wendy L. Cohen California Regional Water Quality Control BoardCentral Valley RegionSacramento, California

Daniel F. Buss Camp Dresser & McKee Inc.Milwaukee, Wisconsin

Khalique Khan, Eh.D. Sverdrup CorporationCosta Mesa, California

Stanley Klemetson Anderson Consulting GroupRoseville, California



This page intentionally left blank



TABLE OF CONTENTS

ACRONYMS xii

1 INTRODUCTION 11.1 Purpose 11.2 Background 11.3 Environmental Law 2

1.3.1 Introduction 21.3.2 Development of Environmental Laws and Regulations 31.3.3 Remediation Laws 31.3.4 Other Laws 41.3.5 Local Enforcement 4

1.4 Choosing an Environmental Consultant 51.5 Remediation Planning 51.6 Community Involvement 71.7 References 11

2 SITE CHARACTERIZATION 132.1 Project Planning 132.2 Evaluation of Historical Data 172.3 Site Characterization Methods 19

2.3.1 Physical Characteristics 202.3.2 Contamination Source Characteristics 202.3.3 Environmental Data for Public Health Decisions 212.3.4 Nature and Extent of Contamination 212.3.5 Analysis, Data Evaluation, and Reporting 30

2.4 Human Health Risk Assessment 312.4.1 Introduction 312.4.2 Typical Role of Health Risk Assessment 312.4.3 Planning for an HRA 322.4.4 Protocols for a Baseline HRA 332.4.5 Evaluation of Site Characterization Information 342.4.6 Identification and Selection of Chemicals of Potential Concern 372.4.7 Exposure Assessment 38

ix



x ENVIRONMENTAL SITE CHARACTERIZATION AND REMEDIATION DESIGN

2.4.8 Toxicity Assessment 402.4.9 Risk Characterization 442.4.10 Uncertainty Analysis 45

2.5 Ecological Risk Assessment 462.5.1 Introduction 462.5.2 Ecological Risk Assessment in the Site Mitigation Process 462.5.3 Protocols for an Ecological Risk Assessment 46

2.6 Use of Human Health and Ecological Risk Assessment Information 482.6.1 Development of Preliminary Remediation Goals 492.6.2 Risk Information in Screening and Selection of Alternatives 492.6.3 Selection of Final Remedial Alternative 502.6.4 Verification of Successful Remediation 502.6.5 Risk Management 50

2.7 Treatability Studies 512.8 Site Characterization Report 522.9 References 53

3 EVALUATION OF REMEDIATION ALTERNATIVES 553.1 Introduction 553.2 Establishment of Remedial Action Objectives and Criteria 56

3.2.1 Review of Past Decisions 573.2.2 Statutory Framework and Scope and Schedule Limitations 573.2.3 Applicable or Relevant and Appropriate Requirements (ARARs) .. 573.2.4 Remedial Action Objectives 573.2.5 Community Involvement 58

3.3 Development and Screening of Remediation Alternatives 583.3.1 General Response Actions 593.3.2 Identification of Volumes and Impacted Areas 603.3.3 Identification and Screening of Technologies 603.3.4 Evaluation of Technologies 613.3.5 Assembly of Technologies as Alternatives 653.3.6 Screening of Alternatives 67

3.4 Evaluation of Alternatives 713.4.1 Detailed Analysis of Alternatives 713.4.2 Preparation of Remediation Alternatives Evaluation Report 77

3.5 Remedy Selection 793.5.1 Proposed Remediation Plan 793.5.2 Decision Documents (Record of Decision) 79

3.6 References 80

4 REMEDIATION DESIGN 834.1 Introduction 834.2 Project Planning 83

4.2.1 Statement of Work 834.2.2 Engineer Selection 854.2.3 Design Initiation 864.2.4 Review of Existing Data 864.2.5 Project Design Criteria 874.2.6 Health and Safety Plan 87



ENVIRONMENTAL SITE CHARACTERIZATION AND REMEDIATION DESIGN xi

4.2.7 Emergency Contingency Plans 874.2.8 Community Relations and Involvement Plans 884.2.9 Permits and Site Access 894.2.10 Decision Documents, Regulatory Acceptance, and Comments . . . 90

4.3 Conceptual Design 914.3.1 Design Investigations 914.3.2 Value Engineering Studies 914.3.3 Description of Design Criteria 924.3.4 Proposed Remediation Plan 934.3.5 Suggested Format 93

4.4 Detailed Design 944.4.1 Design Reviews 944.4.2 Plans and Specifications 944.4.3 Design Analysis and Calculations 954.4.4 Construction Cost Estimates and Estimated Quantities 964.4.5 Construction Schedule 974.4.6 Contracting Mechanisms 974.4.7 Designing with Limited Data 100

4.5 Construction and Implementation 1014.5.1 Engineering Services during Construction 1014.5.2 Environmental and Construction Permitting 1024.5.3 Contract Schedule 1034.5.4 Contract Administration 1034.5.5 Change Orders and Claims 1044.5.6 Remedial Action Post-Construction Report 105

4.6 References 105

5 EXPEDITED PROCESSES 1075.1 Introduction 1075.2 Streamlining 108

5.2.1 Relationships with Agencies 1105.2.2 Presumptive Remedies and Treatability Studies 1105.2.3 Flexibility Ill5.2.4 Investigation toward Remediation 1125.2.5 Preapproved Techniques 1135.2.6 Investigation by Remediation 1135.2.7 Intrinsic Remediation 1135.2.8 Brownfields 115

5.3 Quick Tools 1155.3.1 Data-Gathering Tools 1165.3.2 Data-Development Tools 1195.3.3 Data Analysis 120

5.4 Early Action 1205.4.1 Early Action Example 1225.4.2 Removals and Interim Actions 122

5.5 References 125

INDEX 127



ACRONYMS

ARARs Applicable or Relevant and Appropriate RequirementsGDI chronic daily intakeCERCLA Comprehensive Environmental Response, Compensation, and

Liability ActCOPCs chemicals of potential concernDQO data quality objectivesEPA U.S. Environmental Protection AgencyEPC exposure point concentrationESC environmental site characterizationHRA health risk assessmentHSWAs Hazardous and Solid Waste AmendmentsNCP National Contingency PlanNEPA National Environmental Policy Act of 1969NPL National Priorities ListO&M operations and maintenanceOSHA U.S. Office of Safety and Health AdministrationPRGs preliminary remediation goalsQA/QC quality assurance/quality controlRAB restoration advisory boardRCRA Resource Conservation and Recovery ActRI remedial investigationROD record of decisionSOW statement of workSARA Superfund Amendments and Reauthorization ActVE value engineeringVISITT Vendor Information System for Innovative Treatment Technolo-

giesVOCs volatile organic compounds

XII



Chapter 1

INTRODUCTION

1.1 PURPOSE

This manual describes the characterization and design processes forcleanup of sites contaminated by hazardous materials. It is intended forindividuals and companies that become responsible for contaminated sitecharacterization and remediation but do not have the experience or exper-tise of specialized professionals.

Site cleanup includes remediation planning; site characterization; evalua-tion and selection of remediation alternatives; and remediation design, con-struction, and implementation. This manual summarizes site characteriza-tion, then details evaluation of alternatives and remediation design. Becauseall sites are different and simple cleanup procedures may be possible inmany cases, a chapter is included that describes expedited processes. A pre-vious manual, the Environmental Site Investigation Guidance Manual (ASCE1996), provides a more detailed description of the investigation step. It isanticipated that a future ASCE manual will discuss remedial constructionand implementation.

1.2 BACKGROUND

Ideally, environmental management prevents significant contaminationof the environment (Figure 1-1). Poor environmental management may leadto contamination of soils and groundwater. If the contamination threatensthe environment or public health, remediation will frequently be required.Unfortunately, past hazardous materials handling and hazardous wastetreatment and disposal were often done carelessly. Wastes were initiallydumped without treatment. Later, wastes were treated, and processchanges were made to reduce the amounts produced. Now, emphasis is

1



ENVIRONMENTAL SITE CHARACTERIZATION AND REMEDIATION DESIGN

placed on material substitution and process modification to avoid the use ofenvironmentally dangerous materials.

Careless waste treatment and disposal have left a legacy of contaminatedsoil, water, and biota. These frequently pose human health and ecologicalrisks and damage valuable natural resources. The goals of the remediationprocess are to gain control of contaminated sites, to reduce risks to accept-able levels, and to restore resource value.

1.3 ENVIRONMENTAL L AW

1.3.1 Introduction

In the United States, the beginning of the current environmental move-ment is associated with the National Environmental Policy Act of 1969(NEPA). NEPA states that the nation's environmental goal is to recognize

FIGURE 1-1. Ideal Environmental Management Process.

2



INTRODUCTION 3

"the profound impact of human activity on the interrelations of all compo-nents of the natural environment,... [the principle that] each person shouldenjoy a healthful environment... and [the need] to contribute to the preser-vation and enhancement of the environment/7 NEPA requires private com-panies and federal agencies to consider environmental consequences intheir decision-making processes.

Since the enactment of NEPA, many other federal environmental lawshave been passed to address specific environmental problems or contami-nants. In addition, many have been enacted at the state and local level, sothat cleanup is often controlled by a complex maze of interacting regulations.

1.3.2 Development of Environmental Laws and Regulations

Environmental statutes enacted by the federal government typicallyrequire a federal agency, usually the U.S. Environmental Protection Agency(EPA), to develop implementing regulations. Proposed regulations are pub-lished in the Federal Register for public comment. When the comments areresolved, the final regulations are published in the Federal Register and havethe force of law. Updated regulations are published yearly in the Code of Fed-eral Regulations. State and local governments generally use similar proce-dures to designate responsible agencies and involve the public.

1.3.3 Remediation Laws

The two federal environmental laws that provide the legal foundation forsite characterization and remediation are the Comprehensive Environmen-tal Response, Compensation, and Liability Act of 1980 (CERCLA) and theResource Conservation and Recovery Act of 1976 (RCRA) (GovernmentInstitutes 1993). CERCLA was passed to deal with the human health andenvironmental risks posed by abandoned waste disposal sites and by aban-doned contaminated industrial sites. CERCLA gives EPA the authority toremediate these abandoned sites and to allocate the costs to those who areor were responsible. The law also established the "Hazardous SubstancesSuperfund," financed by a tax on the petroleum and chemical industries. Ifresponsible parties cannot be found to pay for the remediation, or if negotia-tions with the responsible parties are lengthy, EPA can use the fund to payfor cleanup. In 1986, the Superfund Amendments and Reauthorization Act(SARA) was passed, extensively amending CERCLA. CERCLA does notspecify cleanup standards but delegates the ability to do so to responsibleagencies. It requires remediation to comply with all Applicable or Relevantand Appropriate Requirements (ARARs) established by state, federal, andlocal environmental laws, standards, and requirements.

RCRA was passed in 1976 and amended in 1984 by the Hazardous andSolid Waste Amendments (HSWA). The purpose of RCRA is to provide reg-



4 ENVIRONMENTAL SITE CHARACTERIZATION AND REMEDIATION DESIGN

ulations governing the management of hazardous wastes from the point ofgeneration to final disposal. Whereas RCRA is oriented primarily towardgenerators, transporters, and disposers of hazardous waste from active facil-ities, there is a corrective action program that requires the owners and oper-ators of hazardous waste treatment, storage, and disposal facilities to cleanup releases of hazardous constituents. This program is similar to the CER-CLA program for remediation.

Even though much attention is given to CERCLA and RCRA, many sitecleanups are done under the authority of state regulations, which may varyin some ways. Moreover, many projects are done voluntarily, with only min-imal regulatory scrutiny. Many companies are carefully examining theirown properties and pursuing voluntary cleanups where appropriatebecause the reduced regulatory involvement can substantially reduce theexpenditures and time required. Finally, petroleum-contaminated sites arenot included in CERCLA or RCRA; they are regulated separately.

An important aspect of any cleanup is the choice of the acceptable con-centrations of contaminant to be left at the site—basically, "How clean isclean?7' This requires work with various government agencies and practitio-ners with various special skills and is frequently a negotiated site-specificaspect of the cleanup project.

1.3.4 Other Laws

The Clean Air Act of 1970 specifies ambient air quality standards and con-trol technologies for emission sources. The Clean Water Act of 1977 controlsthe discharge of contaminants to surface water. The Safe Drinking Water Actof 1974 defines national drinking water standards. The Toxic SubstancesControl Act of 1976 regulates the manufacture, use, distribution, and dis-posal of chemical substances. It requires an assessment of a chemical's risksto human health and to the environment prior to use and sale.

In some cases, the Federal Insecticide, Fungicide, and Rodenticide Actapplies. Where the contamination has been released from an undergroundtank, federal regulations for underground storage tanks, authorized inSARA, apply. The conduct of site cleanup efforts must meet the regulationsof the Occupational Safety and Health Act of 1970 and the Emergency Plan-ning and Community Right to Know Act of 1986. Summaries and full copiesof these laws are available on the Web site maintained by EPA.

1.3.5 Local Enforcement

Site cleanups often must meet the requirements of local regulations andregulators. Because of the fire and explosion danger, work with under-ground storage tanks often must be approved by the local fire department.Refilling an excavation may require a grading permit from county or city



INTRODUCTION 5

building inspectors. Trucks that haul dirt from the site will be subject to reg-ulation and inspection by the highway patrol.

1.4 CHOOSING AN ENVIRONMENTAL CONSULTANT

The selection of an environmental consultant has much in common withselecting other consultants (AAEE 1995, ASCE 1981). The scope of workshould be carefully defined, and the procedures used in selecting the con-sultant should be objective. The primary factors to be considered are reputa-tion, registration, and qualifications. A consultant must have a good recordfor completing projects on time and on budget, evidence of appropriateexpertise, and a record of quality work. Advertisements may be found intrade journals, such as the newsletter of the local chapter of ASCE, but a ref-erence from a former client is the most valuable source of information.Because the performance of the consultant will determine the success of theproject, the consultant should be selected primarily for technical and busi-ness qualifications rather than low cost.

In some states, it is required that the consultant be a certified environ-mental professional or a professional engineer. A licensed contractor may berequired if remediation work is done based on a design provided by a pro-fessional engineer. Frequently, individuals working on the site are requiredto have specialized training in hazardous materials handling. These creden-tials, and others needed, should be verified.

1.5 REMEDIATION PLANNING

The approach to addressing the environmental problems at an active facil-ity will have a direct impact on public health and the environment. Carefulplanning is necessary to determine the best approach and should be initiatedimmediately on discovery of contamination (Figure 1-2). When the problemis on the premises of an active business, the discoverer should immediatelynotify the company representative responsible for environmental protectionand ensure that senior-level staff are made aware of the issues.

In turn, the person responsible for environmental matters should assessthe apparent severity of the situation and notify others who will be involvedin planning the remedial activity. Parties involved in initial response plan-ning could include the environmental manager, the safety manager, theoperations manager, legal counsel, and insurers. If the environmental prob-lem has regulatory implications, such as spill notification requirements, theappropriate regulatory agencies should be contacted immediately. In addi-tion, spill response procedures should be initiated immediately, as describedin existing contingency plans. All situations presenting imminent hazards to




FIGURE 1-2. Planning Sequence during the Environmental Response Process.



INTRODUCTION 7

public health and the environment should be addressed as quickly as possi-ble. The engineer may have an ethical responsibility to notify a regulatoryagency if the client does not take action when the contamination is recog-nized as immediately dangerous to life.

The response action must be planned, directed, and implemented toensure protection of public health and the environment. Immediate recog-nition of the environmental problem and its potential impact is essential.Protection of human health is first priority, and the response action mustaccomplish this goal (Table 1-1). Proper planning is essential to determinethe extent of contamination, methods to be applied, protocol to be followed,ARARs to be addressed, and steps to be taken to ensure all potentiallyimpacted parties are properly informed of the environmental issues. Properplanning will be the vehicle to ensure the response action is carried out andthat all issues are diligently addressed. Utilizing a well-planned approachwill maximize protection of human health and the environment whilereducing liability and unjustified bad publicity.

Ideally, much of the planning should be done in advance. Manufacturingfacilities or plants are required under RCRA and Office of Safety and HealthAdministration (OSHA) rules to prepare an Emergency Response Plan,including a contingency plan, that is distributed among potential localauthorities (e.g., fire marshal, department of environmental protection, andemergency response teams). Employees should be trained and familiar withthe plan. If the plan is in place, and if the actions it describes are promptlyinitiated when a spill occurs, the environmental impact and costs of the spillcan be minimized.

This manual describes aspects of the remediation process, with emphasison evaluation of remedial alternatives, remediation design, and expeditedprocesses (Figure 1-3). Although the exact terminology, documents, andprocedures may be peculiar to a specific regulatory agency, the stepsdescribed in this manual are generally sound and widely applicable.

1.6 COMMUNITY INVOLVEMENT

Community involvement should be part of the plan for site characteriza-tion and remediation work. Engineers and business owners are commonlywary of public involvement and uncomfortable with implementation ofpublic relations efforts. There have been many cases in which a contami-nated site has become the center of public controversy, generating unjusti-fied panic in the community and requirements for very expensive measuresthat make little genuine contribution to public health or environmentalquality. Site owners and their consultants fear that they may lose control of asite if public notification leads to journalistic sensationalism and politicalgrandstanding. Owners frequently take the extreme position that they want




TABLE 1-1. Elements for Consideration in Planning

Response time. If the environmental concern poses an environmental haz-ard to public health or the environment, the response must be imple-mented immediately to protect the public and the environment.

"Partnering" with regulatory agencies. The agency regulating the specificenvironmental concern must be notified, as required by applicable reg-ulations, within time to reasonably draw on the expertise of agency per-sonnel responsible for protecting the quality of the environment. It isessential to coordinate the response action with all appropriate regula-tory agencies to obtain agreement to the planned course of action andaccount for all criteria that must be addressed.

Protection of information. It is essential to respond to the environmentalconcerns to ensure protection of public health and the environment.However, it is also important to meet these primary goals using a pro-cess that prevents perceived or speculative problems that could createunnecessary harm to the financial and operational welfare of the prop-erty experiencing the environmental concern. Therefore, legal counselshould be sought for advice on managing the information.

Understanding the "big picture." The full situation and its ramificationsmust be thoroughly understood so that the environmental problem canbe addressed in the most expedient and efficient manner that protectshuman health and the environment.

Sensitivity issues. Many situations confronted in responding to the environ-mental concern will be politically sensitive, particularly the assignmentof risk and blame. Proper planning will evaluate the level of risk accu-rately and minimize unjustified public concerns.

Fatal flaws. Without adequate planning, situations involving responseactions to environmental concerns can manifest themselves and signifi-cantly impact the action taken. These fatal flaws or pitfalls to theresponse action can be legal issues or safety- and engineering- relatedissues. Proper planning can account for these potential flaws so they donot hinder the selected response action.

Continued on next page

the community to know as little as possible, but this may ultimately exacer-bate public relations problems.

Appropriate community relations may range from extensive professionalpublic relations efforts on large, widely publicized sites to almost no efforton small, private sites away from residential communities. It is not possibleto prescribe a single approach for all sites, but some general principles can befollowed.



INTRODUCTION

TABLE 1-1. Continued

Time line. It is important that during the planning process, a time line for theresponse action be developed. For example, the environmental concernmay include issues that require immediate attention through sourceremoval or managing an imminent safety or environmental hazard.Other situations may not create an imminent hazard but involve con-taminants that could produce long-term environmental impacts.

Liability issues and perceived risk to the community. Environmental con-tamination can be very costly if the contaminants migrate to an adjacentproperty or are perceived to be impacting human health. These costsinclude legal fees, investigation and engineering costs, and costs associ-ated with the corrective action. Proper planning is essential to deter-mine the extent of contamination, methods to be applied, protocol to befollowed, ARARs to be addressed, and steps to be taken to ensure allpotentially impacted parties are properly informed of the environmen-tal issues. Proper planning will be the vehicle to ensure the responseaction is carried out and that all issues are diligently addressed. Utilizinga well-planned approach will maximize protection of human healthand the environment while reducing liability and unjustified bad pub-licity.

Community participation. Community interaction has become an essentialelement to the successful design and implementation of remedialactions. Clear communication of proposed actions will assist commu-nity understanding and, ultimately, acceptance of the remedial plan.

The community is more likely to interrupt the project by political or legalaction, or to demand unnecessary procedures, if they feel that deception orsilence has been used to hide hazards. As in politics, the perception of a"cover-up" may create more ill will than the contamination. Effective com-munity involvement will reduce the likelihood of lawsuits, complaints toregulatory agencies, appeals to local politicians, and inflammatory reportson the nightly news.

Many cleanup laws at the federal, state, or local level include require-ments for notification of public agencies and communications with the sur-rounding community. Certainly, it is the responsibility of the owner andconsultant to follow these laws.

For both the owner and the engineering consultant, there is an ethicalresponsibility to stakeholders. If the community surrounding the site is sub-ject to health threats, reduced property values, or other adverse impactsduring the cleanup, they have an ethical right to know in advance and toexpress their views. If there is a possibility of such effects, the community

9




FIGURE 1-3. Remediation Process and Manual Outline.

also has a right to involvement in the investigation to determine whetherthey are occurring. Sharing information and providing frequent opportuni-ties for community involvement will strengthen remedial planning andbuild support for the project. It also allows the project team to mitigate thebad news (contaminants have been found) with the good (actions are beingtaken to clean up the site and protect the community).

Even when there will be no impact on the local community, it may be inthe owner's interest to educate the community before site remediation



INTRODUCTION 11

begins. If the neighbors first become aware of the project when they seeworkers in "moon suits" taking samples at the site, they are likely to reactwith panic and outrage, and may well use legal or political means to inter-rupt the project. However, if they have been given accurate and completeinformation in advance, the emotional impact and the severity of theirresponse will be greatly reduced, and the project will be more likely to pro-ceed smoothly.

Very often the legal requirement is that a regulatory agency be informedof the conditions and actions at the site. The agency is then responsible forcommunity notification. This may relieve the owner of the cost and effort,but regulatory agencies often pass their costs back to the responsible party.Furthermore, the owner may wish to participate in the notification to ensurethat it is done in an honest, balanced manner. The initial announcement isan opportunity to take a proactive stance.

These difficult issues are commonly beyond the expertise of owners andengineers. It is strongly recommended that legal advice be obtained todetermine their precise responsibilities. If an extensive community relationseffort is to be undertaken, it may be necessary to hire professional publicrelations experts with experience in site remediation communications. Engi-neers should not presume that they can deal effectively with the public ifthey have not had experience in doing so: Communicating with the public isvery different from communicating with other engineers or clients.

1.7 REFERENCES

American Academy of Environmental Engineers (AAEE) (1995). Environmental Engi-neering Selection Guide, AAEE, Annapolis, MD.

American Society of Civil Engineers (ASCE) (1981). Consulting Engineering—A Guidefor the Engagement of Engineering Services, ASCE Manuals and Reports on Engi-neering Practice No. 45, ASCE, New York, NY.

American Society of Civil Engineers (ASCE) (1996). Environmental Site InvestigationGuidance Manual, ASCE Manuals and Reports on Engineering Practice No. 83,ASCE, New York, NY.

Government Institutes (1993). Environmental Law Handbook, 12th Ed., GovernmentInstitutes, Rockville, MD.



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Chapter 2

SITE CHARACTERIZATION

2.1 PROJECT PLANNING

An important aspect of any site characterization is project plan develop-ment. Planning detail depends on the complexity of the characterizationinvestigation. Planning is important because it ensures that the scope ofwork is well thought out and possible contingencies are addressed (Lewisand Wilson 1995). Proper planning minimizes mid-course modifications tothe project and also sets budgets and goals that can be met.

The planning process should be formalized in writing, either through awork plan submitted to a client or regulator, or through preparation of adetailed proposal. Most planning steps become part of the effort expendedin preparing the work plan and proposal. Initial work plans may be general,becoming more detailed after consultant selection and in-house evaluations.

Site characterization investigations are usually conducted in phases,which may be iterative (Figure 2-1). Information obtained in one phase isused to determine the course of the next. Although this approach can berepetitive, it is often cost-effective, because the investigation is furtherfocused and refined at each phase. For example, contaminants whose pres-ence was initially suspected may be eliminated from subsequent analysisplans if data from a previous phase show that they are not present. Similarly,areas within the site can be eliminated from consideration during later phasesif a round of data collection shows them to be clean. By the same token, addi-tional analytical parameters or areas of investigation may be added duringlater phases if initial investigations suggest that this is warranted.

Typically, a site characterization or investigation project is conducted inresponse to a suspected or confirmed spill or other release of hazardous sub-stance, a recommendation for additional investigation in a Phase I Prelimi-nary Site Assessment, closure of a former industrial operation or facility, aregulatory agency inspection or order, a consent order, or a regulatory direc-

13




tive or requirement. During the planning process, the planning profession-als (including both owner's representatives and engineers) should be awareof the reason that the investigation is required and/or the ultimate objectivesso that the characterization can be directed accordingly. If possible, the finaluse of the resulting data or report should also be identified, so that anyreport is written to address this anticipated use and audience. As describedfurther in this chapter, data collection methods and detection limits shouldbe closely scrutinized during the planning step if there is a possibility thatthe data will be used for risk assessment purposes. Similarly, close scrutinywill be required if litigation is involved or contemplated.

FIGURE 2-1. Site Characterization Process.



SITE CHARACTERIZATION 15

EPA's seven-step data quality objectives (DQO) process has often been avaluable tool to define specific goals (EPA 1994). It is not necessary to applyevery step to every project, but the analytical and decision-making processwill be of benefit to all projects.

The DQO process is a strategic planning approach developed by the EPAquality assurance management staff to facilitate the planning of data collec-tion activities (Table 2-1). The process is designed to help planners achieveprogram goals by focusing the purpose of the investigation and directingattention to the potential uses of the data to be collected. It requires thatlikely response actions to potential investigation results be identified beforethe investigation begins.

TABLE 2-1. Seven Steps of the DQO Process

Step 1: Problem StatementConcisely describe the problem to be studied. Review prior studies andexisting information to gain a sufficient understanding to define theproblem.

Step 2: Identify the Decision that Addresses the ProblemIdentify what questions the study will attempt to resolve and what actionsmay result.

Step 3: Inputs Affecting DecisionIdentify the information that needs to be obtained and the measurementsthat need to be taken to implement the decision statement.

Step 4: Define the Boundaries of the StudySpecify the time periods and spatial areas to which decisions will apply.Determine when and where data should be collected.

Step 5: Decision RulesDefine the statistical parameter of interest (if applicable), specify the actionlevel, and integrate the previous DQO inputs into a single statement thatdescribes the logical basis for choosing among the alternative actions.

Step 6: Limits on UncertaintyDefine the decision maker's tolerable decision error rates considering theconsequences of making an incorrect decision.

Step 7: Optimize the DesignDesign the field investigation, giving adequate consideration to the resultsof Steps 4,5, and 6 and to the available resources. (This step is often done inpreliminary or outline form within the DQOs and is addressed fully in thealternatives evaluation plan.)




The first step in planning a project is to collect pertinent backgroundinformation. The experienced professional will find out what informationexists and determine what is relevant, because although a large amount ofinformation may be available, much of it may not be useable. A good sourceof background information is a Phase I Environmental Site Assessment, ifone has been conducted (ASCE 1996). In the absence of a Phase I Assess-ment, a history of previous site use obtained through verbal communica-tions and review of chain-of-title, historical aerial photographs, and/or topo-graphic maps will be useful to establish past uses of the site.

Available reports, even though not directly applicable to an environmen-tal investigation, may also provide useful site information. For example, ageotechnical report prepared for the purpose of designing a building foun-dation will identify soil types and may indicate depth to groundwater or thepresence of perched water on the site. Real estate reports may contain plotplans and site layouts, which will help to accurately plot site features andidentify locations for soil borings or groundwater wells. These reports mayalso identify features or operations that have contributed to suspected con-tamination. However, data from documents prepared by others should beverified.

The planning phase must also include collection of information regard-ing site access or access requirements, surface materials (unpaved, or typeand thickness of pavement), depth to groundwater, location and use ofnearest wells, site topography, surface water drainage, presence of overheador subsurface utilities or other obstructions, regional land use, and locationand demographics of residents in the vicinity of the site.

The decision to obtain information will be dictated by its intended use,the cost of obtaining it, the particular phase of the investigation, and avail-able budget. Before proceeding with the investigation, the planning profes-sional should identify additional information that may be required. Follow-ing the identification of data gaps, the means to obtain this information andits possible sources can be identified.

Other factors to consider as part of the planning process may includeavailability of staff or subcontractors, availability of equipment needed forthe investigation, presence of equipment storage and staging areas, possibleencroachment onto adjacent properties or public rights-of-way, and storageand disposal of wastes (soil cuttings, purge water, protective equipment)generated during the investigation.

Budget often is the limiting factor when planning a site characterizationinvestigation and is inevitably a significant factor in determining the scopeof an investigation. Because of this, the project planner can be placed in aposition where the thoroughness of the investigation is sacrificed to fit abudget. The skill of the planner is challenged to determine the most cost-effective characterization method that will address the goals of the investi-gation and maintain project quality. Variables to be considered in determin-




ing the most cost-effective approach include investigation methods, regula-tory requirements, number of samples collected, analytical parametersselected, site screening techniques, report presentation, etc.

Laboratory analyses may be done in an established commercial labora-tory (a fixed or stationary lab) or with analytical instruments taken to the sitein a transportable vehicle such as a trailer, van, or converted recreationalvehicle (a mobile lab). Each alternative has advantages and disadvantages. Amobile lab will provide rapid and possibly less expensive results, particu-larly for large investigations. The use of a mobile lab can also facilitate fielddecisions. However, the fixed lab can be used for a more comprehensivesuite of analyses, and the results may be more reliable. Often a mobile lab isused for the bulk of the analyses, with occasional duplicate samples beingsent to a fixed lab for confirmation. The throughput of the laboratory (i.e.number of samples that can be analyzed per unit time) should also be con-sidered when evaluating mobile versus fixed laboratories for a project.

As with any environmental project, compliance with rules, regulations,and guidelines of local, state, and federal regulatory agencies is a key issue.It is important that the planning professional understand and comply withthese rules. Some regulatory agency involvement will be required on mostprojects and should be considered early in the process, particularly if theinvestigation report is to be submitted to the agency for evaluation. Undersome conditions, a work plan that outlines the scope of the investigationmust be submitted to the lead regulatory agency for approval in advance. Apre-approyed work plan is often desirable as a means to avoid conflicts andprevent project delays. In addition, regulators may require specific data fortheir evaluation and may specify the format of submittals. Required plansmay include a sampling and analysis plan (including the field sampling planand the quality assurance project plan), a data management plan, a healthand safety plan, and a management plan for the waste generated by theinvestigation.

In summary, several key questions should be answered before the sitecharacterization plan is developed (Table 2-2).

2.2 EVALUATION OF HISTORICAL DATA

Historical data play a key role in establishing the scope of a site character-ization investigation. Historical information can identify time periods dur-ing which potentially contaminating operations were conducted and mayserve to limit areas that warrant investigation. In addition, it can be used todecide which analyses and tests are appropriate for site characterization.

As an example, a site investigation was conducted for a former platingshop at which very little historical information was available. The investiga-tion included an extensive sampling program, with samples analyzed for




TABLE 2-2. Questions Addressed by the Site Characterization Plan

Why is the project being carried out?What are the regulatory agency requirements?What is the objective of the characterization investigation?How will the information obtained during this investigation be used?What data and information are currently available, and what do they indi-

cate?What additional data and information should be obtained?What site constraints are present?Will the data support the conclusions?What is the available budget?

several parameters, including heavy metals, pH, and volatile organics. Atanother similar site, detailed historical information revealed a specific loca-tion of a vapor degreaser, which remained unchanged throughout the his-tory of operations. This detailed historical information also identified spe-cific hazardous materials used at the facility together with hazardousmaterials storage areas. The investigation at the latter site required less sam-pling because specific areas were targeted and fewer parameters wereincluded, even as the goals of both investigations were met.

No single source of historical information should be relied on exclusively.Collectively, data sources can provide sufficient information to formulate acomprehensive picture of site conditions (a partial list of data sources is con-tained in Table 2-3).

Where available, fire insurance maps may provide important informa-tion. These maps often identify past site use and can also record importanthistorical site features such as the types and locations of flammable storage(including aboveground and underground tanks).

Aerial photographs are extremely helpful in determining past site use.However, their use is limited to identification of surface structure locationsand types and of some activities conducted outside of buildings, such as on-site disposal. An experienced reviewer can obtain considerable informationfrom aerial photographs, particularly those having good coverage spacedover a number of years. Departments of transportation and county roadwaydepartments are inexpensive sources for aerial photographs.

Larger industrial facilities or military operations may have an archive ofhistorical plot maps. Information from past on-site operations can beobtained through the review of building names identified on the maps.Although they are not as valuable, historical topographic maps may providesome of the information that can be obtained from site-specific maps and




TABLE 2-3. Sources of Historical Information

Fire insurance mapsAerial photographsHistorical directoriesBuilding department records and/or blueprintsLocal planning offices and/or local health departments

Historical topographic mapsSite mapsSanborn mapsRegulatory filesConversations with personnel having a long on-site historyChain-of-title records

can fill data gaps. Historical topographic maps can also be useful in identify-ing previous landforms that may have been later altered or covered, such asstreams or swampy areas.

Conversations with personnel who know the history of the site can alsoprovide useful data. However, the information should be verified throughadditional sources to ensure the reliability of the data. Of limited use isreview of chain-of-title records. Although some important information canbe obtained through these records, information in chain-of-title recordsshould not be relied on exclusively.

Sources of historical information and its review is contained in ASCEManuals and Reports on Engineering Practice No. 83 (ASCE 1996). Thismanual should be consulted for additional information.

2.3 SITE CHARACTERIZATION METHODS

No two site characterizations are exactly the same. Each has its unique setof associated circumstances, such as contaminants of concern, volume andextent of contaminants, media affected, and site access. As part of the plan-ning process, a professional will review the characteristics of the site anddefine an approach that addresses the goals of the project and controls costs.Because there are discretionary steps, two equally proficient investigatorsmay devise different approaches for a particular set of conditions. This isfurther complicated because site characterization projects are typically com-pleted in phases, and the results from one phase influence the approach inthe following phase.




The objective of a site characterization is not only to identify and delin-eate the contaminants and concentrations of concern but to develop a broadunderstanding of the site. A site characterization should include physicalcharacteristics of the site, characteristics of the contaminant source, natureand extent of contamination, and fate and transport mechanisms and theirenvironmental impact.

The concept of the completed exposure pathways is intrinsic to the deci-sion-logic for any site characterization or remediation. A completed exposurepathway consists of the following five elements: a source of contamination,an environmental medium, a point of exposure, route(s) of exposure, and areceptor population. Receptor populations include community residents andany relevant worker populations. All five elements must be present for apathway to be considered complete and for the potential for exposure toexist. The completed exposure pathway, with all five elements present, is thefoundation upon which the case is built to determine which populations arebeing exposed to hazardous substances, the relative hazards to humanhealth posed by a site, and what remedial actions should be considered.

2.3.1 Physical Characteristics

Physical characteristics determine the environmental setting of a site, andinclude factors such as soils, geology, hydrology, meteorology, and ecology.An analysis of these characteristics for a site should emphasize elements thatare important in determining the fate and transport of contaminants in theexposure pathways of concern. For example, if migration to groundwater isfeared, physical characteristics evaluated will include soil types in the unsat-urated zone, depth to groundwater, precipitation, etc. A different set ofphysical characteristics will be examined if there is potential exposure to siteworkers through contaminant inhalation.

2.3.2 Contamination Source Characteristics

The characteristics of the contaminant(s) are a factor in determiningpotential exposure scenarios. The contaminants may have been generatedat one time in the past, or the release may be current and continuing. Thenumber and types of contaminants released vary, along with their rates ofrelease. Compounds may be entering the environment as gases, liquids, orsolids. For example, fate and transport scenarios associated with a landfillare different from those associated with a leaking underground tank. Thecontaminants of concern are different, and the time line for releases mayvary. A release from an underground storage tank can be stopped relativelyeasily, whereas releases from a landfill may continue for many years. Inaddition, the magnitude and chemical nature of releases from each of thesesources are likely to be different.




2.3.3 Environmental Data for Public Health Decisions

In general, the information collected for engineering decisions at hazard-ous waste sites is similar to that needed by public health agencies to makedecisions regarding the hazards posed by the site. However, often there areinsufficient environmental data to determine whether more rigorous healthinvestigations should be conducted. Environmental data are critical to thepublic health algorithm for assessing sites, but only to the extent that suchdata can be used in a manner that contributes to and facilitates good publichealth practice. Generally, public health professionals will need additionalinformation in the following categories:

• Contaminant concentrations in all off-site media to which the publicmay be exposed

• An appropriate detection limit and level of quality assurance/qualitycontrol in samples to ensure resulting data are adequate to assess pos-sible human exposures

• Discrete samples that reflect the potential range of exposure of thepublic

• Shallow surface soil and sediment analytical data from samples (notdeeper than 3 inches)

• Extensive biota studies and analyses of edible portions of plants• Ambient and indoor air samples• Lists of physical hazards and barrier to site access

To ensure that the data needs of the public health professional areaddressed, it is recommended that the engineering consultants discuss theplans for the site characterization with local, state, and/or federal publicagencies. Local and state agencies can provide guidance on what data areneeded for site-specific public health determinations. In addition, theAgency for Toxic Substances and Disease Registry (ATSDR 1994) providesguidance on the data needs of the environmental public health professional.

2.3.4 Nature and Extent of Contamination

Sampling is conducted to define the nature and extent of contaminationat a site. Pollutants may affect soil, groundwater, surface water, sediments,and air. Sample analyses are required to establish concentrations within theaffected media so that the lateral and vertical extent of contamination can bedetermined. This information forms the basis on which potential of therelease can be assessed, the public health implications determined, andremedial alternatives evaluated.

2.3.4.1 Soil Sampling. The medium that is most commonly analyzed duringsite characterization is soil. There are numerous methods for soil character-




ization. They include geophysical techniques, grab soil sampling, handaugering, backhoe excavation, soil vapor surveys, direct push sampling, androtary auger or cable tool drilling (Devinny et al. 1990).

Each of these methods has inherent strengths and weaknesses. Thechoice of method depends on the specific circumstances and goals of theinvestigation as well as site-specific constraints. It is not uncommon for onecharacterization investigation to utilize many of these techniques.

2.3.4.2 Geophysical Techniques. Surface geophysical techniques are nonin-vasive and are used as a preliminary step to provide subsurface informationfor a site. Geophysical methods include magnetics, electromagnetics,ground-penetrating radar, resistivity sounding, and seismic refraction.These methods can survey large areas of a site at relatively low cost.

Because of the noninvasive nature of surface geophysical techniques,they can be effective in identifying features on a site that warrant furtherinvestigation without disturbance of the site. For example, surface geophys-ical techniques can determine the physical features of a site by locating thegroundwater surface, the base of refuse or other fill, fractures, or other geo-logical inhomogeneities. These techniques also can identify subsurfacestructures such as buried pipelines, underground tanks, or buried wastes. Itis particularly important to locate and avoid possible subsurface structures.

The limitations of each method must be thoroughly evaluated before aselection is made. For example, the value of many surface geophysical tech-niques depends on the skills of the investigator as well as on the limitationsof the methodologies. The experience of the surveyor may determine whichdata are taken and how they are interpreted. Results of a surface geophysi-cal survey cannot be confirmed without excavations.

2.3.4.3 Grab Soil Samples. Grab sampling is employed frequently to assesscontamination of surface soil (e.g., upper 12-30 inches of soil). Grab samples,for example, could be used as a preliminary step to assess releases to surfacesoil in an area that had been used to store drums of hazardous materials.Surface soil samples are particularly important to determine human healthrisks. People, especially children, are far more likely to be exposed to surfacecontaminants through routine work and play than to contamination foundat greater depths.

The basic approach for collecting grab soil samples is simple. A handtrowel, shovel, or similar sampling instrument is used to put soil into a sam-pling container. This method is easily implemented and can be used inplaces where access is limited. However, it may not be suitable for collectionof samples for volatile organic compound (VOC) analysis because it distortsthe sample. When it is used in the collection of samples for VOC analysis,caution should be exercised in the collection of the samples and in the subse-quent interpretation of VOC data.




One way to collect relatively undisturbed soil samples is to use a coringdevice driven or pushed into the soil surface. Undisturbed samples can becollected with a slide-hammer sampler with 2-inch-diameter brass tubes.These are acceptable for measuring concentrations of VOCs.

Samples collected as part of a site characterization can be either discreteor composite samples. Discrete samples are collected from soil at a specificlocation and depth on a site. Composite samples are a mix of several discretesamples that have been combined in the field or in the analytical laboratoryto form one sample for which an average concentration can be determined.A composite sample can represent conditions at a single depth across a siteor at various depths at one sampling location. Composite samples are usu-ally collected as part of preliminary assessments to evaluate whether an areawarrants further investigation. The disadvantage of composite samples isthat the additional analysis of discrete samples is often required if compositesample results indicate the presence of contamination. Composite samplesare not generally acceptable for the analysis of VOCs because vapors may belost during the compositing process.

2.3.4.4 Hand Angering Methods. A modification of the grab soil samplingmethod is the use of a hand auger coupled with a bulk soil sampler. Com-monly, a 2- to 4-inch-diameter auger is used to bore to the desired samplingdepth. A bulk sampler, comprised of a sample barrel lined with a stainlesssteel or brass sleeve, is hand driven into the soil by using a weighted slidehammer. A relatively undisturbed core sample is collected. Various power-assisted devices are available to facilitate sample collection.

Like grab sampling, hand augering methods can be used when access bylarger equipment is not possible. It also can be used during preliminaryphases of investigation because samples can be collected relatively inexpen-sively. However, because this method relies on hand power to advance tothe desired depth, it is limited by site soils. Borings can be made to as muchas 20 feet in firm but cuttable soils (such as silty sand), but only 1-2 feet maybe possible in hard clay. The approach generally fails in rocky soils. Thismethod also does not work successfully in gravelly soils, loose sands, or highgroundwater conditions where the soil collapses into the hole as it is beingbored.

2.3.4.5 Trenching. Conventional excavating equipment such as a backhoecan be used in sample collection. Trench (or pothole) excavation is particu-larly useful in conducting investigations for those contaminants that impartcolor to soil, such as heavy hydrocarbons (oil). Inspection of the side walls ofthe excavation allows visual assessment of the vertical extent of contamina-tion. A backhoe can excavate a trench rapidly. Disturbed samples can be col-lected directly from the bucket of the backhoe while a bulk density sampleris used to collect undisturbed soils from the trench. Using a backhoe, large




numbers of samples may be collected over a short period of time for variousparameters, including samples for geotechnical testing that may be neces-sary to evaluate remedial alternatives.

In addition to depth limitations, a disadvantage of backhoe excavating isthat it is extremely disruptive to the site under investigation. Because a largeamount of soil is disturbed and exposed to the atmosphere, there can betroublesome releases of toxic or odorous gases during the operation, whichmay cause severe and unintended consequences. Therefore, this method isnot recommended for sites where highly toxic materials are anticipated.Through backhoe trenching, a large volume of excavated material is gener-ated that must be properly stored and managed. Health and safety mea-sures for workers and other receptors must also be considered when evalu-ating this method for sample collection.

2.3.4.6 Soil Vapor Surveys. Soil vapor surveys are used extensively forassessing contamination by VOCs and other gases (Dorrance et al. 1995).The method collects samples of the gas trapped between soil particles byadvancing a sealed probe attached to tubing into the soil to the desireddepth. The probe is then opened and evacuated. The soil vapor is collectedfor direct analysis in a mobile laboratory or held in gas sampling canisters orbags for transport to a fixed laboratory (Ullom 1995). Samples are sometimesanalyzed directly by using field instruments.

This method can be effective in identifying the lateral and vertical extentof soil contamination associated with releases of volatile materials such assolvents and gasoline. It is also a useful tool for assessing potential ground-water contamination. Although soil vapor results are not always directlyrelated to bulk soil results, the data provide a method for determining suit-able locations for soil sampling. Under certain geological conditions, soilvapor data can be more representative of the extent of contamination thandata from bulk soil samples, particularly in course-grained sediments.Indeed, regulatory agencies in California are specifying vapor surveys asthe preferred method over bulk soil sampling for investigations of VOCs incoarse-grained alluvial soils.

Soil vapor surveys are rapid; 10-20 points can be investigated in a normalwork day, although the actual number is highly dependent on soil condi-tions and sampling depth.

Soil vapor investigation does not provide lithological data. In addition,cobbles or other obstructions can impede the investigation. Finally, datafrom fine grained sediments may not be representative of actual site condi-tions because good vapor recovery may not be achieved.

2.3.4.7 Direct Push Sampling Methods. Direct push methods utilize hy-draulics, sometimes coupled with vibration or driving action, to advance asampling device mounted at the end of a relatively narrow (normally,




1-inch) steel rod through soil to the desired depth. Direct push methods canbe used to collect bulk soil, soil vapor, or groundwater samples.

One reason for the increased popularity of direct push methods is recentadvances in equipment and technology. Some equipment requires that theentire tool string be retrieved from the hole each time a sample is collected,which may result in caving of the hole. However, most equipment now uti-lizes a dual-wall system, which allows the sampling device to be removedwhile maintaining the integrity of the hole.

A significant advantage to this method is that there is little production ofsoil cuttings, which may require managed disposal. Also, the equipment canbe less expensive than conventional drilling rigs. The disadvantage is that inmany cases, a groundwater well cannot be constructed in a hole createdusing a direct push method because the pressure of driving the hole tends toseal the side walls, particularly in fine-grained soils. In addition, direct pushmethods are generally limited to a maximum depth of approximately 100feet depending on soil lithology and the specific equipment used to advanceor retrieve the probe.

2.3.4.8 Drilling. As with other methods, the drilling method selected foreach investigation is dependent on project goals, site constraints, and geo-logical conditions. Typical drilling methods include hollow-stem auger, airrotary, solid-stem auger, cable tool, and mud rotary. Each method has appli-cations in which it is most effective, and their suitability depends on geolog-ical conditions at the site. Emphasis should be placed on the ability to collectsamples that fulfill the goals of the investigation.

The hollow-stem auger is the most common tool utilized in collecting soilsamples for site characterization investigations at shallow to moderate depths.As the name implies, the auger is hollow, which enables a sampling device—typically, a split-barrel sampler—to be passed through the auger to collect soilsamples. Undisturbed soil samples can be easily collected at desired depths.Groundwater wells also can be constructed within the hollow stem of theauger. As the bit is advanced, soil is removed from the boring through helicalflights on the outside of the auger. Hollow-stem augers are effective for drillingthrough unconsolidated materials but are generally ineffective in consolidatedsoils, rock, or soils containing a large proportion of cobbles or boulders.

The commonly used split-barrel sampler is a cylinder cut in half along itslongitudinal axis. Threads on the outside edge of both ends allow the sam-pler to remain intact when a drive head coupler and drive shoe are threadedonto each end. A relatively undisturbed sample is collected by driving thesplit-barrel sampler into the soil after drilling has reached the desired depth.A sleeve placed inside the sampler contains collected soil. After retrieval, thesampler is disassembled, and the sleeve is removed from the sampler. Sam-plers must be cleaned between sampling intervals to prevent cross-contami-nation.




Air rotary drilling is typically used for environmental applications wherehollow-stem techniques cannot be used. A rotary bit is used to bore a hole,and pressurized air is used to remove drill cuttings. As a result of the high-pressure air that is typically associated with air rotary drilling, this methodshould not be selected for use in investigations of VOCs because these willbe flushed from the soil that is to be sampled.

Solid-stem auger, cable tool, and mud rotary drilling techniques generallyhave limited application in site investigations. As the name implies, a solid-stem auger has a narrow steel stem and wide flights. A solid-stem auger iseffective for drilling shallow boreholes but must be removed for collection ofundisturbed soil samples. Disturbed samples may be collected from theflights of the auger. In cable tool drilling, the bit cuts by repeated lifting anddropping of the drill string. In unconsolidated material, casing is driven intothe formation following the bit. Cable tool drilling is particularly effective inloose materials and is capable of drilling deep holes in hard rock, thoughslowly. Mud rotary drilling is a rapid and effective method for drilling holesbut generally is not acceptable for environmental purposes because sampleswill be contaminated by drilling fluids and muds.

2.3.4.9 Surface Waters. Ponds, lakes, or flowing streams may be part of acontaminated site. Because stratification can occur in standing water, thenumber and location of samples depend on factors such as size, depth, andconfiguration. Contaminants tend to mix throughout the cross section of astream, but longitudinal variation is great. Upstream and downstream mea-surements are important.

Samples from surface waters can either be grab or composite samples.Common grab sampling techniques use pond samplers; weighted bottlesamplers; peristaltic pumps; and Van Dorn, Nannsen, or Kemmerer depthsamplers.

Composite samples are collected from a water body when it is anticipatedthat characteristics may change over time or depth. Composite samples pro-vide an average concentration and cannot be used to assess peak or mini-mum concentrations. Composite samples can be comprised of a series ofgrab samples. Waste and water streams can be sampled by using an auto-matic composite sampler. If the sampler is used with a flow measuringdevice such as a weir with a water level recorder, flow-proportioned com-posites can be collected.

Excavations used for sampling or in the remediation process are some-times flooded with groundwater, and sampling may be appropriate. Theappropriate methods are similar to those for ponds and lakes.

2.3.4.10 Sediment Sampling. Sediments located near or beneath water bod-ies can be impacted by various contaminants through contact with contami-nated surface water, deposition, or direct discharge of contaminants. Most




commonly, sediments are impacted by halogenated hydrocarbons (poly-chlorinated biphenyls [PCBs], dioxins, pesticides, etc.), polycyclic aromatichydrocarbons, and heavy metals. These contaminants are more dense thanwater, have an affinity for adsorbing to particles, and/or form precipitatesthat settle out of water.

The characteristics of sediments vary widely depending on the overlyingwater body. Some sediments are extremely fine-grained and free-flowing,whereas others are compacted and dense. Therefore, sampling of thesemedia is dependent not only on the specific analyses to be completed on thesamples but also on the characteristics of the sediment.

Sampling methods identified above for soils and surface waters can bemodified for use in sampling sediments, particularly those that are locatedabove the water surface or in shallow water. For sampling of sedimentslocated in deep water, specialized samplers such as Eckman or Ponardredges are used.

As part of an investigation in which sediments are sampled for chemicalanalysis, it is equally important to characterize physical properties of thesediment, because these properties will affect contaminant fate and trans-port. Physical characteristics that should be established include particle sizedistribution, organic carbon, and total solids. Sediments also should be ana-lyzed for chemical parameters such as pH, oxidation/reduction potential,salinity, sulfide, and reactive iron and manganese.

2.3.4.11 Groundwater. Groundwater is characterized through installationand sampling of monitoring wells (Selby 1991). To characterize horizontalflow direction and determine background chemicals of concern, threegroundwater wells are needed, one of which is upgradient of the contami-nant source. Installation of three wells allows for determination of thehydraulic gradient, and thus the direction of groundwater flow. Monitoringwells are usually constructed of 2- to 4-inch-diameter PVC and screened inthe saturated zone to allow water to enter the casing. Stainless steel or Tefloncasing may be used where it is feared that adsorption of organic contami-nants will distort the results or where a contaminant or aquifer characteris-tics could damage conventional well materials. A properly constructed anddeveloped well causes minimal disturbance to the formation. Contamina-tion of groundwater samples by inadequate sealing or leaching of chemicalsfrom well construction materials must be prevented.

At some sites, contaminant concentrations in groundwater can be highlyvariable because of changes in water flow patterns and adsorption and des-orption of contaminants by different soil strata. Recommendations regard-ing groundwater must be based on trends and not on single samplingevents.

Samples are collected from groundwater wells after they are purged toremove water that has accumulated within the well casing. Purging ensures




that water sampled is representative of water within the water-bearing for-mation. Wells are typically sampled after three or more well volumes ofwater have been removed through the use of a bailer or pump and parame-ters such as temperature, pH, and specific conductance have stabilized.Sampling must sometimes be done in wells that produce very little water. Alow-yield well is typically purged dry twice, with the well allowed torecover 80% of its volume between purgings, and then sampled.

Sampling apparatus includes bailers, suction-lift pumps, submersiblepumps, air-lift samplers, and gas-operated squeeze pumps. The appropriatesampling method for groundwater is dependent on the analytical parame-ters being determined and the regulatory protocols being implemented. Forexample, a bailer is the preferred method to collect samples to be analyzedfor VOCs because volatilization losses are minimized. Alternatively, sensorscan be placed within the well to provide data continuously or at fixedintervals.

Alternative groundwater sampling methods are being utilized withgreater frequency. A common alternative is the use of grab sampling inwhich a casing having a retractable tip is driven into the saturated zone. Atthe selected depth, the tip is retracted, exposing a porous plate that allowswater to pass into narrow-diameter tubing, which can be purged and sam-pled. Grab groundwater sampling is typically used to provide screeningdata, allowing mapping of a contaminant plume for better well placementand site delineation. Analytical results obtained from grab samples may notbe directly comparable with those obtained from permanent monitoringwells. In addition, a disadvantage of this method is that sampling cannot beeasily repeated for verification at a later date.

2.3.4.12 Air Monitoring. Air monitoring can be used to assess potentialimpacts to site workers, provide a relative indicator of contamination in soilsamples, assess potential airborne contaminants associated with a release,and assess the migration of airborne contaminants from a site.

Air can be monitored with portable field instruments or by collectingsamples for laboratory analysis (Waxman 1996). The most common devicesused in site characterization investigations measure organic vapor concen-trations. The wide variety of organic vapor analyzers available differ in themethod used to quantify vapors. Flame ionization detectors and photoion-ization detectors are common. Both of these provide results in the parts-per-million by volume range. The choice of instrument for a particular applica-tion will depend on the contaminants and site characteristics.

Other instruments have specific applications in site investigations.Combustible gas meters monitor concentrations of flammables such asmethane gas in wells or near landfills. Oxygen meters are used in environ-ments where it may be depleted. Particulate dust meters can be used tomonitor migration of contaminated dust during drilling, excavation, or




other activities that may raise dust. Lower explosive limit meters deter-mine whether explosive gases are nearing their explosive threshold,threatening safety.

Samplers can be used to monitor air over longer periods. In active sam-pling, air is moved through the collection medium. Active samplers usuallyconsist of a pump, sample inlet, and a sampler containing an appropriatecollection medium (filter paper, activated carbon, gas absorbers, samplebags, etc.). At the end of the sampling period, the collection medium is trans-ported to a laboratory for analysis. A flow rate record must be accuratelymaintained to obtain data that can be compared with exposure limits orother standard values.

Passive sampling relies on diffusion to bring compounds to the sensor. Inaddition to their typical use as personal monitoring devices, passive sampleshave had some use in site investigation. Passive samplers include dosime-ters and diffusion samplers.

2.3.4.13 Data Collection for Engineering Evaluations. During the site char-acterization, it is desirable to collect data that eventually will support alter-natives for evaluation and remediation design. Much feasibility and prelim-inary design level data can be collected inexpensively at this stage, ratherthan at additional cost later on. A borehole drilled for site characterization,for example, can also yield samples for remediation design. If these are col-lected during the site characterization, fewer expensive borings may beneeded during the design phase.

During the planning stages, the planning professional should solicitinput from the remediation design team to identify data needs that are typi-cal of the likely remedies for the site. Many of these data needs overlap withthose collected for site characterization. Typical available data at the plan-ning stage describe site topography, subsurface soil properties, groundwaterlevels, and groundwater geochemistry.

Site topographic data usually can be obtained inexpensively from aerialphotography. The topographic map can also be used as a base map for locat-ing the site characterization investigation points. In addition, use of ste-reopairs from this and other flights often provides useful soil and bedrockinterpretation for use in geotechnical and hydrogeological evaluations.

Testing selected soil samples for basic geotechnical index tests (e.g., mois-ture content, grain size, Atterberg Limits, and organic content) can providesite-specific knowledge of the soil and rock types. These data can be corre-lated with global or regional values in the literature to provide a frameworkfor understanding the engineering properties of the materials at the site.These tests are excellent to evaluate the variability of materials at the site andtherefore to evaluate the level of uncertainty in the feasibility level cost esti-mates. These data are also useful in evaluating hydrogeological issues, suchas the potential for fissuring and fracturing in clay layers.




Most of the groundwater data collected during the site characterizationare intended for contaminant transport evaluations. Occasionally, addi-tional piezometric data from critical areas or from critical seasonal periodsare needed to properly evaluate the engineering issues related to the feasi-bility of pump and treat, containment, or capping systems.

Some basic groundwater geochemistry analysis from selected samplesduring the site characterization can be very useful in evaluating major costelements affecting the feasibility of water treatment or intrinsic remedia-tion (also referred to as natural attenuation or natural degradation). Typicalwater chemistry analyses to evaluate water treatment issues include totalsuspended solids, total iron, total hardness, total organic carbon, pH, andtemperature. Typical chemistry analyses to evaluate the potential for aero-bic and anaerobic intrinsic remediation include nitrate, total and dissolvediron, total and dissolved manganese, sulfate, sulfide, chloride, carbon diox-ide, methane, phospholipid fatty acids, pH, temperature, and redox poten-tial. Refer to Chapter 5 for additional information regarding intrinsic reme-diation.

2.3.5 Analysis, Data Evaluation, and Reporting

Samples not tested in the field should be preserved as required for therequested analysis and then logged and tracked from the point of collectionto the laboratory by using appropriate chain-of-custody documentation.Information regarding EPA-approved analytical methods and samplingconsiderations is provided in SW-846: Test Methods for Evaluating Solid Waste,3rd ed. (EPA 1996b). SW-846 contains specific information regarding sam-pling techniques, analytical methods, preservation of samples, proper vol-ume, appropriate containers, and sample holding times. If applicable, stateor local regulatory requirements or guidelines should also be followedbecause they may be more stringent than EPA requirements.

After collection, samples are transported to a laboratory for chemicalanalysis along with appropriate quality assurance/quality control (QA/QC)samples, such as duplicates and blanks. The purpose of blank samples is toassess the extent to which any constituents identified in the environmentalsamples might be attributable to external conditions such as impure sourcewater or incomplete decontamination. Rinsate blanks can be collected tomonitor the effectiveness of field equipment decontamination, field andambient blanks to determine the effects of site conditions, and source blanksto document the quality of each source of water used.

The laboratory must have an established quality control program thatensures that samples are accurately analyzed and that data are defensible asrepresentative of site conditions. If applicable, the laboratory should be certi-fied within the state in which the investigation is being conducted. Beyondcertifications, an evaluation of laboratory quality control and its capability




and capacity to perform the requested analyses within required time framesmust be made. Laboratory staff should be interviewed to determine theirmethods, the availability of quality control data, current capacity, and theability to perform the required analyses within guidelines established by EPA.

On receipt of analytical data from the laboratory, the report should bescrutinized to ensure that the data are accurate and reflect site conditions.The report should indicate that samples were analyzed within acceptedholding times. Trends in the data should be reviewed to determine whetherthey are intuitively reasonable. Laboratory detection limits should bereviewed for accordance with agreed limits, project objectives, and regula-tory guidance. Quality assurance and quality control data also should bereviewed to verify that data are within acceptable limits. Any anomaliesshould be discussed with the laboratory. Depending on project objectives,more sophisticated data evaluation such as intercomparisons, data plots,regression analysis, and tests for fitness can be conducted to validate thedata. Data should be reported in a form that clearly describes what wasdone and shows trends in the data.

EPA has prepared guidance manuals for data evaluation that should beconsulted for additional information.

2.4 HUMAN HEALTH RISK ASSESSMENT

2.4.1 Introduction

The goal of environmental professionals in site remediation is to charac-terize the contamination to the fullest extent practicable and to provide theleast expensive, technically sound method for site mitigation to ensure pro-tection of public health and the environment. These goals cannot beattained without knowledge of the inherent risks associated with the haz-ardous substances at the site. Risk assessment is a tool that can be used todevelop site remediation goals that are protective of human health.

In the past, environmental risks were described qualitatively, based onavailable information and best engineering judgment and practice. As moreinformation has been collected on the toxicity of hazardous substances andintake by human receptors, risk assessments have become more quantita-tive in nature. In its current state, a human health risk assessment (HRA)allows us to quantify the risk associated with hazardous substance contami-nation and determine the mitigation measures necessary to alleviate it.

2.4.2 Typical Role of Health Risk Assessment

An HRA can serve several roles throughout the site mitigation process.When a site has been characterized and the extent of contamination is




known, an HRA can evaluate the imminent hazard associated with site con-taminants as well as baseline risk conditions for all potential receptor scenar-ios. This allows determination of the overall risk under present conditionsand prioritization of contaminants, site areas, receptor scenarios, and envi-ronmental media for which risks are unacceptably high. Unacceptable risksbecome the focus of corrective action.

An HRA can also support development of health risk-based cleanupgoals. Establishing cleanup levels using a quantitative risk-based approachis becoming increasingly popular with legislators, regulators, and the public.Risk assessments are increasingly guiding development of environmentallaw and regulations. Risk-based cleanup goals are important for the evalua-tion of remedial alternative feasibility. However, risk-based cleanup goalsare not accepted in all states and local jurisdictions, so state- and area-spe-cific regulations should be consulted.

When risk-based cleanup goals cannot be met through remediation, anHRA can guide risk management. Risk management is the procedurethrough which environmental risks are described to those who may bestakeholders and then alleviated to the satisfaction of the stakeholders. Riskmanagement may entail limitation of future development on a site withsome remaining contamination. After remediation, an HRA can be used toevaluate the risk and define necessary use restrictions on a property withresidual contamination.

2.4.3 Planning for an HRA

Planning an HRA should begin early in a site remediation project. Thereare several aspects of an HRA that can be significantly affected by initialinvestigative activities. The EPA and some state agencies have developedguidelines for the data needs of an HRA.

Proper site characterization as provided in a sampling and analysis plan,including statistically valid sampling, analytical method selection, and back-ground sampling, can strongly affect the content of an HRA. It may beappropriate to involve a risk assessor in the planning stages of an environ-mental investigation. In many cases, environmental investigations focus onpotential or existing "hot spot" areas where contamination is worst. Estimat-ing risks using data from these hot spots can substantially overestimate riskfor the site as a whole. On the other hand, collecting and analyzing samplesfrom all areas of a site, even those where there is no contamination, maylead to an underestimate of risk.

The objective of site characterization is to define the extent and magni-tude of contamination. However, in many cases, investigators do not obtainstatistically valid data. Because there are so many calculations and assump-tions involved with an HRA, it is important to minimize the uncertainty inthe various values used in the calculations. One of the areas in which uncer-




tainty should be minimized is the determination of representative concen-trations of contaminants from site characterization data. The risk assessorhas some control over the validity and appropriateness of the site character-ization data and should exercise this control during the planning phases of asite characterization project.

After statistically valid site characterization data have been obtained, thescoping process for the HRA must begin. Depending on the extent and mag-nitude of contamination and other site-specific conditions, a decision shouldbe made as to the need and level of effort for an HRA. In many instances, anHRA may not be necessary to guide the site mitigation process and developremediation goals. In other cases, only a screening-level (e.g., very healthconservative) HRA may be necessary to obtain the necessary risk informa-tion. The level of effort for the HRA may be driven by regulatory require-ments, stakeholder concerns, costs for completion, practicality, and/or otherfactors.

2.4.4 Protocols for a Baseline HRA

In instances where a comprehensive HRA is deemed necessary and prac-tical, a formal baseline human HRA can be developed for this purpose. Aformal HRA evaluates the human health and environmental risks associ-ated with contaminants in soils, sediments, surface water, groundwater, air,or other environmental media at a particular site. Its objective is to provideupper-bound, conservative estimates of the human health impacts.

A baseline HRA addresses current and future health effects, assumingsite conditions will remain unchanged (e.g., no remediation will take place).However, the baseline HRA can be utilized to develop health risk-basedcleanup goals for a site if calculated baseline risk levels are above regulatorythresholds.

HRA protocols presented here reflect information provided in currentEPA guidance (EPA 1989a). Although risk assessment protocols are con-stantly being evaluated and modified, this document remains the primaryguidance for HRAs in the United States. EPA risk assessment guidelinesshould be supplemented with guidelines established within a particularstate or local jurisdiction.

Many state and local agencies have developed guidance manuals andregulations governing HRAs. In addition, some professional organizationshave developed guidances for their profession. The risk assessor shouldreview all available HRA regulations, resources, and guidelines for eachjurisdiction. Because risk assessment guidelines are constantly in a state offlux, the risk assessor must keep abreast of current developments in the fieldto be successful.

In addition to regulatory risk assessment protocols, the Agency for ToxicSubstances and Disease Registry (ATSDR) has developed protocols for pub-




lie health assessments at National Priorities List and Superfund sites. Theseassessments can provide additional information associated with the poten-tial human health impacts resulting from contaminated sites. More informa-tion about public health assessments and health hazard evaluations can befound in the ATSDR Public Health Assessment Guidance Manual (ATSDR1992).

Typical contents for an HRA and common procedures for preparing onehave been developed by EPA (EPA 1989a) and are valuable tools for an HRA.See Table 2-4 and Figure 2-2.

2.4.5 Evaluation of Site Characterization Information

The initial phase of an HRA includes the development and evaluation ofsite characterization information. Information regarding the environmentaland physical setting of a site should be gathered and assessed. Critical char-acteristics expected to influence the degree of chemical release and subse-quent transport to a potentially exposed population are the most importantitems. These characteristics include surface topography, climatology andmeteorology, vegetation and soil cover, geology and soil types, groundwaterhydrology and hydrogeology, surface hydrology, current and future zoningand land use, and demographics. Each of these factors could have an impacton human exposure to chemicals and on risk calculation.

Review of the site characterization may show that supplemental informa-tion is necessary. This occurs when the gathered data are not statisticallyvalid according to EPA, state, and/or local standards or if not all potentialcontaminants, areas of contamination, or environmental media have beenconsidered. HRAs include cumulative risks for all contaminants reasonablyexpected to be present at a site; therefore, any and all potential contami-nants must be considered.

In addition to the analytical data for contaminated areas, the site investi-gation phase must develop analytical data for background (e.g., uncontami-nated) conditions for the various environmental media. This might includeevaluation of upgradient groundwater quality, soil in uncontaminated oroff-site locations, upwind air quality, and upstream surface water and sedi-ment quality. Background data are evaluated in the same manner as othercollected data to determine statistical validity. Many contaminants that donot occur naturally are assumed to be absent from the background.

Given the site characterization information, data suitable for an HRAmust be selected by determining whether existing data are representative ofsite conditions as they exist at the time the HRA is being completed. Eachdata set should be evaluated according to EPA guidelines regarding theappropriateness of protocols and procedures used in collecting and analyz-ing the samples (EPA 1990).

Only data that are deemed suitable for an HRA should be used in the riskcalculations. The HRA report should contain a summary of data selected for




TABLE 2-4. Suggested Outline for Baseline Risk Assessment Report

1. INTRODUCTIONOverviewSite BackgroundScope of Risk AssessmentOrganization of Risk Assessment Report

2. IDENTIFICATION OF CHEMICALS OF POTENTIAL CONCERNGeneral Site-Specific Data Collection ConsiderationsGeneral Site-Specific Data Evaluation ConsiderationsEnvironmental Area or Operable Unit 1 (Complete for All Media)Environmental Area or Operable Unit 2(Repeat for All Areas or Operable Units, as Appropriate)

3. EXPOSURE ASSESSMENTCharacterization of Exposure SettingIdentification of Exposure PathwaysQuantification of ExposureIdentification of UncertaintiesSummary of Exposure Assessment

4. TOXICITY ASSESSMENTToxicity Information for Noncarcinogenic EffectsToxicity Information for Carcinogenic EffectsChemicals for which No EPA Toxicity Values Are AvailableUncertainties Related to Toxicity InformationSummary of Toxicity Information

5. RISK CHARACTERIZATIONCurrent Land-Use ConditionsFuture Land-Use ConditionsUncertaintiesComparison of Risk Characterization Results with Human StudiesSummary Discussion and Tabulation of the Risk Characterization

6. SUMMARYChemicals of Potential ConcernExposure AssessmentToxicity AssessmentRisk Characterization



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