United States
Environmental Protection
Agency
Office of Emergency and
Remedial Response
Washington, D.C. 20460
EPA/540/2-91/020A
September 1991
for Conducting
Treatability Studies
Under CERCLA:
Soil Washing
Interim Guidance
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EPA/540/2-91/020A
September 1991
GUIDE TO CONDUCTING
TREATABILITY STUDIES UNDER CERCLA:
SOIL WASHING
INTERIM GUIDANCE
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
and
Office of Emergency and Remedial Response
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
Washington, D.C. 20460
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DISCLAIMER
This material has been funded wholly or in part by the United States
Environmental Protection Agency (EPA) under contract No. 68-C8-0061.
Work Assignment No. 2-06, to Science Applications International Corpo-
ration (SAIC). It has been subj ect to the Agency' s peer and administrative
reviews and it has been approved for publication as an EPA document.
Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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FOREWORD
Today's rapidly developing and changing technologies and industrial
products and practices frequently carry with them the increased
generation of materials that, if improperly dealt with, can threaten both
public health and the environment. The U.S. Environmental Protection
Agency (EPA) is charged by Congress with protecting the Nation's land,
air, and water resources. Under a mandate of national environmental laws,
the Agency strives to formulate and implement actions leading to a
compatible balance between human activities and the ability of natural
systems to support and nurture life. These laws direct the EPA to perform
research to define our environmental problems, measure the impacts, and
search for solutions.
The Risk Reduction Engineering Laboratory (RREL), is responsible for
planning, implementing, and managing research, development, and
demonstration programs to provide an authoritative, defensible
engineering basis in support of the policies, programs, and regulations of
the EPA with respect to drinking water, wastewater, pesticides, toxic
substances, solid and hazardous wastes, and Superfund-related activities.
This publication is one of the products of that research and provides a
vital communication link between the researcher and the user community.
This document provides guidance for planning, implementing, and
evaluating soil washing treatability tests to support the remedy evaluation
process for Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA) sites. Additionally, it describes a three-tiered
approach, which consists of 1) remedy screening, 2) remedy selection, and
3) remedy design, to soil washing treatability testing. It also presents a
guide for conducting treatability studies in a systematic and stepwise
fashion to determine the effectiveness of soil washing in remediating a
CERCLA site. The intended audience for this guide comprises Remedial
Project Managers (RPMs), On-Scene Coordinators (OSCs), Potentially
Responsible Parties (PRPs), consultants, contractors, and technology
vendors.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
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ABSTRACT
Systematically conducted, well-documented treatability studies are an
important component of the remedial investigation/feasibility study
(RI/FS) process and the remedial design/remedial action (RD/RA) process
under the Comprehensive Environmental Response, Compensation, and
Liability Act (CERCL A). These studies provide valuable site-specific data
necessary to aid in the selection and implementation of the remedy. This
manual focuses on soil washing treatability studies conducted in support
of remedy selection prior to developing the Record of Decision (ROD).
This manual presents guidance for designing and implementing a soil
washing treatability study. The manual gives an overview of general
information for determining whether soil washing technology may be
effective, guidance on designing and conducting soil washing treatability
studies for remedy selection, assistance in interpreting data obtained from
remedy selection treatability studies, and guidance for estimating costs
associated with remedy design and full-scale soil washing remedial action.
The manual is not intended to serve as a substitute for communication
with experts or regulators nor as the sole basis for the selection of soil
washing as a particular remediation technology. Soil washing must be
used in conjunction with other treatment technologies since it generates
residuals. This manual is designed to be used in conjunction with the
Guide for Conducting Treatability Studies Under CERCLA (Interim
Final).'' ^ The intended audience for this guide comprises Remedial Proj ect
Managers (RPMs), On-Scene Coordinators (OSCs), Potentially
Responsible Parties (PRPs). consultants, contractors, and technology
vendors.
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TABLE OF CONTENTS
Section Page
DISCLAIMER ii
FOREWORD in
ABSTRACT iv
FIGURES vi
TABLES vii
ACKNOWLEDGMENTS vm
1. Introduction 1
1.1 Background 1
1.2 Purpose and Scope 1
1.3 Intended Audience 2
1.4 Use of This Guide 2
2. Technology Description and Preliminary Screening 3
2.1 Technology Description 3
2.2 Preliminary Screening and Technology Limitations 5
3. The Use of Treatability Studies in Remedy Evaluation 9
3.1 Process of Treatability Testing in Evaluating a Remedy 9
3.2 Application of Treatability Tests 11
4. Treatability Study Work Plan 15
4.1 Test Goals 15
4.2 Experimental Design 18
4.3 Equipment and Materials 20
4.4 Sampling and Analysis 21
4.5 Data Analysis and Interpretation 22
4.6 Reports 24
4.7 Schedule 25
4.8 Management and Staffing 26
4.9 Budget 26
5. Sampling and Analysis Plan 29
5.1 Field Sampling Plan 29
5.2 Quality Assurance Project Plan 30
6. Treatability Data Interpretation 33
6.1 Technology Evaluation 33
6.2 Estimation of Costs 34
7. References 37
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FIGURES
Figure Page
2-1. Schematic Diagram of the Major Elements of the Aqueous Soil Washing Process 3
3-1. Flow Diagram of the Tiered Approach 10
3-2. The Role of Treatabihty Studies in the RI/FS and RD/RA Process 11
4-1. Soil Washing Applicable Particle Size Range 23
4-2. Hypothetical Contaminant Distribution by Soil Fraction Before and After Treatment 23
4-3. Plot of Agitated Contact Time Versus Contaminant Removal Efficiency and Final
Contaminant Concentration in the >2 mm Soil Fraction 24
4.4. Example Project Schedule for a Treatability Study 25
4-5. Organization Chart 26
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TABLES
Table Page
2-1. Physical Prescreening Soil Characterization Tests 7
4-1. Suggested Organization of Soil Washing Treatability Study Work Plan 15
4-2. Major Cost Elements Associated with Remedy Selection Soil Washing Studies 26
5-1. Suggested Organization of Sampling and Analysis Plan 30
6-1. Potential Major Cost Estimate Components in a Remedy Design Soil Washing Field Test 35
6-2. Major Cost Estimate Components in a Full-Scale Soil Washing Operation 36
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ACKNOWLEDGMENTS
This document was prepared for the U.S. Environmental Protection
Agency, Office of Research and Development. Risk Reduction
EngineeringLaboratory (RREL), Cincinnati Ohio, by Science Applications
International Corporation (SAIC), with the support of its subcontractors,
Bruck, Hartman & Esposito, Inc.. and Chapman. Inc.. under Contract No.
68-C8-0061. Mr. Mike Borst and Ms. Malvrna Wilkens served as the EPA
Technical Project Monitors. Dr. Thomas Fogg and Mr. Jim Rawe were
SAIC's Work Assignment Managers. The project team included Kathleen
Hurley, Curtis Schmidt, Cynthia Eghbalnia, and Yueh Chuang of SAIC; Pat
Esposito of Bruck, Hartman & Esposito, Inc.; and James Nash of
Chapman, Inc. Dr. Robert Shokes and Mr. Clyde Dial served as SAIC's
Senior Reviewers, and Robert Coleman served as Technical Editor.
The following Agency and Contractor personnel have contributed their
time and comments by participating in the protocol workshop and/or peer
reviewing the draft document:
Michael Amdurer
Robin Anderson
Ben Blaney
Clyde Dial
Chi-Yuan Fan
Howard Feiler
Frank Freestone
Paul Leonard
Jim Orban
Caroline Roe
Ronald Taylor
Richard Traver
Thomas Wagner
Darlene Williams
Andre Zownir
Ebasco
EPA, OERR
EPA, RREL
SAIC, Cincinnati
EPA, RREL
SAIC, Paramus
EPA, RREL
EPA, Region III
EPA, Region IV
EPA, OERR
USD A, Soil Conservation Service
EPA, RREL
SAIC, Cincinnati
EPA, RREL
EPA. OSWER
The document was also reviewed by the Office of Waste Programs
Enforcement and the Technology-' Innovation Office. We sincerely hope
we have not overlooked anyone who participated in the development of
this guide.
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SECTION 1
INTRODUCTION
1.1 BACKGROUND
Section 121 (b) of the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA)
mandates the Environmental Protection Agency (EPA) to
select remedies that "utilize permanent solutions and
alternative treatment technologies or resource recovery
technologies to the maximum extent practicable'' and to
prefer remedial actions in which treatment that "permanently
and significantly reduces the volume, toxicity, or mobility of
the hazardous substances, pollutants, and contaminants is a
principal element." Treatability studies provide data to
support treatment technology selection and remedy
implementation. If treatability studies are used, they should
be performed as soon as it is evident that insufficient
information is available to support the remedial decision.
Conducting treatability studies early in the remedial
investigation/feasibility study (RI/FS) process reduces
uncertainties associated with selecting the remedy and
provides a sound basis for the Record of Decision (ROD).
EPA Regional planning should factor in the time and
resources required for these studies.
Treatability studies conducted during the RI/FS phase
indicate whether the technology can meet the cleanup goals
for the site. Treatability studies conducted during the
remedial design/remedial action (RD/RA) phase establish
design and operating parameters for optimization of
technology performance. Although the purpose and scope of
these studies differ, they complement one another since
information obtained in support of remedy selection may also
be used to support the remedy design.(24)
This document refers to three levels or tiers of treatability
studies: remedy screening, remedy selection, and remedy
design. Three tiers of treatability studies are also defined in
the Guide for Conducting Treatability Studies Under
CERCLA, Interim FinaF5), referred to as the ''generic
guide" hereafter in this document. The generic guide refers
to the three treatability study tiers, based largely on the scale
of test equipment, as laboratory screening, bench-scale
testing, and pilot-scale testing. Laboratory
screening is typically used to screen potential remedial
technologies and is equivalent to remedy screening.
Bench-scale testing is typically used for remedy selection,
but may not provide enough information for remedy
selection. Bench-scale studies can, in some cases, provide
enough information for full-scale design. Pilot-scale studies
are normally used for remedial design, but may be required
for remedy selection in some cases. Because of the overlap
between these tiers, and because of differences in the
application of each tier to different technologies, the
functional description of treatability study tiers (i.e., remedy
screening, remedy selection, and remedy design) has been
chosen for this document.
Some or all of the levels may be needed on a case-by-case
basis. The need for and the level of treatability testing
required are management decisions. The time and cost
necessary to perform the testing are balanced against the
improved confidence in the selection of treatment
alternatives. These decisions are based on the quantity and
perceived quality of data available and on other factors (e.g.,
State and community acceptance of the remedy or new site
data on experience with the technology). Section 3 discusses
using treatability studies in remedy selection in greater detail.
1.2 PURPOSE AND SCOPE
This guide helps ensure a reliable and consistent approach in
evaluating soil washing as a consideration for site
remediation. This guide discusses the remedy screening and
remedy selection levels of treatability testing. Remedy
screening studies provide a quick and relatively inexpensive
indication of whether soil washing is a potentially viable
remedial technology. The remedy selection treatability test
provides data to help determine if reductions in contaminant
volumes will allow cost-effective treatment of residual
contamination to meet cleanup goals. Remedy selection
studies also provide preliminary estimates of the cost and
performance data necessary to design either a remedy
design study or a full-scale soil washing system.
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In general, remedy design studies will also be required to
determine if soil washing is a viable treatment alternative for
a site. Remedy design studies are conducted after the ROD
and are typically vendor-specific. Therefore, remedy design
is not discussed in this guidance document.
1.3 INTENDED AUDIENCE
This document is intended for the use of Remedial Project
Managers (RPMs), On-Scene Coordinators (OSCs),
Potentially Responsible Parties (PRPs), consultants,
contractors, and technology vendors. Each has different roles
in conducting treatability studies under CERCLA. Specific
responsibilities for each can be found in the generic guide.(15)
1.4 USE OF THIS GUIDE
This guide is organized into seven sections, which reflect the
basic information required to perform treatability studies
during the RI/FS process. Section 1 is an introduction which
provides background information on the role of the guide and
outlines its intended audience. Section 2 describes different
soil washing processes currently available and discusses how-
to conduct a remedy screening to determine if soil washing
is a potentially viable remediation technology. Section 3
provides an overview of the levels of treatability testing and
discusses how to determine the need for treatability studies.
Section 4 provides an overview of the remedy screening and
remedy selection treatability studies, describes the contents
of a typical work plan, and discusses the major issues to
consider when conducting a treatability study. Section 5
discusses sampling and analysis and quality assurance project
plans. Section 6 explains how to interpret the data produced
from treatability studies and how to determine if further
remedy design testing is justified. Section 7 lists the
references.
This guide, along with guides being developed for other
technologies, is a companion document to the generic guide.
In an effort to limit redundancy, supporting information in the
generic guide and other readily available guidance documents
is not repeated in this document.
The document is not intended to serve as a substitute for
communication with regulators and/or experts in the field of
soil washing. This document should never be the sole basis
for selecting soil washing as a remediation technology or
excluding soil washing from consideration.
As treatability study experience is gained, EPA anticipates
further comment and possible revisions to the document. For
1his reason, EPA encourages constructive comments from
outside sources. Direct written comments to:
U.S. Environmental Protection Agency
Releases Control Branch (MS 104)
Risk Reduction Engineering Laboratory
2890 Woodbridge Ave.
Bldg. 10, 2nd Floor
Edison, New Jersey 08837-3679
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SECTION 2
TECHNOLOGY DESCRIPTION AND
PRELIMINARY SCREENING
This section presents a description of various full-scale soil
washing technologies and a discussion of the information
necessary for prescreening the technology before committing
to a treatability test program. Subsection 2.1 describes
several full-scale soil washing systems. Subsection 2.2
discusses the literature and data base searches required, the
technical assistance available, and the review of field data
required to prescreen these technologies. Technology
limitations are also reviewed in this subsection.
and soil clods and then washed with fluids to remove
contaminants. To be effective, soil washing must either
transfer the contaminants to the wash fluids or concentrate
the contaminants in a fraction of the original volume, using
size separation techniques. °2) In either case, soil washing
must be used in conjunction with other treatment
technologies. Either the washing fluid or the fraction of soil
containing most of the contaminant, or both, must be treated.
Figure 2-1 presents a schematic diagram of a soils washing
process.(12)
2.1 TECHNOLOGY DESCRIPTION
Soil washing is a physicallchemical separation technology in
which excavated soil is pretreated to remove large objects
The first stage in the soil washing process is preparation of
the excavated soil. Soil preparation involves mechanical
screening of the soil feedstock to remove debris such as
rocks, roots, etc. The maximum size of particles allowed
Volatile*
Contaminated
Soil
Makeup Water
Extracting Agent(s)
(Surfactants, etc.)
Soil
Preparation
0)
Prepared
Soil
Soil Washing
Process
(2)
-Mixing
-Washing
-Rinsing
-Size Separation
Emission
Control
Treated
Air Emissions
Recycled Water
Chemicals
Slowdown
Water
Wastewater
Treatment
(3)
Treated
Water
Sludges/
Contaminated Fines
Clean Soil
Oversized Rejects
Figure 2-1. Schematic diagram of the major elements of the aqueous soil washing process.
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in the feedstock varies with the equipment used, ranging
from 10 mm (3/8 inch) up to 50 mm (2 inches).
The next stage is the soil washing process. Typically, soil
washing involves mixing, washing, rinsing, and size separation
steps. During mixing, the wash fluid is introduced to the soil
in measured proportions. At some installations, this is a
separate step. Other installations combine mixing and
washing into one step (as shown in Figure 2-1).
The intimate energetic mixing of the wash fluid with soil
constitutes the "washing" step. Intensive contact between
the soil grains and the wash fluid causes the soil
contaminants to dissolve and disperse into the water. Energy
is introduced into the mixture by high-pressure water jets,
vibration devices, and other means, depending upon the
equipment.
After the appropriate contact time, treated soil is separated
from the wash water. Coarse soil particles are separated
with a trammel or vibrating screen device. Fine particles are
separated in a sedimentation tank, sometimes with the
addition of flocculating agents. Silt is removed in a
hydrocyclone or centrifuge device. The coarse soil fraction
is rinsed with clean water to remove residual contaminants
and fine soil particles which may stiff be adhering to coarse
particles. The coarse fhaction is recovered from the process
as clean soil.
The final steps treat the remaining fine soils (fine silt and
clay) and the contaminated water mixture. The contaminated
water mixture may require precipitation and clarification to
remove the metals and fine soils as a sludge. If organic
contaminants are present, the clarifier effluent may require
treatment, typically using activated carbon, before recycling.
The fine soils, in which contaminants have been
concentrated, will normally require further treatment. If
contaminants are volatile, emission controls may be required.
In actual operation, there are more sidestreams and
equipment involved than shown in the Figure 2-1. This
equipment typically includes soil feedstock and treated soil
conveyors and earthmoving equipment for stockpiling soil.
This equipment is, however, ancillary' and not critical to
understanding the basic soil washing process.
2.1.1 Soil Washing by Phase Transfer
During soil washing, some contaminants dissolve or become
suspended in the aqueous wash fluid and are removed for
further treatment. If the washed soil meets the established
cleanup goals in the ROD, it may be returned to the original
excavation site. If unacceptable levels of contaminants
remain, the soil should be stockpiled or fed directly to the
next step for additional treatment.
Chemical agents may be added to the wash water to
increase the efficiency of contaminant removal. Acids, such
as hydrochloric acid, sulfuric acid, and nitric acid, may be
added to improve the solubility of certain contaminants,
especially heavy metals. Sodium hydroxide, sodium
carbonate, and other bases can be used to precipitate
contaminants in the extraction fluid. Clay and humus
fractions, which may contain a large percentage of organic
contaminants, are dispersed by bases.0'0 Dispersion of oily
contaminants can be facilitated by the addition of surface
active agents. Various chelating or sequestering agents, such
as citric acid, ammonium acetate, nitrilotriacetic acid (NTA),
and ethylenediaminetetraacetic acid (EDTA), will remove
the available fraction of inorganic contaminants. Combining
chemicals may improve process performance in some cases,
although limited information is available on the performance
of these combinations. Contaminant removal may be
improved, in certain cases, by elevation of the extraction
temperature or by chemical oxidation of the contaminants
using an oxidizer (e.g., hydrogen peroxide or ozone).(3)
2.1.2 Soil Washing Using Particle Size
Separation
EPA research shows that a large percentage of soil
contamination (especially organic) is sometimes associated
with, or bound to, very small (silt and clay) soil particles. In
these situations, a physical separation of the large soil
particles (sand and gravel) from the silt, clay, and humic
material effectively concentrates the contaminants. Soil
washing significantly reduces the volume of contaminated
soil when this condition occurs. Following mixing and
washing, sand particles larger than 50 to 80 um can be easily
separated from the washing fluid because of their relatively
high settling velocity. Simple, inexpensive equipment, such as
settling chambers, can be used.
Most of the clay particles and humus remain suspended in
the wash water supernatant after sand and gravel
sedimentation. These small, slow-settling particles pass
through the settling chambers. They ultimately end up in the
wastewater treatment sludge.(3)
2.1.3 Use In Conjunction With Other
Treatment Technologies
Soil washing is not usually a stand-alone technology.
Typically, both the fine soils (silts and clays) recovered after
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washing and the spent wash water are subject to further
specific treatment and disposal techniques, as appropriate, to
complete the cleanup. Wash water is normally treated using
standard wastewater treatment practices. Sludges generated
during wash water treatment may need subsequent treatment
by such methods as solidification/stabilization, biodegradation,
and incineration. The EPA document entitled, "Technology
Screening Guide for Treatment of CERCLA Soils and
Sludges." contains a detailed description of potential
treatment technologies.(22) Sidestreams generated during
treatment, such as spent solvents, exhausted resins, air
emissions, etc., must also be treated.
2.2 PRELIMINARY SCREENING AND
TECHNOLOGY LIMITATIONS
The need for and the appropriate level of treatability studies
required are dependent on available literature, expert
technical judgment, and site-specific factors. The first two
elements~the literature search and expert consultationare
critical factors in determining if adequate data are available
or whether a treatability study is needed to provide those
data.
2.2.1 Literature/Data Base Review
Several reports and electronic data bases exist which should
be consulted to assist in planning and conducting treatability
studies, and to help prescreen soil washing for use at a
specific site. Existing reports include:
Guide for Conducting Treatability Studies Under
CERCLA, Interim Final. U.S. Environmental Protection
Agency, Office of Research and Development and
Office of Emergency and Remedial Response,
Washington, D.C. EPA/540/2-89/058, December 1989.
Guidance for Conducting Remedial Investigations and
Feasibility Studies Under CERCLA, Interim Final. U.S.
Environmental Protection Agency, Office of Emergency
and Remedial Response, Washington, D.C.
EPA/540/G-89/004, October 1988.
Superfund Treatability Clearinghouse Abstracts. U.S.
Environmental Protection Agency, Office of Emergency
and Remedial Response, Washington, D.C.
EPA/540/2-89/001, March 1989.
The Superfund Innovative Technology Evaluation
Program: Technology Profiles. U.S. Environmental
Protection Agency, Office of Solid Waste and
Emergency Response and Office of Research and
Development, Washington, D.C. EPA/540/5-90/006,
November 1990.
Summary of Treatment Technology Effectiveness for
Contaminated Soil. U.S. Environmental Protection
Agency, Office of Emergency and Remedial Response,
Washington, D.C., 1989 (in press).
Technology S creening Guide for Treatment of CERCLA
Soils and Sludges. U.S. Environmental Protection
Agency. EPA/540/2-88/004, 1988.
U.S. Environmental Protection Agency, Applications
Analysis Report - CF Systems Organics Extraction
System, New Bedford, MA, EPA Report to be
published.
Currently, RREL in Cincinnati is expanding its Superfund
Treatability Data Base. This data base will contain data from
all treatability studies conducted under CERCLA. A
repository for treatability study reports will be maintained at
RREL in Cincinnati. The contact for this data base is Glenn
Shaul at (513) 569-7408.
Office of Research and Development (ORD) headquarters
maintains the Alternative Treatment Technology Information
Center (ATTIC), a comprehensive, automated information
retrieval system that integrates hazardous waste data into a
unified, searchable resource. The intent of ATTIC is to
provide the user community with technical data and
information on available alternative treatment technologies
and to serve as an initial decision support system. Since
ATTIC functions as a focal point for users, it facilitates the
sharing of information with the user community and creates
an effective network of individuals and organizations involved
in hazardous waste site remediation.
The information contained in ATTIC consists of a wide
variety of data obtained from Federal and State agencies.
The core of the ATTIC system is the ATTIC Data Base,
which contains abstracts and executive summaries from over
1,200 technical documents and reports. Information in the
ATTIC Data Base has been obtained from the following
sources:
The Superfund Innovativ e Technology Evaluation (SITE)
Program
California Summary of Treatment Technology
Demonstration Projects
Data collected for the Summary of Treatment
Technology Effectiveness for Contaminated Soil
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North Atlantic Treaty Organization (NATO)
International Data
Innovative Technologies Program Data
Removal Sites Technologies Data
Resource Conservation and Recovery Act (RCRA)
Delisting Actions
USATHAMA Installation Restoration and Hazardous
Waste Control Technologies
Records of Decision (from 1988 on)
Treatability Studies
Superfund Treatability Data Base (also available through
ATTIC)
In addition, the ATTIC system contains a number of resident
data bases that have been previously developed, as well as
access to on-line commercial data bases. For more
information, contact the ATTIC System Operator at (301)
816-9153.
The Office of Solid Waste and Emergency Response
(OSWER) maintains an Electronic Bulletin Board System
(BBS) as a tool for communicating ideas and disseminating
information and as a gateway for other Office of Solid
Waste (OSW) electronic data bases. Currently, the BBS has
eight different components, including news and mail sendees
and conferences and publications on specific technical areas.
The contact is James Cummings at (202) 382-4686.
2.2.2 Technical Assistance
Technical assistance can be obtained from the Technical
Support Project (TSP) team, which is made up of six
Technical Support Centers and two Technical Support
Forums. It is a joint service of the Office of Solid Waste and
Emergency Response, the Office of Research and
Development, and the Regions. The TSP offers direct
site-specific technical assistance to On-Scene Coordinators
(OSCs) and RPMs and develops technology workshops,
issue papers, and other information for Regional staff. The
TSP:
Reviews contractor work plans, evaluates remedial
attematives, reviews RI/FS, and assists in the selection
and design of the final remedy
Offers modeling assistance and data analysis and
interpretation
Assists in developing and evaluating sampling plans
Conducts field studies (soil gas, hydrogeology, site
characterization)
Develops technical workshops and training, issue papers
on groundwater topics, and generic protocols
Assists in performing treatability studies.
The following support centers provide technical information
and advice related to soil washing and treatability studies:
1. GroundwaterFate and Transport Technical Support
Center
Robert S. Kerr Environmental Research Laboratory
(RSKERL), Ada, Oklahoma
Contact: Don Draper
FTS 743-2202 or (405) 332-8800
RSKERL in Ada, Oklahoma, is EPA's center for fate and
transport research. It focuses its efforts on transport and fate
of contaminants in the vadose and saturated zones of the
subsurface, methodologies relevant to protection and
restoration of groundwater quality, and evaluation of
subsurface processes for the treatment of hazardous waste.
The Center provides technical assistance, such as evaluating
remedial alternatives; reviewing RI/FS and RD/RA work
plans; and providing technical information and advice.
2. Engineering and Treatment Technical Support
Center
Risk Reduction Engineering Laboratory (RREL),
Cincinnati, OH
Contact: Ben Blaney
FTS 648-7406 or (513) 569-7406
The Engineering and Technical Support Center (ETSC) is
sponsored by OSWER but operated by RREL. The center
handles site-specific remediation engineering problems.
Access to this support Center must be obtained through the
EPA Remedial Project Manager.
RREL offers expertise in contaminant source control
structures; materials handling and decontamination; treatment
of soils, sludges and sediments; and treatment of aqueous
and organic liquids. The following are examples of the
technical assistance that can be obtained through ETSC:
Screening of treatment alternatives
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Review of the treatability aspects of RI/FS
Review of RI/FS treatability study Work Plans and final
reports
Oversight of RI/FS treatability studies
Evaluation of alternative remedies
Assistance with studies of innovative technologies
Assistance in full-scale design and start-up
2.2.3 Prescreening Characteristics
The need for a treatability study is determined near the
beginning of the RI/FS when a literature survey of remedial
technologies is performed. Remedial technologies are
identified based on compatibility with the type of
contaminants and the media (soil, water, etc.) present at the
site, and the anticipated cleanup objectives. Remedial
technologies are prescreened for effectiveness,
implementability, and cost. The prescreening is done using
available technical literature, data bases and manufacturer's
information. Based on this initial technology prescreening, soil
washing may be one of several candidate remedial
technologies eliminated before or during the RI/FS. See the
generic guide for more specific details on screening of
treatment technologies and on determining the need and type
of treatability tests which may be required for evaluating
treatment technology alternatives.05'
Prescreening activities for soil washing treatability testing
include interpreting any available site-related field
measurement data. The purpose of prescreening is to gain
enough information to eliminate from further treatability
testing treatment technologies that have little chance of
achieving the cleanup goals.
Table 2-1 lists physical parameters that may be measured or
available before designing treatability tests. Particle size
distribution and cation exchange capacity (CEC)
measurements are particularly useful when evaluating soil
washing.
If contamination exists at different soil zones, a soil
characterization profile should be developed for each soil
type or zone. Available chemical and physical data (including
averages and ranges) and the volumes of the contaminated
soil requiring treatment should be identified. Hot spots require
separate characterizations so they can be properly addressed
in the treatability tests. Soil washing may be applicable to
some, but not all, parts of a site.
Characterization test results should be broadly representative
of the waste profile of the site. Grab samples taken from the
site ground surface may represent only a small percentage of
the contaminated soils requiring remediation. Deeper,
subsurface strata affected by contaminants may vary widely
in composition (grain size, clay content, cation exchange
capacity, total organic carbon, and contamination levels) from
those found at the surface and should also be characterized.
If significant sand or clay lenses are present in the
contaminated zone, the location and volume should be
estimated. This information is critical to determine the mix of
feedstocks to be used. The quantity' and distribution of rubble
and debris should also be determined as part of the
characterization. This material must be removed from the
feedstock material during any full-scale treatment operations.
In general, existing commercial soil washers cannot accept
material larger than 3/8 to 2 (10 to 50 mm) inches in
diameter.
The three most important soil parameters to be evaluated
during prescreening and remedy screening tests are the
grain size distribution, clay content, and cation exchange
capacity'. Soil washing performance is closely tied to
TABLE 2-1. Physical Prescreening Soil Characterization Tests
Parameter
Grain size analysis/
Description of Test
Sieve screening using #10
Standard Analytical
Method
ASTM D422
Reference
1
particle size distribution
Cation exchange capacity
(CEC)
and #60 screens or
equivalent
Ammonium acetate
Sodium acetate
Method 9080
Method 9081
23
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these three factors. Soils with relatively large percentages of
sand and gravel (coarse material >2 mm) respond better to
soil washing than soils with small percentages of sand and
gravel. Larger percentages of clay and silt (fine particles
smaller than 0.25 mm) reduce contaminant removal
efficiency. In general, soil washing is most appropriate for
soils that contain at least 50 percent sand/gravel, i.e., coastal
sandy soils and soils with glacial deposits. Soils rich in clay
and silt tend to be poor candidates for soil washing. Cation
exchange capacity measures the tendency of the soil to
exchange weakly held cations in the soil for cations in the
wash solution. Soils with relatively low CEC values (less than
50 to 100 meq/kg) respond better to soil washing than soils
with higher CEC values. Early characterization of these
parameters and their variability throughout the site provides
valuable information for the initial screening of soil washing
as an alternative treatment technology. Appendix C of the
generic guide lists other specific characterization
parameters.(15)
Chemical and physical properties of the contaminant should
also be investigated. Solubility in water (or other washing
fluids) is one of the most important physical characteristics.
Reactivity with wash fluids may, in some cases, be another
important characteristic to consider. Other contaminant
characteristics such as volatility and density may be
important for the design of remedy screening studies and
related residuals treatment systems. Speciation, is important
in metal-contaminated sites. Specific metal compounds
should be quantified rather than total metal concentration for
each metal present at the site. Soil prescreening
characterization data should be assembled and organized in
a concise tabular form before designing the remedy
screening tests.
2.2.4 Soil Washing Limitations
Soil washing limitations may be defined as characteristics
that hinder cost-effective soil treatment. The limitation may
be due to the soil particle distribution (high percentage of silt,
clay, or organic matter), the contaminant (high concentration
of mineralized metals or hydrophobic organics), or the
process itself. High concentrations of additives may be
required in some cases to meet the necessary performance
goals. Difficulties are sometimes encountered in treating and
recycling additives in the spent wash water. If these
conditions occur, process costs may be prohibitive due to the
cost of treating washing fluids and replenishing additives.
Hydrophobic contaminants can be difficult to separate from
soil particles into the aqueous washing fluid. Estimated
aqueous distribution coefficients (KJ, also known as partition
coefficients. (Kp), indicate the fraction of the contaminant
expected to remain on the soil particle versus the fraction of
the contaminant dissolved in the water. (6) Alternative
methods can be used to estimate these values when tabulated
values cannot be located.(S) A contaminant with a high K,,
(e.g., PCB > 10,000) is more difficult to wash off the soil
particles using water than a contaminant with a lower K,,
(e.g., TCE=3). Additives such as surfactants may be
required to improve removal efficiencies. However, larger
volumes of washing fluid may be needed when additives are
used.
Complex mixtures of contaminants in the soil, such as a
mixture of metals, nonvolatile organics, sernivolatile organics,
etc., make it difficult to formulate a single suitable washing
fluid that will remove all the different types of contaminants
from the soil. Sequential washing steps, using different
additives, may be needed. Frequent changes in the
contaminant type and concentration in the feed soil can
disrupt the efficiency of the soil washing process. To
accommodate changes in the chemical or physical
composition of the feed soil, modifications to the wash fluid
formulation and the operating settings may be required.
Alternatively, additional feedstock preparation steps, such as
blending soils to provide a consistent feedstock; may be
appropriate.
High humic content in the soil makes separation of
contaminants very difficult. Humus consists of decomposed
plant and animal residues and offers binding sites for
accumulation of both organics and metals. A high percentage
of clay and silt (e.g., more than 30 to 50 percent) in the soil
usually indicates that soil washing will be unfavorable due to
the amount of time and money required to treat this volume
of contaminated soil. A volume reduction process like soil
washing is most cost-effective when the cleaner soil fraction
is much larger than the more contaminated soil fraction.
Chelating agents, surfactants, solvents, and other additives
are often difficult and expensive to recover from the spent
washing fluid and then recycle in the soils washing process.
The presence of additives may make the spent washing fluid
difficult to treat by conventional treatment processes such as
settling, chemical precipitation, or activated carbon. The
presence of additives in the contaminated soil and treatment
sludge residuals may cause increased difficulty in disposing
of these residuals.
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SECTION 3
THE USE OF TREATABILITY STUDIES
IN REMEDY EVALUATION
This section presents an overview of the use of treatability
tests in confirming the selection of soil washing as the
technology remedy under CERCLA. It also provides a
decision tree that defines the tiered approach to the overall
treatability study program with examples of the application of
treatability studies to the RI/FS and remedy evaluation
process. Subsection 3.1 presents an overview of the general
process of conducting treatability tests. Subsection 3.2
defines the tiered approach to conducting treatability studies
and the applicability of each tier of testing, based on the
information obtained, to assess, evaluate, and confirm soil
washing technology as the selected remedy.
3.1 PROCESS OF TREATABILITY
TESTING IN EVALUATING A
REMEDY
Treatability studies should be performed in a systematic
fashion to ensure that the data generated can support the
remedy evaluation process. This section describes a general
approach that should be followed by RPMs, PRPs, and
contractors during all levels of treatability testing. This
approach includes:
Establishing data quality objectives
Selecting a contracting mechanism
Issuing the Work Assignment
Preparing the Work Plan
Preparing the Sampling and Analysis Plan
Preparing the Health and Safety Plan
Conducting community relations requirements
Complying with regulatory requirements
Executing the study
Analyzing and interpreting the data
Reporting the results
These elements are described in detail in the generic guide.
(15) That document gives information applicable to all
treatability studies. It also presents information specific to
each of the levels of treatability testing.
Treatability studies for a particular site will often entail
multiple tiers of testing. Duplication of effort can be avoided
by recognizing this possibility in the early planning phases of
the project. The Work Assignment, Work Plan, and other
supporting documents should include all anticipated activities.
There are three levels or tiers of treatability studies: remedy
screening, remedy selection, and remedy design testing.
Some or all of the levels may be needed on a case-by-case
basis. The need for and the level of treatability testing
required are management decisions in wrhich the time and
cost necessary to perform the testing are balanced against
the risks inherent in the decision (e.g., selection of an
inappropriate treatment alternative). These decisions are
based on the quantity and perceived quality of data available
and on other decision factors (e.g., State and community
acceptance of the remedy or new site data). The flow
diagram for the tiered approach in Figure 3-1 traces the
stepwise review of data with the decision points and factors
to be considered.
Technologies generally are evaluated first at the remedy
screening level and progress through remedy selection to the
remedy design testing. A technology may enter the selection
process, however, at whatever level is appropriate based
on available data on the technology and site-specific
factors. For example, a technology that has been
successfully applied at a site with similar conditions and
contaminants may not require remedy screening to determine
whether it has the potential to work. Rather, it may
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I
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Remedial Investigation/
Feasibility Study (RI/FS)
Identification
of Alternatives
Record of
Decision
(ROD)
Remedy
Selection
Remedial Design/
Remedial Action -
(RD/RA)
Scoping
- the -
RI/FS
Literature
Screening
and
Treatability
Study Scoping
Site
Characterization
and Technology
Screening
REMEDY
SCREENING
to Determine
Technology Feasibility
Evaluation
of Alternatives
REMEDY SELECTION
to Develop Performance
and Cost Data
Implementation
of Remedy
REMEDY DESIGN
to Develop Scale-Up, Design,
and Detailed Cost Data
FIGURE 3-2. The role of treatability studies in the RI/FS and RD/RA process.
go directly to remedy selection testing to verify that
performance standards can be met and generate preliminary
cost estimates. Treatability studies, at some level, will
normally be needed to assure that the technology can
achieve site target cleanup goals even if previous studies or
actual implementation have encompassed similar site
conditions. Figure 3-2 shows the relationship of the three
levels of a treatability study to each other and to the RI/FS
process.
3.2 APPLICATION OF TREATABILITY
TESTS
Before conducting treatability studies, the objectives of each
tier of testing must be established. Soil washing treatability
study objectives are based on the specific needs of the
RI/FS. There are nine evaluation criteria specified in the
document, Guidance for Conducting Remedial Investigations
and Feasibility Studies Under CERCLA (Interim Final);(14)
the treatability studies provide data for up to seven of these
criteria. These seven criteria are:
Overall protection of human health and environment
Compliance with applicable or relevant and appropriate
requirements (ARARs)
Reduction of toxicity, mobility, or volume through
treatment
Short-term effectiveness
Implementability
Long-term effectiveness and permanence
Cost
The first four of these evaluation criteria deal with the
degree of contaminant reduction achieved by the soil
washing process. What will be the remaining contaminant
concentrations? Will the residual contaminant levels be
sufficiently low to meet the established ARARs and the
risk-based contaminant cleanup levels? What are the
contaminant concentration and physical and chemical differ-
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ences between the untreated and the washed soil fractions
(i.e., has contaminant toxicity, mobility, and volume been
reduced)? The fourth criterion, short-term effectiveness,
addresses the risks posed by the treatment technology during
construction and implementation of a remedy.
The implementability assessment evaluates the technical and
administrative feasibility of the technology and the availability
of required goods and services. The following questions must
be answered in order to address the implementability of soil
washing:
What is the percentage of clay, silt, and humic matter
requiring additional treatment?
What additives will be required (e.g., chelating agents or
surfactants) that might make residuals treatment and
disposal difficult?
What are the characteristics and the volume of the
sludge that will be produced?
Is sufficient water available at the site, and is it suitable
for process use?
Normally, the required equipment and washing solutions are
available. However, alterations to process design may be
necessary on a site-by-site basis to accommodate different
soils and contaminants. Sidestreams and residual soil from
the soil washing process require additional treatment. The
implernentability assessment must include these additional
treatments.
Long-term effectiveness assesses how effective treatment
technologies are in maintaining protection of human health
and the environment after response objectives have been
met. The magnitude of any residual risk and the adequacy
and reliability of controls must be evaluated. Residual risk, as
applied to soil washing, assesses the risks associated with the
treatment residuals at the conclusion of all remedial activities.
Analysis of residual risk from sidestream and other treatment
train processes should be included in this step. An evaluation
of the reliability of treatment process controls assesses the
adequacy and suitability of any long-term controls (such as
site access restrictions and deed limitations on land use) that
are necessary to manage treatment residuals at the site. Such
assessments are usually beyond the scope of a remedy
selection treatability study, but may be addressed
conceptually based on remedy selection results. Performance
objectives must consider the existing site soil contaminant
levels and relative cleanupgoals for the site. In previous
years, cleanup goals often reflected background site
conditions, Attaining background cleanup levels through
treatment has proven impractical in many situations. The
present trend is toward the development of site-specific
cleanup target levels that are risk-based rather than based on
background levels.
The final EPA evaluation criterion that can specifically be
addressed during a treatability study is cost. Soil washing is
basically a volume reduction technology that uses wash
water to separate contaminated soil into two fractions: a
large fraction of relatively clean, coarse soil and a smaller
fraction of fine soil/sludge containing the concentrated
contaminants.
Remedy selection treatability studies can provide data to
estimate the following important cost factors:
Recoverable clean soil fraction (the achievable volume
reduction)
The volume and characteristics of the concentrated fine
soil and sludge fractions requiring treatment or disposal
The degree to which the additives can enhance the
process efficiency
The degree to which the additives can be recovered and
recycled
The ratio of additives to soil
The ratio of soil to wash water
The first three factors provide information about the costs of
downstream treatments by determining the amount and
character of the contaminated residuals. The last three
factors help estimate the costs of supplies and utilities.
3.2.1 Remedy Screening
Remedy screening is the first testing level. It establishes the
ability of a technology to treat a specific waste. These
studies are generally low cost (e.g., $10,000 to $50,000) and
usually require hours to days to complete. The lowest level
of quality7 control is required for remedy screening studies.
They yield data enabling qualitative assessment of a
technology's potential to meet performance goals. Remedy
screening tests can identify operating conditions for
investigation during remedy selection or remedy design
testing. They generate little, if any, design or cost data and
should never be used as the sole basis for selection of a
remedy.
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Soil washing treatability studies are frequently slapped during
remedy screening. Often, there is enough information about
the physical and chemical characteristics of the soil and
contaminant to allow an expert to evaluate the potential
success of soil washing at a site. When performed, remedy
screening tests are jar tests. However, remedy selection tests
are normally the first level of treatability study executed.
3.2.2 Remedy Selection
Remedy selection testing is the second level of testing.
Remedy selection tests identify the technology's performance
for a site. These studies have a moderate cost (e.g., $20,000
to $100,000) and require several weeks to complete. Remedy-
selection tests yield data that verify that the technology can
meet expected cleanup goals, provide information in support
of the detailed analysis of alternatives (i.e., seven of the nine
evaluation criteria), and give indications of optimal operating
conditions.
The remedy selection tier of soil washing testing typically
consists of laboratory tests which provide sufficient
experimental controls such that a semi-quantitative mass
balance can be achieved. Toxicity testing of the cleaned soil
is typically employed in the remedy selection tier of
treatability testing. The key question to be answered during
remedy selection testing is how much of the soil will be
treated by either particle size separation or solubilization to
meet the cleanup goal by this process. The exact removal
efficiency needed to meet the specified goal for the remedy
selection test is site-specific. Pilot-scale tests may be
appropriate to support the remedy selection phase for
innovative technologies such as soil washing. Typically, a
remedy design study would follow a successful remedy
selection study.
3.2.3 Remedy Design
Remedy design testing is the third level of testing. It provides
quantitative performance, cost, and design information for
remediating an operable unit. This testing also produces the
remaining data required to optimize performance. These
studies are of moderate to high cost (e.g., $ 100,000 to
$500,000) and require several months to complete. For
complex sites (i.e., sites with different types or
concentrations in different areas or with different soil types
in different areas), longer testing periods may be required,
and costs will be higher. Remedy design tests yield data that
verify performance to a higher degree than remedy selection
tests and provide detailed design information. They are
performed after the ROD during the remedy implementation
phase of a site cleanup.
Remedy design tests usually consist of bringing a mobile
treatment unit onto the site, or constructing a small-scale
(pilot) unit for nonmobile technologies. Permit exclusions may
be available for offsite treatability studies under certain
conditions. The goal of this tier of testing is to confirm the
cleanup levels and treatment times specified in the Work
Plan (see Section 4.1.1). This is best achieved by operating
a field unit under conditions similar to those expected in the
full-scale remediation project.
Data obtained from the remedy design tests are used to:
Design the full-scale unit
Refine cleanup time estimates
Refine cost predictions
Given the lack of full-scale experience with innovative
technologies, remedy design testing will generally be
necessary- to support remedy selection and implementation.
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SECTION 4
TREATABILITY STUDY WORK PLAN
Section 4 of this document is written assuming that a
Remedial Project Manager is requesting treatability studies
through a work assignment/work plan mechanism. Although
the discussion focuses on this mechanism, it would also apply
to situations where other contracting mechanisms are used.
This section focuses on specific elements of the Work Plan
for soil washing treatability studies. The elements include test
objectives, experimental design and procedures, equipment
and materials, reports, schedule, management and staffing,
and budget. These elements are described in Sections 4.1-
4.9. Complementing the above subsections are Section 5,
Sampling and Analysis Plan, which contains a Field Sampling
Plan and a Quality Assurance Project Plan, and Section 6,
Treatability Data Interpretation. These sections address the
Sampling and Analysis and Data Analysis and Interpretation
elements of the Work Plan. Table 4-1 lists the other
remaining Work Plan elements
Carefully planned treatability studies are necessary to ensure
that the data generated are useful for evaluating the validity
or performance of a technology. The Work Plan, prepared
by the contractor when the Work Assignment is in place, sets
forth the contractor's proposed technical approach for
completing the tasks outlined in the Work Assignment. It
assigns responsibilities and establishes the project schedule
and costs. The Work Plan must be approved by the RPM
before initiating subsequent tasks. For more information on
each of these sections, refer to the generic guide.050
4.1 TEST GOALS
Setting goals for the treatability study is critical to the
ultimate usefulness of the data generated. Objectives must
be defined before starting the treatability study. Each tier of
treatability study needs performance goals appropriate to that
tier. For example, remedy selection tests are used to answer
the question, "Will soil washing work on this soil/
contaminant matrix?" It is necessary to define "work"
TABLE 4-1. Suggested Organization of Soil Washing
Treatability Study Work Plan
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Work Plan Elements
Project Description
Remedial Technology Description
Test Objectives
Experimental Design and
Procedures
Equipment and Materials
Sampling and Analysis
Data Management
Data Analysis and Interpretation
Health and Safety
Residuals Management
Community Relations
Reports
Schedule
Management and Staffing
Budget
sub-
section
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
(i.e., set the goal of the study). A contaminant reduction of
approximately 90 percent in the >2 mm soil fraction indicates
that further testing for remedy design is appropriate.
The ideal technology performance goals are the cleanup
criteria for the site. For several reasons, such as ongoing
waste analysis and ARARs determination, cleanup criteria
are sometimes not finalized until the ROD is signed, long
after treatability studies must be initiated. Nevertheless,
treatability study goals need to be established before the
study is performed so that the success of the treatability
study can be assessed. In many instances, this may entail an
educated guess as to what the final cleanup levels may be.
In the absence of set cleanup levels, the RPM can estimate
performance goals for the treatability studies based on the
first four criteria listed on page 11. Previous treat-
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ability study results may provide the basis for an estimate of
the treatability study goals in this case.
4.1.1 Remedy Screening Goals
Remedy screening tests are not always performed for soil
washing processes (see Section 3). If remedy screening tests
are performed, an example of the goal for those tests would
be to show that the wash fluid will solubilize or remove a
sufficient percentage (e.g., 50 percent) of the contaminants
to warrant further treatability studies. Another goal might be
to show that contaminant concentrations can be reduced by
at least 50 percent in the >2 mm soil fraction, using particle
size separation techniques.
These goals are only examples. The remedy screening
treatability study goals must be determined on a site-specific
basis.
Achieving the goals at this tier merely indicates that soil
washing has a chance of success and that further studies
will be useful. Frequently, such information is available based
on the type of soil and contaminant present at the site. Based
on such information, experts in soil washing technology can
often assess the potential applicability of soil washing without
performing remedy screening.
Example 1 describes a hypothetical site and a series of
simple jar tests that were used to evaluate the potential to
Example 1. Remedy Screening
An industrial facility in the southeastern United States was built in 1960 and operated until 1990. During that
time, various electronic component assembly and electroplating operations were conducted at the site.
Between 1960 and 1980, sludges and other process related wastes generated at the plant were buried in
onsite landfills. Sometimes, plating/etching solutions and other liquids were disposed of by open dumping
onto the ground or into sand-filled pits constructed for this purpose.
As a results of these past practices, soils in several areas at the site are contaminated with heavy metals,
namely copper, chromium, lead, nickel, and cadmium. Initial site investigations have shown that the average
and maximum sample values for metals found in soil borings are as follows:
Metal
Copper
Lead
Chromium
Nickel
Cadmium
Average
(MaLka)
2,500
1,000
1,200
450
75
Maximum
20,000
7,500
4,000
790
200
Soil borings at the site have shown that most of the contamination is located 4 to 6 feet below grade. About
5,000 to 10,000 cubic yards of soil are believed to be affected by the metals and volatile organic compounds
(VOCs).
Soils were described in the boring logs as clayey sands. A sample of soil, composited from soil borings
cuttings from various areas and depths in the contaminated zone, was sent to the lab for dry sieve particle
size analysis (ASTM methods); results indicated that 38 to 45 percent of the soil particles are >2 mm in
diameter, and 5 to 11 percent are between 1 mm and 2 mm in diameter.
Soil washing was considered as a potential technology to reduce the volume of contaminated soil for two
reasons. First, the sieve analysis showed that a large percentage of the soil (38 to 45 percent) was coarse
sand or gravel (>2 mm in particle size diameter). This indicated that a large percentage of the soil was likely
to respond favorably to soil washing and therefore could be eliminated from further treatment. Research at
the EPA and elsewhere has shown that soil washing is typically most effective in removing contaminants
from the >2 mm fraction. Second, the large quantity of soil affected by metal contaminants could potentially
justify the cost of assembling and operating on onsite washing system.
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A series of simple jar tests was conducted on the site using both hot and cold water to wash a composite
soil sample that broadly represented soil areas known to be contaminated with metals. Equal quantities of
soil and water were placed in ajar, shaken, and then poured across a #10 sieve screen. The particles lying
on the top of the sieve were rinsed with water and allowed to drip dry. The dry soil was then placed in a
clean, tared sample jar, weighed, and sent to the laboratory for total metal analysis. The tests were repeated
three times to measure variability. Average results showed that the soil washed with hot water (>2 mm
fraction) responded the best; the average metal concentrations in the soil before and after hot water washing
are shown below:
Metal
Soil Concentration
Before Washing
(i.e., whole soil, mg/kg)
Soil Concentration After
Hot Water Washing
(i.e., >2 mm fraction, mg/kg)
Copper
Lead
Chromium
Nickel
Cadmium
2,000
1,200
800
400
50
500
300
100
50
15
(75% red.)
(75% red.)
(88% red.)
(88%red.)
(70% red.)
The test results indicate that metal reductions on the order of 70 to 88 percent are readily achievable with hot water.
Product/soil recovery rates on the order of 30 to 50 percent (based on comparison of recovered weights versus starting
weight of soil in each test) are achievable. In order to further confirm these initial findings and to maximize the efficiency
of the treatment process, bench tests are indicated.
use soil washing to remediate the site. The example
illustrates how to decide whether the remedy selection
treatability studies using soil washing should be performed.
4.1.2 Remedy Selection Treatability
Study Goals
The main objectives of this tier of testing are to:
Measure the percentage of the contaminant that can
be removed from the soil through solubilization or from
the >2 mm. soil fraction by particle size separation
Produce the design information required for the next
level of testing, should the remedy selection evaluation
indicate remedy design studies are warranted.
The actual goal for removal efficiency must be based on
site- and process-specific characteristics. The specified
removal efficiency must meet site cleanup goals, which are
based on a site risk assessment or ARARs.
Example 2 illustrates the goal of a remedy selection
treatability study at the Superfund site introduced in
Example 1. In this example, the remedy selection
treatability studies
Example 2. Remedy Selection
As followup to the jar test results discussed in Example 1, a series of bench tests were designed to more
accurately determine the feasibility of using soil washing to reduce the volume of contaminated soil at the
facility. The bench tests included a series of studies, each designed to measure a single variable while
holding all others constant. The following treatment process variables were evaluated:
Ratios of soil and wash water
Washing/mixing/agitation time
Wash water temperature
Additives such as acids, surfactants, and chelating agents
Rinse system cycles
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In all, 24 different tests were completed and each test was performed in duplicate, as a measure of variance,
for a total of 48 tests. Soils recovered on the sieves and from wash waters (filtered to remove very fine soil
particles) were analyzed for the five metals of interest using standard EPA SW846 methods. The bench
tests also evaluated the possibility of altering screen sizes to capture a larger segment of clean soil (particles
>1 mm).
The bench test results for the >2 mm fraction showed that optimal results (as measured by total metal
concentration reductions) were obtained under the following conditions:
Soil to wash water ratio of 1:2
Mixing/agitation time of 15 minutes
Wash water temperature of at least 100°F
Wash water pH of 4-5
Single 60 second rinse of the screened soil using pressure sprayer
This set of process conditions was able to reduce the concentration of all metals in the recovered >2 mm
fraction by at least 90 percent, and some by as much as 95 percent. Surfactants and chelating agents were
found to be counterproductive. They fouled the screening operations, and were not recommended for further
evaluation for this site. The tests also showed that similar results (85 to 90 percent effective reductions in
metal concentrations) could be obtained for the 1 to 2 mm particle size soil fraction. By separating the
washed soil into >1 mm and <1 mm size groups, over 50 percent of the original soil volume could be
effectively treated. However, particles smaller than 1 mm were not effectively cleaned by the process. In fact,
the <1 mm soil fraction carried higher concentrations of metals after sieving than the whole soil carried
before treatment. Hence, most of the metal contamination in these site soils is associated with soil particles
1 mm or less in diameter.
Results from the study were compared to the proposed risk-based soil cleanup goals for the site. Based on
this comparison, the study showed that the proposed cleanup goals could be met for a least 50 percent of
the soil volume through the applied use of soil washing technology.
show that site cleanup goals can be met. Soil washing is
chosen as the selected remedy in the ROD.
4.2 EXPERIMENTAL DESIGN
4.2.1 Remedy Screening Tier
Ajar test can be rapidly performed in an onsite laboratory to
evaluate the potential performance of soil washing as an
alternative technology. Jar tests are performed at the
equivalent of Analytical Levels I and II, which correspond to
field screening and field analysis, respectively.(n)
When assessing the need for jar tests, the investigator should
use available knowledge of the site location and any
preliminary analytical data on the type and concentration of
contaminants present. Soil engineering properties are
available from Soil Conservation Surveys. At this level of
treatability study, the most significant soil property is particle
size distribution. In survey documents, particle size
distribution is categorized into five groupings: fragments or
particles greater than 3 inches in diameter, and fragments
passing through #4 (4.75 mm), #10 (2.0 mm), #40 (0.425
mm), and #200 (0.07 mm) sieves. Generally, soils with a 10
to 15 percent passing rate through a #200 mesh screen have
proven ideal for soil washing. However, soil particle size is
not the only property to consider. The collective effect of all
soil and contaminant properties must be investigated. Even
soil characterized by a 95 percent passage through a #200
screen may be a possible candidate for soil washing if the
contaminant is water soluble or loosely bound to soil
particles.
Contaminant characteristics to examine during remedy
screening include solubility, miscibility, and dispersibility.
Properties of organic contaminants are generally easier to
evaluate than those of inorganic contaminants. Inorganics.
such as heavy metals, can exist in many compounds (e.g.,
oxides, hydroxides, nitrates, phosphates, chlorides, sulfates,
and other more complex mineralized forms), which can
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greatly alter their solubilities. Metal analyses typically provide
only total metal concentrations. More detailed analyses to
determine chemical speciation may be wan-anted.
The liquid used in the jar test is typically water, or water with
additives that might enhance the effectiveness of the soil
washing process. To save time and money, chemical
analyses should not be performed on the samples until there
is visual evidence that physical separation has taken place in
the j ar tests. Jar tests can yield three separate fractions from
the original soil sample. These include a floating layer, a
wastewater with dispersed solids, and a solid fraction.
Chemical analysis can be performed on each fraction.
When performing the jar test, observe if any floating
materials can be skimmed off the top. Observe whether an
immiscible, oily layer forms, either at the top or the bottom,
indicating release of an insoluble organic material. Observe
and time the solids sealing rate and depth. Sand and gravel
settle first, followed by the silt and clay. The rate and the
relative volume of the settling material will provide some
indication of the particle size distribution in the contaminated
matrix and the potential for soil washing as a treatment
alternative. Further evidence can be gained by analyzing the
settled and filtered wash water for selected indicator
contaminants of concern. If simple washing releases a large
percentage of these contaminants into the wash water, then
soil washing can be viewed favorably, and more detailed
laboratory and bench tests must be conducted.
Variations on the jar tests can include the addition of
surfactants, chelants, or other dispersant agents to the water;
sequential washing; heated water washing versus cold water;
acidic or basic wash water; and tests that include both a
wash and a rinse step. The rinse water and fine soil fraction
(<2 mm particle size) should be separated from the coarse
soil fraction (>2 mm particle size) using a #10 sieve. No
attempt should be made during jar tests to separate the soil
into discrete size fractions; this is done at the remedy
selection tier of testing as described in Section 4.2.2.
Normally, only the coarse soil fraction should be analyzed for
contamination. In general, at least a 50 percent reduction in
total contaminant concentration in the >2 mm soil fraction is
considered adequate to proceed to the remedy selection tier.
The separation of approximately 50 percent of the total soil
volume as clean soil also indicates remedy selection studies
may be warranted.
To reduce analytical costs during the remedy screening tier,
a condensed list of known contaminants must be selected as
indicators of performance. The selection of indicator analytes
to track during jar testing should be based on the following
guidelines:
1) Select one or two contaminants present in the soil that
are most toxic or most prevalent.
2) Select indicator compounds to represent other chemical
groups if they are present in the soil (i.e., volatile and
sentivolatile organics, chlorinated and nonchlorinated
species, etc.)
3) If polychlorinated biphenyls (PCBs) and dioxins are
known to be present, select PCBs as indicators in the jar
tests and analyze for them in the washed soil. It is
usually not cost-effective to analyze for dioxins and other
highly insoluble chemicals in the wash water generated
from jar tests. Check for them later in the wash water
from remedy selection tests.
4.2.2 Remedy Selection Tier
This series of tests requires electricity, water, and additional
equipment be available. The tests are run under more
controlled conditions than the jar tests. The response of the
soil sample to variable washing conditions is fully
characterized. More precision is used in weighing, mixing,
and particle size separation. There is an associated increase
in quality assurance/quality' control (QA/QC) costs. Treated
soil particles are separated during the sieve operations to
determine contaminant partitioning with particle size.
Chemical analyses are performed on the sieved soil particles
as well as on the spent wash waters. The impact of process
variables on washing effectiveness is quantified. This series
of tests is considerably more costly than jar tests, so only
samples showing promise in the remedy screening phase (jar
test) should be carried forward into the remedy selection tier.
If sufficient data are available in the prescreening step, the
remedy screening step may be slapped. Soil samples showing
promise in the prescreening step are carried forward to the
remedy selection tier. The objective of the remedy selection
soil washing design is to meet the goals discussed in Section
4.1.2.
A series of tests should be designed that will provide
information on washing and rinsing conditions best suited to
the soil matrix under study. The RREL data base should be
searched for information from previous studies. To establish
percent of contaminant removal, particle size separation, and
distribution of contaminants in the washed soil, the following
should first be studied: 1) wash time, 2) wash water-to-soil
ratio, and 3) rinse water-to-wash water ratio. Following those
studies, the effect of wash water additives on performance
should be evaluated.
Several factors must be considered in the design of soil
washing treatability studies. A remedy selection test design
should be geared to the type of system expected to
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be used in the field. Soil-to-wash water ratios should be
planned using the results from the jar tests, if jar tests are
performed. In general, a ratio of 1 part of soil to 3 parts of
wash water will be sufficient to perform remedy selection
tests. The soil and wash water should be mixed on a shaker
table for a minimum of 10 minutes and a maximum of 30
minutes. The soil-to-wash water ratio and mix times
presented here are rules of thumb to be used if no other
information is available.
Another factor to consider is the variability of the grain size
distribution. Gilsen Wet Sieve devices are recommended for
remedy selection studies. Ro-Tap or similar sieve systems
may also be used. Such devices will enhance the
completeness and reproducibility of grain size separation.
However, they are messy, expensive, and very noisy when
in operation. An alternate choice is to complete a series of
four to six replicate runs under exactly the same set of
conditions to obtain information on the variability of the grain
size separation technique. Variability in the separation
technique can be evaluated by comparing sieve screen
weights across runs and soil contaminant data for the same
fractions from each run. By identifying the range of
variability associated with repeated runs at the same
conditions, estimates can be made of the variability that is
likely to be associated with other test runs under slightly-
different conditions.
Normally, only the wash water and the soil particles captured
by the sieve screen need to be analyzed for contaminants.
Experience has shown that little additional contaminant
removal is likely to be found in the rinse water. Rinsing is
important and must be included in the procedure since it
improves the efficiency of the grain size separation/sieving
process. Rinsing separates the fine from the coarse material.
This can result in a cleaner coarse fraction and more
contaminant concentrated in the fine fraction. Contaminant
concentration in the rinse water may be determined
periodically (e.g., 10 percent of the samples) to evaluate the
performance of the wash solution. However, very little
contamination is typically dissolved in the rinse solution.
Therefore, analyses of the rinse solution may have limited
value in verifying wash solution performance.
Initially, only the coarse soil fraction and the wash water
should be analyzed for indicator contaminants. If the removal
of the indicator contaminants confirms that the technology
has the potential to meet cleanup standards at the site,
additional analyses should be performed. All three soil
fractions and all wash and rinse waters must be analyzed for
all contaminants to perform a complete mass balance. The
holding time of soil fractions in the lab before extraction and
analysis can be an important consideration for some
contaminants.
The decision on whether to perform remedy selection testing
on hot spots or composite soil samples is difficult and must be
made on a site-by-site basis. Hot spot areas should be
factored into the test plan if they represent a significant
portion of the waste site. However, it is more practical to test
the specific waste matrix that will be fed to the full-scale
system over the bulk of its operating life. If the character of
the soil changes radically (e.g.. from clay to sand) over the
depth of contamination, then tests should be designed to
separately study system performance on each soil type,
Additional guidance on soil sampling techniques and theory
can be found in Soil Sampling Quality Assurance User's
Guide/21:' and Methods for Evaluating the Attainment of
Cleanup Standards.(1S)
Additives such as oil and grease dispersants and chelating
agents can aid in removing contaminants from some soils.
However, they can also cause processing problems
downstream from the washing step. Therefore, use of such
additives should be approached with caution. Use of one or
a combination of those additives is a site-by-site
determination. Some soils do not respond well to additives.
Surfactants and chelating agents may form suspensions and
foams with soil particles during washing. This can clog the
sieves and lead to inefficient particle size separation during
screening. The result can be the recovery of soil fractions
with higher contamination than those cleaned by water alone.
Such results can make the data impossible to understand.
Additives can also complicate the rinse water process that
might follow the soil washing. Recent studies have shown
that counter-current washing-rinsing systems, incorporating
the use of hot water for the initial wash step, offer the best
performance in terms of particle size separation, contaminant
removal, and wastewater management (treatment, recycling
and discharge). Additional details regarding the performance
of surfactants and chelating agents in reducing lead
contamination in soils from battery recycling Superfund sites
can be found in Lead Battery Site Treatability Studies,
Project Summary06)
4.3 EQUIPMENT AND MATERIALS
The Work Plan should specify the equipment and materials
needed for the treatability test. For example, the size and
type of glassware or containers to be used during the test
should be specified. Standard laboratory methods normally
dictate the types of sampling containers that can be used
with various contaminant groups. The RPM should consult
such methods for the appropriate containers to be used for
the treatability studies,(23) Normally, glass containers should
be used. Stainless steel can also be used with most
contaminants. Care should be taken when using
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various plastic containers and fittings. Such materials will
absorb many contaminants and can also leach plasticizer
chemicals, such as phthalates, into the soil matrix.
Appropriate methods for preserving samples and specified
holding times for those samples should be used.
The following equipment is recommended for remedy
selection soil washing tests:
Basic Equipment
Reciprocating shaker table
Four to six 10-liter glass jars and lids
pH meter
Electric hot plate/magnetic stir mixer
Top-loading balance
Four 2-liter graduated cylinders
Timer
Stainless steel sieve screens (#10 and #60) - two sets
Four collection pans/buckets for rinse and wash water
collection
Sample jars
Scoops (disposable)
Spray device for rinsing (stainless steel garden sprayers
work well)
Filter and media
Vacuum pump
Optional Equipment
Ro-Tap
Gilsen Wet Sieve
4.4 SAMPLING AND ANALYSIS
The Work Plan should describe the procedures to be used in
field and treatability study sampling. The procedures to be
used will be site-specific.
4.4.1 Field Sampling
A sampling plan should be developed that directs the
collection of representative soil samples from the site for the
treatability test. The sampling plan is site-specific. It
describes the number, location, and volume of samples.
Heterogeneous soils, variations in the contaminant
concentration profile, and different contaminants in different
locations in the site will complicate sampling efforts. If the
objective of the remedy screening or remedy selection
treatability tier study is to investigate the performance of soil
washing at the highest contaminant concentration, the sample
collection must be conducted at a "hot spot." This will
require conducting a preliminary site sampling program to
identify the locations of highest contaminant concentration.
(This information is generated early in the RI process.) If the
soil and types of contaminants vary throughout the site,
extensive sampling may be required. If soil washing is being
considered only for certain areas of the site, the sampling
program may be simplified by concentrating on those areas.
If the objective of the remedy selection study is to investigate
the use of the technology for a more homogenous waste, an
'"average" sample for the entire site must be obtained. This
will require a statistically based program of mapping the site
and selecting sampling locations that represent the variety of
waste characteristics and contaminant concentrations
present. The selection of soil sampling locations should be
based on knowledge of the site. Information from previous
soil samples, soil gas analysis using field instrumentation, and
obvious odors or residues are examples of information that
can be used to specify sample locations.
Chapter 9 of Test Methods for Evaluating Solid Waste(23)
presents a detailed discussion of representative samples and
statistical sampling methods. Additional sources of
information on field sampling procedures can be found in the
Annual Book of ASTM Standards/0 and NIOSH Manual of
Analytical Methods (February 1984)/9) The EPA
publications Soil Sampling Quality Assurance User's
Guide(21) and Methods for Evaluating the Attainment of
Cleanup Standards(18) should be consulted to plan effective
sampling programs for either simple or complex sites.
The method of sample collection is site-specific. For
example, drill rigs or hand augers can be used to collect
samples, depending on the depth of the sample required and
the soil characteristics. If the target contaminants are volatile
and the samples are composited, care should be taken to
minimize the loss of volatile compounds. Compositing
samples on ice is a good method for minimizing the loss of
volatile compounds. Compositing is usually appropriate for
soils containing nonvolatile constituents.
4.4.2 Waste Analysis
Section 2.2.3 detailed the physical tests that are useful in
characterizing the soil matrix at the site during the
prescreening step. The key for successful soil washing
treatability studies is to properly select the soil feedstock
(e.g., sand, loam, clay, etc.) based on the initial prescreening
and additional soil characterizations. Other important soil
characteristics include the pH and moisture content of the
soil. The pH is important in determining the compatibility of
soil washing fluids. The speciation of metal compounds
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may also be affected by soil pH. The soil moisture content is
an important consideration for materials handling.
Standard analyses for contaminants at Superfund sites should
identify the contaminants of concern. It is important to
determine the solubility and volatility of organics.
Contaminant solubility will give an indication of whether
washing solution additives will be required. Volatility will be
an important consideration for materials handling. If high
concentrations of volatiles are present, pretreatment (e.g.,
using soil vapor extraction) or collection and treatment of air
emissions may be required. Metal speciation will be an
important consideration in determining metal solubility.
The spatial distribution and variations in the concentrations of
contaminants will be important for the design of treatability
studies. Complex mixtures of contaminants may be difficult
to treat economically. A number of wash stages and
additives may be required to successfully remove many
contaminants. The cost of such a system may be prohibitive.
Frequent changes in contaminant composition can cause
dramatic changes in removal efficiencies.
4.4.3 Process Control Sampling and
Analysis
This is not applicable to remedy screening and remedy
selection.
4.4.4 Treatment Product Sampling and
Analysis
Soil washing is not a stand-alone process (see Section 2.1.
1). It generates residuals that must be treated further and
disposed of properly. Because the nature of soil washing
equipment and procedures varies greatly between
manufacturers, remedy design testing is necessary to
evaluate the type, quantity, and properties of residuals.
Analyze the washed soil and each of the various
wastestreams (wash water, fine sediment, etc.) for the
contaminants identified in the original soil analyses. In many
cases, indicator contaminants, which are representative of a
larger group of contaminants, can be analyzed in place of a
full scan. Caution must be exercised in using indicator
contaminants since soil washing efficiencies can vary from
one contaminant to another. The process efficiency may be
either understated or overstated when analyzing for indicator
compounds.
If several soil washing studies are run to test the effects of
operating parameters on washing efficiency (i.e., the addition
of surfactants, chelating agents, etc.), samples should be
taken of each test before and after soil washing. Typically,
these tests are run in triplicate.
4.4.5 Sampling and Analysis Plan (SAP)
and Quality Assurance Project
Plan (QAPjP)
A SAP is required for all field activities conducted during the
RI/FS. The SAP consists of the Field Sampling Plan and the
QAFjP. This section of the Work Plan describes how the
RI/FS SAP is modified to address field sampling, waste
characterization, and sampling activities supporting
treatability studies. It describes the samples to be collected
and specifies the level of QA/QC required. See Section 5 for
additional information on the SAP.
4.5 DATA ANALYSIS AND
INTERPRETATION
The Work Plan should discuss the techniques to be used in
analyzing and interpreting the data. The objective of data
analysis and interpretation is to provide sufficient information
to the RPM and EPA management to assess the feasibility
of soil washing as an alternative technology. After remedy
selection testing is complete, the decision must be made
whether to proceed to the remedy design testing tier, to a
full-scale soil washing remediation, or to rule out soil washing
as an alternative. The data analysis and interpretation are a
critical part of the remedy selection process.
Methods commonly used to analyze and interpret data
generated in the soil washing process, such as particle size
distribution of the soil, chemical analysis of the contaminants
present, and test process variables, apply to all three tiers of
the soil washing treatability study.
The particle size distribution of the soil is a standard physical
characterization technique. Recent studies indicate that
contamination is often distributed as a function of soil particle
size. Treatment efficiency is a function of particle size as
well. Three particle size ranges have been frequently studied:
>2 mm, 0.25 to 2 mm, and O.25 mm. These fractions are
obtained from U.S. Standard Sieve Series #10 and #60.
Figure 4-1 shows the applicable particle size ranges plotted
against the sieve throughput percent by weight.02°
Range I consists of coarse soils. Soils in Range I are
economically washed with simple particle size separation
when contaminants are concentrated in the smaller particles.
When fractionation does not occur, as is the case
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Sand
Average , Large
Gravel
Average , Large
Soil Washing
(Range
Soil Wash with
Specific Washing Fluid
(Range II)
Economic Wash
with Simple Particle
Size Separation
(Range I)
0.001 0.002
0.006 0.01 0.02 0.063 0.1 0.2 0.6 1 2 6
Diameter of Particle in Millimeters
FIGURE 4-1. Soil washing applicable particle size range.
20
60 100
with lead, there is no improvement in the economics of
separation when the soil is in Range I.
Soils in the area to the right of Range I are primarily stone
and large gravel. Particle size separation is normally not
feasible for these materials due to their, large size. However,
soluble contaminants may be removed from such soils in the
wash water.
Most contaminated soils lie in Range II. The types of
contaminants present govern, the composition of wash fluids
and affect the overall process efficiency. Process efficiency
is also affected by soil particle distribution patterns and the
250.
fractionation of contaminants in fine particles. Both particle
size separation and contaminant solubilization can be
important for cost-effective treatment of soils in Range II.
Soils in Range III consist primarily of fine sand, silt, and clay.
Frequently, such soils have high humic content and organics
may be strongly adsorbed. Particle size separation may be
effective in concentrating contaminants adsorbed to particles
in this size range into a smaller volume.0 2)
Figure 4-2 is a hypothetical contaminant distribution
histogram for soil. The histogram represents results of
chemical analyses on contaminated bulk and fractionated soil
0.45
2.0mm
Soil Size Fraction
FIGURE 4-2. Hypothetical contaminant distribution by soil
fraction before and after treatment.
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before and after two treatments. The soil was treated with
water at ambient temperature and hot water. The data show
that contaminant is concentrated in the <2 mm soil fractions.
Water at ambient temperature was able to reduce the
contamination in the >2 mm fraction to 10 parts per million
(ppm) (a contaminant reduction of approximately 94
percent). Hot water improved the performance by reducing
the contaminant concentration to 0.45 ppm in the >2 min
fraction (a contaminant reduction of over 99 percent).
Contaminant concentrations in the other fractions (0.25 to 2
mm and <0.25 nun) were not appreciably affected by soil
washing.
Figure 4-3 shows a plot of agitated contact time against
contaminant removal efficiency and final contaminant
concentration in the >2 mm soil fraction. The contaminant
concentration in each soil fraction would normally be plotted
at each time point. In this graph, the initial concentration is
500 ppm and the contaminant cleanup goal is 200 ppm. It is
apparent that the agitated contact time must be a minimum
of 14 minutes to provide contaminant removal efficiencies
that meet the cleanup goals. The effectiveness of treatment
can be expressed as a percent reduction of contaminant. In
this case, there is a 60 percent reduction in contaminant
concentration in the >2 mm soil fraction at 14 minutes. The
figure also demonstrates that, for the soil studied, mixing
times of greater than 14 to 15 minutes result in diminishing
returns. The shape of this curve will be different for each
soil.
An objective of the remedy selection soil washing treatability
testing is to determine how the treatment is affected by the
process design variables. These variables may include
soil-to-wash water ratio, type of mechanical agitation used,
agitated contact time, rinse-water-to-wash water volume
ratio, wash water temperature, system pH, and wash water
additives. Often, two or more of these variables may affect
the results. Statistical analysis of the data can be performed
using standard techniques to differentiate sources of change
and interactions between these sources. For a detailed
discussion of the ANOV A techniques, refer to the document
entitled Statistical Analysis of Groundwater Data at RCRA
Facilities (Interim Final)(20) and Brookes, et al.(5)
4.6 REPORTS
The last step of the treatability study is reporting the results.
The Work Plan discusses the organization and content of
interim and final reports. Complete, accurate reporting is
critical because decisions about implementability will be
partly based on the outcome of the study. The RPM may not
require formal reports at each soil washing study tier. Interim
reports should be prepared after each tier. Project briefings
should be made to interested parties to determine the need
for and scope of the next tier of testing. To facilitate the
reporting of results and comparisons between treatment
alternatives, a sug-
| SO
Contaminant Claanup
Goal>200ppm
_L
J_
10 16 2C 25
Agitated Contact Tint (minutes)
30
FIGURE 4-3. Plot of agitated contact time versus contaminant removal efficiency
and final contaminant concentration in the >2 mm soil fraction.
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TASK
Tatkl
Work Plan Preparation
Task 2
SAP, HSP, & CRP Preparation
TaskS
Treatability Study Execution
Task 4
Data Analysis & Interpretation
TaskS
Report Preparation
Task 6
Residuals Management
Span,
Weeks
4
6
12
2
12
12
Week* from Project Start
T|7
3
M-l
^
4
M
.|.
-2
7
d
%
7 I8
9|lo|ll|l2
M-3 M-4
'-7
X *1
13
-5
r
14(15(16
M
^
17J18
19
20
-6 M-7
/
/
\«
H
-8
21(22(23(24
M-9
w
^f
(^
JJ
25 26|27|28
M-12 M
29)30
13 M
15
M-10 M-ll M-14 M-16
1 1
- Administrative approval, document review, or sample turnaround
M-l Submit Work Plan Wk2
M-2 Receive Work Plan Approval Wk4
M-3 Submit SAP, HSP, CRP Wk8
M-4 Receive SAP, HSP Approvals Wk10
M-5 Collect Sample Wk 12
M-6 Receive Sample Characterization Results Wk 16
M-7 Collect Treatability Study Samples Wk18
M-8 Collect Project Residual Samples Wk 18
M-9. Receive Treatability Study Analytical Results Wk 22
M-10 Receive Project Residual Analytical Results Wk22
M-11 Submit Waste Disposal Approval Form Wk 24
M-12 Submit Draft Report Wk26
M-13 Receive Review Comments Wk28
M-14 Receive Waste Disposal Approval Wk 28
M-15 Submit Final Report; Conduct Briefing Wk30
M-16 Ship Wastes to TSDF Wk30
FIGURE 4-4. Example Droiect schedule for a treatabilitv study.
gested table of contents is presented in the generic guide.(15)
At the completion of the study, a formal report is always
required.
OERR requires that a copy of all treatability study reports be
submitted to the Agency's Superfund Treatability DataBase
repository. One copy of each treatability study report must
be sent to:
U.S. Environmental Protection Agency
Superfund Treatability Data Base
ORD/RREL
26 West Martin Luther King Dr.
Cincinnati, Ohio 45268
4.7 SCHEDULE
The Work Plan includes a schedule for completing the
treatability study. The schedule gives the anticipated starting
date and ending date for each of the tasks described in the
Work Plan and shows how the various tasks interface.
The time span for each task accounts for the time required
to obtain the Work Plan, subcontractor, and other approvals
(e.g., disposal approval from a commercial TSDF); sample
curing time, if necessary; analytical turnaround time; and
review and comment period for reports and other project
deliverables. Some slack time also should be built into the
schedule to accommodate unexpected delays (e.g., bad
weather, equipment downtime) without affecting the project
completion date.
The schedule is usually displayed in the form of a bar chart
(Figure 4-4). If the study involves multiple tiers of testing, all
tiers should be shown on one schedule. Careful planning
before the start of the tests is essential. Depending on the
review and approval process, planning can take up to several
months. Barring any difficulties, such as acquiring sampling
equipment and site access, the field work phase can
generally be accomplished in two weeks. Setup of the
laboratory and procurement of necessary equipment and lab
supplies for treatability studies may take a month. Analytical
results can be available in less than 30 days, depending on
how rapidly laboratory results can be pro-
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LAB TECHNICIANS
Execute Treatability
Studies
Execute sample collection
and analysis
CONTRACT WORK
ASSIGNMENT MANAGER
Report to EPA Remedial
Project Manager
Supervise overall project
GEOLOGIST
> Oversee Treatability Study
execution
> Oversee sample collection
> Prepare applicable sections
of Report and Work Plan
QA MANAGER
> Oversee Quality
Assurance Program
> Prepare applicable
sections of Report and
Work Plan
CHEMIST
Oversee sample collection
procedures and analysis
Prepare applicable section
of Report and Work Plan
FIGURE 4-5. Organization chart.
vided. Shorter analytical turnaround time can be requested
but this will normally double the costs. Compounds such as
pesticides and PCBs may require longer turnaround times
due to the extractions and analyses involved. Depending on
the objectives., the duration of treatability tests may be
longer.
Responsibility for various aspects of the project is typically
shown in an organizational chart such as the one in Figure
4.5
4.9 BUDGET
Interpretation of the results and final report writing may take
1 to 2 months, but this is highly dependent on the review-
process. Remedy screening tests typically take from a few-
hours to several days. It is not unusual for the remedy
selection soil washing treatability test to be a 2 to 3 month
project.
4.8 MANAGEMENT AND STAFFING
The Work Plan discusses the management and staffing of
the remedy selection treatability study. The Work Plan
specifically identifies the personnel responsible for executing
the treatability study by name and qualifacations. Generally,
the following expertise is needed for the successful
completion of the treatability study:
Project Manager (Work Assignment Manager)
Chemist
Geologist
Lab Technician
The Work Plan discusses the budget for completion of the
remedy selection treatability study. Testing costs for remedy-
selection depend on a variety of factors. Table 4-2 provides
a list of potential major cost estimate components this tier.
For most tests, the largest single expense is the
analytical program.
TABLE 4-2.Major Cost Elements Associated with
Remedy Selection Soil Washing Studies
Cost Element
Initial Data Review
Work Plan Preparation
Field Sample Collection
Field Sample Chemical Analysis
Laboratory Setup/Materials
Treatability Test Chemical Analysis
Data Presentation/Report
Cost Range
(1,000s of dollars)
1 -10
1 -5
1 -10
5-25
5-25
5-20
2-5
TOTAL COST RANGE
20-100
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Sites where the soil types, contaminant types, and
contaminant concentration vary widely will usually require
more samples than sites where the soil and contamination is
more homogeneous. It is not unusual for the sampling,
analysis, and QA activities to represent 50 percent of the
total testing cost. In general, the costs for analyzing organics
are more expensive than for metals. Actual costs will vary
according to individual laboratories, required turnaround
times, volume discounts, and any customized testing.
Sampling costs will be influenced by the contaminant types
and depth of contamination found in the sod. The health and
safety considerations during sampling activities are more
extensive when certain contaminants (e.g., volatile organics)
are present in the soil. Level B personal protective equipment
(PPE) rather than Level D PPE can increase the cost
component an order of magnitude. Sampling equipment for
surface samples is much less complicated than equipment
used for depth samples. Depending on the number of
samples and tests specified, residuals management (e.g.,
contaminated soil fraction and wash waters) will require
proper treatment and/or disposal. Treatment and disposal of
the residuals as hazardous wastes increases costs
significantly.
Other factors to consider include report preparation and the
availability of vital equipment and laboratory supplies.
Generally, an initial draft of the report undergoes internal
review prior to the final draft. Depending on the process,
final report preparation can be time consuming as well as
costly. Procurement of testing equipment (e.g., reciprocating
shaker table) and laboratory supplies (e.g., reagents and
glassware) will also increase the costs.
Typical costs for remedy selection tests are estimated to be
from $20,000 to $100,000. Remedy screening, with its
associated lack of replication and detailed testing, ranges
from 25 to 50 percent of these costs. These estimates are
highly dependent on the factors discussed above. Not
included in these costs are the costs of governmental
procurement procedures, including soliciting for bids,
awarding contracts, etc.
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SECTION 5
SAMPLING AND ANALYSIS PLAN
The Sampling and Analysis Plan (SAP) consists of two
parts-the Field Sampling Plan (FSP) and the Quality
Assurance Project Plan (QAPjP). The purpose of this
section is to identify the contents and aid in the preparation
of these plans. The RI/FS requires a SAP for all field
activities. The SAP ensures that samples obtained for
characterization and testing are representative and that the
quality of the analytical data generated is known and
appropriate. The SAP addresses field sampling, waste
characterization, and sampling and analysis of the treated
wastes and residuals from the testing apparatus or treatment
unit. The SAP is usually prepared after Work Plan approval.
5.1 FIELD SAMPLING PLAN
The FSP component of the SAP describes the sampling
objectives; the type, location and number of samples to be
collected; the sample numbering system; the equipment and
procedures for collecting the samples; the sample
chain-of-custody procedures; and the required packaging,
labeling, and shipping procedures.
The sampling objectives must be consistent with the
treatabiliry test objectives. The primary objective of remedy
selection treatability studies is to evaluate the extent to which
specific chemicals are removed from the soil. The primary
sampling objectives include:
Acquisition of samples representative of conditions
typical of the entire site or defined areas within the site.
Because a mass balance is required for this evaluation.
statistically designed field sampling plans may be
required. However, professional judgment regarding the
sampling locations may be exercised to select sampling
sites that are typical of the area (pit. lagoon, etc.) or
appear above the average concentration of contaminants
in the area being considered for the treatability test.
Selection may be difficult because reliable site
characterization data may not be available early in the
remedial investigation.
Acquisition of sufficient sample volumes necessary for
testing, analysis, and quality assurance and quality
control (QA/QC).
From these two primary objectives, more specific objectives
are developed. When developing the more detailed
objectives, consider the following types of questions:
Will samples be composited to provide more
representative samples for the treatability test, or will the
potential loss of target volatile organic compounds
prohibit this sample collection technique?
Is there adequate data to determine sampling locations
indicative of the more contaminated areas of the site?
Contaminants may be widespread or isolated in small
areas (hot spots). Contaminants may be mixed with other
contaminants in one location and appear alone in others.
Concentration profiles may vary significantly with depth.
Are the soils homogeneous or heterogeneous? Soil types
can vary across a site and will vary with depth. Changes
in soil composition can reduce the effectiveness of soil
washing.
Is sampling of a "worst-case" scenario warranted? The
decision on whether to perform remedy selection testing
on specific areas or composite samples is difficult and
must be made on a site-by-site basis. Hot spots and
areas with soils that may be difficult to treat should be
factored into the test plan if they represent a significant
portion of the waste site.
After identifying the sampling objectives, an appropriate
sampling strategy is described. Specific items that should be
briefly discussed in the FSP and QAPjP are listed in Table
5-1.
Table 5-1 presents the suggested organization of the Sam-
pling and Analysis Plan.
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TABLE 5-1. Suggested Organization of Sampling and
Analysis Plan
Field Sampling Plan
1 . Site Background
2. Sampling Objectives
3. Sample Location and Frequency
- Selection
- Media Type
- Sampling Strategy
- Location Map
4. Sample Designation
- Recording Procedures
5. Sample Equipment and Procedures
- Equipment
- Calibration
-Sampling Procedures
6. Sample Handling and Analysis
- Preservation and Holding Times
-Chain-of-Custody
-Transportation
Quality Assurance Project Plan
1. Project Description
-Test Goals
- Critical Variables
-Test Matrix
2. Project Organization and Responsibilities
3. QA Objectives
- Precision, Accuracy, Completeness
- Representativeness and Comparability
- Method Detection Limits
4. Sampling Procedures
5. Sample Custody
6. Calibration Procedures and Frequency
7. Analytical Procedures
8. Data Reduction, Validation, and Reporting
9. Internal QC Checks
10. Performance and System Audits
11. Preventive Maintenance
12. Calculation of Data Quality Indicators
13. Corrective Action
14. QC Reports to Management
15. References
16. Other Items
5.2 QUALITY ASSURANCE PROJECT
PLAN
5.2.1 Experimental Design
Section 1 of the QAPjP must include an experimental project
description that clearly defines the experimental design, the
experimental sequence of events, each type of critical
measurement to be made, each type of matrix (experimental
setup) to be sampled, and each type of system to be
monitored. This section may reference Section 4 of the Work
Plan. All details of the experimental design not finalized in
the Work Plan should be defined in this section.
Items to be included, but not limited to, are:
Number of samples (area) to be studied
Identification of treatment conditions (variables) to be
studied for each sample (i.e., wash time, wash water-
to-soil ratio, rinse water-to-wash water ratio, and
additives to be evaluated)
Soil size fractions
Target compounds for each sample
Number of replicates per treatment condition
The Project Description clearly defines and distinguishes the
critical measurements and observations made and system
conditions (e.g., process controls, operating parameters, etc.)
routinely monitored. Critical measurements are those
measurements, data gathering, or data generating activities
that directly affect the technical objectives of a project. At a
minimum, the determination of the target compound
(identified above) in the untreated and treated soil samples
and the particle size distribution of the untreated soil will be
critical measurements.
The purpose of the remedy selection treatability study is to
determine whether soil washing can meet cleanup goals and
provide information to support the detailed analysis of
alternatives (i.e., seven of the nine evaluation criteria). An
example of a criterion for this determination is a removal of
approximately 90 percent of the contaminants. The exact
removal efficiency specified as the goal for the remedy
selection test is site specific.
5.2.2 Quality Assurance Objectives
Section 2 lists the QA objectives for each critical
measurement and sample matrix defined in Section 1. These
objectives are presented in terms of the six data quality
indicators: precision, accuracy, completeness,
representativeness, comparability, and, where applicable,
method detection limit.
5.2.3 Sampling Procedures
The procedure used to obtain field samples for the treatability
study is described in the FSP. They need not be
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repeated in this section, but should be incorporated by
reference.
Section 3 of the QAPjP contains a description of a credible
plan for subsampling the material delivered to the laboratory
or the treatability study. The methods for aliquoting the
residual material in each size fraction for different analytical
methods must be described.
determine if the analytical method performance is consistent
(relatively accurate). The method blank will show if
laboratory contamination has had an impact on the analytical
results.
Selection of appropriate surrogate compounds will depend on
the target compounds identified in the soil and the analytical
methods selected for the analysis.
5.2.4 Analytical Procedures and
Calibration
Section 4 describes or references appropriate analytical
methods and standard operating procedures for the analytical
method for each critical measurement made. In addition, the
calibration procedures and frequency of calibration are
discussed or referenced for each analytical system,
instrument, device, or technique for each critical
measurement.
The methods for analyzing the treatability study samples are
the same as those for chemical characterization of field
samples. Preference is given to methods in "Test Methods
for Evaluating Solid Waste, SW-846, 3rd. Ed., November
1986.(23) Other standard methods may be used, as
appropriate.(17) Methods other than gas
chromatography/mass spectra (GC/MS) techniques are
recommended to conserve costs when possible.
The purpose of the remedy selection treatability study is to
determine whether soil washing can meet cleanup goals and
provide information to support the detailed analysis of
alternatives (i.e., seven of the nine evaluation criteria). An
example of a criterion for this determination is a removal of
approximately 90 percent of contaminants. The exact
removal efficiency specified as the goal for the remedy
selection test is site-specific. The suggested QC approach
will consist of:
Triplicate samples of both reactor and controls
The analysis of surrogate spike compounds
The extraction and analysis of method blanks
The analysis of a matrix spike in approximately 10
percent of the samples.
The analysis of triplicate samples provides for the overall
precision measurements that are necessary to determine
whether the difference is significant at the chosen
confidence level. The analysis of the surrogate spike will
5.2.5 Data Reduction, Validation and
Reporting
Section 5 includes, for each critical measurement and each
sample matrix, a specific presentation of the following items:
The data reduction planned for the collected data
All equations used to calculate the final resultant value(s)
from the raw critical measurement data, all unit
conversions required and definitions of all terms, as well
as the procedures for correcting analytical recovery
The procedures used to validate data during data
collection, transfer, storage, recovery, processing, and
reporting steps
The methods used to identify and treat outliers (i.e., data
that fall outside the specified QA objective windows for
method precision and accuracy)
The data reporting scheme, including the flow from raw
data through transfer, storage, recovery, processing, and
validation; a flowchart is usually needed
Identification of the specific individuals responsible for
data handling at each step in the reporting scheme.
5.2.6 Internal Quality Control Checks
Section 6 describes and references each specific internal QC
method followed, and indicates the frequency of use. (The
term internal refers to both soil washing tests and laboratory
activities, and applies to all organizations and individuals
involved in the project.) Examples of the types of QC checks
include the following:
Split samples
Replicate samples
Replicate check standards
Matrix-spiked samples
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Matrix-spiked replicates
Laboratory pure water spikes (e.g., QC check samples)
Surrogate spike compounds
Internal standards
Blanks (method, reagent, and/or instrument)
Control charts (e.g., for calibration acceptance limits)
Calibration standards and devices (traceable)
Reagent checks (for all sample preparation and analysis
methods involving the use of laboratory reagents)
In-house proficiency testing program to determine
analyst's capabilities (including documented procedures).
5.2.7 Performance and Systems Audits
Section 7 describes the internal performance evaluation and
technical system audits planned to monitor the capability and
performance of the systems for obtaining critical
measurement data.
At a minimum, a person independent of the analysis submits
a quality control sample for all or some of the target
compounds to the analytical laboratory. The results of the
extraction and analysis document the capabilities of the
personnel with the prescribed procedures.
5.2.8 Calculation of Data Quality
Indicators
Section 8 describes the specific procedures that assess, on a
routine basis, the precision, accuracy, completeness, and
method detection limit (MDL) characteristic of each critical
measurement for each sample matrix. Specifically, the
following items are included:
A brief description of each test procedure for each data
quality indicator, measurement, and sample type
Identification of the specific QC data used in each test
procedure
A brief discussion defining the statistical or mathe-
matical methods used
Specific equations used to calculate each data quality-
indicator, including definitions of reporting units of each
term in the equations
A statement of the frequency of each type of test.
5.2.9 Corrective Action
Section 9 describes the criteria and procedures by which
initial corrective actions are implemented. These descriptions
include the following elements:
The predetermined limits for data acceptability; data
outside these limits require corrective action
The procedures for corrective action, from initial
recognition of the condition requiring corrective action,
through reporting of the condition, approval of the
appropriate corrective action to be taken,
implementation, and reporting of the results
Identification of the individuals responsible for initiating,
approving, implementing, and reporting the effectiveness
of corrective actions.
5.2.10 Quality Control Reports
Section 10 describes the QA/QC information that will be
included in the final project report. As a minimum, reports
include:
Changes to the QA Project Plan, if any
Limitations or constraints on the applicability of the data,
if any
The status of QA/QC programs, accomplishments and
corrective actions
Results of technical systems and performance evaluation
QC audits
Assessments of data quality in terms of precision,
accuracy, completeness, method detection limit,
representativeness, and comparability.
The final report contains all the QA/QC information to
support the credibility of the data and the validity of the
conclusions. This information may be presented in an
appendix to the report. Additional information on data quality
objectives01\ quality assurance programs(13), and preparation
of QAPjPs(19) is available in EPA guidance documents.
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SECTION 6
TREATABILITY DATA INTERPRETATION
Proper evaluation of the potential of soil washing for
remediating a site must compare the test results (described
in Section 4.5) to the test objectives (described in Section
4.1) for each tier. The evaluation is interpreted in relation to
seven of the nine RI/FS evaluation criteria, as appropriate.
The remedy screening tier establishes the general
applicability of the technology. The remedy design tier
provides information in support of the evaluation criteria. The
test objectives are based on established cleanup goals or
other performance-based specifications (such as waste
volume reduction). Soil washing testing must consider the
technology as part of a treatment train.
Section 4.6 of this guide discusses the need for the
preparation of interim and final reports and provides a
suggested format. In addition to the raw and summary data
for the treatability study and associated QC, the treatability
report should describe what the results mean and how to use
them in the feasibility study in screening/selecting
alternatives. The report must evaluate the performance of
the technology and give an estimate of the costs of further
treatability studies and final remediation with the technology.
6.1 TECHNOLOGY EVALUATION
Remedy screening treatability studies typically consist of
simple jar tests. The contaminant concentration in the soil
before washing is compared to the contaminant
concentration in the coarse soil fraction after washing. A
reduction of approximately 50 percent of the soil
contaminants during the test indicates additional treatability
studies are warranted. Contaminant concentrations can also
be determined for wash water and fine soil fractions. These
additional analyses add to the cost of the treatability test and
may not be needed. Before and after concentrations can
normally be based on duplicate samples at each time period.
The mean values are compared to assess the success of the
study. A number of statistical texts are available if more
information is needed.(4)(7)
Jar tests can frequently be skipped when information about
the soil type and contaminant solubilities is sufficient to
decide whether remedy selection studies will be useful. An
example of a prescreening evaluation and decision to bypass
ajar test is provided in Example 3.
Example 3
A site in New Jersey has been used for the manufacture and storage of arsenic-containing pesticides. Soils
at the site are contaminated with arsenic at levels ranging from 10 to 1,500 mg/ kg. The arsenic
contamination is limited to the top 3 feet of soil. Sieve testing has shown that the upper 3 feet of soil contains
75 percent coarse sand and gravel (75 percent >2 mm diameter particles) by weight. Risk assessment
studies conducted during the Rl suggest that a cleanup goal of 100 mg/kg arsenic in onsite soils would be
acceptable.
Previous studies indicated that many contaminants tend to be adsorbed on fine soil particles. Given this
scenario, one can predict that there is at least a moderate chance that soil washing will be effective. It is
entirely possible that the process will be able to reduce the arsenic content in 75 percent of the soil to 100
mg/kg or less. In this case, screening tests may be skipped in favor of conducting remedy selection tests
that would determine optimal soil washing conditions (pH, additives, temperature, mixing/contact time,
wastewater treatment) and performance at bench scale.
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Sections 4.1 and 4.2 of this guide discuss the goals and
design of remedy selection treatability studies, respectively.
Typically, soil contaminant concentrations before soil
washing and contaminant concentrations in the coarse
fraction after soil washing are measured in triplicate. A
reduction of approximately 90 percent in the mean
concentration indicates soil washing is potentially useful in
site remediation. A number of other factors must be
evaluated before deciding to proceed to remedy design
studies.
The final concentrations of contaminants in the recovered
(clean) soil fraction, in the fine soil fraction and wastewater
treatment sludge, and in the wash water are important to
evaluating the feasibility of soil washing. The selection of
technologies to treat the fine soil and wash water waste-
streams depends on the types and concentrations of
contaminants present. The volume reduction achieved is also
important to the selection of soil washing as a potential
remediation technology.
In scaling the cost and performance estimates from remedy
selection testing to remedy design testing or a full-scale soil
washing system, the factors for consideration are:
Performance capabilities of the soil washing process.
including design parameters
Contaminants and contaminant concentrations in the
coarse soil fraction
Contaminants and contaminant concentrations in the
used wash water and in the fine soils and wastewater
treatment sludges
Risk analysis evaluation for worker and community
protection
Quantity of large rocks, debris, arid other screenable
material
The design parameters for the soil washing process include
soil throughput, in dry tons per hour, and optimum wash
water usage in gallons per dry ton of soil. The dosage of
additives, if used, mixed with wash water is also important
for cost and performance estimates.
It is important to estimate the volume and physical and
chemical characteristics of each soil fraction. Estimates of
the volume of and contaminant concentrations in the fine soil
fraction are needed to design treatment systems and estimate
disposal costs. Recycled water can be used to evaluate the
cost of filtration and other dewatering equipment. The ability
to remove contaminants from spent wash water and recycle
the water through the system is an important cost
consideration.
Wash water is treated for recycle in the washing process.
Treatment includes separation of fine soil particles. Other
treatment steps may be necessary to remove organics,
inorganics, and additive chemicals. Scale-up design requires
estimates of wash water volume and quality.
Contamination in excavated soil can pose safety concerns for
workers and the community. Worker protection may be
required during soil excavation. The need for such protection
is a site-specific decision. Health and safety plans should be
prepared and risk analysis conducted for the site.
The quantity of large rocks, debris, and other screenable
material that must be removed is an important measurement.
While this is not a "laboratory" measurement, it is important
to determine which treatment method is most suitable for
preparing the bulk soil for entry into the soil washing process
(i.e., screening to remove large rocks, stumps, debris, and
crushing of oversize rocks, etc.).
6.2 ESTIMATION OF COSTS
Accurate cost estimates for remedy design treatability
studies and full-scale remediation are crucial to the feasibility
study process. Comparisons of various technologies must be
based on the most complete and accurate estimates
available, Remedy screening treatability studies cannot
provide this type of information. Remedy selection treatability
studies can provide relatively accurate cost estimates for
remedy design studies. Preliminary cost estimates for
full-scale remediation may be made from remedy selection
data. Such estimates may be good enough for comparisons
to other technologies at the same tier of testing. On this basis,
the estimates can form the basis of the ROD. Remedy
design studies may be necessary to provide a more accurate
estimate of the eventual cost of full-scale soil washing
remediation. This is especially true since soil washing will
form only one component of a treatment train. The treatment
costs for sludge and wastewater from the soil washing
process must also be evaluated.
6.2.1 Soil Washing Remedy Design
Cost Estimates
If the results of remedy selection treatability testing indicate
that soil washing can be effective, consideration may be
given to remedy design testing. Remedy design tests
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yield more accurate estimates of full-scale performance and
costs. This discussion provides general guidance on the cost
estimating and scheduling of remedy design soil washing
demonstrations.
Few remedy design soil washing demonstrations have been
done in the United States. A solid data base of cost
estimating and scheduling information does not yet exist. The
information in this section is largely derived from EPA RREL
experience with its portable soil washing unit, informational
estimates by the few manufacturers offering remedy design
soil washing equipment and recent experience with the EPA
SITE Program. A summary of the performance data and a
review of the technology are presented in a Soil Washing
Engineering Bulletin.112)
Remedy Design Soil Washing Equipment Availability:
As of Fall 1989 only three sources of a portable remedy
design soil washing units were identified:
BioTrol, Inc.. Chaska, Minnesota
Ecova Corp.. Redmond, Washington
EPA RREL Laboratory, Edison, New Jersey
Mitarri, Inc., Golden, Colorado, reportedly plans to develop a
remedy design unit. For the SITE Program, a remedy design
BioTrol soil washing unit was recently demonstrated and
evaluated in New Brighton, Minnesota.
Remedy Design Testing Cost: Many of the cost consid-
erations in a remedy design soil washing test are similar to
those of the remedy selection. Table 6-1 lists potential major
cost estimate components in a remedy design soil washing
field test. Some of the items in this table also pertain to
remedy selection testing. The cost considerations include
planning, treatment, laboratory testing, and report
preparation. Substantial planning is necessary to assure that
tests meet desired objectives. Additional insurance and
permits may be required. As with remedy selection
demonstrations, the analytical program can be the largest
cost component. It is not unusual for the sampling, analysis,
and QA activities to represent 50 to 60 percent of the total
remedy design testing cost. Remedy design testing requires
personnel safety protection for soil excavation and handling.
Working under Level A or B protection can easily triple labor
costs. The treatment and disposal of contaminated residuals
(soil, sludge, water) can be a major expense. For these
reasons, remedy design testing costs are highly variable
depending on a variety of factors discussed above.
The cost of remedy design testing is highly site-specific and
dependent upon the test objective. As a rough estimate,
remedy design field tests could be expected to range from as
low as $100,000 up to $500,000 (1989 costs) or more.
TABLE 6-1. Potential Major Cost Estimate
Components in a Remedy Design Soil
Washing Field Test
1. Planning- substantial advanced planning is usually
necessary to assure that the demonstration
proceeds smoothly and meets the desired
objectives, including any necessary insurance,
permits, etc.
2. Excavation, transport (if needed), and storage (if
needed) of the soil to be treated during the
demonstration.
3. Design and construction (as required) of temporary
onsite support facilities, including water supply,
power, wastewater discharge, storage of additive
chemicals, and personnel facilities (office, storage,
field testing space, restrooms, showers, etc.). A
detailed sampling analysis and QAPjP is
necessary.
4. Analytical support, e.g., local laboratory, mobile
field laboratory, etc. A detailed sampling analysis
and QAPjP is necessary.
5. Treatment and/or disposal of contaminated
residuals, e.g., the contaminated soil fraction,
sludges, screened-out debris, etc.
6. Supply of chemicals, water, power, spare parts,
personnel protection equipment, etc.
7. Lease or rental of the remedy design unit and
auxiliary equipment including transport to the site.
8. Provision for operating, maintenance, and
analytical labor. Usually, personnel are trained for
handling hazardous materials safely in addition to
their other job-specific qualifications.
9. Implementation of the remedy design
demonstration in accordance with the detailed
Work Plan.
10. Decontamination, demobilization, and return
transport of remedy design soil washing unit and
auxiliary equipment.
11. Return of operating site to pre-agreed condition.
12. Laboratory testing.
13. Report preparation.
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6.2.2 Full-Scale Soil Washing Cost
Estimates
There are no full-scale soil washing operations in use at
Superfund sites identified at the present time. A limited
number of firms (e.g., Ecova, BioTrol) are marketing their
soil washing processes. In Europe, full-scale soil washing
facilities are operating in Germany and the Netherlands. Cost
information is largely in technical articles written by
representatives of the German firm, Harbauer GmbH. The
capital cost of the Harbauer facility is reported to be
approximately $6 million (1986 dollars) for a 15 to 20 ton/hr
facility. The reported operation and maintenance (O&M)
costs for processing alone at the Harbauer Site are $150 per
ton of soil, including the cost of water treatment, but not
including sludge disposal. If sludge weight was assumed to
be 20 percent of the incoming soil weight, and sludge disposal
cost assumed to be $250 per ton, the estimated cost per ton
of treated soil would be about $200 including sludge disposal.
Other European soil washing operations that are less
complex than the Harbauer GmbH Berlin operation report
soil washing processing costs of about $80 to $120 per metric
ton or $73 to $110 per ton. Their costs are generally-
presented in mid-1980's dollars and details of how these
costs were determined are lacking. Table 6-2 lists the major
cost components for a hypothetical full-scale soil washing
operation.
TABLE 6-2. Major Cost Estimate Components in a
Full-Scale Soil Washing Operation3
1. Soil excavation.
2. Transport of excavated soil to the processing unit.
3. Temporary stockpiling of excavated soil.
4. Prevention of contaminant releases to the
environment during Steps 1 through 3 above due to
rain, wind, volatilization, carelessness, etc.
5. Bulk soil pretreatment steps such as screening,
crushing, and physicat/chemical characterization.
6. Management of the screened-out rocks, roots,
debris, etc.
7. Wash water supply facilities, e.g., storage tanks,
pumps, piping, controls, etc.
8. Additive (if any) supply facilities, e.g., storage
tanks, pumps, piping, controls, etc.
9. The soil washing process unit, which may consist
of a series of mixers, washers, screens,
conveyors, cyclones, and other units. It is
assumed that generally this cost will be obtained
from the manufacturer.
10. Temporary stockpiling, transport, and deposition of
the adequately clean, washed soil product fraction.
11. The dirty wash water treatment process, which is
usually a treatment train that may include
clarifiers, chemical reactors, filters, carbon
contactors, dewatering presses, and tanks, etc.
12. Recycle or disposal of the treated wastewater
fraction.
13. Further treatment and disposal of the dirty soil
fraction.
14. Further treatment and disposal of the water
treatment sludge.
15. Permitting and legal services.
16. Engineering design.
17. Service during construction.
18. Contingencies.
a. Note: where applicable, the engineer performing the cost
estimate will usually break down the cost estimate
components listed above into:
(1) construction (e.g., roads, foundations, buildings, etc.)
(2) process equipment (e.g., mixers, tanks, screens, pumps,
clarifiers, etc,)
(3) material handling equipment (eg., power shovel, bulldozer,
portable conveyor, trucks, etc.)
(4) labor (e.g., operators, supervisors, analytical, etc.), energy
(e.g., electrical power, diesel fuel, etc.), utilities (e.g., water,
sewage, etc.), materials (e.g., chemical additives, spare
parts, etc.), and various overhead administrative and profit
items
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SECTION 7
REFERENCES
1. American Society for Testing and Materials. Annual
Book of ASTM Standards. November 1987.
2. American Society of Agronomy, Inc. Methods of Soil
Analysis, Part 1, Physical and Mineralogical Properties
Including Statistics of Measurement and Sampling. 1982
3. Assink, J.W., and W. Van den Brink. Extractive
Methods for Soil Decontamination: A General Survey
and Review of Operational Treatment Installations. In:
Proceedings from the First International TNO
Conference on Contaminated Soil, Ultrecht, Netherlands,
1985.
4. Bevington, P.R. Data Reduction and Error Analysis
for the Physical Sciences. McGraw-Hill, Inc.. New
York, NY, 1969.
5. Brookes, C.J., I.G Bettefley, and S.M. Loxston.
Fundamentals of Mathematics and Statistics for Students
of Chemistry and Allied Subjects. John Wiley & Sons,
Chichester, Great Britain, 1979.
6. Hites, R.A., and S.J. Eisenreich. Sources and Fates of
Aquatic Pollutants. American Chemical Society,
Washington, D.C., 1987.
7. Kleinbaum, D.G, and L.L. Kupper. Applied Regression
Analysis and Other Multivariable Methods. Duxbury
Press, North Scituate, MA, 1978.
8. Lyman, W.J., W.F. Reehl, and D.H. Rosenblatt.
Handbook of Chemical Property Estimation. Methods,
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11. U.S. Environmental Protection Agency. Data Quality
Objectives for Remedial Response Activities.
EPA/540/G-87/004, OSWER Directive 9355.0-713,
1987.
12. U.S. Environmental Protection Agency. Engineering
Bulletin: Soil Washing. EPA/540/2-90/017, 1990.
13. U.S. Environmental Protection Agency. Generic Quality
Assurance Project Plan for Land Disposal Restrictions
Program (BOAT). EPA/530-SW-87-011, 1987.
14. U.S. Environmental Protection Agency. Guidance for
Conducting Remedial Investigations and Feasibility
Studies Under CERCLA, Interim Final. EPA/
540/G-89/004, OSWER-9335.3-01, 1988.
15. U.S. Environmental Protection Agency. Guide for
Conducting Treatability Studies Under CERCLA, Interim
Final. EPA/540/2-89/058, 1989.
16. U.S. Environmental Protection Agency. Lead Battery
Site Treatability Studies, Project Summary'. 1989.
17. U.S. Environmental Protection Agency. Methods for
Chemical Analysis of Water and Wastes. EPA/
600/4-79/020, 1979.
18. U.S. Environmental Protection Agency. Methods for
Evaluating the Attainment of Cleanup Standards, Volume
1: Soils and Solid Media EPA/730/ 2-89/042, 1989.
Word-Searchable Version - Not a true copy
37
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19. U.S. Environmental Protection Agency. Preparation.
Aid for HWER'Ls Category III Quality Assurance
Project Plans. 1987.
20. U.S. Environmental Protection Agency. Statistical Test
Analysis of Groundwater Data at RCRA Facilities.
Interim Final. 1989.
21. U.S. Environmental Protection Agency. Soil Sampling
Quality Assurance User's Guide. EPA/ 600/4-84/043,
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22. U.S. Environmental Protection Agency. Technology
Screening Guide for Treatment of CERCLA Soils and
Sludges. EPA/540/2-88/004, 1988.
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24. U.S. Environmental Protection Agency. Treatability
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Directive 9380.3-02FS, 1987.
Word-Searchable Version - Not a true copy
38
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United States Center for Environmental Research BULK RATE
Environmental Protection Information POSTAGE & FEES PAID
Agency Cincinnati OH 45268-1072 EPA
PERMIT No. G-35
Official Business
Penalty for Private Use, $300
EPA/540/2-91/020A
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