United States
Environmental Protection Agency
Office of EPA 540-F-98-054
Solid Waste and OSWER-9355.0-72FS
Emergency Response PB99-963301
September 1999
&EPA PresumPtive Remedy
for Metals-in-Soil Sites
DOE Office of Environmental and Policy Assistance (EH-41)
EPA Office of Emergency and Remedial Response (Mail Code 5204-G)
Quick Reference Guide
Since Superfund's inception in 1980, the U.S. Environmental Protection Agency's (EPA) remedial and removal
programs have found that certain categories of sites have similar characteristics, such as the types of contaminants
present, sources of contamination, or types of disposal practices. Based on the information acquired from
evaluating and cleaning up these sites, the Superfund program has developed presumptive remedies to accelerate
cleanups at certain categories of sites with common characteristics. This directive identifies a presumptive remedy
for metals-in-soil sites, and summarizes technical factors (including limitations on the applicability of this directive)
that should be considered when selecting a presumptive remedy for these sites. Development of this presumptive
remedy has been a joint effort between the EPA and the U.S. Department of Energy (DOE).
INTRODUCTION
Presumptive remedies are preferred technologies or
response actions for sites with similar characteristics.
The selection of presumptive remedies is based on
patterns of historical remedy selection practices, EPA
scientific and engineering evaluation of performance
data on remedy implementation, and EPA policies.
To date, EPA has issued presumptive remedies for
municipal landfills, wood treatment facilities, and
volatile organic compounds (VOCs) in soil. EPA
also has developed a response strategy for sites with
contaminated ground water. Implementation of
presumptive remedies is addressed in both
Presumptive Remedies: Policy and Procedures
(OSWER Directive 9355.0-47FS, September 1993),
which outlines and addresses issues common to all
presumptive remedies, and Presumptive Remedies
and NCP Compliance (memo from Costello and
Wyeth to CERCLA Branch Chiefs, June 14, 1995),
which explains their use in the context of the
National Oil and Hazardous Substances Pollution
Contingency Plan (NCP, see 40 CFR 300).
This presumptive remedy directive establishes
preferred treatment technologies for metals-in-soil
waste that is targeted for treatment, and containment
for low-level risk waste requiring remediation. Use
of this presumptive remedy should streamline remedy
selection for metals-in-soil sites by narrowing the
universe of alternatives considered in the Feasibility
Study (FS) or Engineering Evaluation/Cost Analysis
(EE/CA). Specifically, the national administrative
record for metals-in-soil sites established in this
directive can be used to shorten the screening and
detailed analysis steps in the FS. In addition, this
directive identifies technical considerations that
guide selection of an appropriate presumptive remedy
based on site-specific factors, and describes waste
management requirements that may arise at metals-
in-soil sites.
THE METALS-IN-SOIL PRESUMPTIVE
REMEDY
As summarized in Highlight 1, the presumptive
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Highlight 1
The Metals-in-Soil Presumptive Remedy
The presumptive remedy for principal threat metals-in-soil waste that is targeted for treatment is (see Highlight
4 for an explanation of principal threat wastes):
Reclamation/Recovery (when feasible) - Reclamation/recovery is a permanent treatment that separates metal
contaminants from soil in the form of metal, metal oxide, ceramic product, or other useful products that have
potential market value. Reclamation/recovery is usually preceded by physical separation and concentration (e.g.,
soil washing) to produce uniform feed material and/or to upgrade metal content or enhance separation performance.
Reclamation/recovery may be the primary treatment and may include hydrometallurgical or leaching processes.
Compounds in waste can also be converted to metal or matte by transferring undesirable components to a separate
slag phase. Subsequent treatment can be performed to upgrade the metal or matte. Further management of materials
left over may be required to protect human health and the environment once metals are recovered.
Immobilization - Immobilization includes processes that change the physical or chemical properties that impact
the leaching characteristics of a treated waste or decrease its bioavailability and concentration. This treatment locks
metals within a solidified matrix (solidification) and/or converts the waste constituent into a more immobile form,
usually by chemical reaction (stabilization). The process involves mixing a reagent (usually cement kiln dust,
proprietary agents, cement, fly ash, blast furnace slag, bitumen) and generally solidifying the material with the
contaminated soil. Reagents are selected based on soil characteristics and metal contaminants present. The
treatment can be performed ex-situ or in-situ, and in either on- or off-site units. Immobilized materials generally
are managed in a landfill with the associated containment barriers (e.g., caps).
The presumptive remedy for low-level threat metals-in-soil waste that is not targeted for treatment is:
Containment - Containment of metals-in-soil waste includes vertical or horizontal barriers. These remedial
technologies can provide sustained isolation of contaminants and prevent mobilization of soluble compounds over
long periods of time. They also reduce surface water infiltration, control odor and gas emissions, provide a stable
surface over wastes, limit direct contact, and improve aesthetics. Institutional controls generally are used in
conjunction with containment to further limit the potential for unintended access to the waste materials.
remedy for contaminated soils constituting principal
threat wastes (see Highlight 4) at metals-in-soil
sites is:
(1) reclamation/recovery, where it is well-suited to
the waste present at the site; or
(2) immobilization.
In this directive, EPA identifies reclamation/recovery
as a presumptive remedy where it is well-suited to the
type of waste at the site. See page 8 and Appendix E
of this directive for guidance on determining the type
of waste to which this technology is well-suited. If
the site-specific determination is made that
reclamation/recovery is not well-suited for the waste
at a site, immobilization is the presumptive remedy
for principal threat waste.
For low-level threat waste found at metals-in-soil
sites, the presumptive remedy is containment.
In many cases, EPA expects to use a combination of
methods, as appropriate, to achieve protection of
human health and the environment. EPA indicates in
the NCP that it expects to use treatment to address
the principal threats posed by a site, wherever
practicable, and engineering controls, such as
containment, for waste that poses a relatively low
long-term threat or where treatment is impracticable.
Therefore, site managers can expect to use a
combination of the presumptive technologies
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identified in this directive to address metals-in-soil
sites, if appropriate (see section 300.430 of the
NCP).
EPA selected the technologies identified as
presumptive for metals-in-soil sites on the basis of a
national feasibility study analysis conducted on 51
sites. As shown in Highlight 2, one of the three
presumptive remedies was selected at 39 of the 51
sites (nearly 80 percent) evaluated in detail in the
feasibility study analysis. Appendix A provides a
summary of the methodology and results of the
historical remedy review that supports establishing
the national administrative record for metals-in-soil
sites. Appendices B-D provide information on how
the presumptive remedy technologies were evaluated
using the nine NCP criteria at sites included in the
feasibility study analysis.
Highlight 2
Summary of Site Analysis Supporting
Metals-in-Soil Presumptive Remedy*
Technologies Selected to
Address Contaminated
Metals-in-Soil Waste at
Sites Selected for this
Analysis
Immobilization
Reclamation/Recovery
Containment
Institutional Controls
Other On-Site Treatment
Off-Site Disposal
Total Number of
Sites Selecting
Remedy (of 51
sites)
17
9
13
3
2
7
* Bold indicates that the technologies are included in
the presumptive remedy.
SCOPE AND USE OF THIS DOCUMENT
Historically, activities that result in contamination at
metals-in-soil sites are diverse, including chemical
and textile manufacturing; electroplating; smelting;
wood treating, and mining and milling. Soils often
are contaminated with metals as a result of direct
contact with plant waste discharges, fugitive
emissions, or leachate from waste piles, landfills, or
sludge deposits.
This presumptive remedy is intended for use at sites
(or areas of sites) where metal contamination in soils
is a primary problem, including, where appropriate,
areas where metals may be co-located with other
contaminants. These contamination problems are
often complex. For example, organics as well as
metals may be present, and metals may be migrating
into the ground water. These conditions do not
preclude use of this presumptive remedy, but site
managers should use site-specific information
available to determine whether metals are a primary
problem, and whether the presumptive remedy
approaches are viable. Site managers also should
assess if contaminants such as mercury, which are
not within the scope of this presumptive remedy, are
present in concentrations that will affect remediation.
Finally, site managers should determine if other
presumptive remedies (e.g., VOCs in soils, ground-
water presumptive site strategy) are appropriate to
consider and integrate with the remediation of metals
problems. If metals are a primary contaminant of
concern, this presumptive remedy guidance should be
used unless site-specific factors suggest a contrary
approach.
The following sections identify the types of sites and
contaminants that are addressed by this presumptive
remedy. Specifically, these sections:
(1) identify contaminants that are addressed and not
addressed by the metals-in-soil presumptive remedy
guidance;
(2) provide a definition of the soils included in the
"metals-in-soil" category;
(3) address use of the presumptive remedy at mining
and milling sites;
(4) highlight the role of ground water considerations
in the overall site-specific remediation strategy;
(5) outline use of the presumptive remedy by other
programs; and
(6) discuss the link between this presumptive remedy
and innovative technologies.
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Contaminants at Metals-in-Soil Sites. This
presumptive remedy is directed at sites or areas of
sites that primarily contain metals in soil or related
media (e.g., sludges and excavated sediments
containing metals that are amenable to treatment,
consistent with the definition that follows). The
contaminants within the scope of this directive and
the frequency with which they were found at the
evaluation sites are listed in Highlight 3. This
presumptive remedy guidance is applicable to sites
with the contaminants or combinations of
contaminants in Highlight 3, with the exception of
mercury, as noted below.
Highlight 3
Contaminants Found at Metals-in-Soil
Sites Evaluated for this Presumptive
Remedy (of 51 sites)
Contaminant Number of Sites Where Found
Lead 37
Arsenic 35
Cadmium 26
Zinc 24
Copper 20
Chromium 20
Mercury 15
Nickel 13
Antimony 9
Manganese 9
Selenium 8
Iron 7
Barium 6
Beryllium 5
Note: Numbers represent number of times
contaminant was identified as being present in the
FSs or RODs used to develop the presumptive
remedy, and does not necessarily indicate the
contaminant was found in any specific
concentration, or was identified as a principal
threat waste.
Mercury. Because of data limitations in the
analysis, management of soils containing
concentrations of mercury at levels that constitute
principal threat wastes is not addressed by this
presumptive remedy guidance. According to
available literature, including work done by EPA's
Office of Research and Development (ORD), soils
with mercury at higher concentrations may not be
amenable to the technologies that make up the
presumptive remedy for other metals. Site-specific
consideration of mercury remediation technologies
and approaches will be needed where mercury wastes
are present at levels constituting a principal threat
waste. However, remediation methods for mercury
may potentially be combined with presumptive
remedy technologies for metals (e.g., pre-treatment of
soil for mercury followed by presumptive remedy for
metals).
Definition of Soils and Sediments. This
presumptive remedy is directed at sites with metals in
soil. Soils are defined as loose material on the
surface and in the subsurface of the earth consisting
of mineral grains and organic materials in varying
proportions. It also applies to sites with related
media that have similar treatment characteristics (e.g.,
dewatered sludges and sediments).
This presumptive remedy is not necessarily
appropriate for all sediments contaminated with
metals, in part because in situ sediments often pose
additional restoration issues, or because their
excavation or treatment must be balanced with the
potential for harm to sensitive ecosystems. This
presumptive remedy may be appropriate, however,
for sediments once they are excavated, dewatered,
and determined to be amenable to treatments similar
to those described in this document for soils and
sludges. Eleven of the 51 sites studied in this
analysis treated sediments with one of the three
presumptive technologies.
Use at Mining and Milling Sites. Thirteen of the 51
sites studied for this presumptive remedy are mining
and milling sites. EPA expects that site managers
can use this presumptive remedy directive for
discrete metals-in-soil problems at mining sites,
particularly when the problems resemble those found
in more common industrial settings. In many cases,
however, unique site features at these often large
mining sites (e.g., site size, extent of contamination,
nature of metals present, complexities associated
with sensitive ecosystems, speciation of metals) may
lead a site manager to determine that the presumptive
remedy is not practicable to pursue. EPA is studying
alternate remediation strategies for mining-related
problems.
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Ground Water Considerations. Site managers
should consider and integrate the remedial actions
planned for metals-in-soil with the overall
remediation strategy for the site, including other
actions that may be needed for source control or for
remediation of contaminated ground water. In
general, site managers should determine whether the
remedy components selected for metals-in-soil (i.e.,
containment of low-level threat waste and treatment
of principal threat waste) will be effective in
minimizing further migration of metals to ground
water. If site ground water is contaminated and will
be restored, minimizing migration of metals to
ground water probably will be necessary to allow
ground water cleanup levels to be attained. If site
ground water is not contaminated, minimizing
migration of metals to ground water may be
necessary to prevent ground water from becoming
contaminated in the future. For further information
concerning remediation of contaminated ground
water, site managers should consult Presumptive
Remedy Strategy and Ex-Situ Treatment
Technologies for Contaminated Ground Water at
CERCLA Sites, Final Guidance, (OSWER Directive
9283.1-12, October 1996).
Application to Other Programs. This directive is
designed to assist Superfund site managers (i.e.,
Remedial Project Managers (RPMs) and On-Scene
Coordinators (OSCs)) and other personnel in
selecting remedies for cleaning up metals in soil.
Site managers in other programs, such as the
Resource Conservation and Recovery Act (RCRA)
corrective action program, or managers conducting
state or voluntary remediation in the private sector,
should also find the information in this document
useful. For example, the information contained in
this document could be used to eliminate the need for
an alternatives screening step and streamline the
detailed analysis of alternatives in the RCRA
Corrective Measures Study (CMS), which is
analogous to the FS under CERCLA. Federal facility
site managers can use this document to expedite
decision making for all metals-in-soil sites regardless
of the regulatory program to which they are subject.
Use of Innovative Technologies. Innovative
technologies are generally not identified as
presumptive remedies because they have not been
used historically with sufficient frequency.
Nevertheless, some presumptive remedy categories,
such as volatile organic compounds in soil and wood
treatment sites, do include innovative technologies
based on historic remedy selection and other
pertinent considerations. For metals in soil, new
technologies currently being developed focus on
more effective separation/recovery of metals from
soils (such as soil washing, which has been used at
several NPL sites and in other countries),
composting, and phytoremediation. To the degree
that any innovative technologies show promise of
performance or cost advantages, EPA will develop
supplemental bulletins, or update this presumptive
remedy.
As indicated in the Presumptive Remedy Policies and
Procedures directive (OSWER Directive 9355.0-
47FS), EPA expects to consider using innovative
technologies when such technologies offer the
potential for comparable or superior treatment
performance and implementability, fewer or lesser
impacts than other available approaches, or lower
costs for similar levels of performance than
demonstrated technologies. Specifically, as stated in
the Presumptive Remedies: Policy and Procedures,
OSWER Directive 9355.0-47FS, September, 1993:
"The use of the presumptive remedies may
tend to reduce the frequency of full
evaluation of innovative technologies.
However, as indicated previously, the
presumptive remedies provide a tool for
streamlining the remedy selection process.
They do not preclude the consideration of
innovative technologies should the
technologies be demonstrated to be as
effective or superior to the presumptive
remedies. Innovative technologies may be
evaluated and recommended in addition to
the presumptive remedies where these
criteria are met.
EPA encourages review of the latest
Innovative Technologies Semi-Annual
Reports [now entitled Treatment
Technologies for Site Cleanup: Annual
Status Report] or Engineering Bulletins [see
http://www.clu-in.org for the latest
information on treatment technologies] for
the up-to-date information on the potential
effectiveness and applicability of various
innovative technologies. Site managers are
strongly encouraged to involve the site-
expert team to determine whether unusual
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circumstances exist to consider a non-
presumptive remedy based on site-specific
conditions, and/or community, state, and
PRP concerns, or the availability of a
potentially promising innovative
technology."
THE PRESUMPTIVE REMEDY PROCESS
FOR METALS-IN-SOIL SITES
When developing a strategy for implementing this
presumptive remedy for metals in soil, site managers
should be aware of three objectives that data
collection in the RI/FS needs to support. The
technologies included in this presumptive remedy are
categorized according to the nature of the metal
wastes found at the site, i.e., whether or not the
wastes are principal threat wastes. Therefore, the
first objective at a metals-in-soil site is to make an
early determination as to whether any source
material wastes are considered principal threat wastes
based on their toxicity or mobility (see Highlight 4).
As discussed on page 8, this determination is based
on waste characteristics (e.g., mobility and
concentrations), degree of risk, or other site-specific
factors.
Once the determination has been made that principal
threat waste is present at a site, the second objective
is to decide whether the waste present at the site is
well-suited for recovery/reclamation. This
determination is based on the waste characteristics
and technical factors identified on page 8. For
example, reclamation/recovery is usually well-suited
for situations with high concentrations of valuable or
easily volatilized material. Data will be needed to
answer the question of whether reclamation/recovery
is a viable alternative, or whether it should be
eliminated from further consideration. If
reclamation/recovery is not well-suited,
immobilization is the other available presumptive
remedy treatment technology for principal threat
wastes at metals-in-soil sites.
Highlight 4
Description of Principal and Low-Level Threat Wastes
Identification of principal threat and low-level threat wastes should occur, on a site-specific basis, when
characterizing source materials. "Source material" is defined as material that includes or contains hazardous
substances, pollutants, or contaminants that act as a reservoir for migration of contamination to ground water,
surface water or air, or act as a source for direct exposure. Contaminated soil, sediments, and sludges can all be
classified as source materials.
Principal threat wastes are source materials considered to be highly toxic or highly mobile that generally cannot
be reliably contained or would present a significant risk to human health or the environment should exposure occur.
Examples include surface soil or subsurface soil containing high concentrations of contaminants of concern that
are (or potentially are) mobile due to wind entrainment, volatilization, surface runoff, or sub-surface transport; and
highly-toxic source material, such as soils containing significant concentrations of highly toxic materials. No
"threshold level" of toxicity/risk has been established to equate to "principal threat." However, where toxicity and
mobility of source material combine to pose a potential risk of 10"3 or greater, generally treatment alternatives
should be evaluated.
Low-level threat wastes generally include contaminated source material of low to moderate toxicity, such as
surface soil containing contaminants of concern that generally are relatively immobile to air or ground water (i.e.,
non-liquid, low volatility, low teachability contaminants such as high molecular weight compounds) in the specific
environmental setting; and low toxicity source material, such as soil and subsurface soil concentrations not greatly
above reference dose levels or that present an excess cancer risk near the acceptable risk range.
For more information, see .4 Guide to Principal Threat and Low Level Threat Wastes (9380.3-06FS, Nov. 1991).
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The third objective to be accomplished at metals-in-
soil sites is to identify waste handling issues that can
be anticipated based on the waste present and the
presumptive remedy selected. For example, at many
metals-in-soil sites, the land disposal restrictions
(LDRs) under RCRA will be applicable or relevant
and appropriate requirements (ARARs), and may
affect waste handling practices and development of
remedial responses (e.g., treatment levels) depending
on the presumptive remedy selected. Page 12
provides an explanation of waste handling issues.
The numbered steps provided in Highlight 5 are
explained below and outline the process that site
managers should generally follow in:
(1) identifying principal and low-level threat wastes
for metals-in-soil sites through site characterization;
Highlight 5
Process for Selecting Presumptive Remedies
Process Step
1. Identify Principal and
Low-Level Threat Wastes
2. Select Appropriate
Presumptive Remedy Based
on Technical
Considerations
3. Identify Waste
Handling Issues
4. Document the Selected
Remedy
Notes
Identify based on
contaminant concentrations
present and the toxicity and
mobility of the
contaminants.
Evaluate hierarchy of
presumptive remedies and
consider technical factors
in order to determine
viable approach.
Includes consideration of
on/off site management of
waste, in/ex-situ treatment,
and RCRA Land Disposal
Restrictions
The Feasibility Study (or
EE/CA), Proposed Plan,
and Record of Decision
should all refer to the
presumptive remedy
selection process used at
the site.
Principal Threat Waste-
" Source materials
considered to be highly
toxic or mobile.
Low-Level Threat Wastes-
Generally include
contaminated source
material of low-moderate
toxicity/mobility.
Site managers should also
consider the properties of the
waste they are addressing,
and consider including design
engineers in technical aspects
of the remedy selection
process.
The Phase IV LDR
treatment standards for
contaminated media were
promulgated in May,
1998 at 40 CFR 268.48.
'A copy of this presumptive
remedy guidance and its
attachments should be
included in the
administrative record.
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(2) selecting the most appropriate presumptive
remedy technology for metals-in-soil waste based on
technical considerations;
(3) considering waste handling issues such as the
land disposal restrictions, and
(4) documenting in the FS, Proposed Plan, and ROD
how the presumptive remedy process was used to
select the remedy.
As with any presumptive remedy, early involvement
of the PRP, State, and community stakeholders is a
fundamental part of the process, where the intent is to
streamline the response selection process. Starting at
scoping, site managers should elicit stakeholder input
about the presumptive remedy process. If the public
expresses strong opposition to the presumptive
remedy under consideration, site managers may need
to include non-presumptive remedy options in the
evaluation. In this case, site managers may evaluate
alternative technologies along with the presumptive
remedy. Technology evaluation and screening
information must be developed and included in the
site Administrative Record for the alternative
technologies.
1. Identify Principal and Low-Level Threat
Wastes. During this step, the site manager
characterizes the nature and extent of the
contamination problem, and determines whether
wastes should be characterized as principal threat
waste and/or low-level threat waste (Highlight 4).
Principal threat wastes generally should be addressed
through treatment-oriented remedies, unless
impracticable, while engineering controls, such as
containment, generally are the preferred remedial
approach for low-level threat wastes. Any remedy
selected for a metals-in-soil site should be consistent
with reasonably anticipated future land uses, where
possible. Therefore, early identification of
reasonably anticipated future land uses will help in
the determination of whether a presumptive remedy
is appropriate and which of the technologies best
meets future land uses. For example, containment of
metals in soil in place may be inconsistent with a
residential future land use. Future land uses also are
part of the judgments needed to conduct a baseline
risk assessment, which in turn may help determine
whether or not principal threat waste and/or low-level
risk waste is present at a site. Site managers should
consult EPA's guidance on land use in the Superfund
remedy selection process (See Land Use in the
CERCLA Remedy Selection Process, OSWER
Directive No. 9355.7-04, May 25, 1995). The key to
assessing this factor is early and continued
interaction with citizens, local governments, and
community organizations.
In some cases, metals concentrations will be low
enough that a response action is not warranted for
portions of a site. Site managers should review the
Soil Screening Level Guidance (SSL) (see Soil
Screening Guidance: Users' Guide, OSWER
Directive 9355.4-23, April 1996), other pertinent
EPA policies, and risk assessment results to
determine if no further action is warranted. By
providing information to assist site managers in
screening out certain areas containing metals in soil
from further study, the SSL guidance streamlines the
data collection process and focuses the remedy
selection on the metal contaminants of concern at the
site. In residential scenarios, where contaminant
concentrations equal or exceed SSLs, further
study or investigation, but not necessarily
cleanup, generally is warranted.
2. Select Appropriate Presumptive Remedy Based
on Technical Considerations. For principal threat
wastes, this directive offers two technologies for site
managers to evaluate, both of which have proven
successful in meeting a wide range of remedial
objectives. As discussed below,
reclamation/recovery is well-suited to certain types of
wastes (see also Appendix E). If the waste at the site
is amenable to reclamation/recovery, then site
managers should consider reclamation/recovery
before considering use of immobilization.
Site managers may want to have design engineers
participate in the determination of which presumptive
remedy alternatives are appropriate for consideration.
One advantage of presumptive remedies is that it may
be possible to accelerate initiation of the remedial
design (and therefore remedial action) by focusing on
a limited set of approaches from the beginning;
therefore, site managers should focus as early as
possible on the design aspects of the selected
technology, particularly by identifying what data are
needed for design.
Technical Considerations For the Metals-in-Soil
Presumptive Remedy. There are many technical
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Highlight 6
Reduction/Separation Technologies
(e.g., Soil Washing)
Reduction/separation technologies (e.g., soil
washing) used as part of a treatment train may
make a remedy more cost effective by removing
metal contaminants from soil; thereby reducing
the toxicity, mobility, and volume of waste
requiring treatment.
Reduction/separation technologies are ex-situ
remediation technologies that use a combination
of physical separation and aqueous-based
separation unit operations to reduce contaminant
volume and concentrations to site-specific
remedial goals. Technologies such as soil
washing are performed on excavated soils and
may involve some or all of the following
depending on the contaminant-soil matrix
characteristics, cleanup goals, and specific process
employed: (1) mechanical screening, (2) crushing,
(3) physical processes to liberate weakly bound
agglomerates, (4) treatment of coarse-grained soil
fractions), (5) treatment of fine-grained
fraction(s), and (6) management of generated
residuals.
considerations that site managers may need to
examine when applying the presumptive remedy and
other aspects of this directive to metals-in-soil sites.
When addressing sites contaminated with metals in
soil, site managers should consider, on a site-specific
basis, the use of reduction/separation technologies in
conjunction with the identified presumptive
remedies, when appropriate. Highlight 6 and
Appendix D provide additional information on
remediation technologies, and Appendix E identifies
data requirements to help determine the applicability
of presumptive technologies to metals contamination.
Considerations When Selecting Reclamation/
Recovery. Multiple factors may influence the choice
to recover or separate metals, such as the economic
viability of recovery, vendor availability, post-
treatment requirements depending on the metals
present; and concentration of the mixture of volatile
and nonvolatile metals that require multiple process
steps. Reclamation/recovery often is amenable to
situations with high concentrations of valuable or
easily volatilized materials. For zinc, lead,
cadmium, nickel, and chromium it may be
economically viable to recover metals from large
volumes of waste with high concentrations at 5-20%.
In addition, proven technology exists for recovering
material containing greater than 40% lead.
Reclamation/recovery may be appropriate for sites
with lower metal concentrations if the metals easily
reduce and vaporize (e.g., mercury) or are
particularly economically valuable (e.g., gold).
Lower concentrations of metals typically are
processed by hydrometallurgical methods. Due to
economies of scale, reclamation/recovery
technologies generally work best for a continuous
feed of large volumes of metals.
A limited range of suitable particle sizes is associated
with reclamation/recovery. Large clumps or debris
tend to slow heat transfer and require removal prior
to treatment. Fine particles tend to become entrained
in gas flows that increase the dust generated.
Moisture also has a negative effect on the process by
increasing energy requirements and causing material-
handling problems. Thus, free moisture should not
be present during the process. Higher temperatures
for processing are preferred as the treatment requires
the ability to transfer heat into the matrix. Nitrates,
sulfur compounds, phosphates, and halides may form
corrosive gases, nonvolatile sulfides, and volatile
metal species that may impede effective treatment.
Reclamation/recovery often is not practicable for
projects that lack economic viability (i.e., the cost of
implementing the technology significantly outweighs
revenues generated by the resale/re-use of recovered
materials); however, if the total costs of reclamation/
recovery are comparable with other protective
alternatives, then reclamation/recovery should still be
considered. For more information, see Contaminants
and Remedial Options at Selected Metal-
Contaminated Sites (EPA/540/R-95/512, July 1995).
Considerations When Selecting Immobilization.
Immobilization satisfies CERCLA's preference for
treatment of principal threat wastes, is generally
effective for metals, and is a commercially available
and demonstrated technology. Immobilization works
well for particular oxidation states of arsenic and
chromium. When addressing lead and cadmium,
immobilization may be more effective when a single
metal is present.
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The effectiveness of immobilization treatment,
however, is dependent on several factors. First,
identifying a suitable reagent (e.g., fly ash, Portland
cement) may be difficult. Without a reagent that has
the ability to mix with waste uniformly and
thoroughly, contamination may not be significantly
reduced. Second, it may be difficult to identify a
reagent that simultaneously reduces the mobility of
multiple contaminants. Third, the presence of
organics may interfere with the bonding of wastes
with reagents.
Other contaminants can present additional problems.
For example, VOCs may vaporize during the process.
(If VOCs are present in high concentrations, they
should be addressed prior to treatment.)
Contaminants such as oil, grease, phenol, soluble
salts of some metals, cyanide, and sulfate may inhibit
proper bonding of reagent with waste; retard setting
of treated material; and/or reduce durability, bearing
strength, and leach resistance of the final product.
If a site manager chooses to use immobilization,
performance standards should be established in the
ROD, which may be based on risk to human health or
the environment, or ARARs. For example, if the
RCRA Land Disposal Restrictions (LDRs) are
ARARs, then specific leaching performance
standards and tests may be required to be met. Off-
site disposal of RCRA hazardous waste will also
need to comply with RCRA LDRs. Disposal of the
immobilized material on-site may also mean that risk-
based performance standards need to be set to ensure
that the remedy is protective of human health and the
environment, and will maintain integrity over time
due to such factors as freezing conditions, or load.
Risk-based standards should be considered
particularly if there is the potential for leaching to
ground water or emissions to air. Standards that may
need to be set based on disposal on-site include:
contaminant leaching level determined based on
ground-water modeling or potential air emissions;
bearing strength; and freeze-thaw durability. In
addition, the NCP preamble states that the Superfund
program uses as a guideline for effective treatment
the range of 90 to 99 percent reduction in the
concentration or mobility of contaminants of
concern. (55 FR page 8701, March 8, 1990).
Furthermore, site managers should also note that a
treatability study is generally recommended before
implementing an immobilization remedy. As with
other technologies cited in this presumptive remedy,
proper treatment and disposal for the final product is
assumed.
As an in-situ treatment, immobilization has been
demonstrated to be effective at depths up to 30 feet
and may be feasible up to 150 feet. The presence of
subsurface barriers, debris, and boulders impedes
delivery of the reagent to contaminated soil and
impedes the complete and uniform mixing of the
reagent with the waste. Further, because the
presence of clays and oily sands may limit the
effectiveness of in-situ immobilization, these
composites can be more effectively treated if ex-situ.
For more information, see Contaminants and
Remedial Options at Selected Metal-Contaminated
Sites (EPA/540/R-95/512).
Treatment of Chromium. Although historical
analysis shows that immobilization can be effective
for treating Cr(VI), other treatment methods, singly
or in combination with immobilization, may improve
immobilization's effectiveness. For example,
reduction of Cr(VI) to principally insoluble Cr(III)
reduces many of the mobility and toxicity concerns
otherwise present with Cr(VI). However,
establishing conditions that maintain irreversibly the
Cr(III) and prevent oxidation back to Cr(VI) can be
difficult, particularly if the treatment is done in-situ.
If treatment takes place ex-situ, maintaining the
Cr(III) oxidation state may be easier in the long term.
Final disposal units may also require long-term
monitoring to ensure that the Cr(III) valence is
maintained.
Treatment of Arsenic. Treatment of arsenic may be
strongly affected by the species present, reactions
with other compounds, and soil and site conditions.
Research by EPA's Office of Research and
Development, summarized in Engineering Bulletin:
Technology Alternatives for the Remediation of Soils
and Sediments Contaminated with Arsenic,
Cadmium, Chromium, Mercury, and Lead
(EPA/540/S-97/500, August 1997), shows that most
arsenic compounds are strongly sorbed by soils and
sediments at pH 4.5 to 5.0 and thus are relatively
immobile, but other arsenic compounds in other
conditions are much more mobile. Site managers
should use caution when selecting immobilization for
arsenic due to sensitivity in the effectiveness of
treatment in different pH conditions. The Bulletin
states that "EPA does not preclude use of
[immobilization] for treatment of arsenic (particularly
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inorganic arsenic) wastes, but recommends that its
use be determined on a case-by-case basis." This
should be accomplished through use of a site-specific
treatability study to supplement the administrative
record.
Considerations When Selecting Containment of
Metals in Soil. Containment is often a relatively
inexpensive, commercially available, and
demonstrated technology for remediating metals
contamination in soils. Also, containment generally
is protective and cost-effective for areas of shallow,
wide-spread, and low-level contamination.
Caps and vertical barriers must be designed to
conform to any ARARs (unless waived) such as
RCRA landfill closure requirements, and/or to
address exposure pathways of concern (e.g., dermal
exposure). Within these constraints, the type of cap
or vertical barrier needed also may be partially
dependent upon climate-related factors, including
levels of rain and snow fall, and also dependent upon
the amount of surface run-on and run-off. Cost and
implementability issues may make containment
preferable for large areas of contamination.
Containment may not be effective, however, for sites
with a high ground-water table or sites located on a
floodplain. Furthermore, containment does not
involve treatment, nor does it reduce toxicity or waste
volume, and generally will restrict future uses of a
site.
For more information on containment, see
Contaminants and Remedial Options at Selected
Metal-Contaminated Sites (EPA/540/R-95/512, July
1995).
Co-Mingled/Located Waste (e.g., organics) and
Related Issues. In many cases, metals contamination
will be co-located with other contaminants, such as
organics, or it will be found at types of sites for
which EPA has already issued a presumptive remedy
(e.g., wood treater sites) or other remediation
guidance. The presence of other contaminants such
as organics does not automatically preclude the use
of this directive. Rather, site managers need to
determine how to apply this directive and to evaluate
whether the presence of certain other contaminants,
such as organics in high concentrations, may limit the
effectiveness of the identified presumptive remedy
technologies. Organics were present in varying
concentrations at 30 of the 51 sites evaluated in the
accompanying Feasibility Study Analysis Report, and
in 22 of these 30 cases (73 percent), one of the three
presumptive technologies was still selected.
Where metals are co-located with other contaminants,
site managers should evaluate the following key
questions in order to use the information in this
presumptive remedy effectively and obtain the
intended benefits.
* Can metals problems be addressed
separately from other problems co-located at
the site (e.g.. are they found in discrete
geographic locations within the same site)?
Are wastes with other contaminants
amenable to effective treatment by the
presumptive remedy technologies selected?
If so, the guidance in this presumptive
remedy can be applied without significant
modification. Within the Proposed Plan and
ROD, site managers should clearly indicate
the portion of the site's problems to which
this directive is being applied and for what
portions a more site-specific analysis of
alternatives was conducted.
* If metals problems cannot be considered
separately from other problems (or other
contaminants lessen a treatment's
effectiveness), has EPA issued a
presumptive remedy or other remediation
guidance that addresses the other problems?
For example, if the co-located problem with
metals is volatile organic compounds
(VOCs) in soils, site managers should
consult the existing presumptive remedy for
VOCs in soil, and consider whether
information from both presumptive remedy
documents can be used to select a remedy
that addresses the co-located problems.
This situation often will require a treatment
train using a combination of technologies to
meet both risk-based objectives as well as
any additional requirements such as those
posed by RCRA LDRs. Presumptive
remedy benefits (e.g., streamlined screening
and analysis of alternatives in the feasibility
study) should still be available by relying on
the national administrative records available
for each presumptive remedy.
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In cases where other presumptive remedies already
address metals-in-soil problems (e.g., wood treater
sites where chromium and arsenic problems are often
found), the more site-specific presumptive remedy (in
this example, wood treaters) should be followed.
Finally, if other presumptive remedy guidance is not
available for the co-located problem, site managers
should use this directive to the extent possible to
select a remedy that complies with CERCLA and the
NCP. Consultation with stakeholders, internal
counsel, and technical experts will be important in
finalizing the remediation action decision.
3. Identify Waste Handling Issues. Several
interrelated issues often arise at metals-in-soil sites
that have important impacts on planning the
implementation of the presumptive remedy outlined
in this directive. These issues include on-site vs. off-
site management of wastes, in-situ vs. ex-situ
treatment of the wastes, and compliance with a
variety of RCRA requirements, including land
disposal restrictions (LDRs).
On/Off-Site Management of Metals-in-Soil Waste.
Analysis of the 51 Records of Decision evaluated for
this directive indicate that management of metals-in-
soil waste can occur on and/or off site. If off-site
management of the wastes is selected, which may be
appropriate in certain cases on a site-specific basis,
treatment to applicable RCRA and other standards
often will be required. Site managers also must
comply with the provisions of the Off-Site rule (see
40 CFR 300.440) in selecting a facility to manage the
wastes. This selection includes evaluating the
compliance status of the receiving facility and
conducting appropriate waste characterization during
a remedial investigation to meet the receiving
facility's waste acceptance criteria. (On-site
management may also trigger the RCRA land
disposal restriction standards if the materials contain
a RCRA waste, and it is placed outside the area of
contamination.) This presumptive remedy directive
does not preclude reclamation/recovery,
immobilization, or containment from taking place
either on- or off-site.
In/Ex-Situ Treatment. None of the 51 sites
evaluated for this directive had in-situ treatment of
the metals-in-soil waste. However, in-situ treatment
is often an effective option for managing metals-in-
soil waste, particularly when this option is used in
conjunction with containment options. Both in- and
ex-situ immobilization are included as options for
implementing the presumptive remedy in the scope of
this directive.
Key factors to evaluate in determining whether in- or
ex-situ treatment of metals-in-soil waste should occur
include: (1) the effectiveness of the treatment option;
(2) the long-term impact on land use of the option
selected; (3) the availability and implementability of
ex-situ management, particularly if off-site options
are preferred; and (4) the ability to meet ARARs (see
RCRA Land Disposal Restriction discussion below).
RCRA Land Disposal Restrictions. Many metal
wastes found at Superfund sites will be hazardous
under the Resource Conservation and Recovery Act
(RCRA). Depending on the source of these wastes,
the contaminant types and concentrations, and the
remedy selected, these wastes often may be subject to
RCRA Subtitle C regulations, such as the treatment
standards under the land disposal restrictions
(LDRs), as an ARAR. In addition, State hazardous
waste regulatory programs also may have
requirements that must be met as ARARs. The
following are the key RCRA and hazardous waste
management issues that site managers must evaluate
when using this directive:
* Determine if the soil is or contains a RCRA
hazardous waste and, if it is a hazardous
waste, determine the waste code(s). If the
soil is a RCRA characteristic waste or if the
soil contains a listed RCRA waste, certain
RCRA requirements may apply when
carrying out this presumptive remedy. The
RCRA waste codes determine the specific
RCRA requirements that will apply,
including the universal treatment standards
(UTSs) under LDRs. In addition, LDRs
require waste characterization to determine
the presence of any underlying hazardous
constituents reasonably expected to be
present, which also may be subject to the
UTSs contained in 40 CFR 268.48 for soil,
and 40 CFR 268.45 for debris.
* Evaluate whether placement occurs. LDRs
are triggered when restricted RCRA
hazardous wastes are "placed" or "land
disposed" (i.e., placed in a landfill, surface
impoundment, waste pile, injection well,
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land treatment facility, salt dome formation,
salt bed formation, or underground mine or
cave (see RCRA section 3004(k)) or other
units where waste is placed on the land).
Determining the waste codes will be
especially important when remediation
occurs ex-situ or off-site because wastes
managed in these ways often are considered
to be "placed" or "land disposed." Wastes
treated in-situ, or consolidated within an
area of contamination, or an LDR-exempt
unit (such as a corrective action
management unit, described below) may not
trigger LDR requirements because they are
not "placed" during the implementation of
the remedy; however, in some cases, waste
managed on-site may trigger the LDR
standards.
If LDRs are triggered, evaluate compliance
options. A variety of options are available
to comply with the LDR standards. Under
current policy, the preferred approach to
complying with LDRs is treatment to the
contaminated media standards (see 40 CFR
268.49). EPA promulgated the final LDR
treatment standards for soil in May 1998.
Prior to this ruling, soil that contained listed
hazardous waste or exhibited a characteristic
of hazardous waste was prohibited from
land disposal unless it had been treated to
meet the treatment standards promulgated
for pure industrial hazardous waste; in other
words, the same treatment standards that
applied to a pure, industrial hazardous waste
also applied to soil contaminated with that
waste.
EPA chose to develop soil treatment
standards that can be achieved using a
variety of non-combustion treatment
technologies that achieve substantial
reductions in concentration or mobility of
hazardous constituents. The final rule
requires all hazardous contaminated soil,
including soil contaminated by listed
hazardous waste, to be treated for each
underlying hazardous constituent reasonably
expected to be present when such
constituents are initially found at
concentrations greater than ten times the
universal treatment standard. The treatment
standards promulgated in this rule may be
applied to any contaminated soil that is
restricted from land disposal, including but
not limited to soil contaminated by metal
and mineral processing wastes (refer to the
memorandum entitled Management of
Remediation Waste Under RCRA,
distributed October 14, 1998 (EP530-F-98-
026).
Other LDR compliance options also
continue to exist. For example, under
current regulations, "remediation wastes"
can be managed in corrective action
management units (CAMUs) or temporary
units and not be subject to LDR
requirements. In addition, a unit receiving
LDR-restricted waste can receive a no-
migration variance and not have to meet
LDR treatment standards. Another
compliance option is the site-specific
treatability variance for contaminated soil
and debris. This variance may still be used
if the LDR standard cannot be met (although
the LDR standard for soil is no longer
considered to be presumptively
inappropriate (see 63 FR 28,621, May 26,
1998). The variance does not remove the
requirement to treat restricted soil and debris
wastes; rather the variance establishes
alternate treatment levels based on data from
actual treatment of soil. This option may be
appropriate to pursue when materials will be
managed ex-situ on site and may not meet
the LDR requirements for all underlying
hazardous constituents.
Evaluate other RCRA regulations that could
interact with the LDRs. RCRA regulations
other than the LDRs can apply when
implementing the metals-in-soil presumptive
remedy. For example, where RCRA
hazardous wastes are contained on-site,
RCRA closure requirements may be
ARARs. EPA has issued a wide variety of
policy guidance on complying with these
and other RCRA requirements.
4. Document the Selected Remedy. When
implementing this presumptive remedy, a general
explanation of how the presumptive remedy process
affects remedy selection should appear in the FS,
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Proposed Plan, and ROD, along with a discussion of
any site-specific factors that significantly affected
selection of the remedy. The following sections
provide a brief summary of the type of information
that should be included. For additional information,
refer to the Guidance on Preparing Superfund
Remedial Decision Documents, (EPA 540-R-98-031)
(expected final date is 1999).
In addition, a copy of this presumptive remedy
guidance and its accompanying attachments should
be included in the Administrative Record for the
site. These materials will assist in supporting the
selection of the presumptive remedy and will
Highlight 7
Required Elements of the
Administrative Record for Presumptive
Remedy Sites
In order to meet the Administrative Record
requirements for presumptive remedies, the site-
specific Administrative Record should include the
following*:
1) Relevant OSWER generic presumptive
remedy documents;
2) A "bridging" memorandum or other
documentation which shows whether the
presumptive remedy fits the site;
3) A site-specific analysis discussing how
the presumptive remedy fits under the
three site-specific remedy selection
criteria (ARAR compliance, state
acceptance, and community acceptance);
4) EPA's written responses to comments
which pertain to EPA's decisions
regarding the use of presumptive
remedies;
5) A site-specific response to any comments
regarding new technology; and
6) A notice in the Administrative Record
file index regarding the availability of the
data upon which any presumptive remedy
is based.
* summarized from memo, Presumptive Remedies
and NCP Compliance, from Costello and Wyeth
to CERCLA Branch chiefs, June 14, 1995.
constitute the initial screening step of the FS or
EE/CA and support the streamlining of the detailed
analysis portion of the FS or EE/CA. The site-
specific administrative record should be prepared and
contain the elements outlined in Highlight 7. More
information about administrative record requirements
in general can be found in Presumptive Remedies
and NCP Compliance (memo from Costello and
Wyeth to CERCLA Branch Chiefs June 14, 1995).
The Feasibility Study. The FS should explain that
the nationwide Feasibility Study Analysis report,
prepared in support of this presumptive remedy,
substitutes for the site-specific technology
identification and screening steps of the FS. For sites
with principal threat wastes that will be treated, if
reclamation/recovery was found to be well-suited for
the waste, consideration of additional treatment
technologies generally is not necessary. In this case,
the FS should only include the reclamation/recovery
alternative(s) and the no action alternative for the
principal threat waste. The finding that
reclamation/recovery is not well-suited can be a
relatively simple determination based on an
evaluation of existing data and the technical
considerations provided in this directive; it generally
need not entail additional data collection or complex
feasibility evaluations. In this case, treatment
alternatives considered in the FS for principal threat
waste generally will include only those related to
immobilization and the no action alternatives. As
noted in the June 14, 1995 memo from Costello and
Wyeth to CERCLA Branch Chiefs, if outside parties
submit comments in support of technologies other
than those identified in the FS, then such comments
must be adequately addressed.
Feasibility Studies for sites implementing this
presumptive remedy likely will contain an array of
alternatives that include the presumptive treatment
technologies combined with other
treatment/containment features, or responses to other
site-specific contamination problems. For example,
alternatives for a given site could include some or all
of the following:
pre-treatment steps (e.g., reduction/
separation technologies, soil washing) in
combination with presumptive remedy
treatment technologies;
more than one containment option;
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containment of low-level waste in
combination with treatment technologies;
alternatives to address ground-water
contamination; and/or
provisions for institutional controls.
In the FS, site managers must evaluate each of the
alternatives being considered against the nine criteria
set forth in section 300.430(e)(9) of the NCP. This
evaluation is a key component of the Administrative
Record. Appendix B provides a generic evaluation
of each of the technologies in the presumptive
remedy against these criteria (excluding state and
community acceptance and state ARARs). After
augmenting or modifying them as necessary with
site-specific information, site managers can use these
analyses to support final remedy selection.
The Proposed Plan and ROD. Certain sections of
the Proposed Plan and ROD should clearly describe
the presumptive remedy selection process. In
general, references to the presumptive remedy should
be included in the following sections, as appropriate:
Community Participation Section, Scope and Role of
Operable Unit or Response Action Section, Site
Characteristics Section (if streamlining occurred as a
result of presumptive remedy); and Description of
Alternatives Section.
References. Highlight 8 provides a list of EPA
policies and documents that may be relevant to
consider when applying the presumptive remedy
guidance described in this directive.
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Highlight 8
Other Relevant EPA Policy and Technical Documents
EPA numbers, and OSWER numbers when available, are listed. To obtain copies of a document, call the
RCRA/CERCLA hotline at 1-800-424-9346. Documents can be ordered using either an EPA number or an
OSWER number.
1. U.S. EPA, Groundwater Issue, Behavior of Metals in Soils, by Joan E. McLean and Bert E. Bledsoe.
EPA 540/S-92/018, October, 1992.
2. U.S. EPA, A Guide to Principal Threat and Low Level Threat Wastes, OSWER 9380.3-06FS,
November 1991.
3. U.S. EPA, Presumptive Remedies: Site Characterization and Technology Selection for CERCLA Sites
with Volatile Organic Compounds in Soils. OSWER 9355.0-48 FS, EPA/540-F-93-048, September,
1993.
4. U.S. EPA, Presumptive Remedy for CERCLA Municipal Landfill Sites. OSWER 9355.0-49FS,
EPA/540-F-93-035, September, 1993.
5. U.S. EPA, "Feasibility Study Analysis and Administrative Record for Presumptive Remedies"
memorandum from David A. Bennett, September, 1994.
6. U.S. EPA, Feasibility Study Analysis for CERCLA Sites With Volatile Organic Compounds in Soil,
August, 1994. OSWER 9356.0.01, EPA 540/R/94/080.
7. U.S. EPA, Groun dwater Issue, Natural Attenuation ofHexavalent Chromium in Groundwater and
Soils, by Carl D. Palmer and Robert W. Puls. EPA/540/S-94/505, October, 1994.
8. U.S. EPA, Engineering Bulletin, Selection of Control Technologies for Remediation of Soil
Contaminated with Arsenic, Cadmium, Chromium, Lead, or Mercury, EPA/540/S-97/500, March 1997.
9. U.S. EPA, Contaminants and Remedial Options at Selected Metal-Contaminated Sites. EPA/540/R-
95/512, July, 1995.
10. U.S. EPA, "Land Use in the CERCLA Remedy Selection Process," OSWER Directive 9355.7-04, May,
1995.
11. U.S. EPA, Presumptive Remedies andNCP Compliance memorandum from James E. Costello and
George B. Wyeth, June 14, 1995.
12. U.S. EPA, Technology Screening Guide for Radioactively Contaminated Sites, EPA/402/R-96/017,
November, 1996.
13. U.S. EPA, Presumptive Remedies for Soils, Sediments, and Sludges at Wood Treater Sites. EPA/540/R-
95/128, December, 1995. OSWER 9200.5-162.
14. U.S. EPA, 5-0/7 Screening Guidance: User's Guide. OSWER 9355.4-23, EPA/540/R-96/018, July,
1996.
15. U.S. EPA, Stabilization/Solidification Technology for Mixed Wastes. February, 1996.
16. U.S. EPA, Presumptive Response Strategy andEx-Situ Treatment Technologies for Contaminated
Ground Water at CERCLA Sites. OSWER 9283.1-12, EPA/540/R-96/023, October, 1996.
17. U.S. EPA, Presumptive Remedies: Policy and Procedures, September, 1993, OSWER 9355.0-47 FS.
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APPENDIX A
TECHNICAL BASIS FOR PRESUMPTIVE REMEDIES
This Appendix summarizes the analyses that EPA conducted on Feasibility Study (FS) and Record of Decision
(ROD) data from Superfund metals sites that led to reclamation/recovery, immobilization, and containment in place
as the presumptive technologies for metals sites with contaminated soil. EPA conducted the following activities:
* Identified all metals-in-soil sites (270) and analyzed in detail a subset (51) of Feasibility Studies and
Records of Decision for metals-in-soil sites to determine what technologies were selected and the
circumstances of their selection;
* Reviewed EPA and other policies and technical literature associated with the metals found at Superfund
sites and technologies for remediating metals, including information about any emerging technologies that
might be appropriate for use in the future;
* Evaluated EPA and other policies and requirements for implementing remedies for metals, such as best
demonstrated available technologies established under RCRA land disposal restrictions; and
* Reviewed the results of the analysis to determine if the technologies selected based on analyzing either
historical patterns or emerging issues should be modified based on technical judgment.
Of the documents identified in Exhibit 4, EPA relied significantly on the following in this process:
* Presumptive Remedies: Policies and Procedures (EPA540-F-93-047, September 1993);
* Contaminants and Remedial Options at Selected Metal-Contaminated Sites (EPA 540-R-95-512, July
1995)
Identification of the Universe of Metals Sites
EPA started by reviewing abstracts and databases of all Superfund Records of Decision from 1988 to 1994. This
group was screened to identify sites that had metals as a primary contaminant of concern (i.e., metals were identified
as a risk driver or a contaminant for which active management would be required). Approximately 270 sites were
identified in this category. From this set of 270 sites, EPA used expert judgment and analytical tests to select a
representative sample of 51 sites for detailed analysis. This subset is consistent with EPA policy guidelines that
between 10 and 20 percent of sites require review when evaluating a presumptive remedy (Presumptive Remedies:
Policy and Procedures, September 1993, EPA 540-F-93-047). In addition, EPA also evaluated in detail metal-
contaminated sites at which "no action" or "institutional controls" only were selected as the remedy. These sites
were used to determine under what circumstances, if any, limited remediation of metal contaminated sites was
warranted. Detailed discussion of the methodology for site selection is available in two working papers included in
the national Administrative Record for this presumptive remedy.
From the sample of 51 sites, EPA reviewed in detail the data in the documents prepared during the remedy selection
process. These data were used to identify the technologies selected and to identify site circumstances that led to the
selection of one remedy rather than others. Types of data evaluated included information related to site conditions
(e.g., type of site, waste units present), contaminant characteristics (e.g., species, mobility), waste characteristics
(e.g., volume, physical relationship to ground water), and the remedial alternatives accepted and rejected (e.g., cost,
analysis against the NCP screening and detailed analysis criteria). A complete list of data gathered for each site and
sample site report compiled is shown in the Feasibility Study Analysis Report.
Based on the data collected, EPA analyzed several variables in detail:
A-l
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* Frequency of selection of the preferred remedial alternative;
* Rationale for selection of the preferred remedial alternative; and
* Rationale for rejection of other alternatives proposed in initial lists of potential remedies but either
screened out or not selected after the detailed analysis of alternatives.
EPA also evaluated how combinations of site factors affected the pattern of remedy selection. For example, EPA
tried to discern whether mobility of metals or the presence of ground-water contamination affected the pattern of
remedy selection and led to explanatory patterns of remedy selection. If factors strongly suggest a preference for a
specific remedy, EPA intended to incorporate this information into this guidance on how to obtain the maximum
benefits from this presumptive remedy.
Frequency of Technology Selection for Metals Sites
Exhibit A-l presents the distribution of remedial technologies selected at the 51 metals-in-soil sites evaluated.
It demonstrates that the three presumptive technologies were selected more often (39 out of the 51 sites, or
approximately 80% of the time) than the other applicable technologies. Immobilization was the remedy selected
more often than any other technology (17 of the 51 sites, or approximately 33% of the time). Exhibit A-l also
summarizes how a variety of factors (e.g., site characteristics, contaminant characteristics, risk exposure pathways,
volume of materials, land use) affected, if at all, selection of technologies. These factors may provide site managers
and other users with important information about the characteristics that have historically led to using the techniques
indicated as part of the presumptive remedy.
Exhibit A-2 summarizes the results of the screening analysis for all technologies considered for the 51 metals-in-soil
sites studied. It shows the number of times a technology passed screening in the feasibility study (i.e., was
considered in more detail in the detailed analysis of alternatives), the number of times it was screened out, and the
reason given for the screening out. Exhibit A-3 provides a similar summary for the detailed analysis of alternatives
phase.
Exhibit A-4 summarizes the characteristics of each of the technologies not selected as the presumptive remedy
against the seven Detailed Analysis criteria. This table provides site managers with part of the rationale necessary
to eliminate these technologies from further consideration.
Review of Technical Literature. Substantial literature exists on the characteristics of metals in soil and the
technologies that are effective in remediating these contaminants in accordance with Superfund statutory and
regulatory concepts. EPA relied significantly on this literature for two purposes in this analysis:
* To identify the key characteristics of metals that affect remediation, both to ensure that they were evaluated
during the presumptive remedy process as well as to supplement and support the pattern of remedy
selection that was identified; and
* To identify specific circumstances under which technologies have been successful in remediating different
metals-in-soil problems.
EPA reviewed the relevant work of the Office of Research and Development (ORD) and other offices and agencies
to ensure that the presumptive remedy developed was consistent with policy considerations and the technical
advantages and limitations identified through past applications and scientific research. In general, the technical
literature supports the presumptive technologies selected and indicates the types of site-specific circumstances that
exist when presumptive technologies both are and are not appropriate. In some cases, the literature also identified
emerging trends in metals-in-soil remediation that were incorporated into this directive.
A-2
-------
Appendix B evaluates the selected presumptive technologies against the appropriate NCP criteria. Appendices C
and D summarize the findings of the technical literature. Appendix E summarizes the data requirements generally
needed to select the technologies included as part of the presumptive remedy.
Review of EPA policies. EPA has established policies and made technical and regulatory decisions under
Superfund and other programs that affect the selection of a presumptive remedy for metals-in-soil contamination.
For example, EPA has established which technologies under the RCRA land disposal restrictions (LDR) program
are the best demonstrated available technologies (BDAT) and, therefore, are the basis for setting treatment
standards. These policies have important impacts for metals such as mercury and arsenic, for which BDAT is
generally not the solidification and stabilization approach typically applicable and most commonly used for other
metals when treatment is selected.
A-3
-------
EXHIBIT A-1: REMEDIES SELECTED AND SITE CHARACTERISTICS AT METALS SITES
(51 SITES EVALUATED FOR METALS-IN-SOILS SITES)
Site or
Contamination
Problem
Characteristic
All Sites (51)
Anionic metal
drives remedy
selection (12)
Cationic metal
drives remedy
selection (21)
Organics present
(30)
Organics NOT
present (21)
Contaminants
Migrating to
Groundwater (25)
Contaminants
NOT Migrating to
Groundwater (26)
Remedy Selected (percentage of sites)
Recovery
16% (8)
25% (3)
24% (5)
13% (4)
24% (5)
16% (4)
19% (5)
Immobilization
33% (17)
34% (4)
29% (6)
43% (13)
19% (4)
32% (8)
34% (9)
Containment
29% (15)
25% (3)
19% (4)
17% (5)
38% (8)
24% (6)
27% (7)
Presumptive
Remedy
Technologies
78% (40)
84% (10)
72% (15)
73% (22)
81% (17)
72% (18)
80% (21)
Institutional
Controls Only
6% (3)
0
9% (2)
10% (3)
0
8% (2)
4% (1)
Other On-site
Treatment
4% (2)
8%(1)
5% (1)
4% (1)
5% (1)
4% (1)
4% (1)
Off-site
Disposal
14% (7)
8% (1)
14% (3)
13% (4)
14% (3)
16% (4)
12% (3)
A-4
-------
EXHIBIT A-1: REMEDIES SELECTED AND SITE CHARACTERISTICS AT METALS SITES
(51 SITES EVALUATED FOR METALS-IN-SOILS SITES)
(continued)
Site or
Contamination
Problem
Characteristic
All Sites (51)
Contaminants
Migrating to
Groundwater,
Current or Future
Anticipated Use
(17)
Contaminants
Migrating to
Groundwater,
Anionic metal
drives remedy
selection (7)
Contaminants
Migrating to
Groundwater,
Cationic metal
drives remedy
selection (8)
Direct Contact
Pathway (45)
Remedy Selected (percentage of sites)
Recovery
16% (8)
18% (3)
14% (1)
25% (2)
18% (8)
Immobilization
33% (17)
35% (6)
29% (2)
38% (3)
35% (16)
Containment
29% (15)
18% (3)
29% (2)
0
27% (12)
Presumptive
Remedy
Technologies
78% (40)
71% (12)
72% (5)
63% (5)
80% (36)
Institutional
Controls Only
6% (3)
0
0
25% (2)
7% (3)
Other On-site
Treatment
4% (2)
6% (1)
14% (1)
0
0
Off-site
Disposal
14% (7)
23% (4)
14% (1)
12% (1)
13% (6)
A-5
-------
EXHIBIT A-1: REMEDIES SELECTED AND SITE CHARACTERISTICS AT METALS SITES
(51 SITES EVALUATED FOR METALS-IN-SOILS SITES)
(continued)
Site or
Contamination
Problem
Characteristic
All Sites (51)
NO Direct
Contact Pathway
(6)
Direct Contact
Pathway, Anionic
Metal Drives
Remedy Selection
(11)
Direct Contact
Pathway, Cationic
Metal Drives
Remedy Selection
(18)
Inhalation
Pathway (16)
Inhalation
Pathway, anionic
metals present
(13)
Remedy Selected (percentage of sites)
Recovery
16% (8)
17% (1)
27% (3)
22% (4)
19% (3)
23% (3)
Immobilization
33% (17)
17% (1)
37% (4)
28% (5)
19% (3)
23% (3)
Containment
29% (15)
17% (1)
27% (3)
22% (4)
43% (7)
39% (5)
Presumptive
Remedy
Technologies
78% (40)
51% (3)
91% (10)
72% (13)
81% (13)
85% (11)
Institutional
Controls Only
6% (3)
0
0
11% (2)
0
0
Other On-site
Treatment
4% (2)
33% (2)
0
0
0
0
Off-site
Disposal
14% (7)
16% (1)
9% (1)
17% (3)
19% (3)
15% (2)
A-6
-------
EXHIBIT A-1: REMEDIES SELECTED AND SITE CHARACTERISTICS AT METALS SITES
(51 SITES EVALUATED FOR METALS-IN-SOILS SITES)
(continued)
Site or
Contamination
Problem
Characteristic
All Sites (51)
Volume to be
treated <200,000
cy (42)
Volume to be
treated >200,000
cy(8)
Residential land
use scenario
assumed for risk
assessment (29)
Non-residential
land use scenario
assumed for risk
assessment (19)
Remedy Selected (percentage of sites)
Recovery
16% (8)
19% (8)
13% (1)
17% (5)
21% (4)
Immobilization
33% (17)
33% (14)
25% (2)
31% (9)
37% (7)
Containment
29% (15)
22% (9)
50% (4)
28% (8)
21% (4)
Presumptive
Remedy
Technologies
78% (40)
74% (31)
88% (7)
76% (22)
79% (15)
Institutional
Controls Only
6% (3)
7% (3)
0
7% (2)
5% (1)
Other On-site
Treatment
4% (2)
5% (2)
0
3% (1)
5% (1)
Off-site
Disposal
14% (7)
14% (6)
12% (1)
14% (4)
11% (2)
A-7
-------
EXHIBIT A-2: SUMMARY OF INITIAL SCREENING PHASE AGAINST NCR SCREENING CRITERIA FOR METALS-IN-SOILS SITES
Technology
#FSs
Technology
Passed
Screening
#FSs
Technology
Screened Out
REASON FOR REJECTION DURING PRELIMINARY SCREENING
Cost
Effectiveness
Implementability
Recovery
Leaching
Lead recovery '
Metallurgical Treatment
Hydrometallurgical
Treatment
o
J
7
0
2
5
0
1
o
J
1
0
1
0
o
6
0
0
i
1
0
0
2
Immobilization
Solidification/stabilization
32
7
1
i
5
Containment
Capping
Barrier Walls
32
0
5
o
6
1
0
i
i
3
2
No Action
No Action
51
0
0
0
0
The numbers for this technology include one ROD specifying a reclamation facility as the means for recovery.
A-8
-------
EXHIBIT A-2: SUMMARY OF INITIAL SCREENING PHASE AGAINST NCR SCREENING CRITERIA FOR METALS-IN-SOILS SITES (continued)
Technology
#FSs
Technology
Passed
Screening
#FSs
Technology
Screened Out
REASON FOR REJECTION DURING PRELIMINARY SCREENING
Cost
Effectiveness
Implementability
Institutional Controls
Institutional controls
9
3
0
3
0
Other Treatment
Excavation & Off-site
Disposal2
Neutralization
Soil washing/ flushing
Vitrification
15
2
5
3
3
2
11
14
2
0
0
1
0
2
5
4
1
0
6
9
Excavation and off-site disposal would most likely include treatment, but specific treatment(s) were not identified in ROD.
A-9
-------
EXHIBIT A-3: SUMMARY OF DETAILED ANALYSIS PHASE AGAINST NCR CRITERIA FOR METALS-IN-SOILS SITES
Technology
#FSs
Technology
Passed
Screening
#RODs
Technology
Rejected
REASON FOR REJECTION DURING DETAILED ANALYSIS
Overall
Protection
Compliance
with
ARARs
Reduction
of Toxicity
Mobility
Volume
Long-term
Effectiveness
Short-term
Effectiveness
Cost
Implementability
Recovery
Leaching
Lead recovery 3
Metallurgical
Treatment
Hydrometallurgical
Treatment
o
J
1
0
2
3
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
2
0
0
1
Immobilization
Solidification/
Stabilization
32
15
0
1
2
1
2
5
4
Containment
Capping
Barrier Walls
32
0
17
0
2
0
1
0
4
0
6
0
1
0
1
0
2
0
The numbers for this technology include one ROD specifying a reclamation facility as the means for recovery.
A-10
-------
EXHIBIT A-3: SUMMARY OF DETAILED ANALYSIS PHASE AGAINST NCR CRITERIA FOR METALS-IN-SOILS SITES
(continued)
Technology
#FSs
Technology
Passed
Screening
#RODs
Technology
Rejected
REASON FOR REJECTION DURING DETAILED ANALYSIS
Overall
Protection
Compliance
with
ARARs
Reduction
of Toxicity
Mobility
Volume
Long-term
Effectiveness
Short-term
Effectiveness
Cost
Implementability
No Action
No Action
51
51
21
17
3
9
1
0
0
Institutional Controls
Institutional
Controls
9
6
2
2
1
1
0
0
0
Other Treatment
Excavation & Off-
Site Disposal4
Neutralization
Soil washing/
flushing
Vitrification
15
2
5
o
J
9
1
4
3
0
0
0
0
1
0
0
0
2
0
0
0
0
0
0
1
0
0
1
0
4
1
1
0
2
0
2
2
Excavation and off-site disposal would most likely include treatment, but specific treatment(s) were not identified in ROD.
A-ll
-------
EXHIBIT A-4: EVALUATION OF NON-PRESUMPTIVE REMEDY TECHNOLOGIES
AGAINST SEVEN NCP DETAILED ANALYSIS CRITERIA:1
EXCAVATION AND OFF-SITE REMOVAL OF WASTES FOR APPROPRIATE DISPOSAL
CRITERIA
Overall
Protection of
Human Health
and the
Environment
Protectiveness
achieved by offsite
removal and proper
disposal of
contaminated soil
(e.g., RCRA
disposal of
hazardous
materials)
Compliance
with ARARs
If RCRA waste,
requires
compliance with
RCRA
transportation and
land disposal
restrictions
Long-Term
Effectiveness
High long-term
effectiveness for
site; protective-
ness at disposal
site dependent
on offsite
management
choices
Reduction of
Toxicity,
Mobility, or
Volume
Through
Treatment
Disposal reduces
mobility;
reduction of
toxicity and
volume depends
on offsite
management
choices
Short-Term
Effectiveness
Requires
standard
precautions
necessary to
protect worker
and resident
safety and
environment
Special measures
may be required
to protect
residents during
transportation
Implementability
Easily implementable
given facility with
adequate capacity for
waste type, located
within reasonable
distance of site
Uses standard
construction equipment
and labor
Cost2
Reasonable for small
to medium volumes
of contaminated soil
May be cost-
prohibitive for large
volumes
Bold denotes major reasons, in terms of frequency cited in Feasibility Study Analysis Report, the remedy does not meet NCP criteria.
Actual cost of a remediation technology is highly site-specific and dependent upon target cleanup levels of contaminants, soil characteristics, and the design and operation
of the remediation technology used.
A-12
-------
EXHIBIT A-4: EVALUATION OF NON-PRESUMPTIVE REMEDY TECHNOLOGIES
AGAINST SEVEN NCP DETAILED ANALYSIS CRITERIA:1
(continued)
SOIL WASHING/FLUSHING
CRITERIA
Overall
Protection of
Human Health
and the
Environment
Highly effective if
high removal
efficiencies are
attained
Washing fluid
which contains
high metal
concentrations
must be treated to
achieve complete
protection
Compliance
with ARARs
Excavation (soil
washing) may
activate action-
specific
ARARs
Must ensure
that washing
solution into
soil (flushing)
complies with
any chemical-
or location-
specific
ARARs
Long-Term
Effective-
ness and
Permanence
When metals
successfully
removed from
soil, eliminates
risk associated
with contact
with soils and
contaminant
migration off
site
Provides
permanent
solution
Reduction
of
Toxicity,
Mobility,
or Volume
Through
Treatment
Permanently
reduces
toxicity and
mobility by
removing
metals
Soil washing
concentrates
contaminants
into much
smaller
volume
Process
must include
proper
treatment of
washing
fluids
Short-Term
Effectiveness
Injection of the
washing solution
into soil (flushing)
may be harmful to
human health
and/or the
environment if
washing
fluids/vapors are
not collected and
treated properly
Washing requires
standard
precautions
necessary to protect
worker and
resident safety and
environment during
excavation and
treatment
Implementability
Applicable to relatively
narrow range of soil
types and contaminant
combinations:
- Soil with high
percentage of small
particles (clay, silt, fines)
difficult to treat
- Most extraction
solutions effective only
for narrow range of
metals and matrix
combination
High removal efficiencies
can be difficult to achieve
or require complex
process
Requires standard
equipment and labor
Cost2
Potential to
remove
marketable
metals
removed in
sufficiently
high
concentratio
nsmay
partially
offset
treatment
costs
Bold denotes major reasons, in terms of frequency cited in Feasibility Study Analysis Report, the remedy does not meet NCP criteria.
Actual cost of a remediation technology is highly site-specific and dependent upon target cleanup levels of contaminants, soil characteristics, and the design and operation
of the remediation technology used.
A-13
-------
EXHIBIT A-4: EVALUATION OF NON-PRESUMPTIVE REMEDY TECHNOLOGIES
AGAINST SEVEN DETAILED ANALYSIS CRITERIA:1
(continued)
VITRIFICATION
CRITERIA
Overall
Protection of
Human Health
and the
Environment
Highly effective if
successfully
implemented
Products have
potential reuse
options
Compliance
with ARARs
Generally
activates
action-specific
ARARs
Generation of
offgas likely to
trigger
chemical-
specific
ARARs
Long-Term
Effectiveness
and
Permanence
If successfully
implemented,
results in inert
solid with low
leachability
Incorporation of
metals into
vitrified mass
significantly
reduces risk
associated with
contaminated soil
and potential for
offsite migration
Limited data on
long-term
effectiveness
Reduction of
Toxicity,
Mobility, or
Volume
Through
Treatment
Immobilizes
metals reducing
toxicity and
mobility
Generally
reduces volume
Some metals
must be
converted to
less volatile
form prior to
treatment to
prevent release
Short-Term
Effectiveness
Tends to generate
significant amounts
of offgas which may
be harmful to human
health and the
environment; may
require extensive
controls, including:
respiratory
protection, fugitive
dust control
procedures, and air
monitoring
Implementability
Limited commercial availability
Significant offgas production may
preclude implementation due to
community concern, ARARs;
permits for operation may be
difficult to obtain
Requires substantial energy
source
Extensive pilot scale testing
required
Labor intensive; requires highly
skilled personnel, facilities, and
equipment
Presence of other constituents may
impede effective implementation
Cost2
High cost
and energy
intensive;
often cost-
prohibitive
Bold denotes major reasons, in terms of frequency cited in Feasibility Study Analysis Report, remedy does not meet NCP criteria.
Actual cost of a remediation technology is highly site-specific and dependent upon target cleanup levels of contaminants, soil characteristics, and
the design and operation of the remediation technology used.
A-14
-------
EXHIBIT A-4: EVALUATION OF NON-PRESUMPTIVE REMEDY TECHNOLOGIES
AGAINST SEVEN NCP DETAILED ANALYSIS CRITERIA:1
(continued)
INSTITUTIONAL CONTROLS
CRITERIA
Overall Protection of
Human Health and the
Environment
May reduce potential
exposure of receptors by
restricting access and
future land use
Does not reduce certain
contaminant migration
pathways offsite such as
leaching to groundwater,
fugitive dust, surface
runoff
Compliance
with ARARs
May not comply
with federal and
state ARARs
Long-Term
Effectiveness
and
Permanence
Provides some
level of protection
over No Action
Does not
permanently
address
contamination
problem therefore
long-term
effectiveness is
uncertain
Reduction of
Toxicity, Mobility, or
Volume Through
Treatment
Not considered a
treatment remedy.
Short-Term
Effectiveness
Does not create any
potential risks to
human health or the
environment during
implementation
Implementability
Easily implemented
Cost2
Typically the
lowest cost
remediation
alternative
Bold denotes major reasons, in terms of frequency cited in Feasibility Study Analysis Report, the remedy does not meet NCP criteria.
2
Actual cost of a remediation technology is highly site-specific and dependent upon target cleanup levels of contaminants, soil characteristics, and the design and operation
of the remediation technology used.
A-15
-------
APPENDIX B
EVALUATION OF SELECTION CRITERIA FOR TECHNOLOGIES USED TO TREAT CONTAMINATED
SOILS AND RELATED MEDIA AT METALS-IN-SOIL SITES
RECOVERY
CRITERIA
Overall Protection
of Human Health
and the
Environment
Protectiveness and
permanent solution
achieved by removing
contaminants from
soil; also converts
metals to useful form
Compliance with
ARARs
Removing metal
contaminants from
waste eliminates
need to comply with
land disposal
restrictions for
metals only
Action- specific
ARARs may be
activated by use of
treatment processes
Compliance with
ARARs is often met
by further waste
management
Long-Term
Effectiveness
Very high if
contaminants
successfully
removed from
soil; risks
associated with
soil are
permanently
eliminated or
greatly reduced;
no continued site
monitoring
required to ensure
effectiveness
Reduction of
Toxicity, Mobility,
or Volume
Through
Treatment
Permanently removes
majority of
contaminants
thereby reducing
toxicity, mobility,
volume; any
remaining metals
immobilized in slag or
residue
Short-Term
Effectiveness
Requires standard
precautions
necessary to
protect worker and
resident safety and
environment
Thermal air
emissions may
require treatment
Implementability
Based on current
knowledge, several
metals in various forms
can be successfully
recovered from soils;
however, pilot testing
may be required
Commercial smelting
facilities may not have
permits for hazardous
waste; requires
specialized facilities
and highly trained labor
Cost1
Production of
potentially
marketable
materials
potentially
mitigates costs
associated with
treatment;
depends on metal
concentration,
marketability of
metal, and the
form of metal in
waste
Actual cost of a remediation technology is highly site-specific and dependent upon target cleanup levels of contaminants, soils characteristics, and the design and operation
of the remediation technology used.
B-l
-------
APPENDIX B
EVALUATION OF SELECTION CRITERIA FOR TECHNOLOGIES USED TO TREAT CONTAMINATED
SOILS AND RELATED MEDIA AT METALS-IN-SOIL SITES
(continued)
IMMOBILIZATION
CRITERIA
Overall Protection
of Human Health
and the
Environment
Protectiveness
achieved by reducing
ability of
contaminant to
migrate
Compliance
with ARARs
Excavation,
construction, and
operation of on-site
treatment unit may
require compliance
with location- and/or
action-specific
ARARs
Can immobilize
metals such that
TCLP standards are
met, eliminating need
to dispose of as
hazardous waste
Long-Term
Effectiveness
May require
maintenance to
ensure durability
and continued
leach-resistance of
treated material
Data on long-term
effectiveness
limited
Reduction of
Toxicity, Mobility,
or Volume Through
Treatment
Immobilizes
contaminants, but
does not reduce
toxicity; may increase
volume
Short-Term
Effectiveness
Requires
standard
precautions
necessary to
protect
worker and
resident safety
and
environment
May pose
some short
term risks if
ex-situ
treatment is
performed
Implementability
Widely implemented
and reliable
Commercially
available,
demonstrated
technology;
extensive vendor
capacity
Cost1
Generally, lowest
cost treatment
alternative
because of
extensive
commercial
availability and
demonstrated
status
Actual cost of a remediation technology is highly site-specific and dependent upon target cleanup levels of contaminants, soil characteristics, and the design and operation
of the remediation technology used.
B-2
-------
APPENDIX B
EVALUATION OF SELECTION CRITERIA FOR TECHNOLOGIES USED TO TREAT CONTAMINATED
SOILS AND RELATED MEDIA AT METALS-IN-SOIL SITES
O(continued)
CONTAINMENT OF METALS IN SOIL IN PLACE
CRITERIA
Overall Protection
of Human Health
and the
Environment
Contaminated
material remains
onsite but risk of
exposure to public
significantly reduced
through engineered
barriers
Environment is
protected by
minimizing migration
of contaminants and
likelihood of direct
exposure
Compliance
with ARARs
Hazardous waste
disposal will require
compliance with
ARARs
Long-Term
Effectiveness
Long-term
protection can be
ensured through
continued
maintenance
Reduces
contaminant
release rates, but
not considered a
treatment remedy
for principal threat
wastes
Reduction of
Toxicity, Mobility,
or Volume
Through
Treatment
Not considered a
treatment remedy.
Short-Term
Effectiveness
Requires
standard
precautions
necessary to
protect
worker and
resident safety
and
environment
Implement ability
Commercially
available,
demonstrated
technology.
Necessary materials
easily attainable.
Uses standard
construction
equipment and labor
Cost1
Generally less
expensive than
most forms of
treatment
Actual cost of remediation technology is highly site-specific and dependent upon target cleanup levels of contaminants, soil characteristics, and the design and operation
of the remediation technology used.
B-3
-------
APPENDIX C
SUMMARY OF METAL CONTAMINANTS COMMONLY FOUND AT SUPERFUND SITES1
Metal
Physical/Chemical
Characteristics (including
common forms)
Mobility, migration information
Proven Treatment and Technology
(including BDAT)
Arsenic (As)
a semi-metallic element or
metalloid which has several
allotropic forms
commonly found at metal
contaminated sites: As2O3 and As
species which have leached from
As2O3 oxide to As(V) and then
sorbed onto Fe-bearing minerals in
soil
As(V) exhibits anionic behavior in
presence of water; may form
insoluble metal arsenates
As(V) less mobile and toxic than
As(III)
solubility of other forms, including
organometalloids depends on pH,
other soil constituents, presence of
water, etc.
leaching distance generally short
because of tendency to sorb onto soils
and sediments; however soluble forms
move easily with water and may be
carried long distances via rivers
tendency to adsorb onto soils and
sediments increases when clays, iron
oxides, aluminum hydroxides,
manganese compounds, and organic
materials are present
therefore, leaching tendency is higher
when levels of these minerals are low
presence of ions and organic
compounds can increase mobility
because of competitive sorption and
formation of organoarsenic
complexes
BDAT is vitrification
Possible to recover, for sale, through incineration or other thermal processes; not
sufficiently economically attractive to be generally available
Implementation of Solidification/Stabilization
EPA does not preclude use of S/S for treatment of As but recommends its use be
determined on site by site basis
long-term stability is questionable and volume increase may be unacceptable
Oxidation of As(III) to As (V) improves effectiveness of this technology; however,
effectiveness may still be limited because species that exist as ions difficult to
stabilize
High concentrations may increase setting time
As(III) and As(V) do not form insoluble hydroxides or carbonates; this reaction is
mechanism of immobilization for cement-based S/S; thus, this technology is not
applicable to As
'The majority of the information in this table was obtained from Contaminants andRemedial Options at Selected Metal-Contaminated Sites, Office of Research and Development (ORD), U.S. EPA,
EPA/540/R-95/512, July 1995. This table summarizes the information and does not provide the level of description and analysis that is contained in the ORD document. Site managers employing this
presumptive remedy should refer to Contaminants andRemedial Options at Selected Metal-Contaminated Sites for more detail on the information presented in this table.
C-l
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APPENDIX C
SUMMARY OF METAL CONTAMINANTS COMMONLY FOUND AT SUPERFUND SITES
(continued)
Metal
Physical/Chemical
Characteristics (including
common forms)
Mobility, migration information
Proven Treatment and Technology
(including BOAT)
Cadmium (Cd)
exists as Cd2+ion, Cd-CN'
complexes, or Cd(OH) 2 sludge
at most metal-contaminated
sites depending on pH and
treatment that wastes receive
before disposal
at low pH occurs as Cd2+ion or
aqueous sulfate
as pH increases, Cd precipitates
to form Cd(OH)2 and CdCO3
does not form volatile
compounds
precipitation and adsorption onto
soils and sediments govern
transformation and mobility
at low pH, Cd is not generally
removed from water
at lower pH, Cd may be completely
removed from water
adsorption is a function of cation
exchange capacity of clay and
carbonate minerals, oxides and
organic matter
sulfate and chloride ions reduce
adsorption, primarily due to
competitive adsorption; ligands may
increase adsorption
BDAT for nonwastewater Cd other than batteries is
Solidification/Stabilization
BDAT for Cd-containing batteries is thermal recovery
Recovery is preferred over treatment for wastes with Cd concentrations
similar to concentrations in batteries; specific concentration level was not
established
Implementation of Solidification/Stabilization
Particularly effective if Cd is only contaminant
C-2
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APPENDIX C
SUMMARY OF METAL CONTAMINANTS COMMONLY FOUND AT SUPERFUND SITES
(continued)
Metal
Physical/Chemical
Characteristics (including
common forms)
Mobility, migration information
Proven Treatment and Technology
(including BOAT)
Chromium (Cr)
most common forms are Cr(VI)
and Cr(III)
valence is dependent on pH and
redox potential
Cr(VI) exists in more oxidized
soils and sediments
Cr(VI) is highly toxic, soluble,
and mobile in soils; Cr(III) is
significantly less toxic, soluble,
and mobile
Cr(VI) precipitates with metal
cations and soils surfaces with
positively charged sites
Cr(VI) is reduced to Cr(III) in
presence of organic matter and
Fe(II) minerals; rate of reaction
increases with decreasing soil pH
in most soils and sediments Cr
will eventually be present as
Cr(III)
Cr(III) may oxidize to Cr(VI) in
presence of MnO2
mobility depends on sorption
characteristics of soil; depends on
content of clay, Fe2O3, and organic
matter
adsorption of Cr(VI) occurs only at
an acidic or neutral pH
Cr(III) tends to adsorb onto clays
below pH 4; formation of complexes
with soluble organic matter increases
Cr(III) mobility in soils
surface runoff can transport both
soluble and bulk precipitates to
surface water
soluble and unabsorbed Cr(VI) and
Cr(III) complexes in soil will leach
into groundwater
leachability of Cr(VI) increases as soil
pH increases; conversely lower pH of
acid rain may enhance leaching of
acid-soluble Cr compounds in soil
Cr transported through water
generally deposited in sediment
BDAT is Solidification/Stabilization
Implementation of Solidification/Stabilization
BDAT includes reduction of Cr (VI) to Cr (III) prior to S/S; Cr(III) is readily
precipitated by hydroxide over a wide pH range
acidification followed by reduction and neutralization is common approach
to Cr(VI) reduction; chemical treatments available for Cr reduction in neutral
pH ranges; Note: injection of treatment chemicals may create requirement
for land disposal
C-3
-------
APPENDIX C
SUMMARY OF METAL CONTAMINANTS COMMONLY FOUND AT SUPERFUND SITES
(continued)
Metal
Physical/Chemical
Characteristics (including
common forms)
Mobility, migration information
Proven Treatment and Technology
(including BOAT)
Lead(Pb)
most of Pb released in form of
metal, oxides, hydroxides, oxy-
anion complexes
most common oxidation forms
are Pb(0) and Pb(II); Pb(II) is
most stable species under most
conditions
Pb also forms stable complexes
with organic and inorganic
ligands present in soil
reacts with carbonates, sulfides,
sulfates, and phosphates to form
low-solubility compounds
most Pb retained strongly in soil ion
exchange, precipitation, or
sorption/complexation to organic
matter; depending on pH may form
organic- or hydrous Pb oxide- lead
complexes or Pb carbonate or
phosphate precipitates; in these
forms, very little transported to
surface or ground water
at pH of 4-6, organic Pb complexes
become more soluble and may leach
at surface Pb may be converted to Pb
sulfate which is relatively more
soluble than Pb forms found beneath
surface
BDAT for non wastewater other than battery waste and explosive
compounds is Solidification/Stabilization; BDAT for organolead wastes is
incineration and stabilization of ash if needed
BDAT for wastes from lead-acid battery recycling is thermal recovery in
secondary Pb smelter
Recovery appropriate for Pb non wastewater with concentrations up to
50,000 mg/kg of Pb; research indicates concentration must be >25% Pb for
recovery to be economically viable
Implementation of Solidification/Stabilization
treated waste is subject to leaching and solubilization if pH is not carefully
controlled; this may occur evenly at mildly acidic conditions
Particularly effective if Pb is only contaminant
C-4
-------
APPENDIX C
SUMMARY OF METAL CONTAMINANTS COMMONLY FOUND AT SUPERFUND SITES
(continued)
Metal
Physical/Chemical
Characteristics (including
common forms)
Mobility, migration information
Proven Treatment and Technology
(including BOAT)
Mercury (Hg)
exists in mercuric, mercurous,
elemental or alkylated forms
form is dependent on redox
potential and pH of soil
in soil, exists primarily in
mercuric and mercurous forms as
a number of complexes with
varying water solubilities
alkylated forms are most toxic
and are volatile and soluble in
water
under mildly reducing
conditions, organically bound
and inorganic compound may be
degraded readily to alkylated
form
volatile forms evaporate to
atmosphere; solid forms partition to
particulate
tendency of Hg to sorb with soil and
sediment increases with pH; generally
sorbs strongly to organic materials
leaching is a relatively insignificant
transport process in soils; but surface
runoff may remove Hg from soil to
water, particularly for soils with high
humic content
depending on pH, salt content, and
composition of soil solution, mercury
forms various complexes with
chloride and hydroxide ions in soil
some forms also immobilized in soils
and sediments by forming precipitates
with carbonate, phosphate, sulfate,
and sulfide
BDAT for Hg >260 mg/kg is thermal recovery including roasting or retorting
(thermal processes which sublimate Hg from waste and capture metal for
refining prior to reuse); pyrolysis and infrared thermal destruction also
identified as appropriate thermal recovery process
BDAT for inorganic Hg non wastewater below thermal recovery limit (<260
mg/kg) is acid leaching followed by chemical precipitation and dewatering
high volatility makes thermal recovery feasible at relatively low
concentrations relative to other metals
Implementation of Solidification/Stabilization
difficult to stabilize because Hg does not have low-solubility hydroxide;
effectiveness particularly limited when present at high concentration or in
elemental form
in low concentrations, Hg can be stabilized to meet leachability requirements
for land disposal
C-5
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APPENDIX D
SUMMARY OF REMEDIATION TECHNOLOGIES APPLICABLE TO METALS-IN-SOILS CONTAMINATION
Technology
Description of Technology
Benefits/Limitations of Technology
Factors Influencing Effectiveness, Implementability, and
Cost-Effectiveness
Containment
(includes
capping, vertical
and horizontal
barriers)
Result: provides sustained isolation of
contaminants and prevents
mobilization of soluble compounds
over a long period
Processes:
Cap, cover:
design usually conforms to RCRA
landfill closure requirements; however
this may not be necessary in areas
where precipitation is low, capped
waste is not leached by precipitating
water, or risk is due to dust generation
or direct contact; often includes
regrading, revegetation
Vertical Barriers:
includes slurry walls, grout curtains,
sheet pile walls
to be effective, must extend and key to
impervious layer beneath
contaminated area (e.g., bedrock or
competent aquitard)
Horizontal Barriers'.
an emerging technology, not yet
demonstrated at any site; "lines"
contaminated site by placing physical
barrier beneath contaminated area or
making underlying soil less permeable;
objective is to prevent downward
migration of contaminants (because of
limited data will not be further
addressed in this table)
Benefits
considered proven technology for site
remediation; readily available; relatively
inexpensive
addresses contaminated soil where remedial
treatments not appropriate (because of cost, risk,
or implementation issues)
reduces surface and/or ground water infiltration,
direct contact, and dust generation; improves
aesthetics and provides stable surface over waste
may be used for wastes that contain mixtures or
concentrations of metals which impede
effectiveness or preclude implementation of other
technologies
Limitations
Does not involve treatment or provide permanent
solution; does not reduce toxicity or volume
Requires long-term maintenance and monitoring
Restricts site from certain future uses
Once in place, may hinder future treatment
Extent of contamination- capping may be more protective and
cost-effective for areas of shallow, wide-spread contamination
Depth to groundwater- capping may not be effective for sites
with high groundwater table or located on floodplain
Climate- type of cap needed partially dependent on rain and
snow fall
Site topography, geology- generally better suited to level areas
(particularly pertinent to vertical barriers); type of cap needed
partially dependent on amount of surface run-on and run-off;
depth to continuous impermeable strata or competent bedrock
needed for design of slurry wall
Presence of Other Constituents- slurry wall may be degraded by
strong acids or bases, sulfates, and strong electrolyte solutions
D-l
-------
APPENDIX D
SUMMARY OF REMEDIATION TECHNOLOGIES APPLICABLE TO METALS-IN-SOIL CONTAMINATION
(continued)
Technology
Description of Technology
Benefits/Limitations of Technology
Factors Influencing Effectiveness, Implementability, and
Cost-Effectiveness
Immobilization
Result:
Physically locks waste constituents
within solidified matrix (solidification)
and/or converts waste constituents to
more immobile form, usually by
chemical reaction (stabilization)
Process:
Involves mixing reagent with waste
matrix; reagents selected based on
medium and waste constituents;
reagents include cement, fly ash, blast
furnace slag and organic materials such
as bitumen
Can be done either in situ or ex situ
Mixing techniques for in situ include:
- in place mixing
- vertical auger mixing
- injection grouting
Effectiveness dependent on ability to
uniformly and thoroughly mix reagent
with waste
Mechanism:
Mobility is reduced by formation of
insoluble hydroxides, carbonates or
silicates; substitution of metal into
mineral structure; sorption; or physical
encapsulation
General
Benefits
Reduces mobility of metal contaminants;
improves waste handling and other physical
characteristics
Commercially available, established technology;
many vendors available at competitive prices
Limitations
Increases volume; percentage increase dependent
on amount of reagent used as needed to
immobilize contaminants
Ex situ
Benefits
Allows for screening and crushing of large
materials prior to treatment which may be
necessary to ensure proper mixing
Limitations
Excavation increases energy and labor costs;
difficult to implement at small sites
In situ
Benefits
Eliminates labor and energy expenses associated
with excavation, transport, replacement or
disposal of waste
Enables small sites that do not have space for
material stockpiling and treatment to realize cost
savings and satisfy SARA's preference for onsite
treatment
Limitations
Not applicable for deep contamination
General
Metal Contaminants Present- metal and species of metal
determines behavior and reaction of metal; more effective for
particular oxidation states of As, Cr; if single metal is present,
Pb and Cd most amenable to treatment
Multiple contaminants- may be difficult to identify reagent that
simultaneously reduces mobility of all contaminants
Presence oforganics- <20-45 percent by weight; may interfere
with bonding of wastes with binders; VOCs may vaporize during
process; if present in high concentrations must be addressed
prior to treatment; S/S can be used for wastes that contain low
levels oforganics; addition of silicates or modified clays may
improve performance with organics
Particle size-limited amount of insoluble particulate passing
through a 200 mesh screen; fine particles delays setting, weakens
bonds
pH- 9.0-11.5; required for setting and to minimize metal
solubility; pH level must be maintained to ensure continued
immobilization
Presence of Other Constituents- a range of constituents may
inhibit proper bonding of reagent with waste, retard setting of
treated material and/or reduce durability, compressive strength,
and leach resistance of final product; these include oil, grease,
phenol, soluble salts of some metals, cyanide, sulfate
In situ
Depth of contamination- Process is demonstrated at depths up to
30' and may be applicable up to 150'
Subsurface geology- presence of subsurface barriers, debris,
boulders impedes delivery of reagent to contaminated soil and
complete and uniform mixing of reagent with waste
Composition of soil- presence of clay, oily sands, cohesive soils
may impede effectiveness; these can be separated if treated ex
situ
D-2
-------
APPENDIX D
SUMMARY OF REMEDIATION TECHNOLOGIES APPLICABLE TO METALS-IN-SOIL CONTAMINATION
(continued)
Technology
Description of Technology
Benefits/Limitations of Technology
Factors Influencing Effectiveness, Implementability, and
Cost-Effectiveness
Soil Washing Result: extraction of contaminant
from solid matrix that lowers metal
concentrations to specified levels
Process: may involve one or both of
following stages:
-physical separation of soil
particle size fractions
-use of washing solution to
remove contaminants
treatments that combine both
techniques are most effective;
contaminants tend to sorb to smaller
particles; by removing particle size
fraction of soil which is not associated
with contaminant, physical separation
reduces volume needing treatment
washed soil may be returned to site or
reclaimed; small particle size fraction
or wash residuals are generally highly
contaminated and must be properly
disposed of
Mechanism: physical separation scours
and separates silts and clays from clean
sand and gravel particles; wash solution
transfers metal from matrix into
solution or converts it into compound
that can be separated from matrix
Benefits
Removes metal contaminants from soil; thereby
reducing toxicity, mobility, and volume of waste
and providing permanent treatment
Extraction fluid may be processed to recover
metals with market value
If metal concentration is low, this process
provides less costly method to recover potentially
valuable metals
Limitations
Extraction fluids generally specific to limited
range of chemical forms of metal; one treatment
usually only effective for a narrow range of
contaminant and matrix combinations
Not extensively demonstrated at metals-in-soil
sites
Extraction fluid necessary to remove metals may
have toxic characteristics and may have
undesirable side reactions when mixed with
contaminants present
Particle size-
>2mm: presence of large clumps or debris interferes
with good contact between washing solution and soil;
pretreatment needed to remove or crush oversize
material
0.25-2mm: effective; 0.063-0.25: effectiveness
limited; <0.063: clay and silt fraction- difficult soil
washing
Composition of soil- more effective for homogeneous material;
complex mixture increases difficulty in formulation of suitable
extraction fluid
Volume of Waste- treatment of larger volumes more cost-
effective because of economies of scale
Contaminant solubility in water- >1,000 mg/L; soluble
compounds can be removed by water flushing; decreases costs
and risks to worker safety and environment
pH- low pH more effective for acid extraction
Presence of Other Constituents- cyanides, sulfides, fluorides may
generate fumes at low pH
Conditions which enhance sorption- high CEC and humic
content enhance sorption and therefore make extraction more
difficult
D-3
-------
APPENDIX D
SUMMARY OF REMEDIATION TECHNOLOGIES APPLICABLE TO METALS-IN-SOIL CONTAMINATION
(continued)
Technology
Description of Technology
Benefits/Limitations of Technology
Factors Influencing Effectiveness, Implementability, and
Cost-Effectiveness
Soil Flushing Result: extracts metal contaminants
from soil in situ
Process: water or an aqueous solution
(chemicals in water) or organic
extractant is injected into or sprayed
onto contaminated area, contaminated
elutriated, collected, and pumped to
surface for removal, recirculation, or
onsite treatment and reinjection
subsurface contaminated barriers may
be used in conjunction with flushing to
control flow of flushing fluids
Mechanism: contaminants mobilized
by solubilization, formation of
emulsions, or chemical reaction with
flushing solutions
water will extract only water soluble or
water mobile constituents (e.g.,
carbonates of Ni, Zn, Cu)
Benefits
Removes metal contaminants from soil; thereby
reducing toxicity, mobility, and volume of waste
and providing permanent treatment
Avoids cost and implementability issues associated
with excavation
Limitations
treatment for inorganics less well developed than
for organics; limited bench- or pilot-scale testing
may not be able to identify solution necessary to
extract some metals which does not cause harm to
in situ environment and complies with LDRs and
other regulatory requirements
Metal contaminants present- flushing solution used depends on
metals present; fluids vary according to toxicity, cost, regulatory
compliance
Contaminant distribution and subsurface geology- affects ability
to deliver and recover flushing solution effectively
Hydraulic conductivity of soil- >10 "3 cm/sec and low clay
content; allows for efficient delivery of flushing fluids
Equilibrium partitioning of contaminant between soil and
extraction fluid- high partitioning decreases amount of fluid
needed to attain cleanup goals
Composition of soil- more effective for homogeneous material;
complex mixture or spatial variation in waste composition
increases difficulty in formulation of suitable extraction fluid
Contaminant solubility in water- >1,000 mg/L; soluble
compounds can be removed by water flushing; decreases costs
and risks to worker safety and environment
Presence of Other Constituents- cyanides, sulfides, fluorides may
generate fumes at low pH
Conditions which enhance absorption- high cation exchange
capacity, humic content, and surface area of matrix enhance
sorption and therefore make extraction more difficult
D-4
-------
APPENDIX D
SUMMARY OF REMEDIATION TECHNOLOGIES APPLICABLE TO METALS-IN-SOIL CONTAMINATION
(continued)
Technology
Description of Technology
Benefits/Limitations of Technology
Factors Influencing Effectiveness, Implementability, and
Cost-Effectiveness
Vitrification
Result:
Immobilizes metals into chemically
durable, leach-resistant solid; may also
be used to vaporize or destroy organic
contaminants
Processes:
can be done ex situ or in situ
ex situ-
Heat can be applied through
combustion of fossil fuels (coal, natural
gas, and oil) in melter or input of
electric energy by direct joule heating
in situ (ISV) -
heat applied through electric current
passed though soil using array of
electrodes inserted into soil
Mechanism:
Metals retained in melt during heating
and incorporated into vitrified mass
that forms as melt cools; metals
convert to oxides, silicates of other
compounds with high boiling points
Benefits
Immobilization of metals; generally decreases
volume of waste
Can simultaneously treat a wide variety of
contaminants, both organic and inorganic, in a
range of matrix types
Capable of transforming waste into useful,
recyclable products such as clean fill, erosion
control blocks, road dividers
Because most soils naturally composed of glass-
forming materials, usually processible without
additives
Most systems do not require pretreatment
Limitations
Limited current commercially available capacity
for hazardous waste vitrification
Expensive to implement; cost highly dependent
on waste, throughput capacity, local energy costs,
site location
General
Metal contaminants present- Ba, Be, Cr, Cu, Ni, Ag, Th, Zn
easily incorporated into oxide melt; more difficult to
incorporate As, Pb, Se; volatile metals (e.g., Hg, Cd) may exist
in offgas thus requiring treatment of offgas
Concentrations of metal contaminants- if concentration for a
metal exceeds its solubility in silicate, it may form crystalline
phases which can decrease leach resistance
Waste volume- as batch process, economics improve with
increased volume
Moisture content- <25% by wt. high moisture content may
require dewatering and increase energy requirement
Presence oforganics- release energy on oxidation and thereby
reduces energy requirements of process
Particle size- may need to be controlled to achieve reference
throughputs and a homogenous melt; appropriate size dependent
on melter system used
Presence of Other Constituents- sulfates and chlorides may react
to volatile metal species, which may be difficult to retain in
melt, or corrosive acids, which reduce durability
In Situ
Contaminant Depth- >6 ft and <20 ft; uncontaminated
overburden helps retain volatile metals
Surface slope- <5%; melt may flow under influence of gravity
Presence of underground structures, utilities, sealed containers-
items located <20ft must be protected from heat
Presence of groundwater- water inflow increases energy
D-5
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APPENDIX E
DATA REQUIREMENTS TO FOCUS ON TO DETERMINE POTENTIAL FOR
APPLICABILITY OF PRESUMPTIVE REMEDIES FOR METALS-IN-SOIL SITES
Reclamation/Recovery
Purpose
Reclamation/recovery technologies separate metal contaminants from soil in the form of metal, metal oxide, ceramic
product, or other useful products that have potential market value. Reclamation/recovery is consistent with EPA
national policies on pollution prevention and waste minimization. Reclamation/recovery is a permanent treatment
that removes contaminants from the soil.
Description of the Technology
The process for reclamation/recovery is usually preceded by physical separation and concentration to produce
uniform feed material and/or to upgrade metal content. This may be the primary treatment and may include
hydrometallurgical or leaching processes. Compounds in waste can also be converted to metal or matte by
transferring undesirable components to a separate slag phase. Subsequent treatment is performed to upgrade the
metal or matte. The equipment used for the process typically includes rotary kilns, hearth or arc furnaces. Volatile
metals (e.g., As, Cd, Pb) enter off-gas stream, are oxidized and then recovered by filtration or scrubbing; nonvolatile
metals (e.g., Ni, Cr) remain in a furnace and are purified by slagging. See Exhibit E-l for details about data
requirements for reclamation/recovery.
EXHIBIT E-1
DATA REQUIREMENTS TO FOCUS ON TO DETERMINE POTENTIAL FOR
APPLICABILITY OF RECLAMATION/RECOVERY
CATEGORY
Metal Contaminants
Soil Characteristics
Other Contaminants
and Constituents
Present
DATA REQUIREMENT
Metals/chemical form
Concentrations
Particle size
Volume
Moisture content
Thermal conductivity of waste
Combustibles
IMPORTANCE OF INFORMATION
Particular metals and chemical forms are more
amenable to recovery because of marketability or
ease of recovery, such as lead.
Mixtures of volatile and non- volatile metals require
complicated process
High concentrations generally necessary to make
process feasible, economically viable;
hydrometallurgical methods generally used for
wastes with low metal concentrations
Specific processes well-suited to particular particle
sizes
Processing typically operates best with continuous
feed
Presence of water increases energy requirements and
may cause material handling problems
Treatment requires ability to transfer heat into waste
matrix
May provide heating and thereby lower energy
requirements
E-l
-------
CATEGORY
Treatability Study
Testing (factors to be
evaluated during
treatability study
which influence
effectiveness)
DATA REQUIREMENT
Nitrates, sulfur compounds,
phosphates, halides
Alkaline metals
Ash content of waste
IMPORTANCE OF INFORMATION
May form corrosive acid gasses; sulfur forms
nonvolatile sulfides; halides may form volatile metal
species
Metals such as Na, K decrease slag formation
temperature and increase corrosiveness of slag
Helps quantify expected slag volume
Immobilization
Purpose
Immobilization changes the physical or chemical properties that impact the leaching characteristics of a treated waste
or decreases its bioavailability and concentration. Immobilization is designed to accomplish one or more of the
following objectives:
•Improve the physical/chemical characteristics of the waste, without necessarily reducing aqueous mobility of the
contaminant;
•Reduce the contaminant solubility;
•Decrease the exposed surface area across which mass transfer loss of contaminants may occur; or
•Limit the contact of transport fluids and contaminants.
Description of the Presumptive Remedy
This treatment locks metals within a solidified matrix (solidification) and/or converts the waste constituent into a
more immobile form, usually by chemical reaction (stabilization). The process involves mixing a reagent (usually kiln
cement dust, proprietary agents, cement, fly ash, blast furnace slag, bitumen) with the contaminated soil. Reagents
are selected based on soil characteristics and metal contaminants present. Exhibit E-2 provides details about data
requirements for immobilization. The treatment can be performed ex situ or in situ.
EXHIBIT E-2
DATA REQUIREMENTS TO FOCUS ON TO DETERMINE POTENTIAL FOR
APPLICABILITY OF IMMOBILIZATION
CATEGORY
DATA REQUIREMENT
IMPORTANCE OF INFORMATION
Metal contaminants
Metal speciation: oxidation
states of Cr and As
Chemical form determines behavior of metal and
likely reactions with treatment reagents; Cr(VI),
As(III) and As(V) difficult to stabilize
Metal mobility
Leachability of metals; results of
equilibrium and/or diffusion-
controlled leach tests that mimic
expected post-treatment
disposal conditions
In order to meet RCRA LDRs, metals need to become
or remain immobile under expected disposal
conditions as treated materials age (e.g. TCLP)
E-2
-------
CATEGORY
Soil characteristics
Other contaminants
and constituents
present
Treatability Study
Testing (factors to be
evaluated during
treatability study
which influence
effectiveness)
DATA REQUIREMENT
pH and Eh; buffering capacity
Particle size
Particle size distribution
Moisture content
IMPORTANCE OF INFORMATION
Specific pH range and redox condition favors
effective setting; useful in determining conditions
leading to lowest solubility of metals; factor in
identifying solubility of metals
Fine particulate may coat waste particles and weaken
bond between waste solids and cement
May be easier to obtain uniform, complete mixing of
reagent with homogenous soil
Water may need to be added or removed to ensure
proper mixing of reagent with soil
In-Situ
Subsurface conditions
Depth of contamination
Total organic content; including:
VOCs, SVOCs, PAHs, etc.
VOC content
Oil and grease content
Phenol content
Halide content
Soluble salts of Mn, Sn, Zn, Cu,
Pb
Cyanide content
Sulfate content
Volume increase following
treatment; estimate total increase
based on increase in treatability
study
Bearing strength; evaluate
changes in response to
overburden stress between
treated and untreated waste;
cone index
Presence of subsurface barriers or debris and depth
to first confining layer may affect ability to achieve
proper mixing
In-situ mixing demonstrated to 30 feet; new
equipment may be applicable to 150 feet
Organic materials may interfere with bonding of
reagent with waste particles
VOCs can vaporize during process or curing
May interfere with bonding of reagent
with waste particles
May reduce compressive strength of final product
May alter cement setting rate; are soluble and can
leach from cement
May reduce physical strength and dimensional
stability of cured matrix and/or cause large variations
in setting time
May interfere with bonding of reagent with waste
particles
May retard setting and/or cause cement to spall after
setting
Increases transportation and disposal costs; may
eliminate possibility of onsite disposal
Must exceed intended use limits
E-3
-------
CATEGORY
DATA REQUIREMENT
Flexural strength; evaluate
treated materials ability to
withstand loads over large areas
pH, alkalinity; evaluate changes
in leaching as a function of pH
IMPORTANCE OF INFORMATION
Must exceed intended use limits
Immobilization of metals may not be effective if pH of
treated matrix changes
Containment
Purpose
For purposes of this presumptive remedy, containment of wastes in place includes vertical and horizontal barriers.
This remedial technology can provide sustained isolation of contaminants and can prevent mobilization of soluble
compounds over long periods of time. It also reduces surface water infiltration, controls odor and gas emissions,
provides a stable surface over wastes, limits direct contact, and improves aesthetics.
Description of the Presumptive Remedy
Specific factors influence the selection of containment materials and design including the cost of cap materials, the
local availability of capping materials, projected future use of the site, desired function of the cover material, the
nature of the waste, local climate and hydrogeology, and ARARs. Containment often includes regrading and
revegetation above the cap. See Exhibit E-3 for details about data requirements for containment.
EXHIBIT E-3
DATA REQUIREMENTS FOR CONTAINMENT OF METALS IN SOILS ON SITE 1
CATEGORY
Site Characteristics
DATA REQUIREMENT
Extent of contamination
Climate
Depth to groundwater
IMPORTANCE OF INFORMATION
Determines cost-effectiveness of remedy
Water infiltration rate is a determinant of type of cover
needed
May not be effective in areas with high groundwater table
'The majority of the information in this table was obtained from Contaminants and Remedial Options at Selected Metal-
Contaminated Sites, Office of Research and Development (ORD), U.S. EPA, EPA/540/R-95/512, July 1995. This table summarizes
the information and does not provide the level of description and analysis that is contained in the ORD document. Site managers
employing this presumptive remedy should refer to Contaminants and Remedial Options for more detail on the information
presented in this table. Information on containment taken from Lawrence A. Smith, et al. Remedial Options for Metals-
Contaminated Sites. CRC Press, 1995.
E-4
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