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ROD GUIDANCE
DEVELOPMENT AND DOCUMENTATION
FOR NO ACTION RODs,
INTERIM ACTION RODs,
AND CONTINGENCY RODs
Offi£e °f Emergency and Remedial Response
Office of Waste Programs Enforcement
-------
ROD GUIDANCE
l;
STANDARD ROD FORMAT
1. Declaration
Site Name and Location
Statement of Basis and Purpose
Assessment of the Site
Description of Selected Remedy
Statutory Determinations
Signature and Support Agency
Acceptance of the Remedy
2. Decision Summar
Site Name, Location, and
Description
Site History and Enforcement
Activities
Highlights of Community
Participation
Scope and Role of Operable Unit
Site Characteristics
Summary of Site Risks
Description of Alternatives
Summary of Comparative Analysis
of Alternatives
Selected Remedy
Statutory Determinations
Explanation of Significant Changes
3. Responsiveness Summary
-------
ROD GUIDANCE :
NO ACTION RODs
"No Action" RODs may be warranted under the
following circumstances:
The site or operable unit poses no current or
potential threat to human health and the
environment
CERCLA does not provide the authority to take
remedial action.
A previous response eliminated the need for further
remedial response.
-------
ROD GUIDANCE
NO ACTION RODs (cont'd)
"No Action" alternative may Include monitoring
Alternatives that Include components designed to
reduce/prevent exposure (e.g., fence, Institutional
controls) are considered "'limited action"
alternatives.
-------
ROD GUIDANCE :
NO ACTION ROD FORMAT
1. Declaration
Site Name and Location
Statement of Basis and Purpose
Assessment of the Site
Description of Selected Remedy
Statutory Determinations
Declaration Statement
Signature and Support Agency Acceptance of
the Remedy
NO ACTION RODS
Description of Selected Remedy
The ROD should state that no action is necessary for the site/OU.
Monitoring may be authorized.
Declaration Statement
If action is not necessary for protection, the ROD should state that no remedial action is
necessary to ensure protection of human health and the environment.
If no action is taken because there is no CERCLA authority to take action, the ROD
should explain that EPA doesn't have authority under CERCLA 104 or 106 to address
the problems posed by the site/OU. If a problem has been referred to other authorities,
this should be explained.
If taking "no further action," the ROD should explain that previous response(s)
eliminated the need to conduct additional remedial action. The ROD should also state
whether a 5 year review is required. CERCLA requires a 5 year review of earlier
remedies that eliminated the need to take further action (i.e. institutional controls) but left
hazardous substances, pollutants or contaminants on site.
-------
ROD GUIDANCE :
NO ACTION ROD FORMAT (cont'd)
2. Decision Summary
Site Name, Location, and Description
Site History and Enforcement Activities
Highlights of Community Participation
Scope and Role of Operable Unit or Response
Action
Site Characteristics
Summary of site Risks
Deeerlptfan ef AHemotlvee
Summary of Comparative Analysis of Alternate
Selected Remedy
Statutory Determinations
Explanation of Significant Changes
3. Responsiveness Summary
NO ACTION ROD FORMAT
Summary of Site Risks
This section needs to support the decision for not taking an action. The
conclusions of the baseline risk assessment need to be explained.
Any previous responses conducted at the site/OU that eliminated the need for
additional remedial action should be discussed.
If any alternatives were developed in the FS, the FS should be referenced.
-------
ROD GUIDANCE '•
INTERIM ACTION RODs
Interim action*:
are limited In scope
address only areas/media that will be followed bv a
final ROD
intent Is to address problem more fully in a
subsequent action
INTERIM ACTION RODS
EXAMPLES OF INTERIM ACTION RODs: (These Talking Points are for this slide and the next
slide.)
Install barrier wells to contain contaminant plume - remediation levels addressed in a
subsequent ROD
Provide temporary alternate water supply - management decisions addressed in
subsequent ROD(s) for contamination source(s) and/or aquifer addressed in subsequent
ROD(s)
Construct temporary cap to control or reduce exposure - final waste management
decision to address source (e.g. treatment) provided in subsequent ROD
Temporarily consolidate contaminated material for storage - final waste management
decision addressed in subsequent ROD.
-------
ROD GUIDANCE :
INTERIM ACTION RODs (cont'd)
Interim actions may be necessary to:
protect human health and the environment from an
imminent threat In the short term, while a final
solution is being developed
temporarily stabilize the site/operable unit to prevent
further contaminant migration and/or degradation
-------
ROD GUIDANCE '
INTERIM ACTION ROD FORMAT
1. Declaration
Sit* Nam* and Location
• Statement of Baal* and Purpose
« Assessment of the Site ":
Description of Selected Remedy
• Statutory Determinations
Signature and Support Agency Acceptance of
the Remedy
INTERIM ACTION ROD FORMAT
State that interim remedy:
protects human health and the environment.
complies with ARARs for the limited scope of the action.
is cost effective.
Additionally:
If the remedy does not employ treatment, state that the statutory preference for
treatment will be addressed by the final response action.
If the remedy does employ treatment, include language that says that the remedy is in
furtherance of the statutory preference for treatment.
The statutory preference for treatment will be addressed by the final response action.
-------
ROD GUIDANCE :
INTERIM ACTION ROD FORMAT (cont'd)
2. Decision Summary
Site Name, Location, and Description
Site History and Enforcement Activities
Highlights of Community Participation
Scope «nd Role of Operable Unit
Site Characteristics
Summary of Site Risk*
Description of Alternative*
Summary of Comparative Analysis of Alternatl
Selected Remedy
Statutory Determinations
Explanation of Significant Changes
3. Responsiveness Summary
ves
INTERIM ACTION ROD FORMAT (cont'd)
Scope and Role
Describe what action is being performed at the site and state how the interim action will be
consistent with any planned future actions.
Site Characteristics
Indicate description of site/OU characteristics to be addressed by the interim remedy.
Site Risks
Identify the risks addressed by the interim action and the rationale for the limited scope of
action. Qualitative risk information may be presented if quantitative risk information is not
yet available. This will often be the case.
Description of Alternatives
Describe the limited alternatives that were considered for the interim action.
Comparative Analysis
Evaluation criteria that are not relevant to the evaluation of interim actions do not have to
be addressed in detail. Note their irrelevance to the decision.
Statutory Determinations
Focus only the ARARs specific to the interim action.
State that the interim remedy is the best balance of tradeoffs among alternatives with
respect to the pertinent criteria.
The preference for treatment will be addressed in the final action.
-------
ROD GUIDANCE '•
INTERIM VS. FINAL EARLY ACTIONS
Early remedial action* may be ahher Interim or final
May not ba sufficient time to prepare "formal" Rl/FS.
Analysis should ba streamlined:
summary of site data
short analysis of considered remedial alternatives
and basis for rejection/selection.
Analysis/Information can ba provided in proposed
plan/ROD
ROD follows appropriate format (i.e., interim or final)
INTERIM VS. FINAL EARLY ACTIONS
EXAMPLES OF EARLY ACTIONS
Earlv Interim Action
Providing an alternate water supply and sealing wells that are pumping from a
contaminated aquifer.
Earlv final action
Complete removal of drums and surrounding contaminated soil to address
imminent threat and further limit degradation.
-------
ROD GUIDANCE :
RISK ASSESSMENTS FOR EARLY
AND INTERIM ACTIONS
Completed baseline risk assessment not necessary
Potential risk and the need to take an action must be
demonstrated
Contaminants of concern, concentrations and
exposure information
RISK ASSESSMENTS FOR EARLY AND INTERIM ACTIONS
A completed baseline risk assessment is not a requirement to take an interim or early
action.
ROD has to contain enough information to demonstrate the potential risk and the need
to take action.
This information can include a summary of contaminants of concern, concentrations and
relevant exposure information.
-------
ROD GUIDANCE '•
CONTINGENCY REMEDIES
Minimal use
TreatabllKy studios during RI/FS
Ground water remedies
CONTINGENCY REMEDIES
Contingency remedies should be used in limited circumstances because treatability
studies should be performed before ROD is signed to ensure technology's performance.
Appropriate when:
- Significant uncertainty exists about the ability of remedial alternatives to achieve
cleanup levels for ground water actions.
Either innovative technology is selected or a proven technology is used on a waste
where performance data are not available.
-------
ROD GUIDANCE :
PRE-ROD AND POST-ROD CHANGES
Office of Emergency and Remedial Response
Office of Waste Programs Enforcement
-------
ROD GUIDANCE :
PRE-ROD CHANGES
Minor Changes
Little or no impact on overall scope, performance, or
cost of the alternative originally presented as the
preferred remedy.
PRE-ROD CHANGES
EXAMPLES OF PRE-ROD CHANGES
Minor Changes
Altering the Selected Remedy to include a few more ground water extraction wells
than were originally estimated in the Proposed Plan.
-------
ROD GUIDANCE
PRE-ROD CHANGES (cont'd)
Significant Changes
Significant or fundamental effect on the scope,
performance, and/or cost of the preferred remedy.
Generally Involve either:
selection of an Rl/FS alternative other than the
preferred alternative as the remedy; or
substantial modification of a component of the
selected remedy.
PRE-ROD CHANGES (cont'd)
EXAMPLES OF PRE-ROD CHANGES
Significant Changes
In response to comments, the final remedy combines one component of the
preferred alternative (e.g., for ground water remediation) and a component of a
different alternative presented in the Rl/FS Report (e.g., soil remediation).
-------
BOD GUIDANCE :
PRE-ROD CHANGES (cont'd)
DOCUMENTATION
Minor Changes
Document in Description of Alternatives section of the
ROD Decision Summary
If logical outgrowth:
document In Decision Summary of the ROD in the
Documentation of Significant Changes section.
If not logical outgrowth:
Issue revised Proposed Plan;
document in Decision Summary of the ROD In the
Documentation of Significant Changes section.
-------
ROD GUIDANCE :
LOGICAL OUTGROWTH
Public could have reasonably anticipated the change based
on available Information
Example: Change In components of the preferred
alternative based on public comment.
LOGICAL OUTGROWTH
The public could have reasonably anticipated the change based on the information in
the RI/FS, proposed plan, and comments submitted during public comment period.
Example: Change in the preferred alternative's cost and implementation time based on
public comment.
-------
ROD GUIDANCE :
POST-ROD CHANGES
Minor Changes
Example: Amount of waste to be treated is
slightly higher than expected and
consequently Increase In cost Is minimal
Document In the post-decision document file.
POST-ROD CHANGES
The amount of a cost increase is not specific in order to give flexibility to regions.
Difference ranging from 50% over cost to 30% under cost should be used as a guide.
Call appropriate regional coordinator to assist in making determinations.
-------
ROD GUIDANCE '
POST-ROD CHANGES (cont'd)
Significant Changes
Example: Wastes must be managed at a
Subtitle C facility rather than a Subtitle D facility,
as stated In the ROD.
Document in Explanation of Significant
Differences.
-------
ROD GUIDANCE '
EXPLANATION OF SIGNIFICANT DIFFERENCES
(ESD) DOCUMENTATION
• Fact Sheet format
Explain:
changes to remedy
Information
statutory determinations
ESD DOCUMENTATION
The ESD can be in a fact sheet format.
The ESD should:
explain the changes to the remedy.
- summarize information that lead to the decision to change the remedy.
- affirm that statutory determinations of CERCLA121 are met.
-------
ROD GUIDANCE
POST-ROD CHANGES (cont'd)
• Fundamental Changes
Example: Selected remedy prove* Infeaslble - a
new remedy must be chosen.
Document in a ROD Amendment
-------
ROD GUIDANCE :
ROD AMENDMENT DOCUMENTATION
Focus on:
• Rationale for changa
Nina-criteria analysis
Statutory requirements are satisfied
ROD AMENDMENT DOCUMENTATION
Focus on documenting rationale for the ROD amendment.
For the part of the ROD being amended, add the required new 9 criteria analysis.
Cross-reference the original ROD where appropriate.
Indicate that the remedy satisfies the statutory requirements.
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CURRENT STATUS '.
PRINCIPAL THREAT AND LOW LEVEL
THREAT WASTES
CURRENT STATUS
Office of Emergency and Remedial Response
Office of Waste Programs Enforcement
PRINCIPAL THREAT AND LOW LEVEL THREAT WASTES
The need for guidance on the use of the terms principal threat and low level threat was
identified during the FY'90 ROD Forums.
CURRENT STATUS:
Although the principal threat and low level threat policy is under development, the
information presented today is expected to be very similar to that which will be issued.
STATUS:
Draft policy provided to the National Risk Management Work Group for review.
Revised policy will be provided to the Regions for review.
Finalize policy fourth-quarter of FY'91.
-------
CURRENT STATUS
PRINCIPAL THREAT AND LOW LEVEL
THREAT WASTES GUIDANCE
Purpose:
To clarify and standardize use of
terms
Content:
Use of Terms
NCP Expectations
Definitions
ROD Documentation
PRINCIPAL THREAT AND LOW LEVEL THREAT WASTES GUIDANCE
PURPOSE:
Provide guidance on the use of these terms in the Superfund Program.
CONTENT:
Use or role of these terms in the Superfund program.
Relationship of NCP expectations to remedy selection.
Definition of principal threat and low level threat wastes.
ROD documentation requirements.
-------
CURRENT STATUS
USE OF TERMS
Purpose of Terms:
Streamline the RI/FS process based on NCP
expectations
Remedy Selection:
Based on the nine evaluation criteria
USE OF TERMS
PURPOSE OF TERMS:
Streamline RI/FS process based on NCP expectations.
Designation of waste as a principal or low level threat does not dictate whether an action
is necessary, but rather provides management expectations after a decision has been
made to take action at a site.
REMEDY SELECTION:
The baseline risk assessment and the chemical-specific standards that define the
acceptable risk levels (e.g., non-zero MCLGs, MCLs) help to gauge whether remedial
action is warranted.
• Once a decision is made that action is warranted, these terms serve primarily as tools to
facilitate the consideration of the NCP expectations (40 CFR 300.430(a)(1)(iii)) on a
site-specific basis.
It should be stressed that a ROD may address only low level threat waste and still
warrant remedial action.
Remedy selection is based on the nine evaluation criteria.
-------
CURRENT STATUS
NCP EXPECTATIONS FOR SOURCE
MATERIALS
Treatment of principal threat wastes
Engineering controls for low level threat wastes
Engineering controls where treatment is
impracticable
Use of a combination of methods
Use of institutional controls to supplement
engineering controls
NCP EXPECTATIONS FOR SOURCE MATERIALS:
The expectations are non-binding requirements.
The expectations do not dictate the selection of the remedial alternative.
The remedy selection decision is based on an evaluation of the alternatives in
accordance with the NCP.
There will be situations where based on the nine evaluation criteria the selected remedy
does not meet the expectations (e.g., cost effectiveness).
Treatment may not be selected for principal threat waste because of the following
reasons: implementability, greater risk, or cross-media effects.
Treatment may be selected for low level threat waste for the following reasons:
unreliable containment (e.g., technical difficulties)
sensitive environment
low volume
-------
CURRENT STATUS
DEFINING PRINCIPAL THREAT WASTES
Definition:
Highly toxic or highly mobile wastes
Cannot be reliably controlled
Significant risk to human health or the
environment
Includes:
• Liquids
Solvents
High concentrations of toxic compounds
Does not Include:
Contaminated ground water
DEFINING PRINCIPAL THREAT WASTES:
Principal threat is not solely determined by the degree of risk but also takes into
consideration the physical state of the material (e.g., liquid) and the potential mobility of
the wastes in the particular environmental setting.
Wastes that present a significant risk generally will be deemed a principal threat.
Wastes that significantly exceed ARARs or that present a significant non-carcinogenic
health threat also will be deemed a principal threat.
Ground water is not included in the definitions of principal threat or low level threat
wastes; the NCR established expectations for ground water separately from other
materials.
Free products (NAPLs), sediments, lagoon materials, are generally considered source
material, and therefore, may be principal threat waste.
-------
CURRENT STATUS
DEFINING LOW LEVEL THREAT WASTES
Definition:
Low mobility wastes
Can be reliably controlled
Low risk In the event of exposure
Includes:
• Solids
Moderate to low toxlcity
Does not Include:
Contaminated ground water
DEFINING LOW-LEVEL THREAT WASTES:
Low level threat wastes are those wastes that are not principal threat wastes nor are
they contaminated ground water.
Risk is one measure of differentiating between principal threat and low level threat
wastes.
Wastes that pose a threat at the lower end of the risk range may be deemed a low level
threat waste.
Wastes that pose a risk in the middle of the extremes may either be characterized as
principal threat or low level threat waste depending on the site-specific factors (e.g.,
uncertainty).
-------
CURRENT STATUS
ROD DOCUMENTATION
Declaration:
Characterize the wastes
Discuss how the statutory preference for treatment Is
met
Decision Summary:
Characterize the wastes as principal threat, low level
threat waste, or contaminated ground water
Provide supporting rationale
Discuss how the preference for treatment is satisfied
ROD DOCUMENTATION:
Declaration:
The "Description of the Selected Remedy" section should identify the waste as principal
threat, low level threat waste, or contaminated ground water and provide clear rationale.
The "Statutory Determinations" section of the ROD Declaration should discuss how the
selected remedy satisfies the statutory preference requirements of CERCLA section 121 to
select remedial actions "in which treatment which permanently and significantly reduces the
volume, toxicity, or mobility of the hazardous substances, pollutants, and contaminants is a
principal element..."
The statutory determination is based on the degree that treatment is a principal element
and not whether the ROD selected treatment for the principal threat wastes. (Fact Sheet
will provide additional guidance)
Preference for treatment would generally not be met if principal threat waste were the only
materials treated but they were a very small portion of the site.
Decision Summary:
The "Site Characteristics", "Description of Alternatives", and the "Selection of Remedy"
sections should identify the wastes as principal threat, low level threat waste, or
contaminated ground water and provide supporting rationale.
The "Statutory Determinations" section, should include a discussion of how the preference
for treatment is satisfied or explain why it is not satisfied.
The statutory determination is based on the degree that treatment is a principal element
and not whether the ROD selected treatment for the principal threat wastes.
-------
INNOVATIVE:
INNOVATIVE TREATMENT TECHNOLOGIES
Office of Emergency and Remedial Response
Office of Waste Programs Enforcement
INNOVATIVE TREATMENT TECHNOLOGIES
Agency definition/policy on innovative treatment technologies was developed to
standardize the use of terms and to enable the agency to communicate clearly with
the public.
Characterizing treatment as innovative or available in the ROD is important to allow
program analyses on the elements. This effort also allows for the identification of
those technologies which may need treatability studies.
Agency policy was developed via work group meetings between OERR, ORD, and
TIO (Technology Innovation Office). The policy represents state of the knowledge on
immobilization.
A draft fact sheet was developed and provided to the Regions in March for review and
comment.
The fact sheet is expected to be finalized in the third-quarter of FY'91.
-------
INNOVATIVE:
INNOVATIVE TECHNOLOGY GUIDANCE
Purpose:
Standardize use of terms.
Content:
Agency policy
Classification of Treatment Technologies
TreatabllHy studies
ROD documentation
INNOVATIVE TECHNOLOGY GUIDANCE
PURPOSE: Provide guidance on innovative technologies such that the Agency can foster
the use of such technologies and evaluate the progress of the program toward these
ends.
CONTENT:
Agency policy/definition of what constitutes innovative treatment technology(ies),
Classification of Treatment Technologies,
Agency policy on performance of treatability studies, and
ROD documentation requirements.
-------
INNOVATIVE:
AGENCY POLICY
Innovative Treatment Technologies:
Limited data on performance or cost
Most are source control technologies
In-sltu treatment technologies
Available Treatment Technologies:
Available data on performance and cost
• Immobilization of most Inorganics
Incineration of most organics
Most are wastewater treatment technologies
AGENCY POLICY
Characterization of technologies as innovative or available will change overtime as we gain
experience.
INNOVATIVE TREATMENT DEFINITION:
Innovative treatment technologies are those technologies where limited data on
performance and/or cost inhibit their use for many Superfund types of applications.
Innovative treatment technologies are based on the NCR expectations for these
technologies (40 CFR 300.430(a)(1)(iii)(E)).
Because of the general lack of available technologies we anticipate considering
innovative technologies at many sites.
Includes most source control technologies and in-situ treatment technologies.
AVAILABLE TREATMENT TECHNOLOGIES
Currently includes incineration of organics, immobilization of inorganics, and most waste
water treatment technologies.
-------
INNOVATIVE -
CLASSIFICATION OF TREATMENT
TECHNOLOGIES
Source Material - Grouped by primary function:
Destruction/Detoxification
Separation/Recovery
Immobilization
• Other
Aqueous Material - Grouped by general use categories:
Biological
Chemical/Physical Treatment
• Other
CLASSIFICATION OF TREATMENT TECHNOLOGIES
TREATMENT TECHNOLOGIES:
A partial list of innovative and available treatment technologies is provided in the draft
Fact Sheet included in the handout that is entitled: "Innovative Treatment
Technologies."
Technologies have been grouped by primary function for source materials and by
general categories used in the waste water treatment industry for aqueous materials.
• The category of "other" includes technologies involving multiple treatment functions
(e.g., immobilization and thermal destruction) or those technologies that do not fit into a
specific category.
A treatment technology listed as innovative or available may not always fit that category
in actual application. If a technology listed as innovative is used in a situation similar to
that for which we have extensive data it may be available.
Assistance on classification of technologies as innovative or available can be obtained
through ORD or your Regional Coordinator.
These categories also serve the purpose of providing some inclination as to the potential
need for treatment trains (e.g., separation/recovery technologies will generally be
followed by other technologies).
-------
INNOVATIVE •
TREATMENT TECHNOLOGY SYNONYMS
A listing of preferred terms and commonly used synonyms is provided below.
Preferred Term
Destruction/Detoxification
Thermal Destruction
Solid-Phase/Bioremediation
Separation/Recovery
Solvent Extraction
Synonym
Thermal Treatment
Land Farming
Land Treatment
Land Application
Contained Solid-Phase
Critical Fluid Extraction
Carton Dioxide Solvent
Extraction
Propane Solvent
Extraction
Tnethylamine Solvent
Extraction
Preferred Term
Extraction
Ex-SHu Thermal
Desorption
Soil Vapor Extraction
(SVE)
Immobilization
Synonym
Enhanced Volatilization
Low-Terrperature
Desorption
Low-Temperature
Thermal Treatment
Thermal Aeration
Thermally Enhanced
Volatilization
Vapor Extraction
In-Situ Volatilization
Soil Venting
Fixation
A
TREATMENT TECHNOLOGY SYNONYMS
This is a listing of preferred terms and those that have been used historically as
synonyms.
Some of the terms in the synonym column are specific examples of the preferred terms,
while others are terms that are out-dated or do not present a clear indication of the
technology.
Thermal treatment is a term that does not clearly convey the technology. It is
recommended that thermal destruction be used to mean incineration and thermal
desorption be used for extractive type processes.
The synonyms for solvent extraction are more specific examples of the technology.
Passive soil venting is not considered treatment. This is similar to the situation on
natural restoration.
-------
INNOVATIVE •
TREATABILITY STUDIES
Treatabllltv Studies
Are to be conducted early in RI/FS when
Insufficient data are available
Will generally be needed for Innovative
technologies
TREATABILITY STUDIES
Treatability studies of some scale are expected to be needed for innovative
technologies.
Since most technologies fall within this category, treatability studies should be planned
for most sites involving treatment unless data are available to reference for the remedial
decision.
-------
INNOVATIVE •
ROD DOCUMENTATION
ROD Declaration should Include:
Identification and characterization of treatment
alternatives
ROD Decision Summary should Include:
Identification and characterization of treatment
alternatlve(s)
Rationale for characterization
Media/waste type and volume
Treatability study performance
Reference of treatability study(ies)
ROD DOCUMENTATION
ROD DECLARATION:
The "Selection Remedy" section should identify the treatment technologies as available
or innovative.
ROD DECISION SUMMARY:
The following information should be discussed in the "Description of the Alternatives,"
"Summary of Comparative Analysis of Alternatives" and the "Selected Remedy" sections of
the ROD:
Identification of treatment altemative(s),
Characterization of the treatment technology as innovative or available,
Supporting justification for those situations where a technology is characterized
differently from that provided in the examples above,
Information on the type of media, waste constituents, and volume that will be treated by
the treatment technology,
Information on the performance and effectiveness of treatability studies, and
References of treatability study(ies), if provided in lieu of a site-specific study.
-------
DRAFT
United States Office of Publication 9380.3-05FS
Environmental Protection Solid Waste February 1991
Agency and Emergency
Response
INNOVATIVE TREATMENT TECHNOLOGIES
Office of Emergency and Remedial Response
Hazardous Site Control Division Quick Reference Fact Sheet
OS-220W
The Environmental Protection Agency believes that it is
important to foster the development and implementation of
innovative treatment technologies, particularly those
technologies which offer the potential for comparable or superior
treatment performance or implementability, fewer adverse impacts,
or lower cost for similar performance. The National Oil and
Hazardous Substances Pollution Contingency Plan (NCP) promulgated
on March 8, 1990 encourages the evaluation of innovative
technologies in developing remedial alternatives. (40 CFR Section
300.430(a)(1)(iii)(E).)
The purpose of this guide is provide guidance on innovative
technologies such that the Agency can direct efforts towards
fostering the use of such technologies and can evaluate the
progress of the program towards these ends. This guide provide a
definition of "innovative treatment technology(ies)", examples,
guidance on treatability studies, and ROD documentation
requirements.
DEFINING INNOVATIVE TREATMENT TECHNOLOGIES
Innovative Treatment Technologies are those technologies
where limited available data on the performance and/or cost
inhibit their use for many Superfund types of applications.
Innovative treatment technologies are considered based on
the NCP expectations for these technologies (40 CFR
300.430(a)i(l)(iii)(E)). That is to say, innovative
technologies are generally considered when they offer the
"potential for comparable or superior treatment performance
or implementability, fewer or lesser adverse impacts than
other available approaches, or lower costs for similar
levels of performance than demonstrated technologies."
Because of the general lack of available technologies we
anticipate that at many sites we will consider innovative
technologies.
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ANALYSIS OF DEFINITION AS IT APPLIES TO SUPERFUND
The Superfund program's definition of innovative technologies
includes the following:
o "New" technologies that have been demonstrated at the
bench- or pilot-scale for a limited number of
applications, and
o "Demonstrated" or "available" technologies used in
various industries but for which limited data are
available for Superfund site applications.
Since the types of materials encountered at Superfund sites
(particularly soil and debris) differ from bulk waste generally
treated at RCRA facilities, technologies that are commonly
employed at a RCRA facility may be considered innovative for a
Superfund application.
Although the Agency has selected diverse remedial
alternatives for Superfund sites, our experience in the
application of these technologies is limited. Immobilization of
inorganics and incineration of organics are generally considered
proven technologies for which we have extensive experience.
However, we have limited experience with many other types of
treatment technologies which may be utilized to treat source
material. For these reasons, we consider all source control
alternative technologies, with the exception of immobilization of
most inorganics and incineration of most organics, to be
innovative at the present time.
There will be occasions where a demonstrated or proven
technology is used in a manner that constitutes an innovative
application. For example, incineration of a complex waste
containing materials for which we have limited experience (e.g.,
NOx generating compounds) or innovative applications or designs
also may warrant the inclusion of these technologies into the
category of innovative technology. The selection of an
innovative design for thermal treatment or immobilization is
expected to be an infrequent event. RODs should usually identify
a generic type of technology (e.g., thermal destruction) rather
than a specific design (e.g., rotary kiln) unless specific
conditions warrant such as selection. Immobilization of some
inorganic compounds (e.g., arsenic, hydrogen cyanide, chromium
VI) is considered less proven and also would fall into the realm
of innovative treatment.
With regard to ground-water remediation, most technologies
selected for ex-situ treatment of ground water have found common
usage in the waste water treatment industry and it is believed
that these are generally "available technologies" for many
Superfund applications. There are a few technologies, and
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hopefully there will be more in the future, which are or will be
considered innovative technologies. In addition, treatment of
waste water treatment residuals also may utilize many of the
technologies applicable to source material, and these also may be
considered innovative.
Conversely, all in-situ technologies for remediating ground
water and source material are considered innovative at this time.
We anticipate that the list of remedial alternatives which
are characterized as "innovative technologies" in the Superfund
program will change over time. Technologies will graduate to the
"available technology" category and new technologies will enter
the "innovative technology" category. As a result, an annual
analysis of Superfund progress will use a consistent definition
but the list of technologies that comprise that category will
change.
This definition does differ slightly from that which is used
in the Agency's Superfund Innovative Technology Evaluation (SITE)
program but we believe the differences are justified and should
not affect analysis conducted by either program. The SITE
program considers three stages of technology development:
(1) Available Alternative Technology - technologies that are
fully proven and routinely used at hazardous waste sites.
(2) Innovative Alternative Technology - any fully developed
technology for which cost or performance information is
incomplete, thus hindering routine use. An innovative
alternative technology requires field testing and evaluation
before it is considered proven and available for routine
use.
(3) Emerging Alternative Technology - a technology in an
earlier stage of development. Documentation has involved
laboratory testing, and the technology is being developed at
pilot-scale prior to field testing at Superfund sites.
For purposes of the Superfund program we have grouped the last
two categories under the term "innovative technology." While the
Agency will primarily be selecting technologies which fall under
the first two categories of the SITE program, there may be
situations where an "emerging technology" may also be selected
based on developmental efforts conducted at a site. Therefore,
for purposes of the Superfund program there does not appear to be
a reason for maintaining a separate category for emerging
technologies for the Superfund program.
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EXAMPLES
Table 1 provides a list of treatment technologies which are
currently considered "innovative" or "available". The list is
not intended to be exhaustive. Most of the technologies listed
have been selected in Records of Decisions (RODs); a few
additional technologies have been listed because they are
believed to have a high potential of being applied to Superfund
sites. Other technologies are under development and are
innovative technologies. As these are selected as remedial
alternatives for Superfund sites they will be added to the list.
Table 2 provides a listing of treatment technology synonyms
which will aid in the use of Table 1.
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Table 1
CLASSIFICATION OF TREATMENT TECHNOLOGIES
FOR TREATMENT OF SOURCE MATERIALS1
Treatment technologies for source material are grouped based on
the primary function for which they are generally used:
destruction/detoxification, separation/recovery, immobilization,
and other.
INNOVATIVE
DESTRUCTION/DETOXIFICATION
Bioremediation
Composting
Solid-Phase Bioremediation
Slurry-Phase Bioremediation
Soil Heaping
Vacuum-Enhanced Bioremediation
In-Situ Bioremediation
Chemical Destruction
Dehalogenation
Dechlorination
Chemical Oxidation
Chemical Reduction
Thermal Destruction
Incineration (Organics in the presence of inorganics2)
The list is not all inclusive.
2 Thermal destruction technologies are generally considered
available for most organic wastes. Thermal destruction of
organic waste mixed with inorganics (e.g., metals, hydrogen
cyanide, nitrous oxide generating compounds) may be innovative if
it requires innovative engineering approaches to address
emissions problems and/or concerns regarding residuals
characteristics.
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Classification of Innovative Treatment Technologies for Treatment
of Source Materials (Continued):
SEPARATION/RECOVERY
Chemical/Physical Extraction
Solvent Extraction
Soil Washing
In-Situ Vacuum Extraction
Soil Vapor Extraction (SVE)
Thermally-Enhanced Vacuum Extraction
In-Situ Soil Flushing
Thermal Desorption
Ex-Situ Thermal Desorption
In-Situ Steam Stripping
In-Situ Hot Air Stripping
IMMOBILIZATION3
Solidification/Stabilization (Organics and select
inorganics (e.g., Ar, HCN, Cr(VI))
Stabilization (Organics and select inorganics (e.g.,
Ar, HCN, Cr(VI))
In-Situ Solidification/Stabilization (All wastes)
In-Situ Stabilization (All wastes)
OTHER*
Ex-Situ Vitrification
In-Situ Vitrification
3 Immobilization is generally considered innovative when it
involves treatment of organics and/or treatment of inorganics
which include arsenic, hydrogen cyanide, or chromium(VI). This
is primarily due to uncertainty regarding the effectiveness of
the technology for these waste types.
4 The "Other" category includes technologies involving
multiple treatment functions (e.g., destruction and
immobilization), generally due to the presence of both organics
and metals in the source material.
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Classification of Available Treatment Technologies for Treatment
of Source Materials:
AVAILABLE5
DESTRUCTION/DETOXIFICATION
Thermal Destruction
Incineration (Oganics)
Rotary Kiln Incineration
Fluidized Bed Incineration
Liquid Injection Incineration
Infrared Incineration
IMMOBILIZATION (Most inorganics and metals)
Stabilization
Solidification/Stabilization
Sorbent Solidification
CLASSIFICATION OF TREATMENT TECHNOLOGIES
FOR TREATMENT OF AQUEOUS STREAMS6
Treatment technologies for aqueous streams are grouped based the
categories commonly used in the waste water treatment industry:
biological, chemical/physical treatment, and other.
INNOVATIVE
BIOLOGICAL
In-Situ Biodegradation for Ground Water
OTHER
All in-situ treatment methods applied to the saturated zone
for ground water remediation.
5 In some cases, modifications of available technologies
may be considered innovative.
6 The list is not all inclusive.
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8
Classification of Available Treatment Technologies for Treatment
of Aqueous Streams:
AVAILABLE7
BIOLOGICAL
Activated Sludge
Aerobic Treatment
Fixed-film Reactors
Rotating Biological Contactors
Sequencing Batch Reactors
CHEMICAL/PHYSICAL TREATMENT
Air Stripping
Carbon Adsorption
Chemical Precipitation
Ion Exchange
Reverse Osmosis
Steam Stripping
Ultrafiltration
UV/Oxidation
In some cases, modifications of available technologies
may be considered innovative.
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Table 2
TREATMENT TECHNOLOGY SYNONYMS
A listing of preferred terms and commonly used synonyms are
provided below.
PREFERRED TERM
Destruction/Detoxification
Thermal Destruction
Solid-Phase Bioremediation
SYNONYM
Thermal Treatment8
Land Farming
Land Treatment
Land Application
Contained Solid-Phase
Separation/Recovery
Solvent Extraction
Extraction
Critical Fluid Extraction
Carbon Dioxide Solvent
Extraction
Propane Solvent Extraction
Triethylamine Solvent
Ex-Situ Thermal Desorption
Soil Vapor Extraction (SVE)
immobilization
Enhanced Volatilization
Low-Temperature Desorption
Low Temperature Thermal
Treatment
Thermal Aeration
Thermally Enhanced
Volatilization
Vapor Extraction
In-Situ Volatilization
Soil Venting9
Fixation
Thermal Treatment has been used in the past to mean
either thermal destruction (e.g., incineration) or thermal
desorption (e.g., steam stripping).
9 Passive soil venting is also a means of ventilating
subsurface gases or vapors (such as methane) in the absence of a
vacuum. This type of soil venting is not considered treatment.
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10
TREATABILITY STUDIES
It is Agency policy that treatability studies will be
conducted during the remedial investigation/feasibility study
(RI/FS) when there are insufficient data to support the
evaluation choice of a treat remedy during the selection process.
This policy was provided in the directive entitled: "Advancing
the Use of Treatability Technologies for Superfund Remedies"
(OSWER Directive No. 9355.0-26, Feb. 21, 1989). The directive
points out the importance of treatability studies particularly
for "innovative technologies." The importance and need for
treatability studies was also identified in A Management Review
of the Superfund Program (July 1989).
Treatability studies will be needed for the selection and
implementation of innovative treatment technologies except for
those situations where sufficient information is available for
the treatment technology for similar waste and waste matrix.
Currently this information does not exist for most treatment
technologies termed innovative. Treatability studies may also be
needed for the "available" treatment technologies where
insufficient data are available to support the remedy evaluation
and/or implementation.
Guidance for designing and executing treatability studies
is provided in the Guide for Conducting Treatabilitv Studies
under CERCLA. Interim Final, EPA 540/2-89/058, December 1989 and
in the Treatabilitv Studies under CERCLA; An Overview. Quick
Reference Fact Sheet, Directive 9380/3-02FS, December 1989.
ROD DOCUMENTATION
The characterization of a treatment alternative as
"innovative" or "available" should be documented in the "Selected
Remedy" section of the ROD Decision Summary. The information
provided above together with knowledge about the technology and
site-specific information should be used to characterize
technologies.
The following information should be discussed in the
"Description of the Alternatives", "Summary of Comparative
Analysis of Alternatives" and the "Selected Remedy" sections of
ROD:
Identification of treatment alternative(s),
- Characterization of the treatment technology as
innovative or available,
Supporting justification for those situations where a
technology is characterized differently from that
provided in the examples above,
- Information on the media/waste type and volume which
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11
will be treated by the treatment technology,
- Information on the performance and effectiveness of
treatability studies, and
References of treatability study(ies), if provided in
lieu of a site-specific study.
FOR FURTHER INFORMATION
The appropriate Regional Coordinator for each Region located
in the Hazardous Site Control Division/Office of Emergency and
Remedial Response or the CERCLA Enforcement Division/Office of
Waste Programs Enforcement should be contacted for additional
information.
NOTICE: The policies set out in this memorandum are
intended solely as guidance. They are not intended, nor can
they be relied upon, to create any rights enforceable by any
party in litigation with the United States. EPA officials
may decide to follow the guidance provided in this
memorandum, or to act at variance with the guidance, based
on an analysis of specific site circumstances. The Agency
also reserves the right to change this guidance at any time
without public notice.
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IMMOBILIZATION AS TREATMENT
Office of Emergency and Remedial Response
Office of Waste Programs Enforcement
IMMOBILIZATION AS TREATMENT
Agency policy on the use of immobilization has been developed because of concerns
regarding the short- and long-term protectiveness afforded by the immobilization of
organic-containing wastes.
Agency policy was developed via workgroup meetings between OERR, ORD, and
OSW. The policy represents state of the knowledge on immobilization.
A draft Fact Sheet entitled "Immobilization as Treatment" (Publication #9380.3-07 FS),
was developed and provided to the Regions in March for review and comment.
The Fact Sheet is expected to be finalized in third-quarter of FY 91.
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IMMOBILIZATION:
IMMOBILIZATION GUIDANCE
Purpose:
Provide guidance on the conditions under which
immobilization is appropriate
Content:
Definition of Immobilization
Agency Policy
Land Disposal Restrictions
ROD Documentation Requirements
IMMOBILIZATION GUIDANCE
PURPOSE: Provide guidance on the conditions under which immobilization is an appropriate
treatment technology to employ under the Superfund program.
CONTENT:
This guide provides:
• A definition of immobilization,
Current Agency policy on the use of immobilization,
Status of the immobilization as it relates to the RCRA Land Disposal
Restrictions, and
ROD documentation requirements.
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IMMOBILIZATION I
IMMOBILIZATION AS TREATMENT
Office of Emergency and Remedial Response
Office of Waste Programs Enforcement
IMMOBILIZATION AS TREATMENT
Agency policy on the use of immobilization has been developed because of concerns
regarding the short- and long-term protectiveness afforded by the immobilization of
organic-containing wastes.
Agency policy was developed via workgroup meetings between OERR, ORD, and
OSW. The policy represents state of the knowledge on immobilization.
A draft Fact Sheet entitled "Immobilization as Treatment" (Publication #9380.3-07 FS),
was developed and provided to the Regions in March for review and comment.
The Fact Sheet is expected to be finalized in third-quarter of FY 91.
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IMMOBILIZATION -'
IMMOBILIZATION GUIDANCE
Purpose:
Provide guidance on the conditions under which
immobilization Is appropriate
Content:
Definition of Immobilization
Agency Policy
Land Disposal Restrictions
ROD Documentation Requirements
IMMOBILIZATION GUIDANCE
PURPOSE: Provide guidance on the conditions under which immobilization is an appropriate
treatment technology to employ under the Superfund program.
CONTENT:
This guide provides:
A definition of immobilization,
Current Agency policy on the use of immobilization,
Status of the immobilization as it relates to the RCRA Land Disposal
Restrictions, and
ROD documentation requirements.
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IMMOBILIZATION '•
DEFINITION OF IMMOBILIZATION
Definition:
Technologies that limit solubility or mobility of
contaminants
Includes:
Stabilization
Solidification/Stabilization
Sorbent Solidification
Does not Include:
• Solidification
DEFINITION OF IMMOBILIZATION:
The term "immobilization" is used to mean any of the technologies that limit the solubility
or mobility of contaminants, including:
- Stabilization
- Solidification/Stabilization
- Sorbent Solidification
Solidification is not included as a treatment technology under Superfund.
Solidification is solely intended to produce a monolith for purposes of structural integrity
and does not satisfy the statutory preference for treatment to reduce the toxicity,
mobility, or volume (TMV) under Superfund.
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IMMOBILIZATION:
SUPERFUND POLICY ON USE OF
IMMOBILIZATION
May be appropriate for Inorganics, semi-volatile
organlcs and/or non-volatile organics
Not appropriate for volatile organ ics
Pre-treatment required for volatile organ ics
Treatablltty study Is needed for semi-volatile and
non-volatile organ ics
Test method Is total waste analysis (TWA)
Demonstrate significant reduction In mobility
SUPERFUNO POLICY ON USE OF IMMOBILIZATION
Immobilization generally constitutes treatment of wastes to reduce toxicity, mobility, or volume
(TMV) in the following circumstances:
Immobilization of inorganics.
Immobilization of semi-volatile and non-volatile organics where a treatability study was
planned or performed. Treatability studies should generally achieve a 90 percent
reduction or greater of the contaminant concentration or mobility (using TWA before and
after treatment).
Non-site specific treatability studies may be used to demonstrate effectiveness but
should be referenced and discussed in the RI/FS and the ROD.
Immobilization is not deemed to constitute treatment to reduce TMV in the following
circumstances:
Immobilization of volatile organics. Immobilization cannot contain volatile organics
during the treatment process or after the treatment process.
Immobilization of semi-volatile and non-volatile organics where a treatability study
producing data meeting the above criteria is not performed, planned and/or referenced.
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HI MOBILIZATION '•
RCRA LAND DISPOSAL RESTRICTIONS
Immobilization is not BOAT for organics
Immobilization may be appropriate for a treatabllity
variance
Treatability test method for a treatability variance
employing Immobilization of organics has changed
RCRA LAND DISPOSAL RESTRICTIONS:
RCRA land disposal restrictions (LDRs) are potential ARARs for Superfund waste
management.
While immobilization under Superfund may be treatment to reduce TMV, it may not be
able to comply with the LDRs treatment standards.
Immobilization generally is not appropriate for compliance with existing LDR best
demonstrated available technology (BOAT) standards for organics (40 CFR section
268.43). Immobilization does not significantly lower the concentration of hazardous
constituents present.
Immobilization of organics does have a role in the treatability variance process for
contaminated soil and debris. (See "Superfund LDR Guide #6A (2nd Edition) Obtaining
a Soil and Debris Treatability Variance for Remedial Actions," Superfund Publication
#9347.3-06FS, September 1990.)
The evaluation method specified in Superfund LDR Guide #6A for the immobilization of
organic waste (first footnote on page two) has changed since the issuance of the
guidance -- Total Waste Analysis (TWA) should be used in lieu of TCLP for organics.
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nil!OBIUZATION '•
ROD DOCUMENTATION
ROD Decision Summary:
Type of waste
Constituents in the waste
Treatablllty study results
ROD DOCUMENTATION:
The following information should be provided in the "Description of the Alternatives,"
"Summary of Comparative Analysis of Alternatives," and the "Selected Remedy" sections of
ROD:
• Type of waste (i.e., non-volatile organics, semi-volatile organics, volatile organics,
or inorganics).
Constituents in the waste to be remediated by immobilization.
Treatability study results (literature reference and/or results of site-specific
studies) that demonstrate 90 percent reduction or greater in contaminant
concentration or mobility using TWA.
Treatability study results that demonstrate the effectiveness of immobilization to
achieve remediation levels.
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DRAFT
United States Office of Publication 9380.3-07FS
Environmental Protection Solid Waste February 1991
Agency and Emergency
Response
IMMOBILIZATION AS TREATMENT
Office of Emergency and Remedial Response
Hazardous Site Control Division Quick Reference Fact Sheet
Section 121(b) of CERCLA mandates the EPA to select remedies
that "utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum
extent practicable" and to prefer remedial actions in which
treatment "permanently and significantly reduces the volume,
toxicity, or mobility of hazardous substances, pollutants, and
contaminants as a principal element." Immobilization is one such
treatment technology which may find application at Superfund
sites to meet the CERCLA mandate for treatment. Since
immobilization is not generally considered a destructive or
removal treatment technology for which treatment effectiveness
can most easily be defined, it is important that the Agency
establish clear guidelines as to when and under what conditions
immobilization satisfies the CERLA mandate.
The purpose of this guide is to provide guidance on the
conditions under which immobilization is an appropriate treatment
technology under the Superfund program. This guide provides: a
definition of immobilization, the current Agency policy on the
use of immobilization for Superfund applications, the status of
the immobilization as it relates to the RCRA Land Disposal
Restrictions, and ROD documentation requirements.
DEFINITION OF IMMOBILIZATION
The term "immobilization" is used to mean any of the
technologies which limit the solubility or mobility of
contaminants. The term "fixation" has also been used as a
synonym for immobilization. Technology types which fall within
the realm of immobilization include:
Stabilization
Solidification/Stabilization
Sorbent Solidification
The various immobilization technologies limit solubility or
mobility with or without a change in physical characteristics of
the matrix. Immobilization may involve physical/chemical
processes that do more than simply entrap the contaminants.
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Solidification alone is not included as a treatment
technology under the Superfund definition of immobilization
because it does not satisfy the statutory preference for
treatment to reduce the toxicity, mobility, or volume (TMV) under
Superfund. The term "solidification" implies a treatment
technology which is intended to produce a monolith for purposes
of structural integrity. Since the principal purpose of
solidification is structural integrity, it does not qualify as
treatment under Superfund for purposes of reduction of TMV.
Solidification performed in conjunction with stabilization (i.e.,
solidification/stabilization), however, would satisfy the
preference for treatment under Superfund and falls within the
Superfund program's definition of immobilization.
IMMOBILIZATION AS A TREATMENT ALTERNATIVE
Concerns have been raised regarding the types of
immobilization that provide for adequate protection. The
principal reason for these concerns rest on the fact that
immobilization is not generally considered a destructive
technique but rather prohibits or impedes the mobility of
contaminants.
Although experts are in general agreement regarding the
effectiveness of immobilization for most inorganics and metals,
the effectiveness of immobilization for organics cannot be
predicted without testing. Furthermore, the testing methods
available (i.e., leachability tests) provide different types of
information on the mobility of contaminants depending on the
test. For these reasons, Superfund has developed general
guidelines for evaluating and selecting immobilization taking
into consideration the testing methods currently available,
scientific understanding to date, and the NCP expectations
regarding treatment.
The preamble to the NCP (55 FR Page 8701, March 8, 1990)
provides the following guidance regarding treatment
effectiveness:
"...The Superfund program also uses as a guideline for
effective treatment the range 90 to 99 percent reduction in
the concentration or mobility of contaminants of
concern.... EPA believes that, in general, treatment
technologies or treatment trains that cannot achieve this
level of performance on a consistent basis are not
sufficiently effective and generally will not be
appropriate."
The use of any treatment technology, including immobilization,
needs to be weighed against this policy and current knowledge
regarding the technology application.
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SDPERFUND POLICY ON USE OF IMMOBILIZATION
This guide provides Agency policy on the use of
immobilization for treatment in view of concerns that have been
raised regarding technology performance primarily for organics.
The Superfund policy is as follows:
Immobilization is generally appropriate as a treatment
alternative only for material containing inorganics, semi-
volatile and/or non-volatile organics. Based on present
information, the Agency does not believe that immobilization
is an appropriate treatment alternative for volatile
organics. Selection of immobilization of semi-volatile and
non-volatile organics generally requires the performance of
a site-specific treatability study or non-site-specific
treatability study data generated on waste which is very
similar (in terms of type of contaminant, concentration, and
waste matrix) to that to be treated and that demonstrates,
through Total Waste Analysis (TWA), a significant reduction
(i.e., a 90-99 percent reduction) in the concentration of
chemical constituents of concern .
The need for treatability study data and the importance of
conducting appropriate leachability tests as part of the study,
are important parts of this policy statement. Treatability
studies to demonstrate the effectiveness of treatment of organics
is needed since we do not believe that we can predict the degree
of performance which may be provided without such testing.
Although immobilization has a long history of application for
inorganics, treatability testing may also be advisable for site
specific cases for both inorganics and organics constituents
where we have insufficient data.
EPA believes that given the uncertainty associated with
immobilization of organics, the most stringent leachability test
available (i.e., TWA) should be used to demonstrated the
effectiveness of the technology. A successful demonstration
using TWA provides a measure of assurance regarding the
leachability of the organics. TWA does not mirror environmental
conditions, however, and does not provide information on the
protectiveness under specific management scenarios for the
immobilized product. One or more other leachability tests may
The 90-99 percent reduction in contaminant concentration
is a general guidance and may be varied within a reasonable range
considering the effectiveness of the technology and the clean-up
goals for the site. Although this policy represents EPA's strong
belief that TWA should be used to demonstrate effectiveness of
immobilization, other leachability tests may also be appropriate
in addition to TWA to evaluate the protectiveness under a
specific management scenario.
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also be used in conjunction with TWA to ensure that the remedy is
protective and can meet the remediation levels for the site-
specific conditions.
Immobilization is not currently viewed as an effective
treatment method for volatile organics since these compounds will
be released during treatment as well as following treatment.
Alternative treatment methods should be evaluated to destroy or
remove the volatile organics to remediation levels either prior
to or concurrently with immobilization. A treatability study
will be needed to demonstrate the effectiveness of the
destruction or removal treatment technology through measurement
of emissions.
The Superfund policy on immobilization is based on current
knowledge with regards to immobilization effectiveness. This
policy may change in the future as we gain knowledge on the use
of immobilization and leachability testing.
POLICY ANALYSIS
The immobilization policy focuses principally on the
appropriate use of the technology as a treatment alternative.
The performance of the technology against site specific
remediation goals also needs to be considered in the evaluation
of the treatment technology.
The policy is broken down into various components to clarify
when immobilization will and will not be considered to constitute
treatment to reduce TMV under Superfund:
Immobilization generally constitutes treatment of wastes to
reduce TMV in the following circumstances:
o Immobilization of inorganics.2
o Immobilization of semi-volatile and non-volatile
organics contaminants of concern where a treatability
study was performed during the RI/FS or is planned
during the RD/RA, and the performance achieved or
performance goal is generally 90 percent reduction or
greater of the contaminant concentration or mobility
using TWA before and after treatment.
Treatability tests for immobilization of inorganic wastes
may be appropriate in situations where insufficient data is
available to support remedy selection or implementation.
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o Immobilization of semi-volatile and non-volatile
organics where non-site-specific data (treatability or
full scale operational data) are available for similar
wastes (in terms of contaminants, concentration, and
waste matrix), and the performance achieved was
generally 90 percent reduction or greater in the
concentration or mobility of contaminants of concern
using a TWA before and after treatment. The reference
for the treatability study report and a discussion of
the data applicability at this site was provided.
Immobilization is not deemed to constitute treatment to
reduce TMV in the following circumstances:
o Immobilization of volatile organics.3
o Immobilization of semi-volatile and non-volatile
organics where a treatability study producing data
meeting the above criteria is not performed, planned
and/or referenced.
ANTICIPATED APPLICATIONS OF IMMOBILIZATION
Immobilization is most commonly accepted as an appropriate
remedy for wastes which contain only inorganics or high levels of
inorganics in combination with semi- and/or non-volatile organics
which would not in themselves result in a waste being deemed a
principal threat. For example, a waste may contain elevated
levels of lead and a low-level concentration of a relatively
immobile organic (e.g. PCBs). In such a case one could
immobilize the waste for the metal but the organic might not be
targeted for treatment since it is at levels at which engineering
controls would be more appropriate. A treatability study for the
organics would not be needed unless we were attempting to achieve
a significant degree of treatment (e.g., 90 percent or greater
reduction in mobility) for purposes of protectiveness. A
treatability study would need to be conducted, if the organics
were of concern and immobilization was being used to treat those
constituents. A treatability study would also be needed for the
inorganics if insufficient information is available to support
the remedy decision for these constituents.
This general statement does not apply to carbon
adsorption of volatile emissions which is followed by carbon
regeneration or treatment. Carbon adsorption has found wide
acceptance for volatile organic control from air emission sources
and waste water treatment facilities.
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Although treatment of high levels of organics may be
achievable with immobilization, the Agency is recommending that
alternative treatment technologies be evaluated in addition to
immobilization, or that treatment trains (which combine pre-
treatment or concurrent treatment to destroy or remove the
organics together with immobilization) be evaluated. Treatment
technologies which have found application to organic wastes
include destructive or removal technologies such as thermal
destruction, thermal desorption, solvent extraction, etc. If
pre-treatment or concurrent treatment is evaluated to address the
organics, the technology should generally be able to achieve a
significant reduction of the organics constituents (i.e., 90
percent reduction or greater or a level that is deemed protective
under the reasonably expected use scenarios).
Since immobilization is not currently considered a viable
treatment alternative for volatile organic materials, an
alternative treatment method to immobilization (i.e., use of a
pre-treatment or concurrent treatment method) should be used to
remove or destroy the volatile organics to remediation levels.
Treatability study data are required to demonstrate the
destruction or removal of the volatile organics to these levels.
EXAMPLES
Examples of immobilization which constitute treatment:
o The waste matrix contains inorganics at concentrations
that represent a principal threat and high molecular
weight organics that are low-level threat wastes since
they are near above unrestricted use levels and are
relatively non-mobile under the current and future
environmental conditions. The disposal of the
treatment product would generally require engineering
controls since the organics would generally be above
levels of concern. Selection of immobilization would
constitute treatment to reduce TMV for the inorganic if
it met the remediation goals for the inorganics since
the waste warrants treatment solely due to the presence
of inorganics.
o The waste matrix contains mobile semi- and non-volatile
organics at concentrations that represent a principal
threat. A treatability study is conducted that shows
that the concentration or mobility of the organics is
reduced 90 percent or greater by using TWA before and
after immobilization. The treatability study is
documented in the ROD. Immobilization of the organics
constitutes treatment to reduce TMV since a
treatability study verified its probable performance
which was documented in the ROD.
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o The waste matrix contains inorganics at levels deemed
appropriate for treatment (i.e., principal threat) and
semi- and non-volatile organic contaminants at levels
deemed appropriate for containment (i.e., low-level
threat). Treatment of the both types of wastes is
selected based on economies of scale (cost
effectiveness) and treatability study data which
demonstrate a 90 percent reduction in the concentration
or mobility for both inorganics and organics of
concern. Immobilization of the organics and inorganics
constitutes treatment to reduce TMV because a
treatability study was conducted and documented showing
effective treatment of the organics.
Examples of immobilizations which generally do not
constitute treatment to reduce TMV:
o The waste matrix contains inorganics that due to
mobility and concentration result in the waste matrix
being deemed a principal threat and volatile organics
which result in emissions above levels that are
protective. Immobilization would generally count as
treatment to reduce TMV for the inorganics but not for
the volatile organics which would volatilize during the
immobilization process and may continue to volatilize
after completion of the remedy. Pre-treatment to
remove or destroy the volatile organics to remediation
levels established in the ROD is generally required.
o The waste matrix contains mobile semi- and non-volatile
organics at levels which constitute a principal threat.
A treatability study was not conducted, treatability
study data of similar waste was not documented in the
ROD, and a treatability study is not planned post-ROD.
Immobilization would generally not constitute treatment
to reduce TMV in this situation since the waste
warrants treatment due to the presence of the organics
and a treatability study was not performed, planned, or
documented.
RCRA LAND DISPOSAL RESTRICTIONS
CERCLA remedial actions must comply with the requirements of
the Resource Conservation and Recovery Act (RCRA) when they are
determined to be applicable or relevant and appropriate
requirements (ARARs) unless a waiver is justified. Potential
ARARs for CERCLA responses include the RCRA land disposal
restrictions (LDRs) established under the Hazardous and Solid
Waste Amendments (HSWA). The LDRs prohibit the land disposal of
restricted RCRA hazardous wastes unless these wastes meet
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treatment standards specified in 40 CFR Part 268, meet the
minimum technology requirements during a national treatment
capacity extension, or satisfy the requirements of one of the
other available compliance options (i.e., treatability variance,
equivalent treatment method, no migration demonstration, or
delisting).
While immobilization may be treatment to reduce TMV, it may
not be able to comply with the LDRs, which are based on best
demonstrated available technology (BDAT). In setting BDAT, the
Agency can decide that BDAT involves destroying or recovering the
hazardous constituents, or that decreasing the mobility
represents BDAT. To date, immobilization has been selected as
BDAT only for metals. Immobilization is not generally
appropriate for compliance with existing BDAT standards for
organics (40 CFR Part 268.43) because it serves to dilute the
waste, lower the effectiveness of the analytical method, and not
significantly lower the amount of hazardous constituents present.
Immobilization of organics does have a role in the
treatability variance process for contaminated soil and debris.
The fact sheet entitled: Superfund LDR Guide #6A (2nd Edition)
Obtaining a Soil and Debris Treatabilitv Variance for Remedial
Actions, Superfund Publication 9347.3-06FS, September 1990 should
be consulted for guidance on applying this variance.
The evaluation method specified in Superfund LDR Guide #6A
for the immobilization of organic waste (first foot-note on page
two) has changed since the issuance of the guidance. The
September 1990 guidance specified the "TCLP method" but should
read TWA. The revised foot-note should read:
"TWA should be used when evaluating wastes with relatively
low levels of organics that have been treated through
immobilization."
As stated previously, TWA is believed to provide a more stringent
test of the immobilization and the potential degree of chemical
interaction which may have occurred.
The treatability variance guidance for soil and debris (as
modified above) will apply on a case-by-case basis until final
LDR soil and debris standards are issued.
ROD DOCUMENTATION
The Record of Decision (ROD) should indicate clearly what
materials are targeted for treatment by immobilization and the
rationale that supports the selection of immobilization. The
following information should be provided in the ROD for
immobilization to be characterized as treatment to reduce TMV:
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o Type of waste (i.e., non-volatile organics, semi-
volatile organics, volatile organics, or inorganics),
o Constituents in the waste to be remediated by
immobilization,
o Treatability study results (literature reference and
results of site-specific studies) which demonstrate 90
percent reduction or greater in contaminant
concentration or mobility using TWA.
o Treatability study results that demonstrate the
effectiveness of immobilization to achieve remediation
levels.
This information should be provided in the "Selected Remedy"
section of the ROD Decision Summary to ensure that it is
documented appropriately. This information also should be
provided in the "Description of the Alternatives", "Summary of
Comparative Analysis of Alternatives" and the "Selected Remedy"
sections of ROD. Please refer to the Interim Final Guidance on
Preparing Superfund Decision Documents (OSWER Directive 9355.3-
02, November 1989) for additional information on ROD
documentation.
FOR FURTHER INFORMATION
The appropriate Regional Coordinator for each Region located
in the Hazardous Site Control Division/Office of Emergency and
Remedial Response or the CERCLA Enforcement Division/Office of
Waste Programs Enforcement should be contacted for additional
information.
NOTICE: The policies set out in this memorandum are
intended solely as guidance. They are not intended, nor can
they be relied upon, to create any rights enforceable by any
party in litigation with the United States. EPA officials
may decide to follow the guidance provided in this
memorandum, or to act at variance with the guidance, based
on an analysis of specific site circumstances. The Agency
also reserves the right to change this guidance at any time
without public notice.
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EXAMPLE ROD
The final ground water Record of Decision for the Mystery
Bridge Site has been included in this portion of your handbook to
serve as an example of a well-prepared decision document. It is
not a "model ROD" (see ROD checklists for standard content and
language) but represents a concise well-written document which
clearly outlines the history of the site, current problems posed
by site contamination, the options considered to address the
problems, and the reason/rationale for selecting a particular
alternative. Editorial notes/comments have been inserted
throughout the text to highlight current program policies and
guidance as it relates to ROD documentation.
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I. SITE NAME, LOCATION AND DESCRIPTION
The Mystery Bridge Road/U.S. Highway 20 (Mystery Bridge) Superfund site (Figure 1) is
located in Section 5, Township 33N, Range 78W 6th P.M. in Natrona County, one mile east of
Evansville, Wyoming. The site includes two residential subdivisions (Brookhurst and Mystery
Bridge) and an industrial area to the south where certain hazardous materials have been used.
The site is bordered on the north by the North Platte River, on the west by the Sinclair/Little
America Refining Company (LARCO), and on the south by U.S. Highway 20. Mystery Bridge
Road and the Mystery Bridge subdivision extend along the eastern perimeter of the site.
Topography of the area varies from flat or gently sloping to slightly rolling. The slope of the
land surface is less than 2 percent but ranges between 7 and 25 percent along the banks of
the North Platte River. The 100- and 500- year floodplains are within 50 to 100 feet of Elkhorn
Creek and the North Platte River. Because of upstream reservoir regulation, the relatively large
channel capacity of the river and rare heavy precipitation events, the North Platte River does
not have an extensive history of flooding.
Drainage is mainly overland flow to man-made diversion structures and to Elkhorn Creek.
Elkhorn Creek is a perennial stream that crosses the site and flows in a northeasterly direction
into the North Platte River. Water from Elkhorn Creek is used for washing equipment at
industrial facilities. During the summer, water is diverted for irrigation of nearby fields.
The Mystery Bridge site is underlain by an alluvial aquifer which previously served as a water
supply to all of the homes in the area. After discovery of organic compounds in water from this
aquifer, all but six of these homes began using other water sources. Currently only two wells in
the residential area are being used to provide drinking water. The alluvial aquifer is also used
for fire fighting by KNEnergy, Inc. (KN). The uppermost bedrock aquifer, the Teapot Sandstone
formation, provides water to a number of industrial wells in the area of the site. Except for
ground water, no other natural resources on the site are used. The North Platte River is used
for recreational fishing.
The residential area, located on the northern two thirds of the site, consists of 125 lots which
range in size from two to five acres. Houses were constructed on approximately 100 of these
lots between 1973 and 1983. According to population data collected in 1987, approximately
400 people lived within the Brookhurst subdivision. In addition, approximately 250 people
comprised the work force for the industrial properties bordering the residential area. Within a
1 -mile radius of the study area, the total work daytime population is approximately 1000 people.
The population within a 3-mile radius was approximately 3000 people, which included 2160
people in the community of Evansville.
An industrial area is located along the southern perimeter of the site to the south of the
Burlington Northern Railroad (BNRR) right-of-way and north of the highway. Present industrial
operations at the site include companies which provide oil field services, bulk fuel storage for
local delivery, natural gas processing and compressing, and supply commercial chemicals.
Several petroleum refineries operate to the west of the site. Other businesses located along
U.S. Highway 20 include truck sales, grading, moving and storage, and public utilities.
Past and present surface and subsurface storage units and other structures at the site include
several underground and above ground storage tanks, abandoned drums, an unlined waste
pond and a concrete lined waste pond. Although several of the units have been removed,
these features have released contaminants from the industrial facilities at the site and are
discussed in detail in the next section.
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II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
Initial Investigations
In August of 1986, residents complained of poor air and water quality in and around the
residential subdivisions. As a result, the Wyoming Department of Environmental Quality
(WDEQ), the Natrona County Health Department and the Office of Drinking Water in EPA
Region VIII began an investigation of the site. Results of early sampling activities indicated
organic compounds in residential wells and tap water. Residents were advised not to use their
well water for drinking or food preparation purposes. In the same year, the State of Wyoming
began providing bottled water to residents. Under the Superfund Removal Program, EPA took
over the lead responsibility for removal activities including providing bottled water. As part of
the removal program, EPA also installed monitoring wells and conducted sampling programs to
further investigate the release of contaminants and gather information to evaluate the need for
further removal action.
The Agency for Toxic Substances and Disease Registry (ATSDR) assessed the public health
risk posed by volatile organic compounds in the ground water at the site. ATSDR determined
that there was an imminent and significant health threat to site residents and that if action were
not taken within one year, the levels of contaminants would increase the lifetime cancer risk for
individuals drinking well water from the area.
In March 1987, EPA began an Expanded Site Investigation (ESI) to further define the nature
and extent of contamination in air, soil, surface water and ground water at the site and to
respond to community concerns. The ESI delineated several potential plumes of ground water
contamination and identified several potential sources of contaminants. Based on the findings
of the ESI, the Mystery Bridge site was proposed for the National Priorities List (NPL) in June of
1988. Listing of the Mystery Bridge site on the NPL was finalized on August 28,1990.
The ESI concluded that one or more contaminated ground water plumes originate near the
Dow/DSI property, and that another ground water plume resulting from the release of aromatic
hydrocarbons originates near the KN facility. The report also concluded that soils at the Dow
Chemical Company and Dowell-Schlumberger Inc. (Dow/DSI) facility were contaminated and
soils at KN could be contaminated. A third major plume was identified as entering the
subdivision from the LARGO property to the west.
The LARCO facility is under the authority of the Resource Conservation and Recovery Act
(RCRA) and was not investigated as part of the CERCLA activities at the Mystery Bridge site.
The contamination associated with the LARCO facility is being addressed through a unilateral
3008(h) corrective action order issued on December 1,1988 on which LARCO and EPA are
negotiating a consent decree. The contaminated ground water (referred to as the RCRA
plume) is believed to be made up of floating petroleum/hydrocarbon products.
Based on an imminent and substantial endangerment to public health revealed by the ESI, EPA
decided to supply an alternative permanent water system for the subdivision. The water supply
project was separated into two phases: Phase I included the design and construction of a
water transmission line from the municipal water supply in Evansville to the site and a
distribution system throughout the residential area; Phase II involved upgrading the Evansville
water filtration facility and included the design and construction of a new water intake and its
corresponding pump station, a new transmission line from the new intake to the Evansville
water filtration facility, and a new sedimentation basin. Phase II was required because the
existing intake was below the Casper wastewater treatment plant discharge and the water
quality was unacceptable. The system was put into operation in January 1989.
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Concurrent with the initial scientific studies, EPA also conducted research to identify potentially
responsible parties (PRPs), parties who may be liable pursuant to CERCLA, for the clean up of
contamination at the site. Notice letters regarding removal actions and remedial activities were
sent in late 1986 and 1987 to various PRPs identified including Dow Chemical Company,
Dowell-Schlumberger, Inc., and KNEnergy, Inc.
Pentachloraphenol (PCP) was detected in two soil samples and several wells located on the
BNRR right-of-way. Over 60 abandoned 55-gallon drums were also found on the property.
Analysis of samples from the drums indicated that 11 of the drums contained aromatic
hydrocarbons and other chemical compounds. These drums were relocated to a BNRR freight
building. The remaining drums were found to contain typical trash and were disposed of by
WDEQ. In 1988, a soil contamination study conducted at the BNRR property concluded that
soil underlying the drums was not contaminated.
Removal Actions
In December 1987, KN and Dow/DSI each entered into Administrative Orders on Consent to
perform removal actions at their respective facilities. Dow/DSI and KN agreed to take
immediate actions to control suspected sources of ground water contamination on their
respective properties and to prevent further migration of contaminated ground water into the
subdivision.
Dow/DSI: The Dow/DSI facility uses mobile mounted pumps, tanks and other associated
equipment to perform oil and gas production enhancement services for the oil and gas
industry. Dow/DSI performs its own truck repair and stores solvents in drums on site.
A gravel leach sump for disposal of truck wash water located on the western portion of the
property had been in operation since shortly after the facility began operations. The wash
water is believed to have contained chlorinated solvents. Also located on the western part of
the property, a 1000-gallon underground oil/water separator tank was used to separate oil film
and solids washed from trucks. Separated wash water left the separator and flowed through a
vitreous tile drain to the leach sump system. A toluene storage area was located at the north
end of the facility. Contaminants were released from both the wash water disposal system and
toluene storage area.
Because of these releases and the resulting contamination, and in accordance with the
Administrative Orders on Consent, Dow/DSI prepared an Engineering Evaluations/Cost
Analysis (EE/CA) report to document the extent and nature of the releases of contaminants,
and to propose expedited removal actions to control migration of contaminants and eliminate
sources of contaminants beneath and adjacent to their property. As a result of drilling and
sampling activities at the Dow/DSI facility in 1987, several volatile halogenated organic (VHO)
soil contaminants were identified in the ground water and soil near the abandoned chlorinated
sump area. The VHO group includes chlorinated organic compounds. The EE/CA prepared
by Dow/DSI evaluated removal technologies and recommended a removal action that was then
implemented.
Removal activities at the Dow/DSI facility began in January 1988. This removal included the
excavation and off-site landfilling of approximately 440 cubic yards of contaminated surface
soils from the chlorinated sump area. The oil/water separator, the decommissioned waste oil
tank and portions of the vitreous tile drain were also removed from the site. A soil vapor
extraction (SVE) system was used in the chlorinated sump area and removed over 300 pounds
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of contaminants from the soil. Almost 6,000 pounds of solvents were removed from soils from
the toluene storage area using a SVE system.
KN: KN has operated a natural gas fractionation, compression, cleaning, odorizing, and
transmission plant at the site since 1965. Operational maintenance activities are performed on-
site.
Originally constructed as an earthen impoundment, a flare pit was used to collect spent
material generated by the facility. Materials that may have been placed in the flare pit include:
1) crude oil condensate; 2) absorption oil; 3) emulsions, antifoulants, and anticorrosive agents;
4) liquids accumulated in the flare stack; 5} potassium hydroxide treater waste; and 6}
lubrication oils and blowdown materials from equipment in the plant. In October 1984, the
western half of the impoundment was backfilled and a new concrete lined flare pit was
constructed on the eastern half. Use of the flare pit was discontinued and the pit was
decommissioned in 1987. Waste streams formerly collected in the flare pit were rerouted into
above storage tanks for temporary storage or recycling.
A catchment area, a low spot in the ground just west of Elkhorn Creek, collected surface run-off
water containing contaminants from the plant area and steam condensate from the dehydration
unit. Various activities were undertaken by KN to reroute materials away from this area in 1984.
In 1965, an underground pipe burst during facility start-up and 5,000 to 10,000 gallons of
absorption oil were injected under pressure into the ground beneath the process area.
Absorption oil is used at the KN processing facility to remove impurities from the natural gas
stream. Other releases occurred between 1965 and 1987 in the form of small leaks and spills
near the flare pit and catchment area.
Because of these releases and the resulting contamination, and in accordance with the
Administrative Order on Consent, KN prepared an EE/CA report. An investigation was
conducted as part of the EE/CA for removal actions at the KN facility. A soil vapor survey was
conducted in the vicinity of the flare pit, and soil boreholes and ground water were sampled.
Additional samples were collected from soils between the concrete flare pit and the flare stack,
and also beneath the concrete flare pit. Several aromatic hydrocarbon contaminants were
identified in the soils and ground water near the flare pit. Benzene, ethylbenzene, toluene and
xylenes (BETX) are included in the aromatic hydrocarbons group. A floating layer of BETX
contaminants was identified during subsequent ground water sampling at the KN facility.
Based on additional drilling and sampling, aromatic hydrocarbons were identified within the
boundaries of a section of soil that is stained by what is believed to be absorption oil from past
releases in the process area and flare pit location. The stained soil on the KN property extends
across the northeastern portion of the Dow/DSI property, through the railroad right-of-way and
slightly into the residential area.
In November 1989, removal actions designed to remove BETX contaminants from the ground
water and soil beneath the KN facility began. Pursuant to this removal action, volatile BETX
contaminants are being removed from the ground water and soil using a SVE system and a
ground water treatment system. As of July 31,1990, the KN removal system had recovered
approximately 6,000 gallons of BETX contaminants and has extracted approximately 135
pounds of benzene from the soils and ground water beneath the KN facility.
Remedial Investigation/Feasibility Study (RI/FS)
In December 1987, an Administrative Order on Consent was issued to Dow/DSI and KN
requiring them to conduct a Remedial Investigation/Feasibility Study (RI/FS) to characterize the
extent of contamination and identify alternatives for cleaning up the site. The RI/FS report,
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which was completed in June 1990, concluded that two plumes of contaminated ground water
originate in the industrial area south of the subdivision and are migrating through the
subdivision in a northeast direction. The first of these plumes is contaminated with VHO
compounds (referred to as the VHO plume), and extends from the Dow/DSI facility to the North
Platte River. The second plume is contaminated with BETX compounds (referred to as the
BETX plume), and extends from the KN facility to the BNRR property and possibly into the
subdivision directly north of the KN facility. In addition, a layer of BETX contaminants
originating at the KN facility and extending slightly into the subdivision was found floating on
the ground water.
PCP contamination near the BNRR property that was identified during the ESI was not detected
in subsequent ground water sampling conducted for the RI/FS. However, EPA will further
address the PCP contamination during activities conducted for the second operable unit for the
site which will evaluate contaminant source areas as discussed in Section IV.
The RI/FS also identified areas of contaminated soils related to the industrial properties at the
site including Dow/DSI, KN, Van Waters and Rogers, NATCO, Sivalls, Permian, and Mobile
Pipeline. Much of this soil has been removed or cleaned up as part of the removal actions
described above. However, some underground soil contamination remains in the industrial
area of the site. This contamination will be addressed during the studies conducted for
contaminant source areas of the Mystery Bridge site (see Section IV).
As part of the RI/FS, in September 1989, EPA prepared a baseline risk assessment (BRA) to
estimate potential health and environmental risk which could result if no action were taken at
the site. The BRA indicated that exposure to ground water could result in significant risks due
to contaminants at the site. Details of the BRA are summarized later in Section VI.
The RI/FS, completed in June 1990, suggested that ground water plumes of VHO compounds
emanating from the Dow/DSI property and BETX compounds emanating from the KN property
are not commingled in the area downgradient from the Dow/DSI and KN facilities. The data
also suggested the VHO plume could be commingled with the RORA plume. Since the most
recent data contained in the RI/FS was from ground water samples taken in September and
October 1989, EPA requested the data be updated prior to issuing this ROD to determine if
these conditions had changed.
In July 1990, ground water samples from 20 wells were collected by consultants for Dow/DSI
(with split samples obtained by EPA and consultants for KN) and analyzed for selected VHO
and BETX compounds. The primary objectives of this sampling were to further assess possible
commingling of the contaminant plumes and to investigate the current degree of contamination
as it may have been affected by the ongoing KN removal action. Results of the July sampling
suggest that there is no current commingling of the VHO plume with the BETX plume nor the
VHO plume with the RORA plume. The July 1990 data are somewhat conflicting with historical
data with respect to BETX compounds in the ground water northeast of the KN property line
and the volume of the BETX plume appears to be greater than that estimated in the RI/FS.
III. HIGHLIGHTS OF COMMUNITY INVOLVEMENT
Community interest in problems at the Mystery Bridge site became very intense in late 1986
when site contamination problems first surfaced and the ATSDR advisory was issued. Early
public meetings, many of which were attended by as many as 100 people, often became highly
emotional encounters between concerned residents and public officials. Media coverage was
extensive, including coverage by local and State newspapers and television stations, as well as
some national television coverage.
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State legislators and Congressional staff members took a great interest in site activities. The
community's letter-writing campaign extended to the White House.
<3 *j Initial community involvement was coordinated by an EPA removal program community
™ tf relations coordinator, as well as by an EPA field liaison, EPA's representative in Casper, and
V Q the Emergency Response Branch's On-Scene Coordinator for the site.
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EPA's removal community relations coordinator prepared a Community Relation Plan in
December 1986. The Plan was revised in November 1988 by the remedial community
involvement coordinator.
Between December 1986 and July 1987, EPA held five public meetings. From December 1986
through October 1989, EPA issued five Fact Sheets and 14 Information Updates. In January
1990, EPA distributed a Fact Sheet on the risk assessment for the site. In addition, EPA
provided for public comment on work plans, sampling plans, the Community Relations Plan,
alternative water supply options, and other key documents throughout site activities. EPA
issued responsiveness summaries for comments received during these comment periods.
1 From April 1987 through June 1988, EPA representatives participated in a Governor's Task
Force and Oversight Committee on a regular basis. From June 1988 through October 1989,
EPA worked with WDEQ and the Natrona County Health Department to continue a monthly
forum for discussing issues with community members.
?To further fulfill the requirements of CERCLA/SARA Section 113 (k)(2)(i-v) and Section 117, the
Administrative Record file for the removal actions was established at EPA's Denver office and at
EPA's Wyoming field office in Casper. EPA also provided a copy of the record to one
community group who requested it under the Freedom of Information Act (FOIA). The
i Administrative Record for the remedial activities was established at the Natrona County Library
I in Casper and in EPA's Denver office.
i The Proposed Plan for OU 1 was issued on July 3,1990 with a one-quarter page advertisement
placed in the Casper Star Tribune on July 1,1990 outlining remedial alternatives and
announcing the public comment period and public meeting. The public comment period was
open from July 5 to August 3,1990. The public meeting was held July 18,1990 at the Casper
City Council Chambers. A transcript of the public meeting is included in the Administrative
Record.
Approximately five community members attended the Proposed Plan public meeting. Two oral
comments were received at the public meeting and three sets of written comments were
received during the public comment period.
Details of community involvement activities and responses to official public comment on the
Proposed Plan are presented in the Responsiveness Summary attached to this ROD.
IV. SCOPE OF ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
The Mystery Bridge site has been divided into two operable units: one to address ground
water (OU 1) and the other to evaluate contaminant source areas (OU 2). The remedy selected
in this ROD is for the first operable unit and addresses-the contaminated ground water
emanating from the Dow/DSI and KN facilities. This ground water poses the principal threat to
uman health and the environment due to ingestion of and contact with water from wells that
contain contaminants above the Maximum Contaminant Levels (MCLs) established by the Safe
Drinking Water Act.
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EPA will evaluate remaining source areas in OU 2 and, as necessary, will determine whether
further action is required for contaminated subsurface soils in the vicinity of the industrial
properties that were identified during the RI/FS and represent possible continuing sources of
ground water contamination. Questions raised by comments received during the public
comment period regarding the BNRR property will be further evaluated during OU 2.
EPA believes additional consideration of the contaminant source~areas is necessary to ensure
the long-term effectiveness of the ground water dean up. The Rl focused primarily on
contaminated ground water and did not address mechanisms which may transport
contaminants from soils to water. Removal actions for the Oow/DSI and KN facilities prevent
further migration from source areas into residents' ground water. Questions remain concerning
the ability of the removal actions to eliminate sources of contamination. For example, the SVE
and hydrocarbon recovery activities at the site may not be effective on soils below the ground
water. There are also inherent technical difficulties in cleaning the stained soil areas above the
ground water and the floating BETX contaminants.
V. SITE CHARACTERISTICS
Site Geology and Hydrology
The site is located within a narrow strip of Quaternary alluvial floodplain and terrace deposits
along the North Platte River and Elkhorn Creek. The upper 1.5 to 13 feet of the alluvial deposit
is a surficial soil layer which consists of a mixture of sandy silt and clayey silt. The remaining
alluvium ranges in thickness from 13 to 68 feet It is well-sorted coarse to medium sand with
little fine sand and trace amounts of silt and gravel.
Bedrock crops out to the southeast and northwest of the site. In the uppermost 200 to 300 feet
of bedrock the formations are in ascending order 1) Teapot Sandstone, consisting of medium-
to fine-grained sandstone with shale partings and 2) the Lewis Shale, consisting of thick
bedded shale grading into brown sandstone.
The bedrock surface at the site is beneath a layer of alluvium. A clay layer indicating
weathered bedrock was encountered at the contact between the alluvium and bedrock in
almost every borehole. A valley in the bedrock surface that roughly parallels the present
course of Elkhom Creek was also identified. This valley was probably eroded by a former
course of the North Platte River. Bedrock elevations increase on both flanks of the valley. To
the east, this increase is part of a divide separating the site from an adjoining drainage. The
alluvium pinches out in the east, restricting movement of ground water towards the residential
area. The bedrock surface is less regular to the northwest A comparison of bedrock surface
topography to alluvial ground water flow directions shows that the shape of the bedrock valley
significantly affects ground water movement in the alluvial aquifer. The low permeability layer at'
the bedrock surface also appears to confine the contaminants to the upper alluvial aquifer.
The horizontal component of ground water flow within the alluvial aquifer is consistently to the
northeast with only minor and local variations. The flow direction appears to be controlled to a
certain degree by the alignment of the valley in the bedrock surface. Although water level
differences between the alluvium and underlying bedrock have been variable, they generally
confirm the potential for ground water in the bedrock to flow into the alluvium in the valley from
peripheral portions of the local area.
Based on the character of the alluvial materials at the site and on hydraulic tests conducted
within the alluvium, the ground water seepage velocity for horizontal flow within the alluvium
ranges from 0.21 to 4.9 feet per day, with an average value of 2.12 feet per day. The seepage
velocity represents the rate at which dissolved contaminants would be transported with the
-------
ground water in the absence of hydrogeochemical factors such as adsorption onto sand grains
in the aquifer.
There is potential discharge of contaminated ground water from the VHO plume to the North
Platte River over the next few years. Data from the RI/FS indicate that the water quality criteria
for the river will continue to be met because the volume of contaminants will be insignificant
relative to the volume of water in the river.
Nature and Extent of Contamination
The scope of the Rl at the Mystery Bridge site included studies for all media that may be
contaminated. Soils in the residential area, surface water and sediments from Elkhorn Creek,
and air quality at the site were investigated and determined not to be of concern with regard to
contaminant pathways at the site.
Areas of contaminated soils were identified on the industrial properties at the site. This
contamination will be evaluated more fully during the activities conducted for OU 2.
Sources of ground water contamination at the Dow/DSI and KN properties are discussed
below. The pathway of migration for contaminants in both the VHO plume originating beneath
the Dow/DSI facility and BETX plume originating beneath the KN facility is through the shallow
alluvial aquifer moving in a northeasterly direction towards the North Platte River.
Dow/DSI: Potential sources of contaminants at Dow/DSI include 1) a 1000 gallon oil/water
separator, 2) a vitreous drain line, 3) an empty waste oil tank, 4) chlorinated leach sump, and
5) toluene storage area. The first three were removed as part of the Dow/DSI removal action
discussed above.
The ground water plume emanating from Dow/DSI is characterized by elevated levels of VHOs
including the following chlorinated compounds:
1,1-dichloroethene (1,1 DCE);
trans-1,2-dichloroethene (t-1,2 DCE);
trichloroethene (TCE);
tetrachloroethene (PCE);
1,1,1-trichloroethane (1,1,1 TCA); and
1,1-dichloroethane(1,1 DCA).
MCLs and proposed MCLs were exceeded for TCE, t-1,2 DCE and PCE in wells sampled
between 1987 and 1989. Table 1 summarizes data from the RI/FS and ESI reports, and recent
July 1990 sampling for VHO concentrations in monitoring wells considered to be located within
the VHO plume and their MCLs or proposed MCLs. These contaminants were released to the
ground water from equipment washing operations at or near the chlorinated sump on the
western portion of the Dow/DSI facility. A toluene and xylene plume apparently originates at
the former toluene storage area, but is considered of minor importance as the concentrations
are below MCLs.
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The shape and trend of the TCE ground water contamination has been found to be similar to
the ground water plume for total VHO compounds, as TCE is the major constituent in the VHO
group. VHO compounds are highly mobile in the aquifer and contamination from Dow/DSI has
travelled with the northeasterly flow of ground water. The plume of contaminated ground water
with levels exceeding MCLs or proposed MCLs extends below the residential area of the site as
shown on Figure 2. Vertical extent of the VHO contamination is limited to the shallow alluvial
aquifer. The volume of ground water at the site containing VHO contaminants above the MCLs
or proposed MCLs was estimated in the RI/FS report to be 1 096 acre-feet.
KM: Three sources of contamination have been identified on the KN property including: 1 ) the
flare pit, 2) the catchment area and 3) the process area. High concentrations of BETX
compounds have been found in monitoring wells near these sources. These compounds are
believed to be components of absorption oil and other liquids associated with refining activities
at the KN facility. A summary of data for BETX concentrations from the RI/FS and ESI reports,
and recent July 1990 sampling in monitoring wells considered to be located within the BETX
plume and their MCLs or proposed MCLs are provided in Table 2. Recent drought conditions
have lowered the water table, and free hydrocarbons containing BETX compounds have been
found floating on top of the water. Some of this material was recovered by KN as part of the
removal action. A large area of stained soil below the surface remains on KN's property. Final
remediation of this contamination and of the floating hydrocarbons will be addressed as part of
the OU 2 activities.
BETX compounds are less mobile in the aquifer and are present in the ground water near the
source at the KN facility. Migration of the BETX may be inhibited by preferential adsorption to
the soil matrix as well as by biological degradation of adsorbed and dissolved residues. The
contaminated plume of BETX compounds occurs under the KN facility and extends
downgradient of the facility close to the northern property boundary as shown on Figure 3. A
conservative approach to estimating the volume of ground water contaminated with BETX
compounds would be to consider all wells where BETX compounds in excess of their MCLs or
proposed MCLs have ever been detected. This would include several wells on the KN
property, plus wells north of the property line. If the dissolved BETX plume is taken to include
all of these wells, the estimated volume of contaminated ground water would be about 25 acre-
feet rather than 1 0 acre-feet estimated in the RI/FS.
VI. SUMMARY OF SITE RISKS
As part of the RI/FS, EPA prepared a Baseline Risk Assessment for the Mystery Bridge site in
December 1 989. This risk assessment was carried out to characterize, in the absence of
remedial action (i.e., the "no-action" alternative), the current and potential threats to human
health and the environment that may be posed by contaminants migrating in ground water or
surface water, released to the air, leaching through the soil, remaining in the soil, or
bioaccumulating-tfUhe food chain at the site. Figure 4 provides a glossary of the key risk
terms from theteRAhat are used in this section of the ROD.
.
f The risk assessment began by compiling a list of contaminants from the results of the various
A sampling activities that were measured to be above detection limits or above natural
background levels. Thirteen indicator contaminants were selected based on concentrations at
the site, toxicity, physical/chemical properties that affect transport/movement in air, soil and
ground water and prevalence/persistence in these media. These indicator contaminants were
judged to represent the major potential health risks at the site.
11
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Figure 4
Key Risk Terms
Carcinogen: A substance that increases the incidence of cancer.
Chronic Daily Intake (GDI): The average amount of a chemical in contact with an
individual on a daily basis over a substantial portion of a lifetime.
Chronic Exposure: A persistent, recurring, or long-term exposure. Chronic exposure
may result in health effects (such as cancer) that are delayed in onset, occurring long
after exposure ceased.
Exposure: The opportunity to receive a dose through direct contact with a chemical or
medium containing a chemical.
Exposure Assessment: The process of describing, for a population at risk, the
amounts of chemicals to which individuals are exposed, or the distribution of exposures
within a population, or the average exposure of an entire population.
Hazard Index: An EPA method used to assess the potential noncarcinogenic risk. The
ratio of the GDI to the chronic RfD (or other suitable toxicity value for noncarcinogens) is
calculated. If it is less than one, then the exposure represented by the GDI is judged
unlikely to produce an adverse noncarcinogenic effect. A cumulative, endpoint-specific
HI can also be calculated to evaluate the risks posed by exposure to more than one
chemical by summing the GDI RfD ratios for all the chemicals of interest exert a similar
effect on a particular organ. This approach assumes that multiple subthreshold
exposures could result in an adverse effect on a particular organ and that the
magnitude of the adverse effect will be proportional to the sum of the ratios of the
subthreshold exposures. If the cumulative HI is greater, than one, then there may be
concern for public health risk.
Reference Dose (RfD): The EPA's preferred toxicity value for evaluating
noncarcinogenic effects.
Risk: The nature and probability of occurrence of an unwanted, adverse effect on
human life or health, or on the environment.
Risk Assessment: The characterization of the potential adverse effect on human life or
health, or on the environment. According to the National Research Council's
Committee on the Institutional Means for Assessment of Health Risk, human health risk
assessment includes: description on the potential adverse health effects based on an
evaluation of results of epidemiologic, clinical, toxicologic, and environmental research;
extrapolation from those results to predict the types and estimate the extent of health
effect in humans under given conditions of exposure; judgements as to the number and
characteristics of persons exposed at various intensities and durations; summary
judgements on the existence and overall magnitude of the public-health program; and
characterization of the uncertainties inherent in the process of inferring risk.
Slope Factor: The statistical 95% upper confidence limit on the slope of the dose
response relationship at low doses for a carcinogen. Values can range from about
0.0001 to about 100,000, in units of lifetime risk per unit dose (mg/kg-day). The larger
the value, the more potent is the carcinogen, i.e., a smaller dose is sufficient to increase
the risk of cancer.
15
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rntorooo
, Exposure Assessment
•^s
Although exposure pathways were identified for ground water, surface water and sediments,
residential soils, and air media at the site, the risk assessment indicated that only the ground
water pathway could result in significant health risks. Of the 13 indicator contaminants studied
in the BRA, PCE, TCE, 1,1 DCA and benzene were determined to be the primary contaminants
of concern in the ground water pathway.
xBecause of the northeasterly flow of ground water in the alluvial aquifer at the site,
•^contaminants introduced into the ground water below the sources at the southern section of
|the site could be transported across the residential areas. Thus, a significant potential
^exposure pathway involving ground water is likely to exist for the subdivision residences which
jrrently use site ground water for domestic purposes. Ail but two of the residences now use a
j non-contaminated municipal water supply in place of ground water. The pathway for
,, „ ^contaminants is intercepted for residents using the municipal water supply; however, potential
<£ § ^risk of exposure to the ground water contaminants remains. In addition, considering the
> potential for future land development at the site, future residences could potentially be located
on properties currently used by industries. The ground water pathway is therefore likely to be
complete for these future hypothetical residences. Two important exposure scenarios, the
i Current Resident and Future Hypothetical Resident, were developed based on the fact that
ground water is the primary exposure medium at the site.
Intake of contaminants present in ground water could potentially occur via three routes: 1)
ingestion of ground water; 2) dermal contact with water while bathing, showering, cooking or
swimming (also ground water used for outdoor domestic and/or agricultural purposes); and 3)
inhalation of indoor air contaminants volatilized while bathing, showering, or cooking, or that
volatilized and directly accumulated in the living spaces. In addition, use of contaminated
ground water in a home cooling unit (i.e., swamp cooler) could potentially lead to the inhalation
of volatilized contaminants. The contaminant intake equations and values chosen for various
intake parameters were derived from the standard intake equation and data presented in EPA
guidance documents. Chronic daily intakes (GDIs) were estimated in the BRA. Representative
exposure point concentrations were developed from the sampling data for contaminants
measured in EPA monitoring wells in the residential area.
The Reference Dose values (RfD) for a substance represents a level of intake which is unlikely
to result in adverse non-carcinogen health effects in individuals exposed for a chronic period of
time. The RfDs (in mg/kg-day) for the contaminants include: 1,1 DCA = 0.01; 1,1,1 TCA =
0.09; 1,2 DCE = 0.02; PCE = 0.01; xylenes = 2; toluene = 0.3; and ethylbenzene = 0.1.
The slope factor represents the upper 95 percent confidence limit value on the probability of
response per unit intake of a contaminant over a life time (70 years for the analysis in the BRA).
Slope factors used in the BRA for the contaminants (in (mg/kg-day)-1) include: TCE = 0.11; 1,1
DCA = 0.091; PCE = 0.051 and benzene = 0.029.
Toxicfty Assessment
Indicator contaminants present in the ground water include VHO and BETX compounds. The
following discussion comes from the toxicological profiles of these contaminants presented in
the BRA.
VHOs TCE is classified as a group B2 carcinogen (a probable human carcinogen). TCE has
been shown to cause pulmonary adenocarcinoma, lymphoma, and hepatocellular carcinoma in
multiple strains of mice. Subchronic and chronic exposures of animals to TCE appears to
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morooo
result in liver and kidney toxicity. PCE has been classified as a group C carcinogen (a possible
human carcinogen) based upon evidence that the chemical causes hepatocellular carcinoma
in mice. Mouse and rat studies have indicated that PCE is a teratogen and a reproduction
toxin. In addition, both oral and inhalation exposure of laboratory animals to PCE for
intermediate and long-term exposure leads to liver, kidney and spleen toxicity. 1,1 OCA, t-1,2
DCE and 1,1,1 TCA are not demonstrated human carcinogens. 1,1 DCA appears to cause
kidney damage in laboratory animals exposed subchronically via the inhalation route. Rats
exposed to t-1,2 DCE via inhalation developed progressive damage to the lung and fatty
changes in the liver. Chronic inhalation exposure of laboratory animals to 1,1,1 TCA resulted in
hepatoxicity (fatty changes in the liver and increased liver weights).
BETX EPA considers benzene to be a group A carcinogen. This listing signifies that there is
"Sufficient evidence from epidemiologic studies to support a causal association between
exposure and cancer." In sensitive humans, alterations in bone marrow have been shown to
form during short-term exposures to approximately 10 ppm benzene. Several studies have
demonstrated an increased incidence of non-lymphocytic leukemia from occupational
exposure. Intermediate and chronic exposure to benzene can adversely effect the
hematopoietic and immune systems.
Ethylbenzene, toluene and xylenes are classified as non-carcinogens. Ethylbenzene is acutely
toxic to the lung and central nervous system. However, subchronic and chronic exposures of
laboratory animals to this compound cause liver and kidney damage, as well as testicular
toxicity. The teratogenicity of ethylbenzene has also been indicated in rats. A primary target
for toluene toxicity is the central nervous system. In humans acute exposures to 100 ppm of
toluene via inhalation causes fatigue, sleepiness, decreased manual dexterity and decreased
visual acuity. Exposure to high levels of toluene, as occurs in solvent abuse, can result in
permanent central nervous system effects such as tremors, atrophy, and speech, hearing, and
vision impairment. Animal studies indicate that toluene is also a development toxin causing
growth inhibition and skeletal anomalies. Xylene orally administered to animals can result in
central nervous system toxicity and has also been shown to cause ultra-structural liver changes
(although these changes are not necessarily adverse effects). Xylene has also been shown to
be a fetotoxin and a teratogen in mice at high oral doses.
Risk Characterization
The BRA evaluated the potential non-carcinogenic and carcinogenic risks posed by the
indicator contaminants in the various exposure media at the Mystery Bridge site. Carcinogenic
risk is presented as a probability value (i.e., the chance of contracting some form of cancer
over a lifetime). The estimate of carcinogenic risk is conservative and may overestimate the
actual risk due to exposure.
In the risk characterization, the aggregate carcinogenic risk due to ground water indicator
contaminants at the site is compared to an acceptable target risk. The chance of one person
developing cancer per one million people (or 10-") is used as a target value or point of
departure above which carcinogenic risks may be considered unacceptable. The 10* point of
departure is used when ARARs are not available (i.e., no MCLs or proposed MCLs for the
indicator contaminants) or are not sufficiently protective of human health and the environment.
17
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mbnxtt
Carcinogenic Risk. Carcinogenic risk is typically estimated by multiplying the GDI of an
indicator contaminant by its slope factor. A summary of carcinogenic risks for residents living
directly above and using contaminated ground water from the VHO and BETX plumes in the
Current Resident scenario is provided in Table 3. The aggregate carcinogenic risk is 8.1 x 105
for the VHO plume and 4.7 x 1 Qrs for the BETX plume. Total carcinogenic risk due to ground
water consumption exceeded 10* at both the VHO and BETX plumes. The primary source of
risk posed by the VHO plume was PCE and TCE contamination. The major component of the
risk values calculated for the BETX plume were based on the risk due to exposure to benzene.
Carcinogenic risks were also calculated for selected indicator contaminants for residents using
ground water from wells at the Dow/DSI and KN properties in the Future Hypothetical Resident
scenario. These risks, shown in Table 3, also exceeded 10*. The aggregate carcinogenic risk
for the VHO plume was 3.2 x 1 Q-» and 1.7 x 104 for the BETX plume.
Non-Carcinogenic Risks. The ratio of GDI to RfD was computed for each contaminant and the
resulting ratios are summed to give the hazard index. Non-carcinogenic hazard indices were
calculated for both the Current Resident and Future Hypothetical Resident scenarios. Results
indicated the aggregate hazard indices do not exceed unity; therefore, EPA believes that there
is no non-carcinogenic public health threat.
Risks Due to Indoor Air Contamination. There is a high likelihood that the residents who use
contaminated well water are being exposed to indoor organic vapor contaminants that have
volatilized from the well water. This exposure occurs through inhalation of volatilized
contaminants while showering, bathing, or cooking, as well as volatilized contaminants from
home cooling units. Quantitative risk calculations were not done for indoor air because there is
a high degree of uncertainty associated with the generic (non site-specific) and inhalation risk
factors. Although not quantified, this exposure to contaminated indoor air adds additional risk
for subdivision residents using contaminated well water.
Another potential source of site-related indoor air contamination is the direct emanation and
accumulation of volatilized plume water in the living spaces of residences located directly over
the contaminated ground water plumes. The risks from this direct accumulation of indoor
organic vapors is considered to be insignificant when compared to the risks from inhaling
volatilized shower, bath or cooking water.
Environmental Risks
The ecological effects due to releases from industrial areas are not expected to be significant
for three reasons: 1) these industrial areas do not provide habitat resources for wildlife ; 2) the
sampling data for surface water and sediments at Elkhom Creek indicates minor levels of
contamination from the site; and 3) contamination of the North Platte River via ground water
plume discharge is expected to be relatively insignificant due to the high rate of river flow as
compared with the rate of ground water discharge.
VII. DESCRIPTION OF ALTERNATIVES
A feasibility study was conducted to develop and evaluate remedial alternatives for OU 1 at the
Mystery Bridge site. Remedial alternatives were assembled from applicable remedial
technology process options and were initially evaluated for effectiveness, implementability, and
cost. The alternatives meeting these criteria were then evaluated and compared to nine criteria
required by the NCP. In addition to the remedial alternatives, the NCP requires that a no-action
alternative be considered at every site. The no-action alternative serves primarily as a point of
comparison for other alternatives.
18
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Table 3: Carcinogenic Risk Characterization
VHO Plume
Scenario/Pathway
Current Resident
Ingestion
Absorbtion
Aggregate
Future Hvootnetical Resident *
Ingestion
Absorbtion
Aggregate
Benzene
7.0E-07
1 .3E-06
PCE
2.5E-05
8.9E-08
TCE
5.1E-05
1.9E-07
1,1 DCA
2.3E-06
8.5E-09
Methyiene
Chloride
2.5E-07
9.0E-10
-
7.1E-05
2.9E-07
2.5E-04
1.0E-06
-
-
Pathway
Total
7.9E-05
1.6E-06
S.1E-05
3.2E-04
1 .3E-06
3.2E-04
BETX Plume
Scenario/Pathway
Current Resident
Ingestion
Absorbtion
Aggregate
Future Hvoothetical Resident *
Ingestion
Absorbtion
Aggregate;
Benzene
1.4E-05
2.5E-05
PCE
1.3E-06
4.8E-09
TCE
2.8E-06
1.0E-08
1,1 DCA
3.0E-06
1.1E-08
Methyiene
Chloride
8.3E-07
3.0E-09
5.8E-05
1.1E-04
-
-
-
-
Pathway
Total
2.2E-05
2.5E-05
4.7E-05
5.8E-05
1.1E-04
1.7E-04
' selected contaminants only
19
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!
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;l
V
, >oEach remedial alternative acknowledges the removal activities that have occurred or are
_ currently taking place assumes continuation of the ongoing activities. While sources are being
controlled by the removal actions, ground water remains contaminated with VHO and BETX
compounds released from the sources. The remedial alternatives described in this ROD
address this ground water contamination.
A ground water model has been developed to simulate transport of dissolved VHO compounds
through the alluvial ground water system. The model incorporates a variety of physical,
chemical, and biological factors which can affect the rate of contaminant migration through the
aquifer. Known variability and expected uncertainty in these factors were incorporated into the
model by performing 5,000 duplicate model runs with model parameters selected randomly
from within their known or expected ranges. The resulting model runs provided an expected
range of contaminant concentrations over time, from which statistically most-probable
contaminant transport rates could be estimated. Contaminant transport rates were used to
estimate time frames for the remedial alternatives developed in the RI/FS. This transport model
swas not applied to the BETX plume because downgradient migration of BETX compounds from
KN property to the BNRR property appears to be minimal.
^-**"" V.
The(action levejf for remediation are the MCLs and proposed MCLs for the contaminants of
concern. Attainment of these levels will be protective of human health and the environment.
However, EPA recently studied the effectiveness of ground water extraction systems in
achieving specified goals and found that it is often difficult to predict the ultimate concentration
to which contaminants in the ground water may be reduced. The study did find that ground
water extraction is an effective remediation measure and can achieve significant mass removal
of contaminants. Most of the remedial alternatives described in this section include ground
water extraction systems and assume that it is technically feasible to achieve MCLs or
proposed MCLs in the ground water.
Except for the no-action alternative which includes ground water monitoring only, each
alternative includes the following common elements:
Ground Water Monitoring. Ground water monitoring during the remedial activities will be
used to evaluate performance of the remedial action. Monitoring points are anticipated to be
located upgradient of the plume (to detect contamination from other sources), within the plume
(to track the plume movement during remediation), and downgradient (to detect plume
migration). Monitoring points to the west of the VHO plume would be used to evaluate whether
commingling with other plumes occurs in the future. Ground water samples would be analyzed
for site indicator compounds as determined during remedial design. Existing monitoring wells
and possibly additional monitoring wells to be installed would be used for ground water
monitoring. The specific locations and frequency of ground water monitoring will depend on
the remedial alternative selected and site conditions at the time of implementation. Monitoring
would continue after remedial objectives are met to ensure residual contaminants desorbing
into ground water will not exceed MCLs or proposed MCLs in the future.
Temporary Institutional Controls. Temporary restrictions on the construction and use of
private water wells, such as well restrictions in property deeds, well construction permits,
and/or deed notices during remediation would effectively restrict human consumption of
ground water exceeding MCLs and proposed MCLs irvthe residential area until remediation
joalfyor ground water are achieved. Actual institutional controls to be used will be determined
Juririg remedial design. ~~
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rnDrooo
VHO Plume
Seven remedial alternatives for the VHO plume were considered for detailed evaluation and are
described below. Table 4 provides a summary of the alternatives. Alternative V2 contemplated
collection of VHO-impacted ground water and transport to an off-site RCRA treatment facility.
This alternative was eliminated early in the evaluation process because it would be technically
infeasible to implement and would involve costs that would be grossly excessive compared to
its overall effectiveness.
Alternative V1 • No-action with ground water monitoring.
Under this alternative, EPA would take no further action to control the source of contamination.
However, long-term monitoring of the site would be necessary to monitor contaminant
migration. Monitoring using previously installed monitoring wells and residential wells can
easily be implemented.
Because this alternative would result in contaminants remaining on-site, CERCLA requires that
the site be reviewed every five years. If indicated by the review, remedial actions would be
implemented at that time to remove or treat the wastes.
Alternative V1 relies on natural processes in the ground water to reduce VHO levels in the
aquifer. Results of contaminant transport and fate modeling described previously indicated
that the most-probable time required for natural processes to reduce contaminant
concentrations by two orders of magnitude at the downgradient edge of the subdivision (i.e., at
the North Plane River) would be approximately seven years. A two order of magnitude
reduction would result in VHO concentrations below MCLs and proposed MCLs.
Consequently, it is expected that VHO contaminants will have been effectively flushed out of
the aquifer beneath the subdivision within seven years. The ground water would be restored to
a Classification I aquifer suitable for drinking water purposes. There is a minimal chance that
complete flushing would take as long as 19 years.
The present worth cost for Alternative V1 would be $71,000. Since the alternative requires "no-
action", there would be no capital cost. However, operation and maintenance (O&M) costs are
estimated to be $11,000 for ground water monitoring.
Alternative V3 • Extraction of VHO-impacted ground water, aerobic biological treatment of
extracted ground water, and discharge of treated ground water to the North Platte River.
Extraction of ground water with VHO concentrations exceeding MCLs or proposed MCLs
would be accomplished with an extraction well system. Assuming an extraction system of ten
^ wells and a volume of impacted ground water of 1096 acre-feet, extraction would be completed
<§ in one to two years after initiation of the alternative. The actual number of wells could change
as determined by remedial design. The time for remediation could vary depending on several
^ ^ ^factors including the pumping rate and the volume of impacted ground water.
'A sequencing batch reactor system would provide aerobic biological treatment of extracted
ground water and would facilitate destruction of organic constituents. The treatment system
would be expected to volatilize some of the VHO contaminants which would be released to the
atmosphere.
Aerobic biological treatment of ground water would produce a sludge that would require
disposal. An estimated 170 tons of non-hazardous sludge per year would be generated. The
sludge would be expected to meet all RCRA criteria for land disposal.
21
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Table 4: Summary of VHO Plume Alternatives
Component
Common
Elements
Extent of
Ground Water
Extraction
Treatment
Technology
Disposition of
Treated Water
Ground Water
Monitoring
Institutional
Controls
Extraction of Ground
Water with VHO
Concentrations > MCLs
Extraction of Upgradient
Ground Water With VHO
Concentrations > MCLs
Aerobic Biological Treatment
of Extracted Ground Water
Air Stripping of
Extracted Ground Water
Carbon Adsorption of
Extracted Ground Water
Chemical Oxidation of
Extracted Ground Water
Natural Attenuation of VHOs
in Downgradient Plume
In-situ Bioremediation
of VHOs in Downgradient Plume
In-situ Bioremediation
of VHO Plume
Injection of Treated Water
to Up/Downgradient Wells
Discharge of Treated
Water to North Plane River
Discharge of Treated
Water to Elkhorn Creek
Alternatives
V1
X
V3
X
X
X
X
X
V4
X
X
X
X
X
V4A
X
X
X
X
X
V5
X
X
X
X
X
V6
X
X
X
X
X
(X)
X
(X)
V6A
X
X
X
X
X
(X)
X
(X)
V7
X
X
X
(X) » Option or Contingency
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Treated ground water would be discharged to the North Platte River. For cost estimation
purposes, it was assumed that a treatment facility would be located on industrial property. The
discharge would be sampled as necessary to comply with National Pollutant Discharge
Elimination System (NPDES) permit requirements.
Capital cost for Alternative V3 would be over $2 million with O&M costs of $165,000. The
present worth cost would be almost $2.5 million.
Alternative V4 - Extraction of VHO-impacted ground water, air stripping of extracted
ground water, and discharge of treated ground water to the North Platte River.
This alternative is similar to Alternative V3, except that extracted ground water would be treated
in an air stripping tower on-site to remove VHOs. In the air stripping process, VHOs are
transferred from the water phase to the air phase and discharged to the atmosphere. Air
stripper vapor discharge would be sampled as necessary to comply with Wyoming Air Quality
Standards and Regulations.
Alternative V4 would involve capital costs of over $1 million and O&M costs of $129,000. The
present worth cost would be approximately $1.3 million.
Alternative V4A - Extraction of VHO-impacted ground water, carbon adsorption treatment
of extracted ground water, and discharge of treated ground water to the North Platte
River.
This alternative is similar to alternatives V3 and V4, except that extracted ground water would
be treated in a carbon adsorption system on-site to remove VHOs. In the carbon adsorption
process, VHOs are adsorbed onto activated carbon, thereby removing them from the ground
water. The spent carbonjsl^ical^ thermally or chemically regenerated for reuse.
Present worth cost for this alternative would be almost $1.4 million. Capital cost would be $1.2
million with O&M costs of $128,000.
Alternative V5 • Extraction of VHO-impacted ground water, chemical oxidation of extracted
ground water, and discharge of treated ground water to the North Platte River.
This alternative is similar to alternatives V3, V4, and V4A, except the chemical oxidation of
contaminants in extracted ground water would be implemented on-site using controlled reactor
vessels. A retention time of jtpproximatelyrjrfew minutes^should be sufficient to treat influent
7^ ground water VHO concentrations to the required levels!
Capital cost for Alternative V5 would be $1.1 million with O&M costs equal to $282,000.
Present worth cost is $1.7 million.
Alternative V6 - Extraction in the upgradient portion of the plume which contains the
highest VHO concentrations, air stripping of extracted ground water, discharge of treated
ground water to Elkhorn Creek or reinjection upgradient or downgradient of the extraction
well system, and natural attenuation in the downgradient portions of the plume.
An extraction well system would remove ground water with VHO levels exceeding MCLs and
proposed MCLs in the upgradient portion of the plume. Assuming one extraction well and a
volume of VHO-impacted ground water in the upgradient portion of the plume of 57 acre-feet,
extraction should be completed in about one year following implementation of the remedy. The
actual number of extraction wells could change as determined by the remedial design.
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Extracted ground water would be treated to remove VHOs in an air stripping tower on-site as
described for Alternative V4. Concentrations of VHOs in the treated ground water would be
reduced to MCLs or proposed MCLs.
Treated ground water would be reinjected upgradient or downgradient of the extraction well.
Downgradient injection points could accomplish the following objectives: 1) provide additional
hydraulic containment of the upgradient portion of the VHO plume being extracted; 2)
minimize the possibility of any interaction related to VHO remediation efforts with nearby
plumes and/or free BETX contaminants associated with the KN facility; and 3) assist
remediation in the downgradient portion of the VHO plume. The final reinjection locations(s)
would be determined during remedial design. Treated ground water would be sampled as
necessary to comply with Wyoming Underground Injection Control (UIC) program
requirements.
Alternative V6 relies on natural processes in the ground water to reduce VHO levels in
downgradient portions of the aquifer. Concentrations of VHOs should decline two orders of
magnitude, which would be sufficient to lower the VHO concentrations to MCLs and proposed
MCLs, within about six years. An extraction well system in the upgradient portions of the plume
would help prevent VHO concentrations in ground water leaving the northern Dow/DSI property
boundary from exceeding MCLs or proposed MCLs. VHO concentrations throughout the
aquifer would therefore meet MCLs and proposed MCLs within six years under Alternative V6.
However, there is a minimal chance that a complete flushing could take as long as 18 years.
In situ bioremediation in the downgradient portion of the plume was considered as an
additional component of Alternative V6. However, it was not incorporated for the following
reasons: 1) this type of treatment is designed primarily for source control, not area control; 2)
the uncertainties in remediation time associated with this treatment; 3) extraction and injection
of treated water would cause nearby plumes to migrate further into the residential area; and 4)
treatability studies would be required.
Costs for Alternative V6 would include capital cost of $183,000, O&M costs of $122,000, and
present worth cost of $354,000.
Alternative V6A - Extraction of the upgradient portion of the plume which contains the
highest VHO concentrations, carbon adsorption treatment of extracted ground water,
discharge of treated ground water to Elkhorn Creek or reinjection upgradient or
downgradient of the extraction well system, and natural attenuation in the downgradient
portions of the plume.
This alternative is Similar to Alternative V6, except extracted ground water would be treated to
remove VHOs in a carbon adsorption system on-site similar to Alternative V4A.
Alternative V6 costs would include $357,000 in capital cost, $114,000 for O&M, and a present
net cost of $518,000.
Alternative V7 - In situ bioremediation of VHO-impacted ground water.
In situ bioremediation of ground water with VHO concentrations exceeding MCLs and
proposed MCLs would involve addition of an oxygen source, nutrients, and hydrocarbon
feedstock, such as methane, to the aquifer to promote the activity of organisms which co-
metabolize VHOs. An injection and extraction well circulation system would distribute oxygen,
nutrients, and co-metabolites through the aquifer. Assuming the extraction and injection well
system would consist of six extraction wells and four injection wells, VHO concentrations would
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be expected to be reduced to MCLs and MCLs in two to five years. The actual number of wells
for the system could change as determined by remedial design. Treatabiiity testing would be
necessary to determine design parameters for in situ bioremediation.
Ground water monitoring would be performed during the two to five years of in situ ground
water treatment and following completion of treatment to verify the reduction of VHO
concentrations in the aquifer.
Capital cost for this alternative would be $425,000 and O&M costs would be $133,000. Present
worth cost would be over $1 million.
BETX Plume.
For the BETX plume, five remedial alternatives (including the no-action alternative) remained
following the screening analysis. Table 5 summarizes the alternatives for the BETX plume.
Each of the remedial alternatives designed to address the BETX plume are described below.
Alternative B2 contemplated collection of BETX-impacted ground water and transport to an off-
site RCRA treatment facility. This alternative was eliminated early in the evaluation process
because it would be technically infeasible to implement and would involve costs that would be
excessive compared to its overall effectiveness.
Alternative B1 • No-action with ground water monitoring.
Similar to Alternative V1 for the VHO plume, Alternative B1 relies on presently occurring natural
processes to reduce concentrations on the BETX compounds in the aquifer. The time frame
for the ground water to be restored to a Classification I aquifer under the no-action alternative
is unknown.
The costs associated with ground water monitoring for this alternative would be $11,000 in
O&M. Present worth cost would be $137,000.
Alternative B3 - Extraction of BETX-impacted ground water, aerobic biological treatment of
extracted ground water, discharge of treated ground water to either injection wells
located upgradient or downgradient of the extraction well system or to Elkhorn Creek
Extraction of ground water with BETX concentrations above MCLs or proposed MCLs would be
accomplished in Alternative B3 with an extraction well system. Assuming a volume of impacted
ground water of ten acre-feet as estimated in the RI/FS, the time of aquifer remediation has
been calculated to be approximately three months. If the volume of impacted ground water is
assumed to be 25 acre-feet, based on a more conservative approach, the time for remediating
the aquifer is extended to approximately eight months. Ground water extraction and treatment
would continue until MCLs and proposed MCLs are permanently attained in the BETX plume.
Extracted ground water would be passed through an oil/water separator to remove free
hydrocarbons. Recovered hydrocarbons would be recycled. It was assumed that the existing
oil/water separator would be used for this purpose.
Following separation of aromatic hydrocarbons, a sequencing batch reactor system, similar to
the system described for Alternative V3 for the VHO plume, would provide aerobic biological
treatment of extracted ground water and would facilitate destruction of organic constituents.
The treatment system would be expected to volatilize some of the BETX compounds which
would be released to the atmosphere.
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Table 5: Summary of BETX Plume Alternatives
Component
Common
Elements
Extraction
Treatment
Technology
Disposition of
Treated Water
Ground Water
Monitoring
Institutional
Controls
Soil Vapor Extraction
of BETX Contaminated Soils
Hydrocarbons Recovery
and Recycling
Extraction of Ground
Water with BETX
Concentrations > MCLs
Aerobic Biological Treatment
of Extracted Ground Water
Air Stripping of
Extracted Ground Water
Chemical Oxidation of
Extracted Ground Water
In-situ Bioremediation
of BETX Plume
Injection of Treated Water
to Up/Downgradient Wells
Discharge of Treated
Water to Elkhorn Creek
Alternatives
B1
X
B3
X
X
X
X
X
X
X
(X)
B4
X
X
X
X
X
X
X
(X)
B5
X
X
X
X
X
X
X
(X)
B6
X
X
X
X
X
(X) - Option or Contingency
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Aerobic biological treatment of ground water would produce an estimated 10 to 20 tons of
sludge per year. The sludge would be expected to meet all RCRA criteria for land disposal.
Treated ground water would be discharged to injection wells upgradient or downgradient of the
extraction well system or to Elkhorn Creek. Upgradient injection locations could facilitate
movement of the contaminants toward extraction wells. Downgradient injection locations could
serve to contain the plume and also provide hydraulic assistance in ground water collection.
The discharge would be sampled as necessary to comply with NPDES and/or Wyoming UIC
program requirements.
Costs for this alternative would include capital cost of $582,000, and O&M costs of $44,000.
The present worth cost would be $750,000.
Alternative B4 - Extraction of BETX-impacted ground water, air stripping of extracted
ground water, and discharge of treated ground water to either injection wells located
upgradient or downgradient of the extraction well system or to Elkhorn Creek.
This alternative is similar to Alternative 63, except extracted ground water would be treated with
an air stripper. It was assumed that the existing on-site air stripper would be used. In the air
stripping process, BETX compounds are transferred from the water phase to the air phase and
discharged to the atmosphere. Based on the best available control technology (BACT)
analysis performed as part of the EE/CA for the KN current removal action, vapors emitted
during air stripping and SVE treatment at the KN facility would be associated with an individual
probability of cancer of 1 X 1 O-7, which is within the acceptable limit established by the NCP.
Based on this analysis, the WDEQ determined that the preferred approach for management of
air stripper emissions for the KN removal action was venting the air stripper emissions at the
top of the on-site flare stack, which raises the point of emissions to 110 feet above ground
level, thereby decreasing the individual probability of cancer to 5 X10r9. Accordingly, this
method of air emission management was implemented in connection with the current removal
action and is included in Alternative B4. It was assumed that vapors emitted from the air
stripping system would be vented from the flare stack and that risk levels similar to those for
the current removal action would be associated with the system proposed. Discharge from the
flare stack would be monitored as necessary to comply with Wyoming air quality standards.
The present worth cost for this alternative would be $248,000. The capital cost would be
$73,000 with O&M costs of $51,000.
Alternative B5 - Extraction of BETX-impacted ground water, chemical oxidation of
extracted ground water, and discharge of treated ground water to either injection wells
located upgradient or downgradient of the extraction well system or to Elkhorn Creek.
This alternative is similar to alternatives B3 and B4, except chemical oxidation of extracted
ground water would be implemented on-site using controlled reactor vessels similar to
Alternative V5 for the VHO plume
Costs for this alternative would include $400,000 capital cost, $53,000 O&M costs, and a
present worth cost of $577,000.
Alternative B6 - In sftu bioremediation of BETX-impacted ground water.
In situ bioremediation of ground water would involve adding an oxygen source and nutrients to
the aquifer in order to promote the activity of organisms which degrade contaminants in a
manner similar to Alternative V7 for the VHO plume. The injection/extraction well system would
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consist of one extraction well and one injection well. It was assumed that one of the three
existing aromatic hydrocarbons recovery wells would be used for extraction, and an existing
on-site injection well would be used for injection. The actual number and location of wells for
the system could change as determined by remedial design. Prior to mixing, extracted water
would be passed through an oil/water separator to remove BETX contaminants extracted with
ground water. Recovered BETX contaminants would be recycled. To the extent technically
practicable, in situ bioremediation would continue until the ground water achieves MCLs and
proposed MCLs which would be expected to be within two to five years. Treatability testing
-v. would be necessary to determine design parameters for in situ bioremediation.
This alternative would cost $87,000 in capital cost with $37,000 for O&M. The present worth
would be $344,000.
VIII. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The remedial alternatives developed in the FS were analyzed in detail for both the VHO and
BETX plumes using nine evaluation criteria. The resulting strengths and weaknesses of the
alternatives were then weighed to identify the alternative for each plume providing the best
balance among the nine criteria. These criteria are: 1) overall protection of human health and
the environment; 2) compliance with applicable or relevant and appropriate requirements
(ARARs); 3) reduction of toxicity, mobility, or volume through treatment; 4) long-term
effectiveness and permanence; 5) short-term effectiveness; 6) implementability; 7) cost; 8)
state acceptance; and 9) community acceptance. Each of these criteria is described below.
VHO Plume
Criterion 1: Protection of Human Health and Environment
Overall protection of human health and the environment addresses whether a remedy provides
adequate protection and describes how risks posed through each pathway are eliminated,
reduced, or controlled through treatment, engineering controls, or institutional controls.
All the treatment technologies employed by the alternatives are protective of human health and
the environment by eliminating or reducing risk through the treatment of contaminants in ground
water. In addition, the institutional controls and the existing municipal water supply would
minimize further use of ground water and therefore reduce exposure to contaminants. As the
no-action alternative does not include treatment or controls, it provides no reduction in risk and
will no longer be discussed with regard to the VHO plume.
Alternatives V6 and V6A, which contemplate limited extraction of ground water, provide the
greatest overall protection. Extraction and injection of ground water throughout the entire VHO
plume, as considered in alternatives V3, V4, V4A, V5, and V7, would accelerate eastward
migration of the RCRA plume. The approximate areal extent of the RCRA plume is shown in the
residential area on Figure 2. The resulting movement of the RCRA plume would increase the
areal extent of contamination in the aquifer from that plume, thereby increasing potential risk to
residents in the subdivisions.
Criterion 2: Compliance with Applicable Relevant and Appropriate Requirements (ARARs)
Applicable requirements are those cleanup standards, standards of control, and other
substantive requirements, criteria, or limitations promulgated under Federal or State
environmental or facility siting law that specifically address a hazardous substance, pollutant,
contaminant, remedial action, location, or other circumstance at a CERCLA site. Relevant and
appropriate requirements are those cleanup standards, standards of control, and other
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substantive requirements, criteria, or limitations promulgated under Federal or State
environmental siting law that, while not "applicable" to a hazardous substance, pollutant,
contaminant, remedial action, location, or other circumstance at a CERCLA site, address
problems or situations sufficiently similar to those encountered at the CERCLA site that their use
is well suited to the particular site.
Compliance with ARARs addresses whether a remedy will meet all Federal and State
environmental laws and/or provide basis for a waiver from any of these laws. These ARARs are
divided into chemical specific, action specific, and location specific groups.
All the VHO alternatives would comply with ARARs. The ARARs evaluation is provided as
Exhibit 1.
Criterion 3: Long-Term Effectiveness and Permanence
Long-term effectiveness and permanence refers to the ability of a npitfdy to maintain reliable
protection of human health and the environment over time. ThiSxcfiterion includes the
consideration of residual risk and the adequacy and reliability^ controls.
The remedial alternatives all result in minimal residual risk. All the alternatives are expected to
attain MCLs and proposed MCLs, thereby resulting in minimal risk from contaminant residuals
in ground water. The institutional controls and the existing municipal water supply additionally
mitigate residual risk by minimizing the use of ground water.
Alternatives V3, V5 and V7 result in no treatment residuals. Alternatives V4 and V6 release
emissions to the atmosphere, but at negligible levels ^nd minimal risk. Additional controls for
IrTese two alternatives include monitoring to ensure compliance with Wyoming air quality
standards, and a BACT analysis to ensure emissions are minimized. Alternatives V4A and V6A
require disposal or treatment of contaminated carbon filters, but pose minimal residual risk.
Criterion 4: Reduction of Toxicitv. Mobility, or Volume through Treatment
Reduction of toxicity, mobility, or volume through treatment refers to the preference for a
remedy that uses treatment to reduce health hazards, contaminant migration, or the quantity of
contaminants at the site.
All the alternatives employ an irreversible treatment as a primary element to address the
principal threat of contamination. Alternatives V6 and V6A treat a smaller volume of water than
the other alternatives in order to avoid adverse effects to the RCRA plume.
Reduction in toxicity, mobility, and volume of contaminants in ground water is best
accomplished by Alternative V5 through chemical oxidation. Alternatives V4 and V6 indirectly
reduce toxicity and volume through photodegradation of contaminants. Photodegradation
occurs when the contaminants, released to the atmosphere, are broken down by sunlight.
Alternative V7 reduces toxicity and volume through treatment but would require treatability
studies to evaluate its effectiveness. Alternatives V4A and VGA reduce mobility, but not volume
or toxicity because these alternatives result in spent carbon filters containing the contaminants,
reguiringjisposal or regeneration of the carbon. Alternative V3 reduces toxicity, mobility and
volume of contaminants, but wpuldjaroduce 170 tons of non-hazardous sludge annually which
would require disj
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Criterion 5: Short-Term Effectiveness
Short-term effectiveness refers to the period of time needed to complete the remedy and any
adverse impacts on human health and the environment that may be posed during the
construction and implementation of the remedy.
Alternatives V6 and V6A are not expected to pose any appreciable short-term risks to the
community and workers during construction and implementation.
Alternatives V3, V4, V4A, V5, and possibly V7 are expected to cause adverse effects to the
environment and human health by spreading the RCRA plume through the aquifer and possibly
depleting the aquifer.
The high extraction volume in alternatives V3, V4, V4A, V5, and V7 are expected to attain ^
remedial objectives in the shortest time, two years, with the exception of V7 which could take
as long as five years. Alternatives V6 and V6A are expected to require six years to attain
remedial objectives. These two alternatives would not result in the unacceptable effects on
human health and the environment as are expected from the other alternatives through effects
on the RCRA plume.
Criterion 6: Implementabilitv
Implementability refers to the technical and administrative feasibility of a remedy, including the
availability of materials and services needed to implement the chosen solution. It also includes
coordination of Federal, State, and local governments to clean up the site.
Alternatives V6 and V6A are most easily technically implemented because these alternatives
involve activities primarily on the Dow/DSI facility, requiring the least amount of construction
and least difficulty with property access. Alternative V7, and possibly V5, would be less easily
implemented because of the need for treatability studies to better understand the applicability
of in situ bioremediation and chemical oxidation to the site. Alternatives V3. V4A, and V6A
present no technical difficulties, but require the additional burden of disposing of or treating
residual sludges and carbon filters.
All alternatives require ground water monitoring. Alternatives V6 and V6A additionally require
air monitoring. Monitoring activities would be coordinated with the State of Wyoming.
Criterion 7: Cost
This criterion examines the estimated costs for each remedial alternative. For comparison,
capital and annual O&M costs are used to calculate a present worth cost for each alternative.
Alternatives V6 and V6A have the lowest capital and O&M costs, resulting in present worth of
$353,822 and $518,407, respectively. These alternatives are the least expensive because they
incorporate scaled-down ground water extraction in comparison to the other alternatives. V7 is
the next most costly, with a present worth of $1,011,288. Alternatives V4 and V4A, which are
scaled-up versions of V6 and V6A, and V5, differ in treatment method, but are otherwise similar
and so cost nearly the same. Present worth estimates for these three alternatives range from
$1,351,883 to $1,673,488. V3 is the most costly because of very high capital expenses, and
has a present worth of $2,482,675.
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Criterion 8: State Acceptance
xl
EPA has involved the WDEQ in the RI/FS and remedy selection process. WDEQ was provided
the opportunity to comment on the RI/FS document and the proposed plan, and took part in
the public meeting held to inform the public of the proposed plan. WDEQ's statement in regard
to the selected remedy, read at the public meeting, states in part "It is the position of the
Department [WDEQ] that the proposed actions identified in alternatives B4 and V6 should be
implemented as soon as possible". WDEQ went on to add that it concurs with the proposal to
further investigate subsurface soil contamination sources as contemplated in OU 2.
WDEQ believes, however, that remedial actions taken under CERCLA should be integrated with
the RCRA corrective action addressing the RCRA plume, forming a comprehensive effort to
concurrently remediate ail ground water contamination within the Brookhurst subdivision.
WDEQ's comments are further addressed in the attached Responsiveness Summary.
Criterion 9: Community Acceptance
EPA solicited input from the community on the clean up methods proposed for the ground
water at the Mystery Bridge site. Although public comments indicate no specific opposition to
the preferred alternative, residents and their representatives did raise concerns about the
methods and data used to reach that alternative. These issues are addressed in the attached
Responsiveness Summary and some will be incorporated into OU 2 activities for the site.
BETX Plume
Criterion 1: Protection of Human Health and the Environment
All the treatment technologies employed by the remedial alternatives are protective of human
health and the environment by eliminating or reducing risk through the treatment of
contaminants in ground water. In addition, institutional controls and the municipal water supply
would minimize further use of ground water and therefore reduce exposure to contaminants.
As the no-action alternative does not include treatment or controls, it provides no additional
reduction in risk and will no longer be discussed with regard to the BETX plume.
None of the alternatives is expected to adversely impact the RCRA plume as some of the VHO
plume alternatives would.
Criterion 2: Applicable or Relevant and Appropriate Requirements (ARARs)
All the BETX alternatives would comply with ARARs. The ARARs evaluation is provided as
Exhibit 1.
Criterion 3: Long-Term Effectiveness and Permanence
The remedial alternatives all result in minimal residual risk. All the alternatives are expected to
attain MCLs or proposed MCLs, thereby resulting in minimal risk from contaminant residuals in
ground water. The institutional controls and the existing municipal water supply additionally
mitigate residual risk by minimizing the use of ground water.
Over the long term, each alternative will likely leave some residual BETX contaminants in
subsurface soils on or near the KN facility. Problems related to these residuals will be
addressed OU 2. Alternative B6, however, would help treat some of the residual BETX
contaminants since in situ bioremediation would destroy contaminants with naturally occurring
microorganisms in ground water and in subsurface soils.
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Alternative 65 would result in no treatment residuals. Alternative B4 would release emissions to
the atmosphere, but at negligible levels and minimal risk. The air stripper contemplated in
Alternative B4 is currently operating as part of the KN removal action. Monitoring has
demonstrated that air stripper emissions are within Wyoming air quality standards. Alternative
B3 would result in 10 to 20 tons annually of non-hazardous residual sludge requiring off-site
disposal.
Criterion 4: Reduction in Toxicitv. Mobility, or Volume through Treatment
All the alternatives employ an irreversible treatment as a primary element to address the
principal threat of contamination.
Reduction in toxicity, mobility, and volume of contaminants in ground water would best be
accomplished by alternatives B5 and B6. Alternative 34 would remove contaminants from
ground water and indirectly reduce toxicity and volume through photodegradation of the
contaminants. Alternative B3 would reduce toxicity, mobility and volume of contaminants, but
would produce 10 to 20 tons of non-hazardous sludge annually requiring disposal.
Criterion 5: Short-Term Effectiveness
None of the alternatives would result in adverse short-term effects for community and worker
protection. However, Alternative 86 would require two to five years to achieve clean up, whereas
alternatives B3, B4 and B5 are estimated to achieve clean up within one year.
Criterion 6: Implementability
Alternative B4 would most easily be implemented because the air stripper used in this
alternative is currently in operation as part of the KN removal action. Alternative 65 would pose
no undue problem with regard to this criterion. Alternative 63 would present no technical
difficulties but requires the additional burden of disposing of residual sludge. Alternative 66
would be more difficult to implement because of the need for treatability studies to better
understand the applicability of in situ bioremediation to the site.
All alternatives require ground water monitoring. Alternative 64 additionally requires air
monitoring. Monitoring activities will be coordinated with the State of Wyoming.
Criterion 7: Cost
With the air stripper already in place, Alternative 64 has minimal capital costs. Its present worth
of $247,917 is also the least among all alternatives. Alternative 66 is the next most expensive
with a present worth of $334,553. Alternatives 85 and 63 are the most costly, with present
worth estimates of $577,217 and $750,502, respectively.
Criterion 8: State Acceptance
State acceptance for this alternative is the same as described above for Alternative V6 for the
VHO plume.
Criterion 9: Community Acceptance
Community acceptance for this alternative is the same as described above for Alternative V6 for
the VHO plume.
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IX. SELECTED REMEDY
EPA has selected the combination of alternatives V6 and B4 as the remedy for the ground
water operable unit for the Mystery Bridge site. This remedy is made up of the following
components:
Common Elements
• Monitoring ground water, discharged treated water, and air; and
• Implementation of institutional controls.
VHP Plume: Alternative V6
• Extraction of ground water with concentrations of VHOs above MCLs or proposed
MCLs in the upgradient portion of the plume (i.e., on and/or near the Oow/OSI
facility);
• Treatment of contaminated ground water with an on-site air stripping facility;
• Reinjection of treated water into the aquifer to provide additional hydraulic
containment of the upgradient portion of the VHO plume being extracted,
minimize any impact from the VHO remediation efforts on the RCRA plume and
BETX plume, and enhance the natural attenuation process in the downgradient
portions of the VHO plume; and
• Reliance on natural processes for reduction of VHO levels in downgradient
portions of the VHO plume.
BETX Plume: Alternative 84
• Extraction of ground water with concentrations of BETX compounds above MCLs
or proposed MCLs throughout the plume;
• Treatment of contaminated ground water with an on-site air stripping facility; and
• Reinjection of treated water into the aquifer to provide additional hydraulic control
of the BETX plume and minimize any potential impact from the BETX remediation
efforts on the RCRA and VHO plumes.
Alternative B4 assumes continuation of the ongoing KN removal action. This removal action
would be expanded, if necessary, to recover any hydrocarbons originating from the KN
operation that may exist outside of KN's facility. In addition, since no ground water in the
residential areas is believed to be contaminated with BETX originating from KN at
concentrations above MCLs or proposed MCLs, this remedy requires that no ground water
contaminated above such levels will be allowed to enter the subdivision from the KN property.
Periodic monitoring will be used to evaluate compliance with this condition.
The remedial design will specify the appropriate number and location of wells and monitoring
points, and system parameters such as flow rates for both the VHO and BETX ground water
treatment systems. Some modifications or refinements may be made to the remedy during
remedial design and construction. Such modifications or refinements, in general, would reflect
results of the engineering design process. Estimated cost for the selected remedy is $600,739.
Details of the costs for each of the VHO and BETX remedies are shown in Table 6.
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e selection of this remedy is based upon the comparative analysis of alternatives presented
bove, and provides the best balance of tradeoffs with respect to the nine evaluation criteria.
ARARs for the selected remedy are shaded in the table provided as Exhibit 1 . As pointed out in
the comparative analysis, the impact of each VHO plume alternative on the RCRA plume was
carefully considered. The close proximity of these two plumes prescribes a remedy that would
not adversely affect the extent of the RCRA plume. VHO plume alternatives which include
limited ground water extraction and minimally disturb the aquifer down gradient of the source
areas meet this need. Air stripping was chosen as the appropriate treatment technology
applied to the extracted ground water bvweiqhing the factors outlined in the comparative
analysis. Natural attenuation was choserTover m situ bioremediation for the downgradient
portion of the VHO plume in Alternative V6 because it would not adversely impact the RCRA
plume in any way, does not require treatability studies, is effective at the existing level of
contamination, and has less uncertainty than bioremediation with regard to remediation time
frame. The selection of Alternative B4 as the remedy for the BETX plume was also based upon
the comparative analysis. A particular strength of this alternative is that it is already in place
and has been proven effective as part of the KN removal action.
Based on the findings in the BRA for the Current Resident and Future Hypothetical Resident
scenarios (see Table 3), the remedial action objectives for this site are the following:
1 ) Prevent ingestion of water containing t-1 ,2 DCE, 1,1,1 TCA, TCE, PCE, benzene,
toluene, ethylbenzene, or xylene at concentrations that either a) exceed MCLs or
proposed MCLs, or b) present a total carcinogenic risk range greater than
1x10-*-1x1O«;and
2) Restore the alluvial aquifer to concentrations that both a) meet the MCLs or proposed
MCLs for M ,2 DCE, 1 ,1 ,1 TCA, TCE, PCE, benzene, toluene, ethylbenzene, and xylene,
and b) present a total carcinogenic risk range less, than 1x10* -1x10*.
Remedial aetten goals specifically delineate action -tevelsTafea of attainment, and restoration
time frameT'fhe-aetiofHevels are MCks and proposed MCLs (as shown previously in tables 1
and 2). Attainment of these aetiorvtovels will provide protectiveness of human health and the
environment. The area of attainment shall be the entire VHO and BETX plumes, including
those areas of the plumes within and outside the Oow/DSI and KN properties. Based on the
contaminant transport modeling performed for the RI/FS, the restoration time frame for this
remedial action shall be six years, with the expectation that remediation of the BETX plume
should be no longer than one year, and with the acknowledgement that the restoration time
frame may vary depending upon the outcome of OU 2 in addressing remaining sources, and
other factors described below.
A further objective of this remedial action is to restore the ground water, with the exception of the
area impacted by the RCRA plume, to its beneficial use, which is, at this site, a drinking water
aquifer. Based on information obtained during the Rl, and the analysis of all remedial
alternatives, EPA and the State of Wyoming believe that the selected remedy will achieve this
objective. It may become apparent, during implementation or operation of the ground water
extraction system, that contaminant levels have ceased to decline and are remaining constant at
levels higher than the remediation goal. In such a case, the systems' performance standards
and/or the remedy may be reevaluated.
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Table 6: Selected Remedy Costs
Page 1 of 2
VHO Plume
Item
Direct Capital Costs
Temporary Deed and/or User Restrictions
Extraction Well System Installation
Well Installation Supervision
Well Pumps
Influent and Discharge Piping
Piping Installation
Air Stripper System
Air Stripper System Installation
Discharge Pump
Mobilization
Equipment Decontamination
Health and Safety Program
Estimated Direct Capital Cost
Indirect Capital Costs
Contingency Allowance (25%)
Engineering Fees (1 5%)
Legal Fees (5%)
Estimated Indirect Capital Cost
Total Estimated Capital Cost
Annual Operation and Maintenance Costs
Ground Water Sample Collection
Ground Water Sample Analysis
Electricity (pumps, blower)
Air Stripper Operation
Air Stripper Maintenance
Air Stripper Cleaning Solution
Discharge Sampling (water)
Discharge Analysis (water)
Air Stripper Vapor Discharge Sampling
Vapor Sample Analysis
Estimated Annual Operation and Mainenance Cost
Present Worth of Annual Operation and Maintenance Costs (i*5%)
Total Estimated Cost VHO Plume
Cost
$15,000
$3,500
$1,110
$2,500
$5,000
$4,000
$57,000
$14,000
$2,500
$7,000
$5,000
$10.000
$126,610
$31 ,653
$18,992
$6.331
$56.975
$183.585
$2,600
$8,400
$4,320
$23,360
$13,440
$1 ,500
$11,680
$54,750
$1,664
$1 .200
$122,914
$170,237
$353,822
From: RI/FS Report (June 1990)
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Table 6: Selected Remedy Costs
Page 2 of 2
BETX Plume
Item
Direct Capital Costs
Temporary Deed and/or User Restrictions
Influent and Discharge Piping
Piping Installation
SVE Wells
Product Recovery Well
Product Recovery Pump
Vacuum Pump
Well Installation Supervision
Mobilization
Equipment Decontamination
Health and Safety Program
Estimated Direct Capital Cost
Indirect Capital Costs
Contingency Allowance (25%)
Engineering Fees (1 5%)
Legal Fees (5%)
Estimated Indirect Capital Cost
Total Estimated Capital Cost
Annual Ooeration and Maintenance Costs
Ground Water Sample Collection
Ground Water Sample Analysis
Electricity (pumps, blower)
Air Stripper Operation
Air Stripper Maintenance
Air Stripper Cleaning Solution
Discharge Sampling (water)
Discharge Analysis (water)
SVE Vapor and Stack Discharge Sampling
Vapor Sample Analysis
Estimated Annual Operation and Mainenance Cost
Present Worth of Annual Operation and Maintenance Costs (i«5%)
Total Estimated Cost BETX Plume
Cost
$15,000
$4,000
$600
$10,500
$4,500
$2,500
$7,500
$1 ,850
$3,000
$500
$500
$50,450
$12,613
$7,568
$2.523
$22,703
$73,153
$2,600
$8,400
$6,000
$6,400
$3,200
$1,700
$3,200
$15,000
$1,664
$2.400
$50,564
$174,765
$247,917
From: RI/FS Report (June 1990)
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The selected remedy will include ground water extraction for an estimated period of at least
one year for the VHO plume and less than one year for the BETX plume, during which time the
systems' performance will be carefully monitored on a regular basis and adjusted as warranted
by the performance data collected during operation. The operation monitoring period will be
determined during remedial design. The operating system may include discontinuing
operation of extraction wells in areas where cleanup goals have been attained, alternate
pumping at wells to eliminate stagnation points, and pulse pumping to allow aquifer
equilibration and encourage adsorbed contaminants to partition into ground water for
extraction and treatment.
X. STATUTORY DETERMINATIONS
EPA's primary responsibility at Superfund sites is to select remedial actions that are protective
of human health and the environment. CERCLA also requires that the selected remedial action
for the site comply with applicable or relevant and appropriate environmental standards
established under Federal and State environmental laws, unless a waiver is granted. The
selected remedy must also be cost-effective and utilize permanent treatment technologies or
resource recovery technologies to the maximum extent practicable. The statute also contains a
preference for remedies that include treatment as a principal element. The following sections
discuss how the selected remedy for contaminated ground water at the Mystery Bridge site
meets these statutory requirements.
Protection of Human Health and Environment
(In order to meet the remedial objectives outlined in the previous section, the risk associated
) with exposure to the contaminated ground water must fall within the acceptable risk for
(carcinogens. Attainment of MCLs and proposed MCLs will assure site risk falls within this
(range. The selected remedy protects human health and the environment by reducing levels of
contaminants in the ground water through extraction and treatment, as well as through natural
attenuation. EPA expects VHOs in ground water would be reduced to MCLs or proposed
MCLs in six years and MCLs or proposed MCLs for BETX compounds would be attained within
one to two years. However, there is a minimal chance that complete remediation may take as
long as 18 years. Together with deed and/or user restrictions and the existing municipal water
supply, the threat of exposure currently posed tqjgsidents from contaminated ground water
would besignifjcantly reduced if not eliminatjd^Df alFthe alternatives for both the VHO and"
/rBh fx plumesTfhe selected alternatives provide the best protection toJuimanJiealth withoui
j v~Lsjgnificantjdverse impact to the environment/fto unacceptable short-term risks or cross-
media impacts would be caused by implementing this remedy.
Attainment of Applicable or Relevant and Appropriate Requirements of Environmental
Laws
All ARARs would be met by the selected remedy.
Chemical Specific ARARs. The selected remedy would achieve compliance with chemical
specific ARARs related to the downgradient ground water and ambient air quality at the site.
The relevant and appropriate requirements include primary drinking water standards
established by the Safe Drinking Water Act. Some contaminants of concern identified for the
site have MCLs. MCLs have been proposed for the remaining contaminants of concern and
are to be considered. Values for the MCLs and proposed MCLs are shown on Table 1 for the
VHO compounds and on Table 2 for the BETX compounds. Concentrations of BETX
compounds throughout the entire BETX plume would be reduced below MCLs or proposed
MCLs by the Alternative B4 treatment system. Concentrations of VHO compounds in the
37
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brod6
while natural attenuation would reduce concentrations in the downgradient portion of the
plume to below MCLs or proposed MCLs.
Benzene emissions from the air stripping treatment system will be monitored and if required,
.<:Tji controls would be jmplemented to ensure would compliance with the National Emission
-f}iyW Standards for Hazardous Air Pollutants (NESHAP). At present it is not expected that
s-£ ^ d constituents for which standards have been established by the Wyoming Air Quality Rules and
Regulations will be produced in the treatment process. In the unlikely event that constituents
^: are produced, the necessary controls would be implemented in order for the emissions to
comply with the regulations]
Action Specific ARARs. The selected remedy would address and comply with action specific
ARARs for injection of treated water back in to the ground according to Wyoming UIC program
established by 40 CFR 147 and Wyoming Water Quality Rules and Regulations, Chapter IX.
The ground water monitoring program which includes wells located upgradient, downgradient,
and within the contaminated ground water would fulfill the requirements of the RCRA corrective
action program.
Land disposal restrictions are not applicable to the selected remedy. Instead, RCRA section
3020 applies to reinjection of treated ground water into Class IV injection wells during CERCLA
response actions. Since the goal is to clean up ground water to drinking water levels, health-
based drinking water standards (MCLs), rather than land disposal restrictions, are the relevant
and appropriate clean up standard.
RCRA requirements would be met as appropriate for owner and operators of hazardous waste
treatment, storage, and disposal facilities. BACT analysis for construction, modification, and
operation of the water treatment systems would comply with the requirements of Wyoming Air
Quality Rules and Regulations and discharges would not be concealed. Similarly, BACT permit
and data requirements for the ground water extraction/injection system would comply with
Wyoming Water Quality Rules and Regulations.
Location Specific ARARs. The selected remedy would address and comply with all location
specific ARARs for preservation and protection of the North Platte River floodplain according to
the requirements of 40 CFR 6.302. RCRA location standards for treatment, storage and
disposal facilities are relevant and appropriate for temporary storage tanks of recovered
hydrocarbons.
Cost Effectiveness
EPA believes the selected remedy is cost-effective in mitigating the principal risk posed by
contaminated ground water within a reasonable period of time. Section 300.430(f)(ii)(D) of the
NCP requires EPA to evaluate cost-effectiveness by comparing all the alternatives which meet
the threshold criteria: protection of human health and the environment, against three additional
balancing criteria: long-term effectiveness and permanence; reduction of toxicity, mobility or
volume through treatment; and short-term effectiveness. The selected remedy meets these
criteria and prndurns thn hoitmmmH effectiveness at-tho lowest roaoonablg^ost. Therefore;
the oolootod remedy is cost-offMtiyc as defined in tho NCP. The estimated jrost for the
selected remedy (£over $600,OQG^>
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r
Utilization of Permanent Solutions and Alternative Treatment Technologies or Resource
Recovery Technologies to the Maximum Extent Practicable
EPA believes the selected remedy represents the maximum extent to which permanent
solutions and treatment technologies can be utilized in a cost-effective manner for the Mystery
Bridge site. Of those alternatives that are protective of human health and the environment and
comply with ARARs, EPA has determined that the selected remedy provides the best balance
of trade-offs in terms of long-term effectiveness and permanence; reduction in toxicity, mobility
or volume achieved through treatment; short-term effectiveness; implementability; and cost,
and also considering the statutory preference for treatment as a principal element and
considering State and community acceptance.
/^Alternative V6 complies with ARARs; and reduces the toxicity, mobility, and volume of the
contaminants in the ground water equally as well as the other VHO plume alternatives. Short-
term effectiveness and protection of human health and the environment were critical in
choosing Alternative V6 with natural attenuation for the downgradient portion of the VHO plume
in light of effects on the RCRA plume and trade-off with remediation time frame.
Alternative B4 provides long-term effectiveness equally as well as alternatives B3 and 65.
Although Alternative B6 has potential to best provide protection, it would require a greater
remediation time frame and cost more than Alternative B4. Alternative B5 would accomplish a
greater reduction in toxicity, mobility and volume of contaminants than B4, but at over twice the
cost. Alternative B4 removes contaminants from ground water and will indirectly reduce the
toxicity and mobility through photodegradation. Alternative B3 requires the additional burden
of disposing of 10 to 20 tons of non-hazardous sludge annually. Since Alternative B4 would be
a continuation of the ongoing air stripping operation at the KN facility,' it would be the easiest to
implement and cost the least of the BETX plume alternatives.
The State of Wyoming is in concurrence with the selected remedy. The Proposed Plan for the
Mystery Bridge site was released for public comment in July 1990. The Proposed Plan
identified alternatives V6 and B4 as the preferred remedy. EPA reviewed all written and verbal
comments submitted during the public comment period. Upon review of these comments, EPA
determined that no significant change to the remedy originally identified in the Proposed Plan
.was necessary.
Preference for Treatment as a Principal Element
/" The selected remedy satisfies, in part, the statutory preference for treatment as a principal
( element. The principal threat to human health is from ingestion of and direct contact with
\ contaminated ground water. The selected remedy reduces levels of BETX contaminants and
) the highest concentrations of VHO contaminants in ground water through treatment using air
stripper systems. Natural attenuation of the downgradient portion of the VHO plume was
selected over treatment because of the adverse effects on the nearby RORA that would result
from aquifer drawdown during pumping of that portion of the plume for treatment. If the
downgradient portion of the plume is pumped, the RCRA plume could migrate further into the
residential area and thus increase the risk of exposure to contaminated ground water.
sfc &ffu/U4-s
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