Office of Solid Waste and EPA-540-R-013-015
Emergency Response (5102G) January 29, 2013
Optimization Review
Velsicol Chemical Corporation
Hardeman County Landfill
Superfund Site
Toone, Tennessee
http://www.clu-in.org/optimization | http://www.epa.gov/superfund/cleanup/postconstruction/optimize.htm
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OPTIMIZATION REVIEW
VELSICOL CHEMICAL CORPORATION
HARDEMAN COUNTY LANDFILL
SUPERFUND SITE
TOONE, TENNESSEE
Report of the Optimization Review
Site Visit Conducted at the Velsicol Chemical Corporation
Hardeman County Landfill Superfund Site on
January 18,2012
January 29, 2013
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EXECUTIVE SUMMARY
The U.S. Environmental Protection Agency's (EPA) working definition of optimization is as
follows:
"Efforts at any phase of the removal or remedial response to identify and implement actions that
improve the action's effectiveness and cost-efficiency. Such actions may also improve the
remedy 'sprotectiveness and long-term implementability which may facilitate progress towards
site completion. To identify these opportunities, regions may use a systematic site review by a
team of independent technical experts, apply techniques or principles from green remediation or
Triad, or apply some other approach to identify opportunities for greater efficiency and
effectiveness. Contractors, states, tribes, the public, and potentially responsible parties (PRP)
are also encouraged to put forth opportunities for the Agency to consider. "
An optimization evaluation considers the goals of the remedy, available site data, conceptual site
model (CSM), remedy performance, protectiveness, cost-effectiveness, and exit strategy. A
strong interest in sustainability has also developed in the private sector and within Federal, State,
and Municipal governments. Consistent with this interest, optimization now routinely considers
green remediation and environmental footprint reduction during optimization evaluations. An
optimization evaluation includes reviewing site documents, interviewing site stakeholders,
potentially visiting the site for one day, and compiling a report that includes recommendations in
the following categories:
Protectiveness
Cost-effectiveness
Technical improvement
Site closure exit strategy
Environmental footprint reduction
The recommendations are intended to help the site team identify opportunities for improvements
in these areas. In many cases, further analysis of a recommendation, beyond that provided in this
report, may be needed prior to implementation of the recommendation. Note that the
recommendations are based on an independent evaluation, and represent the opinions of the
evaluation team. These recommendations do not constitute requirements for future action, but
rather are provided for consideration by the Region and other site stakeholders. Also note that
while the recommendations may provide some details to consider during their implementation,
the recommendations are not meant to replace other, more comprehensive, planning documents
such as work plans, sampling plans, and quality assurance project plans.
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Site-Specific Scope of Optimization Review
The optimization review of the Velsicol Chemical Corporation Hardeman County Landfill
Superfund Site (the Site) includes a comprehensive review of the CSM, existing soil and waste
remedies, soil vapor extraction (SVE) pilot studies, and potential remedial alternatives for soil. In
particular, the review covers the following:
Review of the existing Records of Decision (ROD), Five-Year Reviews, 2007 Feasibility
Study, SVE pilot test results, 2011 draft Focused Feasibility Study for landfills, progress
reports, geophysical data, soil gas data, landfill cap and characterization information.
Review of SVE as a potential Site-wide soil remedy.
Considerations for SVE design and implementation.
Consideration of other potential remedial alternatives.
While the focus of this review is on potential soil and waste remediation, an initial review of
potential groundwater remediation is also considered.
Site-Specific Background
The Velsicol Chemical Corporation Hardeman County Landfill Superfund Site is located in a
rural area near the town of Toone in western Tennessee. The Site includes approximately 24
acres of capped landfill area within a 237 acre property parcel. Between 130,000 and 300,000
drums of chemical wastes from Velsicol's pesticide manufacturing plant in Memphis were
disposed of in unlined trenches at the Site between 1964 and 1973. Using the low end of this
estimate, and multiplying by 55 gallons per drum, this equates to an estimate of over 7 million
gallons of chemical waste. The drums and other containers of waste were dumped in the trenches
and the trenches were backfilled. Years later (in 1980) a clay cap was placed over the disposal
areas, and even later (1997) a multi-layer composite cap was placed over the clay cap, per the
ROD for Operable Unit 2 (OU2: waste and soils).
The wastes included pesticides and chemicals used in the production of pesticides. Carbon
tetrachloride and other volatile organic compounds (VOCs) made up a substantial portion of the
wastes (a PRP contractor, Environ, estimates 1 percent to 5 percent of the total volume) and have
been the most mobile contaminants at the Site. Pesticides and semi-volatile organic compounds
(SVOCs) are also contaminants of concern (COCs), primarily for soil within and below the
buried waste.
An SVE pilot test was conducted at one of the disposal areas in 2009-2011. The SVE system
proved effective at removing substantial VOC mass. SVE is being considered as a new full-scale
remedy for OU2.1
1 Since completion of the optimization review and the initial draft of this report, a ROD amendment has been
completed for OU2 specifying SVE in all disposal areas.
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A 1,700-acre groundwater plume emanates from the disposal areas and discharges into
downgradient streams and wetlands. The primary contaminant in groundwater is carbon
tetrachloride, which has a maximum contaminant level (MCL) of 5 micrograms per liter (|ig/L).
Measured concentrations over a large portion of the plume (900 acres) exceed 5,000 jig/L and
concentrations as high as 64,000 |ig/L have been recorded. The plume appears to be almost
entirely within an upper unconfined aquifer layer that is approximately 50 feet thick. There is
limited contamination in the underlying leaky confined aquifer. It has been noted in previous
documents (including the 2011 Five-Year Review report) that the plume is stable in size. The
plume has already reached lateral and downgradient discharge locations at streams and
streamside seeps and wetlands.
Per the ROD for OU1 (groundwater), a Groundwater Extraction and Treatment System (GETS)
was constructed in 1996. It operated for 6 years removing 110,000 pounds VOCs while treating
796 million gallons of water. The average withdrawal rate of less than 250 gallons per minute
(gpm) was much less than the design objective of 465 gpm. The GETS proved difficult to
operate and the EPA determined that groundwater remediation goals would not be met in a
reasonable time frame. The system was shut down in 2003.
There are approximately 35 residences located within the area of the groundwater plume (the
groundwater beneath these residences has concentrations that exceed remediation goals). A clean
public water supply has been made available to the plume-area residents and institutional
controls to prevent groundwater use have been obtained for 56 of 60 parcels within the plume,
covering approximately 86% of the plume area.
Ambient air and indoor air concentrations of carbon tetrachloride are elevated relative to
background within the plume area, and indoor-air mitigation systems have been installed at two
residences (in 2007). Some measured concentrations in ambient air have been above calculated
risk-based action levels based on an excess cancer risk of 10"4 (the upper end of the EPA's
acceptable risk range).
Concentrations are also elevated in surface water near plume discharge locations. The
concentrations are above Tennessee surface water quality criteria. However, Site-specific risk
assessments have concluded that surface-water exposure routes do not present significant human
health or environmental risks.
Summary of Conceptual Site Model
The CSM consists of contaminant source areas at the disposal areas, a groundwater plume
emanating from the disposal areas and migrating to the north and northwest in the unconfined
aquifer, discharge to downgradient surface waters, and volatilization of VOC contaminants to
ambient and indoor air. The CSM is succinctly depicted in Figure B-4 of the 2011 Five-Year
Review report (included in Attachment A; prepared by Environ).
in
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Humans may be exposed to Site contaminants through direct contact with waste or contaminated
soil, through consumption of contaminated groundwater, through contact with (or ingestion of)
contaminated surface water, through inhalation of ambient or indoor air within the plume area, or
through consumption of organisms (for example, fish) from Site-area habitats.
All of these exposure pathways have been evaluated through risk assessments and several of the
more critical pathways have been addressed through institutional and engineering controls.
Summary of Findings
Based on a technical review of the information provided to the Optimization Team, the Site visit
conducted on January 18, 2012, and interviews with persons knowledgeable about the Site,
several findings have been identified. The observations provided below are the technical
interpretations of the Optimization Team. They are not intended to imply a deficiency in the
work of the site managers but are offered as constructive information and opinions in the best
interest of the EPA and the public. The main findings of the Optimization Team are listed below,
with additional supporting details provided in Section 5 of this report:
Approximately 9 million pounds of VOCs are present at the Site.2 It is clear from Site
data that most of the contaminant mass is within the footprint of the largest landfill area,
the North Disposal Area (NDA). Based on concentrations present in the groundwater, the
size of the plume, and the likely presence of non-aqueous phase liquid (NAPL) in
groundwater, it is estimated that at least 7 percent (and perhaps well over 10 percent) of
the total mass buried at the Site has already migrated to the saturated zone, much in
NAPL form.
A primary issue with the source areas is that they act as a continuing long-term source for
groundwater contamination. The source areas also likely contribute directly to ambient
air contamination, especially near the source areas.
There remains the potential for future human exposure to groundwater with
concentrations well in excess of MCLs. The institutional controls that are in place help
reduce the likelihood of future human exposure to contaminated groundwater.
Despite the fact that surface-water concentrations exceed MCLs and certain surface-water
criteria, potential risks for recreational users exposed to surface water and fish at the Site
were found to be acceptable in 2011 risk assessments. The affected surface waters are not
currently used as a water-supply source.
2 This estimate of 9 million pounds is consistent with a draft Focused Feasibility Study for OU2 (Environ, January
2012) reviewed by the Optimization Team. Environ has since reduced their mass estimate to 6.8 million pounds.
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The ambient (outdoor) air at the Site has elevated levels of carbon tetrachloride. A few
measurements of ambient air concentrations in 2007-2008 exceeded risk-based screening
levels based on a 10"4 excess cancer risk. Within the immediate area of the disposal areas
(on the landfill property) elevated ambient air concentrations are likely caused by vapors
emanating from the buried waste, the contaminated soil in the vadose zone below the
buried waste, and (probably to a lesser extent) vapors emanating from contaminated
saturated-zone groundwater. Immediately adjacent to the landfill property (for example,
along Old Toone Road due west of the disposal areas) it is likely that ambient air
concentrations are caused by volatilization from the waste and vadose zone at the source
areas and by volatilization from groundwater and nearby surface seeps. North of the
landfill property, it is likely that the most elevated ambient air concentrations are caused
primarily by volatilization from contaminated surface water and groundwater.
The vapor mitigation systems that were installed at two homes are effective at mitigating
indoor air risk. There remains a future risk of indoor air exposure at homes within the
plume, including homes that may be built in the future without vapor mitigation systems.
In the opinion of the Optimization Team, the measures that have been taken at the Site to
reduce the potential for human exposure to Site contaminants (for example, past land
acquisition, groundwater use restrictions, provision of an alternate water supply, and
fencing around the disposal areas) have been prudent and effective.
The January 2012 draft OU2 Focused Feasibility Study (FFS) provides a summary of
several feasible remedial technologies that is helpful for assessing the relative merits of
different potential remedial approaches. This draft FFS also provides a feasibility-level
evaluation of remedial alternatives relative to National Oil and Hazardous Substances
Pollution Contingency Plan (NCP) criteria. The technologies and alternatives presented
in the FFS cover an appropriate range of potential remediation approaches for this
operable unit. The Optimization Team reviewed the draft FFS in developing technical
comments on SVE as a full-scale remedy for OU2 relative to other potential remedial
alternatives.
In the opinion of the Optimization Team, based on technical experience at other sites and
a review of Site documents, the remedial alternative involving SVE only (SA-4) is better
than the alternative involving excavation and on-Site disposal with SVE (SA-5) when
evaluated relative to the NCP criteria.
SVE is a cost-effective and implementable technology for removing VOC mass. While
SVE will remove contaminant mass, it will not lead to complete Site restoration without
other actions to address saturated-zone contamination. SVE alone is not expected to offer
substantial overall risk reduction for the Site for the next several decades, at least. There
is a tradeoff involved when deciding between the SVE alternative (SA-4) and a more
limited and much less costly alternative (SA-2) not including SVE. It is appropriate for
the EPA and other stakeholders to evaluate the expected remedy cost and the expected
mass-removal effectiveness when making a remedy decision.
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None of the alternatives presented in the FFS would result in meeting the remediation
goals established in the original OU2 ROD for soil and groundwater concentrations.
The SVE pilot test at the Southwest Disposal Area (SWDA) was successful at removing
substantial mass and provides useful information for full-scale design.
Based on experience at other similar sites with SVE systems, the VOC mass removal
from SVE is likely to be significant but considerably lower than the PRP consultant's
estimate of 85 percent.
The cost estimate for full-scale SVE implementation as presented in the draft FFS could
be improved; the actual present-value cost of implementing SA-4 is expected to be closer
to $40 million.
Most of the potential human health and environmental risks at the Site appear to be
related to the groundwater contamination. In addition to the potential future use of
contaminated groundwater as a drinking water source, groundwater continues to supply
contaminants to Pugh Creek, Clover Creek, other tributaries, and wetlands. Also, a large
portion of the ambient and indoor air risks are driven by volatilization from contaminated
groundwater and from groundwater-fed surface water.
The GETS design was not optimal and operation was challenging and costly.
A more optimal design of the pump and treat remedy for hydraulic containment is
feasible and should be considered as a potential remedial alternative for OU1. An
improved treatment process design should be included in this alternative.
Several other potentially viable alternatives exist for containing the groundwater plume
nearer the source areas (for example, funnel-and-gate with permeable reactive barriers
(PRBs) and others).
Based on the Optimization Team's understanding of the CSM, and past reviews of many
other sites with pump and treat remediation systems, a well-designed and operated
groundwater containment remedy could substantially reduce concentrations
downgradient of the system, and lower concentrations could be realized throughout the
plume within 30 years. While it would likely take a much longer period of time to reach
MCLs downgradient of the containment system, risks (from groundwater, surface water,
and air exposure) would be substantially reduced sooner.
The overall exit strategy for this Site is unclear. According to the RODs, the goals are to
reduce concentrations to MCLs outside the disposal area footprints and to reduce soil
concentrations to concentrations that will not cause future MCL exceedances below the
disposal areas. With the GETS out of operation, there is no current remedial action for
groundwater and it does not appear that SVE systems contemplated for OU2 will achieve
all remedial goals.
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The SVE systems contemplated for OU2 will result in significant energy usage and there
will be an environmental footprint associated with implementing this remedy.
The SVE remedy presents job safety hazards for field teams that are more significant than
many sites, such as the requirement for protective suits and supplied air during drilling at
the disposal areas. Various measures can be implemented to address those risks.
Summary of Recommendations
Recommendations are provided to improve remedy effectiveness, reduce cost, provide technical
improvement, and assist with accelerating the Site exit strategy. The recommendations in these
areas are as follows:
Improving Effectiveness:
Select and implement an OU2 remedy that will address risks posed by the source material
present at the Site. Remedial action objectives should be developed based on policy and
what can be technically achieved.
Evaluate groundwater remedial alternatives and implement an OU1 remedy.
Continue to improve property controls through institutional controls.
Continue a monitoring program for ambient and indoor air.
Reducing Cost:
Evaluate OU2 implementation costs during remedial design.
Set performance goals for SVE so that the systems can be turned off when the rate of
mass removal is no longer significant.
Technical Improvement:
Define and document action levels for ambient air and indoor air.
Define and implement an ongoing groundwater monitoring program.
Develop and utilize a central data management system for environmental data.
Site Exit Strategy:
Develop a Site exit strategy that includes practical remedial measures at OU2 and OU1
along with remedial action objectives that are both protective and practical.
Also, it is recommended that the Site team consider ways that the environmental footprint of
remedy implementation can be limited for OU1 and OU2.
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NOTICE
Work described herein was performed by Tetra Tech for the U.S. Environmental Protection
Agency (EPA). Work conducted by Tetra Tech, including preparation of this report, was
performed under Work Assignment 2-48 of the EPA's Contract No. EP-W-07-078 with Tetra
Tech. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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PREFACE
This report was prepared as part of a national strategy to expand Superfund optimization from
remedial investigation to site completion implemented by the U.S. Environmental Protection
Agency (EPA) Office of Superfund Remediation and Technology Innovation (OSRTI). The
project contacts are as follows:
Organization
Key Contact
Contact Information
EPA Office of Superfund
Remediation and Technology
Innovation
(OSRTI)
lennifer Edwards
U.S. Environmental Protection Agency
Construction & Post Construction
Management Branch
1200 Pennsylvania Ave., NW
Washington, DC 20460
edwards j ennifer@epa.gov
Phone: 703-603-8762
Tetra Tech EM, Inc.
(Contractor to EPA)
Therese Gioia
Tetra Tech EM Inc.
1881 Campus Commons Drive, Suite 200
Reston,VA 20191
therese.gioia@tetratech.com
phone: 815-923-2368
Tetra Tech (GEO)
(Subcontractor to Tetra Tech EM,
Inc.)
Doug Sutton, PhD,
P.E.
Tetra Tech
2 Paragon Way
Freehold, NI 07728
phone: 732-409-0344
doug.sutton@tetratech.com
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LIST OF ACRONYMS AND ABBREVIATIONS
ARARs
bgs
CERCLA
cfm
coc
CSM
DNAPL
EPA
FFS
FS
ft
FTL
GAC
GETS
gpm
HP
KW
LTM
MCL
MDA
NAPL
NCP
NDA
NPL
O&M
OSRTI
OU
P&T
ppbv
PRP
RAO
RCRA
RI
ROD
RSE
Micrograms per kilogram
Micrograms per liter
mmicrograms per cubic meter
Applicable or relevant and appropriate requirements
Below ground surface
Comprehensive Environmental Response, Compensation, and Liability Act
Cubic feet per minute
Contaminant of concern
Conceptual site model
Dense non-aqueous phase liquid
U.S. Environmental Protection Agency
Focused feasibility study
Feasibility study
Feet
Fruit-of-the-Loom Custodial Trust
Granular activated carbon
Groundwater Extraction and Treatment System
Gallons per minute
Horsepower
Kilowatt
Long-term monitoring
Maximum contaminant level
Middle Disposal Area
Non-aqueous phase liquid
National Oil and Hazardous Substances Pollution Contingency Plan
North Disposal Area
National Priorities List
Operation and maintenance
Office of Superfund Remediation and Technology Innovation
Operable unit
Pump and treat
Parts per billion by volume
Potentially Responsible Party
Remedial action objective
Resource Conservation and Recovery Act
Remedial investigation
Record of Decision
Remediation system evaluation
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SAL Soil action level
SEDA Southeast Disposal Area
SVE Soil vapor extraction
SVOC Semi-volatile organic compound
SWDA Southwest Disposal Area
SWSWDA Southwest-Southwest Disposal Area
TDEC Tennessee Department of Environment and Conservation
UAO Unilateral Administrative Order
USGS United States Geological Survey
VGAC Vapor granular activated carbon
VOC Volatile organic compound
yr Year
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TABLE OF CONTENTS
EXECUTIVE SUMMARY i
NOTICE viii
PREFACE ix
LIST OF ACRONYMS AND ABBREVIATIONS x
1.0 INTRODUCTION 1
1.1 PURPOSE 1
1.2 SITE-SPECIFIC SCOPE OF OPTIMIZATION 3
1.3 TEAM COMPOSITION 3
1.4 DOCUMENTS REVIEWED 4
1.5 QUALITY ASSURANCE 5
1.6 PERSONS CONTACTED 5
2.0 SITE BACKGROUND 7
2.1 LOCATION 7
2.2 SITE HISTORY 7
2.2.1 HISTORIC LAND USE AND OPERATIONS 7
2.2.2 CHRONOLOGY OF ENFORCEMENT AND REMEDIAL ACTIVITIES 8
2.3 POTENTIAL HUMAN AND ECOLOGICAL RECEPTORS 9
2.4 EXISTING DATA AND INFORMATION 10
2.4.1 SOURCES OF CONTAMINATION 10
2.4.2 GEOLOGIC SETTING AND HYDROGEOLOGY 10
2.4.3 SOIL CONTAMINATION 11
2.4.4 GROUNDWATER CONTAMINATION 11
2.4.5 SURFACE-WATER CONTAMINATION 11
2.4.6 AMBIENT AIR AND INDOOR AIR CONTAMINATION 12
3.0 DESCRIPTION OF PLANNED OR EXISTING REMEDIES 13
3.1 REMEDY AND REMEDY COMPONENTS 13
3.1.1 ALTERNATIVE WATER SUPPLY 13
3.1.2 LANDFILL CAPS 13
3.1.3 GROUNDWATER PUMP AND TREAT SYSTEM 13
3.1.4 INSTITUTIONAL CONTROLS AND ACCESS CONTROLS 14
3.1.5 VAPOR MITIGATION SYSTEMS 14
3.1.6 SVE 14
3.2 RAOs AND STANDARDS 14
3.3 PERFORMANCE MONITORING PROGRAMS 15
4.0 CONCEPTUAL SITE MODEL 16
4.1 CSM OVERVIEW 16
4.2 CSM DETAILS AND EXPLANATION 16
4.2.1 SOURCE AREAS 16
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4.2.2 CONTAMINANT MIGRATION PATHWAYS 16
4.2.3 CONTAMINANT FATE 17
4.2.4 POTENTIAL EXPOSURE ROUTES 17
4.3 DATA COMPLETENESS 18
5.0 FINDINGS 19
5.1 CONTAMINANT MASS AND LOCATION 19
5.2 RISKS FROM DIFFERENT AREAS OF CONTAMINATION 20
5.2.1 SOURCE AREAS 20
5.2.2 GROUNDWATER 20
5.2.3 SURFACE WATER 21
5.2.4 AMBIENT AIR 21
5.2.5 INDOOR AIR 22
5.3 EXISTING RISK-MITIGATION MEASURES 22
5.4 POTENTIAL ADDITIONAL MEASURES TO ADDRESS LANDFILL SOURCES (OU2) 23
5.4.1 OU2 FEASIBILITY STUDY 23
5.4.2 COMPARING EFFECTIVENESS FOR ALTERNATIVES S A-4 AND S A-5 24
5.4.3 ARAR COMPLIANCE AND WAIVERS 25
5.4.4 SVE PILOT TEST 25
5.4.5 ASSESSMENT OF SVE BENEFITS AND SHORTCOMINGS 25
5.4.6 SELECTION OF SVE AS OU2 FINAL REMEDY 26
5.4.7 FS COST ESTIMATE FOR S A-4 26
5.5 GROUND WATER CONTAINMENT AND RESTORATION (OU1) 28
5.5.1 IMPORTANCE OF THE GROUND WATER PATHWAY 28
5.5.2 PRIOR PUMP AND TREAT REMEDY 28
5.5.3 IMPROVED PUMP AND TREAT ALTERNATIVE 29
5.5.4 OTHER ALTERNATIVES FOR OU1 29
5.5.5 EXPECTED EFFECTIVENESS 30
5.6 SITE EXIT STRATEGY 30
5.7 ENVIRONMENTAL FOOTPRINTS OF REMEDIAL MEASURES 30
5.8 HEALTH AND SAFETY 30
6.0 RECOMMENDATIONS 31
6.1 RECOMMENDATIONS TO IMPROVE EFFECTIVENESS 31
6.1.1 COMPLETE THE OU2 REMEDY DECISION WITH CLEAR RAOs 31
6.1.2 EVALUATE GROUNDWATER REMEDIAL ALTERNATIVES AND IMPLEMENT AN
OU1 REMEDY 32
6.1.3 CONTINUE TO IMPROVE PROPERTY CONTROLS 33
6.1.4 CONTINUE TO MONITOR AMBIENT AIR AND INDOOR AIR 33
6.2 RECOMMENDATIONS TO REDUCE COSTS 33
6.2.1 EVALUATE OU2 IMPLEMENTATION COSTS DURING REMEDIAL DESIGN 34
6.2.2 SET PERFORMANCE GOALS FOR SVE 34
6.3 RECOMMENDATIONS FOR TECHNICAL IMPROVEMENT 34
6.3.1 DEFINE AND DOCUMENT ACTION LEVELS FOR AMBIENT AIR AND INDOOR
AIR 34
6.3.2 DEFINE A GROUNDWATER MONITORING PROGRAM 35
6.3.3 ESTABLISH AND USE A DATA MANAGEMENT SYSTEM 35
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6.4 CONSIDERATIONS FOR ACHIEVING SITE CLOSE OUT 35
6.4.1 DEVELOP A SITE EXIT STRATEGY 35
6.4.2 UPDATE THE OU1 AND OU2 RODS 35
6.5 RECOMMENDATIONS RELATED TO GREEN REMEDIATION 36
6.6 SUGGESTED APPROACH TO IMPLEMENTING RECOMMENDATIONS 36
List of Tables
Table 5-1. Remedial Alternatives Summary from the Draft FFS 24
Table 6-1. Recommendations Summary 37
Attachments
Attachment A: Site Figures provided by Environ
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1.0 INTRODUCTION
1.1 PURPOSE
During fiscal years 2000 and 2001 independent Remediation System Evaluations (RSEs) were
conducted at 20 operating pump and treat (P&T) sites (those sites with P&T systems funded and
managed under Superfund by the U.S. Environmental Protection Agency [EPA], other federal
agencies, and by the States). Due to the opportunities for system optimization that arose from
those RSEs, the EPA Office of Superfund Remediation and Technology Innovation (OSRTI) has
incorporated RSEs into a larger post-construction completion strategy for Fund-lead remedies as
documented in OSWER Directive No. 9283.1-25, Action Plan for Ground Water Remedy
Optimization. Concurrently, the EPA developed and applied the Triad Approach to optimize site
characterization strategies, methods and technologies, including the increased use of conceptual
site models (CSMs) as the basis for identifying project data gaps, and using those gaps to guide
the development of site characterization objectives and work plans. The EPA has since expanded
the reach of optimization to encompass reviews at the investigation stage of projects. The EPA's
definition of optimization is as follows:
"Efforts at any phase of the removal or remedial response to identify and implement actions that
improve the action's effectiveness and cost-efficiency. Such actions may also improve the
remedy 'sprotectiveness and long-term implementability which may facilitate progress towards
site completion. To identify these opportunities, regions may use a systematic site review by a
team of independent technical experts, apply techniques or principles from green remediation or
Triad, or apply some other approach to identify opportunities for greater efficiency and
effectiveness. Contractors, states, tribes, the public, and potentially responsible parties (PRPs)
are also encouraged to put forth opportunities for the Agency to consider. "
The Strategy also encourages other activities designed to facilitate better site characterization,
remedy selection, and design and construction by applying various techniques and optimization
lessons learned to improve a given project's scope, schedule and cost.
As stated in the definition, optimization refers to a "systematic site review," indicating that the
site as a whole is often considered in the review. Optimization can be applied to a specific aspect
of the remedy (such as, focus on long-term monitoring [LTM] optimization or focus on one
particular operable unit [OU]), but other site or remedy components are still considered to the
degree that they affect the focus of the optimization. An optimization evaluation considers the
goals of the remedy, available site data, CSM, remedy performance, protectiveness, cost-
effectiveness, and exit strategy. A strong interest in sustainability has also developed in the
private sector and within Federal, State, and Municipal governments. Consistent with this
interest, OSRTI has developed a Green Remediation Primer (http://cluin.org/greenremediation/),
and now routinely considers green remediation and environmental footprint reduction during
optimization evaluations. The evaluation includes reviewing site documents, potentially visiting
the site for one day, and compiling a report that includes recommendations in the following
categories:
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Protectiveness
Cost-effectiveness
Technical improvement
Site exit strategy
Environmental footprint reduction
The recommendations are intended to help the site team identify opportunities for improvements
in these areas. In many cases, further analysis of a recommendation, beyond that provided in this
report, may be needed prior to implementation of the recommendation. Note that the
recommendations are based on an independent evaluation, and represent the opinions of the
evaluation team. These recommendations do not constitute requirements for future action, but
rather are provided for consideration by the Region and other site stakeholders. Also note that
while the recommendations may provide some details to consider during implementation, the
recommendations are not meant to replace other, more comprehensive, planning documents such
as work plans, sampling plans, and quality assurance project plans.
The national optimization strategy includes a system for tracking consideration and
implementation of the optimization recommendations and includes a provision for follow-up
technical assistance from the Optimization Team as mutually agreed upon by the site
management team and EPA OSRTI staff.
The Velsicol Chemical Corporation Hardeman County Landfill Superfund Site (Site) is located
in a rural area near the town of Toone in western Tennessee. The Site includes approximately 24
acres of capped landfill area within a 237 acre property parcel. Between 130,000 and 300,000
drums of chemical wastes from Velsicol's pesticide manufacturing plant in Memphis were
disposed of in unlined trenches at the Site between 1964 and 1973. The drums and other
containers of waste were dumped in the trenches and the trenches were backfilled. Years later (in
1980) a clay cap was placed over the disposal areas, and even later (1997) a multi-layer
composite cap was placed over the clay cap.
The wastes included pesticides and chemicals used in the production of pesticides. Carbon
tetrachloride and other volatile organic compounds (VOCs) made up a substantial portion of the
wastes (a PRP contractor, Environ, estimates 1 percent to 5 percent of the total volume) and have
been the most mobile contaminants at the Site. Pesticides and semi-volatile organic compounds
(SVOCs) are also chemicals of concern (COCs), primarily for soil within and below the buried
waste.
A 1,700-acre groundwater plume emanates from the disposal areas and discharges into
downgradient streams and wetlands. The primary contaminant in groundwater is carbon
tetrachl oride, which has a maximum contaminant level (MCL) of 5 micrograms per liter (|ig/L).
Measured concentrations over a large portion of the plume (900 acres) exceed 5,000 |ig/L and
concentrations as high as 64,000 |ig/L have been recorded. The plume is almost entirely within
an upper unconfined aquifer layer that is approximately 50 feet (ft) thick. There is limited
contamination in the underlying leaky confined aquifer. The plume is stable in size because it has
already reached its lateral and downgradient discharge locations.
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There are approximately 35 residences located within the area of the groundwater plume (the
groundwater beneath these residences has concentrations that exceed remediation goals).
Ambient air and indoor air concentrations of carbon tetrachloride are elevated relative to
background within the plume area, and indoor-air mitigation systems have been installed at two
residences (in 2007). Some measured concentrations in ambient air have been above calculated
risk-based screening levels based on an excess cancer risk of 10"4 (the upper end of the EPA's
acceptable risk range).
Concentrations are also elevated in surface water near plume discharge locations. The
concentrations are above Tennessee surface water quality criteria. However, Site-specific risk
assessments have concluded that surface-water exposure routes do not present significant human
health or environmental risks.
1.2 SITE-SPECIFIC SCOPE OF OPTIMIZATION
The optimization review of this Site includes a comprehensive review of the CSM, existing soil
and waste remedies, soil vapor extraction (SVE) pilot studies, and potential remedial alternatives
for soil. In particular, the review covers the following:
Review of the existing Records of Decision (RODs), Five-Year Reviews, 2007
Feasibility Study, SVE pilot test results, 2011 draft Focused Feasibility Study for
landfills, progress reports, geophysical data, soil gas data, landfill cap and
characterization information
Review of SVE as a potential Site-wide soil remedy
Considerations for SVE design and implementation
Consideration of other potential remedial alternatives
While the focus of this review is on potential soil/waste remediation, an initial review of
potential groundwater remediation is also considered.
1.3 TEAM COMPOSITION
The Optimization Team consisted of the following individuals:
Name
Jennifer Hovis
Edward Gilbert
Greg Council
Peter Rich
Affiliation
EPA HQ/OSRTI
EPAHQ/OSRTI
Tetra Tech
Tetra Tech
Phone
703-603-8888
703-603-8883
770-619-9950
410-990-4607
Email
hovis.iennifer(a)epa.sov
silbert. edward(3)epa. sov
sres . council (SHetratech . com
peter.rich(3)tetratech. com
In addition, Doug Sutton from Tetra Tech assisted with project direction.
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1.4 DOCUMENTS REVIEWED
The following documents were scanned or reviewed. The reader is directed to these documents
for additional Site information that is not provided in this report.
Operable Unit #1 ROD (EPA - June 1991)
Operable Unit #2 ROD (EPA - September 1995)
Five-Year Review (EPA - September 2000)
Second Five-Year Review (EPA - September 2006)
Third Five-Year Review (EPA - April 2011)
Post Second Five-Year Review Feasibility Study (Environ - June 2007)
Supplemental Remedial Alternative Evaluation Letter (Environ - April 2010)
Annual Progress Report-2010 (Environ - 2011)
Revised Human Health Risk Assessment (Environ - March 2011)
Super fund Fact Sheets (Environ - 2004 thru 2011)
Third Quarter Progress Report-2010, Velsicol Chemical Corp., Hardeman County
Landfill, OUs #1 and #2 (Environ - March 2011)
Fourth Quarter Progress Report-2010, Velsicol Chemical Corp., Hardeman County
Landfill, OUs #1 and #2 (Environ - March 2011)
Revised First Quarter Progress Report-2011, Velsicol Chemical Corp., Hardeman
County Landfill,OUs #1 and#2 (Environ - September 2011)
Second Quarter Progress Report-2011, Velsicol Chemical Corp., Hardeman County
Landfill, OUs #1 and #2 (Environ - August 2011)
Third Quarter Progress Report-2011, Velsicol Chemical Corp., Hardeman County
Landfill, OUs #1 and #2 (Environ - October 2011)
Summary of Surface Geophysical Investigation Results for the SWSWDA (Environ - May
2011)
Summary of Surface Geophysical Investigation Results Suspect Trench Areas - Areas 1
through 9 (Environ - June 2011)
Summary of Surface Geophysical Investigation Results Suspect Trench Areas - Areas 1
through 9 (Environ - September 2011)
Soil Vapor Extraction Pilot Test Options (Environ - April 2008)
Soil Vapor Extraction Pilot Test Study Work Plan Part 1. Pre-Design Activities (Environ -
September 2008)
Soil Vapor Extraction Pilot Test Study Work Plan Part 2. Design and Installation
(Environ - March 2009)
2008 Soil Gas Sampling Results Technical Memorandum (Environ - February 2010)
Soil Vapor Extraction Pilot Test Operation, Maintenance, and Monitoring Manual
(Environ - January 2011)
Soil Vapor Extraction Pilot Test Construction Completion Report (Environ - January
2011)
Phase IISVE Pilot Test Conceptual Design and Cost Estimate (Environ - September
2011)
Phase II SVE Pilot Test Design Submittal 1: Well Installation and Sampling Velsicol
Chemical Corp. Hardeman County Landfill, OU#2 (Environ - November 2011)
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Phase IISVE Pilot Test Design Submittal 3: Soil Gas Sampling & System Startup
(Environ - January 2012)
Landfill Cap as Built Plans (Conestoga-Rovers & Associates - December 1980)
Feasibility Study (Conestoga-Rovers & Associates - April 1991)
Remedial Investigation Report, Volume I - Text (Conestoga-Rovers & Associates - April
1991)
Landfill Waste Sampling and Data Evaluation Report fConestoga-Rovers & Associates -
May 1993)
Feasibility Study (Conestoga-Rovers & Associates - June 1995)
Landfill RCRA Cap Technical Memorandum- Electromagnetic Survey Results for OU2
(Conestoga-Rovers & Associates - July 1996)
Landfill Cap Construction Report (Conestoga-Rovers & Associates - January 1998)
Groundwater Flow & Particle Tracking Analysis (EPA - 2006)
2008 Ambient Air Sampling Report for the Velsicol Chemical Corp. Hardeman County
Landfill Site (Environ - September 2009)
Draft Focused Feasibility Study: OU2 Landfill Disposal Areas (Environ - January 2012)
Phase II SVE Pilot Test Design Submittal 1: Design Basis and Mechanical Component
Specifications: Velsicol Chemical Corp. Hardeman County Landfill, OU#2 (Environ -
December 2011)
Soil Gas and Indoor Air Investigation: Technical Memorandum (Environ - February
2006)
August 2007 Air Sampling Results Update (Environ - September 2007)
October 2007 Air Sampling Results Update (Environ - January 2008)
1.5 QUALITY ASSURANCE
This optimization review utilizes existing environmental data to interpret the CSM, evaluate
remedy performance, and make recommendations to improve the remedy. The quality of the
existing data is evaluated by the Optimization Team prior to using the data for these purposes.
The evaluation for data quality includes a brief review of how the data were collected and
managed (where practical, the site Quality Assurance Project Plan is considered), the consistency
of the data with other site data, and the use of the data in the optimization review. Data that are
of suspect quality are either not used as part of the optimization review or are used with the
quality concerns noted. Where appropriate, this report provides recommendations made to
improve data quality.
1.6 PERSONS CONTACTED
A stakeholders meeting was held on January 18, 2012, at the Site and at the Jackson field office
of the Tennessee Department of Environment and Conservation (TDEC). In addition to the
Optimization Team, the following persons were present for the stakeholders meeting and Site
visit:
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Name Affiliation Email Address
JohnNolen EPA Region 4 (Project Manager) nolen.john@epa.gov
Ron Sells TDEC james.ron.sells@tn.gov
Jay Steinberg Fruit-of-the-Loom Custodial Trust (FTL) (not given)
David Heidlauf Environ (consultant for FTL) dheidlauf@environcorp.com
Michael Bradley United States Geological Survey (USGS) mbradley@usgs.gov
Don Sprinkle of TDEC was also present for a portion of the meeting at the TDEC office.
Mr. Heidlauf was subsequently contacted by the Optimization Team with a few follow-up
questions. A conference call was also held between the Optimization Team and Site stakeholders
on February 15, 2012, to discuss preliminary findings of the Optimization Team.
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2.0 SITE BACKGROUND
2.1 LOCATION
The Site is located in a hilly, rural area of Hardeman County, Tennessee, approximately 2 miles
north-northeast of the town of Toone and approximately 60 miles east-northeast of Memphis.
There are five defined landfills at the Site, called the North Disposal Area (NDA), the Middle
Disposal Area (MDA), the Southeast Disposal Area (SEDA), the Southwest Disposal Area
(SWDA), and the Southwest-Southwest Disposal Area (SWSWDA). The relatively small
SWSWDA was recently discovered; the other landfill areas have been capped. These landfill
areas occupy approximately 24 acres of a 237-acre parcel just east of Old Toone Road about
1 mile north of state route 100. The NDA is by far the largest disposal area and most significant
contaminant source.
A groundwater plume of carbon tetrachloride and other contaminants emanates from the landfills
and stretches northward and northwestward for a distance of over 1.5 miles. The groundwater
plume ends at natural discharge points along and near Clover Creek (northern plume boundary),
Pugh Creek (eastern plume boundary) and other tributaries (for example, the unnamed creek
along the western plume boundary). The plume covers approximately 1,700 acres. It has been
noted in previous documents (including the 2011 Five-Year Review report) that the plume is
stable in size. The plume is stable because it has already reached lateral and downgradient
discharge locations at streams and streamside seeps and wetlands. There are approximately 35
residences within the groundwater plume area. Most of the area is forested; there are significant
areas of wetlands in the lowlands along the streams; and some of the land is used for agriculture.
2.2 SITE HISTORY
2.2.1 HISTORIC LAND USE AND OPERATIONS
Between 130,000 and 300,000 drums of chemical wastes from Velsicol's pesticide
manufacturing plant in Memphis were disposed of in unlined trenches at the Site between 1964
and 1973. Using the low end of this estimate, and multiplying by 55 gallons per drum, this
equates to an estimate of over 7 million gallons of chemical waste. The drums and other
containers of waste were dumped in the trenches and the trenches were backfilled. Later (in
1980) a clay cap was placed over the disposal areas, and even later (1997) a multi-layer
composite cap was placed over the clay cap.
The wastes included pesticides and chemicals used in the production of pesticides. Carbon
tetrachloride and other volatile organic compounds (VOCs) made up a substantial portion of the
wastes (a PRP contractor, Environ, estimates 1 percent to 5 percent of the total volume) and have
been the most mobile contaminants at the Site. Pesticides and semi-volatile organic compounds
(SVOCs) are also chemicals of concern (COCs).
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2.2.2 CHRONOLOGY OF ENFORCEMENT AND REMEDIAL ACTIVITIES
The USGS identified the likelihood of waste releases to groundwater at the Site by 1967. In
1979, after groundwater was found to be contaminated, Velsicol began providing an alternative
water source to affected residents. A clay cap was constructed over the disposal areas in 1980 by
a Velsicol contractor. The Site was added to the National Priorities List (NPL) in 1983.
Two operable units (OUs) were defined for the Site:
OU1 is contaminated groundwater
OU2 is the waste and underlying contaminated soil
In 1991, a ROD was finalized by the EPA for OU1 specifying a groundwater pump and treat
remedy. Velsicol was directed to design and implement the selected groundwater remedy
through a Unilateral Administrative Order (UAO).
Velsicol's contractor began construction of a Groundwater Extraction and Treatment System
(GETS) north of the disposal areas in 1995. The system became fully operational in November
1997 and operated until November 2003 (approximately six years) at an average flow of less
than 250 gallons per minute (gpm), which was approximately half of the design flow. Several of
the GETS wells extracted some water from the leaky confined aquifer which was relatively clean
compared with the shallower unconfmed aquifer. A total of 796 million gallons of water were
treated by the GETS and 110,000 pounds of VOCs were removed. The average influent
concentration of VOCs was approximately 17,000 |ig/L.
Numerous difficulties were experienced in GETS operation. The system was also not as effective
as expected in reducing plume concentrations to remedial goals and an EPA analysis suggested
that it would take 100 years or more to reach MCLs in the downgradient portion of the plume
even with effective hydraulic containment near the sources and assuming no non-aqueous phase
liquid (NAPL) in groundwater.
In 1995, a ROD was finalized for OU2, and a RCRA-style, multi-layer composite cap (on top of
the existing clay cap) was specified as the remedy for the known disposal areas (NDA, MDA,
SEDA, and SWDA). The cap was intended to eliminate the ongoing source of contamination to
groundwater and prevent direct human contact with waste or soil exceeding risk-based soil
action levels (SALs). Velsicol was directed to design and implement the source-area remedy
through a UAO. The caps were constructed in 1997.
By 2001, through corporate transactions, the Site's potentially responsible party (PRP) became
Fruit-of-the-Loom Corporation. In 2002, a bankruptcy settlement established the Fruit-of-the-
Loom Custodial Trust (FTL), and this entity became the Site PRP.
In 2007, vapor mitigation systems were installed by Environ (the current PRP consultant and
contractor) at two homes located within the area of the groundwater plume that were found to
have indoor air concentrations in excess of risk-based action levels. The mitigation systems
include crawlspace vapor barriers, vapor collection pipes below the barriers, vent pipes, and fans.
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Over a period of many years, institutional controls to prevent groundwater use have been
obtained for 56 of 60 parcels within the groundwater plume, covering approximately 86 percent
of the plume area.
In 2009-2011, an SVE pilot test was conducted at the SWDA over a period of 28 months. The
SVE pilot test removed approximately 31,000 pounds of VOCs from the waste zone and the
underlying vadose zone.
The EPA issued five-year review reports in 2000, 2006, and 2011. The 2011 five-year review
concluded that neither OU1 nor OU2 have been remediated as intended in their respective RODs
and that, as a result, the Site remedies implemented are not protective of human health and the
environment.
As this optimization review was being conducted, the EPA was contemplating a full-scale SVE
remedy for OU2, based on results of the recent pilot test and a draft Focused Feasibility Study
(FFS) for OU2 issued by Environ on behalf of the PRP in January 2012.3 A Feasibility Study
(FS) that included remedial alternatives for both OU1 and OU2 was previously prepared by
Environ in 2007.
The EPA has not fully developed a new remedial strategy for OU1. The EPA expects to address
OU1 after finalizing a new ROD for OU2.
2.3 POTENTIAL HUMAN AND ECOLOGICAL RECEPTORS
The primary receptors of potential concern are current and future residents within the area of the
groundwater plume. The residents may potentially be exposed to groundwater, surface water,
ambient air, and indoor air with elevated concentrations of VOCs, primarily carbon tetrachloride.
Other recreational users such as hunters and fisherman are also potential receptors. Organisms in
the streams and wetlands are potential ecological receptors.
The Toone public water supply (not impacted by the Site) is available to residents in the plume
area and institutional controls have been established to prevent current and future residents from
using contaminated groundwater at most (but not all) properties within the plume. The PRP also
owns a substantial portion of the plume-area property.
Vapor mitigation systems have been installed at the two homes within the plume where indoor
air concentrations of carbon tetrachloride have been found to be of potential concern. These
systems require continuous fan operation and periodic inspection and maintenance.
At several locations, ambient air concentrations have been measured near and above calculated
risk-based action levels for carbon tetrachloride. Slightly different action levels have been used
or proposed by Environ for ambient air and indoor air based on different sets of exposure
assumptions and updated toxicity assessments. All of these action levels are based on an excess
3 Since completion of the optimization review and the initial draft of this report, the FFS has been revised and a
ROD amendment has been completed for OU2. The ROD specifies SVE in all disposal areas.
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cancer risk of 10~4 which is the upper end of USEPA's risk range. Based on the available data,
when averaged over time and space, ambient air concentrations in the plume areas likely less
than concetnrations associated with the 10~4 risk level.
Risk assessments completed prior to the original RODs for the Site, as well as subsequent risk
assessments from Environ, indicate that:
(1) Ecological receptors are not expected to be adversely impacted by Site contaminants;
(2) Exposures associated with occasional recreational uses of the streams and land above the
plume are not likely to lead to significant increased human health risk; and
(3) Consumption offish from impacted streams is not likely to lead to significant increased
human health risk.
2.4 EXISTING DATA AND INFORMATION
The information provided in this section is intended to represent data already available from
existing Site documents. Interpretation included in this section is generally interpretation from
the document from which the information is obtained. The Optimization Team's interpretation of
this data is discussed in Sections 4.0 and 5.0 of this report.
2.4.1 SOURCES OF CONTAMINATION
Buried wastes at the five disposal areas (NDA, MDA, SEDA, SWDA, and SWSWDA) are the
sources of contamination at the Site. The wastes are buried in the interval from approximately 5
to 20 feet below the current land surface (which is the top of the cap in most places).
Contaminated soil and NAPL in the vadose zone below the waste is a secondary source that can
leach contaminants to the underlying saturated groundwater zone. The water table is
approximately 90-100 feet below land surface at the disposal areas.
2.4.2 GEOLOGIC SETTING AND HYDROGEOLOGY
The following descriptions of the Site geology and hydrogeology are obtained from the 1991
Remedial Investigation report, the OU1 ROD, and more recent reports by Environ.
The Site is located on alluvial/fluvial/deltaic deposits near the eastern edge of the Mississippi
Embayment within the Gulf Coastal Plain. The uppermost Quaternary alluvial deposits and
underlying Claiborne and Wilcox Formations have similar compositions: mostly interbedded
quartz sand with discontinuous strata of silts and clays. Some thin kaolin layers are present in
these formations. These sandy units are over 100 feet thick at the Site and are underlain by the
Porter's Creek Clay.
At the time of the OU1 ROD, the entire saturated portion of the combined Claiborne-Wilcox
Formation was thought to be a single continuous aquifer unit bounded at the base by the Porter's
Creek Clay aquitard. Subsequent hydrogeologic investigations revealed that this aquifer unit was
more accurately described by an upper unconfined aquifer layer and an underlying leaky
confined aquifer, with limited transmission of water between the two layers due to the presence
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of a clayey semi-confining layer. The semi-confining layer is found throughout most of the
plume area but is suspected to be absent or discontinuous in at least one location: north of the
NDA near the original GETS source-control extraction wells.
The groundwater contamination at the Site is much greater in the unconfmed aquifer layer above
the semi-confining layer. The unconfmed aquifer layer is approximately 50 ft thick on average.
The lower leaky confined aquifer layer does have some areas of groundwater contamination,
especially near the suspected discontinuity in the overlying semi-confining unit; however,
contaminant concentrations are much lower in the leaky confined aquifer layer than in the
unconfmed aquifer layer.
2.4.3 SOIL CONTAMINATION
As part of the 1995 OU2 ROD, Soil Action Levels (SALs) were set for Site COCs for direct
contact and for prevention of leaching to groundwater that would likely lead to an exceedance of
groundwater remediation levels. Data collected in 2005 indicate that the SALs protective of
groundwater are exceeded outside cap areas at multiple locations for four VOCs: carbon
tetrachloride, chloroform, methylene chloride, and acetone.
2.4.4 GROUNDWATER CONTAMINATION
A 1,700-acre plume of contamination emanates from the disposal areas and is bounded at
surface-water discharge locations (streams and stream-side wetlands). Based on 2008
measurements, concentrations of carbon tetrachloride in groundwater exceed 5,000 |ig/L (1,000
times the MCL) over approximately 900 acres and concentrations exceed 30,000 |ig/L at three
wells north of the NDA (two that were previously part of the GETS).
2.4.5 SURFACE-WATER CONTAMINATION
The highest concentrations of carbon tetrachloride in surface water are found in Pugh Creek and
small tributaries into Pugh Creek north of the source areas. In 2010-2011, a concentration of
26,000 |ig/L was measured in a small tributary to Pugh Creek. A concentration of 6,100 |ig/L
was measured in 2004-2005 at Pugh Creek less than 1,000 ft northwest of the NDA. At that time,
concentrations persisted near and above 100 |ig/L from that point to the confluence with Clover
Creek. However, concentrations in Clover Creek downgradient of the groundwater plume
discharge locations were below MCLs and below water quality criteria for all surface-water use
designations. For carbon tetrachloride, Tennessee water quality criteria are 5 |ig/L for surface
water that may be used as a domestic water supply, 16 jig/L for recreational use (including
fishing) of surface water (organisms only criteria), and 2.3 |ig/L for surface waters designated for
both domestic and recreational use; other water use designations do not have specific criteria for
carbon tetrachloride.
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2.4.6 AMBIENT AIR AND INDOOR AIR CONTAMINATION
The ambient (outdoor) air at the Site has elevated levels of carbon tetrachloride. A few
measurements of ambient air concentration in 2007-2008 exceeded the risk-based screening level
of 5.2 parts per billion by volume (ppbv) (which represented a 10"4 cancer risk using certain
exposure and toxicity assumptions) presented in the 2008 Annual Ambient Air Report. This
ambient-air screening level was twice the presented indoor-air screening level of 2.6 ppbv based
on an assumption that ambient air exposure is only applicable outdoors and that 12 hours per day
are spent outdoors. The OU2 FFS provides an updated risk-based criterion of 6.5 ppbv for
carbon tetrachloride in ambient and indoor air based on updated toxicity information.
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3.0 DESCRIPTION OF PLANNED OR EXISTING REMEDIES
The information provided in this section is intended to represent information available from
existing Site documents. Interpretation included in this section is generally interpretation from
the document from which the information is obtained. The Optimization Team's interpretation of
this information and evaluation of remedy components are discussed in Sections 4.0 and 5.0 of
this report.
3.1 REMEDY AND REMEDY COMPONENTS
The Site remedy has consisted of several remedy components specified in the 1991 ROD for
OU1, the 1995 ROD for OU2, and additional interim measures. These components are described
in the following subsections.
3.1.1 ALTERNATIVE WATER SUPPLY
Velsicol began providing an alternative source of water to plume-area residents in 1979. The
water supply system from the City of Toone has been expanded to provide a replacement source
for well-water users in the groundwater plume.
3.1.2 LANDFILL CAPS
In 1980, a clay cap was installed over the disposal areas (except the SWSWDA), on top of the
existing waste covers and backfill. A majority of the area above disposal areas was capped at that
time. Pursuant to the OU2 ROD, a more impermeable multi-layer composite cap was installed in
1997. This cap included a low-density polyethylene (LDPE) liner, drainage layer, and well-
vegetated soil cover. The caps limit infiltration and thus reduce the potential for leaching from
the wastes and underlying soils into groundwater. However, migration to groundwater can still
occur via NAPL drainage and soil-vapor transport.
3.1.3 GROUNDWATER PUMP AND TREAT SYSTEM
The GETS was constructed in 1996 and operated for 6 years. It removed 110,000 pounds of
VOCs while treating 796 million gallons of water. The average withdrawal rate of less than 250
gpm was much less than the design objective of 465 gpm. The extraction wells were screened in
both the unconfined aquifer and in the underlying and relatively clean confined aquifer. The
average concentration of VOCs in the influent was approximately 17,000 |ig/L.
The GETS treatment system consisted of in-well chlorination (to prevent biofouling), air
stripping, and granular activated carbon (GAC) polishing. GETS effluent was discharged to Pugh
Creek. Vapors were treated in a vapor-phase regenerative GAC (VGAC). Operation and
maintenance of the groundwater treatment system was challenging and costly.
The GETS has been shut down since 2003.
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3.1.4 INSTITUTIONAL CONTROLS AND ACCESS CONTROLS
Fences have been installed around the disposal areas to limit human access to the source areas.
Institutional controls in the form of deed restrictions to prevent groundwater use have been
obtained for 56 of 60 parcels within the plume, covering approximately 86 percent of the plume
area.
3.1.5 VAPOR MITIGATION SYSTEMS
In 2007, indoor vapor mitigation systems were installed to control indoor air concentrations at
two homes approximately 1 mile north of the NDA, in a low-lying area where the vadose zone is
thin. The mitigation systems include crawlspace vapor barriers, vapor collection pipes below the
barriers, vent pipes, and fans.
3.1.6 SVE
An SVE pilot test was conducted with eight SVE well nests and one additional SVE well at the
SWDA over a period of 28 months (approximately 10,000 operation hours). The SVE pilot test
removed approximately 31,000 pounds of VOCs from the area and provided Site-specific data
for design at the other disposal areas.
3.2 RAOs AND STANDARDS
Page 6 of the 1991 OU1 ROD indicates that the scope of the response action is "to address the
off-Site groundwater contamination and prevent additional contamination from leaving the
disposal areas via migration through the groundwater." This section of the ROD further states
that the selected remedy for OU1 will address the remediation of contamination in the
groundwater beyond the disposal-area boundaries prior to discharge into the nearby surface
water bodies of Clover and Pugh Creeks.
Section 2.4 of 1995 OU2 ROD identifies two remedial action objectives for the waste disposal
areas including soils directly beneath the wastes:
i) Prevent human exposure through direct contact or ingestion of landfill wastes or soils
directly beneath the wastes which have chemical constituent concentrations in excess of
calculated, risk-based, direct-contact criteria levels (identified in Table 2.8 of the OU2
ROD); and
ii) Prevent further degradation of the groundwater beneath and downgradient of the waste
disposal areas by chemical constituents found within the waste.
The OU1 and OU2 RODs identify applicable or relevant and appropriate requirements (ARARs)
and list associated concentration standards as remediation goals:
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1. The OU1 ROD identifies MCLs as ARARs and sets groundwater cleanup levels to MCLs
for all COCs with MCLs. For carbon tetrachloride, the remediation goal in groundwater
is 5 ng/L. Remediation goals for contaminants without an MCL were based on risk
calculations at a 10~6 excess risk level.
2. The OU1 ROD also identifies certain Tennessee in-stream water-quality criteria as
ARARs and lists these criteria as interim surface-water discharge limits for several
COCs. For carbon tetrachloride, the discharge concentration limits were listed as 5 jig/L
and 44 |ig/L for chronic and acute exposures, respectively.
3. The OU2 ROD identifies soil action levels (SALs) for both protection of groundwater
and for direct-contact exposure. The direct-contact SALs are applicable only to surface
soil and do not apply to covered or capped waste and soil. The ground water-protection
SALs were calculated for both the waste zone and underlying soil zone based on
preventing leachate concentrations that would lead to an MCL exceedance with only a
clay cap (prior to the OU2 cap). In general, the groundwater-protection SALs are lower
(more stringent) than the direct-contact SALs. For carbon tetrachloride, the groundwater-
protection SALs are 1,121 micrograms per kilogram (jig/kg) for the waste zone and 1,054
Hg/kg for soil.
3.3 PERFORMANCE MONITORING PROGRAMS
The OU1 ROD specifies that groundwater monitoring be conducted to evaluate remedy
performance and verify that groundwater remediation goals (MCLs or other specified standards)
are attained downgradient of the extraction wells near the source areas.
GETS operation was ceased in 2003 for a variety of reasons related to system design,
effectiveness, and operation. Groundwater remediation goals have not been attained.
There is no defined groundwater monitoring program currently in place for the Site, though
monitoring activities do take place from time to time. The last comprehensive round of
groundwater monitoring was conducted in July 2012.
The 1995 OU2 ROD specified periodic inspection and maintenance of the composite caps. Cap
maintenance activities have been performed by Environ.
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4.0 CONCEPTUAL SITE MODEL
This section discusses the Optimization Team's interpretation of existing characterization and
remedy operation data and Site visit observations to explain how historic events and Site
characteristics have led to current conditions. This CSM may differ from that described in other
Site documents. CSM elements discussed are based on data discussed in the preceding sections
of this report. This section is intended to include interpretation of the CSM only. It is not
intended to provide findings related to remedy performance or recommendations for
improvement. The findings and recommendations are provided in Sections 5.0 and 6.0,
respectively.
4.1 CSM OVERVIEW
The CSM consists of contaminant source areas at the disposal areas, a groundwater plume
emanating from the disposal areas and migrating to the north and northwest in the unconfmed
aquifer, discharge to lateral and downgradient surface waters, and volatilization of VOC
contaminants to ambient and indoor air. The CSM is succinctly depicted in Figure B-4 of the
2011 Five-Year Review report (included in Attachment A; prepared by Environ).
4.2 CSM DETAILS AND EXPLANATION
4.2.1 SOURCE AREAS
The source areas refer to the five known landfill areas: NDA, MDA, SEDA, SWDA, and
SWSWDA. These areas cover a total area of approximately 24 acres within a contiguous land
parcel covering approximately 237 acres. Significant quantities of buried waste remain in these
disposal areas. The contamination in the buried waste is an ongoing primary source of
contamination to groundwater, surface water, and air.
In addition, highly contaminated vadose-zone soil, around and below the buried waste, at the
disposal areas represents a significant secondary contaminant source. That is, even if all of the
buried waste were removed, the remaining highly contaminated soil would continue to act as a
source of contamination to groundwater, surface water and air.
NAPL in the vadose and saturated zones also acts as a continuing source of contaminants to
groundwater and air. Some of the NAPL may be mobile, while much is likely in a residual,
immobile form. Contaminants can slowly dissolve from NAPL into groundwater and partition
into vadose-zone air vapor.
4.2.2 CONTAMINANT MIGRATION PATHWAYS
Groundwater at the Site is contaminated with carbon tetrachloride and other VOCs. Carbon
tetrachloride has been detected at concentrations up to 64,000 |ig/L and has an MCL of 5 |ig/L.
While other VOCs, SVOCs, and pesticides have been detected at the Site, carbon tetrachloride is
clearly the groundwater contaminant of greatest concern.
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A groundwater plume exceeding the carbon tetrachloride MCL of 5 |ig/L covers 1,700 acres
extending north and northwest of the source areas. The plume extends from the source areas to
areas of groundwater discharge to surface water along Pugh Creek, Clover Creek, other
tributaries, and wetlands. Contamination primarily exists in the upper unconfined portion of the
saturated groundwater zone (approximately 50 ft thick).
Groundwater discharge to surface water results in elevated levels of contaminants (especially
carbon tetrachloride) in streams. However, the processes of volatilization, dilution, and
biodegradation result in reduced concentrations within short distances from the discharge areas
and concentrations of Site contaminants are not detected above relevant criteria downstream
(west) of the plume in Clover Creek surface water.
4.2.3 CONTAMINANT FATE
Volatilization of carbon tetrachloride and other VOCs to the atmosphere represents the most
important natural contaminant sink for the Site. This volatilization occurs directly from the waste
areas and underlying vadose-zone soils (escaping along the edges of the landfill caps), from the
groundwater (especially in low-lying plume areas where the vadose zone is thin), and from the
wetlands and streams. There is also some biodegradation that occurs for carbon tetrachloride
(with chloroform, methylene chloride, and other degradation products potentially formed) near
discharge locations, but it appears that volatilization is a much more significant contaminant
sink.
In the present system, the volatilization that occurs, largely at groundwater seeps and in the
streams, can be thought of conceptually as a natural air stripper.
Once in the atmosphere, VOCs become widely dispersed and concentrations decrease rapidly to
background levels away from the areas of volatilization. Carbon tetrachloride is fairly stable in
the troposphere but can escape to the stratosphere where it is broken down by photolysis.
The non-VOC contaminants at the Site are likely to remain sequestered by sorption within
wastes, soils, and sediments at the Site for a very long time. These contaminants, to different
degrees, may eventually biodegrade. Some volatilization of SVOCs will also occur.
4.2.4 POTENTIAL EXPOSURE ROUTES
Humans may be exposed to Site contaminants through direct contact with waste or contaminated
soil, through consumption of contaminated groundwater, through contact with (or ingestion of)
contaminated surface water, through inhalation of ambient or indoor air within the plume area, or
through consumption of organisms (including fish) from Site-area habitats.
All of these exposure pathways have been evaluated through risk assessments and several of the
more critical pathways have been addressed through institutional and engineering controls (see
Sections 2.3 and 3.1).
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4.3 DATA COMPLETENESS
While the available data do not precisely quantify the mass of buried waste, the amount of NAPL
present, or the mass of contamination in the groundwater, the data are sufficient to generally
describe the conceptual site model, including the delineation of contamination.
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5.0 FINDINGS
The observations provided below are the technical interpretations of the Optimization Team.
They are not intended to imply a deficiency in the work of the site managers but are offered as
constructive information and opinions in the best interest of the EPA and the public.
5.1 CONTAMINANT MASS AND LOCATION
Based on the draft FFS, it is estimated that there are approximately 9 million pounds of VOCs
present at the Site.4 This total includes 8.8 million pounds for the North Disposal Area (NDA),
0.08 to 0.15 million pounds for the MDA, and lower masses from the smaller disposal areas.
By far, most of the contaminant mass is within the footprint of the largest landfill area, the NDA.
At each landfill area, the contamination is present within the buried waste which is
approximately 5 to 20 ft below ground surface (bgs). Some of the contamination likely remains
within intact or partially intact drums in the waste zone. (Contamination within drums has been
encountered during past drilling activities.) The vadose-zone soil and saturated zone groundwater
beneath the waste zone also have substantial contamination.
A VOC plume in groundwater emanates from the landfill areas. The plume covers 1,700 acres
and extends from the source areas to downgradient surface discharge points at creeks and
wetlands.
During its 6-year operation, the GETS removed 796 million gallons of water and 110,000 pounds
of VOCs. Thus, on average, the extracted water contained approximately 17,000 jig/L VOCs.
Based on the FFS plume map, the portion of the plume between 2,000 |ig/L and 40,000 |ig/L (or
higher) is approximately 950 acres. If it is assumed that the average concentration in this part of
the plume is 17,000 jig/L (the average concentration removed by the GETS), that the plume
thickness is 50 ft, and that the porosity is 30 percent, the amount of VOC mass in the saturated
zone is approximately 660,000 pounds. This does not include the mass present as NAPL in the
saturated zone.
NAPL is present at the Site in the vadose-zone and saturated zone. This finding is based on the
following facts:
NAPL waste has been encountered during investigation.
Measured groundwater concentrations for carbon tetrachloride routinely exceed 1 percent
of solubility (8,000 |ig/L) in many monitoring wells (some far from the source);
4 The mass estimates presented in this paragraph come from a draft Focused Feasibility Study for OU2 (Environ,
January 2012) reviewed by the Optimization Team and supported by independent calculations of reasonableness.
Environ has since reduced their mass estimate to 6.8 million pounds; the basis for this reduction has not been
reviewed by the Optimization Team.
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Deep vadose-zone soil gas concentrations are significantly elevated relative to
background and ambient concentrations (particularly at the NDA);
The method of burial (drums of liquid waste from a chemical plant were dumped in
trenches) would easily lead to widespread NAPL presence; and
Carbon tetrachloride is denser than water (DNAPL) and thus tends to migrate down to
and below the water table.
It is difficult to estimate the mass of NAPL in the saturated zone. Based on experience at other
NAPL sites, the mass of VOCs present in the saturated zone as NAPL may be similar to or
greater than the mass present in dissolved form. Thus it is possible that over 1 million pounds of
VOCs are present in the saturated zone (dissolved plus NAPL mass). It is therefore estimated
that at least 7 percent (dissolved only) and perhaps well over 10 percent of the total mass buried
at the Site has already migrated to the saturated zone.
5.2 RISKS FROM DIFFERENT AREAS OF CONTAMINATION
5.2.1 SOURCE AREAS
Human health direct exposure risks are low at the source areas because covers and caps are
present over most of the buried waste and contaminated soil and because access to the area is
limited by fencing and institutional controls.
The SWSWDA does not yet have a multi-layer composite cap. The PRP's consultant (Environ)
also recently noted that geophysical studies have identified some additional buried waste outside
the previously-known waste footprint that has not been capped.
A primary issue with the source areas is that they act as a continuing long-term source for
groundwater contamination. The source areas also contribute directly to ambient-air
contamination, especially close to the source areas.
5.2.2 GROUNDWATER
Groundwater is contaminated above MCLs with carbon tetrachloride (primary risk driver) and
chloroform between the source areas and the downgradient creek and wetland system which acts
as a groundwater sink. Concentrations of carbon tetrachloride are three to four orders of
magnitude greater than the MCL throughout much of the plume (approximately 900 acres).
The groundwater plume is stable in size because the plume has already reached natural discharge
locations; groundwater beyond the bounding creeks (such as north of Clover Creek and east of
Pugh Creek) is not contaminated and is not expected to become contaminated.
There are approximately 35 homes currently within the plume boundary. These homes have been
provided with a clean public water supply and are not withdrawing groundwater for household
use. Institutional controls prohibiting use of groundwater (through property deed restrictions)
have been implemented for most, but not all, of the properties within the plume.
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5.2.3 SURFACE WATER
Groundwater discharges to streams and streamside wetlands with concentrations of carbon
tetrachloride above MCLs. Dilution, volatilization, and (probably) biodegradation reduce
concentrations measured in the streams.
The highest concentrations of carbon tetrachloride in surface water are found in Pugh Creek and
tributaries to Pugh Creek north of the source areas. In 2010-2011, a concentration of 26,000 |ig/L
was measured in a small tributary to Pugh Creek. A concentration of 6,100 |ig/L was measured
in 2004-2005 in Pugh Creek less than 1,000 ft northwest of the NDA. At that time,
concentrations persisted near and above 100 |ig/L from that point to the confluence with Clover
Creek. However, concentrations in Clover Creek downgradient of the groundwater plume
discharge locations were below MCLs and below water quality criteria for all surface-water use
designations. For carbon tetrachloride, Tennessee water quality criteria are 5 |ig/L for surface
water that may be used as a domestic water supply, 16 jig/L for recreational use (including
fishing) of surface water (organisms only criteria), and 2.3 |ig/L for surface waters designated for
both domestic and recreational use; other water use designations do not have specific criteria for
carbon tetrachloride.
Despite the fact that surface-water concentrations exceed MCLs and certain surface-water
criteria, potential risks for recreational users exposed to surface water and fish at the Site were
found to be acceptable in a 2011 risk assessment. The affected surface waters are not used as a
water-supply source.
At least one residential property within the plume area has a pond that is filled (in part) using
potentially contaminated water from Pugh Creek. Residential exposure to contaminated ponds
has not been fully evaluated as a potential exposure route.
5.2.4 AMBIENT AIR
The ambient (outdoor) air at the Site has elevated levels of carbon tetrachloride. A few
measurements of ambient air concentration in 2007-2008 exceeded the risk-based screening level
of 5.2 ppbv (which represents a 10"4 cancer risk using certain exposure and toxicity assumptions)
presented in the 2008 Annual Ambient Air Report. This ambient-air screening level was twice
the presented indoor-air screening level of 2.6 ppbv based on an assumption that ambient air
exposure is only applicable outdoors and that 12 hours per day are spent outdoors. The OU2 FFS
provides an updated risk-based criterion of 6.5 ppbv for ambient and indoor air based on a
revised toxicity assessment for carbon tetrachloride published by the EPA in the Integrated Risk
Information System in 2010.
Within the immediate vicinity of the disposal areas (that is, on the landfill property) elevated
ambient air concentrations are likely caused by vapors emanating from the buried waste, the
contaminated soil in the vadose zone below the buried waste, and (probably to a lesser extent)
vapors emanating from contaminated saturated-zone groundwater. Immediately adjacent to the
landfill property (for instance, along Old Toone Road due west of the disposal areas) it is likely
that ambient air concentrations are caused by volatilization from groundwater and by
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volatilization from the waste and vadose zone at the source areas. It is noted that soil-gas
samples near and west of the disposal areas show elevated concentrations in shallow soil gas and
often show increasing soil-gas concentrations with depth, suggesting volatilization from
groundwater is potentially important.
North of the landfill property, it is likely that elevated ambient air concentrations are caused
primarily by volatilization from contaminated groundwater and surface water. Concentrations are
generally higher in low-lying areas where the water table is relatively shallow and concentrations
do not appear to be significantly correlated to either distance from the source areas or to wind
direction. There is little evidence to suggest that vapors emanating from the source areas
contribute significantly to ambient air concentrations distant from the sources.
Exposure to elevated ambient air concentrations can be controlled at the landfill property and at
other PRP-owned land through access restrictions. It is difficult or impossible to control
exposure to ambient air at properties not owned or controlled by either the PRP or government.
5.2.5 INDOOR AIR
Concentrations of carbon tetrachloride were detected above risk-based action levels at two
homes within the groundwater plume. Subsequently, vapor mitigation systems were installed at
each of these homes using a crawlspace vapor barrier and active venting to the atmosphere.
These systems are effective at mitigating indoor air risk for these two homes.
A thorough set of indoor air monitoring data have been collected. At present, there are no other
homes that have indoor air issues at the Site. There remains a future risk of indoor air exposure at
homes within the plume, including homes that may be built in the future without vapor
mitigation systems.
5.3 EXISTING RISK-MITIGATION MEASURES
Several measures have been taken at the Site to reduce the potential for human exposure to Site
contaminants. These measures include:
A clay cap was installed over the disposal areas, on top of the existing waste cover, to
prevent direct exposure to the waste and to limit infiltration through the waste and
underlying contaminated soil; a multi-layer RCRA cap was subsequently installed on top
of the clay cap to further isolate the waste and limit infiltration.
Fences have been installed around the disposal areas to limit human access to the source
areas.
A public water supply was extended to the Site area to provide a clean water source for
residents within the groundwater plume.
Institutional controls to prevent groundwater use have been obtained for 56 of 60 parcels
within the plume, covering approximately 86 percent of the plume area.
Indoor vapor mitigation systems have been installed to control indoor air concentrations
at two homes.
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Each of these actions has had a positive effect in reducing the potential human exposure to Site
contaminants, particularly carbon tetrachloride. The low-permeability landfill caps also reduce
the amount of contaminant leaching to groundwater.
5.4 POTENTIAL ADDITIONAL MEASURES TO ADDRESS LANDFILL SOURCES
(OU2)
5.4.1 OU2 FEASIBILITY STUDY
The January 2012 draft OU2 FFS provides a summary of several feasible remedial technologies
that is helpful for assessing the relative merits of different potential remedial approaches. The
draft FFS also provides a feasibility-level evaluation of remedial alternatives relative to the NCP
criteria. The technologies and alternatives presented in the FFS cover an appropriate range of
potential remediation approaches for this operable unit. The Optimization Team reviewed the
draft FFS in developing technical comments on SVE as a full-scale remedy for OU2 relative to
other potential remedial alternatives.
With the exception of cost, the evaluations are presented in qualitative terms in the draft FFS:
comparisons of alternatives relative to each NCP criteria are presented in narrative form and
summarized in a table (the alternatives are scored as good, moderate, or poor at meeting NCP
criteria). Table 5-1 on the following page is a summary of the feasible remedial alternatives
taken directly from the draft FFS,5 with a few cells highlighted by the Optimization Team.
With the exception of the no-action alternative (SA-1), all of the alternatives include construction
of a cap over the SWSWDA, maintenance of the landfill caps, and controls to prevent access to
the disposal areas (fences and property ownership with institutional controls). SA-4 includes
these actions plus operation of SVE to remove a substantial portion of the VOCs present in the
waste and vadose zones at all disposal areas. SA-5 includes excavation of the waste layer with
SVE for the underlying vadose zone; the excavated waste would be consolidated in a new on-site
engineered disposal cell with appropriate bottom liner and cap for more effective isolation.
' This table has been updated by Environ subsequently, after Environ review of a draft of this report.
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Table 5-1. Remedial Alternatives Summary from the Draft FFS
Alternative
Description
Overall Protection of
Human Health and the
Environment
Compliance with ARARs
Long-Term Effectiveness
and Permanence
Reduction of Toxicity,
Mobility, and Volume
through Treatment
Short-Term Effectiveness
Implementability
Total Present Value Cost of
Alternative
SA-1
No Action
Moderate
Poor
Poor
Poor
Poor
Good
$0.2 M
SA-2
Access
Restriction & Cap
Maintenance
Good
Poor
Good
Poor
Moderate
Moderate
$1.5 M
SA-4
SA-2 +
SVE
Good
Poor
Good
Moderate
Moderate
Moderate
$54.5 M
SA-5
SA-4 +
Excavation & On-
Site Disposal
Good
Poor
Good
Moderate
Moderate
Poor
$305.5 M
The draft FFS does not present a preferred alternative, but discussions with the Site team have
indicated that SA-4 (SVE with access restriction and cap maintenance) is the preferred
alternative for a new OU2 Proposed Plan and ROD.6
SVE has already been implemented in the SWDA as a pilot test and another SVE pilot test has
begun at the SEDA and SWSWDA.
5.4.2
COMPARING EFFECTIVENESS FOR ALTERNATIVES SA-4 AND SA-5
Environmental professionals are likely to differ in opinions regarding how the different
alternatives compare to one another in relation to the NCP criteria, and the qualitative ratings in
the draft FFS table above do not fully elucidate the differences between alternatives, although the
FFS provides a discussion of many of the differences between the alternatives in the text. In
particular, it may be useful to describe more fully the relative merits of alternatives SA-4 (SVE)
and SA-5 (Excavation & SVE) in a few of the categories where the two alternatives have
identical ratings, as highlighted in orange in the table above.
6 Since completion of the optimization review and the initial draft of this report, a ROD amendment has been
completed for OU2 specifying SVE in all disposal areas.
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As indicated in the FFS evaluation, the excavation action would, in the long term, result in a
more certain and permanent isolation of much of the contamination present at the Site. While the
excavation would more permanently immobilize much of the mass, there would actually be less
mass treated (by SVE) under alternative SA-5.
5.4.3 ARAR COMPLIANCE AND WAIVERS
The second criterion in the table, Compliance with ARARs, is also a threshold criterion under
the NCP and CERCLA. Any ARAR that cannot be met by a selected remedial alternative is
required to be documented in an appropriate waiver. The evaluation of "poor" for all alternatives
in this category (blue highlighted cells in above table) requires additional explanation and a
description of the type of waiver(s) that would be sought for the particular ARAR(s) not met.
While it is clear that neither SA-1 nor SA-2 will result in meeting the OU2 Soil Action Levels
(SALs), the FFS text should provide further discussion, especially for SA-4 and SA-5.
It would be appropriate to state that none of the alternatives will result in meeting SALs for
pesticides or SVOCs. While SA-4 and (more so) SA-5 will result in significant long-term
reductions in VOC concentrations, it is also unlikely (in the opinion of the Optimization Team
based on experience at and reviews of other sites) that SALs will be achieved permanently
throughout the entirety of OU2. If the Site team believes that SALs will be met, soil
concentrations should be included as a measure of SVE performance.
Since the OU2 remedial alternatives would not address existing groundwater contamination, it
would also be appropriate to note that groundwater, surface-water, ambient air, and indoor air
ARARs and cleanup levels will not be met by any of the alternatives, but that these ARARs and
levels will be addressed during selection of a remedy for OU1.
5.4.4 SVE PILOT TEST
The SVE pilot test conducted from eight SVE well nests and at one additional SVE well at the
SWDA over a period of 28 months (approximately 10,000 operation hours) achieved significant
contaminant mass removal. The SVE pilot test removed approximately 31,000 pounds of VOCs
from the area and provided Site-specific data for design at the other disposal areas. Based on the
most recent information the Site team provided, the effective lateral radius of influence was
greater than expected (much greater than 100 ft).
5.4.5 ASSESSMENT OF SVE BENEFITS AND SHORTCOMINGS
The main benefit of SVE is to reduce the mass of VOCs in the waste and underlying vadose
zone. Based on preliminary information from the pilot test, the PRP's consultant estimates that
approximately 85 percent of VOC mass at the source areas can be removed from the waste and
vadose zone with SVE. While the amount of mass removal will be substantial, this removal
percentage is higher than measured at other somewhat similar SVE sites, and thus the
Optimization Team believes that this estimate of mass removal is optimistic. A more realistic
estimate is 75 percent or less.
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A significant mass of VOCs as well as non-volatile contaminants will be left in place. The
remaining VOCs will continue to be a source of groundwater contamination through: (1) vapor
migration which is limited laterally by topography and vertically by the thick vadose zone, and
(2) liquid migration and leaching which is limited by the landfill caps.
Due to the fact that a diminished source will remain and considering that there is already
substantial mass in the saturated zone (some as DNAPL), it is unlikely that SVE will result in
meaningful reductions in groundwater concentrations or consequent potential risks for present
and future downgradient receptors, for a period of many decades at least.
5.4.6 SELECTION OF SVE AS OU2 FINAL REMEDY
The Optimization Team concurs with the Site team that SVE is the most cost-effective and
implementable means by which contaminant mass can be removed at this Site.
The Optimization Team also concurs with the Site team preference for SA-4 (SVE only) over
SA-5 (excavation and SVE) based on the five balancing criteria: long-term effectiveness and
permanence; short-term effectiveness; reduction in toxicity, mobility, or volume of contaminants
through treatment; implementability; and cost. The Optimization Team also concurs that SA-4
will result in significant reduction in mass of VOCs at the Site and therefore addresses the NCP
criteria for reducing contaminant toxicity, mobility, or volume through treatment whereas SA-2
does not.
The significant cost increase for SA-4 relative to SA-2 would result in a significant reduction in
VOC mass but would not be likely to reduce downgradient risks over a reasonable time frame.
The EPA, TDEC, PRP, and other stakeholders may consider whether the benefit of reduced
VOC mass with SVE is worth the substantial cost of implementation. Per the NCP, a remedy
shall be deemed cost-effective if its costs are proportional to its overall effectiveness. Cost
effectiveness is determined by evaluating three of the balancing criteria: (1) long-term
effectiveness and permanence, (2) reduction of toxicity, mobility, or volume through treatment,
and (3) short-term effectiveness to determine overall effectiveness and then overall effectiveness
is compared to cost to ensure that the remedy is cost-effective.
5.4.7 FS COST ESTIMATE FOR SA-4
The Optimization Team agrees with the relative total costs of alternatives and comparative
analysis of costs in the draft FFS (shaded in green in Table 5-1). However, our review suggests
that the cost estimate could be refined and that overall costs should be significantly lower for
SVE (SA-4). The overall reduction in cost (to perhaps $40M total net present value for SA-4)
would increase the favorability of SA-4 relative to other alternatives.
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The following specific comments are provided for the SA-4 cost estimate presented in the draft
FFS:7
1. No source, quote or discussion is provided for the $1.5 million thermal oxidization unit.
More detail should be provided including a vendor quote and backup information should
be provided for estimated natural gas and maintenance labor costs. The FFS should
provide some rationale for use of thermal oxidation for the vapors at the NDA rather than
VGAC with regeneration.
2. No source or quote is provided for the blower units, and there is some discrepancy
between Table 8-4 and Appendix D of the draft FFS. The $1.2 million capital cost and
$889,000/year (yr) power costs are higher than the Optimization Team would expect
based on experience. The power costs are equivalent to greater than 1,200 kilowatts
(KW) at $0.08/KW in continuous operation. Assuming 75 percent motor efficiency, this
translates to three 400 horsepower (FTP) motors. This seems large for the flow rate (the
vacuum was not specified but we assume it is about 60-in F^O). The Optimization Team
is working at another site with three Tuthill Competitor Plus Model 6015-21L2 rotary
blowers with 25 HP motors that provide 1,000 cubic feet per minute (cfm) at 55-in H^O
vacuum. These cost less than $30,000 each complete in 2007 and could be available for
much less now. A Roots 624 blower with a 100 HP motor could provide approximately
3,000 cfm and could be purchased for under $50,000 each.
3. The MDA plus NDA phase 1, 2 and 3 costs include about $790,000 for on-landfill gas-
probe monitoring points in addition to the 102 extraction wells per phase. The cost
estimate should provide a basis for the number of wells and probes, taking into account
the results of the SVE pilot test and the potential for extraction wells to serve also as
monitoring points. Fewer SVE wells and probes may be appropriate.
4. Other costs that should be checked for MDA and the 3 NDA phases combined:
a. $270,000 for security during drilling at a remote fenced site.
b. $300,000 for fencing around wells at a Site that already has a fence.
c. $265,000 for laboratory analysis of soil samples, but it appears that only soil gas
levels during operation will be relevant for demonstrating performance.
5. The construction management level of 32% is very high ($5 million total). We
understand that the percentage is based on experience during the pilot test but the level of
effort should decrease considerably for full-scale installation of the larger systems by
more efficient contractor scheduling and higher production.
7 Environ has subsequently modified some cost estimates and lowered the overall net-present-value cost estimate for
SA-4 from $55 million to $50 million. The FFS was finalized in June 2012, but the final FFS was not reviewed as
part of this optimization review.
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6. $513,000 of remedial design is included in Phase 2 and 3 of the NDA. It is not clear why
this would be needed after the blower and oxidizer will have been installed and well
details are the same as the previous phases.
7. The $98,000/month (page 2 of Table 8-4) cost for monitoring and reporting at the SDA,
MDA and NDA for the first 8 years of operation on top of two full-time operators at the
NDA is very high. It could be in the $50,000/month range.
8. Generally the capital and operation and maintenance (O&M) costs are much higher than
expected for the SVE system. The total O&M costs (without discount) should probably
be approximately $40 million.
9. The 7% discount factor used from the 2000 FS guidance should be presented, but it is too
high for current economic conditions. Thus, an additional net-present-value calculation
with a more reasonable discount factor should also be presented. The Optimization Team
has used 3% in recent work and 5% is the maximum that could be considered reasonable.
5.5 GROUNDWATER CONTAINMENT AND RESTORATION (OU1)
Though not the main focus of this optimization review, a few findings are presented below
relative to OU1.
5.5.1 IMPORTANCE OF THE GROUNDWATER PATHWAY
Most of the potential health and environmental risks at the Site are related to the groundwater
contamination. In addition to the potential future use of contaminated groundwater as a water
source, groundwater continues to supply contaminants to Pugh Creek, Clover Creek, other
tributaries, and wetlands. Also, a significant portion of the ambient and indoor air risks are
driven by volatilization from contaminated surface water and groundwater.
Even if the OU2 remedy is very effective at reducing VOC mass at the source areas, the
groundwater in OU1 will likely remain an issue for many years to come because:
DNAPL is very likely present in the saturated zone and will remain a long-term source
through dissolution; and
The OU2 remedy will not completely remove the source of contamination to the
saturated zone.
5.5.2 PRIOR PUMP AND TREAT REMEDY
The GETS operated for 6 years (1997-2003) and removed 110,000 pounds VOCs while treating
796 million gallons of water. The average withdrawal rate of less than 250 gpm was much less
than the design objective of 465 gpm.
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The extraction wells were screened in both the unconfmed aquifer and in the underlying and
relatively clean confined aquifer. This design was not optimal and it resulted in withdrawal of a
significant amount of clean water and may have contributed to the limited amount of
contamination observed in the confined aquifer near the extraction wells. Still, the average
concentration of VOCs in the influent was approximately 17,000 |ig/L.
The GETS treatment system consisted of in-well chlorination (to prevent biofouling), air
stripping, and GAC polishing. GETS effluent was discharged to Pugh Creek. Vapors were
treated in a regenerative VGAC. Operation and maintenance of the groundwater treatment
system was challenging and costly.
5.5.3 IMPROVED PUMP AND TREAT ALTERNATIVE
A pump and treat remedy for hydraulic containment is feasible. However, design changes should
be considered, if pump and treat is selected as a remedy. A revised design would set up a
hydraulic containment barrier line downgradient (north and northwest) of the source areas in the
unconfmed zone only. As indicated in a draft EPA groundwater analysis memorandum,
approximately 400 gpm would be needed to capture the plume. The aquifer can support this total
pumping rate from multiple wells.
The general treatment scheme used in the prior GETS would be appropriate, but most of the
existing equipment would likely be unusable due to age and inefficiency, or would not be
needed, and the system should be redesigned and rebuilt for the expected flow rates and
concentrations. A more detailed review of operation and maintenance records from the prior
GETS system could help define a more optimal treatment process design.
The Optimization Team understands that the GETS VGAC regeneration system was no longer
working and the system had solids filtering issues prior to its shutdown. These issues could be
addressed. A non-regenerative VGAC system may be considered or even treatment of the water
with GAC alone (no air stripper). These options would result in high GAC costs but system labor
and maintenance would be reduced. The solids filtration issue could be addressed by adding
parallel bag filter sets before and after the air stripper.
5.5.4 OTHER ALTERNATIVES FOR OU1
Other potentially viable alternatives likely exist for containing the groundwater plume nearer the
source areas or otherwise preventing human exposure to groundwater. Reasonable possibilities
are presented in the 2007 Site-wide FS. These alternatives include:
A funnel-and-gate system using vertical barriers and permeable reactive barriers (PRBs);
and
Acquisition of property within the plume.
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5.5.5 EXPECTED EFFECTIVENESS
Containment of the groundwater plume nearer the source, through pump and treat or another
remedy should be feasible. However, contamination will remain downgradient of the
containment boundary and it will take a long time for MCLs to be attained. The EPA estimates in
a draft modeling memo that the time to reach MCLs downgradient of the containment boundary
will be 100 years or more.
Based on prior experience, the Optimization Team would expect significantly reduced
concentrations downgradient of a well-designed and well-operated containment system within a
reasonable time frame. Based on estimated groundwater travel time of 200 ft/yr, some positive
effects (lower concentrations) of plume containment near the source areas could be realized
throughout the plume within 30 years. While it would likely take a very long time to reach MCLs
downgradient of the containment system, risks (from groundwater, surface-water, and air
exposure) would be substantially reduced much sooner.
5.6 SITE EXIT STRATEGY
The overall exit strategy for this Site is unclear. According to the RODs, the goal is to reduce
concentrations to MCLs and reduce soil concentrations to SALs (at least outside the caps). These
goals would take many decades (at least) to attain. With the GETS out of operation, there is no
current remedial action for groundwater and it does not appear that SVE systems contemplated
for OU2 will achieve all remedial goals without other actions. It is likely that any remedy will
take at least a few decades to achieve all remediation goals.
5.7 ENVIRONMENTAL FOOTPRINTS OF REMEDIAL MEASURES
Environmental footprints are typically evaluated for operating remedies (such as pump and treat
systems) in an effort to determine if operations can be adjusted in a manner that will reduce the
ongoing environmental footprint (such as through reduced energy use). At this Site, there are no
ongoing energy-intensive operations and no long-term operations are planned. The SVE systems
contemplated for OU2 will result in significant energy usage and there will be an environmental
footprint associated with this remedy. However, it would be premature to estimate the
environmental footprint prior to remedy selection and design.
5.8 HEALTH AND SAFETY
This Site presents substantial job safety hazards for the Site field teams that must be managed.
The presence of hazardous contaminants in buried waste presents both a direct exposure and
explosive-vapors threat. Level B personal protective equipment (PPE), which includes supplied-
air respirators, is used for subsurface-disturbance activities within the disposal areas, and soil
vapors must be monitored for potentially explosive conditions.
The use of Level B PPE limits the mobility and senses of the field personnel, presenting practical
hazards that must be taken into account when developing and implementing work tasks.
30
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6.0 RECOMMENDATIONS
Several recommendations are provided in this section related to remedy effectiveness, cost
control, technical improvement, and site exit strategy. The recommendations are listed in Table
6-1. Note that the recommendations are based on an independent technical review and represent
the opinions of the Optimization Team and in no way commit the EPA to accept or implement
such recommendations. These recommendations do not constitute requirements for future action,
but rather are provided for consideration by the Region. While the recommendations provide
some details to consider during implementation, the recommendations are not meant to replace
other, more comprehensive, planning documents such as work plans, sampling plans, and quality
assurance project plans.
Cost estimates provided herein have levels of certainty comparable to those done for CERCLA
feasibility studies (+50/-30 percent), and these cost estimates have been prepared in a manner
generally consistent with EPA 540-R-00-002, A Guide to Developing and Documenting Cost
Estimates During the Feasibility Study, July, 2000. The costs presented do not include potential
costs associated with community involvement activities that may be conducted prior to field
activities.
6.1 RECOMMENDATIONS TO IMPROVE EFFECTIVENESS
As noted in the 2011 Five-Year Review Report, the selected remedies for OU1 and OU2 did not
meet their stated remedial goals and are not protective of human health and the environment.
Therefore, for both OUs, a new remedial strategy is needed.
6.1.1 COMPLETE THE OU2 REMEDY DECISION WITH CLEAR RAOs
A new remedy for OU2 is needed. The EPA has progressed on this and is close to formally
proposing SVE as the new OU2 remedy, along with a cap over the SWSWDA and other
uncapped material, maintenance of all caps, and access restrictions.8 SVE has already been
implemented as a pilot study and interim measure for the SWDA.
It may be appropriate to implement the SWSWDA cap portion of the remedy as an interim
measure to avoid potential administrative delays. Also, it would be appropriate to cap any newly
discovered area of buried waste outside the existing cap footprints. (Based on communication
from Environ, there has been such a discovery since the Site visit by the Optimization Team.)
Implementing SVE at all disposal areas will result in a significant reduction in VOC mass but
(absent other actions) will not be likely to reduce downgradient risks for the next several
decades.
8 Since completion of the optimization review and the initial draft of this report, a ROD amendment has been
completed for OU2 specifying these remedial actions.
31
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An important part of the remedy decision for OU2 will be setting remedial action objectives
(RAOs) that are consistent with the overall Site remedy strategy, are achievable, and are
protective of human health and the environment. If the RAOs are set to achieve SALs similar to
those set in the original OU2 ROD, or if RAOs are set to attain MCLs in groundwater near the
sources, then it is unlikely that any OU2 remedy will meet these RAOs. The remedy at OU2
should also not be counted on to eliminate ambient-air risks outside the landfill property.
One goal of the remedy should be to eliminate any potential direct contact risk at the source
areas. This goal will be met by the OU2 remedy through capping, maintenance, and access
restriction. An additional goal would be to reduce the mass of VOCs at the source areas to the
extent practicable. Based on the analysis in the draft FFS, and the review of the Optimization
Team, SVE would be the cost-effective way to attain this goal, and would allow performance
objectives to be stated in terms of achieving attainable mass removal rates and stopping SVE
operation when mass removal rates are very low.
If SVE is implemented, the Site team should consider whether SVE shutoff should be based on
removing a certain number of pore volumes or rather on reaching a point of negligible mass
removal rate, as compared to that observed in the pilot test or observed during the initial period
of SVE operation.
6.1.2 EVALUATE GROUNDWATER REMEDIAL ALTERNATIVES AND IMPLEMENT AN OU1
REMEDY
The GETS that was constructed and operated per the OU1 ROD operated for six years and was
shut down in 2003. As explained in Section 5.5.2, that system had design flaws and operational
issues. There is presently no system to remediate groundwater or to reduce ongoing discharges of
groundwater contamination to surface waters and the ambient air.
The FS completed by Environ in 2007 included assembly and evaluation of several remedial
alternatives to address groundwater contamination. That FS is a good starting point for an
updated evaluation of potential remedies for OU1.
Data and modeling show that it may not be technically practicable to meet MCLs downgradient
of the landfill property for several decades. However, it should be possible to substantially
decrease the potential risks to current and future receptors through implementation of a well-
designed OU1 remedy.
In particular, the Optimization Team believes the EPA should give careful consideration to the
following general remedial actions (see Sections 5.5.3 and 5.5.4):
1. Limitation of access to properties within the plume area and to the adjoining streams.
(Note: This consideration is provided by the Optimization Team. In discussions during
the optimization process, the EPA and TDEC stated that they are not considering this as a
potential option.)
2. In-situ groundwater treatment and containment using a PRB in a funnel-and-gate system.
32
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3. Redesigned pump and treat system near the downgradient end of the landfill property
with approximately 400 gpm extraction for hydraulic capture and a redesigned treatment
system.
6.1.3 CONTINUE TO IMPROVE PROPERTY CONTROLS
Exposures can effectively be eliminated by controlling access to property and contaminated
media within the property. To that end, it is appropriate for the EPA and PRP to continue to seek
institutional controls for the remaining few properties in the plume that do not yet have such a
control. The PRP may also consider acquiring additional property.
6.1.4 CONTINUE TO MONITOR AMBIENT AIR AND INDOOR AIR
The ambient air data collected in 2008 suggest that residential air exposures are likely within the
acceptable 10"6 to 10"4 risk range, when concentrations are appropriately averaged over time and
over reasonable exposure areas. However, there were several instances where measurements of
ambient-air concentration exceeded the previous risk based action level set at a 10"4 risk level. As
noted in Section 6.3.1, action levels for ambient and indoor air should be clearly established.
Also, given high soil-gas concentrations in the plume area, and given some elevated indoor-air
concentrations, periodic monitoring of indoor air would be appropriate for existing and future
buildings in the plume area.
It would likely be prudent to install vapor barriers for any new buildings constructed in the
plume area.
Additional air quality data should be gathered, to supplement the data collected in 2008, in order
to better define the potential human health risks from ambient air and indoor air. See also Section
6.3.1.
6.2 RECOMMENDATIONS TO REDUCE COSTS
In a typical optimization review, ongoing annual costs incurred by the sponsoring organization
are reviewed, and recommendations are made on ways these costs can be reduced through
optimization. In this case, the sponsoring organization (the EPA) is not the Site operator;
furthermore, there are no systems currently in place requiring significant long-term operation and
maintenance effort or cost.
However, since the EPA Superfund program may end up with significant financial obligations at
this Site during and after implementation of new remedies for OU2 and OU1, the Optimization
Team does make two recommendations for controlling costs during future remedial actions.
33
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6.2.1 EVALUATE OU2 IMPLEMENTATION COSTS DURING REMEDIAL DESIGN
As noted in Section 5.4.7, the optimization review identified several items in the draft FFS cost
estimate for SA-4 (SVE with SWSWDA cap, cap maintenance, and access controls) that should
be checked carefully for potential opportunities to substantially reduce costs during
implementation of SVE.
While it may not be important for the FFS to be more accurate on costs (because improved
accuracy would not likely change the remedy decision), it will be important for the financially
responsible organization(s) to carefully consider these costs during the remedial design and
procurement process. Actual costs for this remedy should be considerably lower than listed in the
draft FFS.
6.2.2 SET PERFORMANCE GOALS FOR SVE
As discussed in Section 6.1.1, it will be important to set reasonable performance measures for
SVE (if implemented) so that the system can be shut down when it is no longer serving the
purpose of substantially reducing VOC mass. The Site team should consider whether SVE
shutoff should be based on removing a certain number of pore volumes or rather on reaching a
point of negligible mass removal rate, as compared to that observed in the pilot test or observed
during the initial period of SVE operation.
6.3 RECOMMENDATIONS FOR TECHNICAL IMPROVEMENT
A few recommendations are provided that could help in interpreting and managing data
associated with the Site and with assisting future evaluations.
6.3.1 DEFINE AND DOCUMENT ACTION LEVELS FOR AMBIENT AIR AND INDOOR AIR
In various documents, the risk-based criteria for ambient air and indoor air have been changed,
apparently based on different exposure assumptions and a recent (2010) update to the EPA's
toxicity information (see Section 5.2.4). The acceptable air concentrations, particularly for
carbon tetrachloride, should be formally set by the EPA. In setting these levels for ambient air, it
may be appropriate to consider the validity of an assumption that had previously been made
when developing such criteria: that time spent indoors but within the groundwater plume area
can be ignored (even where there is no vapor mitigation system installed). Such an assumption
can lead to a higher acceptable concentration for ambient air than for indoor air, which is
counterintuitive.
The carbon tetrachloride concentration of 6.5 ppbv (41 micrograms per cubic meter [|ig/m3] at
25ฐCelcius) identified as the appropriate risk-based criterion by Environ in the OU2 FFS is
estimated to result in a 10"4 excess cancer risk and therefore within the CERCLA risk range (10~6
to 10"4); this value is calculated based on toxicity information in IRIS, and an assumption of 30
years of exposure for 350 days/year and 24 hours/day.
' After reviewing a draft of this optimization review, Environ lowered the cost estimate for SA-4.
34
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6.3.2 DEFINE A GROUNDWATER MONITORING PROGRAM
A defined groundwater monitoring program should be documented and followed. The goal of the
monitoring would be to confirm that the plume remains stable. Annual sampling of a subset of
available monitoring wells would be appropriate. The monitoring program could be adapted in
the future as needed.
6.3.3 ESTABLISH AND USE A DATA MANAGEMENT SYSTEM
Data from the Site, including relevant data collected by PRP contractors, USGS, and TDEC
should be stored in an electronic data management system to improve data availability and
accessibility. This will improve the efficiency for any future technical evaluations at the Site.
The cost for setting up the data management system should be less than $10,000. Management of
the system will require some labor, but it is expected that additional labor costs will be entirely
offset by improved efficiency in reporting of analyses.
6.4 CONSIDERATIONS FOR ACHIEVING SITE CLOSE OUT
The effectiveness recommendations listed in Section 6.1 were selected because they are likely to
be helpful in initiating progress toward exiting the Site. Additional exit-strategy-related
recommendations are provided below.
6.4.1 DEVELOP A SITE EXIT STRATEGY
The overall Site exit strategy should involve either:
1. Mitigation of potential risks to existing and future receptors through reduction of
groundwater concentrations downgradient of source areas to the extent practicable; or
2. Elimination of long-term exposures (to residences) in the plume area and at discharge
waters with land-use controls.
In either case, the exit strategy will involve ongoing plume monitoring and management to
ensure that the plume does not expand, and ongoing source management (such as through cap
maintenance).
6.4.2 UPDATE THE OU1 AND OU2 RODs
New RODs should be developed for both OU1 and OU2. These RODs should be clear in RAOs
about how the implemented remedies will protect human health and the environment and should
indicate where and why certain ARARs (such as MCLs) can or cannot be achieved. If it is found
to be technically impracticable to achieve the MCL, it may be appropriate to seek an ARAR
waiver.
By documenting the Site strategy and clear RAOs in new RODs, it will be possible to execute
remedial actions at the Site and later demonstrate successful remediation.
35
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6.5 RECOMMENDATIONS RELATED TO GREEN REMEDIATION
No specific recommendations are provided for improved green and sustainable remediation at
this Site. However, the Site team should consider means for minimizing the footprint of remedies
considered for OU1 and OU2. During remedy implementation, preference should be given to
green remedial measures such as technologies and options that will result in lower energy use,
lower atmospheric emissions of contaminants, and lower waste volumes that would minimize the
footprint of the selected remedy.
6.6 SUGGESTED APPROACH TO IMPLEMENTING RECOMMENDATIONS
A preliminary decision on Site exit strategy (see Section 6.4.1) should be made in the near term
base on available information by weighing the costs, benefits, policy compliance, and
stakeholder perceptions associated with different conceptual approaches. At the time this review
was conducted the decision document for OU2 (source control) had not yet been finalized.10
Formalizing and implementing a groundwater monitoring program (see Section 6.3.2) should
also be completed in the near term.
Recommendations in Section 6.1.1, 6.2.2, and 6.4.2 should be considered when formalizing the
remedy decisions and establishing RAOs. During OU2 design, there will likely be opportunities
to reduce costs (see Section 6.2.1) and reduce the environmental footprint of the remedial action
(see Section 6.5).
A remedy decision for OU1 may require additional evaluation and perhaps additional studies
such as for effectiveness of PRB media) that could take 12 to 18 months to complete. The
recommendations in Sections 6.1.2 and 6.4.2 should be taken into account when developing
RAOs and formalizing the remedy decision.
An ongoing ambient and indoor air monitoring program (see Section 6.1.4) could be established
within a few months. This should be done in concert with defining an acceptable ambient air
concentration (see Section 6.3.1).
Establishment of a data management system (Section 6.3.3) should be implemented in the near
term and used as the central repository for past and future environmental data. This action will be
more time critical if and when the EPA Superfund program takes on greater responsibility for
remedy implementation.
Improvement of property controls (Section 6.1.3) should be on ongoing activity.
10 Since completion of the optimization review and the initial draft of this report, a ROD amendment has been
completed for OU2.
36
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Table 6-1. Recommendations Summary
Recommendation
6.1.1 Complete the OU2 Remedy Decision with Clear
RAOs
6.1.2 Evaluate Groundwater Remedial Alternatives and
Implement an OU1 Remedy
6.1.3 Continue to Improve Property Controls
6.1.4 Continue to Monitor Ambient Air and Indoor Air
6.2.1 Evaluate OU2 Implementation Costs during
Remedial Design
6.2.2 Set Performance Goals for SVE
6.3.1 Define and Document Action Levels for Ambient
Air and Indoor Air
6.3.2 Define a Groundwater Monitoring Program
6.3.3 Establish and Use a Data Management System
6.4.1 Develop a Site Exit Strategy
6.4.2 Update the OU1 and OU2 RODs
6.5 Consider Green Remediation Measures to Minimize
the Footprint of the Selected Remedy
Reason
Effectiveness**
Effectiveness
Effectiveness
Effectiveness
Cost Reduction
Technical
Improvement
Technical
Improvement
Technical
Improvement
Site Close Out
Site Close Out**
Green Remediation
Change in Cost*
Not Quantified
Not Quantified
Not Quantified
Not Quantified
Cost Reduction See Section 5.4.7
Not Quantified
Not Quantified
Not Quantified
Not Quantified
Not Quantified
Not Quantified
Not Quantified
* Due to the nature of this review, cost impacts were generally not quantified.
** An OU2 ROD has been issued since this report was drafted.
37
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ATTACHMENT A
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HARDEMAN COUNTY LANDFILL
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Drafter: APR/ELS
Date: 1/16/12 Contract Number: 21-11010B44
Approved: DTH Revised:
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SITE BOUNDARY
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Figure
B-3
Drafter: APR/ELS
Date: 02/22/11
Contract Number:
21-11010B40
Approved: DTH
Revised:
-------
VOCs OFF-GASSING FROM
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LANDFILL CAP FLANKS
VOCs OFF-GASSING FROM
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Drafter: APR/ELS
Date: 2/23/11
Contract Number:
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Approved: DTH
Revised:
-------
6NVIRON
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Drafter:
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Date: 4/17/12
Contract Number: 21-11010B44
Approved: DTH
Revised:
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21-11010B40
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Figure
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Drafter: ELS
Date: 2/24/11
Contract Number:
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Approved: DTH
Revised:
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Figure
B-19
Drafter:
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Date: 2/23/11
Contract Number: .21-11010640
Approved: DTH
Revised:
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237-ACRE LANDFILL PROPERTY
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Figure
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Drafter:
ELS
Date: 2/23/11
Contract Number:
21-11010B40
Approved: DTH
Revised:
-------
237-ACRE LANDFILL PROPERTY
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Figure
B-21
Drafter: ELS
Date: 2/23/11
Contract Number: 21-11010B40
Approved: DTH Revised:
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