United States Solid Waste and
Environmental Protection Emergency Response EPA530-R-97-007
Agency (5303W) May 1997
Best Management Practices
SEPA (BMPs) for Soils Treatment
Technologies
Suggested Operational
Guidelines to Prevent Cross-
Media Transfer of Contaminants
During Cleanup Activities
Reproduced on Paper that Contains at least 20% Post Consumer Fiber
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DISCLAIMER
This document was prepared by the U.S. Environmental Protection Agency (EPA) in order to
provide guidance in preventing cross-media transfer of contaminants during
implementation of soils treatment technologies. EPA does not make any warranty or
representation, express or implied with respect to the accuracy, completeness or
usefulness of the information contained in this report. EPA does not assume any liability
with respect to the use of, or for damages resulting from the use of, any information,
apparatus, method or process disclosed in this report. Reference to trade names or
specific commercial products, commodities, or services in this report does not represent
or constitute an endorsement, recommendation, or favoring by EPA of the specific
commercial product, commodity, or service. In addition, the policies set out in this
document are not final agency action, but are intended solely as guidance. They are not
intended, nor can they be relied upon, to create any rights enforceable by any party in
litigation with the United States. EPA officials may decide to follow the guidance
provided in this document, or to act at variance with the guidance, based on an analysis of
specific site circumstances. The Agency also reserves the right to change this guidance
at any time without public notice.
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PREFACE
This document has been prepared by the U.S. Environmental Protection Agency's
Office of Solid Waste. To minimize the cross-media transfer of contaminants during
Remedial Actions (RAs) or Corrective Measure Implementations (CMIs), this effort was
undertaken to develop the Best Management Practices (BMPs) for various soils treatment
technologies. This document was developed by a team effort led by EPA's Office of Solid
Waste. The names of team members, their affiliation, and area of assistance are listed
below:
Team Members
Ed Earth, P.E.
Ray Cody
Subijoy Dutta, P.E.
Michael Forlini
Scott Frederick
Larry Gonzalez
Bob Hall
Carolyn Hoskinson
Jose Labiosa
Shaun McGarvey
Bonnie Robinson
Larry Rosengrant
David Sweeny
Debby Tremblay
EPA/ORD/NRMRL-
Cincinnati
Other Physical/Chemical
EPA/Region 1
EPA/OSW/PSPD
EPA/TIO
EPA/OERR
Vapor Extraction
Team Leader
Bioremediation
Superfund Coordination
EPA/OSW/HWMMD Other Physical/Chemical
EPA/OSW/PSPD Management Coordination
EPA/OSW/PSPD HWIR-Media Coordination
EPA/OSW/HWMMD Soil Washing
EPA/OSW/HWMMD Thermal Treatment
EPA/OSW/PSPD Comments Coordination
EPA/OSW/EMRAD Universal Table
New Jersey, DEP Field Applicability
EPA/OUST Vapor Extraction
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A series of seven workshops on different technology groups was held by the team in
developing the document. A list of outside experts who attended these workshops and
provided input is furnished below:
Outside Workshop Experts
William Anderson, P.E.
Brett Campbell
David Carson
Harry Compton
Harsh Dev, PhD
Regina Dugan, PhD
David Ellis, PhD
Evan Fan
Uwe Frank
C.C. Lee
Mark Meckes
Rick Vickery
Kenneth R. Weiss
John Wilson, PhD
AAEE, Annapolis, MD Soil Washing/Thermal
Geosafe Corp., WA
EPA/ORD/NRMRL
EPA/OSWER/OERR-
Edison, NJ
IITRI, IL
Institute for Defense
Analyses, VA
Dupont Chemicals, DE
EPA/ORD/NRMRL
EPA/ORD/NRMRL
EPA/ORD/NRMRL
EPA/ORD/NRMRL
Dupont Exp. Stn.
Delaware DNR
EPA/ORD/NRMRL
Insitu Vitrification
Containment
OPC
RF Heating
Bioremediation
Bioremediation
Vapor Extraction
Vapor Extraction
Incineration
Thermal Treatment
Incineration
Incineration
Bioremediation
EPA plans to update this document in the future, when new technologies and more
effective management practices are developed.
Any questions, clarifications, or suggestions on this document should be
addressed to:
Subijoy Dutta, P.E.
U.S. EPA (5303W)
Office of Solid Waste
401M Street, SW
Washington, DC 20460
email: dutta.subijoy@epamail.epa.gov
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CONTENTS
Chapter Page
LIST OF TABLES iv
LIST OF FIGURES vi
LIST OF ACRONYMS vii
1.0 Chapter One: INTRODUCTION 1
1.1 Regulatory Background and Need for BMPs Guidance 1
1.2 Structure of BMPs Guidance 2
1.3 Examples of BMPs 4
2.0 Chapter Two: GENERAL BMPs for REMEDIATION ACTIVITIES 7
2.1 General Cross-Media Transfer Potentials for Various Treatment
Technologies 7
2.2 General Best Management Practices for Soils Treatment Technologies 9
2.2.1 Site Preparation and Staging 9
2.2.2 Pre-Treatment Activities 10
2.2.3 Treatment Activities 11
2.2.4 Post-Treatment Activities/Residuals Management 11
2.3 References 13
3.0 Chapter Three: CROSS-MEDIA TRANSFER CONTROL TECHNOLOQIES and MONITORING
3.1 Available Control Technologies 14
3.2 Relative Costs of Implementing BMPs 28
3.3 References 29
4.0 Chapter Four: BMPs for CONTAINMENT TECHNOLOGIES 31
4.1 Definition and Scope of Containment Technologies (for BMPs) 31
4.1.1 Key Features of Containment Technologies for the Purpose of BMPs 31
4.2 Containment Technology Description 33
4.3 Cross-Media Transfer Potential of Containment Technologies 34
4.4 Best Management Options to Avoid Potential Cross-Media
Transfers for Containment Technologies 34
4.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for Containment Technologies 36
4.6 References 36
5.0 Chapter Five: BMPs for SOIL WASHING 38
5.1 Definition and Scope of Soil Washing (for BMPs) 38
5.1.1 Key Features of Soil Washing Technology for the Purpose of BMPs 38
5.2 Soil Washing Technology Description 39
5.3 Cross-Media Transfer Potential of Soil Washing Technologies 40
5.4 Best Management Options to Avoid Potential Cross-Media
Transfers for Soil Washing Technologies 41
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5.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for Soil Washing Technologies 44
5.6 References 45
6.0 Chapter Six: BMPs for THERMAL TREATMENT 47
6.1 Definition and Scope of Thermal Treatment (for BMPs) 47
6.1.1 Key Features of Thermal Treatment for the Purpose of BMPs 47
6.2 Thermal Treatment Technology Description 49
6.3 Cross-Media Transfer Potential of Thermal Treatment Technologies 49
6.4 Best Management Options to Avoid Potential Cross-Media
Transfers for Thermal Treatment Technologies 50
6.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for Thermal Treatment Technologies 52
6.6 References 52
7.0 Chapter Seven: BMPs for VAPOR EXTRACTION 54
7.1 Definition and Scope of Vapor Extraction (for BMPs) 54
7.1.1 Key Features of Vapor Extraction Technology for the Purpose of BMPs .... 54
7.2 Vapor Extraction Technology Description 56
7.3 Cross-Media Transfer Potential of Vapor Extraction Technologies 56
7.4 Best Management Options to Avoid Potential Cross-Media
Transfers for Vapor Extraction Technologies 57
7.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for Vapor Extraction Technologies 59
7.6 References 60
8.0 Chapter Eight: BMPs for BIOREMEDIATION 62
8.1 Definition and Scope of Bioremediation (for BMPs) 62
8.1.1 Key Features of Bioremediation for the Purpose of BMPs 64
8.2 Bioremediation Technology Description 64
8.3 Cross-Media Transfer Potential of Bioremediation Technologies 66
8.4 Best Management Options to Avoid Potential Cross-Media
Transfers for Bioremediation Technologies 67
8.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for Bioremediation Technologies 68
8.6 References 69
9.0 Chapter Nine: BMPs for INCINERATION TREATMENT 72
9.1 Definition and Scope of Incineration Treatment (for BMPs) 72
9.1.1 Key Features of Incineration for the Purpose of BMPs 78
9.2 Incineration Technology Description 78
9.3 Cross-Media Transfer Potential of Incineration Technologies 78
9.4 Best Management Options to Avoid Potential Cross-Media
Transfers for Incineration Technologies 79
9.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for Incineration Technologies 80
9.6 References 81
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10.0 Chapter Ten: BMPs for OTHER PHYSICAL/CHEMICAL TREATMENTS 82
10.1 Definition and Scope of Other Physical and Chemical Treatment (for BMPs) 82
10.2 In Situ Radio Frequency (RF) Heating 83
10.2.1 Definition and Scope of In Situ RF Heating (for BMPs) 83
10.2.1.1 Key Features of In Situ RF
Heating for the Purpose of BMPs 84
10.2.2 In Situ RF Heating Technology Description 85
10.2.3 Cross-Media Transfer Potential of In Situ RF Heating 85
10.2.4 Best Management Options to Avoid Potential
Cross-Media Transfers During In Situ RF Heating 86
10.2.5 Waste Characteristics that May Increase the Likelihood
of Cross-Media Contamination for In Situ RF Heating 87
10.3 In Situ Vitrification 88
10.3.1 Definition and Scope of In Situ Vitrification (ISV) (for BMPs) 88
10.3.1.1 Key Features of In Situ Vitrification for the
Purpose of BMPs 89
10.3.2 In Situ Vitrification Technology Description 90
10.3.3 Cross-Media Transfer Potential of In Situ Vitrification 90
10.3.4 Best Management Options to Avoid Potential
Cross-Media Transfers During ISV 90
10.3.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for In Situ Vitrification
Technologies 91
10.4 In Situ Soil Flushing 92
10.4.1 Definition and Scope of In Situ Soil Flushing (for BMPs) 92
10.4.1.1 Key Features of In Situ Soil Flushing for
the Purpose of BMPs 93
10.4.2 In Situ Soil Flushing Technology Description 95
10.4.3 Cross-Media Transfer Potential of In Situ Soil Flushing 95
10.4.4 Best Management Options to Avoid Potential Cross-Media
Transfers During In Situ Soil Flushing 95
10.4.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for In Situ Flushing Technologies 96
10.5 Solidification/Stabilization 97
10.5.1 Definition and Scope of Solidification/Stabilization (for
BMPs) 97
10.5.1.1 Key Features of Solidification/Stabilization forthe
Purpose of BMPs 98
10.5.2 Solidification and Stabilization Technology Description 98
10.5.3 Cross-Media Transfer Potential of
Solidification/Stabilization 99
10.5.4 Best Management Options to Avoid Potential
Cross-Media Transfers During Solidification/Stabilization 99
10.5.5 Waste Characteristics That May Increase the Likelihood of
Cross-Media Contamination for Solidification and
Stabilization Technologies 100
10.6 Excavation and Off-Site Disposal 100
10.6.1 Definition and Scope of Excavation and Off-Site Disposal (for
in
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BMPs) 100
10.6.1.1 Key Features of Excavation and Off-Site
Disposal for the Purpose of BMPs 100
10.6.2 Excavation and Off-Site Disposal Technology Description 101
10.6.3 Cross-Media Transfer Potential of Excavation and Off-Site
Disposal 101
10.6.4 Best Management Options to Avoid Potential Cross-Media
Transfers During Excavation and Off-Site Disposal 101
10.6.5 Waste Characteristics that May Increase the Likelihood of
Cross-Media Contamination for Excavation and Off-Site
Disposal Technologies 102
10.7 References 102
11.0 Chapter Eleven: FIELD VALIDATION and CASE STUDIES of BMPs 106
11.1 Soil Washing/Soil Leaching to Treat Metals Contaminated
Soil at an Army Ammunition Plant in Minnesota (Site 1) 108
11.1.1 Description of Site Remediation Activities 108
11.1.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants 108
11.1.3 Views and Discussion Ill
11.2 In-Situ Chemical Based Stabilization of Petroleum Contaminated
Soil at a Refinery in Minnesota (Site 2) 112
11.2.1 Description of Site Remediation Activities 112
11.2.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants 112
11.2.3 Views and Discussion 114
11.3 Stabilization and Disposal of Lead Contaminated Soils at a Closed
Battery Manufacturing Facility in Virginia (Site 3) 114
11.3.1 Description of Site Remediation Activities 114
11.3.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants 115
11.3.3 Views and Discussion 117
11.4 Particle Size Separation and Soil Washing at a Site Used
Previously for Ammunition Testing and Disposal in Connecticut (Site 4) 117
11.4.1 Description of Site Remediation Activities 117
11.4.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants 118
11.4.3 Views and Discussion 119
11.5 Soil Vapor Extraction of Solvents at a Closed Electronic
Component Manufacturing Facility in Maine (Site 5) 120
11.5.1 Description of Site Remediation Activities 120
11.5.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants 120
11.5.3 Views and Discussion 121
11.6 Excavation and Thermal Treatment of VOC-Contaminated Soil and
Debris at a DOE Site in Colorado (Site 6) 121
11.6.1 Description of Site Remediation Activities 121
11.6.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants 122
11.6.3 Views and Discussion 124
11.7 On-Site Containment of Soils in Former Manufacturing Areas at a
Chromium Plant, Maryland (Site 7) 124
11.7.1 Description of Site Remediation Activities 124
11.7.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants 125
11.7.3 Views and Discussion 128
IV
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11.8 Ex Situ Bioremediation of Explosives Contaminated Soils at a
DoD Facility in Virginia (Site 8) 129
11.8.1 Description of Site Remediation Activities 129
11.8.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants 129
11.8.3 Views and Discussion 130
11.9 Comparison of Selected Case Study BMPs With BMPs
Recommended in this Guidance 131
LIST OF TABLES
Table 1-1. Technology-Specific Cross-Media Transfer Concerns and Possible BMPs 5
Table 2-1. Fractional Contributions of Various Remedial
Activities to Total Volatile Contaminant Emissions 8
Table 3-1. Emissions Sources and Controls During Cleanup Activities 16
Table 3-2. Technologies for Controlling Cross-Media Transfer of Contaminants During
Materials Handling Activities 18
Table 3-3. Technologies for Reducing Contaminant Concentrations in Air
Emissions Generated During Remediation 21
Table 3-4. Examples of Technologies for Controlling Cross-Media Transfer to Water 24
Table 3-5. Examples of Field Monitoring Technologies 26
Table 11-1. Key Characteristics of BMP Case Study Sites 107
Table 11-2. Examples of Field/Case Study Findings and Relevant
Modifications of the BMP Guidance Document 134
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LIST OF FIGURES
Figure 3-1. Relative Cost Effectiveness for Point Source VOC Controls 29
Figure 4-1. Cross-Sectional View Showing Implementation of Slurry Walls 32
Figure 4-2. Cross-Section of Multilayer Landfill Cover 32
Figure 5-1. Basic Soil Washing Flow Diagram 39
Figure 6-1. Schematic of a Thermal Desorption Treatment System 48
Figure 7-1. Schematic of a Soil Vapor Extraction System 55
Figure 8-1. Schematic for Solid Phase Bioremediation 63
Figure 8-2. Diagram of Solid Phase Biological Treatment Using a Composting Pile 66
Figure 9-1. Schematic Diagram of a Typical Incineration Facility 73
Figure 9-2. Typical Liquid Injection Incinerator 74
Figure 9-3. Typical Fixed/Sloped Hearth Incinerator 75
Figure 9-4. Typical Multiple Hearth Incinerator 76
Figure 9-5. Typical Rotary Kiln Incinerator 77
Figure 10-1. Schematic Diagram of an In Situ RF Heating System 83
Figure 10-2. Cross-Section of an In Situ RF Heating System 84
Figure 10-3. ISV Equipment System 88
Figure 10-4. A Cut-Away View of a Typical Treatment Cell 89
Figure 10-5. Schematic of In Situ Flushing Field Test System 93
Figure 10-6. Soil Flushing Sprinkler System 94
Figure 10-7. Schematic of Soil Flushing System 94
Figure 10-8. Generic Elements of Typical S/S Processes 97
VI
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LIST OF ACRONYMS
AEC Area of Environmental Concern
APCD Air Pollution Control District
ASME American Society of Mechanical Engineers
ASTM American Society of Testing and Materials
ATP Anaerobic Thermal Process
BACT Best Available Control Technology
BDAT Best Demonstrated Available Technology
BOD Biochemical Oxygen Demand
BMPs Best Management Practice(s)
BPT Best Practicable Technology
BPCT Best Practicable Control Technology
CAO Corrective Action Order
CAP Corrective Action Plan
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act of
1980
CFM Cubic Feet Per Minute
CFR Code of Federal Regulations
CMI Corrective Measure Implementation
CMIPP Corrective Measure Implementation (Program Plan)
COD Chemical Oxygen Demand
CAMU Corrective Action Management Unit
CSFS Contaminated Soil Feed Stockpiles
CWA Clean Water Act
DEP Department of Environmental Protection
DM Dust Monitor
DNAPLDense Non-Aqueous Phase Liquid
DNR Department of Natural Resources
DoD Department of Defense
DOE Department of Energy
EPA U.S. Environmental Protection Agency
FACA Federal Advisory Committee Act
FCC Federal Communications Commission
FFA Federal Facility Agreement
FID Flame lonization Detector
FR Federal Register
GAC Granular Activated Carbon
GC/MS Gas Chromatography/Mass Spectrometry
GCLs Geosynthetic Clay Liners
GPD Gallons Per Day
HWIR Hazardous Waste Identification Rule
HWMMEazardous Waste Minimization and Management Division of OSW/EPA
IRP Installation Restoration Program
ISM Industrial, Scientific, and Medical
ISV In Situ Vitrification
LNAPL Light Non-Aqueous Phase Liquid
LDR Land Disposal Restrictions
MPCA Minnesota Pollution Control Agency
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NIOSH National Institute of Occupational Safety and Health
NPDES National Pollutant Discharge Elimination System (CWA)
NRMRINational Risk Management Research Laboratory
OD Outside Diameter
OERR Office of Emergency and Remedial Response
OPC Other Physical/Chemical Treatment
ORD Office of Research and Development
OSW Office of Solid Waste
OSWEROffice of Solid Waste and Emergency Response
OUST Office of Underground Storage Tanks
OVA Organic Vapor Analyzer
OW Office of Water
PASP Perimeter Air Sampling Program
PCE Perchloroethylene
PIC Products of Incomplete Combustion
PID Photoionization Detector
PM Particulate Matter
POHC Principal Organic Hazardous Constituent
PPB Parts Per Billion
PPM Parts Per Million (mg/1)
PSPD Permits and State Programs Division of OSW/EPA
PVC Polyvinyl Chloride
RA Remedial Action
RD Remedial Design
RCRA Resource Conservation and Recovery Act
RF Radio Frequency
RFI RCRA Facility Investigation
RI Remedial Investigation
RI/FS Remedial Investigation/Feasibility Study
RSKERRL Robert S. Kerr Environmental Research Laboratory
SARA Superfund Amendments and Reauthorization Act of 1986
SDWA Safe Drinking Water Act
SHSP Site Health and Safety Plan
SITE Superfund Innovative Technology Evaluation
SPCC Spill Prevention, Containment, and Countermeasure (CWA)
SPLP Synthetic Precipitation Leaching Procedure (EPA Method 1312)
S/S Solidification/Stabilization
SU Standard Unit
SVE Soil Vapor Extraction
SVOC Semi-Volatile Organic Compound
SWDA Solid Waste Disposal Act
TCE Trichloroethylene
TCLP Toxicity Characteristic Leaching Procedure (EPA Method 1311)
TDU Thermal Desorption Unit
TIO Technology Innovation Office
TPH Total Petroleum Hydrocarbons
TRPH Total Recoverable Petroleum Hydrocarbons
TSDF Treatment, Storage and Disposal Facility
TSS Total Suspended Solids
Vlll
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TWA Time Weighted Average
USEPAU.S. Environmental Protection Agency
UST Underground Storage Tank
UXO Unexploded Ordnance
VOC Volatile Organic Compound
WIPP Waste Isolation Pilot Plant
WMD Waste Management Division of OSW/EPA
XRF X-Ray Fluorescence
IX
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1.0 Chapter One: INTRODUCTION
This document provides guidance on how to design and conduct soil remediation
activities at RCRA and other hazardous waste sites so that transfers of contaminants from
contaminated soil to other media (i.e., clean soil, air, and surface or ground water) are
minimized. Its primary purpose is to provide guidance on preventing cross-media
transfers of contaminants during implementation of soils treatment technologies for
treating contaminated soils or solid media in compliance with applicable state and/or
federal regulations. Releases that may result in transfer of contaminants from the soil
or solid media to water, air or other natural media are generally referred to as cross-
media transfer.
This document is not meant to direct or guide selection of appropriate treatment
technologies. Rather, it is only meant to provide advice on the operational practices
relating to prevention and control of cross-media contamination (hereafter referred to
as "Best Management Practices" or "BMPs") that, based on research and past experience,
may be best for the selected technology.
As described below, efforts to develop this document were initiated to support
implementation of the proposed Hazardous Waste Identification Rule for contaminated
media (HWIR-media). However, EPA believes that the guidance contained herein will be
useful in many different situations involving cleanup activities, where parties
implementing a soil treatment technology want to be attentive to cross-media
contamination concerns and minimize any adverse impact on the overall environment. This
document does not replace any existing state or federal regulations or guidance.
This document is also expected to assist in reducing worker exposure to
contaminants by identifying the potentials for cross-media transfer and recommending
possible control mechanisms during implementation of soils treatment technologies.
Although it is beyond the scope of this document to address the worker health and safety
issues, the recommended BMPs are expected to passively alleviate many of the worker
health and safety concerns during soils treatment technology implementation.
The cost of implementing the recommended BMPs are generally subsumed in the
overall treatment technology implementation. No specific incremental cost estimates are
available at this time for application of the recommended BMPs. However, based upon the
information gathered from a few case studies, a short synopsis on the relative cost of
implementing BMPs is provided in Section 3.2 of this document.
1.1 Regulatory Background and Need for BMPs Guidance
The Best Management Practices (BMPs) for Soils Treatment Technologies were
developed to provide guidance on how to identify and minimize the potential for causing
cross-media contamination during implementation of cleanup technologies for
contaminated soils or solid media. The guidance outlines the specific potential cross-
media concerns for specific activities and recommends approaches for preventing cross-
media transfer of contaminants.
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EPA originally began to develop the BMPs guidance in response to concerns that some
cleanup activities may unintentionally cause additional contamination through cross-
media transfer of contaminants. Stakeholders involved in the development of HWIR-media
raised these concerns to EPA.
The BMPs guidance was not developed for and should not be used as a compliance guide
for any particular set of cleanup standards, but instead should be used as a reference
during implementation of those standards. The Agency expects that it will be of use in
many contexts, including Superfund cleanups, RCRA Subtitle C corrective action, UST
corrective action, and state cleanups. If any of the recommendations provided in this
guidance causes a conflict with a state or federal regulation, such conflict is
unintentional, and the applicable regulation should be followed.
BMPs are not meant to be used as a selection tool for remedial treatment
technologies, rather they should be used during the implementation stage of remedies once
they are selected. EPA believes that this document will be of unique assistance where
parties implementing a soil treatment technology want to be attentive to cross-media
contamination concerns.
1.2 Structure of BMPs Guidance
The structure of this guidance document is the result of several rounds of analysis
and review of the task at hand and the information developed to accomplish it.
Developing and compiling BMPs for each existing soil treatment technology would be
a monumental undertaking. To simplify the effort, the BMP team grouped technologies
based on common features and similarities in their ability to give rise to cross-media
transfers of contaminants. This resulted in the following seven technology categories:
• Containment Technologies
• Soil Washing
• Thermal Treatment
• Vapor Extraction
• Bioremediation
• Incineration
• Other Physical/Chemical Treatments
It was recognized by the peer reviewers and BMP team members that implementation of
many technologies involved common activities. To streamline the document and make it
easier to use, BMPs for common activities were compiled into a single chapter. Similarly,
information on technologies used for controlling cross-media transfers of contaminants
were also compiled in one chapter for quick reference and to minimize repetition.
Individual chapters on different technology categories are made much more technology
specific. Other characteristics of initial draft guidance, such as organizing BMPs by
remedial stage or phase (e.g., site preparation and staging), were also maintained but
improved upon wherever possible, in accordance with reviewers' comments.
The remainder of this BMPs guidance is structured into ten chapters as follows:
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Chapter 2 presents BMPs that are not specific to any particular soils treatment
technology. In most cases, these BMPs are applicable across a range of remedial
activities and several or most remediation technologies. As presented, these BMPs
address specific cross-media transfer concerns (e.g., fugitive dust emissions,
surface and ground water contamination by runoff), providing information on
operational activities that can reduce the likelihood of transfers during
remediation activities. The information in this chapter is organized relative to
various remedial stages: site preparation and staging, pre-treatment, and post-
treatment/residuals management. Technology-specific BMPs are provided later in
Chapters 4 through 10.
Chapter 3 provides information on control technologies that can be used in
conjunction with BMPs to reduce the likelihood of cross-media contamination
during soil remediation activities. The information in this chapter is organized
in a series of five tables.
Chapters 4 through 10, respectively, present technology-specific BMPs for each of
the seven technology categories and, in some cases, for specific technologies
within those categories. References to Chapters 2 and 3 are provided wherever
applicable. More specifically, each chapter provides the following information:
• Definition and Scope. For each technology category, the guidance provides
a definition of the technology and describes the purpose and applications
of the technologies in each category. A description of the key features
common to all the technologies within the category is also provided. When a
new technology is introduced that is not specifically addressed in this
guidance, it could be matched with an existing technology category with
which it shares similar key features, and the appropriate BMPs can be
applied.
• Cross-Media Transfer Potential. The types of potential releases (e.g.,
fugitive dust emissions, volatile organic compound (VOC) emissions,
leaching of contaminants to ground water) that are of concern for the
general technology category and, if they differ, for specific technologies
within the category are identified. Types of potential releases are tied to
the remedial stage during which they are most likely to occur.
• The Best Management Options to Avoid Potential Cross-Media Transfers. For
the four major stages of the remediation process, this guidance discusses
those management options or practices, also called BMPs, that are generally
considered best to minimize cross-media transfer of contamination. For
example, the BMPs provided here address techniques that can be used to
suppress fugitive dusts, gas emissions, and odors; minimize surface and
ground water contamination; limit the effects of human and animal access
across sites; and other methods that can help to avoid potential cross-
media transfers during all activities associated with site remediation.
Most of the BMPs in many chapters address activities within the treatment
stage of remediation because those tend to be the most technology specific.
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Where appropriate, however, BMPs for technology-specific activities that
occur in other stages are also offered.
• Waste Characteristics that May Increase the Likelihood of Cross-Media
Contamination for this Technology. An overview is provided of site
conditions and waste characteristics that might result in a greater
likelihood of cross-media transfer of contaminants when a technology is
applied in less than optimal site conditions or to treat contaminants for
which its effectiveness may be limited.
• Residuals Management. Common post-treatment and residual management
issues have been addressed in Chapter 2 of this guidance, which identifies
the types of residuals that might be generated by the implementation of
technologies within particular categories and discusses the options
available for the management of residuals to prevent cross-media
contamination. This guidance only addresses those residuals that have some
potential for cross-media transfer of contaminants or their by-products
created during treatment.
Chapter 11 provides case studies as well as information on field validation
activities that EPA undertook at soil remediation sites in the Fall and Winter of
1996-1997. Useful information gleaned from these case studies and field
validation activities, such as the field applicability of BMPs and associated
control technologies, has been incorporated into this document as appropriate for
the seven technology categories.
In order to easily identify the recommended BMPs, the / bullet has been used
exclusively for the recommended BMPs in this document.
1.3 Examples of BMPs
Table 1-1 provides examples of the types of information that can be found in these
chapters. Specifically, this table presents technology-specific cross-media transfer
concerns for various technology categories and some of the possible BMPs for addressing
them. This table is not meant to be comprehensive. Many other concerns, and the BMPs that
should be used to address them, are outlined in the individual technology chapters, and
the reader is encouraged to review all of the information that is pertinent to a
particular technology grouping for best results.
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Table 1-1. Technology-Specific Cross-Media Transfer Concerns and Possible BMPs
Technologies
Area of Concern
Possible BMPs to Mitigate Concern
Containment
Technologies
Post-Implementation Maintenance: Cracks,
microfractures, other breaches of
containment unit resulting in leaching of
materials to groundwater or release of
fugitive emissions to air.
Containment structures should be periodically monitored for
cracks, microfracture, or leaks and proper control should be
exercised, when necessary, to prevent migration of
contaminants. Details of other cross-media transfer
concerns and possible BMPs for Containment Technologies are
listed in Chapter 4 of this document.
Soil Washing
Technologies
Residuals Management: Soil washing
typically generates large volumes of
contaminated waste water or other liquids.
Not all of these liquids can be easily
treated on-site.
Soils should be cleaned of debris and materials that would
increase the requirements for the use of water or other
solvents. For example, fine silts and clays should be
screened out prior to treatment. In addition, the mixing of
soil batches that contain dissimilar contaminants should be
avoided. In this way, the liquids that are used to clean the
soils can contain fewer additives, which will make them
easier to treat for recycling or disposal. Details of other
cross-media transfer concerns and possible BMPs for Soil
Washing Technologies are listed in Chapter 5 of this
document.
Thermal
Treatment
Technologies
Process Emissions: Stack emissions from
organic collection, removal, or
destruction of vapors past the thermal
desorption, vaporization, or separation
treatment have the potential for air
release of contaminants that have not been
completely destroyed.
Air pollution devices should be properly designed, installed
and operated to handle all of the constituents that are
anticipated to be separated from the soil under the specific
design of the particular thermal technology selected.
Products of incomplete reaction (i.e., combustion, if
appropriate) should also be handled in the design and
operation of the air pollution control devices.
Additives to soil being thermally treated have the potential
for encouraging complete combustion reactions, thereby
reducing emissions. Details of other cross-media transfer
concerns and possible BMPs for Thermal Treatment
Technologies are listed in Chapter 6 of this document.
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Table 1-1. Technology-Specific Cross-Media Transfer Concerns and Possible BMPs (cont'd)
Technologies
Area of Concern
Possible BMPs to Mitigate Concern
Vapor Extraction
Technologies
Disposal Of Residuals: Contaminated
debris, soils, and liquid wastes resulted
from excavation and installation of wells
are new sources for potential cross-media
transfer of contaminants.
During construction of soil vapor extraction-based systems,
construction debris should be properly handled and treated
on-site or be disposed off-site. Details of other cross-
media transfer concerns and possible BMPs for Vapor
Extraction Technologies are listed in Chapter 7 of this
document.
Bioremediation
Technologies
Surface and Ground Water Contamination:
Additives used in bioremediation, such as
phosphorus and nitrogen, have the
potential to migrate into nearby water
bodies as runoff if not carefully
controlled. In addition, oxygen
suppliers, such as hydrogen peroxide, can
be flammable, and may require careful
handling.
The nutrient-rich run-off should be controlled by the use of
berms, moats, or other physical barriers around
bioremediation sites. Alternatively, ground-feeding
sprinkler systems operated at low volumes can minimize the
amount of, and area over which, nutrient-rich water is
sprayed, reducing the potential for cross-media
contamination. Details of other cross-media transfer
concerns and possible BMPs for Bioremediation Technologies
are listed in Chapter 8 of this document.
Incineration
Technologies
Process Emissions: Stack emissions from
organic collection/destruction of vapors
using thermal desorption, vaporization, or
separation treatment have the potential
for release as contaminant-laden gas
streams into the atmosphere.
Air pollution devices should be properly designed, installed
and operated to handle all of the anticipated constituents to
be released from the soil during the treatment process. Air
pollution control devices should be designed to treat the
products of incomplete combustion by ensuring that
sufficient oxygen is available during all combustion
activities.
Additives to the soil being incinerated have the potential
for reducing the formation of products of incomplete
reaction, thereby reducing emissions. Details of other
cross-media transfer concerns and possible BMPs for
Incineration Technologies are listed in Chapter 9 of this
document.
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2.0 Chapter Two: GENERAL BMPs for REMEDIATION ACTIVITIES
At many sites with contaminated soil or solid media, remediation activities will
be conducted that have the potential to generate cross-media contamination. These
activities generally fall within one of four major remedial stages, regardless of the
selected technology (although some technologies may not require or have the same level of
activity in all stages):
• Site Preparation and Staging
• Pre-Treatment
• Treatment
• Post-Treatment/Residuals Management
These stages are not always discrete and separate from one another. (For example,
residuals management is often an issue while treatment is on-going). However, for the
purposes of this document, they are treated individually.
This chapter presents best management practices (BMPs) for addressing those
remedial activities that are not unique to the technology selected for treating
contaminated soil or solid media at a site (but that still have the potential to generate
cross-media contamination). In other words, these BMPs are likely to have applicability
to a wide variety of sites because they are associated with a common remedial activity,
such as excavation, rather than a specific technology, such as soil washing. The BMPs are
organized according to the remedial stage to which they pertain (e.g., staging and site
preparation), and then to the applicable cross-media transfer concern (e.g., fugitive
dust). The types of remedial activities that may give rise to each concern (e.g.,
clearing and grubbing, excavation) are also presented to help in determining the
applicability of BMPs to a particular site.
As reflected in this chapter, BMPs most commonly associated with activities
performed as part of site preparation and staging, pretreatment, and post-
treatment/residuals management are not technology-specific. BMPs associated with
activities that occur in the treatment stage of a remediation are generally technology
specific, so they are not addressed here. BMPs for technology-specific activities and
cross-media transfer concerns are found in Chapters 4 through 10, which address
individual technology categories.
2.1 General Cross-Media Transfer Potentials for Various Treatment Technologies
During implementation of any soils treatment technology the following steps are
generally undertaken: a) Site preparation and staging, b) Pre-treatment activities, c)
Treatment activities, and d) Post-treatment activities. Specific cross-media concerns
during the actual treatment activities are addressed separately under the relevant
technology categories in Chapters 4 through 10. General cross-media transfer potential
for contaminants mostly during the site preparation, pre-treatment, and post-treatment
activities are identified below.
• There is risk of inaccurate site characterization with any soils treatment
technology operation. The material encountered at the remedial site may
-------
not be like the soils studied in treatability or pilot-scale tests.
Additional contaminants may be encountered, and the percentage of the fine-
grained fraction may be significantly different from that expected. These
factors may lead to a long-term storage or generation of high residual
volume, and thus increase the potential for cross-media transfer.
• During several different activities associated with remedy
implementations, including staging and site preparation (e.g., clearing,
grubbing); drilling, well installation and trenching operations;
mobilization and demobilization of equipment; excavation; transport of
materials across the site; and some treatment activities, there is high
potential for fugitive dust emissions due to movement of equipment at the
site. In addition, these same activities can enhance the volatilization of
VOCs, SVOCs, and other potentially hazardous materials into the
atmosphere.
• During pretreatment operations such as excavation, storage, sizing,
crushing, dewatering, neutralization, blending, and feeding, there is the
potential for dust and VOC emissions from the contaminated media.
• Migration of contaminants to uncontaminated areas may occur during
mobilization or demobilization.
• VOC and SVOC emissions tend to increase during periods of hot and dry
weather.
• Leaching of contaminants to surface water can occur from uncovered
stockpiles and excavated pits.
• Improper handling and disposal of residues (e.g., sediment/sludge
residuals or post-washing wastewater) may allow contaminants to migrate
into and pollute uncontaminated areas.
• Post-treatment discharges of wastewater, if improperly managed, can cause
migration of contaminants.
Table 2-1 provides a summary of the fractional contributions of various remedial
activities to the generation of volatile contaminant emissions, which is potentially a
major source of cross-media contamination during many remedial activities.
Table 2-1. Fractional Contributions of Various Remedial
Activities to Total Volatile Contaminant Emissions
(USEPA, 1991)
Fractional Contribution to Total Volatile
Remedial Activity Contaminant Emissions for the Entire Site
Remediation Process
-------
Excavation 0.0509
Bucket (Loading) 0.0218
Truck Filling 0.0905
Transport 0.3051
Dumping 0.5016
Incineration 0.0014
Exposed Soil 0.0287
Total 1.0000
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2.2 General Best Management Practices for Soils Treatment Technologies
Various control practices to prevent potential cross-media transfer of
contaminants during cleanup activities have been identified in Tables 3-1 to 3-5. Also,
proper system design is recommended prior to implementation of the remedial treatment to
avoid cross-media transfer problems during different treatment steps. However, general
BMP options to control specific cross-media transfer of contaminants for different
treatment technologies are furnished below:
2.2.1 Site Preparation and Staging
Prior to movement of equipment on site the following activities are most commonly
undertaken:
4 Site inspections; surveying; boundary staking; drilling and trenching;
sampling; demarcation of hot spots; and construction of access roads,
utility connections, and fencing.
Special attention and care should be taken during site preparation activities so
that the contaminated media are not disturbed. In case of unavoidable circumstances, the
contaminated media should be subjected to a very minimal disturbance/alteration during
these activities. The following BMPs are generally recommended:
/ Avoid entering the contaminated area. In unavoidable circumstances, build
a temporary decontamination area, which could be later used during cleanup
activities. Any above-ground and underground source of contaminants should
be identified and located prior to starting any treatment of contaminated
media.
/ Any soils and soil-gas sampling, field air permeability testing,
demarcation of hot spot etc. activities should generally be followed by
plugging/covering of any holes or depressions created during these
activities to prevent intrusion of water. It would also be appropriate to
install relevant signs at the same time so that repeated entry to the site is
not called for.
/ Contaminated drilling mud from any drilling operations should be collected
in a lined/contained system. This will prevent the contaminants from
mixing with the normal surface water runoff from the area and the
surrounding natural watercourse.
/ Contaminated waste generated during site preparation or further site
characterization activities should be managed protectively as specified in
Chapter 3, Tables 3-1 to 3-4.
/ Site investigation and operational plans should take into account the
presence of permeable zones and account for potential pre-existing
underground sewers and electrical conduits.
10
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/ Surface drainage and subsurface utility systems should be identified.
/ Local watershed management goals and priorities should be incorporated
into the surface water management plan for the cleanup activities.
2.2.2 Pre-Treatment Activities
Prior to beginning the actual treatment process the following activities are most
commonly undertaken:
4 Excavation, transportation, storage, sizing, crushing, dewatering,
neutralization, blending, installation of feeding systems for
contaminated media etc.
During the above activities, measures should be taken to control fugitive dust
emissions and to prevent releases of contaminated media to the natural environment. To
prevent cross-media transfer of contaminants, the following BMPs are generally
recommended for the above activities:
/ Any aboveground and underground sources of contaminants, such as storage
tanks, should generally be removed.
/ Any offsite runoff should be prevented from entering and mixing with on-
site contaminated media by building earthen berms or adopting similar other
measures, as outlined in Table 3-4.
/ Provisions should generally be made to capture on-site surface water runoff
by diverting it to a controlled depression-area or lined pit.
/ Sizing, crushing, and blending activities should be conducted under an
environment where the off gases, volatiles, dusts, etc. are all captured
inside a hood or cover, or controlled using other options listed in Chapter
3. The dust and VOC emissions associated with these activities that exceed
acceptable regulatory limits should be controlled by capturing these
emissions and then treating the captured vapor/air to the extent
practicable. Measures for preventing, collecting and treating dust and VOC
emissions are provided in Tables 3-1 and 3-3.
/ When mixing or dewatering, the contaminated aqueous stream should be
collected in a lined/contained system. This will prevent the contaminants
from mixing with the normal surface water runoff from the area and the
surrounding natural watercourse.
/ Protective management/disposal of contaminated debris is recommended to
prevent cross-media transfer. Protective management includes debris
washing, providing covers, testing, and appropriate disposal (see Section
11.6.2(d)and(i)).
11
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/ When treating explosive wastes, proper safety and care should be exercised
to prevent any explosion during the treatment process. For conducting safe
operations, recommendations provided in the Handbook (USEPA, 1993) may be
used, when necessary.
/ The technology design should be checked to ensure that the corrosion factor
has been taken into account in the design for all appropriate pipes, valves,
fittings, tanks, and feed systems.
/ Entry to the active site should be limited to avoid unnecessary exposure and
related transfer of contaminants.
/ The temporary decontamination area described in Section 2.2.1 should be
used as recommended earlier to keep the site-related contaminants within
the active cleanup area.
/ Fugitive dust emissions should be controlled during excavation by spraying
water to keep the ground moist. During wet weather or rainfall no water
spraying would be needed.
/ Consideration of climatological extremes/high wind, etc. should be taken
into account when conducting any of the treatment or associated activities.
Real-time weather data could be used to monitor weather conditions and
accordingly control treatment operations. During a recent field visit an
onsite weather station was observed. The weather monitoring stations were
reported to have nominal cost and were found to be highly useful in
controlling weather-related cross-media transfers. To determine possible
extreme conditions, local weather data for the past 10 years could be
reviewed from publications (NOAA, 1995) of the National Climatic Data
Center, 151 Patton Avenue, Asheville, NC 28801-5001, Phone: (704) 271-
4800.
/ During excavation, blending, and feeding of contaminated soils, VOC
emissions should be monitored and appropriate emission control measures
undertaken.
/ Operational plans should include adequate inspection procedures that look
specifically for corrosion and wear.
/ It is also critical to check that the air pollution control devices are
designed for the corrosive nature of the hot gases that are expected to
enter these devices, when used in certain soil treatment technologies.
/ As an effective erosion control practice, scheduling of construction
activities should be arranged to limit the time of exposure of disturbed
segments of the site. This entails directing work to one area of a site,
then completing and stabilizing that area before moving on to other areas of
the site.
12
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2.2.3 Treatment Activities
Treatment activities and relevant BMPs are specifically described for each
technology category in Chapters 4 through 10.
2.2.4 Post-Treatment Activities/Residuals Management
During the post-treatment process the following activities are most commonly
undertaken:
(a) Vapor (Gas) Phase
• Collection or destruction of organics
• Collection of particulates
• Removal of acid gases
13
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(b) Solid and Liquid Phases
• Treatment or disposal of aqueous wastes
• Disposal of dusts collected as a result of emission control during
materials handling, stabilization, or any other tertiary/post-
treatment
During the conduct of the above activities, measures should be taken to prevent
release of contaminated media to the natural environment. The following BMPs are
generally recommended for the above activities:
/ Remedial plans should be checked to ensure that they account for the
anticipated differences in characteristics of the treated soil. This may
involve recombination of the treated soil with uncontaminated soil from the
site (or off-site) in order to approximate the original soil
characteristics prior to contamination. The anticipated soil
characteristics of the treated soil should be verified prior to
replacement.
/ Treated wastes should be checked for leachability prior to disposal in a
landfill or other similar systems. Possibilities of long-term degradation
and migration of contaminants to groundwater should be carefully evaluated
and checked prior to disposal of stabilized/treated material.
/ Contaminated debris, soils, and liquid wastes resulting from excavation
and installation of wells should be properly handled, either treated on-
site or trucked away for off-site disposal. Berms should be built around
the active excavation, storage and treatment areas, if necessary, to
prevent migration of contaminated runoff away from the area.
/ If solid materials such as granulated carbon filters are used to collect
emissions, they should be removed carefully from the emissions system to
avoid rupturing them and dissipating the contaminated carbon materials.
They should be placed into tightly covered containers until they can be
recycled or properly disposed of.
/ Carbon beds used for VOC removal from the extracted vapor should be properly
managed and disposed of in compliance with Subtitle C regulations, and
should meet all applicable land disposal standards. If the carbon is
regenerated using steam or other means, the residual contaminated, liquids
should be managed as hazardous wastes, and treated or disposed of in
compliance with the applicable regulations.
/ Containers that hold residual liquids should be stored where they cannot be
disturbed or ruptured by large equipment. This may require construction of
a residuals management unit separate from the treatment and storage areas.
14
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/ All dusts or other particulates that are collected during emissions control
activities should be tested for contamination levels and handled and
disposed of properly.
/ Air stripping or other treatment of extracted (contaminated) water/liquids
should meet all applicable surface water discharge standards for post-
treated water.
/ When residual treatment wastes are obtained in the form of pure listed
waste/liquids (e.g., condensate from steam regeneration of carbon beds),
the recycling/reuse option for such residual waste should be considered.
2.3 References
1. National Oceanographic and Atmospheric Administration (NOAA). 1995. Comparative
Climatic Data for the United States through 1994, U.S. Department of Commerce,
Asheville, NC, October.
2. USEPA. 1993. Approaches for the Remediation of Federal Facility Sites
Contaminated with Explosive or Radioactive Wastes, EPA/625/R-93/013, Office of
Research and Development, Washington, DC, September.
3. USEPA. 1991. Engineering Bulletin, Control of Air Emissions from Materials
Handling During Remediation, EPA/540/2-91/023, Office of Research and
Development, October.
15
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3.0 Chapter Three: CROSS-MEDIA TRANSFER CONTROL TECHNOLOGIES and
MONITORING
This chapter provides descriptions of some of the technologies and practices that
are available to control or treat releases that might create cross-media contamination
during implementation of treatment technologies for soils and/or solid media. These
control technologies should generally be applied under the following conditions:
• When potential for cross-media transfer exists associated with the use of a
soil treatment technology as identified in Chapters 4 through 10 of this
document.
• When recommended in the general best management practices (BMPs) section
(Chapter 2) or technology-specific BMPs (Chapters 4 through 10).
• When a safe exposure level for workers is exceeded during cleanup
activities, as determined by the Occupational Safety and Health
Administration (OSHA), per 29 CFRpart 1910.
• Any other site-specific reasons that warrant their application, such as
proximity of a populated area or a drinking water source to the site.
3.1
tables:
Available Control Technologies
Information contained in this chapter is mostly provided in the following five
Table 3-1. Emissions Sources and Controls During Cleanup Activities. This
table lists potential emissions sources that may be encountered
during cleanup activities such as containers, tanks, and landfills.
It describes some common controls that can be used to reduce those
emissions, and outlines factors that may contribute to the
likelihood of emissions from those sources.
Table 3-2. Technologies for Controlling Cross-Media Transfer of Contaminants
During Materials Handling Activities. This table lists materials
handling activities that may be performed during site preparation
and staging, as well as pre- and post-treatment, that have the
potential to create cross-media contamination. It provides control
technologies that can be used during those activities, and lists
factors that may influence the effectiveness of those control
technologies. Some of the controls listed in this table may be
applicable to treatment activities which are discussed in the
individual remediation technology chapters.
Table 3-3. Technologies for Reducing Contaminant Concentrations in Air
Emissions Generated During Remediation. This table provides a list
of control technologies that can be used to reduce the
concentrations of air emissions. It describes each technology, and
16
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outlines factors that may influence the effectiveness of those
control technologies.
Table 3-4. Examples of Technologies for Controlling Cross-Media Transfer to
Water. This table provides a list of controls that should be
considered during all remedial activities to minimize the potential
for releases from soil to surface and/or ground water. The examples
provided are for relatively small-scale structures that can be
applied to short-term projects; for larger-scale and long-term
projects, consult the Metropolitan Washington Council of
Governments document cited in the references.
Table 3-5. Examples of Field Monitoring Technologies. This table provides a
list of technologies or practices that can be used to monitor
potential emissions during remediation activities. It describes
the technologies that can be used to monitor emissions from active
and inactive sites. These technologies can be applied prior to and
during remediation, as needed. A few simple and easy-to-use
monitoring techniques are also listed in this table.
17
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Table 3-1. Emissions Sources and Controls During Cleanup Activities (USEPA, 1992a)
Emission Source
Description of Control Technology
Factors Affecting Emissions
Surface Impoundments
Air-Supported Structures are made of light materials (often
plastics, vinyls, or coated fabrics) that form a roof-like
structure over the impoundment. Fans are used to maintain
positive pressure to inflate the structure. For effective
control, the air vented from the structure should be sent to
a control device such as a carbon adsorber. Air supported
structures have been used as enclosures for conveyors, open
top tanks, and storage piles, as well as impoundments.
Floating Membrane Covers are used to cover large
impoundments containing liquids. The membrane must provide
a seal at the edge of the impoundment, and provisions must be
made for the removal of rainwater that accumulates on the
covers. Additionally, vent systems for the removal of
accumulated gases and pumping systems for the removal of
accumulated sludge may be necessary.
Volatility of constituent
Residence time
Surface area
Turbulence
Windspeed
Temperature
Extent of competing mechanisms
(e.g., biodegradation)
Tanks
Fixed Roofs can be retrofitted to open tanks, or a fixed-roof
tank can be used to replace an open tank or impoundment.
Compared to an open tank, a fixed roof tank can provide
additional control of 86 to 99 percent.
Floating Roofs are common on tanks at petroleum refineries.
The roof floats on the liquid and moves with changes in the
liquid level, controlling working losses. Floating roofs
can be installed internally in a fixed-roof tank or
externally in a tank without a fixed roof. Emissions from a
properly maintained floating roof are very low.
Volatility of constituent(s)
Surface area
Turbulence
Windspeed
Temperature
-------
Table 3-1. Emissions Sources and Controls During Cleanup Activities (cont'd) (USEPA, 1992a)
Emission Source
Description of Control Technology
Factors Affecting Emissions
Dewatering
Devices
Dewatering devices, such as rotary drums and presses,
provide several opportunities for volatile organics to be
emitted, such as when a press is opened to remove and
transport accumulated sludge, or during pressing, when
volatile liquids may leak from a press into a drip pan
underneath. Emissions from dewatering devices can be
controlled by building an enclosure around the unit and
venting it to a control device (best used for presses or
rotary devices), or by collecting volatile organics in a
condenser above the volatile source, treating the waste, and
discharging it as appropriate (best for thin-film
evaporators). In addition, sludge fixation often generates
volatiles during mixing, when agitation is provided while
adding the fixative agent. Emissions during fixation can be
controlled by installing covers or enclosures that are
vented to a control device.
Temperature
Surface area
Turbulence
Windspeed
Concentration
Volatility
Containers
Submerged Fill Piping has been shown to decrease emissions
by 65 percent relative to splash filling. In submerged
filling, an influent pipe is inserted below the existing
liquid surface in the container. Liquid is introduced into
liquid, rather than spilled on top of the liquid surface,
which reduces splashing and the degree of saturation of the
displaced vapors.
See Tanks
Landfills
Carbon Adsorption. Condensation. Absorption, or Vapor
Combustion are traditionally used to capture and control
See Table 3-3 for descriptions of
air control technologies
emissions.
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Table 3-2. Technologies for Controlling Cross-Media Transfer of Contaminants During Materials Handling Activities (USEPA,
1991)
Remedial Activity
Description of Control Technology
Factors Influencing
Effectiveness
All
to
o
Operational Controls: Those procedures or practices inherent to most
site remediation projects that can be instituted to reduce VOC and
particulate matter emissions. You should, to the extent possible:
/ Plan site remediation for times of year with relatively cooler
temperatures and lower wind speeds to minimize volatilization and
particulate matter emissions.
/ Maintain lower speeds with all vehicles on unpaved roads.
/ Control placement and shape of storage piles. Place piles in areas
shielded from prevailing winds. Shape pile in a way that
minimizes surface area exposed to wind.
/ During excavation, use larger equipment to minimize surface
area/volume ratio of material being excavated.
/ During dumping, minimize soil drop height onto pile, and
load/unload material on leeward side of pile.
/ During transport, cover or enclose trucks transporting soils,
increase freeboard requirements, and repair trucks exhibiting
spillage due to leaks.
Excavation
Covers and Physical Barriers: Physically isolate the contaminated
media from the atmosphere. Include soils (topsoils or clays);
organic solids such as mulch, wood chips, sawdust, or straw,
typically anchored with a net; asphalt/concrete; gravel/slag with
road carpet; synthetic covers (e.g., tarps). Some technologies best
used in active areas, others in inactive areas; see USEPA 1992b for
details.
Foam Coverings: "Blanket" the emitting source with foam, thus
forming a physical barrier to emissions. Also insulate emitting
source from wind and sun, further reducing particulate and volatile
emissions. Several commercially available. Generally used in
active areas.
Site characteristics (terrain,
vegetation, nature of
contaminated media) and needs for
access
Drainage rates, wind speed,
precipitation, surface
roughness, temperature, surface
activity, contaminant
characteristics
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(cont'd)
Table 3-2. Technologies for Controlling Cross-Media Transfer of Contaminants During Materials Handling Activities
(USEPA, 1991)
Remedial Activity
Description of Control Technology
Factors Influencing
Effectiveness
Wind Screens: Provide an area of reduced velocity that allows
settling of large particles and reduces particle movement from
exposed surfaces on leeward side of screen. Also reduce soil moisture
loss due to wind, resulting in decreased VOC and particulate
emissions.
Slurry Cover Sprays: Spray soil piles/excavated areas with a thin
layer composed of a fibrous slurried aggregate that hardens to form a
protective layer (see Sec. 11.6.2 for an example of commercially
available materials).
Wind screen porosity, wind
direction with respect to screen,
wind screen height, soil silt
content
Excavation
(cont'd)
Water Sprays: Agglomerate small particles with larger particles or
with water droplets. Also, water added to the soil cools the surface
soil and decreases air-filled soil porosity, both of which reduce VOC
emissions.
Water Sprays with Additives: Common additives include hygroscopic
salts, bitumens, adhesives and surfactants. Reduce emissions by
adsorbing moisture from the air, thereby increasing the soil moisture
content; agglomerate surface soil particles to form a surface crust;
or reduce water surface tension, thereby increasing wetting capacity
of the water.
Enclosures: Usually self-supported or air-supported structures; for
soil storage piles, usually self-supported structures similar to the
"beehive" used to store road salts. Provide a physical barrier
between the emitting area and the atmosphere.
Application rate, application
frequency, meteorological
conditions, traffic rate
Potential for enclosure materials
to react with contaminants
Transportation
Covers and Physical Barriers: Road carpets are water permeable
polyester fabrics that are placed between the road bed and a coarse
aggregate road ballast, such as gravel, across which vehicles travel.
Creates a physical barrier between moving vehicles and source of
emissions.
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(cont'd)
Table 3-2. Technologies for Controlling Cross-Media Transfer of Contaminants During Materials Handling Activities
(USEPA, 1991)
Remedial Activity
Description of Control Technology
Factors Influencing
Effectiveness
to
to
Dumping
Covers on Loads: Cover all loads being moved by truck, open piping, or
other conveyance with tarps, roofs, or other structures that will
eliminate or reduce the likelihood of particulate release into the
atmosphere.
Water Sprays of Active Areas: See Excavation
Dust Suppressants: See Excavation
Water Sprays: Water can be sprayed in a curtain-like fashion over the
bed of a truck (or over any conveyance system, such as a moving belt)
during dumping; see Excavation for details on how water sprays work
Water Sprays with Additives: Used like water sprays (see above), with
additional substances such as surfactants; see Excavation
Preparation of
Contaminated
Media and Feeding
Media into
Remediation
System
Covers and Physical Barriers. See Excavation
Enclosures. See Excavation
Collection Hoods: Commonly used in small areas (e.g., waste
stabilization/solidification mixing silos, bioremediation
reactors) and route those emissions to air pollution control devices.
Capture emissions by creation of an air flow after the emitting source
that is sufficient to remove the contaminated air.
Distance between hood and
emissions source; volumetric flow
rate into hood; surrounding air
turbulence; hood design
-------
(cont'd)
Table 3-2. Technologies for Controlling Cross-Media Transfer of Contaminants During Materials Handling Activities
(USEPA, 1991)
Remedial Activity
Description of Control Technology
Factors Influencing
Effectiveness
Storage of
Waste/Residuals
Covers and Physical Barriers: See Excavation
Foam Coverings: See Excavation
Wind Screens: See Excavation
Water Spravs: See Excavation
Water Spravs with Additives: See Excavation
to
OJ
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Table 3-3. Technologies for Reducing Contaminant Concentrations in Air Emissions Generated During Remediation
(USEPA, 1995 and 1992b)
Technology
Incineration
~ Catalytic (also
known as catalytic
oxidation)
— Regenerative
Thermal
Adsorption
~ Nonregenerable
~ Modified
Description
Contaminant-laden waste gas is heated with auxiliary fuel to
between 600° and 900°F. The waste gas is then passed across a
catalyst where the VOC contaminants react with oxygen to form
carbon dioxide and water. (USEPA, 1992b)
Contaminated air is preheated, then combusted to oxidize the
organic volatiles. The clean gas exiting the combustion
chamber is cooled by passing through cool packed beds, then
discharged to the atmosphere. Remaining contaminated air is
reheated, then passed through packed beds, with clean air
cooled and discharged. The cycle of heating, cooling, and
discharge is repeated as necessary. (USEPA, 1995)
Organics are selectively collected on the surface of a porous
solid. Typical adsorbents include activated carbon, silica
and aluminum-based adsorbates. (USEPA, 1995)
Air stream containing volatiles flows upward through one or
two fixed beds of adsorbent. Volatiles are adsorbed until
breakthrough occurs, at which time adsorbent is replaced.
(USEPA, 1995)
Systems designed specifically for low concentrations (less
than 100 ppm) of organic volatiles in gas, which most treatment
systems are not designed to accommodate. Adsorption treatment
is followed by treatment of the concentrated volatiles in the
regenerated gas (by incineration), or volatiles below
regulatory limits are discharged into atmosphere. (USEPA,
1995)
Factors Influencing
Effectiveness
Waste gas composition
Useful for low concentrations of
VOCs at low to moderate feed
rates
Must be used in conjunction with
units that recover or destroy
organic volatiles
At high influent concentrations,
not generally cost-effective
because of large volumes of
adsorbent that must be used
-------
Table 3-3. Technologies for Reducing Contaminant Concentrations in Air Emissions Generated During Remediation (cont'd)
(USEPA, 1995 and 1992b)
Technology
Description
Factors Influencing
Effectiveness
~ Fabric Filter
Designed for control of participate emissions from point
sources. One or more isolated compartments containing rows of
fabric bags or tubes. Particle-laden gas passes up along the
surface of the bags then radially through the fabric.
Particles are retained on the upstream face of the bags, while
the clean gas stream is vented to the atmosphere. (USEPA,
1992b)
Flue gas temperature, gas stream
composition, particle
characteristics
~ Fiigh Efficiency
Particulate Air
Filter (HEPA)
to
Used at sites requiring 99.9% or greater particulate removal.
Can be used as a particulate matter polishing step in
ventilation systems for enclosures or with
solidification/stabilization mixing bins. (USEPA, 1992b)
Comprised of a series of filters, filter housing, duct work,
and a fan. Filters are aligned in series, in parallel, or in a
combination. Air is forced over the filters; larger
particulates are collected on prefilters, finest particulates
are collected on filters. When breakthrough occurs, filters
are replaced and disposed of.
Moisture content of contaminated
air stream; degree of
particulate matter loading
Absorption
Organics in the gas stream are dissolved in a solvent liquid,
such as water, mineral oil, or other nonvolatile petroleum
oil. The contact between the absorbing liquid and the vent gas
is accomplished in counter current spray towers, scrubbers, or
packed or plate columns. In most cases, the volatiles are
stripped from the scrubbing liquid; the volatiles are then
recovered as liquids by a condenser. (USEPA, 1995)
Works better at higher volatile
concentrations
Other Commercial Technologies
Enhanced
Adsorption
Combines wet scrubbing, carbon adsorption, and ozone
reactions; ultimately all organic volatiles are oxidized to
carbon dioxide, water, and if chlorine is present in the
contaminated air stream, hydrochloric acid. (USEPA, 1995)
Periodic
replacement/regeneration of
saturated filter media provides
smooth and effective operation
-------
Table 3-3. Technologies for Reducing Contaminant Concentrations in Air Emissions Generated During Remediation (cont'd)
(USEPA, 1995 and 1992b)
Technology
Description
Factors Influencing
Effectiveness
Internal
Combustion
Engines
Uses a conventional automobile or truck internal combustion
engine as a thermal incinerator of contaminated gas streams.
(USEPA, 1992b)
Optimum air/fuel mixture for
complete combustion
~ Membranes
Membrane concentrates organic solvents by being more
permeable to organic constituents than to air. A pressure
difference is imposed across a selective membrane (with a
compressor or vacuum), which drives the separation of the
solvent from the gas stream. The stripped-off gas is either
vented or recycled to the source of contamination. (USEPA,
1992b)
Solvent permeability (flux
across the membrane), separation
factor (degree of concentration
the membrane can achieve)
to
~ Condenser
Volatile components of a vapor mixture are separated from the
remaining gas by a phase change. Condensation occurs when the
partial pressure of the volatile components is greater than or
equal to its vapor pressure, which can be achieved by lowering
the temperature or increasing the pressure of the gas stream.
(USEPA, 1992b)
Characteristics of vapor stream,
condenser operating parameters
~ Wind Screens
Provide limited control of VOC emissions by increasing the
thickness of the laminar film layer (stagnant boundary layer)
on the leeward side of the screen; also reduce soil moisture
loss to wind, resulting in decreased VOC emissions. (USEPA,
1992b)
Wind screen porosity, wind
direction with respect to wind
screen, wind screen height, soil
silt content
Emerging Technologies
~ Corona Discharge
Uses a high voltage/low current electrical charge to destroy a
wide range of molecules in a gas stream containing organic
volatiles. (USEPA. 1995)
-------
Table 3-3. Technologies for Reducing Contaminant Concentrations in Air Emissions Generated During Remediation (cont'd)
(USEPA, 1995 and 1992b)
Technology
Description
Factors Influencing
Effectiveness
Heterogeneou
s
Photocatalys
is
Uses a near-ultraviolet light to continuously activate a
semiconductor (such as titanium dioxide). The activated
surface of the semiconductor then acts as a catalyst for the
oxidation of the organic volatiles in air. (USEPA, 1995)
Possibly contaminant
concentrations (incomplete
reactions when concentrations
are high); humidity (high
humidity may reduce
effectiveness)
~ Biofiltration
Offgases containing biodegradable organic compounds are
vented, under controlled temperature and humidity, through a
biologically active material. The microorganisms contained
in the bed of compost-like material digest or biodegrade the
organics to carbon dioxide and water. (USEPA, 1995)
to
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Table 3-4. Examples of Technologies for Controlling Cross-Media Transfer to Water
Technology
Description
Purpose
Temporary Diversion
A temporary ridge or excavated channel
or combination ridge and channel
constructed across sloping land on a
predetermined grade (USDA, 1995)
Protects work areas from upslope runoff
and to divert sediment-laden water to an
appropriate sediment trapping facility
or stabilized outlet
Filter Berms
to
oo
A temporary ridge of gravel or crushed
rock constructed across a graded right-
of-way (EPA, 1972)
Retains sediment on-site by retarding
and filtering runoff while at the same
time allowing construction traffic to
proceed along the right-of-way. Used
primarily across graded rights-of-way
that are subject to vehicular traffic.
Also applicable for use in drainage
ditches prior to roadway paving and
establishment of permanent ground
cover.
Infiltration Basins
Impoundments where incoming stormwater
runoff is stored until it gradually
exfiltrates through the soil of the
basin floor. Removal of pollutants is
accomplished by adsorption, straining,
and microbial decomposition in the basin
subsoils as well as the trapping of
particulate matter within pretreatment
areas. (MWCOG, 1992)
Collects sediments and pollutants
Temporary Sediment Traps
Small, temporary ponding basins formed
by construction of an embankment or
excavated basin (USDA, 1995)
Detains sediment-laden runoff from
small disturbed areas for a sufficient
period of time to allow the majority of
sediment and other floating debris to
settle out
Diversion Dikes
A combination of ridge and excavated
channel constructed to divert surface
flow
Diverts overland flow from certain
areas away from unstabilized or
contaminated areas (USDA, 1995)
-------
Table 3-4. Examples of Technologies for Controlling Cross-Media Transfer to Water (cont'd)
Technology
Description
Purpose
Riprap
A combination of large stones, cobbles
and boulders used to line channels,
stabilize banks, reduce runoff
velocities, or filter out sediments
(MWCOG, 1992)
Prevents erosion on steep or cleared
slopes (USDA, 1995)
Sand Filters
to
A filtration system constructed of
layers of peat, limestone, and/or
topsoil, and may also have a grass cover
crop. The first flush of runoff is
diverted into a self-contained bed of
sand. The runoff is then strained
through the sand, collected in
underground pipes and returned to the
stream or channel. (MWCOG, 1992)
Treats stormwater runoff; removal rates
for sediments and trace metals are high,
and moderate for nutrients, BOD, and
coliform
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Table 3-5. Examples of Field Monitoring Technologies (Freeman and Harris, 1995, and USEPA, 1994)a
Technique
Description and Application to Air Emissions
Applicable To1
Types of Detectors
Commonly Used2
Direct
Measurement
with Hand-Held
Equipment
Hand-held organic vapor analyzers provide quick readings on
presence of organic vapors. Can be used to check for
emissions from specific equipment (e.g., pipe seals,
gaskets), or to identify when emissions levels change from
one area to another.
VOCs, some
SVOCs
OVA
Head Space
Analysis
Involves collecting waste material in a bottle with
"significant" head space and allowing the waste/head space
to reach equilibrium. The head space gas is then analyzed for
volatile compounds with simple real time analyzers.
VOCs, SVOCs
OVA, PID for VOCs and
SVOCs
Realtime
Instrument
Survey
Screening takes place directly over the waste to obviate
modeling by testing the air above the surface. This approach
can identify "hot spots" of emissions and zones of similar
emissions.
VOCs, SVOCs,
PM
OVA, PID for VOCs and
SVOCs; DM for PM
Upwind/
Downwind Survey
Monitors upwind/downwind concentrations of ambient target
compounds. Often, realtime analyzers with flame ionization
and photoionization detection are used for organic emission
detection.
VOCs, SVOCs
OVA, PID for VOCs and
SVOCs; DM for PM;
GC/MS
Surface Flux
Chamber
A direct measurement approach applicable to many kinds of
waste sites and capable of generating both undisturbed and
disturbed emission rate data for volatile and semivolatile
compounds. The technology uses a chamber to isolate a
surface emitting gas species (organic or inorganic);
emission rates are calculated by measuring the gas
concentration in the chamber and using the chamber sweep air
flow rate and surface area.
VOCs, SVOCs,
PM
OVA, PID for VOCs and
SVOCs; SD, GC/MS
-------
Table 3-5. Examples of Field Monitoring Technologies (cont'd)
(Freeman and Harris, 1995, and USEPA 1994)a
Technique
Description and Application to Air Emissions
Applicable To1
Types of Detectors
Commonly Used2
Transect
An indirect method that involves the collection of ambient
concentration data for gaseous compounds and/or particulate
matter using a two-dimensional array of point samplers.
These data, along with micro-meteorological data, can be
used to estimate the emission rate of the source by using a
dispersion model. Data can be obtained that represent
emissions from a complex or heterogeneous site or an activity
that generates fugitive air emissions.
VOCs, SVOCs
Fourier Transform
Infrared Optical
Remote Sensing
Detector;
Ultraviolet-
Differential Optical
Absorbance Sensor;
Filter Band Pass
Absorption Detector,
Laser, PAS
Visual
Inspection
Periodic visual inspection of pipes and joints for corrosion
and leaks could provide early detection and prevent major
leaks or spills.
Liquids and
gases
Occasionally aided
by hand-held
telescopes, or
magnifying glass.
Periodic
Watershed
Evaluation
The impact of cleanup activities on the watershed could be
periodically evaluated by monitoring the following
indicator parameters:
• Level of siltation
• Water clarity
• Habitat and vegetation
Most of the above monitoring could be accomplished by visual
inspections.
Water and
sediment
For details on screening survey, monitoring instruments, limitations of portable VOC detection devices, performance
criteria of VOC detectors, data handling, and calibration procedures, see cited reference ~ USEPA, 1994, pages 37-
47.
VOCs = Volatile Organic Compounds; SVOCs = Semi-Volatile Organic Compounds; some volatile inorganic compounds are
amenable to techniques suitable for SVOCs; and PM=Particulate Matter.
OVA = Organic Vapor Analyzer; PID = Photoionization Detector; SD = Specific Compound Detector; DM = Dust Monitor; and
GC/MS = Gas Chromatography/Mass Spectrometry
-------
3.2 Relative Costs of Implementing BMPs
EPA did not conduct an exhaustive analysis of the costs associated with
implementing the practices outlined in this document. Conducting such an analysis is
complicated by two key factors: (1) many of the suggested practices do not involve
equipment purchases nor do they entail a well-defined or discrete task outside the
integral remediation activities, and (2) cost data available on soil cleanups tend to be
aggregated such that costs for performing specific practices are not discernable. In
addition, the practices applicable or necessary for a particular cleanup, and the
magnitude to which they are performed, can vary based on the characteristics of the site
and those of the contaminants present.
Notwithstanding, as a general rule, EPA does not expect cleanup managers to incur a
significant incremental cost in implementing the practices suggested in this document.
In fact, at many sites, cleanup managers are already implementing the applicable
practices as part of the good management practices they follow whenever performing
cleanups. The costs of implementing these practices are subsumed into their overall
cleanup costs. EPA recognizes that, in some cases, additional costs may be incurred to
implement cross-media transfer controls. However, in these cases, these costs would
probably need to be incurred anyway to meet existing state or federal cleanup
requirements or to avert potential future costs to address cross-media transfers of
contaminants. Based on preliminary cost data gathered during field validation of BMPs,
these costs are generally an integral part of the cost of remedial activity and are
estimated to comprise about two to six percent of the overall cleanup cost.
EPA welcomes any data that will help to more fully characterize the costs related
to minimizing cross-media transfers of contaminants.
Although actual cost figures are not available at this time for the recommended
BMPs, studies have been conducted earlier by EPA on the relative cost effectiveness for
point source VOC controls as shown in Figure 3-1 (USEPA, 1992b).
32
-------
Cost effective
range
Technology
effective ~
Carbon adsorption
Catalytic oxidation
— I—1
Condenser
Biofilter
I.C engine
Membrane
Thermal processor
'1'
Thermal incineration
u.v.
0.1 1.0 10 100 1,000 10,000 100,000
VOC concentration (ppm)
Figure 3-1. Relative Cost Effectiveness for Point Source VOC Controls
(USEPA, 1992b)
3.3
1.
2.
3.
4.
References
USDA. 1995. Illinois Urban Manual - a technical manual designed for urban
ecosystem protection and enhancement, prepared for Illinois Environmental
Protection Agency, by the U.S. Department of Agriculture (USDA), Natural
Resources, Conservation Service, Champagne, Illinois.
USEPA. 1995. Survey of Control Technologies for Low Concentration Organic Vapor
Gas Streams, EPA/456/R-95/003, Office of Air Quality Planning and Standards,
Research Triangle Park, May.
Freeman, Harry M. and Eugene F. Harris. 1995. Hazardous Waste Remediation:
Innovative Treatment Technologies, Technomic Publishing Co Inc Lancaster
PA.
USEPA. 1994. Control Technologies for Fugitive VOC Emissions from Chemical
Process Facilities, Handbook, EPA/625/R-93/005, Office of Research and
Development, Cincinnati, March.
USEPA. 1992a. Seminar Publication, Organic Air Emission from Waste Management
Facilities, EPA/625/R-92/003, Office of Air Quality Planning and Standards,
Research Triangle Park, August.
33
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6. USEPA. 1992b. Control of Air Emissions from Superfund Sites, EPA/625/R-92/012,
Office of Research and Development, November.
7. Metropolitan Washington Council of Government (MWCOG). 1992. A Current
Assessment of Urban Best Management Practices, a report prepared for U.S. EPA's
Office of Wetlands, Oceans, and Watersheds, March.
8. USEPA. 1991. Engineering Bulletin, Control of Air Emission from Materials
Handling During Remediation, EPA/540/2-91/023, Office of Research and
Development, October.
9. USEPA. 1989. Seminar Publication, Corrective Action Technologies and
Applications, EPA/625/4-89/020, Office of Research and Development, Cincinnati.
10. USEPA. 1988. Project Summary. Fugitive Dust Control Techniques at Hazardous
Waste Sites: Results of Three Sampling Studies to Determine Control
Effectiveness, EPA/540/S2-85/003.
11. USEPA. 1972. Guidelines for Erosion and Sediment Control Planning and
Implementation, EPA-R2-72-015, Office of Research and Development, August.
34
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4.0 Chapter Four: BMPs for CONTAINMENT TECHNOLOGIES
This chapter focuses on the generally accepted best management practices (BMPs) to
minimize cross-media transfer of contaminants during remedial actions or corrective
measure implementations when using containment technologies to treat soils or solid
media. BMPs are meant only to provide guidance and general recommendations on the
operational practices of selected technologies. BMPs are not meant to direct or dictate
the selection of appropriate technologies.
4.1 Definition and Scope of Containment Technologies (for BMPs)
Containment technologies use physical barriers to retain, immobilize, or
isolate contaminated media from the surrounding environment and to minimize migration
of the contaminants without destroying them.
Many types of containment technologies are currently being used for soils
treatment or disposal. Considering their similarity in cross-media transfer potentials,
the following treatment technologies are listed as a few examples of containment
technologies (for the purpose of BMPs):
• Storage Piles/Vapor Sheds • Slurry Walls
• Storage Containers/Drums • Salt Bed Disposal
• Tank Installations • Geomembrane Barriers
• Impoundments • Landfill Cover Systems
• Siltation Basins • Landfill Liner Systems
The scope of BMPs for containment technologies is not limited to the above listed
technologies. Any treatment technology that meet the key features of containment
technologies, as described below, should generally be considered as containment
technologies for the purpose of BMPs.
Diagrams of two typical containment technologies are shown in Figures 4-1 and 4-2.
Details of most of the above technologies are provided in the cited references (USEPA,
1992a and 1993a, and Rumer and Ryan, 1995). The salt bed disposal system used at the Waste
Isolation Pilot Plant (WIPP) is an unique containment technology designed for the safe
disposal radioactive wastes (DOE, 1995).
4.1.1 Key Features of Containment Technologies for the Purpose of BMPs
• Do not destroy contaminants.
• Immobilize contaminants.
• Provide temporary storage and containment of wastes.
• Provide barriers that contain the waste and control horizontal
and/or vertical movement of contaminants. Typical construction
uses either soil-bentonite or cement-bentonite mixtures.
• Provide partial barriers that control infiltration of
precipitation, thereby reducing the amount of leachate generated as
35
-------
the water passes through the waste. The systems consequently reduce
horizontal and downward migration of contaminants.
Reduce contaminant movement upward and prevent the waste from
physical contact with the surface water.
36
-------
WASTE MATERIAL
SLURRY WALL
BEDROCK OR AQUITARD
Figure 4-1. Cross-Sectional View Showing Implementation of Slurry Walls
(USEPA, 1992a)
vegetation —», \l// \\// \l// \\// \\//
topsoil
protection layer
drainage layer
geomembrane/soil
barrier layer
or geosynthetic
clay liner (GCL)
-^:5~;
o
o
* O * I*
0
0
, .p,
„
'
•=^"=^"=
0 ^
0
C9
c> waste
Q? o
.
»
* °. * 0 * " 0
00 C o O
« "J, » * 0 *
ifjl^i
03 C>
0
0
granular or geotextile filter
geomembrane
w/overlying protective geotextile
geotextile gas
collection layer
Figure 4-2. Cross-Section of Multilayer Landfill Cover (USEPA, 1993a)
37
-------
4.2 Containment Technology Description
Although many different technologies fall within the umbrella of the containment
technology group, the two most commonly encountered at present are slurry walls and
landfills. A brief description of slurry walls and landfill cover systems are provided
here. These technologies often require an extensive preparation of the site (e.g.,
geotechnical characterization and reinforcement of existing subsurface structures at
the site before constructing a slurry wall) and/or pretreatment of the waste being
contained (e.g., excavation and removal of highly contaminated waste from the site before
constructing a landfill cover system).
The construction of slurry walls involves the excavation of a vertical trench
using a bentonite-water slurry to hydraulically shore up the trench during construction
and seal the pores in the trench walls via formation of a "filter-cake." A cross-
sectional view of a slurry wall is shown on Figure 4-1. Slurry walls are usually 20 to 80
feet deep with widths from 2 to 3 feet (USEPA, 1992a). Depending on the site conditions
and contaminants, the trenches can be either excavated to a level below the water table to
capture chemical "floaters" (this is termed as a "hanging wall") or extended ("keyed")
into a lower confining layer (e.g., bedrock or aquitard). Similarly, on the horizontal
plane the slurry wall can be constructed around the entire perimeter of contaminated
media or portions thereof (e.g., upgradient or downgradient). The principal
distinctions among slurry walls are differences in the low-permeability materials used
to backfill the trenches, namely the water content and ratios of bentonite/soil or
bentonite/cement used to backfill the trench. In most cases using bentonite/soil, the
excavated soil is mixed with bentonite outside the trench. A relatively new development
in the construction of slurry walls is the use of mixed in-place walls (also referred to as
soil-mixed walls). This method of vertical barrier construction is recommended for sites
where soft soils are encountered, there are concerns for failure of traditional trenches
due to hydraulic forces, or space availability for construction equipment is limited
(USEPA, 1992a).
Grouting, including jet grouting, employs high pressure injection of a low
permeable substance into fractured or unconsolidated geologic material. This technology
can be used to seal fractures in otherwise impermeable layers or construct vertical
barriers in soil through the injection of grout into holes drilled at closely spaced
intervals (i.e., grout curtain).
The design of landfill covers is also site-specific and depends on the intended
functions of the system. Many natural, synthetic and composite materials and
construction techniques are available. Covers can range from a one-layer system of
vegetated soil to a complex multi-layer system. A cross-sectional view of atypical
multilayer landfill cover is given in Figure 4-2. Generally a fill layer of clean soils is
placed first above the waste and graded to establish the base of the cover system. Then, a
bottom layer, which may be a granular gas collection layer, is placed on top of the fill
layer as a base for the remainder of the cover. The barrier layer is installed next. The
materials used in the construction of the barrier layer are low-permeability soils and/or
geosynthetic clay liners (GCLs). A flexible membrane liner (FML) layer is placed on top
of the low-permeability barrier layer. These two layers prevent water infiltration into
the waste. The high permeability drainage layer is placed on top of FML to drain the water
38
-------
away that percolates through the top of the cover. A granular or geotextile filter fabric
may be laid on top of the drainage layer for protecting the drainage layer from clogging
due to fine silts or clay deposits from the percolating water. A protective fill soil and
topsoil are then applied and the topsoil seeded with grass or other vegetation adapted to
local conditions. Covers are usually constructed in a crowned or domed shape with side
slopes as low as is consistent with good stormwater runoff characteristics. Other
materials may be used to increase slope stability. Steeply mounded landfills can have a
negative effect on the construction and stability of cover. For example, there may be
difficulty anchoring a geomembrane to prevent it from sliding along the interfaces of the
geomembrane and soils.
Landfill covers are presently constructed in a variety of combinations depending
upon the site-specific conditions. The most critical components of a cover with respect
to selection of materials are the barrier layer and the drainage layer. The barrier layer
can be a GCL and/or low-permeability soil (clay). Other alternative barrier materials
have also been identified in the document (USEPA, 1993a) cited under reference.
4.3 Cross-Media Transfer Potential of Containment Technologies
(a) General
General cross-media transfer potentials during site preparation, pre-treatment,
and post-treatment activities have been addressed in Chapter 2.
(b) Additional Concerns for Specific Containment Technologies
In addition to the general concerns and BMPs that are outlined in Chapter 2,
containment technologies pose the following technology-specific concerns:
• Geomembranes are vulnerable to puncturing during installation.
Inadequate preparation of the surface on which the geomembrane will
be laid, or improper placement of materials on top of the geomembrane
may result in punctures that allow infiltration of water and escape
of volatile contaminants. Proper seaming of adjacent sheets also is
critical for effective containment using this technology (Rumer and
Ryan, 1995).
• Landfill cover systems pose the same cross-media transfer potential
as geomembrane liners. Breaches in the system's integrity could
allow infiltration of rain water. The infiltration could then
result in leaching of contaminants from the waste into surrounding
soil and underlying groundwater. VOCs may also escape from the
landfill cover system by diffusion through the cover layers and by
"barometric pumping" through vents (USEPA, 1992c). Breaches in the
landfill cover system and improper design and installation of
landfill gas collection systems also could allow volatile
contaminants to escape into the atmosphere.
39
-------
• Since salt bed disposal is a deep underground entombment of
contaminants, potential for releases are minimal. However,
improper storage and handling of the wastes before placing them in
the deep underground vaults could cause aboveground migration of
contaminants.
4.4 Best Management Options to Avoid Potential Cross-Media Transfers for Containment
Technologies
General BMPs to prevent potential cross-media transfer of contaminants during
site preparation, pre-treatment, and post-treatment activities have been addressed in
Chapter 2. Only technology-specific treatment activities and possible BMP options to
control cross-media transfer of contaminants during these activities are furnished
below.
Containment Treatment Activities - During implementation of the containment
technologies the following activities are most commonly undertaken:
4 Excavation; trenching; storage of soils, sediments, and materials that
will be used to construct containment system; construction of slurry
walls, landfill covers, and other containment units. In the case of deep
containment, such as with salt beds, extensive underground excavation is
required Secondary activities include surface water diversion and
control, on-site pumping and treating, installation of cut-off trench type
interceptors, installation of leachate collection systems.
During these activities, the following BMPs should be considered for containment
technologies:
/ In the case of slurry walls, when there is a potential for outward migration
and contamination of groundwater, periodic pumping and treating of the
contaminants from the contained area and maintaining an inward hydraulic
gradient from outside to inside the slurry wall may be considered. This
practice has been observed in the field during field validation of BMPs (see
Section 11.7.1).
/ All soils should be analyzed and processed before they are disposed of off-
site (see Section 11.7.2).
/ Air quality trends should be constantly monitored. If air quality degrades
as a result of construction activities, those activities should be altered
or stopped until air quality is restored (see Section 11.7.2).
/ Climatological extremes (e.g., high wind) should be considered when
implementing containment technologies. See Chapter 2, Section 2.2.2, for
details on consideration of climatological extremes.
/ All debris should be covered during construction (see Section 11.7.2).
40
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/ Temporary sumps should be used to collect stormwater runoff from the site
during construction (see Section 11.7.2).
/ Temporary arrangements should be provided that protect areas that are
vulnerable to damage and migration of contaminants during construction
(e.g., road covers). See Chapter 3 and Section 11.7.2 for more details.
/ Effective VOC, methane, and odor emissions should be controlled by using
covers, foam suppressants, enclosures, vapor collection systems, gas
flares, or other methods as appropriate (USEPA, 1992b).
/ Contaminated liquids generated from treatment operations should be treated
and/or disposed in a protective manner as specified in Chapter 3 and Chapter
6, Section 6.4, of this document.
Additional Post-Treatment Activities - In addition to the general post-treatment
BMPs provided in Chapter 2, the following BMPs should be considered for containment
technologies:
/ Routine audits should be conducted to verify the integrity of the
containment structure with accompanying documentation.
/ For most containment technologies, the production of residuals is
generally not a concern. However, construction of soil-bentonite slurry
walls can generate large quantities of excess slurry and excavated
materials. In most cases, it is expected that these excess materials are
not hazardous (Freeman and Harris, 1995). However, if the excavated soil
and slurry cannot be used as backfill, they should be properly stored onsite
or transported and disposed offsite.
4.5 Waste Characteristics that May Increase the Likelihood of Cross-Media
Contamination for Containment Technologies
The effectiveness of containment technologies could be compromised and undue
cross-media contamination may be caused under certain conditions identified in this
subsection. However, some of these limitations could possibly be overcome with various
technology specific modifications and variations. Please refer to technology-specific
references provided at the end of this chapter for additional information about
modifications or variations that can be used to enhance the effectiveness of containment
technologies.
*• When contaminant concentrations exceed 10% to 25% of their explosive
limits, they are potentially unsafe to handle or can pose a threat to the
integrity of the containment system (USEPA, 1994).
*• Ignitable wastes may present fire hazards when treated using containment
technologies that are exothermic (generates heat).
41
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* Very low pH values (<4.0 Standard Unit (SU)) or high (> 11 SU) may lead to
corrosion in liners and equipment (USEPA, 1994).
>• Strong oxidizers can corrode slurry walls and geomembranes.
4.6 References
1. Freeman, Harry M. and Eugene F. Harris. 1995. Hazardous Waste Remediation:
Innovative Treatment Technologies. Technomic Publishing Co., Inc., Lancaster,
PA.
2. Rumer, R.R. and M.E. Ryan. 1995. Barrier Containment Technologies for
Environmental Remediation Applications, John Wiley and Sons, Inc., August.
3. U.S. Department of Energy (DOE). 1995. Draft No Migration Variance Petition,
Waste Isolation Pilot Plant, DOE/CAO-95-2043, Carlsbad Area Office, Carlsbad, NM.
May.
4. USEPA. 1994. BMP Development Workshop Summary - Containment Technologies. Office
of Solid Waste, Permits and State Programs Division, August.
5. Dutta, S. 1993. Modified Cover System for Hazardous Waste Landfills in Semi-Arid
Areas, Proceedings of the 3rd International Conference on Case Histories in
Geotechnical Engineering, St. Louis, MO, June.
6. USEPA. 1993a. Engineering Bulletin-Landfill Covers. EPA/540/S-93/500. Office
of Research and Development, Cincinnati, February.
7. USEPA. 1993b. Environmental Fact Sheet, Controlling the Impacts of Remediation
Activities in or Around Wetlands, EPA/530/F-93/020, Office of Solid Waste and
Emergency Response/Office of Waste Programs Enforcement, August.
8. USEPA. 1992a. Engineering Bulletin-Slurry Walls, EPA/540/S-92/008, Office of
Research and Development, Cincinnati, October.
9. USEPA. 1992b. Engineering Bulletin, Control of Air Emissions from Materials
Handling During Remediation, EPA/540/2-91/023, October.
10. USEPA. 1992c. Organic Air Emissions from Waste Management Facilities, EPA/625/R-
92/003, May.
11. USEPA. 199 la. Handbook, Stabilization Technologies for RCRA Corrective Actions,
EPA/625/6-91/026, Office of Research and Development, Washington, DC, August.
12. USEPA. 199Ib. SITE Technology Demonstration Summary, International Waste
Technologies/Geo-Con In Situ Stabilization/Solidification Update Report,
EPA/540/S5-89/004a, Center for Environmental Research Information, Cincinnati,
OH.
42
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13. USEPA. 1989. Technical Guidance Document, Final Covers on Hazardous Waste
Landfills and Surface Impoundments, EPA/530/SW-89/047, Office of Solid Waste and
Emergency Response, Washington, DC.
43
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5.0 Chapter Five: BMPs for SOIL WASHING
This chapter focuses on the generally accepted best management practices (BMPs) to
minimize cross-media transfer of contaminants during remedial actions or corrective
measure implementations when using soil washing technologies to treat soils or other
solid media. BMPs are meant only to provide guidance and general recommendations on the
operational practices of selected technologies. BMPs are not meant to direct or dictate
the selection of appropriate technologies.
5.1 Definition and Scope of Soil Washing (for BMPs)
Soil washing (for BMPs) is an ex situ, generally water-based process that
relies on traditional chemical and physical extraction and separation processes for
removing a broad range of organic, inorganic, and radioactive contaminants from soils
or solid media (USEPA, 1993a). This aqueous-based technology uses mechanical
processes (e.g., scouring) and/or solubility characteristics of contaminants to
separate contaminants from excavated soils or solid media. The process frees and
concentrates contaminants in a residual portion of the soil (typically 5 to 40% of the
original volume), where they can be subsequently treated by other remediation
techniques or managed in compliance with applicable regulations.
A typical schematic of a soil washing system is shown on Figure 5-1.
Because of their similarity in cross-media transfer potentials the following
treatment technologies are listed as a few examples of soil washing technologies (for the
purpose of BMPs):
• Soil Washing • Excavating, Dredging, and
• Solvent Extraction Conveying
• Debris Washing • Wet and Dry Screening
• Magnetic Separation • Gravity Concentration
• Froth Flotation
The scope of BMPs for soil washing is not limited to the above listed technologies.
Any treatment technology that satisfies the key features of soil washing could be
considered as soil washing technologies for the purpose of BMPs. BMPs for soil flushing
technologies and other in situ technologies are addressed under Chapter 10 of this
document. Solvent extraction has been included in this chapter because the treatment
process closely matches the key features of this BMP category.
5.1.1 Key Features of Soil Washing Technology for the Purpose of BMPs
• A non-destructive process which separates contaminants from solids
and concentrates the contaminants for collection and/or treatment.
• An ex situ technique normally requiring excavation of soil or
sediment and other materials handling operations, such as pre-
44
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screening of oversize (e.g., vegetation, debris, etc.),
stockpiling, conveying, and particle size separation.
Applicable for treating a wide variety of organic, inorganic, and
radioactive contaminants in soil or solid media.
• Commonly relies on additives such as surfactants or solvents to
enhance the effectiveness of the soil washing process.
• Significantly reduces the volume of contaminated soil (USEPA,
1992a).
5.2 Soil Washing Technology Description
A synopsis of the technology description is provided here. For detailed
information on this technology see the relevant references cited in this chapter.
Characterizatic
Excavated area
A
Materials >
Process water
treatment
and recycle
r
#f$9
Excavated
soil pile j
J«/x ,
/£*
Ovens
mater
Return to excavated area ^
^L
iized
al
L .
r ^ .
<
1
S
E
P
A
R
A
T
I
O
N
i
jt
Dffsite
Usposalas
.nliH uract<>
I
k
>, „
Fines
I
k
Froth
j
^ Cos
i
jrse
i
Clean soil
fraction
>.
^
f
Contaminants
and sludge
1
Further treatment
& disposal
Soil returned to site of origin
Figure 5-1. Basic Soil Washing Flow Diagram (USEPA, 1993a)
The soil washing process begins with the excavation and preparation of the
feedstock soil. Soil preparation can involve the mechanical screening of the feedstock
45
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to remove rocks, debris, and other oversized material (USEPA, 1993a). The treatment
process generally involves the use of wet, mechanical scrubbing and screening processes
to separate particles containing the contaminants. Most commercially available soil
washing systems utilize mechanical screening devices to remove oversize materials and
separation systems to generate coarse- and fine-grained fractions. The process also
includes treatment units for washing and systems for scrubbing the separated fractions.
The specific processes and equipment used depend upon individual site characteristics.
After excavation and preparation, the feedstock soil is actively mixed with water
or an amended water-based washing fluid, which separates the contaminants from the soil.
The soil is then separated from the spent fluid, and the soil is recovered in two distinct
fractions. One fraction comprises a relatively high volume, coarse sand and gravel
fraction that is clean and suitable for use as on-site fill; the other usually comprises a
smaller volume, fine silt and clay fraction that typically carries the bulk of the
contaminants. From the coarse soil fraction, a contaminated, naturally occurring
organic material may be separated as a third fraction by specific gravity separation. The
coarse sand and gravel fraction is generally passed through an abrasive scouring or
scrubbing action to remove the surficial contamination. The washwater in this washing
step may contain a basic leaching agent, surfactant, or chelating agent to help remove
organics or heavy metals. The mixture is agitated by use of high-pressure water jets,
vibration devices, and other means depending upon the equipment (USEPA, 199la). Fine
particles are sometimes further separated in a sedimentation tank with the help of a
flocculating agent.
In the final step, the remaining fine silt, clay and the contaminated washwater are
treated. The contaminated washwater may require precipitation and clarification, which
removes metals and fine soils as a sludge. The fine soils, in which contaminants have been
concentrated, will normally require further treatment or proper disposal in compliance
with applicable regulations.
To increase the efficiency of contaminant removal, sometime chemical agents are
added to the washwater. Acids, such as hydrochloric acid, sulfuric acid, and nitric acid,
may be added to improve the solubility of certain contaminants, especially heavy metals.
Sodium hydroxide, sodium carbonate, and other bases can be used to precipitate
contaminants in the extraction fluid. Dispersion of oily contaminants can be facilitated
by the addition of surface active agents. Various chelating agents such as citric acid,
ammonium acetate, nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid
(EDTA) will remove the available fraction of inorganic contaminants (USEPA, 199 la). For
improved removal in certain cases, the extraction temperature is elevated or an oxidizer,
such as hydrogen peroxide, or ozone is added for chemical oxidation.
5.3 Cross-Media Transfer Potential of Soil Washing Technologies
(a) General
General cross-media transfer potentials during site preparation, pre-treatment,
and post-treatment activities have been addressed in Chapter 2.
(b) Additional Concerns for Soil Washing Technologies
46
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Additives used in the process can increase the potential of direct
spillage of wastewater (e.g., foam with metals and organics) to the
soil and surface water during treatment activities, especially if
soil washing unit is not properly lined and bermed.
In the specific case of solvent extraction, where there are commonly
pressurized tanks and flammable and highly volatile solvents used,
there is potential for VOC emissions due to leaks in pipes, joints,
and valves. Major emission points associated with solvent
extraction are those involved in the distillation process used to
recover the solvent (USEPA, 1992b).
Chelating agents, surfactants, solvents, and other additives are
often difficult and expensive to recover or recycle from the spent
washing fluid by conventional treatment processes, such as,
settling, chemical precipitation, or activated carbon. The
presence of additives in the contaminated soil and treatment sludge
residuals may cause added difficulty in disposing of these residuals
(USEPA, 1993a), thereby increasing the potential for cross-media
transfer.
Additives used in the soil washing, debris washing, wet screening
and froth flotation process can increase the potential of direct
spillage of wastewater to the soil and surface water during
treatment activities as a direct result of excessive foaming or
frothing.
Soil characterization data (e.g., size classifications, levels of
contamination, permeability of soil, and estimates of the
quantities of soil) used for treatability or pilot-scale tests may
not accurately reflect the breadth of soil characteristics actually
found in the field. Accurate characterization is important for the
efficient use of this technology and additional pretreatment of the
soil (i.e., additional drying, crushing and sizing) may be necessary
just prior to operating the technology. Such improper
characterization or lack of adequate pre-treatment may lead to a
higher potential for cross-media transfer than expected.
Treated soil residues from soil washing, wet and dry screening,
gravity concentration and froth flotation may have significantly
different soil characteristics such as permeability and
compactability, and thus, could adversely effect the ground water
flow characteristics of the site where these soils are replaced.
Other constituents at the site could then migrate back into or
through the treated soil.
Wastewaters from soil washing, wet screening, froth flotation and
debris washing may contain diluted amounts of the hazardous
constituents and significant levels of suspended matter. Cross-
47
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media transfer can occur if these residues are released to the
environment without any treatment.
• Improper or incomplete identification of contaminants and lack of
knowledge of their concentrations in the spent washwater may foul up
the system since the washwater is treated and recycled back into the
washing process. This may in turn cause inadequate cleaning and
removal of contaminants and cause cross-media transfer.
• When the fine particles are not separated from the pre-treated
soils, it may result in emission of the fine particles, which
oftentimes bind most of the contaminants.
5.4 Best Management Options to Avoid Potential Cross-Media Transfers for Soil Washing
Technologies
General BMPs to prevent potential cross-media transfer of contaminants during
pre-treatment and post-treatment activities have been addressed in Chapter 2. Only
technology specific treatment activities and possible BMP options to control cross-media
transfer of contaminants during treatment, as well as a few post-treatment BMPs, are
furnished below.
During the soil washing treatment process, the following activities are most
commonly undertaken:
4 Excavation of soils, temporary storage, particle size separation,
transportation/transfer of contaminated soils from loaders to dump trucks,
mixing action, movement of the contaminated media through a conveyor
system, desorption, separation, and washing in an aqueous media.
The following BMPs, when appropriate, are recommended to prevent cross-media
transfer of contaminants for the above activities:
/ Precautions should be taken to avoid foaming (or frothing) and subsequent
overflow by periodically performing visual inspections when additives are
used that have been demonstrated to froth in other situations. Field
testing of small soil samples in jars with excess additives might help
anticipate problems, but should not be used as the only means to anticipate
frothing problems. As a contingency plan, the area underneath the soil
washing unit could also be lined and bermed to collect any potential
spillage.
/ Major emission points associated with solvent extraction, such as, those
involved in the distillation process for recovering solvent, should be
carefully monitored during operation. Process shutdowns may be deemed
necessary if excessive levels are detected.
/ Volumes of soil batches should be carefully managed so that they do not
overfill the containers or exceed the normal operating specification of the
48
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equipment. The soil batches should preferably be run at less than maximum
capacity to prevent leaks or spills.
/ Chelating agents, surfactants, solvents, and other additives should be
carefully selected so as to avoid ones that are difficult and expensive to
recover or treat by conventional processes, such as, settling, chemical
precipitation, or activated carbon. Potential impact of residual soil
washing additives that are anticipated to remain in the soil after
treatment should be examined and replacement plans be adjusted accordingly
(e.g., if acids are used to extract metals from soils, the residual soil may
need to be either limed prior to replacement in order to account for the
acidity expected to be left in the soil or a neutralization step may need to
be included as part of the soil washing process.)
/ Any off-site runoff should generally be prevented from entering and mixing
with the on-site contaminated media by building earthen berms or adopting
similar other measures. Provision should be made to capture the on-site
surface water runoff by diverting it to a controlled depression-area or
lined pit.
/ Most soil washing operations are vulnerable to high wind, especially with
respect to the fugitive dust emission. Weather monitoring and operational
control should be exercised as specified in Chapter 2 of this document.
During excavation and material handling activities as well, meteorological
conditions should be strongly emphasized and evaluated to minimize cross-
media transfer.
/ Mixing, crushing, or conveying activities should generally be conducted
under an environment where the off gases, volatiles, dusts, etc. are all
captured inside a hood or cover or controlled using other control options
listed in Chapter 3. The VOC emissions associated with these activities
should be controlled by capturing and then treating the captured vapor/air.
/ All excavated soils when stored prior to treatment should be securely
covered with plastic liners and these temporary covers need to be
maintained until the storage pile is moved for treatment. The excavated
cells should also be lined, when migration possibilities of contaminated
runoff exist, during precipitation events.
/ During the main treatment activities as specified above, organic or
inorganic vapor emissions should be monitored and appropriate emission
control measures, described in Chapter 3 of this document, should be used to
prevent emissions above the allowable level specified by the regulatory
agency (EPA or authorized state).
/ When treating soils contaminated with explosive wastes, proper safety and
care should be exercised to prevent any explosion during the treatment
process. For conducting safe operations, recommendations provided in the
Handbook (USEPA, 1993c) may be used, when necessary.
49
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/ Periodic system monitoring and evaluation should be performed, if
appropriate, to prevent leaks or spills.
/ When re-using treated soils for restoration of a site, care should be taken
to re-create the original soil texture. The anticipated soil
characteristics of the treated soil should be verified prior to
replacement. This may require the addition of clays, nutrients, or other
materials, some of which can be mixed in from clean soils at the site.
During these soil mixing activities, BMPs for pre-treatment should be
applied (i.e., use covers over areas used for storage or mixing or for
processing small batches; minimize work in high temperatures or in high
wind, etc.).
/ There are four main waste streams generated during soil washing:
contaminated solids from the soil washing unit, wastewater, wastewater
treatment sludges and residuals, and air emissions (Freeman and Harris,
1995). General BMPs for addressing these residuals are provided in Chapter
2; additional BMPs are provided here.
— When collecting moisture or liquids from the treatment process, the
contaminated aqueous stream should generally be collected in a tank
or a lined/containment system. This should prevent the contaminants
from mixing with the normal surface water runoff from the area and
the surrounding natural watercourse. The contaminated aqueous
stream should be treated or disposed of in accordance with the
applicable regulation.
— An enclosed conveyance system, such as a pipeline or hose, should be
used to move contaminated liquids from the soil washing unit to the
containers that will be used to store them.
— Containers that hold residual liquids should be stored in a place in
which they cannot be disturbed or ruptured by large equipment. This
may require construction of a residuals management unit separate
from the treatment and storage areas.
— During post-treatment, residuals that are nearly pure listed waste
(contaminant) or highly concentrated may need to be managed. These
wastes should be dealt with extreme caution and safety to avoid all
possible risks of cross-media transfer of contaminants and treated
or disposed of in compliance with the applicable state and/or
federal regulations.
— Wastewaters containing the hazardous constituents and the high
levels of suspended matter can generally be treated with
conventional wastewater technologies to acceptable regulatory
levels. They should generally be handled on-site as potentially
hazardous wastewaters with appropriate spill prevention
contingencies. Air emissions from these units should also be
50
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evaluated for appropriate control measures (i.e., closed tanks,
covers, etc.) as specified in Chapter 3.
— If solid materials such as granulated carbon filters are used, they
should be removed carefully from the emissions system to avoid
rupturing them and dissipating the carbon materials. They should be
placed into tightly covered containers until they can be recycled or
properly disposed of.
5.5 Waste Characteristics that May Increase the Likelihood of Cross-Media
Contamination for Soil Washing Technologies
The effectiveness of soil washing treatment technologies could be compromised and
undue cross-media contamination may be caused under certain conditions identified in
this subsection. Some soils, especially those that are rich in clays or contain high
concentrations of mineralized metals or hydrophobic organics, require very large amounts
of additives to achieve acceptable remediation endpoints. Additionally, complex
mixtures of contaminants in the soil may make it difficult to formulate a single suitable
washing fluid that will remove all the different contaminant types. In such cases,
multiple cleaning fluids may need to be used, and therefore multiple types of residuals
will be generated.
When soil washing is used to remediate contaminated soil, one should consider the
potential for the generation of large amounts of hazardous wastes that must be treated or
disposed of (sometimes at a great cost) when this technology is used in less than ideal
situations. In such cases, even when best management practices are applied, the
significant volumes of hazardous wastes that are generated and the reduced efficiency
with which the overall system is operating can increase the risk of accident or
mismanagement, which can in turn increase the risk of cross-media contamination.
However, some of these limitations could possibly be overcome with various
technology specific modifications and variations, and some of these limitations could
possibly be overcome by coupling with other processes (such as further separation of
fines, using special solvents, etc.), but may involve higher cost. The following few
characteristics have been identified that could impede the soil washing treatment
process and may result in cross-media transfer of contaminants.
>• Soils with high silt and clay content (>50% clay and silt) may be
problematic due to the difficulty of removing contamination from very fine
particles (Lear, 1996, and USEPA, 1993a).
>• Soils contaminated with a high concentration of mineralized metals or
hydrophobic organics (USEPA, 1993a).
>• Complex mixtures of contaminants make it difficult to formulate a suitable
washing fluid that will remove all the different contaminant types, and
possibly be cost prohibitive. Sometimes a single contaminant/compound
could also become strongly bound and difficult to remove (USEPA, 1993a).
51
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>• Generally not designed for highly explosive materials.
5.6 References
1. Lear, Paul R. 1996. OHM Remediation Services Corp. Comments on Draft BMP
Document. Personal Communication with Subijoy Dutta, May.
2. U.S. Department of Energy (DOE). 1995. Draft No Migration Variance Petition,
Waste Isolation Pilot Plant, DOE/CAO-95-2043, Carlsbad Area Office, Carlsbad, NM,
May.
3. Freeman, Harry M. and Eugene F. Harris. 1995. Hazardous Waste Remediation:
Innovative Treatment Technologies, Technomic Publishing Co., Inc., Lancaster,
PA.
4. USEPA. 1994a. BMP Development Workshop Summary-Soil Washing and Thermal
Treatment, Office of Solid Waste, Permits and State Programs Division, August.
5. USEPA. 1994b. Engineering Bulletin-Solvent Extraction, EPA/540/S-94/503,
Office of Research and Development, Cincinnati, April.
6. USEPA. 1993a. William C. Anderson, ed. Innovative Site Remediation Technology,
Soil Washing/Soil Flushing, Volume 3, EPA 542/B-93/012, Office of Solid Waste and
Emergency Response.
7. USEPA. 1993b. Proposed Best Demonstrated Available Technology (BOAT) Background
Document for Hazardous Soil, Office of Solid Waste, Waste Management Division,
August.
8. USEPA. 1993c. Approaches for the Remediation of Federal Facility Sites
Contaminated with Explosive or Radioactive Wastes, EPA/625/R-93/013, Office of
Research and Development, Washington, DC, September.
9. USEPA. 1992a. A Citizen's Guide to Soil Washing-Technology Fact Sheet,
EPA/542/F-92/003, Office of Solid Waste and Emergency Response, Technology
Innovation Office.
10. USEPA. 1992b. Seminar Publication-Organic Air Emissions from Waste Management
Facilities, EPA/625/R-92/003, Office of Research and Development, Washington,
DC, August.
11. USEPA. 199 la. Guide for Conducting Treatability Studies Under CERCLA: Soil
Washing, Interim Guidance (and Quick Reference Fact Sheet), EPA/540/2-91/020A and
B, Office of Emergency and Remedial Response, September.
12. USEPA. 199Ib. Innovative Treatment Technologies-Overview and Guide to
Information Sources, EPA/540/9-91/002, Office of Solid Waste and Emergency
Response, Washington, DC, October.
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13. USEPA. 1990a. Engineering Bulletin-Solvent Extraction Treatment, EPA/540/2-
90/013, Office of Research and Development, Cincinnati, September.
14. USEPA. 1990b. Engineering Bulletin-Soil Washing Treatment, EPA/540/2-90/017,
Office of Research and Development, September.
15. USEPA. 1989. Overview: Soils Washing Technologies for CERCLA, RCRA, and Leaking
UST Site Remediation, Risk Reduction Engineering Laboratory, Edison, NJ, June.
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6.0 Chapter Six: BMPs for THERMAL TREATMENT
This chapter focuses on the generally accepted best management practices (BMPs) to
minimize cross-media transfer of contaminants during remedial actions or corrective
measure implementations when using thermal treatments to treat soils or solid media.
BMPs are meant only to provide guidance and general recommendations on the operational
practices of selected technologies. BMPs are not meant to direct or dictate the selection
of appropriate technologies.
6.1 Definition and Scope of Thermal Treatment (for BMPs)
Thermal treatment processes employ indirect or direct heat exchanges to
desorb, vaporize, or separate volatile or semi-volatile organicsfrom soils or any
solid media while largely avoiding combustion (destruction) of these contaminants in
the primary unit. Gases or vapors from the thermal process are treated, destroyed or
condensed for reuse. (USEPA, 1993aand 1994c)
Many types of thermal treatment technologies are currently being used for the
treatment of soils and solid media. Considering their similarity in cross-media transfer
potentials, the following treatment technologies are listed as a few examples of thermal
treatment (for BMPs):
• Thermal Desorption • Low Temperature Thermal Aeration
• Catalytic Oxidation • Anaerobic Thermal (ATP)
• Thermal Bonding • Rotary Desorbers
• Molten Salt Oxidation • Heated Conveyors
• LT3 System • Anaerobic Pyrolysis
Two technologies included in this group ~ molten salt oxidation and anaerobic
pyrolysis ~ differ slightly from the others, but have been included here because they
resemble these technologies more than any others addressed in this guidance. However,
unlike the other technologies in this group, molten salt oxidation and anaerobic
pyrolysis destroy at least some portion of the contaminants present in the soil or solid
media.
The scope of BMPs for thermal treatment is not limited to the above listed
technologies. Any treatment technology that meets the key features of thermal treatment
should generally be considered as thermal treatment for the purpose of BMPs. BMPs for
incineration technologies are addressed separately under Chapter 9 of this document.
A typical schematic of a thermal desorption system is shown in Figure 6-1.
6.1.1 Key Features of Thermal Treatment for the Purpose of BMPs
• External application of heat to raise the operating temperature is
the unique feature of the thermal treatment category for the purpose
of BMPs.
54
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Pre-
treatment
Most thermal treatments call for operating temperatures that are
significantly above ambient temperature and exceed the boiling
point of water, i.e., 212T.
Most thermal treatments under this category are generally designed
to remove contaminants from the soil matrix.
These treatment technologies are generally designed to be non-
destructive. But the high operating temperatures used in some
thermal treatment systems will result in localized oxidation or
pyrolysis (USEPA, 1994c).
The desorption, vaporization, or separation of different
contaminants from the soil matrix varies with the type of
contaminants. These variations depend significantly on the type of
contaminant and the selected operating temperature.
The residence time, operating temperature, and the expanse of
mixing/agitating the contaminated soil matrix or solid media are
generally the prime operating factors in thermal treatment.
a. Direct-fired rotary
desorber
b. Indirect-fired rotary
desorber
c. Conveyor
d. Others
a. Organic collection/
destruction
b. Paniculate collection
c. Acid gas removal
Thermal
Desorber
Gas Post-
treatment
a. Excavation
b. Storage
c. Sizing
d. Crushing, dewatering,
neutralization
e. Blending
f. Feeding systems
Solid Post-
treatment
a. Discharge material
handling system
b. Cooling
c. Dust control
d. Stabilization
Figure 6-1. Schematic of a Thermal Desorption Treatment System (USEPA, 1993a)
55
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6.2 Thermal Treatment Technology Description
Thermal desorption is considered the most general and representative form of
thermal treatment for the purposes of this chapter; therefore, a description of thermal
desorption is provided here.
In thermal desorption, contaminated material is excavated and delivered to the
desorption unit. Excavated material is often stockpiled to provide an adequate feed
supply for continuous operation of the treatment facility. Typically, before any
treatment, large objects are screened from the medium and rejected. Rejected material
can sometimes be sized and recycled to the desorber feed. The medium may then be treated
to adjust pH and moisture content. The medium is then delivered by gravity to the desorber
inlet or conveyed by augers to a feed hopper from which it is mechanically conveyed to the
desorber. In the desorption unit, the contaminated material is heated, and water and
contaminants are volatilized. An inert gas may be injected as a sweep stream. Organics in
the off-gas may be collected and recovered by condensation and adsorption, or burned in an
afterburner (USEPA, 1993a).
To increase the effectiveness of thermal desorption technology, extensive pre-
processing/pre-treatment of the inlet soil may be conducted. This pre-processing may
include removing rocks and debris from the waste matrix, mixing the waste to create a more
homogeneous feed, and screening and crushing the waste matrix to achieve a smaller
particle size. During pre-processing, air emission monitoring must be conducted to
control fugitive emissions (USEPA, 1990).
Operation of thermal desorption systems can create a number of process residual
streams that may need to be managed: treated media; untreated, oversized rejects;
condensed contaminants and water; particulate control-system dust; clean off-gas; and
spent carbon or other media, if used (USEPA, 1993a).
6.3 Cross-Media Transfer Potential of Thermal Treatment Technologies
(a) General
Environmental impacts associated with all thermal desorbers, aside from process
emissions,
are attributable to excavation of contaminated solids, management of treated solids, and
equipment noise (USEPA, 1993a).
General cross-media transfer potentials during site preparation, pre-treatment,
and post-treatment activities have been addressed in Chapter 2.
(b) Additional Concerns for Thermal Treatment Technologies
• During various thermal treatment operations, SVOC/VOC emissions
can occur from leaks in pipes, joints, valves, and uncovered
conveyor systems.
56
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• Stack emissions from the collection or destruction of vapors past
the thermal desorption, vaporization, or separation treatment unit
can release contaminants into the air at levels above the regulatory
limit.
• The discharge of scrubber liquor and blowdown can release
contaminants to air, water, or soils.
• Waste handling can contribute significantly to VOC emissions during
remediation of soils or solid media with thermal treatments.
• Inadequate control and management of baghouse dust containing ash,
metals, and/or unoxidized compounds may also cause contaminants to
be released into the environment.
• When using any thermal treatment for remediation of explosive
wastes, there is potential for possible explosion or detonation of
the waste during the treatment process.
• When radioactive/mixed wastes are remediated by thermal treatment,
the radionuclides are generally retained or bonded and rendered
unleachable for safe disposal of the solid residuals (e.g., ash) in
landfills. Potential for radioactive emission from the treated mass
may still exist.
• Fugitive emissions from fuel sources can sometimes add to the
overall emissions of organics from the site.
• In cases where organic wastes are extracted or concentrated using a
thermal treatment technology (i.e., rather than destroyed) the VOC
emissions from these wastes can significantly increase the need for
control of VOCs from the overall process.
• During remediation of chlorinated organics using the Anaerobic
Thermal Processor or any other thermal treatment, the potential
exists for the creation of dioxin or dibenzo-furans emissions at low
concentrations. Fugitive VOC emissions from the vapor cooling
system are also possible (USEPA, 1993a).
6.4 Best Management Options to Avoid Potential Cross-Media Transfers for Thermal
Treatment Technologies
General BMPs to prevent potential cross-media transfer of contaminants during
cleanup activities have been addressed in Chapter 2. Also, proper system design is
recommended prior to implementation of the remedial treatment to avoid cross-media
transfer problems during different treatment steps. However, BMP options to control
specific cross-media transfer of contaminants for thermal treatments are furnished
below.
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During the thermal treatment process the following activities are most commonly
undertaken:
4 Application of heat in a heat exchanger unit; rotational or other mixing
action; movement of the contaminated media through a conveyor system;
vaporization, desorption, separation, or permanent
bonding/solidification of contaminants.
To prevent cross-media transfer of contaminants the following BMPs are
recommended, where appropriate:
/ Fuel storage and fuel handling areas may be added under monitoring and
emission control oversight if deemed necessary.
/ Routine inspections of pipes, valves and fittings should be performed where
fuel or pressurized liquids are involved.
/ During the main treatment activities as specified above, organic or
inorganic vapor emissions should be monitored and appropriate emission
control measures, described in Chapter 3 of this document, should be used to
prevent emissions above the allowable level specified by the regulatory
agency (EPA or authorized state).
/ Technology design should take corrosion into account and incorporate
corrosion resistant surfaces for all appropriate pipes, valves, fittings,
tanks, and feed systems. It is important that the air pollution control
devices are designed for the corrosive nature of the hot gases expected to
enter them. Operational plans should include adequate inspection
procedures that look specifically for corrosion and wear.
/ Operation of thermal desorption systems may create up to six process
residual waste streams: treated soil; oversized soil and debris rejects;
condensed contaminants and water; spent aqueous and vapor phase activated
carbon; and clean off-gas. The following BMPs can be used to control the
potential cross-media transfer of residuals:
— Treated medium, debris, and oversized rejects may be suitable for
reuse onsite. If not, they should be properly stored or
containerized until they can be treated and disposed of.
— The vaporized organic contaminants can be captured by condensation
of the off-gas passing through a carbon absorption bed or other
treatment system.
— Liquid collection tanks and secondary containment should be
incorporated into the operational plans. Plans should also be made
for subsequent treatment of these concentrated liquids in
appropriately regulated units.
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— Aqueous wastes from scrubber liquors and blowdown could be
effectively managed and controlled using a variety of wastewater
treatment technologies. See USEPA, 1987, 1986, and 1984 for
information on wastewater treatment technologies. Technology
operational plans should incorporate discussions of how movement of
these liquids will be adequately controlled.
— Off-gas condensate may contain significant contamination and may
require further treatment (i.e., carbon absorption). If the
condensed water is relatively clean, it may be used to suppress the
dust from the treated medium.
— Spent granulated carbon should either be returned to the supplier
for reactivation or incineration or regenerated onsite.
/ System monitoring and evaluation should be performed, as appropriate, to
determine possible emissions or migration of contaminants during treatment
activities.
6.5 Waste Characteristics that May Increase the Likelihood of Cross-Media
Contamination for Thermal Treatment Technologies
Under the following conditions the effectiveness of thermal treatment
technologies (as categorized for the purpose of BMPs) could be compromised, and could
cause undue cross-media contamination. However, some of these limitations could
possibly be overcome with various technology specific modifications and variations.
>• The contaminant concentration exceeding 10% to 25% of its lower explosive
limit (USEPA, 1994a).
>• Corrosion in containers and equipment due to low (< 5 Standard Unit (SU)) or
high (>11 SU) pH may pose problems (USEPA, 1994c).
>• Particles greater than 2 inches in diameter may call for separate treatment
or disposal due to size limitations for most equipment used for thermal
treatment systems (USEPA, 1994c).
*• Very high moisture content (>50%) generally makes most thermal treatments
highly cost intensive, and might increase the potential for cross-media
release of contaminants through the vapor phase (USEPA, 1994c).
>• Soils mixed with tars and organic materials greater than 10% by volume or
weight may cause handling problems and thus may require use of a reactor or
other equipment to process wastes, which could result in uncontrolled
releases due to corrosion (USEPA, 1994c).
6.6 References
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1. USEPA. 1995. In Situ Remediation Technology Status Report: Thermal
Enhancements, EPA/542/K-94/009, Office of Solid Waste and Emergency Response.
2. USEPA. 1994a. BMP Development Workshop Summary for Soil Washing and Thermal
Treatment, Office of Solid Waste, Permits and State Programs Division, August.
3. USEPA. 1994b. William C. Anderson, ed. Innovative Site Remediation Technology,
Thermal Destruction, Volume 7, EPA 542/B-94/003, Office of Solid Waste and
Emergency Response.
4. USEPA. 1994c. Engineering Bulletin-Thermal Desorption Treatment, EPA/540/S-
94/501, Office of Research and Development, Cincinnati, February.
5. Air & Waste Management Association (AWMA). 1993. Thermal II Changing Molecular &
Physical Status, AWMA Live Satellite Seminar.
6. USEPA. 1993a. William C. Anderson, ed. Innovative Site Remediation Technology,
Thermal Desorption, Volume 6, EPA/542/B-93/011, Office of Solid Waste and
Emergency Response.
7. USEPA. 1993b. Approaches for the Remediation of Federal Facility Sites
Contaminated with Explosive or Radioactive Wastes, EPA/625/R-93/013, Office of
Research and Development, Washington, DC, September.
8. USEPA. 1993c. Proposed Best Demonstrated Available Technology (BOAT) Background
Document for Hazardous Soil, Office of Solid Waste, Waste Management Division,
August.
9. USEPA. 1992a. Guide for Conducting Treatability Studies Under CERCLA: Thermal
Desorption Remedy Selection, Interim Guidance (and Quick Reference Fact Sheet),
EPA/540/R-92/074A and B, Office of Solid Waste and Emergency Response, September.
10. USEPA. 1992b. A Citizen's Guide to Thermal Desorption-Technology Fact Sheet,
EPA/542/F-92/006, Office of Solid Waste and Emergency Response, Technology
Innovation Office.
11. USEPA. 199 la. Innovative Treatment Technologies-Overview and Guide to
Information Sources, EPA/540/9-91/002, Office of Solid Waste and Emergency
Response, October.
12. USEPA. 199Ib. Engineering Bulletin-Thermal Desorption Treatment, EPA/540/2-
91/008, Office of Research and Development, Cincinnati, May.
13. USEPA. 1990. Handbook on In Situ Treatment of Hazardous Waste-Contaminated
Soils, USEPA/540/2-90/002.
14. USEPA. 1988. Technology Screening Guide for Treatment of CERCLA Soils and
Sludges, EPA/540/2-88/004.
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15. USEPA. 1987. Dewatering Municipal Wastewater Sludges Manual, EPA/625/1-87/014,
Office of Research and Development, Cincinnati, September.
16. USEPA. 1986. Municipal Wastewater Disinfection Manual, EPA/625/1-86/021, Office
of Research and Development, October.
17. USEPA. 1984. Onsite Wastewater Treatment and Disposal Systems Manual,
EPA/625/01-80/012, Office of Research and Development, October.
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7.0 Chapter Seven: BMPs for VAPOR EXTRACTION
This chapter focuses on the generally accepted best management practices (BMPs) to
minimize cross-media transfer of contaminants during remedial actions or corrective
measure implementations when using vapor extraction technologies to treat soils or solid
media. BMPs are meant only to provide guidance and general recommendations on the
operational practices of selected technologies. BMPs are not meant to direct or dictate
the selection of appropriate technologies.
7.1 Definition and Scope of Vapor Extraction (for BMPs)
Vapor extraction involves use of vacuum pumps or blowers to produce a negative
pressure gradient, which induces airflow through the waste matrix and causes movement
of vapors containing volatile organic compounds (VOCs) towards extraction wells.
VOCs in the pore spaces of soils or solid media are thereby removed and carried above
ground through screened extraction wells. Extracted vapors are treated, as
necessary, and discharged to the atmosphere or reinjected to the subsurface (where
permissible). (USEPA, 1995aand 1991d).
Because of their similarity in cross-media transfer potentials the following
treatment technologies are listed as a few examples of vapor extraction technologies (for
BMPs):
• Soil Vapor Extraction (SVE) • Soil Venting
• Fracture Enhanced Vapor • Bioventing (also in Chapter
Extraction 8.0, Bioremediation)
• Thermal Enhancements of SVE • Air Sparging
• Steam Injection • Multi-Phase or Dual-Phase
• Hot Air Injection Extraction
• In Situ Steam Stripping
The scope of BMPs for vapor extraction is not limited to the above listed
technologies. Any treatment technology that satisfies the key features of vapor
extraction could be considered as vapor extraction for the purpose of BMPs.
Many of the above listed technologies are used in conjunction with vapor
extraction or groundwater technologies, or may be used to remediate VOCs in saturated
soils or groundwater. BMPs for bioventing systems are additionally addressed under
Chapter 8 (BMPs for Bioremediation) of this document.
A typical schematic of a vapor extraction system is shown in Figure 7-1.
7.1.1 Key Features of Vapor Extraction Technology for the Purpose of BMPs
• With respect to vadose zone soils, vapor extraction relies on the
ability to produce an advective air flow field throughout the
contaminated soils.
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The vacuum gradient created induces air flow through vadose zone
soils to volatilize contaminants.
Transfers contaminants from soil to air. Vapor treatment following
vapor extraction from the subsurface may be required to minimize
discharge of contaminants to the atmosphere; however, it may not be
required in all cases.
Generally does not destroy contaminants; extracts contaminant
vapors for collection and/or treatment.
Effectively reduces concentrations of volatile organic compounds
(VOCs) and certain biodegradable semi-volatile organic compounds
(SVOCs). Less volatile contaminants may be removed by bioventing.
Heat (hot air or steam) may be applied to increase the volatility of
less volatile compounds (USEPA, 1995a).
Generally, vapor extraction is an in situ technique (excluding
above-ground vapor and water treatment). It is primarily designed
for use in the vadose zone, although the saturated zone can be
dewatered and treated or treated with air sparging combined with
vacuum extraction.
Vapor extraction can be used ex situ for the remediation of
aboveground soil piles. For this application, perforated pipes are
located within the aboveground soil piles and connected to a blower
to draw air through the piles (USEPA, 1995a).
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• SECONDARY
% EMISSIONS
WATER COOLED
HEAT EXCHANGER
PRESSURE
GAUGE
PRESSURE
RELEASE
VALVE
IMPERMEABLE
SURFACE SEAL
SAND
PACK
TO WATER
TREATMENTSYSTEM
Figure 7-1. Schematic of a Soil Vapor Extraction System (USEPA, 1991d)
64
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7.2 Vapor Extraction Technology Description
Vapor extraction processes couple vapor extraction wells with blowers or vacuum
pumps to create an air-flow field in soil zones permeable to vapor flow. Contaminants
volatilized within the air-flow field, are swept into the vapor extraction well and are
removed from the soil. Vapor treatment systems, such as catalytic or thermal destruction
systems, activated carbon adsorbers, or biological gas treatment systems may be employed
to treat the extracted contaminated air stream (USEPA, 1995a).
Variants of vapor extraction, such as air sparging and thermally enhanced SVE,
have been developed to extend the application of vapor extraction technology. Air
sparging extends the application of vapor extraction to water-saturated soils by
injecting air under pressure below the water table. Thermally enhanced SVE combines
conventional vapor extraction equipment with a means to elevate the subsurface
temperature for increasing the volatilization potential of the soil contaminants
(USEPA, 1995a).
One advantage of vapor extraction systems is that they generally do not require
addition of reagents that must be delivered to and subsequently recovered from the
contaminated area (USEPA, 1990).
7.3 Cross-Media Transfer Potential of Vapor Extraction Technologies
(a) General
General cross-media transfer potentials during site preparation, pre-treatment,
and post-treatment activities have been addressed in Chapter 2.
(b) Additional Concerns for Vapor Extraction Technologies
• Fugitive vapor emissions through surface soils during operation,
especially when injection (air or steam) and fracturing
technologies are applied.
• Operation of vapor extraction systems may result in the contaminated
soil moisture becoming condensed and entrained with the system
and/or cause the uptake of contaminated groundwater.
• Surface water can intrude or channel into the contaminated vadose
zone altering the anticipated flow of vapors and groundwater.
• Undesirable migration of subsurface contaminant vapors or liquids
into the soil due to improper design or operation. For instance,
improper design of a vapor extraction system can cause unwanted
migration of contaminants from source areas to virgin soils;
improper design of an air sparging system can cause unwanted
migration of dissolved phase and vapor phase contaminants to outside
the remediation area.
65
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• During vapor extraction system operation there is potential for VOC
emissions through pipes, joints, and valves on the
delivery/discharge side of the vacuum pump.
• Inadequate design and operation of emission control equipment may
also cause transfer of contaminants to the natural environment.
• Residual contamination in the soil after system operation or beyond
the effective zone of influence of the extraction wells can act as a
continuing source of contamination to groundwater or air.
• Location and design of extraction and injection wells are critical
to ensuring uniform distribution of subsurface air flow and that
"dead" zones do not exist within the treatment area.
• With respect to injection techniques, underground sewer and utility
conduits can cause short-circuiting of subsurface air flow, and may
result in uncontrollable VOC discharges.
• Incomplete cleanup due to low permeability soil strata or units can
occur. Subsurface air flow will follow the path of least resistance;
therefore, channeling through more permeable soil zones (e.g.,
around natural gravel lenses or fill materials around buildings or
utility lines) can result in a partially or wholly ineffective
system. Low permeability areas can have high residual contaminant
concentrations while vapor extraction off-gases indicate cleanup is
complete.
7.4 Best Management Options to Avoid Potential Cross-Media Transfers for Vapor
Extraction Technologies
General BMPs to prevent potential cross-media transfer of contaminants during
cleanup activities have been addressed in Chapter 2. However, BMP options to control
specific cross-media transfer of contaminants for vapor extraction technologies are
addressed as follows:
Additional Site Preparation and Staging BMPs:
/ Site investigation and operational plans should identify the presence of
preferential subsurface air flow pathways and account for all existing
underground utilities (e.g., sewers, electrical conduits).
/ Design and location of extraction and injection wells are critical to
ensuring proper distribution of subsurface air flow and that "dead" zones
do not exist within the remediation area.
/ Depth to the ground water table should be identified. Ground water
monitoring wells should be installed to determine presence of LNAPL free
product and its recovery strategies. The SVE system design should consider
66
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the presence of free product, and the potential applicability of air
sparging for combined vadose zone and saturated zone remediation.
/ Extraction wells should not be located near surface water impoundments,
underground storm sewers, or drains.
Additional Pre-Treatment Activities: During SVE system construction, including
the installation of wells and/or, horizontal extraction/injection trenches, the
following activities are most commonly undertaken:
4 Trench excavation, well drilling, cuttings storage/treatment, drilling
mud control and dewatering, air/dust control for dry-air drilling, surface
protection for contaminated media.
The following BMP should be used to address these concerns:
/ During dry-air drilling of contaminated soils, VOC emissions should be
monitored and appropriate emission control measures should be used. For
example, the drilling could be configured so that auger cutting can be
directed through a large-diameter flexible pipe into bins. (See Chapter 3
for details on other emission control measures that can applied during
drilling activities.)
Vapor Extraction Treatment Activities: Prior to SVE system operation, the
following activities are generally recommended for better and leak-free operation of the
system:
/ The number and orientation of extraction wells should be determined.
/ Configuration of injection wells should be determined.
/ Permeability and fracturing options should be evaluated.
/ Wells should be anchored.
/ Surface seals should be installed when there is potential for uncontrolled
emissions.
/ The system should be checked for leaks after completion of construction.
/ When VOC emissions or leaks are detected from wellheads, wellhead boxes
should be installed using self-sealing neoprene rubber packers to form an
effective seal between the casing and upper end of the well screen for
wellhead protection.
/ Any emissions or discharge from the treatment process should be monitored,
and control equipment such as granulated activated carbon, air stripping,
and/or biofiltration to treat contaminated water and vapor should be
installed, if necessary. See Table 3-3 for technologies that can be used to
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control air emissions. Emission control equipment should be operated in
conformance with the allowable levels specified by the regulatory
authority (EPA or authorized state).
/ Local dewatering should be implemented in areas of open impoundments to
control water table and to enhance vadose zone air flow.
/ Pumping systems should be installed, if necessary, for controlling ground
water table.
/ When collecting entrained liquids from vapor extraction technology
systems, these liquids should generally be collected in a tank or a
lined/contained system. This will prevent the contaminants within the
liquids from mixing with the normal surface water runoff from the area, the
surrounding natural watercourse, and surrounding soil. These contaminated
aqueous streams should be treated or disposed of in accordance with the
applicable regulations.
/ Performance monitoring and evaluation should be conducted, including
general system integrity, changes in ground water table, and rate of VOC
reduction.
/ Proper safety and care should be exercised to prevent any explosion during
the recovery and treatment of any light non-aqueous phase liquids (LNAPLs)
generated as a free product. When inlet concentrations of the SVE system
exceed 10% of the lower explosion limit (LEL) of the LNAPL (NIOSH, 1990),
safety measures such as remote operation of the system, temporary shutdown,
or intermittent pumping as specified in USEPA, 1993 should be considered.
Post-Operation Activities: After the extraction wellhead vapor monitoring data
reach asymptotic VOC concentrations, soils within the radius of influence of the drawn
vacuum may not still be remediated to the cleanup goal. Thus post-treatment monitoring
will be crucial to ensure the control of soil vapor generated from passive venting.
The waste streams generated by in situ SVE are vapor, treatment residuals (e.g.,
spent activated carbon), contaminated ground water, and soil tailings from drilling the
wells. BMPs for these waste streams are as follows:
/ One option for the vapor stream control/treatment unit is to use a
biofiltration process for VOC removal.
/ Contaminated GAC should be carefully removed from the adsorption unit and
handled, stored, and disposed of or recycled in accordance with
manufacturer's recommendations and appropriate state or federal
regulations.
/ Contaminated ground water, if extracted along with vapor, may be treated
and discharged on site, if allowed, or collected and treated offsite.
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/ Proper decommissioning of extraction, injection, and/or monitoring wells
should be conducted to prevent any future cross-media transfer of
contaminants after the termination of SVE system operation in accordance
with state and local regulations.
7.5 Waste Characteristics that May Increase the Likelihood of Cross-Media
Contamination for Vapor Extraction Technologies
The effectiveness of vapor extraction technologies could be compromised, and
undue cross-media contamination may be caused, under certain conditions identified in
this subsection. However, some of these limitations could possibly be overcome by
technology specific modifications, such as fracturing clay layers to increase air
permeability, injecting hot air to enhance volatility. However, these modifications
would likely increase the design, installation, operation and monitoring costs of the
system. Please refer to technology-specific references provided at the end of this
chapter for additional information about modifications or variations that can be used to
enhance the effectiveness of a vapor extraction technology.
* Low permeability soils (i.e., K < 10~5 cm/sec) (USEPA, 1995a).
>• The presence of constituents that are not volatile or semi-volatile.
>• Sites containing high percentage of silty clay soils and requiring very low
soil clean-up levels within a short time period.
>• Saturated zone soils may be problematic. Air sparging or multi-phase (dual
phase) extraction may be considered to treat saturated zone soils and
groundwater.
»• Commingled waste may have detrimental effects on the treatment of the vapor
(e.g., mercury vapor will significantly affect treatment process used on
the vapor emission control).
7.6 References
1. USEPA. 1995a. Innovative Site Remediation Technology-Vacuum Vapor Extraction,
Volume 8, EPA 542/B-94/002, Office of Solid Waste and Emergency Response, April.
2. USEPA. 1995b. SITE Demonstration Bulletin, Subsurface Volatilization and
Ventilation System, Brown and Root Environmental, EPA/540/MR-94/529, RREL,
Cincinnati, January.
3. USEPA. 1995c. SITE Demonstration Bulletin, Unterdruck-Verdempfer-Brunnen
Technology (UVB) Vacuum Vaporizing Well, Roy F. Weston, Inc./IEG Technologies
Corporation, EPA/540/MR-95/500, RREL, Cincinnati, January.
4. USEPA. 1995d. Review of Mathematical Modeling for Evaluating Soil Vapor
Extraction Systems, EPA/540/R-95/513, Office of Research and Development,
Washington, DC, July.
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5. USEPA. 1995e. BMP Development Workshop Summary-Vapor Extraction, Office of Solid
Waste, Permits and State Programs Division, February.
6. USEPA. 1995f How to Evaluate Alternative Cleanup Technologies for Underground
Storage Tank Sites, EPA/510/B-95/007, Office of Solid Waste and Emergency
Response, May.
7. USEPA. 1994a. Soil Vapor Extraction (SVE) Treatment Technology Resource Guide.
EPA/542/B-94/007, Office of Solid Waste and Emergency Response, Technology
Innovation Office, Washington, DC.
8. USEPA. 1994b. Manual-Alternative Methods for Fluid Delivery and Recovery.
EPA/625/R-94/003, Office of Research and Development, Washington, DC, September.
9. USEPA. 1993. Approaches for the Remediation of Federal Facility Sites
Contaminated with Explosive or Radioactive Wastes, EPA/625/R-93/013, Office of
Research and Development, Washington, DC, September.
10. USEPA. 1992a. Conducting Field Tests for Evaluation of Soil Vacuum Extraction
Application, Office of Research and Development, Ada, OK, EPA/540/S-92/004.
11. USEPA. 1992b. A Citizen's Guide to Air Sparging. Technology Fact Sheet.
EPA/542/F-92/010, Office of Solid Waste and Emergency Response, Technology
Innovation Office.
12. USEPA. 1992c. Proceedings of the Symposium on Soil Venting, April 29-May 1, 1991,
Houston, Texas, EPA/600/R-92/174, Office of Research and Development,
Washington, DC, September.
13. USEPA. 199 la. Guide for Conducting Treatability Studies Under CERCLA: Soil Vapor
Extraction, Interim Guidance (and Quick Reference Fact Sheet), EPA/540/2-91/019A
and B, Office of Emergency and Remedial Response, September.
14. USEPA. 1991b. Engineering Bulletin-Air Stripping of Aqueous Solutions,
EPA/540/2-91/022, Office of Research and Development, Cincinnati, OH, October.
15. USEPA. 1991c. Engineering Bulletin-In Situ Soil Vapor Extraction Treatment,
EPA/540/2-91/006, Office of Emergency and Remedial Response, Washington, DC.
16. USEPA. 1991d. Reference Handbook-Soil Vapor Extraction Technology, EPA/540/2-
91/003, Office of Research and Development, Washington, DC, February.
17. USEPA. 1990. State of Technology Review-Soil Vapor Extraction Systems,
EPA/600/2-89/024, Hazardous Waste Engineering Research Laboratory, August.
18. National Institutes of Occupational Safety and Health (NIOSH). 1990. Pocket
Guide to Chemical Hazards, US Department of Health and Human Services, June.
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19. Johnson, P.C., M.W. Kemblowski, J.D. Colthart, D.L. Buyers, and C.C. Stanley.
1990. A Practical Approach to the Design, Operation, and Monitoring of In-Situ
Soil Venting Systems, Shell Development/Shell Oil Company, Spring.
20. Baehr, Arthur, George Hoag, and Michael Marley. 1988. Removing Volatile
Contaminants from the Unsaturated Zone by Inducing Advective Air-Phase Transport,
June 20.
21. USEPA. 1989a. Soil Vapor Extraction VOC Control Technology Assessment, EPA-
450/4-89/017, Office of Air Quality Planning and Standards, September.
22. USEPA. 1989b. Technology Evaluation Report: SITE Program Demonstration Test ~
Terra Vac In Situ Vacuum Extraction System, Groveland, Massachusetts, Volume 1,
EPA/540/5-89/003a, April.
23. USEPA. 1989c. Applications Analysis Report: Terra Vac In Situ Vacuum Extraction
System, EPA/540/A5-89/003, Office of Research and Development, July.
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8.0 Chapter Eight: BMPs for BIOREMEDIATION
This chapter focuses on the generally accepted best management practices (BMPs) to
minimize cross-media transfer of contaminants during remedial actions or corrective
measure implementations when using bioremediation technologies to treat soils or solid
media. BMPs are meant only to provide guidance and general recommendations on the
operational practices of selected technologies. BMPs are not meant to direct or dictate
the selection of appropriate technologies.
8.1 Definition and Scope of Bioremediation (for BMPs)
Bioremediation is a treatment technology that uses biode gradation of organic
contaminants through stimulation of indigenous microbial populations by providing
certain amendments, such as adding oxygen or limiting nutrients, or adding exotic
microbial species. It uses naturally occurring or externally-applied microorganisms
to degrade and transform hazardous organic constituents into compounds of reduced
toxicity and/or availability. Specific technologies fall into two broad categories:
(1) Ex situ technologies (e.g., slurry phase, land treatment, solid phase,
composting), and (2) In situ technologies (USEPA, 1991c). Active remediation can
include addition of such amendments as nutrients or oxygen and passive remediation
utilizes natural attenuation to adequately characterize, model and monitor the site
to evidence natural attenuation and protection of potential receptors.
Many different types of bioremediation technologies are currently being used for
soils treatment, and many more innovative approaches involving bioremediation are being
developed. Considering their similarity in cross-media transfer potentials, the
following treatment technologies and processes are listed as a few examples of
bioremediation (for the purpose of BMPs):
• Natural Attenuation • Bioremediation of Metals (Changing
• Biodegradation the Valence)
• Aerobic/Anaerobic • Binding of Metals
Biodegradation • Plant Root Uptake
• Biopiles (Phytoremediation)
• Composting • Fungi Inoculation Process
• Land Treatment • Slurry Phase Bioremediation
• Bioreactors • Solid Phase Bioremediation
• Bioscrubbers • Bioventing (addressed in Chapter.
• Dehalogenation 7, BMPs for Vapor Extraction)
• Methanotrophic Process • Bio Wall for Plume Decontamination
(In Situ)
The scope of BMPs for bioremediation technologies is not limited to the above
listed technologies. Any treatment technology that meet the key features of
bioremediation treatment, as described below, should generally be considered as
bioremediation treatments for the purpose of BMPs.
A typical schematic for solid phase bioremediation is shown on Figure 8-1.
72
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Schematic for Solid Phase Bioremediation
Sludga/Sadmnt.
Transfer PUMP
Excavation a
Mixing Contaminated
Soil
Dralnaga
V JCollaction
8ump
r-< Top»oll/Sub»ffn "„ " >
^^-^^*" *** >^< —- —
Front End
Prapiritlon Staps
Tntttd
Soil Stoekplla
Soure*: EPA/BOO/R-94/203
Figure 8-1. Schematic for Solid Phase Bioremediation (USEPA, 1995c)
-------
8.1.1 Key Features of Bioremediation for the Purpose of BMPs
• Most bioremediation soils treatment technologies generally destroy
contaminants in the soil matrix.
• Generally these treatment technologies are designed to reduce
toxicity either by destruction or by transforming toxic organic
compounds to less toxic compounds.
• Indigenous micro-organisms, including bacteria and fungi are most
commonly used. In some cases, wastes may be inoculated with specific
bacteria or fungi known to biodegrade the contaminants of concern.
Plants may also be used to enhance biodegradation and stabilize the
soil.
• May require the addition of nutrients or electron acceptors (such as
hydrogen peroxide or ozone) to enhance growth and reproduction of
indigenous organisms.
• Field applications of bioremediation may involve:
— Excavation
— Soil handling
— Storage of contaminated soil piles
— Mixing of contaminated soils
— Aeration of contaminated soils
— Injection of fluid
— Extraction of fluid
— Introduction of nutrients and substrates
Several of the above field applications may not necessarily be viewed separately
and may need to be used together.
8.2 Bioremediation Technology Description
Bioremediation involves the use of microorganisms to chemically degrade organic
contaminants. Aerobic processes use organisms that require oxygen to be able to degrade
contaminants. In some cases, additional nutrients such as nitrogen and phosphorous are
also needed to encourage the growth of biodegrading organisms. A biomass of organisms ~
which may include entrained constituents of the waste, partially degraded constituents,
and intermediate biodegradation products ~ is formed during the treatment process
(USEPA, 1990d).
Although bioremediation is applied in many different ways, descriptions of
typical solid-phase bioremediation, composting, bioventing, and traditional in situ
biodegradation are provided here. Solid-phase bioremediation treatment can be conducted
in lined land treatment units or in composting piles. A lined land treatment unit
consists of a prepared bed reactor with a leachate collection system and irrigation and
nutrient delivery systems. The unit also may contain air emission control equipment.
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Figure 8-1 illustrates treatment by solid phase bioremediation. The soil is placed on
land lined with an impervious layer, such as soil, clay, or a synthetic liner.
Solid-phase biological treatment of soil can also be performed in composting
piles. Figure 8-2 illustrates atypical composting treatment process, including a
compost pile, wood chip cover and base, ventilation pipes, and leachate collection
system. In composting, the soil is mixed with fertilizer, water, and a bulking agent such
as wood chips or sand, and placed in piles from 3 to 6 feet high (USATFIAMA, 1988). The
bulking agent helps to mix and aerate the material. Oxygen can be supplied to the pile by
introducing air (using a blower and series of pipes) below the pile, or by
turning/cultivating the pile. The addition of nutrients, such as manure or molasses, to
the soil mixture can increase exothermic biodegradation reaction rates and thereby
increase the operating temperature of the composting pile. The introduction of air can
also help to control the temperature of the system. The addition of bulking agents will
reduce the concentration of organic compounds in the soil; hence, the concentration of
organics in the untreated soil must be sufficiently high to initiate and maintain the
composting process.
The in situ biodegradation process is generally used in conjunction with ground
water pumping and soil flushing systems to circulate nutrients and oxygen through a
contaminated aquifer and associated soil (Freeman and Harris, 1995). The process usually
involves introducing aerated nutrient-enriched water into the contaminated zone through
a series of infiltration galleries and injection wells and recovering the water
downgradient. The recovered water can then be treated, if necessary, and reintroduced to
the soil on site, where allowed by applicable regulations. The in situ biodegradation
system may also include aboveground treatment and conditioning of the infiltration water
with nutrients and an oxygen (or other electron acceptor) source (USEPA, 1994d).
Bioventing uses relatively low-flow soil aeration techniques to enhance the
biodegradation of soils contaminated with organic contaminants. Although bioventing is
predominantly used to treat unsaturated soils, applications involving the remediation of
saturated soils and groundwater (augmented by air sparging) are becoming more common.
Generally a vacuum extraction, air injection, or combination of vacuum extraction and air
injection system is employed (Freeman and Harris, 1995). An air pump, one or more air
injection or vacuum extraction probes, and emissions monitors at the ground surface are
commonly used.
Ex situ processes also include landfarming, which involves spreading contaminated
soils over a large area. Bioremediation may also be conducted in a bioreactor, in which
contaminated soil or sludge is slurried with water in a mixing tank or lagoon.
Bioremediation systems require that the contaminated soil or sludge be sufficiently and
homogeneously mixed to ensure optimum contact with the seed organisms (USEPA, 1990d).
75
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WAIT
~\
HACHAH
•
•' Tt
\
OR OTf-ffrR
P
=f
K
Off
KPC
Figure 8-2. Diagram of Solid Phase Biological Treatment Using a Composting Pile
(USATHAMA, 1988)
8.3 Cross-Media Transfer Potential of Bioremediation Technologies
(a) General
General cross-media transfer potentials during site preparation, pre-treatment,
and post-treatment activities have been addressed in Chapter 2.
(b) Additional Concerns for Bioremediation Technologies
76
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• Release of VOCs to air or water can occur during sampling and
analysis conducted as part of the implementation of the
bioremediation treatment.
• Some in situ bioremediation processes may generate soil gas
emissions in excess of background levels.
• SVOC/VOC emissions may be released from leaks in pipes, joints,
valves, and uncovered conveyor systems used in some bioremediation
technology operations.
• Nutrients that are applied as a part of a bioremediation treatment,
such as landfarming, may be carried through run off to surface water
or leach to groundwater if the treatment is improperly designed
and/or implemented.
• Very high wind speeds may be of particular concern due to the
potential for emissions during active composting or other
operations where soils may not be covered or enclosed.
8.4 Best Management Options to Avoid Potential Cross-Media Transfers for
Bioremediation Technologies
General BMPs to prevent potential cross-media transfer of contaminants during
pre-treatment and post-treatment activities have been addressed in Chapter 2. Only
technology-specific treatment activities and possible BMP options to control cross-
media transfer of contaminants during these activities are furnished below.
During the bioremediation treatment process the following activities are most
commonly undertaken:
4 For ex situ bioremediation, excavation, storage, mixing, and other
preparatory steps are undertaken prior to feeding contaminated soil
stockpile to the bioreactor or treatment bed comprised of lined land
treatment units. In case of composting piles, the soil is mixed with
fertilizer, water, and a bulking agent, such as wood chips or sand, and
placed in piles from 3 to 6 feet high (USATHAMA, 1988). In some
bioremediation application nutrients and substrates are introduced into
the treatment bed. Drainage from the treatment bed is generally collected
in a sump area and recycled back to the treatment bed.
4 In the case of in situ bioremediation, electron acceptors (e.g., oxygen and
nitrate), nutrients, and other amendments may be introduced into the soil
and ground water to encourage the growth of indigenous microorganisms
capable of degrading the contaminants. The principal activities
surrounding in situ bioremediation involves: (a) boundary determination
of the treatment zone in both horizontal extent and depth, (b) injection of
nutrients and other amendments, and (c) periodic monitoring of
concentration levels of contaminant in the soil or solid media. Bioventing
77
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and other in situ biodegradation systems generally use infiltration
galleries or injection wells to deliver required amendments to the
subsurface.
The following BMPs may be used, when necessary and appropriate, to prevent cross-
media transfer of contaminants for the above activities:
/ Biotreatments occasionally produce unpleasant odors. Effective odor
control measures such as vapor collection systems, or other methods as
detailed in Chapter 3, should be used if necessary.
/ Surface treatment structures such as biopiles or compost piles should not
be constructed and maintained in areas that are prone to encounter high
winds. Wind can damage plastic or tarp covers, remove surface materials
such as straw or mulch that provide insulation and protection, and carry
dust and nutrients away from the treatment area, thereby causing cross-
media contamination. In addition, removal of surface protection increases
the likelihood of infiltration of rainfall, which increases the likelihood
of the production of leachate.
/ For technologies such as composting, landfarming, and other surface
treatments, runoff and leachate should be collected and tested regularly to
ensure that nutrient levels do not exceed regulatory standards for surface
water and ground water. In particular, nutrients such as phosphate and
nitrate may be of concern and may need to be monitored carefully throughout
the treatment process.
/ Any covers or liners that are used in surface treatment structures, such as
biopiles or compost piles, should be periodically examined to ensure that
they have not been torn or otherwise damaged. Any damaged covers or liners
should be repaired or replaced upon discovery.
8.5 Waste Characteristics that May Increase the Likelihood of Cross-Media
Contamination for Bioremediation Technologies
The effectiveness of bioremediation technologies could be compromised and undue
cross-media contamination may be caused under certain conditions identified in this
subsection. Please refer to technology-specific references provided at the end of this
chapter for additional information about modifications or variations that can be used to
enhance the effectiveness of a bioremediation technology.
»• All bioremediation applications are dependent upon site specific
conditions and the environment or matrix in which the contamination is
found. The environment and matrix situation should generally be analyzed
prior to choosing the treatment method. For example, some microbes need
specific properties in order to be effective (e.g., high tolerance for acid
conditions, saline conditions), and some compounds need to be treated under
certain conditions (e.g., aerobically, anaerobically).
78
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*• In situ bioremediation applications requiring circulation of fluids should
be avoided in case of tight clay or heterogeneous subsurface environments
where oxygen (or other electron acceptor) transfer limitations exist. This
limitation could possibly be overcome by modification of the site or
technology, but it would result in a more costly cleanup.
>• Because it generally requires some time to be effective, in situ
bioremediation should not be considered in the case of emergency
removal/remedy - "fast cleanup". However, ex situ treatment, e.g., in a
reactor, may be appropriate.
>• Concentration of the contaminant above the toxicity tolerance level of the
microorganisms (which varies with the bioavailability of the compound)
will make biodegradation ineffective.
>• Concentrations of contaminants required to sustain microbial population
may be above the regulatory limit. Conversely, sometimes the microbial
population cannot survive because of the concentrations of contaminants
being too low to sustain it. A treatment train or other alternatives should
be considered under these circumstances.
»• Technologies to treat some metals in heterogeneous mixtures, such as lead
and mercury, should be used very carefully (e.g., iron oxide, hexavalent
chromium, mercury).
Additional BMPsfor Residuals Management - Generally, there are few residuals to
treat with bioremediation technologies. The exception is the bioreactor, which may
generate carbon dioxide, water or other off-gases. Bioreactors should be designed with
monitoring equipment to ensure that off-gases do not produce air emissions at levels
higher than the state or federal regulatory limit.
/ Management of treated soils, sediments, and geological material:
Frequently bioremediation does not bring the concentration of individual
hazardous components in soil, subsurface material, or sediment to current
concentration-based standards. Depending on the bioavailability of those
individual hazardous components to the human population or plants and
wildlife, the hazard may or may not be controlled in the treated material.
Properly remediated geological material should not release or emit
hazardous constituents to soil, air or ground water in contact with the
remediated material. Nevertheless, as with any technology that is used to
treat hazardous wastes, engineering or institutional controls should be in
place to prevent direct contact with the treated material by the human
population or critical environmental receptors. If effective engineering
or institutional controls are not in place to prevent exposure, a risk
analysis of direct exposure should indicate that the level of risk is
acceptable.
8.6 References
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1. Freeman, Harry M. and Eugene F. Harris. 1995. Hazardous Waste Remediation:
Innovative Treatment Technologies, Technomic Publishing Co., Inc., Lancaster,
PA.
2. USEPA. 1995a. Innovative Site Remediation Technology-Bioremediation, Volume I,
EPA 542/B-94/006, Office of Solid Waste and Emergency Response, June.
3. USEPA. 1995b. In Situ Remediation Technology Status Report: Treatment Walls,
EPA/542/K-94/004, Office of Solid Waste and Emergency Response.
4. USEPA. 1995c. Contaminants and Remedial Options at Solvent-Contaminated Site,
EPA/600/R-94/203, Office of Research and Development.
5. USEPA. 1994a. Emerging Technology Bulletin, Institute of Gas Technology, Fluid
Extraction-Biological Degradation Process, EPA/540/F-94/501, March.
6. USEPA. 1994b. Engineering Bulletin-In Situ Biodegradation Treatment, EPA/540/S-
94/502, Office of Research and Development, Cincinnati, OH, April.
7. USEPA. 1994c. BMP Development Workshop Summary-Bioremediation, November.
8. USEPA. 1994d. Remediation Technologies Screening Matrix and Reference Guide,
EPA/542/B-94/013, October.
9. National Academy of Sciences. 1993. In Situ Bioremediation-When Does It Work?
National Academy Press.
10. USEPA. 1993a. Guide for Conducting Treatability Studies Under CERCLA,
Biodegradation Remedy Selection, Interim Guidance (and Quick Reference Fact
Sheet), EPA/540/R-93/519a and b, Office of Solid Waste and Emergency Response,
August.
11. USEPA. 1993b. Bioremediation Resource Guide, EPA/542/B-93/004, Office of Solid
Waste and Emergency Response, Technology Innovation Office, Washington, DC.
12. USEPA. 1992a. Seminar Publication: Organic Air Emissions from Waste Management
Facilities, EPA/625/R-92/003, Office of Air Quality Planning and Standards,
August.
13. USEPA. 1992b. Engineering Bulletin-Rotating Biological Contactors, EPA/540/S-
92/007, Office of Research and Development, Cincinnati, OH, October.
14. USEPA. 1992c. Engineering Bulletin-Slurry Walls. EPA/540/S-92/008, Office of
Research and Development, Cincinnati, OH, October.
15. USEPA. 1992d. A Citizen's Guide to Bioventing-Technology Fact Sheet, EPA/542/F-
92/008, Office of Solid Waste and Emergency Response, Technology Innovation
Office.
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16. USEPA. 1991a. Guide for Conducting Treatability Studies Under CERCLA: Aerobic
Biodegradation Remedy Screening-Interim Guidance, EPA/540/2-91/013A, Office of
Research and Development, Washington, DC.
17. USEPA. 199Ib. Guide for Conducting Treatability Studies Under CERCLA: Aerobic
Biodegradation Remedy Screening-Quick Reference Fact Sheet, EPA/540/2-91/013B,
Office of Emergency and Remedial Response, Hazardous Site Control Division.
18. USEPA. 1991c. Innovative Treatment Technologies: Overview and Guide to
Information Sources, EPA/540/9-91/002, Office of Solid Waste and Emergency
Response, October.
19. Fitter, Pavel and Jan Chudoba. 1990. Biodegradability of Organic Substances in
the Aquatic Environment, CRC Press.
20. USEPA. 1990a. Engineering Bulletin-Slurry Biodegradation. EPA/540/2-90/016.
Office of Research and Development, Cincinnati, OH, September.
21. USEPA. 1990b. Engineering Bulletin-In Situ Biodegradation Treatment, EPA/540/S-
94/502, Office of Research and Development, December.
22. USEPA. 1990c. Summary of Treatment Technology Effectiveness for Contaminated
Soil, EPA/540/2-89/053, Office of Emergency and Remedial Response, Washington,
DC.
23. USEPA. 1990d. Handbook on In Situ Treatment of Hazardous Waste - Contaminated
Soils, EPA/540/2-90/002, Office of Research and Development.
24. Ornston, L. Nicholas, Albert Balows, and Paul Baumann. 1988. Annual Review of
Microbiology, Volume 42, Annual Reviews, Inc.
25. Ross, Derek. 1988. Application of Biological Processes to the Clean Up of
Hazardous Wastes. Environmental Resources Limited.
26. U.S. Army Toxic and Hazardous Materials Agency (USATHAMA) (now U.S. Army
Environmental Center (USAEC)). 1988. Field Demonstration ~ Composting of
Explosives-Contaminated Sediment at the Louisiana Army Ammunition Plant (LAAP),
September.
27. USEPA. 1986. Microbial Decomposition of Chlorinated Aromatic Compounds.
EPA/600/2-86/090, Office of Research and Development, September.
28. Gibson, David T. 1984. Microbial Degradation of Organic Compounds, Marcel
Dekker, Inc.
29. Chakrabarty, A.M. 1982. Biodegradation and Detoxification of Environmental
Pollutants, CRC Press.
81
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30. Pramer, David and Richard Bartha. 1972. Preparation and Processing of Soil
Samples for Biodegradation Studies, Environmental Letters, 2(4), pp. 217-224.
82
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9.0 Chapter Nine: BMPs for INCINERATION TREATMENT
This chapter focuses on the generally accepted best operational management
practices (BMPs) to minimize cross-media transfer of contaminants during remedial
actions or corrective measure implementations when using incineration technologies to
treat soils or solid media. BMPs are meant only to provide guidance and general
recommendations on the operational practices of selected technologies. BMPs are not
meant to direct or dictate the selection of appropriate technologies.
9.1 Definition and Scope of Incineration Treatment (for BMPs)
Incineration, also known as controlled-flame combustion or calcination, is a
remedial technology that destroys organic constituents in soils, debris, or other
materials. An incinerator, as defined in 40 CFR 260.10, is any enclosed device that
uses controlled flame and neither meets the criteria for classification as a boiler,
sludge dryer, carbon regeneration unit, nor is listed as an industrial furnace; OR
meets the definition of infrared incinerator (electric resistance heater) or plasma
arc incinerator (electric arc). Various dictionaries and sources also define
incineration as burning, scorching, or carbonization. The American Society of
Mechanical Engineers (ASME) defines an incinerator as a device in which wastes are
burned (rapidly oxidized) at high temperatures, usually between 1600°F to 2500°F,
equivalent to 87l°C to 137TC (ASME, 1988).
The technologies included in this group are:
• Flame Oxidation
• Controlled Chamber
Combustion
• Catalytic Oxidation
• Plasma Arc and Infrared
Incineration
Liquid Injection Incinerators
Fixed/Open Hearth Incinerators
Rotary Kiln Incinerators
Fluidized Bed Incinerators
Gas or Fume Incinerator
A schematic diagram of atypical incineration facility is shown on Figure 9-1. A
typical liquid injection incinerator is shown on Figure 9-2. Details of a typical
fixed/sloped hearth incinerator are shown on Figure 9-3. Typical multiple hearth and
rotary kiln incinerators are shown in Figures 9-4 and 9-5, respectively.
83
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INCINERATOR
HEAT
RECOVERY
IONIZED
WET
SCRUBBER
QUENCH
STACK
DEMISTER
WASTE HEAT
BOILER
WASTE WATER TREATMENT
UNIT
DRUM
CLASSIFICATION
SLUDGE
DEWATERING
TANK FARM
WASTE PRETREATMENT
Figure 9-1. Schematic Diagram of a Typical Incineration Facility (ASME, 1988)
AIR & WATER
POLLUTION CONTROL
-------
00
Atomizing
Medium
(Air, Nitrogen,
Or Steam)
Supplemental
Fuel
If Required
Liquid
Waste
Storage
Tank
',V-- Combustion
'+*'---
------- chamber
t
n
Combustion
Air
To Air
Pollution
Control
Device
Figure 9-2. Typical Liquid Injection Incinerator (ASME, 1988)
-------
Charging
Door
oo
ON
Primary
Combustion
Chamber
Auxiliary
Burner
(ml
Secondary
Combustion
Chamber
Ashpit
Door
Auxiliary
Burner
Tertiary
Combustion
Chamber
J
I
To Air
Pollution
Control
Device
Figure 9-3. Typical Fixed/Sloped Hearth Incinerator (ASME, 1988)
-------
RETURN AIR
SOLID
WASTE FEED-
BUCKET ELEVATOR
d
FURNACE
HAULING
SCREW CONVEYOR
OWt
AFTERBURNER *,ND
xl
FUEL
BURNERS
(LIQUID AND
GASEOUS
WASTE)
COOLING AIR FOR RABBLE
ARMS AND DRIVE SHAFTS
Figure 9-4. Typical Multiple Hearth Incinerator (ASME, 1988)
87
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Solid &
Sludge
oo
oo
Secondary
Combustion
Chamber
Pumpable
Waste
Drums
Air Pollution
Control Device
Pumpable
Waste
1 Ash to
1 Landfill
Figure 9-5. Typical Rotary Kiln Incinerator (ASME, 1988)
-------
9.1.1 Key Features of Incineration for the Purpose of BMPs
• Used ex situ.
• Generally involves flame oxidation/burning.
• Uses closed chambers, not open burning.
• Produces stack gas emissions.
• Incineration technologies generally destroy contaminants in the
soil matrix at elevated temperatures.
• Reduces volumes of toxic compounds in soils.
• Reduce stoxicity of organics.
• Does not destroy most inorganic (e.g., metals) waste.
• The residence time, operating temperature, and the expanse of
mixing/agitating the contaminated soil matrix or solid media
(turbulence) are generally the prime operating factors in
incineration.
9.2 Incineration Technology Description
The incineration process may be viewed as consisting of four steps: (1)
preparation of the feed materials for placement in the incinerator, (2) incineration or
combustion of the material in a combustion chamber, (3) cleaning of the resultant air
stream by air pollution control devices that are suitable for the application at hand, and
(4) disposal of the residues from the application of the process (including ash and air
pollution control system residues) (USEPA, 1989).
Preparation/pre-processing of feed materials may include screening and mixing as
well as crushing to provide a consistent particle size and homogeneity more suitable for
treatment. Although extensive pre-processing will appear to increase capital and O&M
costs, these costs are offset by greater levels of efficiency (and lower downtime) with
which the system will subsequently operate (USEPA, 1989).
Incineration of soils generates large amounts of ash and residue. Ash
characteristics will depend on the type of thermal destruction process (USEPA, 1989).
9.3 Cross-Media Transfer Potential of Incineration Technologies
(a) General
General cross-media transfer potentials during pre-treatment and post-treatment
activities have been addressed in Chapter 2.
89
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(b) Additional Concerns for Incineration Technologies
Types of Potential Releases:
• Fugitive emissions from fuel sources can add to the overall
emissions of organics from the site.
• Incomplete combustion of organic compounds can generate "products
of incomplete combustion" (PICs) which can cause serious air
pollution.
• High combustion gas flow can cause problems in the gas cooling
device.
• Scrubber gases are often very acidic (when the combusted soils
contain high levels of chlorine or sulfur) and may cause corrosion
in the system components, which in turn may cause containers to
leak/fail, resulting in potential cross-media transfer of
contaminants.
• Potential metal emissions with dust or due to volatilization (e.g.,
mercury).
• Low pH of scrubber water could cause equipment damage and leaks.
• Unless effectively managed and controlled, scrubber
water/residuals from air pollution control devices also pose some
threat for release of contaminants to the air, water, or soils.
• Residuals (water) generated from waste conditioning prior to
incineration.
• There is potential for VOC emissions due to leaks in pipes, joints,
valves, uncovered conveyor systems.
• Stack emissions from organic destruction of vapors have potential
for release of contaminants in the air/natural environment above the
regulatory limit.
• Inadequate control and management of baghouse dust (including ash,
metals, and/or unoxidized compounds) may cause transfer of
contaminants to the environment.
• When the internal temperature and/or pressure of the combustion
chamber becomes too high, emergency vents are opened to allow some of
the superheated gases to escape. This may allow untreated air
containing volatiles, heavy metals, or other substances to be
released, creating the potential for cross-media contamination.
90
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9.4 Best Management Options to Avoid Potential Cross-Media Transfers for Incineration
Technologies
General BMPs to prevent potential cross-media transfer of contaminants during
pre-treatment and post-treatment activities have been addressed in Chapter 2. Only
technology specific treatment activities and possible BMP options to control specific
cross-media transfer of contaminants during these activities are furnished below.
During the incineration process the following activities are most commonly
undertaken:
4 The contaminated media is moved through a conveyor system to the
incineration chamber. Heat is applied in the chamber and the waste
subjected to flame oxidation/burning at a high temperature in a turbulent
environment for a period of time necessary to convert the waste into carbon
dioxide and water. Rotary or other type of mixing actions are generally
undertaken. Waste heat is supplied to the boiler which supports the air and
water pollution control units.
The following BMPs are generally recommended to be used, where appropriate, for
preventing cross-media transfer of contaminants for the above activities:
/ During the main treatment activities as specified above, organic or
inorganic vapor emissions should be monitored and appropriate emission
control measures, described in Chapter 3 of this document, should generally
be used to prevent emissions above the allowable level specified by the
regulatory agency (EPA or authorized state).
/ The fuel storage and fuel handling areas should be added under monitoring
and emission control oversight, if deemed necessary.
/ Pipes, valves and fittings where fuel or pressurized liquids are involved
should be checked regularly for leaks and general condition of joints.
/ Three major waste streams are generated by this technology: solids from the
incinerator and air emissions control system, water from the air emissions
control system, and emissions from the incinerator. The following BMPs
should be used to control the potential of cross-media contamination from
management of these residuals:
— Ash and treated soils or solids from the incinerator combustion
chamber, as well as solids from the air emissions control system,
such as fly ash or granulated activated carbon (GAC), may be
contaminated with heavy metals. These residues should be tested
with leachate toxicity tests. If they fail these tests, they should
be treated by a process such as stabilization/solidification (see
Chapter 10) and disposed of onsite or in an approved landfill
(Freeman and Harris, 1995).
91
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— Liquid waste from the air pollution emissions system may contain
caustics, high levels of chlorides, volatile metals, trace
organics, metal particulates, and inorganic particulates.
Treatment may require neutralization, chemical precipitation,
evaporation, filtration, or carbon adsorption before discharge
(Freeman and Harris, 1995).
9.5 Waste Characteristics that May Increase the Likelihood of Cross-Media
Contamination for Incineration Technologies
The effectiveness of incineration treatment technologies could be compromised and
undue cross-media contamination may be caused under certain conditions identified in
this subsection. However, some of these limitations could possibly be overcome with
various technology specific modifications and variations. Please refer to technology-
specific references provided at the end of this chapter for additional information about
modifications or variations that can be used to enhance the effectiveness of an
incineration technology.
>• Since incineration does not destroy most inorganic (metals) wastes, this
treatment technology may not be effective for waste media containing
metals.
*• May be very fuel-intensive for wastes with high moisture content.
>• Wastes having low organic content may be costly to incinerate.
>• Some explosive wastes may require a specially designed incinerator.
>• This technology will not be applicable to wastes requiring in situ
treatment.
>• Wastes with high debris/large particle content may be a problem for some
incinerators.
9.6 References
1. Freeman, Harry M. and Eugene F. Harris. 1995. Hazardous Waste Remediation:
Innovative Treatment Technologies, Technomic Publishing Co., Inc., Lancaster,
PA.
2. USEPA. 1995. BMP Development Workshop Summary-Incineration Technologies.
Summary of Workshop on Incineration Technologies. March.
3. Vickery, R. 1995. Personal Communication, Memo from Dupont Facilities Services,
Wilmington, Delaware, to Subijoy Dutta, October 13, 1995.
4. USEPA. 1994. Innovative Site Remediation Technology-Thermal Destruction, Volume
7, EPA/542/B-94/003, Office of Solid Waste and Emergency Response, October.
92
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5. USEPA. 1993. Approaches for the Remediation of Federal Facility Sites
Contaminated with Explosive or Radioactive Wastes, EPA/625/R-93/013, Office of
Research and Development, Washington, DC, September.
6. USEPA. 1990. Engineering Bulletin-Mobile/Transportable Incineration Treatment,
EPA/540/2-90/014, Office of Research and Development, Cincinnati, OH, September.
7. USEPA. 1989. Seminar Publication Corrective Action Technologies and
Applications, EPA/625/4-89/020, pages 41-47.
8. ASME. 1988. Hazardous Waste Incineration, A Resource Document, American Society
of Mechanical Engineers, New York, NY, January.
9. USEPA. 1988. Hazardous Waste Incineration: Questions and Answers, EPA/SW-88-
018, Office of Solid Waste, Washington, DC.
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10.0 Chapter Ten: BMPs for OTHER PHYSICAL/CHEMICAL TREATMENTS
This chapter focuses on the generally accepted best management practices (BMPs) to
minimize cross-media transfer of contaminants during remedial actions or corrective
measure implementations when using "other physical/chemical treatment technologies" to
treat soils or solid media. BMPs are meant only to provide guidance and general
recommendations on the operational practices of selected technologies. BMPs are not
meant to direct or dictate the selection of appropriate technologies.
The category of "other physical/chemical treatment" includes all technologies
that are not within the purview of the previous six chapters. BMPs for most of the in situ
treatment technologies are addressed in this chapter.
10.1 Definition and Scope of Other Physical and Chemical Treatment (for BMPs)
The classification of "other physical and chemical" treatment envelops a variety
of novel treatment technologies that are currently being applied to the treatment of
contaminated soils and solid media. These technologies can be applied independently or
in conjunction with other methods to enhance removal and/or stabilization of the
contaminants.
The following technologies are listed as a few examples of "other" treatment
technologies (for the purpose of BMPs):
• In Situ Radio Frequency • Fracturing
(RF) Heating • Solvent Extraction
• In Situ Vitrification • Phyto Uptake (Wetlands)
• In Situ IR Heating • Gasification/Pyrolysis
• Chemical Based • Debris Washing
Stabilization • Grouting
• In Situ Redox Control • Dechlorination
• In Situ Soil Flushing
The scope of BMPs for other physical/chemical treatment is not limited to the above
listed technologies. Although a number of treatment technologies are listed within this
technology category, details of only radio frequency (RF) heating, in situ
vitrification, in situ soil flushing, solidification/stabilization (S/S) and off-site
disposal have been addressed in this document because of their broad applicability as it
pertains to issues related to cross-media transfer of contaminants.
BMPs presented in this chapter and previous chapters of this guidance can be
applied when appropriate, especially to these physical/chemical technologies that are
not specifically addressed here. BMPs for in situ radio frequency heating, which is
presented in this chapter, can be applied to in situ IR heating and in situ redox control.
For other technologies for which BMPs are not specifically provided in this chapter, the
list below provides reference to the chapter containing BMPs that can be applied to the
technology.
• Phyto Uptake and Dechlorination ~ Chapter 2
94
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• Solvent Extraction and Debris Washing ~ Chapter 5
• Gasification/Pyrolysis ~ Chapters 6 and 9
• Fracturing - Chapter 7
10.2 In Situ Radio Frequency (RF) Heating
10.2.1
Definition and Scope of In Situ RF Heating (for BMPs)
Radio frequency heating technologies use electromagnetic energy generated by
radio waves to heat soil in situ, thereby potentially enhancing the performance of
standard soil vapor extraction (SVE) technologies. RF heating is designed to accelerate
the removal of volatile organics and to make it possible to remove semivolatile organics
that would not normally be removed by standard SVE technologies. Contaminants are
removed from in situ soils and transferred to collection or treatment facilities. The RF
energy causes dielectric heating of the soil. Some conductive heating also occurs in the
soil (USEPA, 1995a).
RF heating is applicable only to wastes located above the water table, unless
saturated soils can be effectively dewatered.
A schematic diagram of an in situ RF heating system is shown in Figure 10-1, and a
cross-sectional diagram is shown in Figure 10-2 (USEPA, 1995a).
| = RF Energy Input Point
• = Vapor Extraction Point
X = Temperature Measurement Point
Vapor Barrier Perimeter
AC Power
Distribution
I
§„
as 2
11
I*
s«
« I • • I
XXX
-------
10.2.1.1 Key Features of In Situ RF Heating for the Purpose of BMPs
• Enhances the ability of SVE systems to remove organic
contaminants.
• Involves inground installation of vapor extraction
wells and electrodes or antennae.
• Employs a dielectric heating frequency between 2 MHz
and 2,450 MHz. Operating on a frequency band allocated
for industrial, scientific, and medical (ISM)
equipment minimizes Federal Communications Commission
(FCC) operating requirements.
• Heat soils to a temperature range of 100 to 3 00 °C (212 to
572°F), on average for the treated area.
• Field applications involve installation of:
— Boreholes into the contaminated area
— A vapor extraction and treatment system
— RF shield (sometimes) to control RF emissions
— Electrodes or antennae
Perforations for-
vapor collection
(face inward
toward energy
R
Ene
Po'
xtraction
Point
' "c:
| :
i ^ i
• c •
: c:
: c :
•
c •
- J
s I
'. :
'• c |
: c
• c
• c •
• e
4
F
rgy
ut Tempe
nt Measu
Po
•:
• :
•:
|:
I ;
=;
::
;
:
•
:
rature
ement Vapor
nt Extractior
Point
:
•-f!
3 :•
3 •:
3 |:
j :'•
j •:
T;
> j:
3 :'•
3 :•
) ;'.
• ;
3 •:
1 ;
3 ::
; .
3 ::
3 |;
3 ','•
3 ; I
-f connector
(for routing nsinQ
vapor horizontally
through vapor
collection manifold)
Figure 10-2. Cross-Section of an In Situ RF Heating System (USEPA, 1995a)
96
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10.2.2 In Situ RF Heating Technology Description
RF heating is performed by applying electromagnetic energy in the radio-frequency
band. The energy is delivered to electrodes placed into the soil cover. The mechanism of
heat generation is similar to that of a microwave oven and does not rely on the thermal
properties of the soil matrix. The power source for the process is a modified radio
transmitter. The exact frequency of operations is selected after evaluation of the
dielectric properties of the soil matrix and the size of the area requiring treatment. As
the soil is heated due to the dissipation of the RF energy, contaminants and moisture in
the soil are vaporized and pulled toward ground electrodes, which also serve as vapor
extraction wells. The vaporized water may act as a steam sweep to further enhance the
removal of organic contaminants. A standard SVE system provides a vacuum to the ground
electrodes and transfers the vapors to collection or treatment facilities. Contaminants
are treated using standard vapor treatment techniques. After soil treatment is complete,
the soil is allowed to cool. The SVE system may be operated during part or all of this
cooling period. The exact number of exciter and ground electrodes, electrode
configurations, vapor collection or treatment techniques, and other design details are
generally site-specific (USEPA, 1995a).
10.2.3 Cross-Media Transfer Potential of In Situ RF Heating
(a) General
General cross-media transfer potentials during pre-treatment and post-treatment
activities have been addressed in Chapter 2. In addition, the cross-media concerns
described for vapor extraction (Chapter 7) are generally applicable to this technology.
(b) Additional Concerns for In Situ RF Heating
• Release of contaminants (volatiles and particulates) during site
preparation and borehole drilling.
• Migration of hot vapors to cooler zones and the resulting re-
condensation of contaminants.
• Surface water intrusion from beyond the boundaries of the off-gas
hood into the contaminated area that is being treated.
• Downward migration of contaminant vapors to aquifer.
• Seasonal variation of the water table which causes contaminants to
move as the saturated zone fluctuates.
• The unanticipated occurrence of inorganics, such as mercury, can
increase requirements for system operation, emissions control, and
disposal of off-gases or other residues.
• Unexploded ordnance (UXOs) may pose a potential problem.
• With application of an SVE system, air can move through preferred
channels, such as around natural gravel lenses or fill materials
97
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around buildings or utility lines. This can result in ineffective
cleanup, leaving areas untreated or treated to levels higher than
allowable for closure.
10.2.4 Best Management Options to Avoid Potential Cross-Media Transfers
During In Situ RF Heating
General BMPs to prevent potential cross-media transfer of contaminants during
pre-treatment and post-treatment activities have been addressed in Chapter 2. Also,
proper system design is recommended prior to implementation of the remedial treatment to
avoid cross-media transfer problems during different treatment steps. However, BMP
options to control specific cross-media transfer of contaminants for in situ RF heating
treatments are furnished below.
RF Heating Treatment Activities - During the RF heating treatment process the
following activities are most commonly undertaken:
• Power Source Operation. In these systems the temperature rise occurs as a
result of ohmic or dielectric heating mechanisms. Ohmic heating arises as a
result of ionic current or conduction current that flows in materials in
response to the applied electric field. Dielectric heating arises from the
physical distortion of the atomic or molecular structure of polar materials
in response to the applied electric field. Since the electric field changes
direction rapidly in the RF heating, the alternating physical distortion
dissipates mechanical energy that is thermal energy in the material. The RF
heating process raises the temperature of the soil to a range between 100 to
300°C. It employs an array of metal electrodes which are placed in boreholes
drilled through the contaminated soil. The ground electrodes are generally
supplied with 480-Volt, 3-phase power in major applications.
• Vapor Collection and Treatment. The hot gases and vapors are collected by
means of a gas collection system and transported to the onsite vapor
treatment system by means of a vacuum blower. If carbon adsorption is used
to treat vapor, compressed air may be used for system control. Steam or hot
air is supplied when the carbon bed is regenerated onsite. Natural gas or
propane is used if flare is used to control vapors.
The following BMPs are generally recommended to be used, when necessary, for
preventing cross-media transfer of contaminants for the above activities:
/ Soil permeability should be tested to determine whether the vapor
extraction system will be capable of efficiently collecting the
volatilized contaminants, and to optimize location of vapor extraction
wells.
/ The site should be characterized in terms of the contaminants present,
particularly any volatile metals. This assists in determining which
contaminants will be volatilized by RF heating and collected by the vapor
extraction system.
98
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/ Buried metallic objects such as drums and tanks should be removed to the
extent possible. Also, the presence of buried explosive materials should
be checked to eliminate explosion potential.
/ RF excitor electrodes should not be installed close to a building or other
structure.
/ The configuration, number, depth, and orientation of extraction wells
should be determined so that the vapor extraction system can efficiently
collect any volatilized contaminants with no zones of stagnant air.
/ The well diameter, length, and location of screened zones of extraction
wells should be optimized so that the SVE system can efficiently collect any
volatilized contaminants.
/ Extraction wells should not be located near surface water impoundments,
underground storm sewers, or drains.
/ Well casings, screens, and other structural materials should be protected
from the potential effects of RF heating, such as the development of leaks
or cracks.
/ Leaks and preferential pathways should be checked following completion of
construction to ensure that the SVE system can efficiently collect all
volatilized contaminants.
/ The vapor barrier system should be designed to ensure that none of the
contaminants volatilized by the RF heating are released to ambient air
through the surface.
/ During the main treatment activities, as specified above, Radio Frequency
monitoring should be conducted to ensure that the RF field outside of the
treatment zone does not exceed the National Institute of Occupational
Safety and Health (NIOSH) or Federal Communications Commission (FCC)
requirements.
/ Organic or inorganic vapor emissions should be monitored as well and
appropriate emission control measures, described in Chapter 3 of this
document, should be used to prevent emissions above the allowable level
specified by the regulatory agency (EPA or authorized state).
/ If the vapor treatment system yields any moisture or liquids from the
treatment process, the contaminated aqueous stream should be collected in a
tank or a lined/contained system. This will prevent the contaminants from
mixing with the normal surface water runoff from the area and the
surrounding natural watercourse. The contaminated aqueous stream should
be treated or disposed in accordance with the applicable regulations.
99
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/ Continued use of emissions controls may be necessary after the treatment is
completed, since RF heating elevates the soil temperature and volatiles
may continue to be emitted for some time following treatment.
10.2.5 Waste Characteristics that May Increase the Likelihood of Cross-
Media Contamination for In Situ RF Heating
The effectiveness of in situ RF heating technologies could be compromised and
undue cross-media contamination may be caused under certain conditions identified in
this subsection. However, some of these limitations could possibly be overcome with
various technology specific modifications and variations. Please refer to technology-
specific references provided at the end of this chapter for additional information about
modifications or variations that can be used to enhance the effectiveness of in situ RF
heating technologies.
»• Highly saturated (greater than 25% moisture) soils will consume enormous
amounts of energy as the application of the RF heat causes the water to
evaporate, reducing the efficiency of the RF system.
»• RF heating will not treat nonvolatile organics, inorganics, metals, and
heavy oil.
>• Certain RF heating technologies may not operate most effectively at depths
below 50 feet (USEPA, 1995a).
>• Contaminants in clayey soils are usually strongly sorbed and difficult to
remove (USEPA, 1995b), which reduces the efficiency of the RF system.
10.3 In Situ Vitrification
10.3.1 Definition and Scope of In Situ Vitrification (ISV) (for BMPs)
In situ vitrification (ISV) uses electrical power to heat and melt earthen
materials (e.g., soils, sludges, mine tailings, sediments), waste materials buried in
earthen materials, and other earthen-like materials contaminated with organic,
inorganic, and metal-bearing hazardous and/or radioactive wastes. The molten material
cools to form a hard, monolithic, chemically inert, amorphous or crystalline product that
incorporates and immobilizes the thermally stable inorganic compounds and heavy metals
in the hazardous waste. Organic contaminants are either volatilized and captured at the
hood or pyrolyzed to form more volatile constituents, which are subsequently volatilized
and captured at the hood. The slag product is glass-like with very low leaching
characteristics.
A flowchart of the ISV process is shown in Figure 10-3. A cut-away view of a
treatment cell specifying the general limits for the volume treated is shown in Figure 10-
4 (USEPA, 1994a).
100
-------
OfMMHood
Cantraltod Air Input
Ctcwi Emlutam
Figure 10-3. ISV Equipment System (USEPA, 1994a)
101
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Electrodes
Void
Volumes
(individual
<150cu-ft)
Rubble
(10-20wt%)
Combustfole Liquids
(5-10 wt%)
Metal (5-15 wt%)
Combustible
Solids
(6-10 wt%)
Combustible
Packages
Individual
<30cu-ft)
\
Continuous Metal
(<90%dtetance
between
Figure 10-4. A Cut-Away View of a Typical Treatment Cell (USEPA, 1994a)
10.3.1.1 Key Features of In Situ Vitrification for the Purpose of BMPs
• Converts non-volatile inorganic waste into a non-
leachable vitrified mass.
• Gases/vapors are passed through the off-gas treatment
system and released to the environment.
• Uses electrical energy to heat and melt soil.
• Heats soils to a temperature range of 1600 to 2000 °C
(2900 to 3600°F).
• Field applications involve installation of:
— 12-inch outside diameter (OD) graphite
electrodes
— Off-gas quenching system that includes a water-
based quenching tower and high efficiency
Venturi scrubber; a secondary cooling system
(glycol-based) is then employed to keep the
water temperature within limits
— Optional aboveground thermal oxidizer for
treating organic vapors
— Electrical supply line and transformer
102
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10.3.2 In Situ Vitrification Technology Description
Several methods and configurations exist for the application of ISV. At a site
that has only a relatively shallow layer of contamination, the contaminated layer may be
excavated and transported to a pit where the vitrification will take place. At other
sites where the contamination is much deeper, thermal barriers could be placed along the
site to be vitrified and prevent the movement of heat and glass into adjacent areas. This
will force the heat energy downward and melt depths will be increased. A more
conventional approach to using ISV is to encapsulate the wastes and control the potential
for lateral migration of contaminants within a checkerboard pattern of melts.
ISV uses a square array of electrodes up to 18 feet apart, which is inserted to a
depth of 1 to 5 feet and potentially can treat down to a depth of 20 feet to remediate a
contaminated area. As the vitrified zone grows, it vitrifies metals and either vaporizes
or pyrolyses organic contaminants. A hood placed over the processing area is used to
collect combustion gases, which are treated in an off-gas treatment system. The gases
collected by the hood are treated by quenching, scrubbing, mist-elimination, heating,
particulate filtration, and activated carbon adsorption (USEPA, 1994a).
10.3.3 Cross-Media Transfer Potential of In Situ Vitrification
(a) General
General cross-media transfer potentials during pre-treatment and post-treatment
activities have been addressed in Chapter 2.
(b) Additional Concerns for In Situ Vitrification
• Release of contaminants (volatiles and particulates) during site
preparation.
• Possible hazards due to high voltage electrical fluxes.
• Downward migration of melted contaminants or contaminant vapors to
aquifer.
• Contaminant vapors can be released away from the treatment zone if
there is an open pathway (e.g., pipe, french drain) that intercepts
the treatment zone. Sites should be inspected for open subsurface
conduits prior to applying ISV.
10.3.4 Best Management Options to Avoid Potential Cross-Media Transfers
During ISV
During ISV treatment activities, measures may need to be taken to control fugitive
emissions and to prevent release of contaminated media to the natural environment. The
following BMPs are generally recommended to be used when necessary for preventing cross-
media transfer of contaminants for the above activities:
103
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/ During large-scale operations, pumping wells and/or intercept trenches
should be installed around the treatment zone. This will prevent
groundwater from flowing through a contaminated treatment zone.
/ If open subsurface conduits are found, they should be disrupted (e.g.,
collapsed, broken, filled) prior to treatment.
/ The ISV treatment activities should be conducted under a controlled
environment when the off gases, volatiles, dusts, etc. are being emitted at
levels above the regulatory limit. The VOC emissions associated with these
activities should be controlled by capturing these emissions and then
treating the captured vapor/air.
/ To minimize disruption of contaminated soil, a thin layer of clean cover
soil should be placed over the contaminated area prior to the placement of
the off-gas collection hood. This practice eliminates the possibilities of
airborne contamination and tracking of contaminated material across the
site.
/ If the vapor treatment system yields any moisture or liquids from the
treatment process, the contaminated aqueous streams should be collected in
a tank or a lined/contained system. This will prevent the contaminants from
mixing with the normal surface water runoff from the area and the
surrounding natural watercourse. The contaminated aqueous stream should
be treated or disposed in accordance with the applicable regulations.
/ Typically 20-40% volume reductions occur as a result of the melting
process, which can lead to subsidence within the treated zone. Clean soil
is generally placed to fill in the subsided region as a standard practice,
and this should be consistently followed in all ISV treatment.
/ Arrangements should be made for leaving the vitrified mass in place or
exhuming it and disposing of it properly.
/ If the vitrified soil is to be left in place, clean soil should be backfilled
over it to encourage regrowth of vegetation.
/ Electrodes may be removed, decontaminated, reused, disposed of, or left in
the vitrified mass.
/ Drums or tanks filled with liquid, if removed from the treatment area,
should be disposed of in compliance with the applicable state and/or
federal regulations.
10.3.5 Waste Characteristics that May Increase the Likelihood of Cross-
Media Contamination for In Situ Vitrification Technologies
The effectiveness of in situ vitrification technologies could be compromised and
undue cross-media contamination may be caused under certain conditions identified in
104
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this subsection. However, some of these limitations could possibly be overcome with
various technology specific modifications and variations. Please refer to technology-
specific references provided at the end of this chapter for additional information about
modifications or variations that can be used to enhance the effectiveness of in situ
vitrification technologies.
*• Organic contents of greater than 10% by weight within the soil matrix might
require additional or modified off-gas treatment components.
Alternatively, soils of higher organic contents (e.g., exceeding 20%) have
been successfully treated by slowing the melting rate to levels that allow
acceptable heat removal rates in the off-gas treatment system (Campbell,
1995).
»• Pockets of flammable liquid or vapor sealed in containers beneath the soil
surface can create a potential explosion hazard.
>• In cases where heavy metal immobilization is desired, soils containing less
than 50% by weight of glass formers (e.g., aluminum and silica), and < 2% by
weight of alkali compounds (e.g., sodium and potassium), may require
modification with additives to obtain desired melt and vitrified product
characteristics (Campbell, 1995).
>• Depths greater than 20 feet (6 meters) require higher power-level equipment
because of the larger masses and volume that are being treated (Campbell,
1995).
>• Soils that contain inorganic debris greater than 55% by volume are
extremely difficult to treat with this technology (Campbell, 1995).
>• Soils with high ground water recharge rates require special methods to
limit recharge to acceptable rates.
10.4 In Situ Soil Flushing
10.4.1 Definition and Scope of In Situ Soil Flushing (for BMPs)
In situ soil flushing is the extraction of contaminants from the soil with water or
other suitable aqueous solutions. Soil flushing is accomplished by passing the
extraction fluid through in-place soils using an injection or infiltration process.
Extraction fluids must be recovered and, when possible, are recycled. Typically, soil
flushing is used in conjunction with other treatments that destroy contaminants or remove
them from the extraction fluid and groundwater (USEPA, 1992a).
In situ soil flushing includes conventional and unconventional techniques. The
conventional techniques include well-and-capture methods in the vadose zone and pump-
and-treat systems in the saturated zone. Unconventional techniques consist of primary,
secondary, and tertiary recovery techniques (USEPA, 1993a).
105
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Figure 10-5 is a schematic diagram of an in situ soil flushing system in which the
treatment solvent is injected into the soil (USEPA, 1993a). Figure 10-6 is a schematic
diagram of an in situ soil flushing sprinkler system (USEPA, 1993a). Figure 10-7 is a
cross-section of an in situ soil flushing system that uses spray application (USEPA,
1991b).
106
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Mobile in situ
contaminant/treatment system
(injection/recovery unit)
Mobile independent physical chemical
(1PC) waste water treatment system
Stony wall keyed into
mquiclude
Figure 10-5. Schematic of In Situ Flushing Field Test System (USEPA, 1993a)
10.4.1.1 Key Features of In Situ Soil Flushing for the Purpose of BMPs
• Fluid injection.
• Contaminant mobilization and removal.
• Secondary and tertiary recovery in some cases.
• Field applications involve installation of:
— Subsurface injection wells or aboveground
sprinkler/infiltration bed systems
— Boreholes for recovery wells or other
subsurface recovery devices in the contaminated
area
— Delivery and recovery drain lines
— Reagent delivery system
— Produced fluid treatment system
— Physical (e.g., sheet pile wall) or hydraulic
(e.g., groundwater depression or mounding)
barriers to contain contaminants
107
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• SB
. Granular activated
carbon units
PRC«T»PRC
\\fellno.l
Paniculate
Filters Holding
t3nk/water<
reservoir
Flowpatte
L = Vfell liquid sample
SB = Soil backround
ST = Soil treatment sample
PRC = Precarbon water
POC = Postcarbon water
CS = Collection sump
WsUno.2
70 feet
Figure 10-6. Soil Flushing Sprinkler System (USEPA, 1993a)
*
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10.4.2 In Situ Soil Flushing Technology Description
Schematics of different types of in situ soil flushing applications are provided
in Figures 10-5 through 10-7.
In situ soil flushing includes conventional and unconventional techniques. The
conventional techniques include well-and-capture methods in the vadose zone and pump-
and-treat systems in the saturated zone. Unconventional techniques consist of primary,
secondary, and tertiary recovery techniques (USEPA, 1993a).
10.4.3 Cross-Media Transfer Potential of In Situ Soil Flushing
(a) General
General cross-media transfer potentials during pre-treatment and post-treatment
activities have been addressed in Chapter 2. Soil flushing is different from most other
technologies used to remediate contaminated soils; therefore, the concerns about cross-
media contamination are fairly unique and are discussed in the next section.
(b) Additional Concerns for In Situ Soil Flushing
• The primary waste stream generated is contaminated flushing fluid,
which is recovered along with groundwater (Freeman and Harris,
1995). This fluid can cause cross-media contamination by migrating
into uncontaminated groundwater zones, or if mismanaged, can be
released into the surface environment.
• Treatment of the flushing fluid results in process sludges and
residual solids, such as spent carbon and spent ion exchange resin,
which may cause cross-media transfer of contaminants if improperly
managed and disposed (Freeman and Harris, 1995).
• Residual flushing additives in the soil may be a concern and should
be evaluated on a site-specific basis. These additives may require
additional separation or treatment prior to disposal (Freeman and
Harris, 1995).
• Bacterial fouling of infiltration and recovery systems and
treatment units may be a problem, particularly if high iron
concentrations are present in the groundwater or if biodegradable
reagents are used.
10.4.4 Best Management Options to Avoid Potential Cross-Media Transfers
During In Situ Soil Flushing
General BMPs to prevent potential cross-media transfer of contaminants during
pre-treatment and post-treatment activities have been addressed in Chapter 2. BMP
options to control specific cross-media transfer of contaminants for in situ flushing are
furnished below:
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/ A thorough site characterization should be conducted to determine all
leachable contaminants present.
/ Depth to groundwater (including any seasonal variations) and presence of
free product, if any, should be identified. All free product should
generally be recovered before any treatment begins.
/ During construction of injection wells, care should be taken to properly:
— Anchor wells
— Install suitable screen meshes
— Protect the wellhead
/ The recovery system should have adequate capacity to collect injected
fluids and groundwater, taking into account maximum practical aquifer
yield.
/ If bacterial fouling of any part of the treatment system is a problem, the
addition of compounds to control bacterial growth should be considered.
10.4.5 Waste Characteristics that May Increase the Likelihood of Cross-
Media Contamination for In Situ Flushing Technologies
Under the following conditions the effectiveness of in situ soil flushing (as
categorized for BMPs) could be compromised, and could cause undue cross-media
contamination.
>• Soils containing a high percentage of silt- and clay-sized particles
typically are strongly adsorbed and are difficult to remove. These soils
also tend to be less permeable (Freeman and Harris, 1995). The application
of in situ soil flushing to soils with these characteristics may increase
the need to use additives and reduce the efficiency of contaminant removal.
Reduced contaminant removal may require the treatment of very large volumes
of groundwater, which may increase the potential for cross-media
contamination.
*• Soils with low hydraulic conductivity (e.g., K < 1.0 x 10~5 cm/sec) will
limit the ability of flushing fluids to percolate through the soil in a
reasonable time frame (Freeman and Harris, 1995).
>• Moisture content can affect the amount of flushing fluids required. Dry
soils will require more flushing fluids initially to mobilize contaminants
(Freeman and Harris, 1995).
»• High humic content and high cation exchange capacity tend to reduce the
removal efficiency of soil flushing (Freeman and Harris, 1995).
>• Multiple factors, including high concentrations of fine sedimentary
materials, inorganic precipitation, formation of stable emulsions, or
110
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excessive biological activity can reduce the permeability required for
successful treatment (USEPA, 1993a).
10.5 Solidification/Stabilization
10.5.1
Definition and Scope of Solidification/Stabilization (for BMPs)
Solidification and stabilization (S/S) waste treatment processes involve the
mixing of specialized additives or reagents with waste materials to reduce physically or
chemically the solubility or mobility of contaminants in the environmental matrix
(Freeman and Harris, 1995). Solidification and stabilization are closely related due to
the fact that both use chemical, physical, and thermal processes to detoxify a hazardous
waste. But they are distinct technologies that involve physical/chemical treatment
process.
Figure 10-8 shows a schematic of typical S/S processes.
S/S Binding
Agent(s)
Excavation
(D
|
VOC Capture
and
Treatment
Classification
(2)
Oversize
Rejects
Crusher
,-•». Mixing
(3)
t
Water
Off-Gas
Treatment
(optional)
(4)
— »- Re
». Stabilized/Solidified
Media
Residuals
Ex Situ S/S Process
Stabilized/Solidified
Water-*.
S/S Binding -*•
Agent(s)
Media
Mixing
(1)
— fr>
Off-Gas
Treatment
(optional)
(2)
Residuals
In Situ S/S Process
Figure 10-8. Generic Elements of Typical S/S Processes (USEPA,
1993d)
111
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10.5.1.1 Key Features of Solidification/Stabilization for the Purpose of
BMPs
• Requires mixing of reagents, either on- or off-site.
• Immobilizes contaminants.
• Like other immobilization technologies, does not
destroy inorganic waste, but may alter or change
organic waste.
• Stabilization can be combined with encapsulation or
other immobilization technology(ies).
• May increase total volume of materials that must be
handled as waste.
• Wastes treated with S/S may be amenable to reuse
following treatment.
• Field application may involve installation of any or
all of the following:
— Auger type drilling and mixing equipment for in
situ applications
— Dust collection systems
— Volatile emission control systems
— Bulk storage tanks
10.5.2 Solidification and Stabilization Technology Description
Solidification refers to processes that encapsulate the waste in a monolithic
solid with structural integrity. The encapsulation may be that of compacted fine waste
particles or of a large block or container of wastes. Solidification does not necessarily
involve a chemical interaction between the waste and the solidifying reagents, but may
mechanically bind the waste in the monolith. Contaminant migration is restricted by
vastly decreasing the surface area exposed to leaching and/or by isolating the waste
within an impervious capsule (USEPA, 1994c).
Stabilization refers to processes that reduce risk posed by a waste by converting
the contaminants into a less soluble, mobile, or toxic form. The physical nature of the
waste is not necessarily changed. Phosphates, sulfides, carbonates, etc. can be used as
treatment reagent.
In many instances stabilization is exclusive of solidification. Stabilized
product should have low leaching characteristics. Many of the reagents used for S/S
process are also used in other chemical treatment processes such as dechlorination.
112
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S/S systems can be used to treat contaminated soil or wastes in place or can be
employed to treat excavated wastes externally for their subsequent disposal.
10.5.3 Cross-Media Transfer Potential of Solidification/Stabilization
(a) General
General cross-media transfer potentials during pre-treatment and post-treatment
activities have been addressed in Chapter 2.
(b) Additional Concerns for Solidification/Stabilization
• Leaching of contaminants or excess reagents to ground water from
treated waste that is disposed on site.
• Long-term degradation of the stabilized mass, creating the
potential for solidified wastes, reagents, VOCs, and other
contaminants to be released from the treated waste.
10.5.4 Best Management Options to Avoid Potential Cross-Media Transfers
During Solidification/Stabilization
General BMPs to prevent potential cross-media transfer of contaminants during
typical S/S pre-treatment and post-treatment activities have been addressed in Chapter
2. BMP options to control specific cross-media transfer of contaminants for S/S pre-
treatment and treatment technologies are furnished below:
/ Under dry and/or windy environmental conditions, both ex situ and in situ
S/S processes are likely to generate fugitive dusts (Freeman and Harris,
1995). Refer to Chapter 2 for control mechanisms to reduce the potential
for cross-media contamination from fugitive dusts.
/ Materials that are removed during prescreening activities should be
disposed of properly.
/ S/S processes can produce gases, including vapors that are potentially
toxic, irritating, or noxious (Freeman and Harris, 1995). Vapor treatment
systems should be used to the extent possible to control the movement of
these vapors.
/ If volatile organics are present, off-gas capturing and treatment systems
should be designed according to recommendations provided in Chapter 3.
/ Reagent delivery piping should be regularly checked to ensure tight
fittings. This will reduce the likelihood of releases of VOCs.
/ Wastes should be homogenized as much as practicable before processing.
This can improve the efficiency of the stabilization activities, and may
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help to reduce spillage and other problems related to encountering
irregular masses during the mixing process.
/ Treated waste should be disposed in a covered area and above the ground-water
table.
10.5.5 Waste Characteristics That May Increase the Likelihood of Cross-
Media Contamination for Solidification and Stabilization
Technologies
The effectiveness of solidification and stabilization technologies could be
compromised and undue cross-media contamination may be caused under certain conditions
identified in this subsection. However, some of these limitations could possibly be
overcome with various technology-specific modifications and variations. Please refer to
technology-specific references provided at the end of this chapter for additional
information about modifications or variations that can be used to enhance the
effectiveness of solidification and stabilization technologies.
>• Physical mechanisms that can interfere with the S/S process include:
— Incomplete mixing due to the presence of high moisture or organic
chemical content resulting in only partial wetting or coating of the
waste particles with the stabilizing and binding agents and the
aggregation of untreated waste into lumps (Freeman and Harris,
1995).
— Disruption of the gel structure of the curing cement or pozzolanic
mixture by hydrophilic organics in the soil (Freeman and Harris,
1995).
— Undermixing of dry or pasty wastes (Freeman and Harris, 1995).
»• Chemical mechanisms that can interfere with the S/S process include:
— Chemical adsorption
— Precipitation
— Nucleation
>• Other factors that can interfere include:
— Precise tailoring of waste composition to the S/S process used
(USEPA, 1994c).
— Waste containing oil and grease in moderate to high concentrations.
For more details on the various chemical interactions that can reduce the
effectiveness, and thereby the stability, of S/S treatments, see Freeman and Harris,
1995, and USEPA, 1993b.
10.6 Excavation and Off-Site Disposal
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10.6.1 Definition and Scope of Excavation and Off-Site Disposal (for BMPs)
When a site is remediated by excavation and off-site disposal, the contaminated
material (typically a solid or semi-solid material such as soil or sludge) is excavated,
then transported off-site for treatment and/or disposal.
10.6.1.1 Key Features of Excavation and Off-Site Disposal for the Purpose
of BMPs
• Excavation or collection of contaminated soils,
followed by piling or mixing of the soils.
• Containerization or temporary storage of the
contaminated soils or solid media.
• Shipping of soils off-site for disposal.
• Field applications involve installation of a temporary
canopy, liner, or other physical barrier as presented
in Chapter 3 that minimizes movement of materials from
the site by wind, water, or any other mechanism.
10.6.2 Excavation and Off-Site Disposal Technology Description
Excavation and off-site disposal primarily involve equipment that is widely used
in the construction or non-hazardous solid waste disposal industries, such as
excavators, earth movers or backhoes, dump trucks, and containers of various shapes,
sizes, and materials. However, in general, hazardous waste excavation and off-site
disposal activities require significantly more attention to personal protection and
safety, including provisions for worker protection (special clothing, decontamination
techniques, etc.) and equipment decontamination.
10.6.3 Cross-Media Transfer Potential of Excavation and Off-Site Disposal
(a) General
The general cross-media concerns that are provided in Chapter 2, especially those
that refer to excavation and construction activities, are especially relevant to this
technology. Table 2-1 presents information on the contribution of remedial activities,
including excavation, materials handling, and transportation, that are of concern to all
remedial technologies including this option.
(b) Additional Concerns for Excavation and Off-Site Disposal
Concerns for excavation and off-site disposal center around the potential for
cross-media transfer during materials handling and transportation activities. Careful
attention should be paid to information presented in those chapters, particularly as it
relates to the handling and transportation of contaminated wastes.
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10.6.4 Best Management Options to Avoid Potential Cross-Media Transfers
During Excavation and Off-Site Disposal
General BMPs to prevent potential cross-media transfer of contaminants during
excavation and off-site disposal activities have been addressed in Chapters 2 and 3. The
BMP options presented in those chapters are most applicable to this technology. They
include:
/ Entry to the active site should be limited to avoid unnecessary exposure and
related transfer of contaminants, especially during site preparation and
staging.
/ Avoid entering the contaminated area. In unavoidable circumstances, build
a temporary decontamination area, which could be later used during cleanup
activities. Any above-ground and underground source of contaminants should
be identified and located prior to starting excavation of the contaminated
area.
/ Fugitive dust emissions should be controlled during excavation by spraying
water or other materials to keep the ground moist or covered. During wet
weather or rainfall no water spraying would be needed. See Chapter 3 for
more information on materials that can be used to control fugitive dust
emissions.
/ During transportation of contaminated soils or solid media, covers or
liners should be used to prevent dust and VOC emissions. These temporary
covers on trucks or other hauling equipment should be installed with care to
minimize possibilities for the waste to come into contact with high winds
during transport.
/ Any offsite runoff should be prevented from entering and mixing with on-
site contaminated media by building earthen berms or adopting similar other
measures, as outlined in Table 3-4.
/ Provisions should generally be made to capture on-site surface water runoff
by diverting it to a controlled depression-area or lined pit.
/ Covers, and if necessary, liners, should be used at all times when
contaminated materials are being stored. Covers should be used on trucks
that are moving materials around and from the site. See Chapter 3 for
details on covers and liners that should be considered for use during
excavation, storage, and transportation.
10.6.5 Waste Characteristics that May Increase the Likelihood of Cross-
Media Contamination for Excavation and Off-Site Disposal
Technologies
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Under the following conditions the effectiveness of excavation and off-site
disposal (for BMPs) could be compromised, and could cause undue cross-media
contamination.
»• When high volumes of soils are to be disposed of, this option may not be very
cost-effective.
»• For highly explosive materials, a simple excavation and disposal may not
provide the safest method of handling the waste.
10.7 References
1. Campbell, Brett E. 1995. Geosafe Corporation, Comments on BMP Workshop Summary-
Other Physical/Chemical Technologies, Personal Communication to Subijoy Dutta,
USEPA.
2. Dev, Harsh. 1995. IIT Research Institute, Letter Report on RF In Situ Heating and
Soil Decontamination Process, Personal Communication to Subijoy Dutta, USEPA.
3. Freeman, Harry M. and Eugene F. Harris. 1995. Hazardous Waste Remediation:
Innovative Treatment Technologies, Technomic Publishing Co., Inc., Lancaster,
PA.
4. USEPA. 1995a. SITE Technology Capsule: IITRI Radio Frequency Heating
Technology, EPA/540/R-94/527a, March.
5. USEPA. 1995b. Innovative Technology Evaluation Report, Radio Frequency Heating,
KAI Technologies Inc., EPA/540/R-94/528, April.
6. USEPA. 1995c. In Situ Remediation Technology Status Report: Surfactant
Enhancements, EPA/542-K-94/003, Office of Solid Waste and Emergency Response.
7. USEPA. 1995d. In Situ Remediation Technology Status Report: Cosolvents,
EPA/542-K-94/006, Office of Solid Waste and Emergency Response.
8. USEPA. 1995e. In Situ Remediation Technology Status Report: Hydraulic and
Pneumatic Fracturing, EPA/542/K-94/005, Office of Solid Waste and Emergency
Response.
9. USEPA. 1995f In Situ Remediation Technology Status Report: Electrokinetics,
EPA/542/K-94/007, Office of Solid Waste and Emergency Response.
10. USEPA. 1995g. Dynaphore Inc. Forager Sponge Technology, Innovative Technology
Evaluation Report, EPA/540/R-94/522, Office of Research and Development,
Washington, DC, June.
11. USEPA. 1995h. Geosafe Corporation In Situ Vitrification Innovative Technology
Evaluation Report, EPA/540/R-94/520, Office of Research and Development,
Washington, DC, March.
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12. USEPA. 1995i. IITRI Radio Frequency Heating Technology, Innovative Technology
Evaluation Report, EPA/540/R-94/527, Office of Research and Development,
Washington, DC,
13. USEPA. 1995J. SITE Emerging Technology Summary, Reclamation of Lead from
Superfund Waste Material Using Secondary Lead Smelters, EPA/540/SR-95/504,
Center for Environmental Research Information, Cincinnati, OH.
14. USEPA. 1995k. SITE Emerging Technology Bulletin, Waste Vitrification Through
Electric Melting, Ferro Corporation, EPA/540/F-95/503, Risk Reduction
Engineering Laboratory, Cincinnati, OH, March.
15. USEPA. 19951. SITE Emerging Technology Bulletin, Electrokinetic Soil
Processing, Electrokinetics, Inc., EPA/540/F-95/504, Risk Reduction Engineering
Laboratory, Cincinnati, OH, March.
16. USEPA. 1995m. SITE Technology Capsule, Texaco Gasification Process, EPA 540/R-
94/514a, Center for Environmental Research Information, Cincinnati, OH. April.
17. USEPA. 1995n. SITE Technology Capsule, KAI Radio Frequency Heating Technology,
EPA/540/R-94/528a, Center for Environmental Research Information, Cincinnati,
OH, January.
18. Drennan, Dawn. 1994. Technical Answers, Lasagna Process Treats Contaminants.
Environmental Protection, Stevens Publishing, Waco, TX, September.
19. USEPA. 1994a. Engineering Bulletin-In Situ Vitrification Treatment, EPA/540/S-
94/504, Office of Research and Development, Cincinnati, OH, October.
20. USEPA. 1994b. Emerging Technology Bulletin, Institute of Gas Technology, Fluid
Extraction-Biological Degradation Process, EPA/540/F-94/501, March.
21. USEPA. 1994c. William C. Anderson, ed. Innovative Site Remediation Technology,
Solidification/Stabilization, Volume 4, EPA/542/B-94/001, Office of Solid Waste
and Emergency Response.
22. USEPA. 1994d. Innovative Site Remediation Technology: Chemical Treatment,
Volume 2, EPA/542/B-94/004, Office of Solid Waste and Emergency Response.
23. USEPA. 1994e. Physical/Chemical Treatment Technology Resource Guide, EPA/542/B-
94/008, Office of Solid Waste and Emergency Response, Technology Innovation
Office, Washington, DC.
24. USEPA. 1994f SITE Demonstration Bulletin, SFC Oleofiltration System, InPlant
Systems, Inc., EPA/MR-94/525, Risk Reduction Engineering Laboratory, Cincinnati,
OH, October.
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25. USEPA. 1994g. SITE Technology Capsule, InPlant Systems, Inc., SFC 0.5
Oleofiltration System, EPA/540/R-94/525a, Center for Environmental Research
Information, Cincinnati, OH, December.
26. USEPA. 1993a. Innovative Site Remediation Technology: Soil Washing/Soil
Flushing, Volume 3, EPA/542/B-93-012, November.
27. USEPA. 1993b. Technical Resource Document-Solidification/Stabilization and its
Application to Waste Materials, EPA/530/R-93/012, Office of Research and
Development, Washington, DC, June.
28. USEPA. 1993c. Accutech Pneumatic Fracturing Extraction and Hot Gas Injection,
Phase I, Applications Analysis Report, EPA/540/AR-93/509, Office of Research and
Development, Washington, DC, July.
29. USEPA. 1993d. Engineering Bulletin, Solidification/Stabilization of Organics
and Inorganics, EPA/540/S-92/015, Office of Research and Development,
Cincinnati, OH, May.
30. USEPA. 1992a. Guide for Conducting Treatability Studies Under CERCLA Solvent
Extraction, Interim Guidance (and Quick Reference Fact Sheet), EPA/540/R-92/016A
and B, Office of Emergency and Remedial Response, August.
31. USEPA. 1992b. Seminar Publication: Organic Air Emissions from Waste Management
Facilities, EPA/625/R-92/003, August.
32. USEPA. 1992c. Guide for Conducting Treatability Studies Under CERCLA, Chemical
Dehalogenation (and Quick Reference Fact Sheet), EPA/540/R-92/013A and B, Office
of Solid Waste and Emergency Response, May.
33. USEPA. 1992d. Engineering Bulletin-Supercritical Water Oxidation, EPA/540/S-
92/006, Office of Research and Development, Cincinnati, OH, September.
34. USEPA. 1992e. A Citizen's Guide to Glycolate Dehalogenation-Technology Fact
Sheet, EPA/542/F-92/005, Office of Solid Waste and Emergency Response,
Technology Innovation Office.
35. USEPA. 1992f A Citizen's Guide to In Situ Soil Flushing-Technology Fact Sheet,
EPA/542/F-92/007, Office of Solid Waste and Emergency Response, Technology
Innovation Office.
36. USEPA. 1991a. Engineering Bulletin: Control of Air Emissions From Materials
Handling During Remediation, EPA/540/2-91/023, October.
37. USEPA. 1991b. Engineering Bulletin-In Situ Soil Flushing, EPA/540/2-91/021,
Office of Research and Development, Cincinnati, OH, October.
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38. USEPA. 1991c. Engineering Bulletin-Chemical Oxidation Treatment, EPA/540/2-
91/025, Office of Emergency and Remedial Response, Washington, DC, Office of
Research and Development, Cincinnati, OH, October.
39. USEPA. 1991d. Engineering Bulletin-Granular Activated Carbon Treatment,
EPA/540/2-91/024, Office of Research and Development, Cincinnati, OH, October.
40. USEPA. 1990. Engineering Bulletin-Chemical Dehalogenation Treatment: APEG
Treatment, EPA/540/2-90/015, Office of Research and Development, Cincinnati, OH,
September.
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11.0 Chapter Eleven: FIELD VALIDATION and CASE STUDIES of BMPs
This chapter provides information on the field use of best management practices
(BMPs) for controlling cross-media transfer of pollutants at sites where soils treatment
has been completed or is currently under progress. The information was compiled with the
following objectives:
• Provide highlights of BMPs observed at each site,
• Provide details on how certain BMPs were used at different sites,
• Compare recommended BMPs with the current practices in
the field, and
• Incorporate new or modified BMPs in the relevant sections of the BMPs
guidance.
The information contained in this chapter was developed by examining detailed site
workplans and soils treatment reports, as well as by interviewing site remediation
managers and observing remediation activities at volunteering sites. In total,
information on the field use of BMPs was obtained from eight sites (located in the states
of Colorado, Connecticut, Maine, Maryland, Minnesota, and Virginia) covering the
following six types of soils treatment technologies: containment, soil washing/soil
leaching, soil-vapor extraction, thermal treatment, bioremediation, and chemical based
stabilization.
This field validation study was undertaken at a limited number of sites due to time
constraints and ready availability of volunteering sites. However, after this guidance
is used at various sites, EPA plans to contact additional volunteering sites from
different parts of the country to get their experience with the recommended BMPs. This
feedback would be incorporated in the next update of the BMPs guidance.
Table 11-1 summarizes key characteristics of the sites EPA studied to obtain
information on the field use of BMPs. The first five case studies (Site Nos. 1-5) are
based on records provided by state personnel who had acted as coordinators of RCRA
Corrective Action Programs at the respective sites. These personnel also participated in
EPA's RCRA National Program Meeting in September 1996 to discuss the BMPs used at the
sites. The sixth case study (Site No. 6) is based on records provided by a federal
contractor acting as the planner and coordinator of environmental restoration activities
at the site. The last two case studies (Site Nos. 7 and 8) are based on information
obtained by EPA during site visits when detailed discussions were held with site managers
on their use of BMPs in remediation currently in progress.
Sections 11.1 through 11.8 provide details on the field use of BMPs at each site.
Each section briefly describes site remediation activities at the site followed by a more
in-depth description of the BMPs as used, and some views and discussion on the case study.
Finally, Section 11.9 provides a summary list of selected BMPs used at each site and
comparisons of those BMPs with the recommended BMPs in Chapters 4 through 10 of this
guidance.
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Table 11-1. Key Characteristics of BMP Case Study Sites
Site
No.
1
2
3
4
5
6
7
8
Site and Treatment Details
Location
Army Ammunition
Plant, Minnesota
Petroleum Refinery,
Minnesota
Closed Battery
Manufacturing
Facility, Virginia
Previously Used
Ammunition
Testing/Disposal
Site, Connecticut
Closed Electronics
Component
Manufacturing
Facility, Maine
DOE Manufacturing
Facility, Colorado
Closed Chromium
Manufacturing
Facility, Maryland
DoD Manufacturing
Facility, Virginia
Type of Soil
Contamination
Metals
Petroleum-
Derived
Hydrocarbons
Lead
Metals
(Primarily Lead)
Spent Organic
Solvents
VOCs in
Subsurface Soil
Chromium
Explosives-
Derived
(Organic)
Compounds
Area/Depth of Soil
Contaminated
16 Acres/2 Feet Below
Surface
Two Lagoons 0.5 Acre/Up to
10 Feet
Plant Site of 4.5 Acres/Up
to 3 Feet
Scattered Distribution of
Contaminated Areas Over
435 Acres/Mostly on
Surface
Below a Building, 3 Acre
Site
Two Trenches Each Up to
4,000 Square Feet, 10 Feet
Deep
15-20 Acres; Up to 80 Feet
or Bedrock
300 Foot Long Drainage
Area; 4-5 Feet Wide
Soil Treatment
Technology
Soil Washing/Soil
Leaching
In Situ Soil
Stabilization
Ex Situ Soil
Stabilization
Size Separation/Soil
Washing
Soil Vapor Extraction
Ex Situ Thermal
Desorption
Site Containment
Ex Situ Bioremediation
Volume of Soil
Treated
24,748 Tons
18,000 Cubic
Yards (10 Feet
Depth)
25,578 Cubic
Yards
1,000 Cubic
Yards (40,000
Cubic Yards
Planned for
Field Scale)
Estimated
40,000-50,000
Cubic Yards
2,200 Cubic
Yards
Estimated 1-2
Million Cubic
Yards
500 Cubic
Yards
Duration/Status of
Site Remediation
From 1993 to 1995
Conducted in 1995
Conducted in 1993
Pilot Study
Completed in 1995
In Progress from
1995
Conducted in 1996
In Progress from
1991
In Progress from
Summer 1996
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11.1 Soil Washing/Soil Leaching to Treat Metals Contaminated Soil at an Army Ammunition
Plant in Minnesota (Site 1)
11.1.1 Description of Site Remediation Activities
From 1993 through 1995, metals contaminated soil was excavated from an area of 16
acres in an Army ammunition plant in Minnesota and treated, when possible, by soil
washing/soil leaching on site. The treatment goals were to reduce the concentration of
lead to a regulatory level of 300 mg/kg and the concentration of several other heavy
metals to the background levels. The site was previously used as an open burning area for
scrap primers, fuses, and explosives related to small caliber arms and rifle grenades.
The metals contamination was generally limited to the uppermost three feet across the
site. The site was not contaminated with VOCs, SVOCs, or cyanide. The groundwater was not
impacted by soil contamination. However, twenty disposal areas were identified at this
site which were also excavated and remediated. The materials found in the disposal areas
included ordnance, high explosive items, cast-iron pots, crushed drums, characterized
chemical substances, and miscellaneous scrap metal, wood, concrete and glass debris. All
materials excavated from the disposal areas were identified and sorted for proper
treatment or disposal off site.
The site remediation was performed according to closure plans approved under a
RCRA Hazardous Waste TSD Permit and the Federal Facility Agreement (FFA) prepared for the
Installation Restoration Program (IRP) of the Army ammunition plant. The site closure
activities included site preparation, disposal area investigations and excavation,
metals-contaminated soil excavation and treatment, ordnance clearance, hazardous and
non-hazardous waste management, and site restoration to allow unrestricted future use of
the site.
Approximately 24,748 tons of contaminated soil were excavated at this site. A
total of 246 tons of metal concentrate were recovered during soil washing/soil leaching
activities. A total of 12,797 tons of soil were successfully treated and backfilled as
clean soil. A total of 7,125 tons of soil were treated to become non-hazardous and these
wastes are temporarily being stored on site. Approximately 4,555 tons of soil,
characterized as hazardous and non treatable on site, were recycled off site at a smelter.
11.1.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants
Because the remediated site was located in a large federal facility (2,300 acres)
where several private companies operated as facility tenants, there was a potential for
human exposure to lead and other toxic metals from fugitive dust emission during site
excavation, soil transportation and soil treatment. There was also a potential for
cross-media transfer of pollutants in uncontrolled surface water run-on to and run-off
from the site. Another concern was that a spillage and/or improper disposal of soil
treatment residuals might result in groundwater contamination. To address these cross-
media transfer concerns, various BMPs were used at this site during site remediation. A
list of 12 BMPs, as introduced in different remedial stages, is given below.
Site Preparation and Staging
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a. Delineating the actual limits of soil contamination by lead and other heavy
metals.
b. Establishing an exclusion zone and a decontamination pad to control all
traffic to/from the site.
c. Refurbishing the existing oil treatment pad/area to meet the staging needs
of soil washing/soil leaching on site.
d. Conducting an in-depth characterization of new disposal areas located on
site.
e. Removing and sorting the debris found in disposal areas.
f Installing an air quality monitoring system at the site.
Pre-Treatment
g. Building an earthen berm for controlling surface water run-on to and run-
off from the site.
h. Arranging for dust suppression during site remediation.
i. Covering haul trucks and excavated soil stockpiles.
Soil Treatment
j. Reusing stormwater as process makeup water.
k. Recycling process wastewater in soil treatment.
Post-Treatment
1. Reusing treated/clean soil in restoring the site.
Additional details on the field application of each of these BMPs are given below.
a. Delineating the Actual Limits of Soil Contamination by Lead and Other Heavy
Metals. Additional soil boring and field analysis of total lead concentrations were
performed as one of the earliest activities of site remediation in 1993 to further
delineate the previously estimated limits of soil contamination. A total of 326 soil
borings were made to collect soil samples at 6- and 12-inch depths every 25 feet along the
estimated limits. X-ray fluorescence (XRF) analysis was used to give a field
determination of soil quality. If samples from both depths at a given soil boring were
shown to have XRF lead concentrations of less than 100 ppm, the location was considered to
be non-contaminated. Additional XRF samples were then collected in an attempt to
delineate the boundary of contamination within five feet of the actual zone of
contamination (which also represented the horizontal limits of excavation). These
activities limited the total quantities of soil excavated and treated during site
remediation.
b. Establishing an Exclusion Zone and a Decontamination Pad to Control All Traffic
To/From the Site. After verifying the boundaries of contamination with laboratory
analysis of soil samples, the exclusion zone was established by providing a buffer zone
outside the finalized limits of contamination. Access to the exclusion zone was limited
to qualified personnel wearing the appropriate personnel protective equipment and to
perform only the site remediation activities approved by the site closure plan. After
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establishing the exclusion zone, a decontamination pad was constructed for vehicle,
equipment, and personnel decontamination. All traffic into and out of the exclusion zone
went through the decontamination pad. The decontamination pad was a 6-inch thick asphalt
pad underlain with gravel subbase. The pad was constructed with a 3-inch high asphalt
berm around the perimeter to control run-off and run-on. All water used in the
decontamination pad was collected in a 100-gallon sump. Both the pad and sump were coated
with sealant to help prevent any seepage of contaminated water. Two 8-foot high wind
walls were constructed to minimize decontamination spray from migrating off the pad. A
fully enclosed personnel decontamination area was also constructed on the
decontamination pad. The construction of a decontamination pad with all these features
enabled the facility to effectively manage any release of pollutants taking place during
the excavation and/or transportation of contaminated soil at the site.
c. Refurbishing the Existing Oil Treatment Pad/Area to Meet the Staging Needs of
Soil Washing/Soil Leaching on Site. An existing concrete pad located near the site was
utilized for soil washing and soil leaching operations. The concrete pad was 6 to 8 inches
thick and had masonry block walls. The pad was used, however, only after preparing it for
soil washing/soil leaching equipment. The soil feed section of the pad used for
stockpiling contaminated soil was completely resurfaced with adequate slope for drainage
of water to a sump. Several large, deep cracks existing in other portions of the treatment
pad were also sealed to further ensure containment of pollutants released from the soil
and soil treatment process chemicals used on the pad. A new drive-over curb was
constructed to prevent contaminated water generated in the soil washing area from
entering the treated soil storage area. These preparatory efforts enabled the facility
to effectively contain any release of pollutants taking place during soil treatment on
site.
d. Conducting an In-Depth Characterization of New Disposal Areas Located on Site.
Prior to any soil excavation activities, a certified explosives and unexploded ordnance
contractor performed a visual ordnance survey within the exclusion zone. Based on the
quantity of ordnance identified on the surface of the site, it was decided to take up
additional investigative work on site. A magnetometer survey performed across the site
identified 24 soil anomalies. Investigative test trenching at the locations of these
anomalies and other suspect areas identified 11 disposal areas. Nine more disposal areas
were identified following excavation of metals contaminated soils through a review of
historical aerial photographs or verification test trenching.
e. Removing and Sorting the Debris Found in Disposal Areas. The disposal areas
were excavated before starting the excavation of metals contaminated soils. As a result,
the metals contaminated soils were segregated from the debris buried in the disposal
areas (these materials were untreatable by soil washing/soil leaching). The materials
found in the disposal areas included high explosive items with approximately ten pounds
of explosives. These items were detonated at two locations on site. All other debris were
sorted and sent off site for recovery or disposal.
f Installing an Air Quality Monitoring System at the Site. The health and safety
program at this site included the monitoring of specific air pollutants during the entire
period of remediation at disposal areas, metals contaminated soil excavation, and on-
site treatment of soil. For example, the investigative test trenching and disposal area
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excavation were conducted without encountering hazardous ambient conditions or action
level exceedances for airborne lead, combustible gases, oxygen, total dust, and hydrogen
cyanide. The maximum level of total dust was 0.070 mg/cu.m. (action level = 0.30
mg/cu.m.). The maximum airborne lead was 0.009 mg/cu.m. (action level = 0.03 mg/cu.m.).
The air quality monitoring was performed along with the monitoring of other air-borne
pollutants, such as noise and heat stress in the work areas.
g. Building an Earthen Berm for Controlling Surface Water Run-On to and Run-Off
From the Site. A soil berm approximately three feet wide and two feet high was constructed
immediately outside the exclusion zone. The berm was 1,330 linear feet and completely
surrounded the site. The berm was constructed to contain contaminated stormwater
precipitating on the site as well as to prevent surface water from flowing into the
exclusion zone.
h. Arranging for Dust Suppression During Site Remediation. In preparation for
encountering adverse working conditions, the site was provided with adequate dust
control measures. These measures included a 1.5-inch PVC water line constructed along
the site access road with sprinklers tapped into the line every 25 feet. The line was used
to wet the road, thereby minimizing fugitive dust along the road during the
transportation of contaminated soil to the treatment pad. A 3/4-inch black PVC water line
was also run along the boundary of the exclusion zone with valves located every 100 feet to
provide the entire site with an access to water.
i. Covering Haul Trucks and Excavated Soil Stockpiles. The excavated surface
soils were hauled from the site to the treatment pad in dump trucks covered with a tarp to
prevent spillage and dust emission. The transported soil was stored in the stockpile area
of the treatment pad. Additional quantities of excavated soil were stockpiled within the
exclusion zone near the decontamination pad. Stockpiles were maintained only to provide
adequate quantities for continuing on-site treatment operations. These soil stockpiles
were covered with reinforced plastic sheets to prevent fugitive dust emission and
rainwater infiltration. The same contaminated soil handling procedures were used for
excavation and transport of soils from the disposal area, as well.
j. Reusing Stormwater as Process Makeup Water. The storm water run-off from the
impervious soil treatment pad was collected in a 20,000 gallon holding tank. Stormwater
was also collected in sumps provided in the soil storage pad. To the best extent possible,
water in the holding tank was used as makeup water in the soil treatment process and
thereby eliminated the need for additional treatment of the contaminated stormwater.
k. Recycling Process Wastewater in Soil Treatment. Process water used in soil
washing/soil leaching was normally recycled throughout the project. Recycling of the
process water minimized generation of process wastewater.
1. Reusing Treated/Clean Soil in Restoring the Site. The successfully treated
soil was used to backfill the site; the site was regraded, provided with clean top soil and
revegetated for better soil erosion control. By using treated soil in restoring the site,
it was possible to prevent disposal of large quantities of excavated soil (with residual
contamination) off site.
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11.1.3 Views and Discussion
In addition to the practices listed above, efforts were taken to minimize the need
to dispose of hazardous treatment residuals off site. In the first year of site
remediation (1993), for example, batches of soil that did not meet treatment standards
for any of the heavy metals of concern were hauled back to the contaminated soil feed pad
for reprocessing. These batches were placed in stockpiles where some mixing with other
soils occurred. The batches failing to meet treatment standards in 1994 and 1995 were
first assessed to determine the likelihood of being managed as non-hazardous waste. When
the TCLP results indicated that the soil was non-hazardous, then the batch was
transported to a separate soil storage pad. Other batches failing to meet treatment
standards were disposed off-site.
The soil treatment residuals also included metal concentrates generated in the
density separation stage and electro winning unit of the soil washing/soil leaching
process. The metals concentrates were accumulated in drums and manifested to a smelter
for metal recovery. Treated soil found to be hazardous was sent off site for metal
recovery.
Following completion of soil excavation and treatment activities, the
decontamination pad built near the site was excavated and treated. (Wipe samples were
collected on the surface of the decontamination pad prior to the commencement of any work
and after completing all work on the pad.) The material excavated from the pad was then
disposed of as non-hazardous waste.
11.2 In-Situ Chemical Based Stabilization of Petroleum Contaminated Soil at a Refinery
in Minnesota (Site 2)
11.2.1 Description of Site Remediation Activities
In 1995, two previously used biological treatment facilities (aeration lagoons),
part of a refinery's wastewater treatment plant in Minnesota, were closed after
implementing in situ chemical based stabilization for approximately 18,000 cubic yards
of petroleum contaminated soil at the facilities. Both lagoons had occupied the eastern
portion of an area of fill between a bedrock escarpment and the Mississippi River. The
topography of the fill was relatively flat, rising slightly to the north. The original
lagoon bottoms were approximately 15 to 20 feet below the ground surface nearby and lagoon
elevations were normally at the same level as the river.
Both lagoons were identified in 1990 to be hazardous waste management facilities
due to the occasional presence of benzene in concentrations exceeding the toxicity
characteristic limit in the wastewater entering the first of two lagoons which were in
series. A RCRA Part B permit application to continue operation of the lagoons was then
submitted to EPA and the Minnesota Pollution Control Agency (MPCA). However, it was
decided to permanently close the existing facilities subsequent to the initiation of a
groundwater monitoring program in the vicinity of the lagoons and investigation of the
pollutants in the subsoil in both lagoons. A partial stabilization of the subsoil in the
lagoons was then performed by mixing the top two to six feet of subsoil with cement using a
track-mounted backhoe equipped with injector tines. Based on the results of subsoil
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investigation conducted after these preliminary soil remediation efforts, it was decided
to perform additional stabilization of subsoil in the lagoons. The refinery submitted a
revised closure plan for the two lagoons in 1994 and finally amended the revised closure
plan early in 1995.
Pursuant to the closure plan approved under RCRA, the subsoil in both lagoons was
stabilized in situ by utilizing a mixture of portland cement and fly ash (20:80 percent)
as a stabilizing agent or grout to reduce the potential for leaching the VOCs, SVOCs and
metals from the stabilized materials. The stabilization matrix is also expected to
reduce the generation of leachate and prevent the long-term release of organic compounds
to the groundwater from the soil underlying the stabilized materials in the lagoons. In
situ grouting of subsoil was performed by drilling into the subsoil with a 10-foot
diameter auger and mixing the soil in the borehole with grout as the auger was retrieved.
At each drilling and grouting location, a column of stabilized material of low
permeability was created which contained and immobilized contaminants within the soil.
Prior to the implementation of this soil treatment process, the lagoons were emptied of
oily sludge and wastewater.
11.2.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants
There was a potential for surface water pollution in the initial stages of
remediation at this site (e.g., removal of large quantities of oily sludge and wastewater
from the lagoons before commencing soil treatment) due to the close proximity of a river
to the site. Moreover, soil contamination at the site had adversely impacted groundwater
in the area and the quality of groundwater had to be monitored for several years to
determine if soil treatment had been effective. The following five BMPs were used to
prevent cross-media transfer of pollutants during the RCRA cleanup program at this site:
Site Preparation
a. Removing and containing liquid wastes found at the site.
Pre-Treatment
b. Arranging to prevent surface water run-on to the site.
Soil Treatment
c. Treating stormwater collected on site prior to disposal.
d. Conducting additional soil tests to determine the effectiveness of soil
stabilization.
Post-Treatment
e. Monitoring groundwater to determine the effectiveness of soil
stabilization.
Additional details on the field application of each of these BMPs are given below.
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a. Removing and Containing Liquid Wastes Found at the Site. Oily sludge and
wastewater were removed from the lagoons prior to soil remediation were collected in
portable tanks. Earthen berms (I1 high by 3' wide) surrounded each portable CAMU Padtank.
A poly tarp was placed on the ground and berms before the portable tanks were set in place.
The earthen berms and poly tarp were provided to address concerns of spills of the process
treatment residuals occurring near the tanks. (The tanks were placed outside the
remediation site and near a sharply sloped river embankment.)
b. Arranging to Prevent Surface Water Run-On to the Site. The lagoons were bound
on three sides with man-made dikes and on the fourth side by a 20 feet natural escarpment.
The higher ground beyond the escarpment was occupied by the refinery which was on a well-
paved, graded and diked area. Because the soil stabilization area was in a floodplain of
the Mississippi River, the top of the west dike facing the river was elevated by 3 feet as
additional precaution against flooding during spring time.
c. Treating Stormwater Collected on Site Prior to Disposal. There was ample
freeboard (13 feet) to prevent run-off from the soil stabilization area. The accumulated
stormwater was pumped for treatment to an adjacent wastewater treatment plant. The pumps
and wastewater treatment plant had adequate capacity for this purpose.
d. Conducting Additional Soil Tests to Determine the Effectiveness of Soil
Stabilization. Confirmatory soil sampling was conducted to obtain additional
information on the depth of soil stabilization and soil quality. The soil samples were
examined visually and for odor, and screened for organic vapors using the jar headspace
method. The stabilized materials and unstabilized subsoils below stabilized materials
were then analyzed to determine the leachability of organics and metals present in the
samples.
e. Monitoring Groundwater to Determine the Effectiveness of Soil Stabilization.
If the stabilization matrix became less effective overtime, the VOCs and SVOCs released
before site remediation would be observed at increasing concentrations in the
groundwater near the site. A groundwater demonstration monitoring was started after
completing soil stabilization at this site. This activity included regular monitoring of
groundwater sampled at wells up and down gradient of the lagoons, as well as in aquifers
near the river. The closure plan for the site required groundwater monitoring every month
during the first year, every quarter in the second and third year, and semiannually in the
fourth and fifth year after the site remediation was completed.
11.2.3 Views and Discussion
At this site, there were opportunities for better addressing some of the major
cross-media transfer concerns that existed. For example, the berms around the portable
tanks used to collect and remove oily sludge and wastewater from the lagoons (see "a." in
Section 11.2.2) were not high enough to protect against a major spill of the liquid waste
being removed from site. In fact, the flexible hose from the lagoons to a tank became
loose during remedial activity at this site and flopped out of the containment. Nearly
2,000 gallons of oily sludge spilled into the adjacent river before the spill could be
stopped. If a site-specific emergency response plan was in place and implemented, it
might have prevented a major spill in this incident.
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The field screening and analysis of soil samples at both lagoons had shown the
presence of petroleum hydrocarbons in relatively high concentrations, including VOCs
like benzene and xylene and SVOCs like 2-methylnapthalene and phenanthrene. Under these
site conditions, fugitive emission of VOCs and other gases should be addressed by
monitoring the volatilization of organic compounds during soil treatment. The soil
stabilization process injected liquid slurry by means of an auger which avoided creating
a large area of soil-air contact and the volatilization of organic compounds present in
the soil. An air injection technology for the stabilizing agent might have resulted in
significant air emissions of volatile organics. Under these conditions, it would have
been appropriate to provide for collection and treatment of VOCs released from the site.
Air quality monitoring could have also addressed release of VOCs from the stabilized
soil.
Although some arrangements were made to prevent surface water run-on to the site
(see "b." in Section 11.2.2), the worst likely run-on scenario (e.g., possible breach of
the dike under a heavy flooding condition resulting in a wash out of the lagoon contents
and some contaminated soils into the river) should be estimated in sites located within
the floodplain.
11.3 Stabilization and Disposal of Lead Contaminated Soils at a Closed Battery
Manufacturing Facility in Virginia (Site 3)
11.3.1 Description of Site Remediation Activities
In 1993, a phosphate-based stabilization technique was successfully performed on
approximately 25,578 cubic yards of lead-contaminated soil and debris found in 11 acres
of land at a closed battery manufacturing facility site in Virginia. The site was
contaminated with lead concentrations in soil exceeding 100,000 mg/kg. The contaminated
soil exhibited toxicity characteristics by virtue of the Toxicity Characteristics
Leachate Procedure (TCLP) with lead concentrations in the leachate as high as 345 mg/1.
The phosphate-based stabilization process employed at the site significantly
decreased the leachability of lead in soil to levels well below the regulatory threshold
of 5 mg/1 by virtue of TCLP, and produced a material disposable at greatly reduced costs.
The soil remediation included excavating and mixing lead contaminated soil with triple
superphosphate (TSP), water and magnesium oxide (MgO) in a pug mill. Lead phosphate,
which has been shown to be among the least soluble and most stable forms of lead in the soil
environment, was formed. The action level for deciding to treat most of the lead
contaminated soils found at the site was kept at 1,000 mg/kg. Lower action levels were
given for lead contaminated soils found in the drainage ditch and sedimentation basin
used for stormwater control at the site (400 mg/kg) and in a previously used acid pond on
site (250 mg/kg).
11.3.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants
During the preparation of this site for remedial action, it was necessary to
prevent any removal of contaminated soil from the site without appropriate treatment.
Fugitive emission of dust containing lead and the "carry-over" of lead by stormwater run-
off were the main concerns during pre-treatment and soil treatment at this site. The main
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concern during post-treatment was the fact that action levels (1,000 mg/kg) for most of
the site might have resulted in concentrations of lead in soil remaining at the site to be
substantially higher than background levels. The facility addressed these concerns by
using at least the following six BMPs:
Site Preparation and Staging
a. Establishing site control zones to limit access to site.
b. Performing site clearing and grubbing with limited off-site removal of
pollutants.
Pre-Treatment
c. Installing an air monitoring system and on-site weather station.
d. Constructing a drainage ditch and sedimentation basin for stormwater run-
off control.
Soil Treatment
e. Modifying the process for treatment of soil from different areas of the
site.
Post-Treatment
f Backfilling the excavated areas and site vegetation.
Additional details on the field application of each of these BMPs are given below.
a. Establishing Site Control Zones to Limit Access to Site. The site fence was
relocated prior to any soil disturbance to provide security of the exclusion zone which
contained all soils with lead concentrations above 1,000 mg/kg. Access to the exclusion
zone was permitted only through the contamination reduction zone, where a pad was
constructed to serve as a transfer location for all personnel and equipment to and from
the exclusion zone. All decontamination water was collected and discharged to two 500-
gallon settling tanks. The tanks were placed in series and facilitated the settling of
sediments from the decontamination water. Lead and 10-micron particulate filters were
installed on the discharge pipe of the second settling tank to ensure the adequate removal
of suspended materials. The recycled water was then re-used for decontamination
purposes. If water re-use was not possible, the decontamination water was disposed off-
site. The filters were periodically replaced.
b. Performing Site Clearing and Grubbing with Limited Off-Site Removal of
Pollutants. Prior to excavation activities, but after health and safety and
environmental monitoring controls were emplaced, designated areas in the site were
cleared and grubbed to minimize the off-site transfer of lead contaminated soils without
treatment. All grubbed materials were decontaminated and then disposed off site. Other
building structures on site were dismantled and decontaminated with a high pressure spray
wash of water before the structures were disposed or recycled. This action also minimized
the off-site transfer of lead contaminated soils without treatment.
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c. Installing an Air Monitoring System and On-Site Weather Station. A Perimeter
Air Sampling Program (PASP) was implemented to document the impact of on-site remedial
action on the local ambient air quality. The critical concentrations to which ambient air
sampling results were compared were 150 //g/cu.m. for particulates less than 10 microns in
diameter (PM-10) and 1.5 //g/m3 for lead. The air monitoring was also used to ensure the
effectiveness of dust control at the site. There was only one exceedance of the critical
air concentrations during the entire site remediation period. It was determined to be due
to fugitive dust caused by dry soil conditions and heavy truck traffic. Corrective
actions were immediately taken by spraying additional water on excavated areas and
stockpiled materials to suppress fugitive dust emission. An on-site weather station was
used to control soil handling and excavation activities during high winds.
d. Constructing a Drainage Ditch and Sedimentation Basin for Stormwater Run-Off
Control. The sedimentation basin was constructed to provide for the collection and
recycling of contaminated runoff from the site and the settling of any contaminated
sediment from stormwater run-off throughout the site remediation period. The basin was
designed to retain runoff by providing two hours of retention time for all run-off
generated by a 25-year, 24-hour storm event. The retention time was adequate to settle
particles as small as 10 microns in diameter. Throughout the remedial process, collected
stormwater was recycled from the sedimentation basin to the pug mill for inclusion within
the solidification/stabilization process. This volume did not, however, constitute all
of the make-up water for pug-mill operations; an unspecified volume was transported from
off-site when the water level in the sedimentation basin was too low. Monthly samples of
the water in the stormwater retention basin and quarterly samples of the surface-water
which intermittently appeared in the drainage ditch, were collected and analyzed. The
samples were used to confirm that off-site contamination of surface water had been
prevented. Quarterly samples of the sediments were also taken in the drainage ditch
upstream and downstream of the sedimentation basin. No significant change was found in
the lead concentrations of the sediments obtained downstream of the sedimentation basin.
As expected, lead concentrations increased in the sediments obtained throughout the
period of site remediation from the drainage ditch upstream of the sedimentation basin.
e. Modifying the Process for Treatment of Soil from Different Areas of the Site.
Excavation of soil for constructing the sedimentation basin was completed first, and the
excavated soil was then separated into two storage areas: one area containing
contaminated soils and the other area containing soils below the performance standard for
lead of 1,000 mg/kg. The soil was then excavated from the remaining site, sampled and
stored accordingly. (As noted earlier, the performance standard for soils found in the
previously used acid pond was kept much lower at 250 mg/kg, and a performance standard of
400 mg/kg. was used for soils found in the drainage ditch and sedimentation basin after
completing soil excavation and treatment in the remaining site.) By segregating the soil
with lead above performance standards throughout the project, it was possible to minimize
the total quantity of soil to be stabilized and transferred off-site for disposal. The
areas used for stockpiling contaminated soil were the last to be excavated prior to pug
mill dismantlement. With dismantlement of the pug mill, the surrounding areas used for
staging, treatment and loading of treated soils were resampled, excavated and solidified
or stabilized in roll-on containers, as required. Soils from the drainage ditch and the
sedimentation basin were finally excavated and disposed. However, these soils were
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stabilized in situ to avoid a transfer of contaminated water from the wet soils excavated
at these locations in the site.
f Backfilling the Excavated Areas and Site Vegetation. After receiving
analytical results confirming that performance standards were achieved for all samples
of soil and sediments obtained after treatment at the site, the excavated areas were
backfilled with site soil that was found to be containing lead below 1,000 mg/kg, common
borrow and a 6-inch thick layer of topsoil. Trees were planted in a portion of the area
cleared during site preparation. All the disturbed areas on-site were subsequently
hydroseeded. The original fencing alignment was restored at the conclusion of disposal
operations, gated and locked. The background level of lead in soil for areas outside the
site was found to be only 100 mg/kg. The proper restoration of the site, despite
containment of lead contaminated soils above the background levels (between 1,000 and 100
mg/kg.), was an effective BMP as shown by surface water and groundwater monitoring being
conducted after site remediation.
11.3.3 Views and Discussion
In addition to ambient air quality monitoring throughout the remedial action (see
"b." in Section 11.3.2), this site conducted personal air monitoring during the startup
of each new type of work activity to determine the potential personal exposure to lead.
The action level for lead during personal air monitoring was 50 //g/m3 for an 8-hour time
weighted average (TWA). Both ambient and personal air monitoring were performed in
accordance with the Site Health and Safety Plan (SHSP), to determine that airborne lead
concentrations on and off-site were within acceptable ranges.
11.4 Particle Size Separation and Soil Washing at a Site Used Previously for Ammunition
Testing and Disposal in Connecticut (Site 4)
11.4.1 Description of Site Remediation Activities
Between September 1995 and November 1995, a pilot study was conducted at this site
to evaluate soil washing and chemical leaching of contaminated soil excavated from
several areas of environmental concern (AECs) in a large industrial property spread over
435 acres of wooded land. A total of 51 AECs, including 3 RCRA regulated units, were
identified in the property. Preliminary evaluation of remedial alternatives had
indicated that soil washing may be feasible as a soil treatment method in the majority (37
out of 51) of AECs. It was estimated that approximately 40,000 cubic yards of soil needed
treatment at these AECs. The constituents of concern in the soil are inorganic metals
(primarily lead). Organic constituents are not of particular concern because they were
generally present at concentrations below the proposed RCRA corrective action levels.
Soil composition and contaminant distribution varied significantly among the AECs, and
in some cases, within each AEC. A pilot study was therefore required to determine a viable
and cost-effective remedy which will be protective of human health and the environment.
The site applied for a Corrective Action Management Unit (CAMU) status for an area
adjacent to one of the AECs to facilitate the storage and processing of soil from various
AECs during the pilot study. EPA approved this request in October 1994 and a paved pad was
constructed for management of excavated soil and treated soil at the CAMU. The pilot
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study was conducted at the CAMU pad and included soil washing runs at varying feed rates
(based upon the amount of particulate lead, physical characteristics, and organic
material present in the soils) obtained from different AECs. The treatment goal of each
soil washing run was to reduce total lead content to 1,000 mg/kg, as well as to meet the
TCLP or SPLP levels for determining the treated soil to be non-hazardous. Chemical
leaching was conducted on feed soils with high total lead content (10,000 mg/kg) and on a
few batches of residuals from soil washing not meeting the treatment goals for TCLP/SPLP.
In addition to a pilot study of soil washing/soil leaching, the site conducted a pilot
study of processing the shotgun shells separated from the contaminated soil during soil
washing pilot runs.
The pilot study found that soil washing provided an optimized and steady-state
processing of soil with varying characteristics excavated from the AECs. Based on the
results of the pilot study and a comparison of treatment alternatives, soil washing was
recommended for full-scale operations at the site. A few process changes and alternative
risk based treatment criteria were also recommended by the study. The existing CAMU has
also been recommended, with a few modifications, for use in full-scale soil washing
operations at the site.
11.4.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants
During the pilot study involving soil excavation at AECs and soil treatment
operations at the CAMU, the following concerns for cross-media transfer of pollutants
existed: (i) the migration of contaminants like lead, mercury, strontium, asbestos, etc.
as dust from different work areas, and (ii) surface water/groundwater contamination with
metals and organics released from the soil during soil washing and chemical leaching
operations. The pilot study was therefore designed to address these concerns while
evaluating alternative soil treatment methods for their performance in meeting the
treatment goals. Accordingly, the following six BMPs were used during the pilot study:
Site Preparation and Staging
a. Monitoring of air quality at AECs and the CAMU pad.
b. Installing a new CAMU pad for soil treatment operations.
Pre-Treatment
c. Arranging for dust suppression at AECs and the CAMU pad.
d. Providing covered and lined roll-offs for managing soil treatment
residuals.
Soil Treatment
e. Collecting and treating stormwater run-off from the CAMU pad and wastewater
from soil treatment processes.
Post-Treatment
f . Monitoring groundwater upgradient/downgradient of site.
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Additional details on the field application and effectiveness of each of these BMPs are
given below.
a. Monitoring of Air Quality at AECs and the CAMU Pad. During the pilot study, both
air sampling and real-time monitoring of air quality were performed for lead, total dust
and other contaminants. Baseline samples were collected at the perimeter of each area
before start of operations to obtain background data. Then, air sampling was performed
over the entire period of operations during each day in the area of interest. The air
samples were sent to a laboratory approved by the American Industrial Hygiene Association
(AIHA) which used NIOSH or OSHA methods. Typically, air samples were taken downwind of
the area of interest. In some cases, samples of air were also taken upwind of the area.
Real-time monitoring of total dust in the air was conducted periodically at upward and
downwind locations during soil excavation at AECs. Monitoring of total dust was
performed by an aerosol monitor to determine the concentrations of particulates in air. A
photo-ionization detector (PID) was used to periodically screen VOCs in soil during
excavation activities at AECs. Real time monitoring of total dust and mercury was
performed every 30 minutes around the CAMU pad.
b. Installing a New CAMU Pad for Soil Treatment Operations. The CAMU pad was
designed to store the following major types of soils/soil fractions (until the completion
of sampling and analysis to determine their future management) in full scale operations:
excavated soil, trommel oversize materials, wet-screen oversize materials, "clean"
coarse-grained sand and the concentrated fine-grained materials. The area for storage of
concentrated fine-grained material was provided with a concrete base and containment
berms. This area was also given adequate slope to a sump capable of collecting excess
water or stormwater run-off from the materials. The oversize materials were stored in a
lined storage area segregated by an earthen berm. The soil stockpiles were also stored in
a lined storage area with an earthen berm. However, this liner was protected from
vehicular traffic by a 6-inch layer of sand and a 3-inch layer of gravel. Closure of the
staging area for excavated soil will include removal of the gravel, sand and flexible-
membrane liner placed on ground.
c. Arranging for Dust Suppression at AECs and the CAMU Pad. The site controlled
airborne metals by suppressing dust during soil excavation at and during transportation
of soil from AECs. This involved spraying water in the excavation areas and on
transported soil. Watering trucks were used for dust suppression in remote areas of the
site. The trucks used for transporting the soil were also kept covered as a method of dust
suppression. Because of the presence of lead in the soil being treated, the Health &
Safety Plan for the pilot study required the provision of adequate dust control measures
in the CAMU pad. However, a significant emission of dust did not occur in soil-washing
itself because the materials were kept wet during the process. The stockpiles of soil in
the CAMU pad were either sprayed with water or kept covered with tarp as a dust suppression
measure. Water supply to the CAMU pad is provided by a fire hydrant line in the main
manufacturing plant.
d. Providing Covered and Lined Roll-Offs for Managing Soil Treatment Residuals.
The residuals of soil-washing included contaminated fine-grained material which was kept
stored preferably in covered and lined roll-offs to prevent leaching of metals and to
control dust emission.
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e. Collecting and Treating Stormwater Run-Off From the CAMU Pad and Wastewater
From Soil Treatment Processes. During soil washing operations in the CAMU pad, the
rainwater accumulated in the excavated soil storage area was pumped out into the soil-
washing process. The area used for storage of oversize materials generated wastewater
during the high pressure water/steam cleaning process. This wastewater was collected in
catch basins and treated in a plant existing on site. Soil particles separated from the
oversize materials were processed through the soil-washing system. The stormwater
collected in the fine-grained material storage area was analyzed first to determine the
level of contamination and then treated either on site or off site.
f Monitoring Groundwater Upgradient/Downgradient of Site. Groundwater sampling
was conducted quarterly prior to, during and after completing the pilot study at the site.
For this purpose, two existing groundwater monitoring wells downgradient of the site were
used. Analytical data compiled over a period of four quarters at these wells showed no
evidence of an impact on groundwater quality due to the metals or VOCs released during
soil-washing operations conducted in the pilot study.
11.4.3 Views and Discussion
Area and personal samples were also collected in the CAMU pad during the period of
soil-washing or shotgun-shell processing operations. The parameters sampled during the
pilot study included lead, total dust, mercury, strontium, acetic acid and asbestos ~
i.e., all contaminants of concern known to be present in the materials being processed in
the CAMU pad.
Based on the initial results of air sampling at the CAMU and AECs, which showed the
presence of mercury in air at elevated levels, real-time monitoring for mercury was
conducted at the property fence line for a brief period of time in the pilot study. A gold
film type mercury vapor analyzer was used for this purpose. Readings were taken both
upwind and downwind of the potential or suspected sources of mercury emission during
activities within the property. Background mercury data were also collected. The
results showed no public exposure risk due to release of mercury during site remediation
activities.
Based on the performance of soil treatment methods and field evaluation of cross-
media transfer of pollutants during the pilot study, several BMPs will be modified in
full-scale operations at this site. For example, it was decided to conduct only real-time
total dust monitoring on a periodic basis and biweekly air sampling for lead and total
dust during full-scale excavation activities at AECs and soil washing operations at the
CAMU pad. Only periodic personal and area sampling of air will be performed in the CAMU
pad: for lead and total dust during soil washing, and for asbestos during shotgun-shell
processing operations. It was also decided to eliminate the monitoring of mercury in
full-scale operations.
Other BMPs used in the pilot study that may require changes in full-scale
operations include technologies applied for long term storage of excavated soils and
treatment residuals on site. For example, the use of heavy duty poly tarpaulin covers
secured with sand bags in the pilot study to cover re-wash soils may have to be replaced
with other media for covering soils, such as foam coverings, wind screens, and/or water
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sprays with additives (see Table 3-2 for more details). The full-scale operations at this
large site would probably require the monitoring of surface waters in the area like
creeks, streams and wetlands.
11.5 Soil Vapor Extraction of Solvents at a Closed Electronic Component Manufacturing
Facility in Maine (Site 5)
11.5.1 Description of Site Remediation Activities
From March 1995, except for a shutdown during the coldest periods of winter in 1995
and 1996, a full-scale system for soil-vapor extraction (SVE) has been in operation at
this site to treat the soil below the main building at the facility. The soil
contamination occurred during previous manufacturing operations when spent solvents
leaked from a corroded piping used to transport the solvent wastes to an underground tank
outside the building. The soil below the main building was found to contain several VOCs
like tricholoroethene (TCE), tetrachloroethene (PCE), ethyl benzene, xylenes and 1,1,1-
trichloroethane. During the last several months of operation, the concentration of VOCs
in the influent to the SVE system has reduced from 1,200 ppm to less than 25 ppm. The off
gases generated by the SVE system are processed through granular activated carbon (GAC),
which is then regenerated on site in a mobile steam unit. The steam stripping also
recovers light and heavy DNAPLs originally contained in the off gases. The full scale
system was installed after conducting a range of investigations on site (e.g., soil
borings and soil gas survey, surface water and groundwater sampling, and records search
of chemicals used and building construction on site). A SVE pilot program was also
conducted on site before starting the full-scale operations.
11.5.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants
There was only a limited opportunity for cross-media transfer of pollutants from
the operation of SVE at this site due to the confinement of contaminated soil and off gases
below the main slab of the existing building. However, SVE pilot testing at this site
helped to better define the potential for release of off gases at various points away from
the SVE facility and the need for proper management of the contaminants (VOCs and DNAPLs)
in the off gases generated by the SVE system. Accordingly, the site used the following
three BMPs:
Site Preparation and Staging
a. Containerization of drill cuttings.
b. Ambient and workspace air monitoring for VOCs.
Soil Treatment
c. Recovering DNAPLs from soil-vapor.
Additional details on the field application of each of these BMPs are given below.
a. Containerization of Drill Cuttings. The soil monitoring points and SVE wells
installed on site involved the excavation of contaminated soils. In order to control the
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emission of VOCs during these activities, soil borings and drilling were performed with
an appropriate containerization of cuttings.
b. Ambient and Workspace Air Monitoring for VOCs. Ambient air monitoring of VOCs
was performed with a PID to ensure that Maine's state interim guidelines are being met for
the maximum ambient air concentrations of TCE (2 //g/m3), PCE (0.1 //g/m3), ethyl benzene
(1,000 //g/m3), xylenes (300 //g/m3), and 1,1,1-trichloroethane (1,000 //g/m3). This
activity also enabled a check of emission control measures installed in the SVE system.
Workspace air monitoring of VOCs was performed with a PID to ensure protection of worker
health and safety. By comparing the workspace air quality with the influent
concentration of VOCs, it was possible to check the general performance of the SVE system.
c. Recovering DNAPLs from Soil Vapor. By recovering DNAPLs from spent GAC, the
site prevented cross-media transfer of these pollutants from treatment residuals.
11.5.3 Views and Discussion
Because of the confinement of contaminated soil, and due to the fact that SVE
created a negative pressure under the main slab of the building, there was very little
potential for release of VOCs inside the building. Workspace air monitoring was,
however, conducted to confirm that the SVE system was operating properly at all times.
The confinement of soil under the building also prevented the leaching of contaminants to
groundwater or surface waters, making it unnecessary to monitor these media during the
operation of SVE at this site.
11.6 Excavation and Thermal Treatment of VOC-Contaminated Soil and Debris at a DOE Site
in Colorado (Site 6)
11.6.1 Description of Site Remediation Activities
During 1996, two trenches were excavated at this site to remove approximately
2,200 cubic yards of VOC-contaminated soil and debris which were believed to be
contributing to groundwater degradation in the area. The excavated materials were
treated on site by low temperature thermal desorption. The soils were also known to be
contaminated by low level radioactive materials. On the basis of site data obtained
before commencing site remediation, the depth of trenches was estimated to be nearly 10
feet. The trenches were excavated until VOC concentrations in soils were below cleanup
standards or the excavation encountered bedrock or groundwater. The contaminated
materials ~ soil and debris ~ were treated for removal of VOCs in a set of six thermal
desorption units (TDUs). Each TDU consisted of a low-temperature, low-vacuum extraction
chamber and an infrared heat source. The average treatment rate for the set of TDUs was
100 cubic yards per day. The maximum size of the soil/debris feedstock allowable to the
TDU was eight inches. After completing treatment and verifying the achievement of
cleanup standards, the treated soil was placed back in the trenches, compacted and
covered by clean top soil.
11.6.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants
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There was a potential for release of off gases at soil-vapor extraction (SVE) wells
which had been used in the past for soils treatment at this site. There was also a
potential for mixing soils with different levels of radioactivity during the treatment of
soils for VOCs. It was also necessary to minimize radiation hazards at this site. Other
concerns for cross-media transfer of pollutants to be addressed during this site
remediation included: contamination of clean top soil during excavation of contaminated
subsurface soil in the trenches; air emission of dust from contaminated soil feed
stockpiles (CSFSs) and treated soil stockpiles (TSSs) maintained on site during site
remediation; and contamination of stormwater run-on and run-off by contacting the
materials in CSFSs and contaminated debris stockpiles. A list of 12 BMPs used to address
these concerns is given below.
Site Preparation and Staging
a. Proper demobilization of SVE wells and equipment.
b. Performing a survey to detect low energy radiation.
c. Establishing site control zones.
d. Preparing debris and CSF stockpile areas.
e. Perimeter air quality monitoring.
Pre-Treatment
f Stripping the uncontaminated top soil at each trench.
g. Segregating CSFSs based on radiological measurements.
h. Providing a Jersey barrier with trench around each CSFS.
i. Arranging for use of special dust suppressants on TSSs.
j. Evaluating debris samples for need of treatment.
Soil Treatment
k. Using decontamination wastewater for dust control on CSFSs.
Post-Treatment
1. Backfilling and re vegetation of the site.
Additional details on the field application of each of these BMPs are given below.
a. Proper Demobilization of SVE Wells and Equipment. The site preparation
required properly abandoning five vadose zone SVE wells adjacent to one of the trenches
and drilling out the inner grout from the conductor casing of four previously abandoned
SVE bedrock wells. All unnecessary equipment was removed from the area. By completing
these tasks, the site prevented an unplanned release of soil vapor in the area and other
problems in excavating the trenches.
b. Performing a Survey to Detect Low Energy Radiation. Apre-work survey of low
energy radiation in the area was conducted during site preparation. For this survey, the
entire area was divided into 50-foot grids. The survey also measured radiation in 2-3
foot grids for areas (e.g., traffic zone) in contact with radiologically contaminated
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soil. Radiological monitoring was also conducted during excavation of trenches. This
enabled the facility to define the initial levels of radiological contamination of soil.
c. Establishing Site Control Zones. During site preparation, the trench
boundaries were staked and trench reference points were located. Access to the site was
restricted to six feet from the edges of the trench boundaries. A layout was also prepared
of the exclusion zone, contamination reduction zone and project support zone during site
remediation. Decontamination procedures were also developed for personnel and
equipment.
d. Preparing Debris and CSF Stockpile Areas. The facility prepared areas for
debris and contaminated soil stockpiles, as necessary, to minimize the quantities of
materials to be treated on site. For example, only the debris contaminated with VOCs, or
debris that could not be tested for VOCs, were processed in the TDU. Debris free of VOCs
were stockpiled in a different area. The upper 4 to 6 inches of uncontaminated topsoil
from the CSF and debris stockpile areas were also removed during site preparation and
stored for later use.
e. Perimeter Air Quality Monitoring. Four high-volume air sampling stations were
set up in the perimeter (one upwind and three downwind) of the source removal area. In
addition, the air monitoring of VOCs was conducted by using FID/PID during soil
excavation.
f Stripping the Uncontaminated Top Soil at Each Trench. The upper two feet of
uncontaminated top soil was stripped from each trench and stored near trench boundaries.
This enabled reuse of the top soil after treatment of contaminated soil and backfilling of
trenches with treated soil. Before excavating each trench, groundwater levels in the
area were monitored to establish the depth to prevent additional contamination and
excavation of soil.
g. Segregating CSFSs Based on Radiological Measurements. The soil exhibiting low
energy radiation greater than 3 times the background radiological measurements was
separated from other CSF stockpiles. This practice enabled the site to achieve the "put
back" levels of radiation after completing soil treatment and backfilling the trenches
with treated soil.
h. Providing a Jersey Barrier with Trench Around Each CSFS. The CSF stockpiles had
dimensions of approximately 40 feet by 40 feet established by Jersey barriers on three
sides to contain the contaminated soil. (A Jersey barrier is a portable concrete barrier,
generally used in highway construction for the purpose of dividing or demarcating lanes.
These barriers were provided to this facility at no cost, making this BMP very cost-
effective.) This feature minimized the commingling of stormwater run-on with the CSFSs
and minimize wind blown dispersion of soil. A custom fit, water resistant tarpaulin,
stretched across the Jersey barriers minimized accumulation of stormwater and further
minimized wind blown dispersion of soil. Care was taken to avoid contact between the top
side of the tarp and the contaminated soil within the CSFS. A plastic-lined, gravel-
filled trench surrounded the Jersey barriers to collect stormwater run-off from the CSFS.
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i. Arranging for Use of Special Dust Suppressants on TSSs. A special agent
(fibrous slurry) was used for dust control on treated soil stockpiles to minimize the use
of water. This agent is prepared by mixing two products with water just before use. The
first product includes binding material blended with natural earthen materials,
biodegradable organic compounds with other inert materials and natural cellulosic
materials. The second product is recycled cellulose. The mixture is a thick, viscous
slurry that will cling to vertical surfaces on application. Depending on the weather
conditions, this dust suppressant was found to be effective for several weeks after each
application.
j. Evaluating Debris Samples for Need of Treatment. The waste streams generated
during site remediation included debris from the trenches. Following evaluation of
debris samples, the debris was either processed in TDUs or sent for disposal off site.
This procedure minimized the need to treat debris on site, while preventing any
contamination due to poor waste management.
k. Using Decontamination Wastewater for Dust Control on CSFSs. Wastewater
generated at the site from personnel and equipment decontamination activities was used to
suppress dust from the CSFSs and/or the trenches being excavated. The use of
decontamination water for dust control reduced the amount of clean water required for
dust suppression on site and ultimately reduced the volume of wastewater generated during
site remediation. Stormwater run-off collected in the trenches surrounding CSFSs was
also used for dust control.
1. Backfilling and Revegetation of the Site. Site reclamation consisted of three
tasks: backfilling of treated material into trenches, demobilization of all equipment
and re-vegetation of the project support zone. Because the CSFSs were segregated based on
radiological measurements, it was possible to achieve the initial levels of radiation
when treated soils were put back into the trenches. The uncontaminated top soil stripped
from each trench during soil excavation was also used with treated soil in backfilling
operations.
11.6.3 Views and Discussion
In addition to the BMPs listed above, the site ensured that aqueous and organic
phase condensates recovered from the TDUs were treated and/or disposed of to minimize any
additional contamination due to improper waste management. Typically, the aqueous phase
condensates were treated on site and the organic phase condensates were containerized and
disposed off site. With reference to the BMP listed under 11.6.2(g), it would be
advisable to determine leachability of radioactive contaminants to groundwater before
backfilling treated soil.
11.7 On-Site Containment of Soils in Former Manufacturing Areas at a Chromium Plant,
Maryland (Site 7)
11.7.1 Description of Site Remediation Activities
In 1991, a Corrective Measures Implementation Program Plan (CMIPP) was submitted
by the owner of a 140-years old chromium ore processing facility in Maryland to prevent
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further migration of contaminants to the soil, groundwater and surface water. The owner
of the facility had stopped manufacturing operations in 1985 and entered into a Consent
Decree with EPA and Maryland Department of the Environment (MDE) in 1989 to investigate
the nature and extent of contamination at the 20-acre facility and submit the CMIPP based
on the findings of their investigations. These investigations found that the soils were
contaminated with hexavalent chromium (above the action level of 10 parts per million) in
a few areas of the site where the maximum concentration of chromium was found to be 94
mg/kg. Higher levels of contamination were also found in the sediments in the harbor
surrounding the peninsular facility. Both the shallow aquifer (0-20 feet below the
ground surface) and deep aquifer (23-70 feet below the ground surface) were found to be
contaminated with chromium, with the highest concentrations (14,500 mg/1 for the shallow
aquifer and 8,000 mg/1 for the deep aquifer) found near the former manufacturing area at
the facility. Chromium in the deep aquifer had migrated approximately 2,750 feet off-
site along the top of the bedrock where the concentration of chromium was 1,600 mg/1.
However, no user of the deep aquifer for drinking water could be identified. The surface
water in the marine harbor surrounding the facility was found to be contaminated with
chromium at the maximum concentration of 3,170 ppb (above the standards of 50 ppb for
chromium in marine waters).
The proposed corrective measures included: the installation of a deep vertical
hydraulic barrier (slurry wall) as a containment structure to prevent the release of
contamination into the marine harbor and groundwater surrounding the facility;
installation and operation of a groundwater withdrawal system within the containment
structure to maintain an inward hydraulic gradient of groundwater at the site;
construction of a multi-media cap over the containment area to prevent any future
exposure to the contaminated soil and control the generation of contaminated leachate
from any infiltration of precipitation at the site; and a comprehensive surface and
groundwater monitoring system to confirm that all the site remediation goals are being
achieved. In preparation for implementing these corrective measures, the facility owner
dismantled the manufacturing plant existing at the facility (including 21 buildings,
240,000 square feet of transite roofing, 15,000 tons of decontaminated equipment and
structurals and 50,000 tons of concrete and rubble to be sampled, classified and shipped
to appropriate facilities off-site). Prior to the construction of containment
structures, approximately 150,000 cubic yards of sediments were dredged from the harbor
surrounding the facility, a new outward embankment was constructed, and soil found on
site contaminated with chromium or other hazardous contaminants above the action levels
was excavated and disposed off-site.
The implementation of the CMIPP commenced in 1993 after completely dismantling the
plant and providing an asphalt cover over the former manufacturing areas at the site. The
deep vertical hydraulic barrier is now provided by a slurry wall mixture of soil and
bentonite encompassing 15 acres of the site. This slurry wall was trenched over a linear
distance of 3,300 feet by 3 feet wide with a depth ranging rom 65 to 80 feet up to the
bedrock. A multi-media cap of geosynthetic clay liner and 60 mil LDPE geomembrane covers
is now being provided over the area within the slurry wall. A system for pumping, treating
and disposing of the groundwater from the site is now operational. This system will
continue to operate in order to maintain an inward hydraulic gradient of 0.01 foot per
foot from outside to inside the slurry wall. After completing the construction of a
multi-media cap, the concentration of chromium in the surface water outside the facility
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will be maintained within regulatory levels by monitoring the performance of the slurry
wall and by controlling the rate of groundwater extraction from the site. This site
remediation is also designed to permit future development of the site as a mixed-use
(recreational and commercial uses) zone.
11.7.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants
The RCRA corrective action nearing completion at this site is designed primarily
to minimize the future releases of contaminants from the soils to the air, surface water
and groundwater. In addition, the site remediation activities were conducted in a manner
to prevent any significant cross-media transfer of pollutants during site preparation
and installation of containment structures at the site. The containment structures were
also designed to minimize the possibility of improper operation during the future
development and use of site for recreational or commercial purposes. A list of 11 BMPs
used at the site to address cross-media transfer of pollutants is given below.
Site Preparation and Staging
a. Perimeter and personnel monitoring of air quality.
Pre-Treatment
b. Monitoring trends in air quality and weather conditions to control
construction activities on site.
c. Covering debris generated during construction.
d. Providing temporary sumps for collecting stormwater run-off from the site
during construction.
e. Preventing surface water pollution during construction of the slurry wall.
f Providing temporary arrangements for trucks crossing over the slurry walls
during the remaining construction.
Soil Treatment
g. Checking the integrity of slurry wall.
h. Providing standby well-heads for additional future groundwater extraction
on site.
i. Providing a capillary break layer in multi-media cap.
j. Preparing multi-media cap for future site development.
Post-Treatment
k. Environmental monitoring plan for checking effectiveness of site
containment.
Additional details on the field application of each of these BMPs are given below.
a. Perimeter and Personnel Monitoring of Air Quality. Before implementing the
CMIPP, the existing buildings, equipment and structures at the facility were dismantled
under a plan approved by the MDE and incorporated into the Consent Decree. This plan
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required the perimeter monitoring of air quality for possible release of chromium and
asbestos during dismantling operations. The facility installed six air sampling
stations in the perimeter of the site which operated continuously for 24 hours to filter
the ambient air and provide samples for analysis of the concentrations of chromium and
asbestos. The air quality was then compared with the standards for average and maximum
concentrations of each pollutant. The concentration of a pollutant as measured by any of
the six air sampling stations was also normally expected to be within twice the standard
deviation of the recent values as measured by all six stations. Otherwise, it was assumed
that an exceedance of air quality had occurred and that a corrective action was required.
In addition to monitoring air quality in the perimeter of the site, the site used
personnel monitoring for chromium and asbestos to assure the health and safety of
personnel working on site during the dismantling and disposal of the plant.
b. Monitoring Trends in Air Quality and Weather Conditions to Control
Construction Activities on Site. The site monitors any trends in the concentration of
chromium in ambient air on a daily basis. These trends are examined rather than waiting
for an exceedance of air quality standards taking place on site. These trends are
discussed at daily meetings and a possible list of reasons is prepared for any trends
observed. These trends are also compared with the related set of weather conditions as
measured by a weather station installed on site (e.g., wind speed and direction are
compared with trends in the concentration of chromium). In a specific case of air quality
monitoring at this site, it was found that high concentrations of chromium were probably
related to a spell of dry and windy weather. In response, new efforts were made to
suppress dust emission by spraying water on the stockpiles and other areas of
construction on site. Work has also been stopped on several occasions when air quality
standards were exceeded.
c. Covering Debris Generated During Construction. A site visit during the
regrading of the site prior to the placement of a multi-media cap showed that the piles of
debris generated during previous construction activities were kept covered under sheets
of plastic. This practice was followed in the site mainly due to concerns of wind carrying
over any dust or other debris from open piles to the harbor nearby which is commonly used
for recreation.
d. Providing Temporary Sumps for Collecting Stormwater Run-Off From the Site
During Construction. During the same visit, it was found that temporary sumps were
provided with a pumping system to collect and transfer any run-off from the site to the
tanks being used for storing groundwater extracted on-site. This arrangement prevented a
transfer of site pollutants to the surface water during construction. After construction
of the cap, a permanent system will be made available for diverting stormwater run-on to
the site and collecting stormwater run-off from the site.
e. Preventing Surface Water Pollution During Construction of the Slurry Wall. In
addition to the detailed specifications and inspections required to assure a high quality
construction of the slurry wall and trench at this site, a few precautions were taken to
prevent cross-media transfer of pollutants during construction. For example, the trench
construction spoils were placed at levels above the 100-year level of high tide, and were
also covered by a sheet of plastic. These spoils were tested for the presence of high
concentrations of chromium and were provided with an appropriate management of
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stormwater run-on/run-off. Fugitive dust emission from the spoils was controlled during
periods of dry weather by sprinkling water over the spoils.
f. Providing Temporary Arrangements for Trucks Crossing Over the Slurry Walls
During the Remaining Construction. During construction of the multi-media cap over the
site, a short bridge of concrete is provided over the slurry wall at several points to
permit the occasional travel of trucks. This arrangement prevents damage to the slurry
wall affecting its containment performance.
g. Checking the Integrity of Slurry Wall. The containment performance of the
slurry wall was assessed after its construction (but prior to final remedial construction
on site) using a series of hydraulic tests and monitoring. For the purpose of testing,
paired piezometers were designed to the same specification as the final groundwater
extraction wells. Water levels in the shallow aquifer outside the slurry wall rose at an
average rate of 0.35 foot of head per month during and immediately after slurry wall
construction. Individual pumping tests were performed in the deep aquifer and at four
locations inside the site perimeter. In these locations, even with 25 feet of drawdown,
the outside piezometers did not indicate the influence from the pumping well. Thus,
barrier integrity in the vicinity of the pumping and monitoring was confirmed. Several
interior piezometers were then pumped simultaneously to simulate the groundwater
withdrawal after remedial construction on site. Tests confirming earlier pumping test
results showed rapid drawdown propagation in the confined aquifer within the slurry wall.
As a visual indicator of any settlement of slurry wall contents occurring after
construction, a steel plate was embedded in the slurry wall at several locations and used
as a level gage for direct measurement of subsidence.
h. Providing Standby Weil-Heads for Additional Future Groundwater Extraction on
Site. In anticipation of future problems in operating the groundwater pumping system at
the locations specified now, the site had provided standby well-heads (without pumps)
which could be used as a contingency. This feature minimizes the need to damage the multi-
media cap and drill new wells for an upgrade of the groundwater extraction system after
site development.
i. Providing a Capillary Break Layer in Multi-Media Cap. The site uses a capillary
break layer to prevent any capillary rise of contaminated water from the site to the low-
permeability layer (containing geosynthetic clay liner and geomembrane) above. Upward
migration of contaminants is thus prevented.
j. Preparing Multi-Media Cap for Future Site Development. As the site is
permitted for development as a multi-use zone, concept designs were prepared for the cap
in areas to be paved or unpaved in future. A multi-media cap with grass surface cover, for
example, will have a brightly colored (orange) geotextile placed 18 inches beneath the
surface to alert future developers of the site that a penetration of the cap below this
point might result in infiltration of water to contaminated soils below the cap.
k. Environmental Monitoring Plan for Checking Effectiveness of Site Containment.
Monitoring of chromium in surface water and groundwater levels both inside and outside
the slurry wall will be continued on a regular basis after completing the installation of
multi-media cap and groundwater drainage wells. It is expected that the standards of 50
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ppb for chromium in surface water and the maintenance of required gradient in ground water
will be achieved in future by pumping and treating groundwater at the rate of only about
2,000 gallons per day (gpd). In contrast with this rate of groundwater withdrawal, the
temporary arrangements on site now are pumping about 60,000 gpd.
11.7.3 Views and Discussion
While preparing this site for containment, it was necessary to take up other large
tasks which were, by themselves, major remedial actions and included the use of
additional BMPs to prevent cross-media transfer of pollutants. These tasks included:
(i) dredging of contaminated sediments from the harbor and replacing the dredged
sediments with clean stone for stabilizing the existing bulkheads around the site; and
(ii) dismantling the old chromium plant under negative pressure to prevent the emission
of chromium and asbestos into the neighboring areas as fugitive dust.
Because of the contaminant levels encountered, the dredging and disposal of the
sediments were accomplished under stringent environmental controls. To ensure that
sediments with excessive heavy metal concentrations were not taken to the disposal
facility off-site, testing and bulking of every load of dredged spoils was required.
Dredging was also performed completely within a turbidity curtain. Water sampling and
analysis for chromium was conducted inside and outside the curtain to check the curtain's
effectiveness in reducing migration of chromium in the surrounding harbor waters. In one
area of the site where confined space would have made dredging very problematic, the
sediments were stabilized and capped in place subsequent to construction of the rock
embankment at this location.
Prior to constructing the slurry wall, a new rock embankment was constructed to
prevent any unexpected collapse of contaminated soils into the harbor during
construction of a trench for the slurry wall. This embankment was located outside the
existing bulkheads along the boundary of the site with the marine harbor. The new
outboard embankment also enabled containment of the contaminated surfaces of the
bulkheads within the slurry wall.
The dismantling of the plant was conducted with a series of controls designed to
assure worker health and safety during these operations. The buildings at the site were
categorized according to pollutant concerns (i.e., only asbestos, asbestos and chromium,
and only chromium) and the dismantling plan required development and fabrication of
enclosures for creating a negative pressure during the dismantlement of some buildings.
One of the buildings, for example, used nine HEPA filters with a capacity of 18,000 cfrn
each, as well as the use of water curtains and air seals during dismantling operations.
This plant building was 300 feet long and 70 feet wide with a maximum height of the roof of
100 feet. There was another large building with similar dimensions and several smaller
buildings that were dismantled under negative air pressure.
11.8 Ex Situ Bioremediation of Explosives Contaminated Soils at a DoD Facility in
Virginia (Site 8)
11.8.1 Description of Site Remediation Activities
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In 1996, a Superfund Removal Action involving the excavation and transportation of
800 cubic yards of explosives-contaminated soil was completed within three days at one of
several sites within a DoD facility being investigated under an Installation Restoration
Program (IRP). At this site, the contaminated soils were found in a drainage area located
near wetlands and along a small tributary within the Chesapeake Bay watershed. The site
had received nitramine-containing wastewater from a weapons manufacturing plant since
1945. Although this effluent was diverted in 1986 to a sanitary sewer and the site had
reverted to a natural drainage area, explosive compounds such as TNT, HMX and RDX were
found at elevated concentrations in the samples of soil and sediments obtained recently
from the area. A decision was made to excavate soils up to 4 feet depth from the drainage
area which was partly subject to tidal action every day. Parts of the drainage area was on
a wooded slope of about 15 degrees leading to the wetlands.
After clearing the wood and preparing the site for excavation, two excavators were
operated round-the-clock to remove and load contaminated soil to dump trucks parked on
the road, about 20 feet above the bottom of the drainage area. The excavated soil was
transported over a distance of less than 1 mile to another location where a suitable
biocell had been constructed earlier to conduct a pilot study of an anaerobic process for
treating explosives in the soil. Approximately 600 cubic yards of the explosives-
contaminated soil was screened and then slurried before it was pumped into the biocell for
treatment. Proper operating conditions were maintained in this biocell and the treatment
goals for removal of explosive compounds from the soil and supernatant were achieved, as
planned, in nearly 60 days of bioremediation. The treated biocell contents will be left
in place and the cell will be closed with topsoil and vegetation after allowing excess
water to evaporate. Approximately 200 cubic yards of untreated soil removed from the
contaminated site and over 1,000 cubic yards of soil excavated to construct the biocell
remain for disposal in the pilot study area.
As the results of the pilot study were positive and treatment goals seem to have
been achieved, scaled-up operations using the anaerobic bioremediation process may be
applied to treat explosives contaminated soils found at other sites within the facility.
11.8.2 BMPs Used to Prevent Cross-Media Transfer of Pollutants
The pilot study of soil bioremediation and removal action completed recently at
this site used BMPs to prevent a few concerns for cross-media transfer of pollutants, like
surface water pollution due to stormwater run-off/run-on. However, there are other
concerns which would have to be addressed by BMPs in full-scale operations at this site. A
list of five BMPs used at this site to prevent cross-media transfer of contaminants is
given below:
Pre-Treatment
a. Arranging for containment of soils during excavation.
b. Controlling the transportation of excavated soils.
c. Providing for stormwater run-on/run-off controls near biocell.
d. Using soil erosion and sedimentation controls near biocell.
e. Containing spills during pre-treatment operations.
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Additional details on the field application of each of these BMPs are given below.
a. Arranging for Containment of Soils During Excavation. During site
preparation, a silt fence and straw bales were installed downslope of the excavated area
along the border of the site with the wetlands nearby. These soil erosion and
sedimentation controls prevented, to some extent, the carry-over of contaminated soils
and sediments by daily tidal action on the site. The rapid completion of soil removal
within three days also contributed towards a better containment of pollutants at the
site.
b. Controlling the Transportation of Excavated Soils. The dump trucks used for
transporting excavated soil from the site being remediated to the biocell were loaded by
excavators outside the site. A fixed route was always used for transportation to limit
the areas outside the site from being contaminated by spills on the road. Roll-off
containers were used instead of dump trucks to transport wet soils excavated from the
site.
c. Providing for Stormwater Run-On/Run-Off Control Near Biocell. The biocell
area was on a plateau and existing run-on was diverted around the area via a drainage swale
and an existing culvert. In addition, the biocell was given adequate (18 to 24 inches)
freeboard to accept direct precipitation and any stormwater run-on during normal
operations. At the same time, two portable tanks were kept ready on site to pump out
additional water draining into the biocell during storms.
d. Using Soil Erosion and Sedimentation Controls Near Biocell. Stormwater runoff
from the biocell was designed to pass through soil erosion and sedimentation controls. A
silt fence and strawbale checkdams were therefore installed on the downslope of the area
used for the biocell. These controls were placed before starting the construction of the
biocell. The area was then graded to ensure that all stormwater runoff passes through the
controls, which will remain until the site is vegetated after completing all operations.
Any vehicular traffic in the site is now limited to the haul roads leading to the biocell.
e. Containing Spills During Pre-Treatment Operations. Any leaks or spills of
contaminated water during the screening and slurrying of contaminated soils was
automatically drained by gradient into the biocell. This prevented the contamination of
soils outside the biocell.
11.8.3 Views and Discussion
A full-scale site remediation based on this pilot study should consider the use of
additional BMPs during site preparation and staging, pre-treatment and soil treatment.
The site had already planned a facility-wide groundwater monitoring and treatment in lieu
of the post-treatment phase of all site cleanup efforts. Additional BMPs that could be
used in full-scale operations include the following:
• / An assessment of the potential impact on the ecology of neighboring areas
should be performed before conducting excavation for ex situ remediation of
other contaminated sites that are located near wetlands. The feasibility
of in situ bioremediation should be considered as an alternative to prevent
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cross-media transfer of pollutants during excavation and transportation,
as well as the potential for contaminating the new site selected for
operating the biocell.
• / The site should be well-protected from flooding during storms.
• / A storage area (with liners, berms and top cover) should be provided for
excavated soils to prevent leaching of contaminants from the soils awaiting
treatment.
• / Future efforts using ex situ bioremediation should provide excess capacity
for treatment to prevent stockpiling of untreated soil on site at the end of
operations. Marshy conditions usually make it necessary to excavate more
quantities of soil than planned and the excavated soil may contain large
quantities of fine tree roots which cannot be removed easily from soil
before treatment.
• / Surface water run-off should be monitored during excavation in marshy land
subject to daily tidal action.
• / The air emission of organics (e.g., methane) should be monitored during
treatment in the biocell. A log should be maintained to record air
monitoring data with details of wind direction on a daily basis during full-
scale operations.
• / The use of a dragline instead of excavators should be considered as an
alternative equipment in marshy lands to avoid the problems of getting
stuck in marshy areas (as experienced at this site).
• / Biocells used in large operations should be equipped with concrete floors
with protective lining systems, such as studded liners, instead of the
flexible double liners separated by sand as used in the pilot.
• / The pipes used for recirculating process water in the biocell should be run
within the unit to prevent contamination of outside soil from leaks in these
pipes.
11.9 Comparison of Selected Case Study BMPs With BMPs Recommended in this Guidance
EPA found that some BMPs were used to address concerns of cross-media transfer in
different remedial phases. In a few case studies, EPA found that additional BMPs could
have been used; these additional BMPs have been identified under views and discussion
pertaining to each specific case study in this chapter.
The case studies performed by EPA also indicated that most BMPs are introduced in
the earlier two phases of site remediation, or during site preparation/staging and
pretreatment of soil. The most common type of activity describing a BMP used in the first
phase of site preparation/staging appears to be the installation of a suitable
environmental monitoring system before the commencement of any remediation work at the
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site. In most cases, this type of BMP may only involve the installation of an air quality
monitoring station at the perimeter of the site to address concerns of air pollution in
the neighboring community due to site remediation in future. In some cases, however, the
perimeter air quality monitoring may be supplemented by area and/or personal monitoring
at the location of soil excavation and treatment. Air quality monitoring may also be
supported by a monitoring of changes in weather conditions, as shown by one of the cases
studied by EPA. At this same site, EPA found that both surface water quality and air
quality were being monitored due to the concerns of transfer of pollutants in both media
during site preparation and pretreatment of soil.
In addition to the use of environmental monitoring as a BMP, EPA found that site
preparation often included the construction of new facilities like soil treatment pads
(or improvement of existing facilities) that have proved to be effective BMPs. At least
two sites were found to have used additional site characterization as a BMP during site
preparation/staging. For example, Site No. 1 (Army Ammunition Plant, Minnesota)
delineated the actual limits of soil contaminated with lead and other metals before
starting any excavation at the site. At the same site, more additional studies were
conducted to identify and characterize miscellaneous disposal areas existing at the site
to enable a segregation of the materials found in these areas from the metals contaminated
soil. This in-depth characterization of the site reduced the quantity of soil requiring
treatment and possibly improved the performance of soil treatment as well. This site also
found the establishment of an exclusion zone and decontamination pad for all traffic
to/from the site to be effective measures in preventing the cross-media transfer of
pollutants during soil excavation.
EPA found that the field use of BMPs is also widely introduced during the pre-
treatment phase of site remediation. Most sites were found to have arranged for dust
suppression and stormwater run-on/run-off control during site remediation. Different
methods of suppressing dust are used during soil excavation and transportation, storage
of excavated soil and treated soil in stockpiles, and soil treatment. At some sites
groundwater protection measures (e.g., providing lined and cover roll-offs for soil
treatment residuals) were also introduced as BMPs to prevent cross-media transfer in the
pre-treatment phase of site remediation. BMPs in the pretreatment phase of site
remediation also included the use of special measures, like selecting the right equipment
for excavating soils and providing temporary arrangements for trucks to move in the site
during construction, to prevent the generation of additional wastes or other transfer of
pollutants.
The case studies performed by EPA did not identify as many BMPs as originally
expected during the treatment phase of site remediation. This observation may be due to
the fact that records used in the case studies focussed more on the site specific details
(in contrast with design features of the technologies selected for soil treatment at the
sites). Most of the BMPs used during soil treatment, as identified by the case studies,
were related with proper management of wastewater and other process intermediates. Site
No. 7 (Chromium Manufacturing Plant, Maryland), however, made at lease three (3)
important changes in its technology for soil containment: (i) providing a capillary
break layer in the multi-media cap; (ii) preparing multi-media cap for future development
of the site as a commercial and recreational area; and (iii) providing standby well-heads
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for additional future ground-water extraction at the site. This site also conducted a
series of tests to check the integrity of slurry wall after construction.
The BMPs identified by the case studies included a few that were introduced in the
post-treatment/residuals management phase of site remediation. Most of these BMPs
involved proper disposal of treatment residuals, including the sorting, decontamination
and pretreatment of residuals to enable off-site disposal of residuals as non-hazardous
waste. A proper restoration of the site was also used in some cases as a BMP.
Environmental monitoring, especially the monitoring of groundwater, after completing
soil treatment at the site was also considered to be a BMP.
Table 11-2 provides examples of field/case study findings and relevant
modifications to the BMP guidance document. As indicated in this table, findings from the
case studies were sometimes used to add new BMPs to previous chapters of this guidance
document.
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Table 11-2. Examples of Field/Case Study Findings and Relevant Modifications of the BMP Guidance Document
Field/Case Study Observations
Soil Washing (Site 1): Delineating the actual limits
of soil contamination (See Section 11. 1.2. a); and
Conducting an in-depth characterization of new
disposal areas located on site (See Section 11.1.2d)
Soil Washing (Site 1): Building an earthen berm for
controlling surface water run-on to and run-off from
the site (See Section 11.1.2g)
In Situ Stabilization (Site 2): Conducting additional
soil tests to determine the effectiveness of soil
stabilization (See Section 11.2.2d)
Ex Situ Stabilization (Site 3): Modifying the process
for treatment of soil from different areas of the site
(See Section 11.3.2e)
Soil Washing (Site 4): Monitoring of air qualitv
during operations at AECs and the CAMU pad (See
Section 11.4.2a)
SVE (Site 5): Containerization of drill cuttings (See
Section 11.5.2a)
Thermal Treatment (Site 6): Arranging for use of
special dust suppressants on treated soil stockpiles
(See Section 11.6.21)
Containment (Site 7): Monitoring trends in air
quality and weather conditions to control
construction activities on site (See Section 1 1.7.2b)
Containment (Site 71: Providing a capillary break
layer in multi-media cap (See Section 11.7.2i)
Bioremediation (Site 81: Problems due to lack of
adequate treatment capacity (See Section 11.8.3)
BMPs or Other Reference in Guidance Document
There is a risk of inaccurate characterization with
any soil treatment technology (Chapter 2); and
Accurate characterization (e.g., ...quantities of
soil..) is important for the efficient use of [soil
washing! technology (Chapter 5)
Any off-site runoff should generally be prevented from
...mixing with site contaminated media by building
earthen berms (Chapter 5)
Treated wastes should be checked for leachability
prior to disposal (on site) (Chapter 2)
Wastes should be homogenized as much as practical
before processing (ex situ) (Section 10.4)
... organic or inorganic (air) emissions should be
monitored and appropriate emission control measures
should be used ... (Chapter 5)
...waste resulting from excavation and installation
of wells should be properly treated on site or trucked
away for disposal (Chapter 2)
Fugitive dust emissions should be controlled during
excavation by spraying water to keep the ground moist
Real-time weather data could be used to monitor
weather conditions and accordingly control treatment
operations (Chapter 2)
Geomembranes and drainage layers in multi-media caps
should be protected from capillary rising of
contaminants from the waste materials being contained
(Chapter 4)
Biotreatment systems should be designed to meet
unexpected changes in soil characteristics and/or
quantities (Chapter 8)
Comments/Modifications of the BMP Document
Guidance Document recognized the concern of
cross-media transfer, but BMPs should be
developed to match site-specific conditions
Case Study provides typical dimensions of an
earthen berm
Guidance Document revised (Chapter 2) to include
new BMP with a reference to in situ soil treatment
technologies
Guidance Document revised (Chapter 10) to modify
recommended BMP with a reference to ex situ S/S
technologies
Guidance Document was confirmed by the field
application of air monitoring and emission
control systems; use of hood or cover to capture
air emissions is not always needed
Guidance Document was confirmed by the field
practice of containerizing drill cuttings during
remedial activities
Guidance Document revised (Chapter 2) to include
the use of special dust suppressants (e.g.,
fibrous slurry or pine sap)
Guidance Document was confirmed by field practice
of using weather monitoring station; recommended
BMP was modified to include a reference to
"trends" in air quality and weather conditions
(Chapter 1)
Guidance Document was revised (Chapter 4) to
reflect the field practice observed in this case
study
Guidance Document was revised (Chapters 2 and 8)
to address the problem identified in the field
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